The Kynix Blog - Power

Overview: This article proposes a wind-solar hybrid power system that combines solar and a wind turbine power dispatching system that uses a battery and supercapacitor hybrid energy storage subsystem in the process of cost minimization.The proposed wind solar hybrid power system (WSHPS) architecture, which combines a wind energy system (WES) and a photovoltaic energy system (PVES), is shown in Fig. 1.Architecture of Wind Solar Hybrid Power SystemThe PVES has a 1 MW PV array, a maximum power point tracking (MPPT) controller, and a unidirectional DC/DC boost converter. An AC/DC rectifier, a pitch angle controller, and a 1.5 MW direct-drive three-phase permanent magnet synchronous generator (PMSG) linked to a wind turbine make up the WES.Fig. 1. A wind-solar hybrid power system with HESS Source: IEEE AccessPhotovoltaic Energy SystemThe output of the PV array is very sensitive to two environmental factors: PV irradiation and PV cell temperature. MPPT with incremental conductance (IC) controls the duty ratio of the unidirectional boost converter to draw the maximum amount of power from the PV array. In contrast to the more traditional methods used to extract maximum power from PV systems, an IC MPPT is easy to implement and very effective. As a result, IC MPPT has seen widespread application despite the fact that it can cause slight fluctuations in the maximum power point. One nonlinear device that can be modeled as a current source is a photovoltaic cell. The PV output power and capacity factor are both negatively affected when the PV cell temperature is higher than the ambient temperature.Wind Energy SystemThe WES consists of a wind turbine (WT), permanent magnet synchronous generator (PMSG), pitch angle control, drivetrain, and power converter. Without a gearbox, the WES-based PMSG can connect to the WT. PMSG, based on WES, utilizes a two-step process for energy conversion. The WT blades first convert the kinetic energy into mechanical energy. The second step is for the shaft to transmit the mechanical energy to the PMSG, which then uses the energy to generate electricity.LCL FilterTo satisfy smart grid regulations, an inverter's interaction with the grid additionally necessitates a small output harmonic filter. Because of its superior efficiency and ability to dampen harmonics, an LCL filter has been developed.Calculating the Dispatched PowerFurthermore, the WT's output is proportional to the wind speed passing through the rotor. The real solar irradiance, temperature, and wind speed data recorded at NREL to forecast the dispatched power hour by hour for a full day is expressed as PGrid,ref. Therefore, the WSHPS and HESS will continue to contribute the required amount of power to the utility grid throughout each hourly dispatching period. The WSHPS relies on both the PV array and the WT system to generate an average output power throughout each dispatching period.Dispatchable Power from Photovoltaic Energy SystemThe average output power of the PV array is calculated for each dispatching period using the average irradiance and temperature from the NREL solar statistics inputs. Input factors, including solar cell type, number of parallel cells, and number of series cells, as well as environmental circumstances, are used by the PV array module in Matlab/Simulink to generate power-voltage characteristic curves. NREL's solar data has a resolution of one sample per minute. To generate solar data with a resolution of 120 samples/minute, the cubic spline interpolation method is used. After that, the mean operation method is used to get the average irradiance and temperature for each dispatching time. PPVES,est is the estimated power of the PVES derived from the average irradiation, whereas ηPVES,est is the estimated efficiency of the PVES derived from the average temperature. The ultimate estimated power dispatchable by PVES (PPVES) can be written as follows: PPVES = PPVES,est * ηPVES,est    (1)Dispatchable Power from Wind Energy SystemSimilarly, the estimated WES dispatchable power (PWES) is determined. Based on user input parameters such as base wind speed, base rotational speed, blade pitch angle, and maximum power at base wind speed, the WT model in MATLAB/Simulink gives the WT power characteristic curve. Then, the average wind speed is obtained using the mean operation and cubic spline interpolation methods. The PWES is an estimated power output based on the average wind speed. Finally, Equation (2) is used to determine the typical power output of the wind solar hybrid power system, which is expressed as PWSHPS. PWSHPS = PPVES + PWES    (2)Hybrid Energy Storage SystemEach ESS is connected to a bidirectional DC/DC converter, and the HESS is paired in parallel with the WSHPS. Parallel connections between the WSHPS and HESS and the DC-link capacitor bank that functions as the DC bus lead to a three-level T-type inverter that provides clean, stable DC power. By regulating the current through the power converters, it is possible to regulate the output power from the WSHPS and HESS in this architecture. Because of its great efficiency, low total harmonic distortion (THD), and lower common-mode voltage, a three-level T-type inverter is used. Controlling the system power that is fed into the utility grid is the responsibility of the HESS. Calculating the HESS reference power (PHESS,ref) is as simple as subtracting the PGrid,ref from the PWSHPS: PHESS,ref =  PGrid,ref - PWSHPS   (3) Rapidly fluctuating power components can severely shorten a battery's service life. To assign high-frequency power reference components for the supercapacitor energy storage system SESS (PSESS,ref) and low-frequency power reference components for the battery energy storage system BESS (PBESS,ref), the PHESS,ref is supplied through the LPF. In addition, when the ideal value of depth of discharge (DOD) is determined, a rule-based state of charge (SOC) control algorithm is used to keep the BESS SOC within the optimal range (DOD optimum). As with the SESS, after the best value of DOD has been determined, a rule-based SOC control algorithm is put into place to govern the SESS SOC.HESS DOD OptimisationThe DOD and the rate of change of the charging-discharging power are the two most important factors in determining the ESS's useful life. There is an almost exponential link between cycle life and DOD consumption. There are two primary determinants of ESS costs: (i) the ESS's expected service life and (ii) the ESS's minimum capacity. The minimal capacity of the BESS increases as the DOD decreases in use. However, the BESS's service life decreases with increasing discharge depth. Thus, the simulations are run with all possible values of the BESS DOD to find the optimal value of DOD that results in the cheapest BESS for dispatching the WSHPS electricity. Similarly, research into the ideal DOD for the SESS has been conducted. Unlike Li-ion batteries, supercapacitors can be charged and drained indefinitely. Therefore, the total number of charging-discharging cycles for the SESS is taken to be constant.HESS Cost MinimizationThe BESS and SESS use the LPF as their power reference. Minimum SESS capacity is proportional to the LPF time constant, while minimum BESS capacity is inversely related to the LPF time constant. The total cost of the HESS can be reduced by selecting an appropriate value for the filter time constant. The PSO strategy is used to determine the optimal LPF time constant once the suitable cost formula of the HESS as a function of the LPF time constant has been acquired via the curve fitting method. Because of its many benefits, including easy implementation, increased credibility in locating global optimums, the need for the adjustment of only a small number of parameters, and rapid convergence, the PSO method is used. Although genetic algorithms are also commonly used as an optimization approach in renewable energy systems, the PSO typically provides faster evaluation times and higher-quality solutions.Estimation BESS and SESS LifespanThe charging-discharging characteristics of the BESS over a period of time are utilized to evaluate its service life due to the fluctuating nature of the WSHPS output power. Because of calendar aging, the BESS's predicted lifetime decreases. Calendar aging and cycling are both taken into account by the SESS aging model.Estimating the Cost of HESSThe ESS cost is examined while taking into account the costs associated with both cycle and calendar aging. The capital cost, power conversion system cost, and operation and maintenance (O&M) cost of the ESS make up its total expense. Thus, it is possible to estimate the overall cost related to the BESS (CBat,overall) using equation (4): CBat,overall = CCap + Cconv + CO&M     (4)Summarizing the Key PointsThe article proposes a wind-solar hybrid power system that combines solar and wind turbine power dispatching systems.The system uses a battery and supercapacitor hybrid energy storage subsystem to minimize costs.The wind energy system consists of a wind turbine, permanent magnet synchronous generator, pitch angle control, drivetrain, and power converter.The photovoltaic energy system has a 1 MW PV array, a maximum power point tracking controller, and a unidirectional DC/DC boost converter.The article aims to optimize energy storage and power dispatching in wind-solar hybrid systems for cost-effective and reliable electricity supply.ReferenceRoy, Pranoy, Jiangbiao He, and Yuan Liao. “Cost Minimization of Battery-Supercapacitor Hybrid Energy Storage for Hourly Dispatching Wind-Solar Hybrid Power System.” IEEE Access 8 (2020): 210099–115. https://doi.org/10.1109/access.2020.3037149.

Overview: This article discusses the output capacitance losses and dynamic threshold voltage in Gallium nitride devices. The output capacitance losses are a significant percentage of the device's total loss. The dynamic threshold voltage is a very important factor in power applications. In the area of technological advancements, Gallium nitride (GaN) devices have emerged as a promising solution for various applications. However, despite their growing deployment, there remain persistent uncertainties surrounding their stability, reliability, and robustness. In both academia and industry, there is a growing focus on addressing the challenges related to the stability, reliability, and robustness of GaN devices. Gallium nitride high-electron mobility transistors (GaN HEMTs) have stability issues like dynamic on-resistance, dynamic threshold voltage, and output capacitance losses. All of these things are very important in power applications, especially at high frequencies. This article provides a detailed discussion on output capacitance losses and dynamic threshold voltageWhen using gallium nitride, how does output capacitance loss impact stability?GaN HEMTs are responsible for the output capacitance losses. When the off-state power device's equivalent output capacitance is charged and discharged, this loss occurs. In an ideal capacitor, this loss would be zero. Large-signal, dynamic double sweep in GaN HEMTs leads to power loss because of hysteresis in the relationship between the output charge and the drain-to-source bias. This loss problem has just been brought to light in GaN HEMTs; however, it was first noticed in Si superjunction devices. GaN HEMTs are experiencing significant output capacitance losses. In high-frequency soft-switching applications, this loss starts to become a significant percentage of the device's total loss from the perspective of the system. This loss is often significantly smaller than the other device losses in hard switching (HSW) or low-frequency applications. Unexpected increases in junction temperature can severely degrade system performance.Methods to Determine Output Capacitance LossThis loss has been quantified using a variety of approaches, including calorimetric (thermal) and electric (Sawyer-Tower, nonlinear resonance, and unclamped inductive switching), as shown in Fig. 1. There are benefits and drawbacks to each of these approaches. Fig. 1. Output Capacitance Loss Determining MethodThermal MethodCalorimetric MethodOne of these methods is the calorimetric method, which involves connecting the device under test (DUT) in parallel with an active switch, leaving the DUT unpowered while the active switch controls the drain-to-source bias, and figuring out the output capacitance loss from the change in junction temperature. This technique permits the measurement of the loss of the device under test in active soft-switched converters without regard to the operating frequency. However, system calibration in this approach may be time-consuming, and isolating device output capacitance loss from other losses may be difficult. At low power levels, the calorimetric measurement may also lose some of its precision.Electrical MethodElectrical technique implementation and related data processing are typically easier.Sawyer-Tower TechniqueTo generate the sinusoidal excitation, the Sawyer-Tower technique uses a network that includes the DUT, a reference capacitor, and a power amplifier. Since the DUT is always turned off, the input voltage and the capacitor voltage can be used to determine the DUT's large-signal charge-voltage waveforms; the output capacitance loss can then be extracted from the hysteresis of the waveforms.Nonlinear Resonance or Unclamped Inductive Switching TechniquesThe DUT can be switched on or off when using nonlinear resonance or unclamped inductive switching techniques.ChallangesWhile these electrical systems require a less complex setup, noise and variation in the waveforms and equipment used (such as narrow probe bandwidth, probe delays, and waveform distortion at high frequencies) may have an impact on their accuracy. Calorimetric and Sawyer-Tower methods only include the device in its off-state, so they can't be used to investigate how on-state current affects output capacitance loss. The output capacitance loss data from different approaches requires careful consideration of these factors. Finally, there is still a disagreement over where exactly the output capacitance loss in GaN HEMTs originates, despite widespread agreement that carrier trapping or de-trapping causes output capacitance hysteresis and is a major contributor. The relevant traps' physical origins, location, time constant, and energy level remain unknown. Output capacitance loss has been linked to both leakage current in the epitaxial structure and resonance on the Si substrate. There haven't been many reports on methods for minimizing output capacitance loss because its cause isn't fully understood. Redesigning the GaN HEMT architecture and epitaxial stack has been proven experimentally to decrease the output capacitance losses. Output capacitance loss has a major effect on the device selection for high- and very-high-frequency power converters from the perspective of the application. An established approach to characterization that takes into account both the on and off states of the device and faithfully depicts its steady-state switching in converters would greatly speed up this process.What causes threshold voltage in gallium nitride devices?The instability of the threshold voltage at high bias temperatures in Si and SiC MOSFETs has been a central topic of study for decades. GaN HEMTs of varying gate designs were also investigated. GaN metal-insulator-semiconductor (MIS) HEMTs were the primary focus of early research. In MIS-HEMTs, just like in Si and SiC MOSFETs, trapping at the insulator/GaN interface or in the bulk dielectric is what causes the unstable threshold voltage.Dynamic Threshold VoltageRecent years have seen a shift in research attention to commercial p-gate HEMTs as p-gate gradually becomes the prevailing E-mode GaN technology. Unlike the threshold voltage instability seen in MOSFETs and MIS-HEMTs, the dynamic threshold voltage in SP-HEMTs is an inherent characteristic of the floating p-GaN layer. Fig. 2 depicts the SP-HEMT gate stack, which comprises a back-to-back set of p-GaN Schottky junctions coupled with a p-Gan/AlGaN/GaN p-n junction. This "floating" p-GaN layer is the result of the fact that its charges cannot be successfully supplied or removed in fast switching since the bias state (forward or reverse) of these two junctions is opposite each other. Fig. 2. Typical trapping locations Source: IEEE Transactions on Power Electronics Positive dynamic threshold voltage shifts are common due to the charge storage process in p-GaN. The off-state blocking voltage and switching frequency both contribute to a larger threshold voltage shift. An Ohmic contact on p-GaN is a notable component of the hybrid-drain gate injection transistor since it facilitates efficient charge supply and extraction and, in turn, a reliable threshold voltage. Trapping may potentially play a role in the dynamic threshold voltage, in addition to the free-floating p-GaN. There are two trapping mechanisms that can affect a threshold voltage shift when operating under a forward gate-to-source bias. The first technique causes a negative threshold voltage shift by recoverable hole trapping. The second mechanism causes a positive threshold voltage shift because electrons are trapped and take time to recover. The dynamic threshold voltage shift may have a significant impact on switching processes in devices. Power loss in SP-HEMT grows as the reverse conduction voltage rises with a positive shift. The dynamic threshold voltage of SP-HEMTs will influence the majority of their turn-on losses. As a result, the gate's dependability is compromised, and a large gate-drive voltage is required to properly turn on the device. Therefore, the dynamic threshold voltage should be taken into account in circuit simulations to accurately portray real-world circuit properties. The switching transients in a phase-leg circuit have been recently analyzed using a SPICE model with a dynamic threshold voltage.What are the additional problems associated with composite devices?Given their multi-chip nature, composite devices may experience instability problems stemming from both the GaN HEMTs and the interconnections between the Si devices and the GaN HEMTs. For instance, there have been reports of instability in cascode GaN HEMTs. A diverging oscillation can arise due to a capacitance mismatch between the GaN and Si switches during high-current turn-off situations. Internal switching losses may also rise as a result of the bond wires' inductance between the switches and the Si avalanche. The current generation of commercial cascode GaN HEMTs does not have internal bond wires between the two chips. Instead, the Si chip is stacked directly on the source pad of the GaN HEMT, which reduces the connectivity-induced loss. False turn-on events, however, are possible, as are catastrophic failures brought on by SC oscillations. Cascode GaN HEMTs and direct-drive devices, on the other hand, rarely have gate instability because a Si MOSFET drives them largely or because extra protection circuits are copackaged with the GaN HEMT.Summarizing the Key PointsGallium nitride (GaN) devices are a promising solution for various applications. Despite their growing deployment, there remain uncertainties surrounding their stability, reliability, and robustness. GaN HEMTs have stability issues like dynamic on-resistance, dynamic threshold voltage, and output capacitance losses. Output capacitance losses are a significant percentage of the device's total loss. Dynamic threshold voltage is a very important factor in power applications, especially at high frequencies. Addressing the challenges related to the stability, reliability, and robustness of GaN devices is a growing focus in both academia and industry.ReferenceKozak, Joseph Peter, Ruizhe Zhang, Matthew Porter, Qihao Song, Jingcun Liu, Bixuan Wang, Rudy Wang, Wataru Saito, and Yuhao Zhang. “Stability, Reliability, and Robustness of GaN Power Devices: A Review.” IEEE Transactions on Power Electronics 38, no. 7 (July 2023): 8442–71. https://doi.org/10.1109/tpel.2023.3266365.

Power grids are becoming more decentralized as renewable energy sources take over as the dominant factor. These cutting-edge technological advancements, while providing opportunities for greater productivity.Why is a new reliability framework necessary?The new components of today's power systems bring up novel difficulties that necessitate a new reliability framework, which has recently been implemented. Assessing the reliability of modern power systems necessitates not only assessing various electro-magnetic and mechanical stability difficulties but also introducing new ideas related to local reliability.New Reliability ConceptA new methodology for reliability analysis in contemporary power systems should be established in order to address the issues brought on by new power system technology. It could keep the main ideas of adequacy and security while also taking into account the effects of grid modernization.Modern Power System Adequacy AssessmentThe cyber-physical structure of the current power system, which consists of three layers—power, communication, coupling, and decision—explains the adequate nature of this system. The proposed adequacy assessment framework is depicted in Fig. 1 in order to address all the drawbacks of reliability evaluation methodologies.Fig. 1. Framework for modern power system adequacy assessment. Source: IEEE Open Journal of Power Electronics As illustrated in Fig. 1, the suggested framework allows for the evaluation of the cyber-physical power system's suitability at three hierarchical levels: generation, generation-transmission, and distribution.GenerationFirst and foremost, sufficient generation system capacity is needed to meet system demand as a whole. As a result, the generating sufficiency in HL I can be assessed similarly to the sufficiency of the traditional power system, as illustrated in Fig. 2(a).Fig. 2. Conventional framework for adequacy assessment. Source: IEEE Open Journal of Power ElectronicsCyber-Physical Generation-Transmission SystemTo make sure that the cyber-physical generation-transmission system in HL II is good enough, the effects of the cyber-layers and the effects of distribution generation must be modeled. Large-scale generation units and distribution networks based on microgrids are shown in simplified form in Fig. 3(a). The microgrids are modeled as a specific node at a Point of Common Coupling (PCC), which is depicted in Fig. 3(b), in order to assess the adequacy of these systems. Fig. 3. Scalable framework for modern power system adequacy: a) main structure as a simplified grid; b) equivalent model of microgrids from distribution systems; c) local adequacy for each microgrid. Source: IEEE Open Journal of Power Electronics Depending on the topology and accompanying power management technique inside each microgrid, this special PCC node may be a load or a generation unit for each microgrid in a distribution network. For example, in the substation microgrid comprising medium-scale generators to provide its load, the equivalent load (which is equal to the generation minus the load) can be taken into account at the PCC in Fig. 3(b). Additionally, the equivalent generation can be assumed at the PCC in Fig. 3(b) if the substation microgrid's generation is greater than its load. The substation's internal generation unit availability, load power, and upstream switch reliability all have an impact on this equivalent generation unit's availability. The MV distribution networks can therefore be characterized for transmission system analysis as equivalent loads or generations. The cyber-physical availability model, as shown in Fig. 2(b), can therefore be used for modeling the reliability of the cyber-physical transmission system.Cyber-Physical Distribution SystemThe reliability of cyber-physical distribution networks can be modeled in HL III for each microgrid based on its structure in HL III-A and for the distribution network in HL III-B, as illustrated in Fig. 1. In distribution networks, there are four different types of microgrid structures: single-customer, partial feeder, full feeder, and substation microgrid. The single customer microgrid's adequacy can be modeled by simplifying its structure, as seen in Fig. 3(c). The distribution network outside of the single-customer microgrid is represented in this form as an equivalent generation unit. The local adequacy of the microgrid must be met depending on the application of the single-customer microgrid, such as household load, hospital load, etc. The partial or full feeder microgrid's adequacy can be evaluated similarly to the single-customer microgrid by treating the single-customer microgrids inside it as a specific equivalent node at PCC, which can be a load or generator. Additionally, by modeling the feeder microgrids as special nodes at PCC, the substation microgrid's adequacy is assessed. The distribution network adequacy assessment's primary focus is on the accessibility as well as the availability of energy sources in each sub-grid. This may necessitate restrictions across sub-grids, particularly for single customers who may wish to be islanded during grid outages in order to retain their adequate supply despite the upstream microgrid's declining adequacy. A distribution network consists of numerous substations, which are connected to the high-voltage grid and to one another by MVAC or MVDC transmission systems. Thus, by modeling each substation microgrid as a particular node at their PCC, be it a load or a generator, which is connected to the main grid, it is possible to assess the adequateness of the cyber-physical distribution systems. Due to the presence of DGs and DESS, distribution system reliability, unlike traditional power systems, necessitates local adequacy assessment. The suggested scalable reliability modeling for distribution networks' microgrids ensures each microgrid's adequate suitability.Modern Power System Security AssessmentIn addition to being adequate, modern power systems also need to be secure due to the various sources of uncertainty they include. Similar to conventional power systems, security can be characterized as a system's capacity to tolerate unforeseen events. As indicated in Fig. 4, the security of modern power systems can be examined in three domains: static, dynamic, and cyber. Fig. 4. Framework for security assessment in modern power systems. Source: IEEE Open Journal of Power ElectronicsStatic SecurityThe steady-state operation of the system following any unforeseen event is referred to as static security. The system frequency, bus voltages, and temperature limits of the equipment must therefore remain within a reasonable range. In contrast to traditional power systems, converters specifically for HV and MV transmission lines require appropriate analysis of their thermal limits due to their restricted overloading capacity. Therefore, corrective measures must be taken to maintain system security because any contingency could lead to link overload. Additionally, after any contingency that results in the islanding of the microgrids, the distribution networks must guarantee that the power quality standards are met in addition to the voltage limitations. This is because the power quality requirements for various applications cannot be the same. Therefore, after islanding the microgrids, active and passive filters must be properly relocated in distribution networks to fulfill static security.Dynamic SecurityIn addition, the power system needs to be dynamically secure in case of an emergency. Modern power systems heavily rely on fluctuating energy sources with low inertia; hence, dynamic security is crucial. It could cause problems with voltage and frequency stability in the power systems. Without the proper voltage regulators, intermittent output power or renewable resources may degrade the grid voltage, which may impact the stability of the voltage. Furthermore, the absence of inertia in more or full renewable energy supplies may have an impact on the stability of the grid's frequency. Intercommuting to nearby grids with HVDC systems and using energy storage systems are required to resolve the frequency stability difficulties in the grid. The overall system security can control the size and placement of renewable energy sources, as well as the connection points, capacity, and ancillary services of HVDC networks. Proper system design can guarantee the entire security of the power system. As a result, just like traditional power systems, power system security evaluation calls for an analysis of voltage, frequency, and angular stability. Additionally, due to the widespread use of power electronic converters, the EMM stability difficulties in modern power systems must be taken into account in security evaluation. Power systems and microgrids may experience serious stability problems as a result of EMM interactions. Due to the quick dynamics of converter control systems, the EMM stability assessment within contingency analysis may be a challenging and time-consuming operation. Therefore, adequate models and tools for EMM stability analysis for security evaluation in modern power systems should be established.Cyber SecurityModern power systems are vulnerable to cyber-security vulnerabilities in addition to static and dynamic security problems. Cyber problems may be connected to either the decision layer or the communication and coupling layer. The physical malfunction of monitoring and measurement devices, as well as the lack of data availability, can have an impact on the system's performance at the communication and coupling layers. Additionally, cyberattacks affecting sensors and shift measurements, as well as physical failure of decision equipment that results in false data being injected into communication links, can lead to poor decisions and malfunctions in power systems. The security of the power system must be ensured against physical failure, data loss, and cyberattacks. These issues could have a number of detrimental effects on the system, including angular and frequency stability due to poor decision-making and a change in the demand-generation balance, issues with islanding detection and grid separation, as well as effects from equipment overloading, all of which could jeopardize the security of the entire system. Therefore, in security evaluation and management, it is necessary to consider the cyber-security of modern power systems.Summarizing the Key PointsThe decentralization of power grids due to renewable energy sources requires a new approach to assessing their reliability. The cyber-physical structure of the current power system consists of three layers: power, communication and coupling, and decision. The main ideas of adequacy and security are taken into account in new reliability framework. The new framework can address all the drawbacks of reliability evaluation methodologies. The cyber-security of modern power systems is a crucial consideration in security evaluation and management.ReferencePeyghami, Saeed, Peter Palensky, and Frede Blaabjerg. “An Overview on the Reliability of Modern Power Electronic-Based Power Systems.” IEEE Open Journal of Power Electronics 1 (2020): 34–50 https://doi.org/10.1109/ojpel.2020.2973926.

Overview: The article discusses the rapid growth of renewable energy resources, particularly photovoltaic and wind turbines, as the most attractive power generation options due to strong government incentives and encouragement to use green energy. Over the past ten years, the use of renewable energy resources has grown rapidly throughout the world. Renewable energy sources, especially photovoltaic (PV) and wind turbines (WT), have emerged as the most attractive power generation options.Challenges in Renewable Energy Based Power SystemsThe installed wind turbine capacity increased from 540 GW to 591 GW between 2017 and 2018, while the installed solar photovoltaic capacity increased from 405 GW to 505 GW. The output of the photovoltaic and wind turbines exhibits unstable characteristics because it is heavily dependent on weather factors such as wind and cloud movement. The utility grid faces significant technical challenges with regard to power quality, generation dispatch control, and grid reliability as a result of the substantial penetration of these types of intermittent renewable energy sources. As a result, operators of renewable energy plants will face pressure to deliver consistent power, much like conventional fossil fuel power plants have done. Overgeneration and restrictions are the grid operators' growing concerns as more photovoltaic and wind turbines are connected to the grid. There are primarily two reasons for the curtailment of renewable energy, namely regional supply excess and regional transmission constraints. Although higher levels of curtailment have also been reported, the typical range of curtailment levels for wind generation is between 1% and 4%. When rigid traditional generators, like nuclear and coal plants, are unable to be used to generate lower power, negative pricing and the curtailment of renewable energy generation occur. The duck curve, which is depicted in Fig. 1, can be used to show the enormous difficulty of incorporating solar and wind energy as well as the likelihood of overgeneration and curtailment. Fig. 1. Duck curve illustration. Source: IEEE AccessThe Idea of Hybrid Power SystemsIt is generally accepted that any individual wind or solar source cannot sustainably power a load. It should also be noted that the hours of maximum output for wind and solar systems vary throughout the day and the year. The weather and climate patterns actually make solar and wind energy resources mutually beneficial. Thus, on a seasonal or daily basis, the energy produced by wind-photovoltaic resources keeps reversing. Since photovoltaic and wind turbines have benefits that complement one another in terms of power profiles, the hybrid utilization of the two should receive more attention. It is possible to develop hybridization techniques to deal with the intermittent nature of solar and wind power.Wind-Solar Hybrid Power SystemsThe wind-solar hybrid power system (WSHPS) combines photovoltaic and wind turbine subsystems to boost overall system efficiency, reduce energy storage capacity needs, and make the power grid more reliable. Wind-solar hybrid power systems are better than single photovoltaic or wind turbine systems in deficient utilities because they can compensate for unwanted intermittent variations with a single renewable energy source. In addition, the wind-solar hybrid power system can help the points of generation and consumption be adjacent to each other, which reduces infrastructure costs, particularly for rural electrification projects. As a result, wind-solar hybrid power system schemes at a single location are becoming a prominent trend in the worldwide transition to renewable energy. Voltage and frequency regulation, the mismatch between generated power and load demand, grid operation economics, and the scheduling of generation units are just some of the difficulties associated with the incorporation of large amounts of intermittent renewable energy into the utility. Therefore, grid operators must take extra measures to guarantee the reliability of the system. Because of the addition of solar and wind energy to the grids, fossil fuel generators, for example, need to be switched on and off or have their outputs adjusted more frequently to account for power fluctuations. In addition to raising maintenance costs, frequent cycling of fossil fuel generators also reduces efficiency. With high solar penetration, the cost of cycling ranges from $0.47/MWh to $1.28/MWh per fossil-fueled generator. Therefore, the aforementioned economic challenges necessitate a constant power dispatch commitment from the wind-solar hybrid power system framework at an acceptable interval.Energy Storage SystemsAdding the energy storage system (ESS) to the wind-solar hybrid power system framework will further mitigate the risks associated with renewable energy sources. In particular, the energy storage system makes it possible to provide supplementary services like voltage regulation, frequency regulation, harmonic reduction, transient stability, and load leveling. There are a variety of energy storage systems on the market, but two of the most popular are batteries and supercapacitors (SC). The characteristics of the battery and supercapacitors are compared in Table 1. There are many similarities between the supercapacitors and the conventional capacitors, with the main differences being the supercapacitors' smaller size and longer lifespan. Table 1: Battery and SC Performance Comparison Source : IEEE Access The battery energy storage system (BESS) has a low-power ramp rate, which indicates that the BESS charging-discharging rates are insufficient to meet peak or pulse load demand despite its high energy density property. The energy density is low, but the power ramp rate is high in the supercapacitor energy storage system (SESS). So, the supercapacitors can't keep up with the load for as long as it's needed. It's obvious that neither of these energy storage systems has both a high power density and a high energy density. Therefore, if only one kind of energy storage system is deployed to meet both the power and energy capacity specifications, a high installation cost may be needed to meet both the energy and power capacity needs.Hybrid Energy Storage SystemTherefore, a cost-effective energy storage system can be developed through the use of a hybrid energy storage system (HESS) consisting of a battery energy storage system and a supercapacitor energy storage system, with the supercapacitor facilitating the fast-changing power components passing through the battery, which increases the service life of the battery.Hybrid Energy Storage for Wind-Solar Hybrid Power SystemsThe main goal is to improve the way that renewable energy is used so that the wind-solar hybrid power system output power can be sent to the power grid every hour for a whole day, as desired. For this, the wind-solar hybrid power system architecture incorporates a hybrid energy storage system made up of lithium-ion batteries and supercapacitors, which can store the collected wind-solar hybrid power system energy and transform the intermittent energy into a reliable supply that can be dispatched when needed.Dispatching SchemeTo provide the wind-solar hybrid power system's output power to the utility grid, a dispatching scheme has been employed rather than the conventional peak shaving or smoothing approach. The wind-solar hybrid power system can be regulated like other conventional generators, such as thermal and hydropower plants, because of the utility's dispatching scheme. When combined with the dispatched scheme by which wind-solar hybrid power system output power is supplied to the grid, this flexibility extends to the utility grid in many ways, including the scheduling of generation units, the economics of grid operation, and the provision of grid ancillary services.Low Pass FilterA low pass filter (LPF) is used to split the energy produced by the hybrid energy storage system into two groups: the SC group receives power with a fast-dynamic response, while the battery group receives power with a slow-dynamic response. The battery's lifespan is increased by using this method because it helps the battery avoid rapid charging and discharging cycles and a large discharge current. In addition, the most cost-effective hybrid energy storage system for hourly dispatching of the wind-solar hybrid power system power scheme is sought by using curve fitting and Particle Swarm Optimization (PSO) techniques. The goal is to minimize the cost of the hybrid energy storage system while keeping the energy storage system's state-of-charge (SOC) within a certain range and meeting the power demand during each dispatching period.Summarizing the Key PointsRenewable energy resources, particularly solar and wind, have grown rapidly due to strong government incentives. The output of these energy sources exhibits unstable characteristics due to weather factors such as wind and cloud movement. Hybrid power systems that integrate wind and solar energy can maximize the potential of renewable energy. Technical challenges in photovoltaic and wind turbine power systems need to be addressed to overcome the unstable characteristics of renewable energy. The integration of energy storage systems can help mitigate the variability of renewable energy sources.ReferenceRoy, Pranoy, Jiangbiao He, and Yuan Liao. “Cost Minimization of Battery-Supercapacitor Hybrid Energy Storage for Hourly Dispatching Wind-Solar Hybrid Power System.” IEEE Access 8 (2020): 210099–115. https://doi.org/10.1109/access.2020.3037149.

Overview: This article explores the integration of smart grids, renewables, and communication technologies in the energy sector. It highlights the importance of energy storage systems, home energy management, and electric vehicles. The incorporation of a "smart grid" into today's electrical infrastructure is essential. Notable studies in the field of smart grids that relate to the Energy Internet can be broken down into the various subfields that will be covered below.Home Energy ManagementWith the aid of home energy management systems, the consumer can monitor the energy usage of each appliance in their home and make changes as necessary. The Energy Internet can be managed and operated by household energy cells through a home energy management system. Traditional energy infrastructure typically sends customers monthly bills detailing their energy consumption. The Energy Internet's home energy management systems offer a wealth of data, including consumption data, electricity generated locally via rooftop solar PV, current market rates, and storage capacity, all in real-time. Smart home energy management systems are built on a foundation of connected appliances, controls, networks, and displays. Home energy management systems provide feedback on energy use and other smart features. Consumers can make choices about their energy usage via in-home displays. For instance, Smarter Homes is a company that installs home energy management technologies to control solar rooftop PV, storage devices, and home appliances through the use of the internet of things and consumer electronic devices like iPads and Amazon Alexas. Energy management systems for the home make it easier to connect energy storage to the home's electrical network. An effective home energy management system is necessary for the envisioned energy internet to enable extensive energy trade.The Concept of Vehicle-to-Grid (V2G)Rechargeable batteries and an electric motor provide the power for plug-in electric vehicles. An energy port installed in a home or public space supplies power to a rechargeable battery. If electric vehicles are managed in a distributed fashion along with other electrical loads, they can play an important role in the demand-side management of the smart grid. When compared to stationary energy storage devices, electric vehicles have the distinct advantage of portability, as they can be driven from one location to another. Therefore, vehicle-to-grid and grid-to-vehicle initiatives can't be carried out without the widespread adoption of electric vehicles. Range anxiety is the key factor in determining how many people will sign up for vehicle-to-grid programs. Thus, even in developed nations, the rate of adoption of electric vehicles is low. But from the perspective of the power grid, vehicle-to-grid provides a variety of useful ancillary services, such as peak load management and voltage and frequency regulation. Even privately owned electric vehicles parked in a parking lot can contribute significantly to grid power during periods of inactivity with minimal disruption to the owner. Despite these advantages, people still have doubts about vehicle-to-grid. A lack of knowledge about vehicle-to-grid technical aspects is cited as the cause of this doubt. Policy-wise, many nations lack a well-developed plan for vehicle-to-grid. On the technological side, researchers are focusing on planning the distribution infrastructure to incorporate vehicle-to-grid and planning the vehicle-to-grid infrastructure to optimally operate the distribution network.Renewable Energy Integration into Grid and Distributed GenerationWith the help of a smart grid, renewable energy sources can be easily incorporated into power transmission and distribution systems. Due to the high cost of extending the power grid to rural areas, the electrification process in many countries is on hold. Research into completely independent island energy systems has been going on for a long time. The decentralized storage systems can guarantee a safer energy supply than large centralized systems. Such a system can use V2G technology to take advantage of renewable energy's full potential while also regulating peak demand. Surprisingly, the incorporation of renewable energy can resolve the challenging energy-water nexus that island nations face. For these countries, going from a state of "full input of energy and water" (FIEW) to "zero input of energy and water" (ZIEW) means they can stop relying on the mainland for their energy and water needs. The decarbonization of centrally managed energy systems and the installation of distributed energy systems with renewable energy as their main source are accelerating the transformation of the energy landscape. Based on the basic principle of incorporating distributed energy sources, controllable loads, and storage devices, the concept of a micro-grid has emerged. However, due to the fluctuation and interruption issues of renewable energy systems, managing distributed energy sources in the microgrid is a challenging task. Multi-agent-based approaches are able to handle such complexities. Distributed generation has many benefits, including efficiency gains, reduced carbon emissions, and the delaying of costly transmission line upgrades and expansions. The numerous economic, technological, and environmental advantages of distributed generation have led to its widespread acceptance as the future power paradigm. Additionally, unlike large traditional grids, distributed energy systems that are connected to small-scale generators can respond more quickly and effectively to changes in load curves. So, one of the primary goals of ongoing smart grid research and development activities is to better integrate distributed generation resources into the grid.Energy Storage SystemsFaster adoption of renewable energy sources and smart grids relies heavily on electric power storage facilities. Because of their high price and low efficiency, traditional energy storage systems were not particularly useful, relevant, or functional. It is crucial to take advantage of renewable energy generation and storage in order to set up a fully functional and optimized dynamic grid. The development of these industries requires the formulation of a crucial set of financial and regulatory policies. Devices that store and release energy can meet peak power demands without using additional, costly forms of generation. In addition, storage devices can play a crucial role in enabling cost-effective, efficient, and environmentally friendly operation of the distribution network by offsetting the demand and supply mismatch.Communication TechnologiesThe term "advanced metering infrastructure" (AMI) refers to the combination of "smart" meters, "communication networks," "meter data management systems," "software platforms," and "user interfaces". Through AMI, the utility and the end-user are able to have a two-way interaction about the end-user's energy consumption as well as the utility's price signals and load-control signals. The evolution of the smart grid’s communication technology is shown in Fig. 1.Fig. 1: Smart Grid Evolution Source: IEEE AccessThe data is sent to a centralized server, where it is stored and processed. Therefore, there must be a means of communication established that allows for the free flow of data. The information exchange channel is two-way communication. The utility's capacity for asset maintenance, energy demand management, and energy planning can all be managed through two-way communication. It is anticipated that AMI will become "smarter" in the future. It is predicted that in the near future, consumers will opt for Artificial Intelligent Meters (AIMs) that can regulate their power usage independently, irrespective of external signals. AIM also reduces the amount of human involvement in particular decision-making processes. With computational power and channel bandwidth being limited factors, it is difficult to provide a lightweight communication architecture for the transmission of big data that can quickly respond to network congestion and management requirements. As a result, many different algorithms for transmitting large amounts of data are currently under development.Summarizing the Key PointsSmart grid research aims to integrate distributed generation resources into the grid for improved efficiency and functionality. Energy storage systems are crucial for the adoption of renewable energy sources and the optimization of the dynamic grid. Electric vehicles have the advantage of portability and can contribute to the grid through vehicle-to-grid initiatives. Range anxiety and lack of knowledge hinder the widespread adoption of electric vehicles and vehicle-to-grid programs. Communication technologies play a vital role in enabling the flow of data and information exchange in the energy sector. Advanced metering infrastructure (AMI) enables two-way communication between utilities and end-users for efficient energy management. Artificially Intelligent Meters (AIMs) are predicted to become smarter, reducing human involvement in decision-making processes.ReferenceJoseph, Akhil, and Patil Balachandra. “Smart Grid to Energy Internet: A Systematic Review of Transitioning Electricity Systems.” IEEE Access 8 (2020): 215787–805. https://doi.org/10.1109/access.2020.3041031.

Overview: This article explores the opportunities and challenges of integrating clean technologies and information and communication technologies for efficient and sustainable energy management in smart grids.  Decarbonization has accelerated the fundamental shift in society toward clean technologies. Electrical energy will be a significant factor in the decarbonization process. Electrical energy is one of the most common forms of energy carriers and is seeing growing usage. Increasing electricity demand forces the expansion of the generation and transmission systems, requiring a significant amount of investment.  Power loss and reactive power flow in the transmission systems make the conventional, centralized structure of power systems less efficient. Distributed generations (DGs) have been incorporated into low- and medium-voltage distribution networks in order to increase system availability, efficiency, and cost-effectiveness. Furthermore, renewable-based distributed generation aids in the decarbonization of the electric energy sector.Evolution of Smart GridDistribution systems that have been powered up can function as a microgrid in the absence of the utility grid. A microgrid is an island-based distribution system that uses local distributed generation and energy storage to provide critical loads in island mode. Distribution systems with microgrid capabilities will have some benefits, such as increased productivity, dependability, accessibility, and power quality.  However, information and communication technologies (ICTs) are necessary for the optimal and reliable operation of various distributed generation and energy storage systems in microgrids. To operate modern energy distribution systems as efficiently and dependably as possible, the smart grid concept has been introduced. To operate and plan grid systems with irregular output and variable power sources, ICTs must be available at both the generation and transmission levels. These systems enable power systems to meet customer demands by intelligently monitoring, making decisions, and controlling contemporary power systems. In addition to incorporating DGs into distribution networks, large-scale renewable power plants like photovoltaic (PV) and wind energy systems have been widely installed in power systems, and the power grids are currently moving toward more fully renewable energy systems. Figure 1. Concept of a Distributed Power Generation System Source IEEE Access Along with efficiency, flexibility, and operability benefits, smart grid technologies also present new difficulties for the design and management of modern power systems. Restructuring the power grids to incorporate renewable energy sources, microgrid technologies, ICTs, and power electronics can result in these difficulties. Smart Grid’s Future DirectionsThe idea of smart grids has changed with the development of technology. In recent years, the smart grid's research and development have increased. As a result, the implementation of smart grids has changed from virtual to real-time. However, there are several situations in which action needs to be taken to turn it into a complete real-time network service.Big Data ManagementThe input of real-time data is a key factor in a smart grid. It serves as the backbone of the network's functioning. Power transmission, generation, transformation, and utilization data are being collected for reliable and efficient working. All decisions are made based on the information gathered. The collection and management of such a vast amount of real-time data is a significant problem.  To predict the demand for energy at various locations, the algorithms must use all the data gathered from the sensors and associated devices. To produce the best results, the algorithms must be optimized. One of the main study subjects in smart grid technology is IT infrastructure, data gathering, governance, data processing, and, most critically, data security.Investing in Smart Grid InfrastructureTo reduce carbon emissions, a number of countries have started implementing smart grid infrastructure. Many of them are engaged in projects designed to evaluate the feasibility of the network. The construction of the smart grid infrastructure has already started in nations including Australia, South Korea, and Japan. The initial investment, though, is the main concern. The ongoing maintenance of the entire network further raises the overall cost.  Therefore, before making an investment of this size in the infrastructure, a thorough financial report should be made. The price of smart grids in a few emerging nations is shown in Table 1. This will estimate the starting sum that a developing nation must invest in order to create smart grid infrastructure. Additionally, it will provide a general concept of the maintenance costs as well as any other extra expenses necessary to guarantee the network's efficient operation.Business Model RestructuringThe business model has undergone considerable adjustment as a result of the new smart grid's emergence. New technologies have altered consumer perceptions and created a network of distributed power sources. Consequently, business practices are evolving. It is necessary to implement new policies to benefit consumer communications. To integrate the load and the generated power, the utility business model should be put into practice at the distribution level.Modernization of the Energy Production SystemCustomer needs have evolved due to the smart grid's evolution. As a result, there are fluctuations in energy demand. To accommodate the demand response, the system's capacity should be raised. Additionally, the energy-producing systems must change their production policies to integrate into the smart grid network. In the smart grid network, cloud-based data management strategies are applied. The existing system needs to be upgraded and changed in order to establish IoE activities.  Cyber-physical power systems are the smart operation of future power systems, which include distributed generation, microgrids, and demand side management while utilizing information and communication technologies over the physical system. The ICTs are vulnerable to cyberattacks, data loss, and hardware failure. ICT malfunctions will reduce system performance and must be taken into account when planning a power system. Additionally, when operating power systems, cybersecurity must be taken into consideration because malicious intrusions from cyberattacks could result in a loss of power or energy. The network should incorporate security measures against cyberattacks.Summarizing the Key PointsThe paper highlights the importance of information and communication technologies in the optimal and reliable operation of distributed generation and energy storage systems in microgrids.The integration of information and communication technologies with power systems can lead to the development of cyber-physical power systems or smart grids.Smart grids enable power systems to meet customer demands by intelligently monitoring, making decisions, and controlling contemporary power systems.However, the adoption of clean technologies and information and communication technologies presents new challenges for the design and management of modern power systems.Smart grid technologies also present new difficulties for design and management but offer significant benefits such as flexibility, efficiency, operability, reliability, accessibility, and power quality. Reference(s)1.Peyghami, S., Palensky, P., & Blaabjerg, F. (2020). An Overview on the Reliability of Modern Power Electronic Based Power Systems. IEEE Open Journal of Power Electronics, 1, 34–50. https://doi.org/10.1109/ojpel.2020.29739262.Pal, R., Chavhan, S., Gupta, D., Khanna, A., Padmanaban, S., Khan, B., & Rodrigues, J. J. P. C. (2021, August 28). A comprehensive review on IoT‐based infrastructure for smart grid applications. IET Renewable Power Generation, 15(16), 3761–3776. https://doi.org/10.1049/rpg2.122723.Rafique, Z., Khalid, H. M., & Muyeen, S. M. (2020). Communication Systems in Distributed Generation: A Bibliographical Review and Frameworks. IEEE Access, 8, 207226–207239. https://doi.org/10.1109/access.2020.3037196