查看更多>>摘要：Inverter-based resources(IBRs),such as wind and photovoltaic generation,are characterized by low capacity and extensive distribution,which can exacerbate the weak properties of power systems.Precise identification of weak system status is essential for ensuring the security and economic efficiency of IBR integration.This paper proposes the index of the multiple renewable short-circuit ratio(MRSCR)and its critical value calculated by the voltage(CMRSCR)to provide a comprehensive assessment of power system strength in the presence of high IBR penetration,enhancing the accuracy and reliability of system strength evaluation.First,we introduce a single-infeed equivalent model of the power system integrating multiple IBRs.We examine the factors associated with system properties that are crucial in the strength assessment process.Subsequently,the MRSCR is derived from this analysis.The MRSCR describes the connection between system strength and voltage variation caused by power fluctuations.This implies that voltage variation caused by IBR power fluctuations is more pronounced under weak grid conditions.Following this,the CMRSCR is proposed to precisely evaluate the stability boundary.The disparity between MRSCR and CMRSCR is utilized to evaluate the stability margin of the power system.Unlike a fixed value,the CMRSCR exhibits higher sensitivity as the system approaches a critical state.These indexes have been implemented in the PSD power tools and power system analysis software package,facilitating engineering calculation and analysis of bulk power systems in China.Finally,simulation results validate the effectiveness of the proposed indexes and the research findings.
查看更多>>摘要：Hybrid energy storage system(HESS)is an effective way to mitigate wind power fluctuations on multi-time scale,and can improve influence of large-scale grid-connected wind power on stability and reliability of power system.A novel methodology named zero-phase controlled auto-regressive inte-grated moving-average(CARIMA)filter is proposed to integrate HESS to smooth wind power fluctuations.First,a design method for zero-phase CARIMA filter is provided,and then used to determine grid-connected power for a wind storage system and size HESS.The reasons,direct current(DC)component caused by energy storage efficiency and grid-connected power delay caused by phase shift,for causing superfluous energy storage configuration are revealed.In addition,a nonlinear programming scheduling strategy considering battery degradation is proposed.Power imbalance caused by efficiency difference during dynamic adjustment of energy storage output power is addressed.Further-more,thermostatically controlled loads(TCLs)are integrated in sizing and scheduling HESS to reduce energy storage demand and improve operating conditions of energy storage.Finally,effectiveness of the proposed strategy is verified by a case study.
查看更多>>摘要：Data-driven artificial intelligence technologies have emerged as increasingly fascinating tools for assessing power sys-tem security.However,their inherent mechanism of inexplicabil-ity and unreliability now limits their scalability in power systems.To address this problem,this paper proposes a neural network design method empowered by physical mechanisms for power sys-tem security assessment.It incorporates geometric characteristics of dynamic security regions into the network training process and constructs connections between network structure and system's unstable mode,which can perform security assessment with a neural network efficiently while ensuring physical plausibility.Furthermore,a credibility evaluation mechanism is established to ensure credibility of neural network predictions and reduce misclassifications.Finally,effectiveness of the proposed method is verified on test systems.Methods and considerations in building a neural network with interpretable structures and credible predictions can provide a reference for machine intelligence applied in other industrial systems.
查看更多>>摘要：India's energy crisis can be resolved by using reliable sources of renewable resources,such as solar energy with minimum adverse ecological effects.Several photovoltaic projects have been sanctioned based on rooftop models and land-based solar parks to address energy security concerns.India's strategy focusing on increasing the installation of new solar plants,lead to the vast expansion of the renewable energy market.This paper explores the Indian government policies,current approaches,significant achievements and a scenario for solar power in India.It also summaries various technological options,research,awareness and outreach activities for the deployment of solar energy.These supportive policies provide tax exemptions,attractive tariff plans,and economic incentives which contribute to the sustainable development of the nation.
查看更多>>摘要：Transient voltage stability analysis(TVSA)of power systems is one of the most computationally challenging tasks in dynamic security assessment.To reduce the complexity of TVSA,this paper proposes an improved expanding annular domain(improved EAD)algorithm to estimate the domain of attraction(DA)of power systems containing multiple induction motors(IMs),whose improvements are concerned with relaxing the restriction on critical value and simplifying iteration steps.The proposed algorithm can systematically construct Lyapunov function for lossy power systems with IMs and their slip constraints.First,the extended Lyapunov stability theory and sum of squares(SOS)programming are presented,which are powerful tools to construct Lyapunov function.Second,the internal node model of IM is developed by an analogy with that of a synchronous generator,and a multi-machine power system model by eliminating algebraic variables is derived.Then,an improved EAD algorithm with SOS programming is proposed to estimate the DA for a power system considering the slip constraint of IM.Finally,the superiority of our method is demonstrated on two modified IEEE test cases.Simulation results show that the proposed algorithm can provide a better estimated DA and critical clearing slip for power systems with multiple IMs.
查看更多>>摘要：Nowadays,high penetration of wind power is in-tegrated into power grids,and WTs usually adopt the MPPT algorithm to maximize power output,which decouples the rotor speeds of wind turbines(WTs)and system frequency.Therefore,WTs cannot provide frequency support like conventional genera-tors.To that end,especially avoiding WTs aggravating excessive power generation during over-frequency events,optimal droop control is proposed to reduce power output by fully utilizing WTs'own potential in accelerating rotors.Due to unreliable communication in a wind farm,a game theory-based distributed rotor kinetic energy optimization model is developed to obtain the ideal WT rotor speed and power reduction.Next,the optimal droop gains for WTs are designed to be proportional to their ideal power reduction.Then,not only the frequency support capability of WTs is fully activated,but also as much wind power as possible will be stored as kinetic energy into the accelerated rotor blades.Finally,the effectiveness and rationality of the proposed control are verified in MATLAB and DIgSILENT.
查看更多>>摘要：Photovoltaic power(PV)is integrated into the grid through power inverters.But the inverters lead PV to lose some of the characteristics of conventional power sources that are conducive to grid stability,such as reduced inertia,reactive power regulation capability,and fault ride-through capability.After introducing the power angle characteristics of a motor-generator pair(MGP)and reviewing MGP's existing control methods and PV's characteristics,this paper proposes a DC voltage feedback control method that can make MGP follow the fluctuations of a PV source.The proposal is studied experimentally,with the following results:(1)An MGP system can follow the power fluctuation of PV by using a DC voltage feedback control method.(2)Such feedback enables the PV to have a self-synchronization characteristic,which enables PV to actively contribute to the stability of the grid.
查看更多>>摘要：This paper examines the harmonic oscillations in a grid-connected PV generation farm(PVGF)caused by the parallel connection of an increased number of PV generation units(PVGUs).An equivalent model of the grid-connected PVGF is derived,which clearly explains why there are internal and ex-ternal oscillation modes in the grid-connected PVGF.An indicator of impedance multiplication(IIM)is proposed to quantitatively estimate the impact of the increased number of PVGUs in parallel connection.The analysis in this paper reveals the mechanism about why the damping of external oscillation modes may decrease when more PVGUs are in parallel connection under the condition that the IIM is positive.An example grid-connected PVGF is presented in this paper to demonstrate and evaluate the derived analysis and conclusions.A method for designing the damping controllers to ensure a negative IIM is proposed.With the damping controllers being installed,the risk of growing harmonic oscillations caused by the increased number of the PVGUs in parallel connection can be effectively eliminated.
查看更多>>摘要：This paper illustrates a new bi-objective optimiza-tion model of real-time automatic generation control dispatch in a performance-based frequency regulation market.It attempts to simultaneously minimize the total power deviation and the regulation mileage payment via optimally distributing the real-time total generation command to different regulation units.To handle this problem,an efficient non-dominated sorting genetic algorithm Ⅱ is adopted to rapidly obtain a high-quality Pareto front for real-time AGC dispatch.A dynamic ideal point based decision making technique is designed to select the best compromise solution from the obtained Pareto front according to the minimization of the total regulation variation,which can effectively avoid an excessive regulation variation for each unit.Finally,two testing systems are used to verify the performance of the proposed technique.
查看更多>>摘要：A DC grid based on half-bridge modular multilevel converters(HB-MMC)is a feasible means to realize the friendly grid connection of renewable energy.To solve problems such as the high cost and technical difficulty of DC circuit breakers(DCCB),a coordinated control method for fault current sup-pression of DC grid connecting wind power is proposed.The key influencing factors of DC fault current are revealed by fault characteristics analysis,and an adaptive current-limiting control method for MMC is proposed,whose parameter selection principles are designed to ensure the safe operation of equip-ment while achieving effective suppression of fault current.In addition,a novel configuration method of dissipative resistors with the current-limiting function is proposed,which can solve the problem of surplus power in the DC grid and reduce the current stress of converter valves.Based on this,a coordination scheme of dissipative resistors,the adaptive current-limiting control method,and DCCBs are proposed to block fault current,effectively reducing the manufacturing difficulty and cost of DCCB.Finally,a four-terminal DC grid simulation model is built based on the RTLAB OP5600 real-time digital simulation platform,and the effectiveness and feasibility of the proposed methods are verified.
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