Impact of wind power generating system integration on frequency stabilization in multi-area power system with fuzzy logic controller in deregulated environment

Among the available options for renewable energy integration in existing power system, wind power is being considered as one of the suited options for future electrical power generation. The major constraint of wind power generating system (WPGS) is that it does not provide inertial support because of power electronic converters between the grid and the WPGS to facilitate frequency stabilization. The proposed control strategy suggests a substantial contribution to system inertia in terms of short-term active power support in a two area restructured power system. The control scheme uses fuzzy logic based design and takes frequency deviation as input to provide quick active power support, which balances the drop in frequency and tie-line power during transient conditions. This paper presents a comprehensive study of the wind power impact with increasing wind power penetration on frequency stabilization in restructured power system scenario. Variation of load conditions are also analyzed in simulation studies for the same power system model with the proposed control scheme. Simulation results advocates the justification of control scheme over other schemes.     

New control strategy for 2-stage grid-connected photovoltaic power system

This work deals with the performances and responses of a grid-connected photovoltaic (PV) plant in normal and disturbed modes. The system is composed of a solar array, a dc–dc converter and a three-phase inverter connected to the utility grid. On the one hand a suitable control of the dc–dc converter is developed in order to extract the maximum amount of power from the PV generator. On the other hand an active and reactive power control approach (PQ) has been presented for the inverter. This method can provide a current with sinusoidal waveform and ensure a high power factor. Therefore, the grid interface inverter transfers the energy drawn from the PV into the grid by ensuring constant dc link voltage. Modeling and controlling were carried out using the informational graph of causality and the macroscopic energy representation methods. The simulation under MATLAB/SIMULINK and the experimental results show the control performance and dynamic behavior of grid-connected PV system in normal and disturbances modes.     

Dead-beat instantaneous power control for off-board charger of electric vehicle for V2G application

Dead-beat instantaneous power control strategy for electric vehicle off-board V2G charger is presented in this paper, to suppress harmonic pollution to power grid and realize bi-directional flow of electric energy. The charger consists of three-phase voltage source PWM grid-side converter and bi-directional dc/dc converter. A double closed-loop for three-phase voltage source PWM grid-side converter is designed firstly. And the outer voltage loop is used to keep dc bus voltage constant. The expected switching voltage components are achieved by substituting predicted instantaneous power with its instruction value, to form the inner dead-beat instantaneous power loop. Then a voltage–current double closed-loop for bi-directional dc/dc converter is proposed to implement two-stage charging, combining with constant-current charging and constant-voltage charging. Finally, the effectiveness and feasibility of the proposed control strategy are verified on the power-hardware-in-loop-simulation platform.     

不平衡电网电压下T型三电平光伏并网逆变器的有限集模型预测控制

为实现电网电压不平衡时对T型三电平光伏并网系统输出功率和电流质量的控制,以达到入网功率平稳或电流正弦为控制目标,结合光伏阵列输出功率前馈,在两相静止坐标系下提出一种直流母线电压外环PI控制、并网电流内环有限集模型预测控制的控制策略,并在电压外环中引入2倍频陷波器以获得平滑的入网功率参考值。仿真结果表明:当电网电压不对称时,采用所提控制策略能够实现对入网有功、无功功率2倍频脉动及负序电流的分别抑制或协调控制,且并网电流谐波畸变小、入网电能质量高,同时实现T型三电平逆变器的中点电位平衡。     

微网中储能系统的控制与分析

在微网系统中,大功率电力负荷的投切会导致电网电压幅值和频率产生波动。将储能装置应用于微网系统中,可以通过逆变控制单元,实时监控电网电压波动,即时调节配电网输送的有功、无功功率大小,从而达到平抑电网电压波动的效果。采用了电压频率环控制和有功、无功补偿控制相结合的控制算法,可以即时检测电网电压波动并进行快速补偿,具有较强的有功、无功调节能力。通过构建微网模拟环境,对比试验了不加储能装置和接入储能装置后微电网投入不同电力负荷时的电压波动情况,验证了控制策略的有效性和正确性。     

Modeling and simulation of three phase multilevel inverter for grid connected photovoltaic systems

This paper presents a control for a three phase five-level neutral clamped inverter (NPC) for grid connected PV system. The maximum power point tracking (MPPT) is capable of extracting maximum power from the PV array connected to each DC link voltage level. The MPPT algorithm is solved by fuzzy logic controller. The fuzzy MPPT is integrated with the inverter so that a DC–DC converter is not needed and the output shows accurate and fast response. A digital PI current control algorithm is used to remain the current injected into the grid sinusoidal and to achieve high dynamic performance with low total harmonic distortion (THD). The validity of the system is verified through MATLAB/Simulink and the results are compared with three phase three-level grid connected NPC inverter in terms of THD.     

微电网中并列运行逆变器控制策略研究

考虑到微网内分布式电源的多样化和分散性,提出一种PQ控制与基于下垂特性的电压电流控制相结合的控制策略。PO控制可以实现间歇性微源的最大能源利用率,基于下垂特性的电压电流控制在微网运行模式或结构发生变化时,可以很好地实现负荷功率共享,以维持微网频率和电压的稳定。此控制策略既可以在并网模式下运行,也可以在孤岛模式下运行。并在PSCAD／EMTDC仿真平台上搭建了微电网仿真模型,验证了此控制策略的正确性和有效性。     

基于LC滤波的光伏逆变器电感电流反馈控制策略研究

针对光伏并网逆变器的特点,基于电感电流反馈控制的光伏并网逆变器,提出了参考电流相位超前的电流内环控制策略。通过分析单相并网逆变器结构,推导了LC滤波器上电压电流矢量关系。加入电网电压瞬时值前馈解耦控制,研究了比例调节和准比例谐振调节两种策略下参考电流与输出电流的关联。基于一台3 kW逆变器为实验平台的理论分析和实验结果表明,采用该策略的逆变器并网电流时刻跟踪电网电压频率和相位,功率因数为1,并网电流谐波失真度低于3%。     

Applications of one-cycle control to improve the interconnection of a solid oxide fuel cell and electric power system with a dynamic load

Adding distributed generation (DG) is a desirable strategy for providing highly efficient and environmentally benign services for electric power, heating, and cooling. The interface between a solid oxide fuel cell (SOFC), typical loads, and the electrical grid is simulated in Matlab/Simulink and analyzed to assess the interactions between DG and the electrical grid. A commercial building load profile is measured during both steady-state and transient conditions. The load data are combined with the following models that are designed to account for physical features: a One-Cycle Control grid-connected inverter, a One-Cycle Control active power filter, an SOFC, and capacitor storage. High penetration of DG without any power filter increases the percentage of undesirable harmonics provided by the grid, but combined use of an inverter and active power filter allows the DG system interconnection to improve the grid tie-line flow by lowering total harmonic distortion and increasing the power factor to unity.     

Design of a robust and efficient power electronic interface for the grid integration of solar photovoltaic generation systems

Nowadays, the penetration of photovoltaic (PV) solar power generation in distributed generation (DG) systems is growing rapidly. This condition imposes new requirements to the operation and management of the distribution grid, especially when high integration levels are achieved. Under this scenario, the power electronics technology plays a vital role in ensuring an effective grid integration of the PV system, since it is subject to requirements related not only to the variable source itself but also to its effects on the stability and operation of the electric grid. This paper proposes an enhanced interface for the grid connection of solar PV generation systems. The topology employed consists of a three-level cascaded Z-source inverter that allows the flexible, efficient and reliable generation of high quality electric power from the PV plant. A full detailed model is described and its control scheme is designed. The dynamic performance of the designed architecture is verified by computer simulations.     

单相有源电力滤波器新型数字化控制技术

提出了一种单相有源电力滤波器新型数字化控制技术。只需检测系统电流和逆变器的直流侧电容电压,经过简单的计算,可求出各个开关周期内开关管的占空比。提出的控制技术易于实现全数字化,可避免传统瞬时无功理论的复杂计算,克服滞环控制难以数字化的缺点。通过对电流积分环节的调节作用,实现了电流直流分量的闭环控制,并提高了电路可靠性。仿真结果表明,新方案可有效的消除系统电流的直流分量,实现谐波电流抑制。     

超导储能对并网型风电场运行性能影响的仿真分析

采用超导储能(SMES)可以改善风电场并网运行的稳定性,针对风电系统中出现的联络线短路故障和风电场的风速扰动,提出利用超导储能安装点的电压偏差信号作为超导储能有功控制器的控制策略。为了验证这种策略的有效性,建立了风电机组和超导储能装置的数学模型,并利用MATLAB/Simulink软件搭建了风电场接入电网后的仿真模型。仿真结果表明,采用该控制策略不仅可以在网络故障后有效地提高风电场的稳定性,而且能够在快速的风速扰动下平滑风电场的功率输出,降低风电场对电网的冲击。     

Rapid transaction to load variations of active filter supplied by PV system

This paper deals with the analysis and control of a photovoltaic (PV) system connected to the main supply through a Boost converter and shunt active filter supplied by a PV system providing continuous supply of nonlinear load in variation. A robust control of a PV system connected to the grid while feeding a variable nonlinear load is developed and highlighted. This development is based on the control of the Boost converter to extract the maximum power from the PV system using the Perturb and Observe (P and O) algorithm in the presence of temperature and illumination. The proposed modeling and control strategy provide power to the variable nonlinear load and facilitates the transfer of power from solar panel to the grid while improving the quality of energy (harmonic currents compensation, power factor compensation and dc bus voltage regulation). Validation of the developed model and control strategy is conducted using power system simulator Sim-Power System Blockset Matlab/Simulink. To demonstrate the effectiveness of the shunt active filter to load changes, the method of instantaneous power (pq theory) is used to identify harmonic currents. The obtained results show an accurate extraction of harmonic currents and perfect compensation of both reactive power and harmonic currents with a lower THD and in accordance with the IEEE-519 standard.     

Single-stage sine-wave inverter for an autonomous operation of solar photovoltaic energy conversion system

This paper proposes a high performance single-stage inverter topology for the autonomous operation of a solar photovoltaic system. The proposed configuration which can boost the low voltage of photovoltaic (PV) array, can also convert the solar dc power into high quality ac power for driving autonomous loads without any filter. An MPPT circuit with parallel connection is implemented so that the part of the energy generated is processed by the dc–dc converter to supply dc loads. The line current total harmonic distortion (THD) obtained using this configuration is quite reasonable. The proposed topology has several desirable features such as low cost and compact size as number of switches used, are limited to four as against six switches used in classical two-stage inverters. In this paper analysis, simulation and experimental results are presented.     

一种基于SVPWM并网逆变器电流控制的研究

为提高光伏并网发电系统的输出电能质量,在重复控制策略的基础上,提出一种基于SVPWM并网逆变器电流控制的重复PI复合控制方法。该方法通过重复控制策略来抑制由死区等因素引起的周期性扰动,PI控制策略用来提高系统的动态性能,两种控制策略互为补充以提高系统的动态和稳态性能,同时,在并网逆变器直流侧加入电压闭环以稳定直流母线电压。通过Matlab/Simulink仿真分析,三相并网逆变器输出电流的总谐波畸变率为1.32%。实验结果验证了该复合控制方法的有效性。     

PSCAD/EMTDC-based simulation of wind power generation system

This paper proposes a novel simulation method of wind power generation system (WPGS) using PSCAD/EMTDC. The pitch control-based rotation speed control scheme of turbine under variable wind speed is implemented. For the purpose of achieving effective and user-friendly simulation method for utility interactive (grid connected) WPGS, real weather condition-based WPGS simulation (RW–WPGS) is performed using PSCAD/EMTDC. It is not easy, in general, to consider the RW conditions in the WPGS simulation using the EMTP or PSPICE type of simulators. External parameters of the RW conditions, however, are necessary to improve the simulation accuracy.The components modeling of wind turbine system is also studied and the real weather conditions are introduced by the interface method of a non-linear external parameter of the PSCAD/EMTDC. The outcomes of the simulation demonstrate the effectiveness of the proposed simulation scheme.     

Fault tolerant control strategy for modular PWM current source inverter

In this paper, a fault-tolerant control method for an input-series output-parallel modular grid-tied pulse-width modulation (PWM) current source inverter is proposed to address the most commonly seen single symmetrical gate-commutated thyristor (SGCT) open-circuit fault problems. This method actively offsets the neutral point of the current space vector to ensure a sinusoidal output of the grid current, and it can achieve the upper limit power of the inverter under the condition of a single SGCT open-circuit fault. In addition, an active damping control method based on grid harmonic current feedback is proposed after analyzing the influence of the transformer ferromagnetic resonance caused by the neutral point offset on the power quality of the grid current. It has been demonstrated that the proposed method effectively suppresses the resonance caused by the transformer and the modified modulation, improving the grid current’s power quality.     

Power quality improvement using fuzzy logic controller for five-level shunt active power filter under distorted voltage conditions

In this paper, a five-level inverter is used as a shunt active power filter (APF), taking advantages of the multilevel inverter such as low harmonic distortion and reduced switching losses. It is used to compensate reactive power and eliminate harmonics drawn from a thyristor rectifier feeding an inductive load (RL) under distorted voltage conditions. The APF control strategy is based on the use of self-tuning filters (STF) for reference current generation and a fuzzy logic current controller. The use of STF instead of classical extraction filters allows extracting directly the voltage and current fundamental components in the α-β axis without phase locked loop (PLL). The MATLAB fuzzy logic toolbox is used for implementing the fuzzy logic control algorithm. The obtained results show that the proposed shunt APF controller has produced a sinusoidal supply current with low harmonic distortion and in phase with the line voltage.     

甘肃330 kV、220 kV电网电磁环网解环研究

甘肃省网目前存在电磁环网问题,不利于电网安全稳定经济运行,通过对白银电网环网解环的研究,提出了电磁环网解环的条件及电磁环网解环方案。运行结果表明,电磁环网解环运行后,简化了网络接线,优化了电网潮流,使各电网都不同程度的降低了网络损耗,各电网都满足线路“N-1”校验的要求,提高了电网稳定性;同时优化了电网无功潮流流向,各电网无功潮流更趋于合理,经过校验计算各电网无功配置都满足要求。     

针对并网型风储微网的飞轮储能阵列系统控制方法CSCD

由于新能源发电存在波动性和间歇性,其大量接入时会给电网运行带来新的困难,而利用储能技术提高新能源的可调度性是当前研究的热点。为缓解新能源并网对电力系统的不良影响,针对并网型风储微网提出了一种基于飞轮储能阵列系统的分层优化控制方法,上层优化中心根据功率缺额和各台飞轮的转速建立相应充/放电优化模型,并求解相应飞轮的功率参考值;下层飞轮控制器采用双模双环控制方法,实现飞轮转速和输出功率的控制,最后通过MATLAB/Simulink仿真验证了所提控制方法的有效性和可行性。