Firefly Optimization Algorithm for the Reactive Power Control of an Isolated Wind-Diesel System

This paper investigates the application of firefly optimization algorithm to design an optimal control for voltage stability of a stand-alone hybrid renewable generation unit based on reactive power control. The studied renewable generation unit mainly consists of a permanent magnet induction generator driven by wind turbine and a synchronous generator driven by diesel engine. A STATCOM is used to stabilize the terminal load bus voltage via compensating of reactive power. The main control objective aims to stabilize the terminal load voltage against any disturbances in load reactive power and/or input wind power by adjusting the total system reactive power. This is accomplished by controlling STATCOM phase angle and hence to control the load bus voltage and also by controlling the excitation voltage of the synchronous generator. The proposed renewable energy power system based on the proposed optimal controller has been tested through step change in input wind power and load reactive power. The system performance based on the proposed control is compared with model predictive control, a robust H_∞ control, and a classical PI control.     

Functional Predictive Control for Voltage Stability Improvements of Autonomous Hybrid Wind–Diesel Power System

This study investigates the application of the model predictive control technique for voltage stability of an isolated hybrid wind–diesel power system based on reactive power control. The proposed generation system mainly consists of a synchronous generator for a diesel-generator system and an induction generator for a wind energy conversion system. A static VAR compensator is used to stabilize load voltage through compensating reactive power. Two control paths are used to stabilize load bus voltage based on model predictive control. The first control path is used to adjust the total reactive power of the system by controlling the static VAR compensator firing angle. The second is proposed to control the excitation voltage of the synchronous generator. Model predictive control is used to determine t optimal control actions, including system constraints. To mitigate calculation effort and reduce numerical problems, especially in a large prediction horizon, an exponentially weighted functional model predictive control (F-model predictive control) is applied. The proposed controller was tested through step change in load reactive power plus step increase in input wind power. The performance of the proposed system with the proposed controller was compared with classical model predictive control; moreover, this scheme is tested against parameter variations.     

Real power and frequency control of a small isolated power system

This paper describes the dynamic analysis of a small isolated power system comprising a wind turbine generator and a diesel generator. The analysis is carried out in time domain considering simplified models of the system components by taking into account the wind turbine pitch controller and the diesel engine speed governor. Wind disturbance model consisting components of gusting of wind, rapid ramp changes and random noise. The wind generator is always operated with its rated power and the additional power required by the load is supplied by the diesel generator. For better dynamic performances of wind–diesel system under wind and load disturbance conditions, two control schemes are used. In the first case, a proportional–integral (P–I) controller and in the second case a proportional–integral–derivative (P–I–D) controller are used. Gain parameters of these controllers are optimized using genetic algorithm (GA) and Particle swarm optimization (PSO) considering two different objective functions and the results are compared. The sensitivity analysis of the wind diesel system is carried out for parameter uncertainties and the stability of the system is analyzed using D-stability criterion. Analysis is also carried out to examine the effect of power injection to a 69 bus radial distribution network by wind–diesel isolated system.     

A novel quasi-oppositional harmony search algorithm and fuzzy logic controller for frequency stabilization of an isolated hybrid power system

The intermittent wind power in isolated hybrid distributed generation (IHDG) may cause serious problems associated with frequency (f) and power (P) fluctuation. Energy storage devices such as battery, super capacitor, and superconducting magnetic energy storage (SMES) may be used to reduce these fluctuations associated with f and P. This paper presents a study of IHDG power system for improving both f and P deviation profiles with the help of SMES. The studied IHDG power system is consisted of wind turbine generator and diesel engine generator. Both f and P control problems of the studied power system model are addressed in presence or absence of SMES. Fuzzy logic based proportional–integral–derivative (PID) controller with SMES is used for the purpose of minimization of f and P deviations. The different tunable parameters of the PID controller and those of the SMES are tuned by a novel quasi-oppositional harmony search algorithm. Performance study of the IHDG power system model is carried out under different perturbation conditions. The results demonstrate minimum f and P deviations may be achieved by using the proposed fuzzy logic based PID controller along with SMES.     

大型变速恒频风电系统的建模与仿真

针对兆瓦级变速恒频风力发电系统,基于Matlab/Simulink建立了包括风机、传动齿轮、双馈发电机在内的大型风电系统的整体动态数学模型。传统的最大风能捕获算法往往基于最优功率曲线和部分风机参数已知,当上述参数未知或出现扰动时,风电系统的效率会严重降低。针对此不足,基于所建模型设计了变步长最大风能捕获控制器,该控制器采用矢量控制算法,实现了发电机输出有功和无功功率的解耦控制;针对有功功率控制,控制器根据发电机输出转速扰动时,相应输出有功功率的变化变步长地调整系统输入,直到系统运行到最大风能点。仿真结果验证了风电系统模型的正确性以及控制器的有效性。     

A Novel Stand-Alone Induction Generator System for AC and DC Power Applications

This paper presents a novel dynamic model in the stationary reference frame for a diode bridge rectifier with a dc-link filter directly connected to an induction generator (IG). Moreover, a hybrid excitation system consisting of a capacitor bank with a small-scale active power filter (APF) regulates the stand-alone IG systems output voltages by controlling its reactive current component and cancels the harmonic currents generated by a nonlinear diode rectifier load. A deadbeat current control strategy for the small-scale APF is used to enhance the operating performances of the stand-alone IG. This power generating system can be used for small hydro and wind energy applications, where its generated electrical power is supplied to different load types, i.e., dc and ac loads. The measurement results validate the proposed power generating system with the deadbeat current controller as a good application for the IG to reduce the total system cost and the required number of sensors.     

集成服务环境下风电并网的无功调节(一)无功调节

依据风电功率预测和地区系统无功优化运行方案,计算风电机组电气控制参考值,通过每台风电机控制器和变频器调节风电场注入系统的无功功率。提出了集成服务环境下风电场的无功调节策略,介绍了风电数据采集与监控（SCADA）系统的功率预测过程和参数整定过程。以基于双馈异步发电机的变速恒频风电机组为例,介绍了风电机组无功调节的实现方案。     

Optimal controllers designs for automatic reactive power control in an isolated wind-diesel hybrid power system

The paper presents the bacterial foraging optimization algorithm (BFOA) and particle swarm optimization (PSO) algorithm based robust controllers for voltage deviations due to the variation of reactive power in an isolated wind-diesel hybrid power system. The isolated wind-diesel system consists of wind energy conversion system (WECS) utilizing a permanent magnet induction generator (PMIG). Further, a synchronous generator (SG) is used with the diesel engine set for power generation. The mismatch between generated and consumed reactive power in the system causes voltage fluctuations, which will occur at generator terminals. These oscillations further causes reduction in the stability and quality of the power supply. The static synchronous compensator (STATCOM) and an automatic voltage regulator (AVR) are used to suppress voltage fluctuations in an isolated wind-diesel hybrid power system. The STATCOM is used as a reactive power compensator and the AVR is used to keep the terminal voltage constant for the synchronous generator. Both STATCOM and AVR are having proportional and integral (PI) controllers with single input. In modeling for the system, a normalized co-prime factorization is applied to show the possible unstructured uncertainties in the power system such as variation of system parameters and generating and loading conditions. The performance and robust stability conditions of the control system are formulated as the optimization problem, which is based on the Hα loop shaping. BFOA and PSO algorithms are implemented to solve this optimization problem and to achieve PI control parameters of STATCOM and AVR simultaneously. In order to show the efficiency of the proposed controllers, the performance of the proposed controllers is compared with the performance of the conventional controller and genetic algorithm (GA) based PI controllers for the same wind-diesel system. The dynamic responses of the system for four different small-disturbance case studies has been carried out in MATLAB environment.     

Dynamic stability study of an isolated wind-diesel hybrid power system with wind power generation using IG,PMIG and PMSG: A comparison

This paper presents a comparative study of reactive power control for isolated wind-diesel hybrid power system in three different cases with wind power generation by induction generator (IG), permanent-magnet induction generator (PMIG) and permanent-magnet synchronous generator. The synchronous generator (SG) is used with diesel engine set. A mathematical model of the system based on small signal analysis, is developed considering reactive power flow balance equations. The variable reactive power needed by the system is provided by a static synchronous compensator (STATCOM) when wind power generation is done by IG and PMIG. When permanent-magnet synchronous generator (PMSG) is used for wind power generation, the variable reactive power demand is fulfilled by a voltage source converter (VSC) which is on the load side. A new mathematical approximation model for VSC connected with PMSG is proposed such that the voltage source converter fulfills the increased reactive power requirement of load and also increases its active power equal to the increased input wind power. Proportional and integral (PI) gains of the STATCOM and VSC controllers are optimized using integral square error criterion (ISE). The dynamic responses of the system for small (1%) step increase in load reactive power with and without 1% step increase in input wind power are shown. The paper also shows the dynamic responses of the system for random step change in load reactive power plus random step change in input wind power. The MATLAB/SIMULINK environment is used for simulation.     

基于DSP的简单、经济、实用的无功补偿器的设计

介绍了应用在风力发电机组电控系统中无功补偿控制器的研制 ,此控制器实现基于DSP的对电网电压和从发电机流出的电流快速、准确的检测 ,进行 FFT变换 ,精确算出所要补偿的无功分量的值 ,从而对电网进行适时、有效的补偿     

An optimised FOPID controller for dynamic voltage stability and reactive power management in a stand-alone micro grid

This paper proposes the application of fractional order PID controller (FOPID) for reactive power compensation and stability analysis in a stand-alone micro grid. For enhancement of voltage stability and reactive compensation of the isolated system, a SVC based controller has been incorporated. This paper emphasizes the role of fractional PID based SVC controller for reactive power management and improved stability in the stand alone micro grid, as it provides a special advantage of having two more degree of freedom for accurate tuning in comparison with the conventional controller The system performance, particularly the variations in different parameters values are studied properly with different input parameters and loading conditions. Further improvement of stability margin and optimisation of the system parameters have been achieved by the controller, based on Imperialist competitive algorithm.     

基于DSP的简单、经济、实用的无功补偿器的设计

介绍了应用在风力发电机组电控系统中无功补偿控制器的研制，此控制器实现基于DSP的对电网电压和从发电机流出的电流快速、准确的检测，进行FFT变换，精确算出所要补偿的无功分量的值，从而对电网进行适时、有效的补偿。     

VSC-HVDC控制器抑制风电场电压波动的研究

风电潮流的波动会引起并网系统公共连接点(PCC)电压的波动.在基于电压源换流器的高压直流输电(VSC-HVDC)交直流混合风电场并网系统中,控制VSC-HVDC送端站注入到PCC点的无功功率可以抑制电压波动.本文讨论了VSC-HVDC的无功功率控制器和定电压控制器抑制电压波动的原理.基于电磁暂态软件PSCAD/EMTDC建立了并网风电场模型、VSC-HVDC模型及控制系统模型.仿真结果表明VSC-HVDC采用定电压控制器的并网系统能更好的抑制电压波动,采用无功功率控制器的系统具有较好的风电场并网性能.     

双馈风电机组抑制电力系统低频振荡的鲁棒控制策略

针对大规模风电场接入电力系统面临的低频振荡问题,提出了一种双馈风电机组(doubly-fed induction generator,DFIG)附加鲁棒控制策略,通过控制双馈风电机组的转子侧无功输出向系统注入无功功率以达到提升系统阻尼的目的。首先采用TLS-ESPRIT辨识算法辨识出系统模型,然后采用基于区域极点配置的鲁棒控制理论设计附加阻尼控制器。为对所提控制方法相比于传统控制方法的优势,设计了基于极点配置的阻尼控制器。最后在PSCAD软件中搭建含风电的两区域模型验证所提控制方法的有效性。仿真结果表明DFIG附加鲁棒控制器能有效抑制电力系统低频振荡,具有较好的鲁棒性。     

SVC与桨距角控制改善异步机风电场暂态电压稳定性

研究了改善异步机风电场暂态电压稳定性的措施。基于普通异步机的恒速风电机组是目前世界上应用最为广泛的风电机组之一,由于其发出有功功率的同时吸收无功功率,会导致接入风电地区电网的电压稳定性降低。文中在DIgSILENT/PowerFactory中建立了静止无功补偿器（SVC）控制模型及风电机组桨距角控制模型,通过包含风电场的电力系统仿真计算验证了模型的有效性及其对异步机风电场与电网暂态电压稳定性的贡献。研究结果表明,在接入风电地区电网发生三相短路的大扰动故障时,SVC能够有效地帮助恒速风电机组在故障后恢复电压,提高输出的电磁功率,桨距角控制能够有效地降低恒速风电机组的输入机械功率,以上2种措施能够避免风电机组机械与电磁功率不平衡引起的异步发电机超速及电压失稳;采用SVC及风电机组桨距角控制能够改善异步机风电场的暂态电压稳定性,确保风电机组连续运行及电网安全稳定。     

Load frequency control of an autonomous hybrid power system by quasi-oppositional harmony search algorithm

This paper deals with a novel quasi-oppositional harmony search algorithm (QOHSA) based design of load frequency controller for an autonomous hybrid power system model (HPSM) consisting of multiple power generating units and energy storage units. QOHSA is a novel improved version of music inspired harmony search algorithm for obtaining the best solution vectors and faster convergence rate. In this paper, the efficacy of the proposed QOHSA is adjudged for optimized load frequency control (LFC) of an autonomous HPSM. The studied HPSM consists of renewable/non-renewable energy based generating units such as wind turbine generator, solar photovoltaic, solar thermal power generator, diesel engine generator, fuel cell with aqua-electrolyzer while energy storage units consists of battery energy storage system, flywheel energy storage system and ultra-capacitor. Gains of the conventional controllers such as integral (I) controller, proportional–integral (PI) controller and proportional–integral–derivative (PID) controller (installed as frequency controller one at a time in the proposed HPSM) is optimized using QOHSA to mitigate any frequency deviation owing to sudden generation/load change. In order to corroborate the efficacy of QOHSA, performance of QOHSA to design optimal LFC is compared with that of other well-established technique such as teaching learning based optimization algorithm (TLBOA). The comparative performances of the HPSM under the action of QOHSA/TLBOA based optimized conventional controllers (I or PI or PID) are investigated and compared in the present work. It is found that the QOHSA tuned frequency controllers improves the overall dynamic response in terms of settling time, overshoot and undershoot in the profile of frequency deviation and power deviation of the studied HPSM.     

基于MPPMSG的混合高压直流风电系统故障穿越技术

为解决传统风电系统变换级数多的问题,文中提出了一种基于多相永磁同步电机(MPPMSG)的混合高压直流风电系统拓扑。电机多套绕组分别连接单极性变流器并在直流侧串联形成高压直接接入直流母线,一套绕组向电机注入无功功率以改善电机调速和稳态性能。岸上变电站采用电网换相换流器,直流母线短路时可阻断短路电流。为解决多绕组耦合问题,MPPMSG采用了反馈解耦的控制策略。根据发电机短路特性分析,提出了直流母线短路时限制电机短路电流以及直流故障穿越的控制策略。最后,利用PSCAD/EMTDC搭建风电系统开关电路仿真模型,验证了所提控制策略的有效性。     

双馈型风力发电机功率期望值的H_∞跟踪控制

应用H∞控制理论为双馈型风力发电机系统设计了功率跟踪控制器,以保证风力发电机有功、无功功率能跟踪给定的期望值曲线。期望值曲线是根据风速大小、转子所允许的最大转速和额定功率划分为3个不同的运行区域给出的,以保证在3个运行区域风力发电机都能最大程度地获取风能,同时又可安全可靠运行。H∞控制理论可以解决干扰抑制、鲁棒稳定、信号跟踪等问题。仿真表明,所设计的控制器能驱使闭环风力发电机系统在整个运行过程中很好地跟踪所给定的功率期望值曲线,从而实现了最大风能利用且安全运行的目的。     

电压源换相高压直流输电对改善风电场电压稳定性的作用

并网风电场无功功率的波动会引起系统电压波动。在风电场混合并网系统中,通过电压源换相高压直流输电可以控制系统中的无功功率、抑制并网公共点的电压波动。文章研究了换流站无功功率控制器和定电压控制器对改善并网风电场电压稳定性的作用。基于电磁暂态软件PSCAD/EMTDC建立了并网风电场模型、电压源换相高压直流输电模型及其控制系统模型。仿真结果验证了上述控制器的正确性和可行性,表明采用定电压控制器的并网系统能更好地抑制电压波动,采用无功功率控制器的并网系统具有更好的风电场并网性能。     

Analytical Comparison of Static and Dynamic Reactive Power Compensation in Isolated Wind–Diesel System Using Dynamic Load Interaction Model

This article presents static and dynamic reactive power compensators together for a self-excited induction generator and synchronous generator based isolated hybrid power system. Reactive power is required for excitation of the induction machine and for load under steady-state and transient state operations in an isolated hybrid power system. For small perturbation of load reactive power and input wind power, the use of a dynamic compensator alone may give better voltage stability but at a high cost; in contrast, the static compensator reduces the cost on compromising with the voltage stability. The proper rating selection of both compensators used may give the optimum solution between the voltage stability as system performance and cost of compensation. The fixed costs and voltage profiles are compared for the different participations of the fixed capacitor bank and STATCOM. The interaction of the dynamic load model is also introduced to make the system more reliable and hence a new power balance equation is derived. A 10% step disturbance in the dynamic load model as well as wind power input is considered for the system study. Four different cases designed for unique participation of static and dynamic reactive power compensators are presented. The analytical comparison is based on cost, rating selection, and voltage stability under transient condition.