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.     

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.     

孤岛风柴蓄复合发电功率粒子群优化分配研究

利用可再生能源发电是海岛解决用电和吃水难问题的有效途径之一。对南海某海岛的风力资源和用电负荷分析后,提出采用风柴蓄复合发电蓄电为海岛提供电力,多余电力用于海水淡化的方案。在风柴蓄复合发电的功率设计中往往依靠经验,提出应用改进的粒子群优化方法对孤岛风柴蓄复合发电的风力发电机组台数、柴油机台数和蓄电池容量进行优化设计,优化中采用度电成本最小作为目标,最小失电率作为约束条件,能量调度按照首先应用可再生能源发电,其次是蓄电池电量,最后调用柴油机发电的策略。结果显示,改进优化方法的效率比基本的粒子群优化算法稍低,但是可以得到更加优化的结果。进一步分析了当柴油价格、负荷、蓄电池价格和风力发电机成本变化后,优化出新的风力发电机、柴油发电机和蓄电池配置,分析了优化配置变化的原因。研究可以为在孤立海岛采用风柴蓄复合发电蓄电的设计提供参考。     

单相自激式异步发电机带感性负载研究

感性负载是生产和生活中常遇到的负载类型,从静态和动态两方面人手,引入能量守恒的思想,研究了单相自激式异步发电机带感性负载的能力,通过仿真和实验证实了单相自激式异步发电机具有带静态感性负载和动态感性负载的能力,从而促进了单相自激异步发电机的实用化进程.     

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.     

提高光储柴独立微网频率稳定性的虚拟同步发电机控制策略

针对由间歇性可再生能源、柴油发电机组(DGS)和蓄电池储能系统构成的独立微网,提出一种提高系统频率稳定性的虚拟同步发电机(VSG)控制策略。首先,建立DGS在同步旋转坐标系下的数学模型并分析其输出电压与频率的阶跃特性;其次,在理论分析VSG控制与微网频率稳定性关系的基础上,将同步发电机的转子运动方程、一次调频特性及无功调压特性引入储能变换器(ESC)的控制中,使ESC具有虚拟惯性与阻尼;然后,利用MATLAB/Simulink仿真软件对比针对ESC采用传统电流控制、下垂控制及VSG控制时负载阶跃条件下的系统频率响应特性;最后,建立一套包含2台VSG及1台DGS并联的独立微网实验平台,实验结果验证了所述控制策略的正确性与有效性。     

A novel three-phase four-leg inverter based load unbalance compensator for stand-alone microgrid

This paper proposes a three-phase four-leg voltage sourced inverter (VSI) based load unbalance compensator (LUC) including its control algorithm, which is a component of a microgrid. The purpose of proposed three-phase four-leg VSI based LUC is to improve power quality of the standalone microgrid. Power quality of the microgrid which was installed in Mara-island, Korea is analyzed using a real operational data. In this work, the microgrid in Mara-island which includes a photovoltaic power generation system, a diesel generator, a battery energy storage system, and a power management system is modeled in PSCAD/EMTDC, and proposed three-phase four-leg VSI based LUC is also modeled and applies to the modeled microgrid. Power flow and stability of the modeled microgrid with the LUC is analyzed under variable irradiance and unbalance loads. The results show that the proposed LUC helps to improve stability of the stand-alone microgrid. The proposed three-phase four-leg VSI based LUC and its control algorithm can be effectively utilized to the stand alone microgrid which has large unbalance loads.     

带蓄电池SOC反馈的虚拟同步发电机系统

为了更好地模拟同步发电机的惯性环节并发挥不同储能单元的优势,对带有蓄电池和超级电容组成的混合储能单元的虚拟同步发电机系统进行研究,详细分析了系统的数学模型和控制策略,考虑储能元件自身的特点以及蓄电池的使用寿命,提出了含蓄电池荷电状态(state of charge,SOC)反馈的虚拟同步发电机系统控制策略。通过搭建相应的MATLAB/SIMULINK仿真模型,分析蓄电池在正常充电状态与SOC达到上限时储能的功率分配情况,验证所提出的控制策略的正确性和有效性。结果表明,所提出的带蓄电池SOC反馈控制的虚拟同步发电机系统,可在功率波动时实现功率合理分配,在维持系统的稳定性的同时延长储能的使用寿命。     

SEIG-Based Renewable Generation for MVDC Ship Power System with Improved Power Quality

The global energy consumption is increasing day by day. This increased energy demand can only be fulfilled through large-scale renewable energy integration. This article presents the mathematical modeling, control, and integration of a bio-fuel prime mover fed self-excited induction generator (SEIG) for medium voltage direct current (MVDC) ship power system. A three-phase current controlled voltage source inverter (VSI) working as a static synchronous compensator (STATCOM) injects compensating currents at the point of common coupling (PCC) for harmonic elimination and regulation of the generated voltage under varying load. The VSI is connected at the PCC through a three-phase zig-zag/star transformer which reduces the voltage stress at the DC link. An indirect current technique based controller is used to generate gating pulses for the STATCOM. The MVDC load zone is modeled as an integral sliding mode controlled DC-DC converter feeding ship service loads in shipboard system. Hardware realization of the proposed system has been implemented with 3.7kW induction generator.     

家用混合发电系统的能量优化控制策略

家庭负载频繁出现瞬间的峰值功率需求,由燃料电池/蓄电池组成的混合发电系统是最清洁和高效的发电方式之一.燃料电池仅满足基本负载,由蓄电池放电以满足瞬间的峰值功率需求.研究了一个60 kW家用混合发电系统,该系统由质子交换膜燃料电池(PEMFC)和阀控铅酸蓄电池组成,设计为10个家庭同时供电.在保证系统可靠性和持久性的同时,为了提高整个混合发电系统的工作效率和燃料经济性,在系统仿真和分析的基础上详细描述了一种基于规则的能量优化控制策略.仿真实验结果表明,与燃料电池单独供电相比,60 kW混合发电系统通过优化2种能源之间的功率分配,能够在响应负载的同时提高整个发电系统的工作效率和燃料经济性.     

虚拟直流发电机励磁补偿控制策略

虚拟直流发电机(VDCG)功率协调控制策略将直流电机算法嵌入到DC/DC变换器控制回路中,使其模拟直流发电机运行特性,提升直流微网直流母线电压的动态稳定性。该控制通过功率分配环实现不同容量储能装置间的功率协调分配,但已有的VDCG功率协调控制策略均采用固定励磁磁通作为虚拟电机励磁系数,当再生能源输出功率发生波动或负载发生投切时,直流母线电压会产生稳态电压偏移。为消除母线电压偏移,在详细分析VDCG功率协调控制工作机理的基础上,提出虚拟直流发电机励磁补偿控制策略,通过实时补偿VDCG励磁,消除母线电压偏移,稳定直流母线电压。构建储能装置双机并联光储直流微网仿真及实验平台,分别在再生能源功率波动和负载投切情况下对传统固定励磁磁通功率协调VDCG控制及所提VDCG励磁补偿控制策略进行对比仿真及实验验证,证明所提控制策略的正确性。     

基于PSCAD的风电场低电压穿越无功支撑仿真研究

首先分析风电场低电压穿越(low voltage ride-through,LVRT)能力,然后介绍以双馈感应发电机(doubly-fed induction generator,DFIG)为主体的风电场模型以及静止同步补偿器(static synchronous compensator,STATCOM)的控制策略。最后将STATCOM和静止无功补偿器(static var compensator,SVC)分别应用到含风电场的无穷大系统中,在电力系统仿真软件PSCAD上搭建模型,并对系统故障状态进行仿真,在此基础上分析STATCOM和SVC的无功补偿特性,并对补偿效果进行比较。仿真结果表明无功补偿装置可以在系统故障后提供无功支撑,提高了风电场的低电压穿越能力,并且STATCOM无功补偿性能较SVC更优。     

基于STATCOM的超级电容储能系统的风电并网

为了提高电网的电能质量,探讨了一种与永磁同步发电机(PMSG)相连接的电网控制和运行策略。该电机以直驱变速风电机组和静止同步补偿器(STATCOM)为基础,STATCOM的应用是通过风力涡轮机的不脱网运转能力来提高了系统性能,发电机侧变换器的控制策略是应用STATCOM控制器实现传输效率最大化。通过Matlab对其进行了仿真验证。仿真结果表明,带有STATCOM的超级电容器能量存储系统能够提高风能系统电网故障或扰动时的稳态和动态性能。     

光储直流微网混合储能控制策略研究

混合储能相较于单一储能可以更好地解决微电网电压、频率波动等问题。为了充分利用混合储能系统的优势,使各储能电池优势互补,并考虑到储能变换器弱阻尼、低惯性的特点,提出了基于虚拟直流发电机控制的混合储能单元分频控制策略。该控制策略在混合储能单元分频控制的基础上,对功率密度电池储能变换器采用虚拟直流发电机控制,以增大功率密度型储能的阻尼和惯性,提升直流母线电压的动态稳定性。为验证其有效性,在微源变化和负荷波动2种工况下与传统下垂控制进行仿真对比分析,结果表明所提策略可使母线电压的波动范围限制在±0.75%以内,增强了系统的鲁棒性和稳定性并优化了储能单元的充放电性能。     

发电机无功补偿控制在电厂中的应用

发电机组的调差率调整一般通过励磁系统的无功补偿辅助控制方式来实现,有些系统称之为LDC,本文以某燃机电厂为例分析无功补偿在机组运行中的具体应用。     

An operating method using prediction of photovoltaic power for a photovoltaic–diesel hybrid power generation system

This paper describes a novel operating method using prediction of photovoltaic (PV) power for a photovoltaic–diesel hybrid power generation system. The system is composed of a PV array, a storage battery, a bidirectional inverter, and a diesel engine generator (DG). The proposed method enables the system to save fuel consumption by using PV energy effectively, reducing charge and discharge energy of the storage battery, and avoiding low‐load operation of the DG. The PV power is simply predicted from a theoretical equation of solar radiation and the observed PV energy for a constant time before the prediction. The fuel consumption of the proposed method is compared with that of other methods by a simulation based on measurement data of the PV power at an actual PV generation system for 1 year. The simulation results indicate that the amount of fuel consumption of the proposed method is smaller than that of any other methods, and is close to that of the ideal operation of the DG. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(3): 8–18, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20116     

发电机无功补偿控制在电厂中的应用

发电机组的调差率调整一般通过励磁系统的无功补偿辅助控制方式来实现,有些系统称之为LDC,本文以某燃机电厂为例分析无功补偿在机组运行中的具体应用。     

Robust control of an isolated hybrid wind-diesel power system using Linear Quadratic Gaussian approach

This paper presents the application of the Linear Quadratic Gaussian (LQG) controller for voltage and frequency regulation of an isolated hybrid wind-diesel scheme. The scheme essentially consists of a vertical axis wind turbine driving a self-excited induction generator connected via an asynchronous (AC-DC-AC) link to a synchronous generator driven by a diesel engine. The synchronous generator is equipped with a voltage regulator and a static exciter. The wind generator and the synchronous generator together cater for the local load and power requirement. However, the load bus voltage and frequency are governed by the synchronous generator. The control objective aims to regulate the load voltage and frequency. This is accomplished via controlling the field voltage and rotational speed of the synchronous generator. The complete nonlinear dynamic model of the system has been described and linearized around an operating point. The standard Kalman filter technique has been employed to estimate the full states of the system. The computational burden has been minimized to a great extent by computing the optimal state feedback gains and the Kalman state space model off-line. The proposed controller has the advantages of robustness, fast response and good performance. The hybrid wind diesel energy scheme with the proposed controller has been tested through a step change in both wind speed and load impedance. Simulation results show that accurate tracking performance of the proposed hybrid wind diesel energy system has been achieved.     

一种带线性动态负载的十二相飞轮储能发电机系统

未来多相储能发电机系统具有广阔的发展应用前景,本文在一套十二相/12kW同步发电机硬件系统的基础上进行了带线性动态负载的十二相飞轮储能同步发电机系统的设计与仿真模型研究。系统中的线性动态负载模块由Buck电路构成,励磁功率放大器模块采用全桥电路,励磁控制器模块采用一种新型变参数反馈加前馈的控制方式。为检验设计效果,基于EMTDC软件建立了系统仿真模型,其中电机模型应用Fortran语言对EMTDC软件二次开发获得。仿真结果表明:所有设计模块均能完成基本功能,线性动态负载的输出功率能够按照期望的速率线性增加,励磁控制系统具有较好的控制精度与响应速度;系统模型求解准确、高效。     

Application of STATCOM/BESS for wind power smoothening and hydrogen generation

This paper proposes static synchronous compensator (STATCOM) incorporated with battery energy storage system (STATCOM/BESS) to smooth the line power of wind farm consists of fixed-speed wind generators. Constant output power reference is not a good choice because there may be some cases where wind speed is very low and then sufficient power cannot be obtained. In that case, energy storage device can solve the problem but large energy capacity may be needed. This paper proposes exponential moving average (EMA) to generate the reference output power, and thus the energy capacity of BESS unit can be small. Another salient feature of this study is the generation of hydrogen by using wind energy. At the wind farm terminal, two topologies of hydrogen generators are considered to be connected and their merits and demerits are analyzed. Finally, by taking the advantage of STATCOM/BESS, simple hydrogen generator topology composed of rectifier and electrolyzer is proposed. Detailed modeling and control strategy of hydrogen generator and STATCOM/BESS topologies are discussed and a cooperative control is developed. The effectiveness of the proposed system is verified by the simulation analysis using PSCAD/EMTDC.