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级联H桥型静止同步无功补偿器控制方法的研究
Control Technique of Cascaded H Bridge Static Synchronous Reactive Compensator
【作者】 罗丹；
【导师】 纪延超；
【作者基本信息】 哈尔滨工业大学 ， 电气工程， 2010， 硕士
【摘要】 近年来,随着电网容量的增加,人们对电力供电品质要求也不断提高,柔性交流输电系统(FACTS)作为一项能有效改善电能质量的新技术,得到飞速发展。静止同步补偿器(STATCOM)由于其先进的控制性能和良好的补偿效果,已经成为FACTS装置研制的热点和无功补偿的发展趋势。本文研究的对象是级联H桥型STATCOM,它避免了变压器多重化结构造成的价格昂贵、体积庞大、损耗大以及变压器的铁磁非线性等问题,同时与其他多电平逆变器相比还具有结构简单,所需器件少,易于实现模块化设计和封装等一系列优点。首先对STATCOM的无功补偿原理进行深入的分析,并对不同接入方式下级联STATCOM的阀组结构进行特性分析和比较,通过MATLAB仿真进行了验证。文中在对载波调制方法的原理进行分析基础上,通过数学分析和仿真验证分别对三种调制方法进行对比分析。将载波相移PWM的两种调制方法应用到级联STATCOM中,对其电容电压波动特性进行研究。得出双极性PS-PWM比单极倍频PS-PWM产生的电容电压波形更复杂,谐波含量更多,各个桥电容电压不平衡程度更大。级联H桥型STATCOM最大特点就是每个单相逆变桥的直流侧均具有独立的电容,该结构给级联STATCOM带来显著优点的同时也带来了问题。所以对电容电压的波动情况和影响电容电压平衡的因素进行了研究,并提出了一种新的基于电压冗余状态的直流侧电容电容平衡控制方法。该方法将电容电压平衡控制与STATCOM系统控制独立出来,算法简单,扩展和实现方便,而且不影响输出电压波形,不增加开关频率。仿真分析证实了该方法的正确性和有效性。在仿真的基础上,建立了一台以DSP为平台的实验样机。主要研究了主电路、驱动电路以及DSP的软硬件设计和实现。最后在样机上进行了载波相移两种调制方法的对比实验和STATCOM无功补偿能力的验证实验,实验结果证明了理论及仿真分析的正确性。
【Abstract】 With the constant increase of electrical network capacity and raised requirement of electric power quality, flexible AC transmission system (FACTS) as an efficient technique to improve electric power quality has been rapidly developed. Static synchronous compensator (STATCOM) has currently become a hot research topic of FACTS equipments and a development trend of reactive power compensation because of its advanced control characteristic and good compensation performance.This paper analyzes the cascaded H-bridge STATCOM which avoids the high cost, huge volume, low loss and transformer ferromagnetic nonlinear caused by multi-pulse inverters and has series advantages of simple structure, less devices, easy modular design realization and packaging compared with other multilevel inverters. H bridge STATCOM topology and its operation characteristics with star and angle access mode is analyzed in this paper based on the reactive power compensation principle of STATCOM, and this is verified by MATLAB simulation.Based on the principle analysis of carrier modulation method, three kinds of modulation methods are compared and analyzed through mathematical analysis and simulation verification in this paper. The two carrier phase shifted PWM (CPS-PWM) modulation methods are applied in the cascade H-bridge STATCOM and the capacitor voltage fluctuation characteristics are studied. It can be clearly seen that bipolar CPS-PWM modulation could achieve more complex voltage waveform, larger harmonic components and unbalance of each bridge capacitor voltage than those achieved by unipolar CPS-PWM modulation.Cascade H-bridge STATCOM has the characteristic of independent DC side capacitor on each phase bridge which brings both significant advantages and some problems. So analysis the capacitor voltage fluctuation situation and the corresponding influence factors, then proposes a novel DC side capacitor voltage balancing control method based on voltage redundant states. This new method separates the capacitor voltage balance control from STATCOM control system, and this algorithm is simple, convenient, and does not affect the output voltage waveform and increase switching frequency. Simulation analysis verified the method.An experiment prototype of STATCOM controlled by DSP is designed on the basis of simulation. Design of main circuit, drive circuit and the software and hardware realization of DSP are included. Finally, experiments of the comparison of the two CPS-PWM modulation methods on cascaded H-bridge STATCOM and its reactive power compensation ability are tested on the prototype. Experiment results proved the validity and utility of this new method.