【作者】 胡应宏；

【导师】 纪延超；

【作者基本信息】 哈尔滨工业大学 ， 电力系统及其自动化， 2013， 博士

【摘要】 静止同步无功补偿器(Static Synchronous Compensator，STATCOM)，作为一种重要的无功补偿装置，对电力系统的安全稳定运行发挥着重要作用，是目前国内外研究的热点。级联H桥多电平STATCOM，通过多个H桥模块在输出侧串联叠加，提高了电压等级，增大了设备的容量，具有较高的等效开关频率，在静止无功补偿的领域中具有重要地位。本文主要针对以级联H桥为核心的STATCOM的建模与控制方法、阀组内直流侧电压平衡、零序电压注入控制以及不平衡负载的补偿等问题进行了深入研究，具体研究内容包括以下几个方面。为了对无功功率进行的准确补偿，需要对STATCOM进行建模和精确控制。但是由于级联H桥直流侧电压的波动，使得输出电压畸变，造成STATCOM具有很强的非线性，准确建模困难。针对该问题，本文提出了降阶的Hamiltonian模型，通过降阶将偏微分方程简化为常微分方程，避免了求解高阶偏微分方程方法复杂、不易工程实现的困难，使得非线性控制器设计变得简单。然后基于降阶Hamiltonian模型，实现了系统互联与阻尼分配的无源性控制，通过系统互联的能量成型和阻尼注入，使得STATCOM的动、静态特性均得到了改善。级联H桥的直流侧电容相互独立，会出现直流侧电压不平衡，是级联H桥STATCOM需要解决的重要问题之一。针对该问题提出了交换载波相位的平衡控制的解决方法，根据各个直流侧电压变化趋势，以载波相位差造成的直流侧不平衡来补偿开关损耗等造成的不平衡，该方法适合于稳态直流侧电压不平衡度小的情况。在动态过程以及故障情况下，直流侧需要较快、较强的平衡控制能力。针对该需求，通过分析级联H桥STATCOM瞬时电流和开关状态对直流侧电压的影响，提出了交换冗余开关状态的直流侧电压平衡控制方法,将阀组内直流侧电压高的模块的开关状态与直流侧电压降低的开关状态进行交换，从而实现直流侧电压的平衡。STATCOM的负序阻抗小，当系统电压存在不对称时，STATCOM需要输出相同的负序电压分量来抵消系统的负序电压分量。由于级联H桥多电平STATCOM直流侧分开，各相的负序电压与正序电流相互作用，导致有功功率在级联H桥STATCOM三相阀组中的不平衡，造成了阀组之间的直流侧电压不平衡现象。为此本文提出了基于直流侧能量的零序电压注入的一种解决方法，通过注入适当的零序电压，建立有功功率在三相阀组之间相互交换的一种机制，解决了阀组之间的直流侧电压不平衡的问题。然后分析了注入零序电压补偿不平衡电流的操作范围，星接阀组级联H桥STATCOM能够补偿不平衡负载，但是需要占用了较大的设备容量。分析了不平衡负载的平衡化方法，提出了基于平衡分量法的无功补偿导纳和补偿电流的计算方法。通过将任何中性点不接地的三相负载分解为平衡负载和单一线间负载之和，将补偿导纳的计算分为平衡负载功率因数补偿、单一线间负载功率因数补偿以及单一线间阻性负载平衡化补偿。在平衡分量法基础上提出了阀组角接的级联H桥STATCOM不平衡负载的参考电流计算方法，使级联H桥STATCOM能很好地平衡不平衡负载，仿真和实验证明了所提出的理论分析方法具有算法简单、容易实现的优点，避免了星接阀组补偿不平衡负载占用较大设备容量的缺点。通过修正简化的一维空间矢量调制算法，均匀了H桥模块左右桥臂的开关频率，减小了开关器件的开关应力；然后对级联H桥STATCOM实验平台的进行了软硬件设计，介绍了级联H桥STATCOM的直流侧电容的选择以及静态均压电路的选取，完成了以DSP和FPGA为核心的控制系统硬件电路的设计；最后给出现场运行的测试结果，并对实验结果进行了分析。更多还原

【Abstract】 As a novel static var compensator, STATCOM (static synchronouscompensator), is very important for the security of the power system.It has becomeresearch focus at home and abroad at present. It is important for realizing largecapacity and high voltage reactive power compensation by using cascadedH-bridge multilevel topology. Cascaded H-bridge multilevel STATCOM iscombined by many H-bridge module connected in series.In this way, high voltageis reached, the capacity and switching frequence are increased Modeling andcontrol of cascaded H-bridge STATCOM, DC side capacitor voltage betweenclusters, zero sequence voltage injection method and unbalanced loadcompensation are detailed analyzed in this paper. The detailed contents are asfollows:STATCOM should be modeled and controlled exactly, in order to compensateVar properly.Cascaded H-bridge STATCOM is a strong nonlinear system, becauseof DC-side capacitor voltage fluctuation cause output voltage distortion.According to the modeling of Cascaded H-Bridge STATCOM, a reduced orderHamiltonian model is proposed based on the average model that avoids thesolution difficulty of partial differential equation during the design ofinterconnection and damping assignment passivity-based control (IDA-PBC).Thus open system interconnection and damping assignment passivity-basedcontrol are realized based on the reduced order Hamiltonian model. The dynamiccharacteristic and stability has all been improved by energy shaping and dampinjecting.DC-side capacitor voltage unbalance of Cascaded H-Bridge STATCOM is themost important issue to be dealt with, and the needed DC side balance abilities arevarious in different situations. Carrier phase exchanging is adopted due to theabove problems, and this control method is fit for lower unbalancing situation.Since a more fast control capacity is needed under large fluctuation and fault,according to the impacts on DC-side capacitor voltage by current analysis andswitching states of cascaded H-Bridge STATCOM, a novel DC-side capacitorvoltage control strategy based on voltage redundant states is presented in thispaper.DC side capacitor voltage unbalance between clusters and its reasons areanalyzed. According to the DC side capacitor unbalance of each cluster caused bysystem unbalanced voltage, a zero sequence voltage injecting control method ofcascaded STATCOM based on DC side energy is proposed in this paper. Then, the control ranges in unbalanced system is proposed, where large equipment capacityis needed.Three-phase unbalanced load and balancing method is analyzed in this paper.The novel calculation methods of both reactive power compensation admittanceand the compensation current of STATCOM based on balance components areproposed. Any neutral non-grounded three-phase load can be decomposed intobalanced load and a single line load. The load compensation admittancecalculation can be divided into three parts, the power factor compensation for thebalance load and the single line load together with the balance compensation forthe single line resistive load. Then, the ideal Steinmetz compensation networkalgorithm is amended under the condition of asymmetric voltage. Above all, anoptimization method of reference current of cascaded H-Bridge STATCOM isproposed in this paper, which makes cascaded H-Bridge STATCOM a better use inunbalanced system. Simulation and experimental results verified the advantages ofsimple algorithm and easy realization of the proposed method.Hardware and software are designed for cascaded H-Bridge STATCOM at last,including the choice of DC-side capacitor and steady voltage-balancing circuit.The hardware design of control system based on DSP and FPGA was finished. Asimplified1-D space vector modulation algorithm is presented based on irregularand asymmetrical sampling technique, which could even the switching frequencyof the device. Finally the testing results of field operation are given, and theexperimental results are analyzed and verified.更多还原