级联结构SSSC的RTDS小步长建模

针对RTDS小步长模型应用的难点。建立了SSSC的小步长(<2μs)仿真模型,其SSSC采用H桥级联加单相耦合变压器的主电路接线方式,调制方法为可在线计算逆变器触发角的阶梯波调制,控制策略为恒阻抗控制。针对RTDS建模的特点,探讨了建立电压源逆变器小步长仿真模型的几点注意问题,给出了建立H桥级联式SSSC的RTDS模型的具体实现方法。对比分析不同运行工况下RTDS模型与EMTDC/PSCAD4.02模型的仿真结果,验证了所建立的SSSCRTDS模型的正确性。     

基于级联多电平逆变器的静止同步串联补偿器仿真研究

近些年来,阶梯波调制方法在高电压、大容量多电平逆变器中得到了广泛的应用。本文首先介绍了一种在线计算触发角的方法,它只需要进行几个三角函数的计算就可以求出触发角,计算简单快速。然后将其在5H桥级联逆变器中得到了实现,并提出了逆变器H桥触发角的循环控制策略。同步静止补偿器(SSSC)是灵活交流输电控制器的一种,它可以调节系统阻抗,控制系统潮流和提高系统稳定性,具有良好的性能。文中把前面得到的逆变器模型应用到了SSSC中,并提出了相应的SSSC控制策略。最后在EMTDC/PSCAD中对提出的SSSC仿真模型进行了仿真验证。仿真结果表明,无论运行在感性模式还是容性模式,文中提出的SSSC模型都是合理的。     

基于载波移相SPWM级联式变换器输出谐波分析

为了分析不同调制方式及不同级联数目多电平变换器的输出谐波电压分布规律,并为滤波器的设计提供参考,在充分考虑奇偶级联数目、调制移相角度和调制比对输出波形影响的基础上,分别以3,5,6,7,10个H桥级联的谐波输出情况为例,通过大量的仿真,采用对比分析的方法得出了基于载波移相SPWM级联式静止串联同步补偿器(Static Serial Synchro Compensator,SSSC)输出电压谐波的具体分布规律,并给出了等效载波频率的明确定义方法,通过双重Fourier级数理论分析验证了文中的结论。     

无变压器SSSC的模型及控制方式研究

针对静止同步串联补偿器(SSSC)系统应用中配备耦合变压器存在的损耗、体积以及成本等问题,基于级联H桥多电平逆变器的拓扑结构,提出了一种无需耦合变压器的SSSC系统结构。对无变压器SSSC的拓扑结构进行了介绍,在d-q旋转坐标系下建立了SSSC的动态模型,并对恒电压、恒阻抗、恒功率3种控制方式进行了详细的理论推导,提出了一种简单有效的控制策略。最后针对恒电压控制方式搭建了Matlab/Simulink仿真模型,实验结果证明了该模型及控制策略的可行性。     

级联H桥型电力电子变压器平均值模型

针对电力电子变压器仿真效率较低和死区效应越来越显著的问题,基于级联H桥型双有源桥结构电力电子变压器,提出一种考虑死区效应的平均值模型。首先,计及寄生参数将双有源桥单元简化为一阶RL电路,分析各个死区工况下电压电流特性,求解电流的平均化解析表达式,通过等效电流源代替全桥及高频变压器实现对双有源桥单元的平均值建模。其次,基于状态空间平均法,通过占空比将H桥整流单元各工况整合为一个统一的模型,进而使用受控源代替H桥整流单元与交流电网、双有源桥的接口电路。最后,建立输入侧串联输出侧并联型的级联H桥型电力电子变压器平均值模型并给出计算流程。在PSCAD/EMTDC仿真软件上分别搭建电力电子变压器详细模型与平均值模型,仿真结果表明所提出的模型具有较高的精度和运行效率。     

基于CPS-SPWM的级联H桥多电平逆变器控制方法

级联H桥多电平逆变器适用于各种高电压、大电流的场合;载波移相正弦脉宽调制(CPS-SPWM)技术易于实现,等效载波频率高,已成为级联多电平逆变器使用最广泛的调制方法。采用了一种可节省硬件资源的改进型载波移相调制方式,在对其调制原理进行详细分析的基础上,利用PSCAD/EMTDC软件搭建级联H桥多电平逆变器的软件仿真模型,结合基于IPM模块实现的物理实验系统,研究了载波频率对逆变器输出电压谐波特性的影响。仿真及实验结果均表明改进型CPS-SPWM技术能够使逆变器的输出电压波形趋近正弦波,并降低其畸变率。     

混合级联H桥十三电平逆变器的混合调制

对于混合级联H桥逆变器而言,目前受到广泛研究的拓扑主要是电压比为1:2的混合级联H桥七电平逆变器,但该混合级联H桥七电平逆变器存在电流倒灌问题。为此,提出了一种电压比为1:1:2:2的混合级联H桥十三电平逆变器和一种改进的混合调制方法。仿真和实验结果表明:在改进混合调制方法的控制下,混合级联H桥十三电平逆变器不仅可以消除电流倒灌问题,而且可保证高压单元工作在基波频率并具有较高的输出电压质量。     

改进的新型Ⅱ型不对称CHB逆变器调制策略

级联H桥多电平逆变器具有高质量的输出特性及实用性,然而传统的不对称级联H桥多电平逆变器的调制策略会产生电流倒灌及能量反馈的问题。针对该问题,提出了一种单极倍频的Ⅱ型不对称级联H桥逆变器的调制策略,对该调制频率下所得脉冲进行分区间的逻辑运算与组合,不仅可以解决传统调制策略中电流倒灌和能量反馈问题,而且最大开关频率比传统调制策略降低了1/2,同时改善了逆变器输出电压波形的谐波特性,保证了输出电能质量和效率。所搭建的仿真模型和实验结果均证实了该调制策略的可行性和有效性。     

静止同步串联补偿器的恒阻抗模型及其双闭环控制策略

考虑到静止同步串联补偿器(static synchronous series compensator,SSSC)输出电压相位与线路电流相位的垂直关系、逆变器的损耗以及直流侧电容电压的波动过程,在两相同步旋转d-q坐标系下建立SSSC的恒阻抗模型。在分析此模型的基础上提出SSSC的双闭环控制策略,即电容电压控制和线路阻抗控制。在电容电压控制环中,选取SSSC为控制对象,电容电压为控制目标;在阻抗控制环中,选取含SSSC的输电线路为控制对象,线路阻抗为控制目标。在Matlab/Simulink动态仿真环境中搭建SSSC的恒阻抗模型及控制系统的仿真模型,并对线路阻抗的调节过程和电容电压的变化过程进行仿真,仿真结果证明了所建立模型和所提出控制策略的有效性和实用性。     

电压调整单元双有源桥级联系统的阻抗匹配优化设计

具有电压调整单元(VAU)的双有源桥(DAB)直流变换器是解决宽电压输入时电感电流应力问题的方案之一,然而VAU-DAB存在级联稳定性问题.该文分别推导前级VAU输出阻抗模型和后级DAB输入阻抗模型,在复频域下根据禁区概念阻抗稳定性判据分析级联系统阻抗比,研究阻抗特性对级联系统稳定性的影响.由于VAU输出阻抗谐振峰值与DAB输入阻抗存在交叉点,使级联系统由于阻抗不匹配而导致系统电压振荡失稳.在此基础上,该文基于阻抗匹配准则,提出一种基于超前-滞后的阻抗优化调节器用以抑制VAU输出阻抗谐振尖峰,使级联系统阻抗比满足稳定性判据,提升了系统运行可靠性,并优化了电流应力.最后通过仿真验证了该文提出阻抗优化调节策略的有效性及可行性.     

Novel reactive power controllers for the STATCOM and SSSC

The paper investigates the dynamic operation of both static synchronous compensator (STATCOM) and static synchronous series compensator (SSSC) based on a new model comprising full 48-pulse GTO voltage source converter for combined reactive power compensation and voltage stabilization of the electric grid network. These key FACTS devices are power electronic GTO converters connected in parallel or series with the power system grid and are controlled by novel decoupled controllers. The complete digital simulation of the STATCOM and SSSC within the power system is performed in the MATLAB/Simulink environment using the power system blockset (PSB). The STATCOM scheme and the electric grid network are modeled by specific electric blocks from the power system blockset while the control system is modeled using Simulink. Two novel controllers for the STATCOM and SSSC are presented in this paper based on a decoupled current control strategy to ensure stable operation of the STATCOM under various load excursions. A novel control scheme for the static synchronous series compensator (SSSC) is also implemented to provide a full controllable series compensating (buck/boost) injected voltage over a specified capacitive and inductive range, independently of the magnitude of the transmission line current. The series reactive compensation scheme with an external dc power supply can also compensate for any voltage drops across resistive component of the transmission line impedance. The novel decoupled controller uses a phase locked loop (PLL) with a novel reduced inherent time delay to improve the transient performance of the SSSC. The performance of both STATCOM and SSSC schemes connected to the 230 kV grid are evaluated. The proposed novel control schemes for the STATCOM and SSSC are fully validated by digital simulation.     

基于功率传递的同期并列装置实现SSSC功能的仿真

本文针对基于功率传递的电网间同期并列装置转换为静止同步串联补偿器的复合系统,建立了并网装置转换为SSSC后的等效模型,根据SSSC既可进行容性补偿又可进行感性补偿的双重补偿的特点,分析了SSSC调节潮流的过程以及接入SSSC前后输电线路电流的变化情况。为减小短路故障情况下短路电流对系统的影响,本文利用SSSC可等效为感性阻抗的特点对不同短路故障电流进行了限制,从而提高了现有设备的综合利用率。在PSCAD/EMTDC中搭建了含SSSC的等效模型,仿真结果表明SSSC可有效调节线路输送的潮流,并验证了当系统发生短路故障时SSSC具有一定的限流功能。     

利用附加节点注入电流法设计静止同步串联补偿器的潮流控制器

从静止同步串联补偿器（SSSC）的原理和特性出发,分析了其稳态特性和数学模型,研究对比了SSSC及其它FACTS装置潮流建模的方法,通过分析节点导纳矩阵和雅可比矩阵的修正,提出了利用附加节点注入电流法建立SSSC潮流模型的方法,并分析了此方法的优点.在电力系统分析综合程序PSASP中,利用用户接口程序实现了SSSC的潮流建模,结合开发的潮流控制模块,解决了含SSSC装置的大系统仿真问题.在EPRI-7节点系统的分析计算中,验证了理论分析的正确性和SSSC潮流模型的控制作用.并与相同控制条件下TCSC特性作了比较,结果表明：SSSC能够以更小的输出功率实现相同的控制效果,而且在小功率情况下,SSSC的优势更加明显.     

Optimal control schemes for SSSC for dynamic series compensation

This paper presents two novel control schemes for static synchronous series compensator (SSSC) for dynamic series compensation and voltage regulation. The SSSC model comprises a harmonic neutralized multilevel 48 pulse voltage source converter. This paper investigates two novel control schemes for optimal series compensation, which are indirect control (constant reactance control) and direct control (constant voltage control) using pulse width modulation (PWM) switching techniques. The proposed model of SSSC within the power system is performed in Matlab/Simulink using the power system blockset. The performance of the SSSC schemes connected to the 230 kV grid is evaluated in both capacitive and inductive modes of operation under load excursions. The operation of the proposed controllers is also tested in a weak power in order to compare their performance for securing SSSC stability in response to system contingencies.     

静止同步串联补偿器的原理及其补偿模式研究

详细分析了SSSC的工作原理及其对电力系统的作用。只考虑基波分量,推导出含有SSSC装置输电系统的有功功率和无功功率的表达式,定量的分析了SSSC装置对输电系统潮流的调节作用。介绍了SSSC装置的两种补偿模式：恒阻抗补偿模式和恒电压补偿模式,并分别给出了在两种补偿模式下系统的控制框图。     

静止同步串联补偿器控制方式及特性研究

基于dq同步旋转坐标系建立静止同步串联补偿器(static synchronous series compensator,SSSC)的数学模型,采用电压外环电流内环的双环控制实现对SSSC的控制。基于IEEE次同步谐振第1标准测试系统,考虑仅由固定电容提供串补及其中部分由SSSC提供串补的2种补偿方案,利用测试信号法计算2种补偿方案下发电机组的次同步阻尼特性,并进一步分析SSSC在次同步频率范围内的阻抗特性。研究表明：次同步频率下串有SSSC支路的阻抗特性与串有等值电容支路的阻抗特性相似,但SSSC所呈现的容抗小于固定电容的容抗,且SSSC还呈现较大的电阻分量。因此,串有SSSC的系统次同步谐振点将偏移,且谐振点附近的负阻尼大大减小,这将有利于缓解次同步谐振(subsynch- ronous resonance,SSR)。     

Advanced modeling of the multicontrol functional static synchronous series compensator (SSSC) in Newton power flow

The static synchronous series compensator (SSSC) is one of the recently developed flexible AC transmission system (FACTS) controllers. The SSSC coupled with a transformer is connected in series with a transmission line. This paper describes a multicontrol functional model of the SSSC for power flow analysis, which can be used for steady state control of one of the following parameters: (1) the active power flow on the transmission line; (2) the reactive power flow on the transmission line; (3) the voltage at the bus; and (4) the impedance (precisely reactance) of the transmission line. Furthermore, the model can also take into account the voltage and current constraints of the SSSC. The detailed implementation of such a multicontrol functional model in Newton power flow algorithm is presented. A special consideration of the initialization of the variables of the SSSC in power flow analysis is also proposed. Numerical examples on the IEEE 30-bus system, IEEE 118-bus system, and IEEE 300-bus system are used to illustrate the feasibility of the SSSC model and performance of the Newton power flow algorithm.     

SSSC对阻抗继电器动作特性的影响分析

将SSSC安装于线路中点,根据SSSC在故障范围之内和之外2种情况,对阻抗继电器的测量阻抗进行了分析,且通过SSSC的不同注入电压和补偿方式,以及过渡电阻的变化,仿真了阻抗继电器的动作特性。结果表明,SSSC在故障范围之内时对阻抗继电器的测量阻抗产生了很大的影响,应该采取措施减小SSSC对阻抗继电器的影响;另外,过渡电阻的影响同样不可忽略。     

Impacts of the SSSC control modes on small-signal and transient stability of a power system

In order to accomplish specific compensation objectives a static synchronous series compensator (SSSC) may be controlled by several ways. The most common control modes of the SSSC are: (1) constant voltage mode, (2) constant impedance emulation mode, and (3) constant power control mode. Moreover, to improve the dynamic performance of the system, a SSSC may be equipped with supplementary controllers, such as damping controls. Therefore, this paper investigates the impacts of different SSSC control modes on small-signal and transient stability of a power system. The performance of different input signals to the power oscillation damping (POD) controller is also assessed. The stability analysis and the design of the SSSC controllers are based on modal analysis, non-linear simulations, pole placement technique, and time and frequency response techniques. The results obtained allow to conclude that the usage of the SSSC in the constant impedance emulation mode is the most beneficial strategy to improve both the small-signal and transient stability.     

Power flow control for transmission networks with implicit modeling of static synchronous series compensator

This paper presents an implicit modeling of Static Synchronous Series Compensator (SSSC) in Newton–Raphson load flow method. The algorithm of load flow is based on the revised current injection formulation. The developed model of SSSC is depended on the current injection approach. In this model, the voltage source representation of SSSC is transformed to current source, and then this current is injected at the sending and auxiliary buses. These injected currents at the terminals of SSSC are a function of the required line flow and voltage of buses. These currents can be included easily to the original mismatches at the terminal buses of SSSC. The developed model can be used to control active and reactive line flow together or individually. The implicit modeling of SSSC device decreases the complexity of load flow code, the modification of Jacobian matrix is avoided, the change only will be in the mismatches vector. Finally, this modeling solves the problem that happens when the SSSC is only connected between two areas. Numerical examples on the WSCC 9-bus, IEEE 30-bus system, and IEEE 118-bus system are used to illustrate the feasibility of the developed SSSC model and performance of the Newton–Raphson current injection load flow algorithm.