基于模态分析与相对增益矩阵的多STATCOM交互影响分析与仿真

STATCOM以快速无功控制稳定电压,但缺乏协调配合会产生交互影响。采用模态分析与相对增益矩阵(relative gain array,RGA)结合的方法进行交互影响分析,借助精确反馈线性化改进内层电流控制。建立多STATCOM系统的状态空间表达式,通过模态分析确定系统出现负阻尼振荡模式的控制器参数;结合状态空间表达式系数矩阵,求解相对增益矩阵,研究输入信号及电气距离与交互影响的关联机理;结果表明STATCOM控制器比例增益设置会引入新的局部振荡模式,引起低频功率振荡;而参考电压与电气耦合程度是负交互影响产生的重要因素。针对传统内环电流控制,利用非线性控制理论对其改进,设计输入状态反馈线性化控制器;借助线性二次型控制理论确定状态反馈矩阵,推导最优控制律,实现受控状态对期望状态的最优逼近;仿真结果表明非线性控制器能有效改善参考信号阶跃引起的功率波动,显著提高系统阻尼。

Interactions and Simulation of Multiple STATCOMs Based on Modal Analysis and Relative Gain Array

Voltage stability can be ensured by fast var control of STATCOM,whereas uncoordinated control will contribute to negative interactions.Modal analysis and relative gain array (RGA) are combined to analyze the negative interactions,and exact linearization via feedback is employed to modify the inner current control.The state-space model of the system with multiple STATCOMs is constructed and modal analysis adopted to determine the control parameters which leads to negative damped oscillation mode.RGA is deduced by the matrices form state equations and the relationship between interactions and input signal as well as electrical distance is presented.The results show that new local oscillation mode could exist with uncoordinated proportional gain parameters of STATCOM controller,which may result in low frequency power oscillations.Besides,voltage references and electric coupling are also the significant factors of negative interactions.Acccording to traditional inner current control,nonlinear control theory is employed to modify the control system.With input-state linearization via feedback a modified controller is designed.The state feedback matrix is determined by the linear quadratic control theory to deduce the optimal control strategy,which can achieve the optimal approximation of a controlled state to a desired state.The simulation results show that the nonlinear controller can effectively improved power fluctuation caused by the step of reference signal and significantly increases system damping.