五电平MMC-UPQC的无源控制

Passivity Based Control of Five-Level MMC-UPQC

分析五电平模块化多电平变换器-统一电能质量调节器(MMC-UPQC)的主电路拓扑和工作原理,建立其在dq0坐标系下的数学模型及EL模型。为加快误差能量收敛,采用阻尼注入方法设计电流内环无源控制器,确保MMC-UPQC的稳定性;通过电压外环PI控制器获得内环期望电流,消除静态误差。所提出的无源控制实现了对有功和无功的解耦控制,使系统具有良好的动静态性能。在负序二倍频坐标变换下采用相间解耦控制抑制环流,减少开关损耗;采用基于Park变换的电压电流补偿量提取方法,无需锁相环,提高补偿精度。最后在Matlab/Simulink搭建五电平MMC-UPQC仿真模型,仿真结果表明能够较准确地补偿不平衡、谐波电压以及无功、谐波电流,证明了无源控制的可行性。

This paper analyzes the power circuit topology and operating principle of five-level modular multilevel converter-unified power quality conditioner（MMC-UPQC）, the mathematical model of dq0 coordinate system and EL model are established. In order to speed up the convergence of error storage function, the method of injecting damping is designed for passivity based controller in current inner loop to ensure the stability of MMC-UPQC. The desired current is obtained by PI controller in voltage outer loop, the static error is eliminated. Active and reactive power decoupling control is achieved through the proposed passivity based control, so the dynamic and static performance of system is ensured. Under the negative sequence double frequency coordinate transformation, inter-phase decoupling control is used to suppress circulating current and reduce the switch losses. The extraction of voltage and current compensation based on Park transformation is adopted, which has no need of phase lock loop, so the compensation precision is improved. At last, the simulation model of five-level is built in Matlab/Simulink. Simulation results show that accurately compensating unbalanced, harmonic voltage and reactive, harmonic current has verified the feasibility of passivity based control.