微电网电压不平衡的分层补偿控制策略

微电网是消纳分布式电源的有效手段之一,然而也带来了其自身的电压控制的难题,特别是公共连接点处的三相电压不平衡问题比较突出,为此提出一种微电网公共连接点电压双极补偿控制方法,上层控制发送与电压的正序和负序分量有关的控制信号,采用双电流环的控制器可得到电流给定值;下层控制通过双电流环控制器实施.针对PCC点三相电压不平衡的问题,应用dq旋转坐标分解原理,提出一种基于改进解耦的双同步坐标系锁相环(IDDSRF-PLL)的控制方法,能够实现正负序分量的独立控制,并通过控制给定模型的正负序电流和电压不平衡补偿控制器得到三相平衡电压,使得公共连接点母线电压的二倍频波动部分为零,从而实现了对三相电压不平衡的补偿控制.利用MATLAB/Simulink对微电网接入电网进行建模仿真,结果表明,分层控制方法能够较好的实现对微电网的电压控制.

Hierarchical control strategy for voltage unbalance compensation in micro-grid

Micro-grid is one of the effective means to absorb distributed generations; however, this also results in issues of voltage instability and difficulty in operation controlling of the micro-grid, especially the unbalanced three-phase voltage at the point of common coupling (PCC). This paper proposes a control for micro-grid voltage bipolar compensation at the point of common coupling, the upper level sends the control signals, these control signals relate to the positive-and negative-sequence components of the unbalanced voltage, dual the current control loop current setpoint is obtained. The lower control loop controller through dual current implementation, in view of the PCC point of three-phase voltage imbalance problem, application of dq rotating coordinate decomposition principle, proposed dual synchronous coordinate system based on improved decoupling phase-locked loop (IDDSRF-PLL) to independently control the positive and negative sequence voltage component. Furthermore, the three-phase balance voltage could be achieved by controlling the model of positive and negative sequence currents, and using the unbalance voltage compensation controller, bus voltage doubler fluctuation at point of common coupling is zero, thus realizing the three-phase control voltage unbalance compensation. MATLAB/Simulink software is used to set up the simulation model of connecting micro-grid to the main grid. The simulation results show that the hierarchical control method is effective to implement voltage control of micro-grid.