基于背靠背双PWM变流器的飞轮储能系统并网控制方法研究

Research on Grid-Connected Control Method for FESS Based on Back-to-Back Converter

采用带LCL滤波器的背靠背双PWM变流器作为飞轮电机与电网进行能量交换的接口,提出一种飞轮储能系统并网控制方法。该方法由电网侧变流器控制和电机侧变流器控制两部分组成,并经过充电、预并网和并网运行三个阶段。在充电和预并网阶段,电网侧变流器采用不控整流方式,电机侧变流器先后采用速度外环和电压外环控制方式;在并网运行阶段,电网侧变流器控制采用基于电网侧电流外环、变流器侧电流内环的直接功率控制策略,控制并网有功功率的大小及流向;电机侧变流器控制采用直流母线电压外环、电流内环的双闭环控制策略,维持直流母线电压恒定。采用零极点对消降阶法及对称优化函数等效法分别设计电机侧内外环控制器参数。进行了飞轮储能系统的充电、预并网和并网运行实验。实验结果验证了所提飞轮储能系统并网控制方法的可行性。

A dual-PWM （pulse width modulation） converter with a LCL filter is adopted as an energy exchange interface between flywheel motor and power system. Then a grid-connected control method for FESS is proposed. It is composed of grid-side converter control loop and motor-side converter control loop. The control process includes charge, pre-grid-connected and grid-connected stages. At charge and pre-grid-connected stages, only the six uncontrolled diodes work in the grid-side converter. While the motor-side converter adopts an outer speed loop at charge stage, and adopts an outer DC-bus voltage loop at pre-grid-connected stage. At grid-connected stage, the control of grid-side converter adopts the direct power control strategy based on a grid-side current loop cascaded with an inner converter-side current loop, and thus determines the magnitude and flow direction of grid- connected active power; the control of motor-side converter is based on an outer DC-bus voltage loop cascaded with an internal current loop, and maintains the DC-bus voltage. The parameters of motor- side current controller and DC-bus voltage controller are designed using the zero-pole offset order- reduction method and symmetric optimum function equivalency method respectively. Experiments at charge, pre-grid-connected and grid-connected stages have been conducted. Experimental results validate the feasibility of the proposed method.