LCL型并网逆变器并网电流复合控制研究

RESEARCH ON COMPOUND CURRENT CONTROL FOR GRID-CONNECTED INVERTER WITH LCL FILTER

LCL型并网逆变器采用直接并网电流单闭环控制策略,系统存在稳定性差和控制精确度差等问题。针对该情况,以并网电流瞬时值作为外环反馈量,以LCL滤波器电容电流瞬时值作为内环反馈量的双环控制策略。内环采用比例调节增大阻尼以消除LCL输出滤波器的振荡属性,增强系统的稳定性,外环复合PI控制和重复控制增强系统的动静态特性。详细分析控制方法的工作机理,并给出控制器的设计方法。最后在一台以DSP2812为核心控制器的1.5 k VA并网逆变器装置上进行实验验证。实验结果表明,该控制策略既可保证系统的稳定性,又能提高并网电流的性能。

Grid connected inverter with an LCL filter has many benefits in contrast with L or LC filter. But LCL filter is a third order system which means it is easy to resonate. In order to damp resonance of LCL filter and improve the stability of the system, a compound current control method with grid current feedback and filter capacitor current feedback was proposed. This paper also discussed the limitation of the traditional control method for grid-connected inverters with an LCL filter. On this basis, the feasibility analysis on the application of the compound current control method with both PI control and repetitive control was carried out. All the theoretical analyses presented in the paper were verified by experimental results on a single phase 1.5 kVA prototype of grid-connected inverters with an LCL filter.