基于占空比预测与零极点结合的LCL型逆变器延时补偿方法

LCL型并网逆变器数字控制中延时环节对系统稳定性的影响不可忽略。分析发现,网侧电流数字单环鲁棒性不足,需要采用额外的有源阻尼方法增强阻尼,但传统的数字电容电流反馈有源阻尼方法带来了内环数字延时,使电容电流内环等效虚拟电阻不再保持纯电阻特性,增大了系统保持稳定的难度,因此提出一种预测占空比结合零极点补偿控制延时的方法。通过预测控制算法得到占空比和增加零极点,有效地补偿了系统数字延时,消除了采样计算等产生的一拍延时和零阶保持器产生的半拍延时,使系统在有源阻尼方法下能有效地起到增强阻尼的作用。算法设计简单,系统稳定性加强。仿真和实验验证了所提方法的有效性和可行性。

Delay Compensation Method of LCL-typed Inverter Based on Combination of Duty Cycle Prediction with Zero-pole

The influence of control delay in digital control on system stability is inevitable for LCL-typed grid inverter. The deficiency of robustness in the digital grid-current single-loop control is discovered, and an active damping method is needed to enhance the damping. But the inner loop control delay is brought about by the digital capacitive current feedback, which makes the equivalent virtual impedance of capacitive current feedback no longer retain its pure resistance characteristic while increasing the difficulty in stabilizing the system. So a method of combining duty cycle prediction with increased zero-pole to compensate for control delay is proposed. The control delay is effectively compensated by the duty cycle obtained by predictive control algorithm with the increased zero-pole, which eliminates the one beat and half of beat control delay generated by calculation, sampling and zero-order holder, respectively. And the active damping method is enabled to effectively enhance damping. The design of the method is simple and the stability of the system is enhanced. The effectiveness and feasibility of the proposed method are proved by simulation and experiment.