单相固态变压器逆变级的建模与控制

为了实现固态变压器逆变级在不同调制方式的高性能控制要求,采用开关周期平均法和小信号扰动法,建立了单相固态变压器逆变级在双极性调制和单极性调制方式下的连续数学模型,并分别推导了内环电流对占空比的传递函数以及外环电压对电流的传递函数。明确了其数学模型和传递函数在单极性和双极性调制方式下是不一致的,避免了采用同一个数学模型所导致的控制性能不佳等问题。依据串级系统原理,设计了外环电压子系统和内环电感电流子系统,并提出了具体PI控制器参数设计方法。实验结果表明,建立的系统模型正确,且逆变级输出电压稳态精度高,响应速度快,电压总谐波畸变率低,表明控制策略设计合理。

Modeling and Control for inverter stage of Single-phase Solid State Transformer

In order to realize high performance for inverter stage of solid state transformer, the small-signal dynamic models of single-phase inverter stage under bipolar and unipolar PWM modulation are built up based on the switching cycle average method and the small signal perturbation method. Consequently, the current to duty cycle transfer function and voltage to current transfer function are deduced respectively. It can be seen that the models and transfer functions are of difference under different modulation method. In order to achieve high control performance, it should be adopted different models when controller are designed. According to the cascade system principle, voltage subsystem and current subsystem are designed and parameter design methods of PI controller are proposed respectively. It has been shown by experiment results that the models established in the paper are corrective. The output voltage of inverter stage has small stable error, high dynamic response and low total harmonic distortion, which means PI regulator and control strategy are practicable and reasonable.