两级式逆变器母线电压二次纹波分析及抑制

Secondary Ripple Analysis and Suppression of the Bus Voltage in Two-stage Inverter

针对前级采用Boost电路、后级采用单相全桥逆变电路的两级式逆变器,研究基于传统电压外环电流内环控制改进的方法,以解决抑制中间母线电压低频纹波的问题。由于输入功率是直流量,输出的瞬时功率中除了有直流分量外,还含有2倍于工频的脉动分量,导致输入输出功率不平衡,从而使中间母线电压含有二次低频电压纹波。该低频电压纹波会引起母线电容发热从而危及母线电容的运行寿命,会导致逆变输出电压波形出现削顶而产生畸变,还会影响系统的动态性能。为了解决母线电压低频纹波所带来的问题,提出了一种将输出功率前馈到前级直流变换器以实现母线电压低频纹波抑制的方法。仿真和实验结果验证了该控制方法的正确性和有效性,母线电压低频纹波得到很好的抑制。

For a two-stage inverter with a Boost converter at the front-end and a full-bridge inverter at the back-end, an improved control method based on the traditional controller with a voltage outer loop and a current inner loop is proposed to suppress the low-frequency ripples on the middle-bus. Considering that the power input is a DC power, while the instantaneous output power contains not only DC components but also pulse components whose frequencies are 2 times as high as the power frequency, the input and output powers are imbalanced, which makes the voltage on the middle bus contain secondary low-frequency voltage ripples. These ripples will heat the bus capacitor, thereby endangering the operation life of the bus capacitor and leading to the clipping and distortion of the inverter, s output voltage; moreover, they will also affect the dynamic performance of the system. To solve the above problem, a method is proposed to realize the low-frequency ripple suppression of the bus voltage by applying the feedforward of the output power to the front-stage DC converter. Simulation and experimental results verified the validity and effectiveness of the proposed control method, by which the suppression effect of low-frequency ripples of bus voltage was obvious.