基于相电压反馈的三电平逆变器死区补偿

Three-level Inverter Dead-time Compensation Based on Phase Voltage Feedback

为防止逆变器上下桥臂直通,通常需要在开关管驱动信号中加入死区时间,但死区时间可能导致输出电压和电流畸变。针对二极管中点箝位型NPC(neutral-point clamped)三电平逆变器的死区补偿问题,提出了一种基于相电压反馈在线计算误差电压的死区补偿策略。该策略根据反馈相电压,在dq同步旋转坐标系下对误差电压进行实时计算。同时,针对电流极性判断中传统滤波器所造成的电流相位偏移问题,采用卡尔曼滤波对转换到dq同步旋转坐标系中的三相输出电流进行滤波,并将滤波后的电流重构到三相静止坐标系中,实现无相位偏移地判断电流极性。仿真结果表明,该方法可以较准确地判断电流极性,并能够自适应地调节补偿电压,有效地减小了输出电压的谐波含量。

To prevent the direct-through of the upper and lower arms of an inverter,it is usually necessary to add dead-time to the driving signal of switching tubes.However,the dead-time may lead to the distortion of output voltage and current.To solve the dead-time compensation problem of a diode neutral-point clamped(NPC)three-level inverter,a deadtime compensation strategy is proposed based on the voltage errors obtained using the online phase voltage feedback calculation.Under the d-q synchronous rotating coordinate system,the error voltage is calculated in real time according to phase voltage feedback.At the same time,aimed at the current phase shift problem caused by the traditional filter used in the current polarity judgment,a Kalman filter is adopted to process the three-phase output current under the d-q synchronous rotating coordinate system.Afterwards,the filtered current is reconstructed into a three-phase stationary coordinate system,thus determining the current polarity without phase shift.Simulation results show that the proposed method can accurately judge the current polarity and adjust the compensation voltage adaptively,thereby effectively reducing the harmonic content of the output voltage.