有源滤波器中逆变器的死区效应与补偿方法

为解决死区存在造成逆变器输出波形失真的问题,研究了有源滤波器中逆变器的死区效应及其补偿方法。因PWM控制技术产生谐波效率较高,幅值较小,波形接近正弦波,故被广泛采用在有源滤波器(APF)的控制中,但实际应用时,因死区存在使逆变器输出的补偿电流波形在幅值和相位上产生偏差。故提出了电流反馈型死区补偿方法,它有效地解决了死区给有源滤波系统带来的补偿效果降低问题。仿真证明了该方法的有效性。

Dead-time Effects and Compensation Strategy of Inverters in Active Power Filter

Current harmonics caused by non-linear loads are one of the most common problems in power systems. Non-linear loads include saturated transformer, arc furnaces and semiconductor switches (AC-DC converters ,UPS-device and cycloconverters). If current harmonics are not filtered, voltage harmonics are produced in weak power supplies. Voltage harmonics cause additional losses and malfunctioning of the device connected in the same power supply. In addition to this, it leads to poor power factor, low energy efficiency and harmful disturbance to other appliances. With the rapid development of power electronic technology and the steady improvement of high-voltage devices, an alternative way to filter current harmonics is using active power filter(APF). A dead-time effects and implementation compensation strategy of active power filter is considered in this paper. Because the superiority of high harmonic efficiency and small amplitude, PWM control technology has widely used in the controller of active power filter. In practical application of active power filter, in order to avoid damage to power switching devices, a few seconds of dead-time must be inserted in the switching signals to prevent a short circuit. The delay is a serious drawback for PWM control technique. This will cause the deviation of the output voltage waveform, such as the decrease of the fundamental wave,increase of the harmonic amplitudes. To eliminate such a dead-time, the dead-time compensation must be introduced. This paper analyses the working principles of dead-time effect, it may practically be seen as a cyclic disturbance signal. By adopting current feedback compensation method, the PWM pulse widened or compressed by dead-time period can be compressed or widened, thus effectively compensating dead-time effect. Finally the simulation results indicate that the active power filter system can provide the required signals to perform filtering and compensation.