改进相位差测量在感应加热电源频率跟踪中的应用

在感应加热电源的频率跟踪环节中,需要对负载电压和电流信号相位差进行测量.由于待测负载信号存在波形畸变,使得常用的过零比较法在实现时存在一定误差.为了解决这一问题,提出一种改进的相位差测量方法.利用dsPIC的输入捕捉模块测量负载信号的周期,配合快速傅里叶变换得到负载电压和电流信号相位差,然后对测得的相位差进行修正和补偿,最终实现系统频率跟踪功能.实验结果表明,该方法可以使逆变电路输出较为准确地跟踪负载固有谐振频率的变化,提高了系统的工作性能,较好地达到系统频率跟踪的要求,在实际设计中有一定的应用价值.

Application Research on Improved Phase Difference Measurement in Frequency Tracking of Induction Heating Power Supply

In the frequency tracking part of the induction heating power supply,it is necessary to measure the phase difference of the load voltage and the current signal.Because of the existence of the waveform distortion of the load signal to be measured,there is a certain error in the commonly used zero-cross comparison method in achieving the required measurement.In order to solve this problem,an improved phase difference measurement method is proposed.The dsPIC input capture module is used to measure the load signal cycle,and with fast Fourier transform to get the load voltage and current signal phase difference.Then the measured phase difference is corrected and compensated to realize the system frequency tracking function.The experimental results show that this method can make the output of inverter track accurately the change of the natural resonant frequency of the load and improve the working performance of the system,which can meet the requirement of frequency tracking and have certain reference value in practical products.