基于DSP的高精度UPS锁相技术

High Precision Phase-Lock Technology for UPS based on DSP

为了保证UPS由逆变输出转市电旁路时的可靠切换,其输出电压和电网电压的频率、相位应时刻保持一致。本文针对全数字化控制的UPS系统,结合锁相环原理,研究了利用TMS320F240型DSP实现高精度锁相的数字锁相环原理与实现方法。该方法利用DSP的捕获中断和周期中断读取市电和逆变输出的相位差,经PI调节器输出一个载波周期的补偿量,通过动态改变载波周期值实现逆变输出对市电的动态跟踪,理论上相位差分辨率可高达0.72°。文中给出了硬件实现电路及程序流程图。实验结果验证了该方案的可行性和有效性。

In order to realize the reliable switching when the inverter output of UPS turns to bypass,the frequency and phase of voltage between UPS and electrical network should be same at any moment.In the paper,this principle and realization method of DPLL （Digital Phase Lock Loop） with high precision by DSP TMS320F240 is presented.The phase error between UPS and electrical network is recorded by CAP interrupt and Period interrupt of DSP.A PI controller is applied to supply a compensation value for every carrier period.The dynamic tracing of inverter output to electrical network is realized by changing carrier period.The theoretic resolution of phase error is 0.72 degree.The circuit and the flow chart of program are given.Experiment result proves the scheme is feasible and effective.