基于DSP的光伏并网发电系统软件锁相技术

Software PLL of grid-connected PV power generation system based on DSP

利用TMS320F2812事件管理模块EVA的2路CAP单元分别捕获经过信号调理的电网电压和并网电流对应的方波信号,根据所捕获的信号计算出电网电压与并网电流的频率和相位差,根据计算结果调节算法中的步进值和相位指针从而实现光伏逆变系统锁相控制。该算法以16位无符号整型变量为相位指针,利用该指针在调制频率下步进而周期性溢出的特点来产生同频正弦周期调制信号从而控制逆变输出。该方法提高了相位跟踪的精确性和快速性,实现了并网电流与电网电压同频同相,保证了光伏并网发电系统回馈电网的功率因数近似为1。样机测试结果表明该技术锁相精度高,锁相稳定,快速性好,易于实现。

The PLL （Phase-Locked Loop） control of PV inverter system is implemented ,which uses the 2-way CAP unit of TMS320F2812＇s event management module EVA to capture the square-wave signals of conditioned grid voltage and grid current,calculates the frequency and phase difference between them to adjust the step width and phase pointer. The algorithm takes a 16-bit unsigned integer variable ＂Index＂ as the phase pointer,which steps forward and overflows periodically to produce iso-frequeney sinusoidal modulating signal to control the output of inverter. It improves the accuracy and rapidity of phase tracking, resulting in same phase and frequency of grid current and grid voltage ,and ensures the feeding power factor of grid-connected PV system nearly one. Test results of prototype show that, the software PLL is easy to implement, with high accuracy, stability and rapidity.