电网电压不平衡下光伏并网逆变器的同步技术

为了保证光伏并网逆变器在电网电压不平衡下可靠地向电网输送功率,需要提高逆变器的同步跟踪能力及动态响应性能。提出一种基于比例积分简化型谐振调节器的锁频环(PISR-FLL)技术。PISR-FLL具有高增益带宽及频率自适应特点,能够从不平衡电网电压中准确快速地估算出基波频率正、负序分量。改进的锁频环(FLL)通过增益系数线性化后不但可以保证频率自适应调节,控制结构也变得简单,易于数字实现。仿真和实验结果表明该PISR-FLL技术精度高,动态性能优越,可以满足不平衡电网条件下电网信号同步跟踪要求。

Synchronization technique of grid-connected PV inverter under unbalanced grid voltage

In order to ensure that grid-connected PV inverter can convey power to the grid reliably under unbalanced grid voltage, it is necessary to improve the synchronous tracing ability of the grid-connected PV inverter and optimize its dynamic response performance. A new technique called proportion integral plus simplified resonant controller based on frequency-locked loop (PISR FLL) is proposed. PISR controller has the characteristics of high gain frequency band and frequency adaptivity, so it can accurately and quickly estimate the positive and negative sequence components of the power signal at the fundamental frequency from unbalanced grid voltage. After gain coefficient linearization, the improved frequency-locked loop (FLL) can not only rapidly realize the automatic frequency adjustment, but also simplify the structure of the control system, and the improved FLL is easy to be digitalized. Simulations and experiment results show that the PISR-FLL technique has high precision and good dynamic response, which meets the synchronous tracing requirement of the grid signal under unbalanced grid voltage.