基于改进的PR调节的单相LCL双闭环电流控制并网逆变器的研究

Research on Single-Phase LCL Dual-Loop Grid Current Control Based on the Modified PR Regulator

LCL滤波器具有滤波特性能好、体积小的优势,被越来越广泛地应用于单相并网逆变器中,但由于其电容支路极易产生谐振,对控制电路设计不利。目前可采用多种控制策略来解决上述问题。其中,单环并网电流控制策略是严重欠阻尼系统,谐振尖峰的存在会引起电流波形畸变,PI调节器并不能使闭环系统稳定,PR调节器通过增加特定频率的电流回路增益来抑制谐波误差,但频率漂移影响和控制系统的带宽。本文采用双环电流控制策略,提出一种频率跟随的PR控制器。试验结果表明,该策略能有效解决逆变器在电网频率波动情况下进网电流谐振和进网电流的功率因数问题。

With the advantages of good filter property and small size, LCL filter is widely applied in single-phase grid inverter. However, its capacitance branch is extremely vulnerable to resonances, which are harmful to the design of control circuit, so many strategies are proposed to solve the problem. Monocyclic grid current control strategy is a severe under damped system and the existence of resonant peaks can cause the distortion of current waveform. PI regulator is unable to stabilize the closed-loop system. In terms of PR regulator, by increasing the current loop gain of specific frequency, the error of harmonic can be restricted, but the frequency variations influences and controls the band width of the system. A kind of frequency variations influences is proposed and the double loop current control strategy is adopted in the paper. The experimental result indicates that this kind of strategy can effectively solve the problem of the inverter, in the case of the grid frequency fluctuation, giving rise to the grid current resonance and the power factor of the grid current.