一种新颖的并网逆变器自适应电流滞环控制策略

Adaptive current hysteresis control of grid-connected inverter

采用通过L滤波器滤波的单相单级光伏逆变器并网的拓扑结构和电流滞环跟踪控制,基于固定电流滞环宽度控制的数学模型,推导开关频率和滞环宽度的数学表达式,表明开关频率按照二倍频余弦调制变化,导致开关损耗,EMI增加和滤波器设计困难,提出一种能根据系统电气参数(如光伏阵列直流电压、开关频率、电网电压和参考电流斜率)动态调整滞环宽度的自适应滞环电流控制算法,能实现开关频率的固定化;为解决非线性负载光伏供电的电能质量问题,提出能实现谐波电流和无功电流分量补偿的参考电流计算器模型;提出将自适应电流滞环宽度算法,参考电流计算器、PLL锁相环技术以及最大功率跟踪算法集成在统一的柔性控制器,基于Simcoupler和Matlab/Simulink的仿真分析表明,该控制策略解决固定滞环电流控制开关频率瞬时变化的问题,使滞环宽度瞬时调制而开关频率保持不变,可使电网功率因数接近为1。

With the topology of single- phase single- stage photovohaic grid- connected inverter and its hysteresis band current control via L filter, and based on the mathematical model of constant hysteresis band current control,the analytical expression of switching frequency and hysteresis band width is derived, which indicates that,the switching frequency is cosine modulated at double fundamental frequency,resulting in the switching frequency loss increase,EMI increase and filter design difficulty. An adaptive hysteresis band current control algorithm is proposed,which dynamically adjusts the hysteresis band width according to electrical parameters,such as photovoltaic DC voltage,power grid voltage,switching frequency and reference current slope,to fix the switching frequency;a reference current calculator model is put forward to improve the power quality of non-linear load,which compensates the harmonic and reactive current components. A flexible controller applying the adaptive hysteresis band current control algorithm, reference current calculator,PLL technique and maximum power point tracking algorithm is proposed. The simulation with Simcoupler and Matlab/Simulink shows that,the proposed control algorithm fixes the switching frequency and makes the power factor of grid near unity.