摘要
应用于光伏系统的准Z源逆变器(QZSI)存在着不稳定的零动态和非线性特性,导致系统振荡、动态响应缓慢和控制器设计复杂等问题。基于输入/输出反馈线性化方法,提出将直通电流和脉冲直流电压作为状态变量建立QZSI直流侧的仿射非线性二阶模型,将原非线性系统转化为线性系统,具有模型精确、阶数低、算法简单等优点。基于此模型,设计经典PI控制器调节QZSI的输入电压,并最终实现最大功率点跟踪(MPPT)。阐述了QZSI的输入/输出线性化建模方法,并通过理论推导证明该线性化系统零动态稳定,设计QZSI直流侧与交流侧控制器,实现光伏逆变器升压、并网波形及功率控制3个目标。通过仿真及实验与经典控制策略对比,显示该控制方法能使QZSI输入电压快速跟踪最大功率点,并且在系统工作点大范围变化时能保证输入电压及并网电流波形质量。
The quasi-Z-source inverter(QZSI) applied to the photovoltaic(PV) system has nonlinear and unstable zero dynamic characteristics, which leads to the problem of system oscillation, slow dynamic response and complex controller design. Thereby, we propose a nonlinear control strategy based on Input-output Linearization for QZSI. The affine nonlinear model of the QZSI DC-side is presented and transformed to a linearized form with the help of input-output feedback linearization technique. Based on the linearized system, simple linear controllers are employed to regulate the input voltage of the QZSI, and finally achieve maximum power point tracking. Moreover, the input/output linearization modeling method for the quasi Z-source inverter is described. The zero dynamic stability of the linearized system is proved by theoretical deduction. The DC-side and AC-side controller of the quasi Z-source inverter are designed to realize the three targets of boosting the PV inverter and controlling the grid-connected waveform and the power. Through simulation and experiment, compared with classical control strategy, it is shown that this control method can make QZSI input voltage to track the maximum power point fast, and guarantee the quality of input voltage and grid-connected current waveform when the operation point of the system changes in a wide range.
引文
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