The min-projection strategy (MPS) is a switching rule with better convergence speed, which can improve the dynamic characteristics of three-phase grid-connected inverters. However, the grid-connected current harmonics of the system are large when the MPS is used directly in the digital control framework due to the limitations of the sampling frequency. To solve this problem, an improved min-projection strategy is proposed in this paper by introducing a zero voltage vector to the control. First, the non-zero voltage vector is selected through the switching law function of the MPS. Then the time occupied by the non-zero voltage vector and the zero voltage vector can be obtained through an error function, which is established by the principle of minimum current error. Finally, the switching signal can be obtained for control, based on the method of duty cycle modulation. This method can realize fast current tracking and current decoupling control, reduce the grid-connected current harmonics, and improve the steady state performance of the system without increasing costs. The effectiveness of the proposed method is verified by simulations and experimental results.

最小投影策略（MPS）是一种收敛速度较快的切换规则，可以改善三相并网逆变器的动态特性。然而，由于采样频率的限制，当MPS直接用于数字控制架构时，系统的并网电流谐波较大。为了解决这个问题，本文提出了一种改进的最小投影策略，将零电压矢量引入控制。首先，通过 MPS 的开关律函数选择非零电压矢量。然后可以通过误差函数得到非零电压矢量和零电压矢量所占用的时间，该误差函数是由最小电流误差原理建立的。最后可以得到开关信号进行控制，基于占空比调制的方法。该方法可以在不增加成本的情况下实现快速电流跟踪和电流解耦控制，减少并网电流谐波，提高系统稳态性能。通过仿真和实验结果验证了所提方法的有效性。