本文主体内容包括以下四部分：首先对三电平逆变器进行数学建模，介绍了相间解耦滞环电流控制的原理；然后以第三相固定开关状态-1的分区方法为例，分析了误差电流在扇区边界失控的原理，针对不同分区方法的特点，提出固定开关状态切换控制的相间电流滞环控制策略；针对开关频率不定的问题，通过当前开关周期内的环宽和误差电流变化时间推导出下一个周期的环宽，进而实现定频控制；最后通过离线仿真验证了所提出策略的有效性。

本文所提方法能够有效解决在扇区边界误差电流失控的问题，提高了控制器的控制精度，且能实现定频控制，具有较高的应用价值。

With the increasing application of inverters in power systems, hysteresis current control as a current inner loop control method has received widespread attention. However, traditional hysteresis current control methods may result in uncontrolled error currents at sector boundaries, leading to a decrease in the control accuracy of the controller. A fixed frequency hysteresis current control of three-level inverters based on fixed switch state switching is proposed to improve the control performance at sector boundaries.

The main content of this article includes the following four parts: Firstly, a mathematical model of the three-level inverter was established, and the principle of phase to phase decoupling hysteresis current control was introduced; Then, taking the partitioning method of the third phase fixed switch state-1 as an example, the principle of error current losing control at the sector boundary was analyzed. Based on the characteristics of different partitioning methods, a phase to phase current hysteresis control strategy for fixed switch state switching control was proposed; To address the issue of variable switching frequency, the loop width for the next cycle is derived based on the current switching cycle and the time of error current variation, thereby achieving fixed frequency control; Finally, the effectiveness of the proposed strategy was verified through offline simulation analysis.

The method proposed in this article can effectively solve the problem of uncontrolled current error at sector boundaries, improve the control accuracy of the controller, and achieve fixed frequency control, which has high application value.

Ye Kangquan is a master's candidate at the School of Electric Power, South China University of Technology, with a research focus on photovoltaic inverter control technology. magork@163.com