中文摘要：

在采用传统双闭环控制策略的模块化多电平换流器（MMC）中,电感参数变化可能对设备造成不良影响。为此,利用αβ坐标系中电压和功率之间的数学模型,设计了一种无锁相环的直接功率控制（DPC）策略。该DPC中,通过一种无需使用系统角频率和电感参数的功率解耦控制器,将传统的双闭环简化为αβ坐标系中的单个功率环,避免系统频率偏移和电感参数变化对控制系统的不良影响。同时,该DPC还能实现有功功率和无功功率的独立解耦控制。仿真结果表明,与传统控制策略相比,所提DPC具有更小的功率波动、较好的谐波抑制能力以及较快的系统动态响应,适用于与强电网联接的换流站。

英文摘要：

For modular multilevel converters using two-closed-loop control, the variation inductance parameters could affect the operation of the devices. Therefore, using a mathematical model of grid voltage and power in αβ coordinate system, we designed a direct power control（DPC） strategy that could operate without phase lock loop（PLL）. In this DPC, a power-decoupling controller, which works without using angular frequency and equivalent inductance, is adopted. Hence, the tradition two-closed-loop control is simplified into a power closed-loop control in αβ coordinate system, and the possible influence from variation of angular frequency and equivalent inductance is avoided. Plus, the proposed DPC also realizes control decoupling active power and reactive power. Further simulation indicates that, compared with traditional control strategies, the proposed DPC strategy has smaller power fluctuation, faster transient response and better harmonic suppression function, and it is suitable for converters connected to strong power grid.