A New Voltage Measure Method for MMC Based on Sample Delay Compensation

The nearest level control is suitable for modular multilevel converter (MMC) with large number of submodules (SM). The voltage measure method for MMC requires to install a voltage sensor for each SM, which increases the system costs and the burden of the data acquisition system. This paper presents a novel voltage measure method to solve this problem. With the proposed method, the SMs are divided into some groups, and each group is configured with only one voltage sensor. The voltage of each SM is obtained by an observer based on the charging and discharging model of the SM. In order to improve measurement accuracy, a compensation method is proposed for the delay of the voltage sensor and the A/D sampling chip. To verify the accuracy of the proposed measure method, the case studies are performed on a 30-level single-phase MMC simulation model under different operating conditions. At last, a nine-level single-phase MMC laboratory prototype is also set up to verify the performance of the proposed method.