Instantaneous Power Loss Calculation for MMC Based on Virtual Arm Mathematical Model

The present methods for MMC (Modular Multi-level Converter) valve loss estimation are either inaccurate or time consuming. This paper proposed a virtual arm mathematical model (VAMM). Based on this model, the valve loss of MMC could be calculated accurately as well as quickly. What's more, this calculation method is valid for various operating conditions, different modulation and voltage balancing strategies. Firstly, an introduction of VAMM was presented and the mathematical equations for evaluating valve loss were deduced. Then the comparison with 11-level detailed switching model was given to verify the accuracy of VAMM. Finally, the proposed method was carried out on the valve loss analysis of Zhangbei MMC-HVDC (High Voltage Direct Current) system, results showing a good agreement with traditional analytic calculation method. And the distribution characteristics of valve loss under various operating conditions were also analyzed.