Operation-Characteristic Calculation of MMC Based HVDC Grid

摘要

The steady-state operation characteristics calculation (SOCC) is of great significance in the parameter determination and protection design of modular multilevel converter based high voltage direct current (MMC-HVDC) gird. When the grid consists of lots of MMCs, however, SOCC can be difficult and inefficient because there are too many state variables to be calculated. In response to this problem, this paper proposes a cross-iterative algorithm for the SOCC by using a modular approach. Firstly, the mathematical model and control system of MMC are investigated, based on which a single MMC is considered as the basic unit to the SSOC of the entire grid. Then, the basic principle of proposed cross-iteration algorithm is introduced. This algorithm just iteratively invokes the SSOC function of single MMC and therefore avoids too many unnecessary programming. Following that, a calculation method is presented to obtain the peak value of non-sinusoidal waveforms of each variable. Finally, simulation results in SIMULINK verify the correctness and effectiveness of the proposed calculation methods.