LCC/MMC Coordinated Control Strategy Applied to DC Distribution Network

Line commutated Converter (LCC) and modular multilevel converter (MMC) are two commonly used converters in AC/DC power grid. LCC has the advantages of large capacity, low equipment cost and low operating loss, but also has the disadvantages such as slow response speed, which cannot control DC voltage well. Compared with LCC, MMC has the advantages of faster response speed, but also brings the disadvantages of higher operating loss, higher equipment cost, and smaller capacity. In order to reasonably exploit the advantages of LCC and MMC, LCC is introduced into DC distribution networks and a coordinated LCC/MMC control strategy applicable to DC distribution network structures is proposed in this paper. In steady-state operation, LCC and MMC perform power distribution according to the set distribution ratio, and LCC can be put into operation or shut down at the right time according to power changes. When power fluctuation occurs in the DC distribution network, DC voltage fluctuation spikes can be reduced by MMC under the action of the virtual direct current generator (VDG) control strategy. The simulation results of MATLAB/SIMULINK verify the feasibility and effectiveness of the method.