Research On Capacity Allocation Of Large-scale New Energy Grid-connected System With Flexible Direct Current Transmission

Under the guidance of new energy development and utilization policies,photovoltaic and wind power have developed rapidly.The new energy development rate of the “Northwest,North,and Northeast China” is far greater than the new energy utilization rate.The traditional way to improve the new energy utilization rate is to collect the electric energy from the AC line and then send it to the central and eastern load of China through the grid commutated high-voltage direct current transmission(LCC-HVDC).However,the AC transmission capacity is small,the distance is close,and the system stability is general.Therefore,there are many restrictions on the large-scale transportation of new energy which base is far away from the LCC-HVDC sending end.Therefore,the energy collection strategy of the energy base away from the LCC-HVDC transmission end is studied,and then the energy base capacity allocation problem under the aggregation strategy is studied,which improves the energy utilization rate of the energy base,improves the economic efficiency of the LCC-HVDC delivery system,and alleviates the new energy consumption of the system.Nano pressure is of great significance.After collecting the energy which far away from the LCC-HVDC sending,aiming at the problem of low utilization rate of new energy.By comparing and analyzing the advantages and disadvantages of the energy base energy collection through AC transmission,VSC-HVDC and LCC-HVDC,it is proposed that the electric energy is collected by VSC-HVDC and sent to the central and eastern load center of China through the LCC-HVDC channel.establish an economic dispatch model for the LCC-HVDC delivery system under this strategy.Aiming at the multi-objective optimization problem of power system,the advantages and disadvantages of different optimization algorithms are compared and analyzed,and an improved non-dominated sorting genetic algorithm(NSGA-Ⅱ)with elite strategy is proposed.The improved NSGA-Ⅱ fixed NSGGA-Ⅱ congestion ranking strategy by dynamic crowding sorting strategy.The NSGA-Ⅱ SBX crossover operator was fixed by adaptive tDX(adaptive-tDX,a-tDX)crossover operator.The NSGA-Ⅱ,the comparative NSGA-Ⅱ and the improved NSGA-Ⅱ were calculated on the five standard test functions,and the population diversity and convergence speed were used as evaluation indicators to evaluate the advantages and disadvantages of the three algorithms.The improved NSGA-Ⅱ proposed in this paper is applied to the energy base capacity optimization configuration based on the proposed topology of the energy base energy collected by the VSC-HVDC and then sent by the LCC-HVDC.The problem and the case study are carried out to determine the optimal installed capacity of each power supply.The influence of the power supply structure on the LCC-HVDC sending end system is analyzed by a single variable method to further verify the accuracy of the proposed algorithm.