AD/DC Hybrid System For Optimal Power Flow Based On Electromagnetism-Like Mechanism

With the development of power industry rapidly and the reform of electric power market, researchers pay more attention to the safety、steady and economy of the power system running. The high voltage direct current(HVDC) technology recently is hot and applied in the power grid which makes AC/DC hybrid transmission system to be important transmission means of the regional grid interconnection. Meanwhile, in order to ensure the power grid reliability and deliver power with low loss, optimal power flow(OPF) of AC/DC system plays a very important part of power system economic running.This paper makes an optimal model of AC/DC hybrid transmission system, considering several modes of DC system. The AC/DC hybrid transmission system can achieve the minimum active power loss by reasonably allocating the control variables and state variables of AC and DC transmission system while the constraint conditions are satisfied in upper and lower bound. Therefore, finding a reasonable and effective method to solve OPF model of AC/DC interconnected system is of great significance.Firstly, through analyzed and compared with classical optimization algorithms and artificial intelligence algorithm, a novel swarm intelligence algorithm named Electromagnetism-like mechanism(EM) is studied. Then analyzed the performance and running mechanism of the algorithm and further studying, this paper puts forward to the improved Electromagnetism-like mechanism(IEM) to apply in solving the proposed optimal model. In order to prove Electromagnetism-like mechanism that can feasibly and effectively solve the OPF problem. With IEEE-30and118nodes standard system and its modified AC/DC hybrid transmission system, the article builds the optimization model to simulate and analyze. Examples show that optimization results are influenced by the control modes of DC system. So in actual system, it needs to choose reasonable control mode of DC system according to the demand of the power system. Simultaneously, compared with the PF calculation of AC/DC system and the OPF calculation of AC system, the optimal power flow of AC/DC gets the minimum value of system loss which indicates the optimal power flow of AC/DC plays a very important role of the system economics.The simulation results show that EM has characteristics which can fast search the optimal value, simply operate and effectively deal with discrete variable problem; Furthermore, through using some optimization strategy, the algorithm can avoid falling into local optimum but with a faster speed of convergence to the global optimal solution.