| With the rapid development of interconnected power system and power market,flexible AC transmission system(FACTS) has got more and more attention. FACTS technology has unique advantages in controlling the power flow, increasing the inter-regional transmission capacity of the system and improving the reliability of the system. How to make better use of the FACTS device to improve the system available transfer capability and improve the voltage stability of the system without changing the operation mode and network structure has become an issue of great concern to researchers.The rational allocation of FACTS devices is very important due to the high cost. If the location of FACTS device is improper, it may lead to the decrease of transmission capacity and system stability variation, the inappropriate choice of equipment capacity may result in the waste of investment cost. TCSC and STATCOM is widely used FACTS devices, this paper mainly studies the location and sizing optimization of TCSC and STATCOM to effectively reduce the system network loss, improve voltage stability, improve the system available transfer capability.The studies on optimal allocation of FACTS equipment are mostly single objective optimization with a single optimal solution, which can not provide the decision makers with different preference. According to the working principle of TCSC and STATCOM, the steady state mathematical model of the two equipments is established. Firstly, a multi-objective optimization model of minimize the real power losses, value of voltage deviation, compensation cost is established to optimize the locating and sizing of STATCOM. Secondly, two multi-objective optimization models are established in order to solve the optimization of installation of TCSC and STATCOM in power system. The active power loss, voltage stability index and compensation cost are set to three objective functions in the first model. In order to improve the available transfer capability, a multi-objective optimization model is established by considering the voltage stability index and the compensation cost of the equipment simultaneously in the second model. Multi objective optimization can obtain the optimal solution set for the optimal allocation of TCSC and STATOM of multiple operation indexes, which can be used for decision makers to choose the best compensation method according to the preference.The optimal location and capacity of TCSC and STATCOM is a multi objective optimization problem with nonlinear, discontinuous and mixed integer programming. Inthis paper, the harmony search algorithm is used to solve the problem with simple structure,few parameters and strong robustness. An improved differential harmony search algorithm has been proposed in this paper, mutation and crossover operation are adopted instead of the original pitch adjustment operation of harmony search algorithm, which is intended to avoid the problem of over reliance on the adjusting step in the process of searching for harmony search algorithm, and effective use of the optimal solution of the information to guide the harmonic vector to find a better solution as soon as possible.The multi-objective optimization problem of STATCOM and TCSC locating and sizing are simulated by IEEE30 bus system and IEEE14 bus system respectively. This paper uses the improved multi-objective differential harmony search algorithm to optimize the location and capacity of TCSC and STATCOM. By comparing the results with the optimization results of the multiple population quantum particle swarm optimization, the effectiveness of the proposed algorithm is verified. In this paper, we considerd three kinds of compensation methods for two kinds of equipment separately and hybrid compensation,the calculation results show that mixed compensation can get better system performance indicators solution compared to use a single device to compensate. Results of this study provide new research ideas for the FACTS device configuration of actual system. |
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