Research On Coordination And Optimization Of DC Modulation Controller Parameters In Multi-infeed Transmission System Based On Chaos Cloud Particle Swarm Algorithm

In recent years, with the expansion of large-scale AC/DC interconnected grids and the increase of the liaison line’s load, the long distance and large capacity transmission lines have been formed, the power system structure and control requirements have become more and more complex. With the general application of fast excitation system with high magnification, the system damping property is weakened, which results in the system becoming underdamped running state, and then causes the phenomenon of the inter-area low frequency oscillation and seriously affects the safe and stable operation of the whole power system. The application of DC power modulation of DC transmission lines can effectively suppress the phenomenon of inter-area low frequency oscillation between the AC/DC interconnected grids.Since each power modulation of DC system is designed for improving one particular oscillation mode in multi-infeed AC/DC power system. There are mutual weakened effects due to the lack of coordination among each DC modulator, the system will produce negative damping even result in the unstable operation. And the parameters of DC modulators are important factors affecting modulation effects, so it is necessary to coordinate and optimize the parameters of each DC modulator in the interconnected system.In this dissertation, the multi-signal is firstly introduced into the improved Prony algorithm based on singular value decomposed-total least squares(SVD-TLS) to determine the signal order, and then comprehensively identify the low frequency oscillation modes in AC/DC systems, so that the mutual influence between the DC modulators is identified and simplified, which is used as the basis of the coordination and optimization model. Secondly, a control strategy that applying the chaos cloud particle swarm optimization(CCPSO) algorithm to optimize the parameters of each DC modulatior is proposed. By introducing the chaotic motion to initialize the particles and combining with the cloud model to adaptively adjust inertia weight coefficient, the shortcomings of particle swarm algorithm that is easy to fall into local extremum and low search accuracy will be overcome. Finally, the integral square error(ISE) with quadratic performance index is applied in the global coordination and optimization of DC modulation. Then the objective function is constructed on the basis of above criterions. Owing to the objective function contains the variables associated with the damping property of system, which can greatly reflect the low frequency oscillation of system. Besides, it isn’t necessary to establish the explicit function relationship between objective function and the parameters which need to be optimized. Therefore, it avoids establishing complex mathematical model of AC/DC system.The IEEE eight generators and three regions multi-infeed AC/DC transmission system are chosen as test system. The system doesn’t add the DC modulators and adds the DC modulators whose parameters without coordination and optimization, as well as adds DC modulators whose parameters are respectively optimized by PSO and CPSO, CCPSO algorithm are simulated. Finally, the simulation results are taken to verify the feasibility and effectiveness of the proposed optimization strategy.