Small Signal Stability Analysis And Control Parameters Optimization Of Microgrid Based On Various Control Methods

With the rapid development of human society, traditional fossil fuels exposed more prominent limitations, non-polluting and inexhaustible new energy has become an inevitable choice. Microgrid as an effective way to make full use of new energy, has been widely concerned in the world. The distributed sourceds in microgrid use power electronic interfaces to connect to the bus, so the inertia is poor, and it is easy to be unstable when disturbed, so the small signal stability has become an important research direction. However, current study focused on single-machine infinite-bus system and simplified micro-grid system containing less than two distributed generators, but systems simplified too much may lose some important system eigenvalue information, and thus affect the accuracy of parameter optimization effect; the control is concentrated in the droop control, however droop control has its own limitations, other control methods have a great value. The small signal stability of microgrid under various control strategy has been studied in this paper as follows:1 Summarized the control strategies for micro-grid, including dispersion control and distributed control of AC and AC-DC hybrid microgrid, analyzed the principle, advantages and disadvantages and Applications of various control strategies. Introduced the the mathematical theory of small signal stability analysis, and pointed out the physical meaning of eigenvalues and participation factor of the microgrid system.2 Established the mathematical model of the AC micro-grid system based on the single-master-slave control, calculated the eigenvalues of the system by programing in the Maple software, solved the complexity and fallibility problem of manual calculating high-level systems, and gives the program in the Appendix; Based on the calculated eigenvalues, a detailed analysis of small signal stability of the system is given to find out the weak parts of the system prone to instability.By root locus analysis, gives a optimized control parameters of the system. Then verified of the parameter optimization results in Maple software by time domain simulation.3 As the traditional multi-master-slave control system is more prone to produce circulation between the master source, this chapter proposed the circulation suppression control strategy based on power sharing and the average consensus algorithm, established the mathematical model of four master power source and a slave power source. A detailed analysis of the impact on the system small signal stability of communication latency is given, and proposed a control parameters coordinated optimization method based on the root locus method and particle swarm optimization. Finally, time-domain simulations demonstrate the effectiveness of the circulation inhibitory effect of control strategy and parameter optimization method.4 The small signal stability of the DC side of the AC-DC hybrid microgrid is mainly analysised, found out the most influential factors of the DC voltage, and gave the general method to improve its stability. Finally, optimized the control parameters of the system by the root locus analysis.