Study On Damping Control In Power Systems Based Measurement And Computational Intelligence

With the application of nation-wide power grid interconnection and China's power transmission from the West to the East, the damping of power system will be reduced. As a result, low frequency oscillation will easily be inducted under disturbance, which will affect the safety and stability of power system greatly and limit the power transmission between interconnected power systems. Power system stabilizer (PSS) of excitation system and flexible ac transmission system (FACTS) damping controller can all damp low frequency oscillation effectively, and improve security and economy of power system.This paper studied the problem of damping controller design in power system using measurement and intelligent optimization method. Prony method is used to identify electromechanical modes of low frequency oscillation, and a novel particle swarm optimization (PSO) algorithm is presented to coordinate parameters of damping controller. In addition, propagation characteristic of electromechanical disturbance and Wide-area Prony analysis method are studied. The following details are the main content of this paper.(1) Based on small disturbances analytical method, low frequency oscillation modes of typical power system are analyzed. It shows that the active power increment of generator includes local modes and inter-area modes disturbance. For the electromechanical disturbance of different generators belong to the same area, the interaction between the same local modes is reduced, but is enhanced in inter-area mode. Furthermore, the simulation results show that the electromechanical disturbance is propagated penetrably in power system, and the propagation speed is related to the rotary inertia of generator.(2) Solving step and model order selection of Prony method is analyzed. The feasibility of Prony method can be used to identify oscillation mode and residues is verified by the example of analyzing ideal signal mode and identifying transfer function of control system.(3) Particle swarm optimization (PSO) algorithm is studied by this paper. In order to solve the convergence problem of PSO and obtain expectance optimization object value, a novel fuzzy adaptive particle swarm optimization based on T-S model (T-SPSO) is presented, in which the inertia weight is updated adaptively according to the best current fitness and inertia weight. The simulation for the typical benchmark function and PID controller parameter optimization verified the effectiveness and superiority of T-SPSO algorithm.(4) Based on wide-area measurements system (WAMS) and characteristics of electromechanical disturbance propagation, an idea of low-frequency oscillations mode identification is presented. One generator is selected from each supply area and small disturbance is exerted to it simultaneously. The electric power signals of every generator in every supply area are then analyzed using Prony method at the same time and all electromechanical oscillation modes are thus accurately obtained according to oscillation magnitude. The residues method of Prony analysis is used to get the participation degree of every generator in oscillation mode, based on which, a wide-area Prony analysis scheme of low-frequency oscillations is studied. It accurately identifies all oscillation modes, selects the damping controllers and determines the optimal installation site of power system stabilizer, as well as provides the necessary predictive data for emergency control of power system.(5) For the parameters optimization of multi-machine PSS, the control strategy is studied, which uses Prony method to identify electromechanical modes of low frequency oscillation, and T-SPSO algorithm to coordinate the parameters of PSS. The residue method based Prony analysis is used to choose the best position of PSS installation firstly, and then eigenvalues are obtained by analyzing sampling data using Prony method. Finally, T-SPSO algorithm is used to optimize PSS parameters which taking damping ratio as objective function. Simulation results show that the PSS parameters can be optimized effectively using this method.(6) Taking static synchronous series compensator (SSSC) damping controller design for example, FACTS damping control based wide-area measurements system is studied. In order to solve the parameter optimization of damping controller, a wide-area coordination damping control method is studied based on Prony and intelligent optimization algorithm. Simulation results show that the SSSC damping controller can damp inter-area mode low frequency oscillation in power system effectively.