Research On Power System Harmomic State Estimation

With the widespread use of nonlinear load in the power grid, more and more harmonics are injected into the power system, the harmonic has seriously affected the power quality and grid security. We must firstly define the distribution and state of the harmonic in the power grid to effectively control and eliminate harmonics. The harmonic state estimation can accord the measured value of the limited point to estimate the whole network of harmonic state, it can provide an effective evidence for harmonic monitoring, suppression and management.The modcm measurement technology is prior condition of the harmonic state estimation(HSE), meanwhile it brings some advancement for the relevant problems about measurement variables, estimation models, solution algorithm and observation analysis. Firstly this paper introduces harmonic monitoring system of harmonic state estimation, then describes the harmonic mathematical model of harmonic estimate, this paper selects synchronism value of voltage, bus influx current and branch current as measurement variables, the bus voltage in the whole system as status variables, then establishs the phase measurement equation and describes solution method of harmonic state estimation. For the distinctive with harmonic state estimation and the traditional state estimation, this paper analyzes the pros and cons of method about the observabilities and uses the five node system as examples and varies the rationality of the algorithm at last.The quality of harmonic state estimation is the function of the number and location of measurement device, for the problem of optimal allocation of measurement points, this paper proposes discrete particle swarm optimization(PSO) to apply for the optimal allocation of measurement points, this paper systematically analyzes convergence accuracy and speed which was affected by the choice of particle swarm algorithm parameters. To prevent particle swarm convergence speed into a local optimum, taking the full network observability of power system operation state and the least number of phasor measurement units(PMU) as objective, this paper proposes an optimal PMU placement algorithm based on discrete particle swarm optimization in a ring structure, which aiming at ensuring the system’s largest observation, the redundancy and economic of measurement. The algorithm is proved to be reasonable through IEEE-14bus simulation system.Finally, according to the characteristics of the harmonic state estimati-on equations, two method based on least squares method and particle swarm optimization were given to research the impact caused by different measurement configurations. Judging by nodal injected harmonic active power, harmonic source location based on harmonic state estimation is realized. The results of harmonic state estimation and simulation are compared and then, the theory and algorithm related to this project are validated.