Papers by Author: Hong Hua Xu

Abstract: Renewable energy are usually connected to the power grid through an inverter. As the penetration level of such inverter-based distribution generation resources increases, PCC point harmonics become an important concern for grid stability and power quality. In this paper, the PCC-point harmonics in a parallel-inverter-based photovoltaic station were measured and some significant characteristics of such harmonics were presented. These harmonics are stationary; the voltage and current waveforms are lower frequency, power correlation and inter-harmonic. And these harmonics are 3-phase symmetric and contain 3^rd and 6^th harmonic components. The transitions of the PCC harmonic occurrence and vanishing are instantaneous. The analysis indicates that the PCC harmonics are not produced by the resonances related to the linearities of PV inverters but the inverter nonlinearities are the primary reasons. The strategy to eliminate the PCC point harmonics are proposed in this study.

Abstract: With the rapid development of the VSC-HVDC Power transmission and distribution grid demonstration projects, the technology of the DC transmission once again becomes a research focus. In order to meet the needs of accessing VSC-HVDC power grid of Photovoltaic power generation, the topologies suitable for photovoltaic high voltage DC grid-connected converter was analyzed, the program based on the dual-module combination of full-bridge topology structure was proposed, a detailed control strategy using dual-loop of voltage and current loops was given, and finally a 12kW simulation model to verifying the system topology and control strategy was constructed using PSIM. The simulation results show that the PV high voltage DC grid-connected converter has a good dynamic response and steady state performance.

Abstract: Wind speed prediction is critical for wind energy conversion system since it not only can relieve or avoid the disadvantageous impact on power system, but also can enhance the competitive ability of wind power plants against others in electricity markets. The model presented in this paper was based on artificial neural network (ANN) and the selection of the model parameters was presented in detail. The autocorrelation function (ACF) of wind speed time series was used to determine the input variables of the neural network. The simulation was carried out with the proposed ANN model.The conclusion that the optimal network structure may be different corresponding to different error evaluation was drawn through a large number of simulation experiments. And the simulaiton results showed that the ANN model is less than 10.77% in terms of root mean square error and 5.86% in terms of mean absolute error compared with the persistence model.