Control Strategy For Grid-connected Converters Research Articles

Phase-Locked Strategy of Photovoltaic Connected to Distribution Network With High Proportion Electric Arc Furnace

With the rapid development of industrialization, the proportion of electric arc furnaces (EAF) in distribution networks is getting higher and higher. Aiming at the problem that grid voltage is distorted by a large number of arc furnace nonlinear loads accessing to distribution networks, it is crucial to make dynamic analysis of distribution network voltage and adopt a control strategy of grid-connected converter based on the new phase-locked loop (PLL) technology. As a result, the harmonic distortion rate is reduced and the quality of grid-connected current and voltage is improved. In this paper, photovoltaic (PV) system model and the typical dynamic model of the EAF are established. By analyzing the influence of the EAF model on the PV grid-connected converter with the traditional phase-locked loop while connected to distribution network, a control strategy of the PV grid-connected converter with the self-adjusting double SOGI (MAF-SASOGI) phase-locked loop with the ideal low-pass filter is proposed. Through the simulation analysis, it is verified that precise phase locked can be realized and harmonic content of the system can be reduced by the PLL strategy proposed in this paper. Therefore, the quality of PV grid-connected voltage and current is improved.

Research on Control Strategy of Grid-Connected Converter Based on Virtual Inertia

As the DC microgrid has low inertia, this paper draws on the virtual synchronous machine technology to propose and control a new virtual inertial control strategy. This control strategy enables the grid-connected converter to have both AC inertia and DC inertia. By small signal decomposition, the transfer function block diagram of the system is established. The effects of different inertial parameters on the system’s AC inertia and DC inertia are studied. The dynamic characteristic analysis and simulation results show that the proposed virtual inertial control can effectively suppress the fluctuation of DC bus voltage and AC power and increase the AC and DC inertia of the converter.