A Hysteretic Switching Control Strategy for Photovoltaic Generation System Integration under System Strength Change

With the increasing penetration of renewable energy such as photovoltaic (PV) in the power system, the grid shows the characteristics of low inertia and low short circuit ratio (SCR), which seriously deteriorates the anti-interference ability of the system. The output characteristic of the PV generation system is determined by the system connecting converter (SCC). In order to protect the PV system from system disturbance while trying to provide necessary support during system contingency, how to select the appropriate control strategy of the SCC to become a crucial problem that has received much attention. In this paper, a hysteretic switching control strategy with the combining of the vector current control (VCC) and power synchronization control (PSC) is proposed to provide continuously operating capability of the PV generation system during the system strength continuous and large-scale change. Firstly, two PV SCC control strategies, VCC and PSC, are analyzed under different system strengths by small-signal stability analysis. Then, based on the obtained critical short circuit ratio (CSCR), a hysteretic switching control strategy is developed to realize a smooth switch between the VCC and PSC during the system strength change. A PV generation system connected to the modified IEEE 33 bus system is established in PSCAD/EMTDC to verify the effectiveness of the proposed hysteretic switching control strategy. The simulation results indicate that the application of the hysteretic switching strategy proposed in this paper can keep the PV generation system work stability during the system contingency.