The Control Method Research Of Photovoltaic (PV) Grid System With Power Grid Voltage Support

Different from traditional power supplies, PV has the features of time variation and instability, thus research on the control strategies of the gird-connected PV is of great importance.When the PV output voltage and gird voltage fluctuates, it can be stabilized by regulating the control strategies, thus improving the stability of PV gird-connected power system. The system stability can be determined by whether it is accord with the small signal stability. This paper uses theoretical analysis, PSCAD and MATLAB to study the system control strategies and stability of gird-connected PV. The main contents of this paper are as follows:(1)The basic features and the work principles of PV array are introduced, the system structure and implement scheme of gird-connected PV are illustrated, and the judgement requirements and methods of small signal stability are explained.(2)A complete PV grid-connected power system model is built using the PSCAD. The Boost transform control and PV inverter control are utilized to achieve the stable PV integration under the situation of constant changing illumination intensity and temperature. Add the voltage detecting element to the three phase power gird, so when voltage oscillation happens, the required reactive power compensation based on the voltage and reactive power standard curve can be measured, then by regulating the inverter control signal to change the inverter output grid-connected voltage and to achieve the effective support of the grid voltage.(3)The small signal decision matrix model of PV grid-connected power system is built. The small signal stability can be determined by using the characteristic value of characteristic matrix calculated. And the impacts of system control parameters to the small signal stability are analyzed. The system and control parameters can be optimized and the system stability can be improved based on the parameter sensitivity analysis method.All of the above work introduces the grid voltage support ability of PV grid-connected power system from the theory and simulation aspects. It can be obtained from the results of the case study that the method can effectively support the grid voltage under the premise of ensuring the stability of the system; and optimize the system stability by adjusting the control parameters.