Research of the Reactive Power Control Possibilities in the Grid-tied PV Power Plant

Results of control possibilities research of the reactive power generated by grid-tied PV power plant are presented in this paper. The innovative grid-connected inverter with the intermediate power storage chain (DC/DC converter) is used for the PV power plant. The converter operates well when DC input voltage generated by the PV source changes in a wide range. Mathematical description for the circuit part between the inverter output and the grid is presented. Detailed researches of PV system were carried out by means of the mathematical simulation. The researches disclosed dependence of the system reactive power on the phase of sinusoidal modulation voltage of the inverter. It is defined that phase of the modulation voltage must be positive and can vary in the range 0 divided by 20 degrees. Researches show that researched PV system can generate the capacitive reactive power for compensation of the inductive reactive power of the grid. Operation mode of the system when the reactive power is equal to zero can be achieved in this system. It is defined that electromagnetic distortion (THD) of the grid has maximal value at the point when the reactive power is equal to zero. Consequently, this feature must be evaluated at the design of the inverter filter.