Research On Photovoltaic Grid-connected Power Regulating System Based On Zonal Control

The main function of Routine photovoltaic(PV) power generation, with extra reactive compensation devices equipped, is affording active power to electric network, the effects of which on improving the quality of power supply is limited. So adding grid-connected power regulating control, integrated with the function of active power output, reactive power compensation and harmonic wave suppression into PV power generation system, would be important, as it has obvious effects in improving power supply quality, reducing transmission losses and saving costs of compensation devices.Presently, it is active and reactive power decoupling control strategies that are adopted in PV grid-connected power regulation system. These strategies have the characteristics of clear concept and high control precision, yet are sensitive to network parameters and not suitable for using in distribution network. In this paper, a PV grid-connected power regulation control method based on zonal control is introduced, in allusion to the limits showed in traditional methods. In this method, the operation area of PV system on P-Q plane would be divided into several subareas. Based on output active power of PV and voltage at PCC that has been measured, relevant control parameters could be provided, so the operating point of PV power generation system could be landed in corresponding subarea. Each subarea represents a kind of operation modes with similar qualities, and control precision would become higher with the area being more fine divided. As the grid-connected power model does not change with the network parameters, the discussed strategy can be suitable for the use of PV generation connected to all voltage level grids.When the PCC voltage changes, to avoid the deviation problem of PV operating points that easily occurs in implementing zonal control a correction method based on total differential is proposed. Moreover, allowing for that the damp is too little with LC filter,,both the design plans of LRC filter with damp and selection principles of damp resistance are analyzed.A single phase PV system using the zonal control strategy is connected to a 25 buses low voltage level distribution network, by which the detailed process of zonal control is explained, also the influence on distribution network voltage qualities and load flow is analyzed.The case validates the effectiveness of the discussed method.