Primary and secondary frequency regulation with photovoltaic generators

With the increasing number of distributed generators which transform renewable power sources to electricity, PV generators trough invertors, when is usually difficult to make power output regulation from the primary source side, is the problem of the output power adapting according to the consumption requirements increasingly important. Therefore, it will be necessary to involve these sources to the transmitted power regulation in the electricity supply system. If these resources are designed to operate in island mode, the regulation of them is directly necessary. Control of the three-phase voltage inverts is fundamentally the same as the control of synchronous generators, which allows managing voltage and frequency and inject into the network power values which correspond to a the actual change of the load. In the distribution systems usually as frequency as voltage are influenced by active power as well as reactive power. The share of the individual performance is determined by the impedance ratio (R/X) in the given part of network. Therefore, instead of the traditional characteristics, there are used so called the virtual methods. The paper deals with the frequency regulation possibilities of PV generators by primary frequency and secondary control, using the virtual power method during the microgrid island mode. These possibilities are presented by model examples in MATLAB, Simulink software. Simulation results showed that the frequency and voltage values stayed during any load changes in the limit range due to primary control. The activation of the secondary control will restore their nominal values and there is possible to use this method for PV generator regulation.