Virtual Impedance Concept to Decouple P/Q of Distributed Generation Systems.
Distributed Generation, Power Flow Control, Voltage Mode, Virtual Impedance.
The distributed generation systems based on renewable sources has increased due to environmental problems caused by non-renewable sources, fast return on investment and advances in interconnection systems. In Brazil, the distributed generation energy capacity is growing. Before a new electric power system model, distributed generation systems participation, methods to regulate the power flow in generation units can directly contribute to electric system stability, especially in low-voltage grids, which is the predominantly resistive and the active power can cause overvoltages. In addition, power flow strategies used in conventional generation systems cannot be used in low-voltage systems due to active and reactive power coupling. In this work is proposed the power flow control adjust in a distributed generation photovoltaic system controlled in voltage mode based on virtual impedance concept. In order to overcome the active and reactive power coupling problem, the proposed method is implemented by means a virtual resistor. For analysis purposes, the virtual resistor is implemented by two ways. In the first one, a positive virtual resistor is implemented to accentuate the resistive profile of the system, performing the P/V and Q/θ control. In the second one, a negative virtual resistor is implemented in order to make the network profile predominantly inductive, and then perform the traditional P/θ and Q/V control. The virtual impedance concept technique is evaluated through simulation and experimental results.