Advanced control of a converter used for connection of photovoltaic modules

This paper presents a control algorithm for a voltage source converter (VSC) that is used for connection of photovoltaic (PV) modules. The algorithm enables decoupled control of the PV generation system active and reactive power. Moreover, it enables the operation with unbalanced voltages. In case of unbalance, the negative-sequence currents are regulated to zero and the reference active and reactive power are maintained constant. The algorithm therefore extends the functionality of a PV generation system. Besides delivering the PV modules active power to the network, the PV system gains the functionally of VSC based active compensators. Such PV system could be used, for example, for voltage support or for power factor correction. For the evaluation of the proposed algorithm a PV generation system model is developed in PSCAD. The algorithm shows a good dynamic response and stable operation also in the case of relatively deep voltage sags.