Dynamic maximum power injection control of AC photovoltaic modules using current-mode control

Maximum power point tracking (MPPT) strategies are an essential part of photovoltaic (PV) power converters´ control. These algorithms maintain the operation of the PV panel at the optimal point for maximum performance. In addition, the power converter must synchronise with the electricity grid and inject the power extracted from the PV panel. These two tasks are executed by the controller in the power conditioning unit. This, however, results in complicated control loops. Moreover, the interaction with the grid may cause stability problems in the power converter during voltage disturbances. The dynamic control of PV modules connected to the electricity supply presented by the authors provides a substantial improvement in power converter stability and ease of implementation. This strategy combines grid power injection control and PV MPPT into a single control block. The first objective is achieved using current-mode control to shape the current injection whereas the latter objective exploits the dynamic behaviour of the PV panel to determine changes in the grid current magnitude. An implemented prototype system shows the performance of the proposed strategy and the results are compared against commercially available inverters.