Research on DC Side Voltage Fluctuation Suppression Strategy of Energy Storage Converter Under Unbalanced Grid Voltage Condition

In renewable energy conversion systems, energy storage converters are widely used. However, the dc side capacitor voltage fluctuation caused by grid voltage imbalance will have an effect on the normal operation of the converter. A novel predictive direct power control strategy, which relies on a computational compensation model, is introduced for the reduction of voltage fluctuations on the direct current side of energy storage converters under conditions of an unbalance grid voltage. Compared to the method of separating the positive and negative sequences, this method can simplify the algorithm by using the sampled values of the mains voltage, current & imbalance coefficient to calculate the power compensation value within the DQ frame. By modifying the cost function, the double-frequency component can be suppressed. The presented control strategy is confirmed through simulation and experiment, which can effectively suppress dc side voltage fluctuation.