A Model Predictive Voltage Control using Virtual Space Vectors for Grid-Forming Energy Storage Converters

Sinusoidal output voltages with low harmonic distortion can be achieved using three-level converters along with LC filters, which have been proven to be suitable for energy storage systems (ESSs). Model predictive control (MPC) has been applied to such energy storage converters due to its simplicity and effectiveness. However, selecting the weighting factor of the additional neutral-point (NP) voltage balancing term in the cost function is time consuming and may also affect the main objective of MPC. To address this issue, in this paper, additional virtual space vectors (VSVs), which do not affect the NP capacitor voltages, are adopted in the proposed MPC. Both simulation and experimental results using controller hardware-in-the-loop are presented to show that NP capacitor voltages can be well controlled using a particularly small NP voltage balancing weighting factor in the cost function. In addition, the total harmonic distortion of the voltage at the point of common coupling is reduced while retaining the fast dynamic response of MPC.