A Virtual Inertia Control Strategy with Current Feedforward to Improve Voltage Stability for Power Router

The power router (PR) based on power electronic technology is the core equipment of the energy internet (EI). For the PR, the common direct current (DC) bus structure is drawing more and more attention, in which the DC voltage stability is of vital importance. In the PR with the energy storage system (ESS), the DC/DC converter of ESS has significant effects on the DC bus voltage stability. Droop control is commonly used in the control of DC/DC converters in ESS. However, conventional droop control fails to provide the inertia to meet the demand for voltage stability. Hence, a virtual inertia control strategy with load current feedforward is proposed in this paper to strengthen the voltage stability. Firstly, the small-signal model of ESS is derived to find out the key factors that affect the DC bus voltage stability. Secondly, based on the analysis, an inertial droop control strategy is presented to provide inertia to the DC bus voltage, while a load current feedforward method is proposed to improve the voltage response performance during load transients. The stability analysis is also carried out to guide the controller designing. The validity of the proposed control strategy has been verified by the results from both MATLAB/Simulink and hardware-in-the-loop (HIL) simulation.