Oversampling Multi-Variable Control for Soft-Switching Solid-State Transformer

This paper presents two oversampling based control methods for a multiport low-inertia current-source soft-switching solid-state transformer (S4T). The traditional duty cycle or model predictive control calculates the reference currents and the duty cycle for each port, requiring accurate model prediction and sophisticated control design to balance the input and output power on a per cycle basis. To reduce the computational burden and enable the use of a simpler and more cost-effective microcontroller, two oversampling based control methods are proposed. This type of control exhibits unusual properties, such as unequal switching frequencies at individual ports and across the high frequency transformer. The proposed methods can be extended to cover more ports, simply by adding states in the state machine, thus demonstrating multi-variable control. These methods show promise in the implementation of control for very low-cost multiport converter systems.