Integrating 10-kV SiC MOSFET Into Battery Energy Storage System With a Scalable Converter-Based Self-Powered Gate Driver

Abstract

In the hardware design of Battery Energy Storage System (BESS) interface, in order to meet the high voltage requirement of grid side, integrating 10 kV Silicon-Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) into the interface could simplify the topology by reducing the component count. However, the conventional gate driver design is challenging and inextensible in BESS, since the high voltage rating and high dv/dt bring the requirements of high voltage isolation and low common-mode capacitance. Therefore, in this paper, a scalable converter-based self-powered (SCS) gate driver is further proposed. A 5 kV-input power extracting converter based on a voltage-balanced SiC MOSFET stack is constructed to self-power the gate driver, which exhibits simplification of basic topology and sufficient gate driver power handling capability regardless of the switching requirement of main loop power device. Besides this, the power extracting converter is designed to act as a clamping Resistor-Capacitor-Diode (RCD) snubber circuit, which makes the SCS gate driver scalable to the series connection of power devices. Analysis and design consideration are given in detail, followed by the experimental verification using 10 kV/10 A SiC MOSFETs.

Voltage Balancing of Series-Connected SiC mosfets With Adaptive-Impedance Self-Powered Gate Drivers

“…Further, different from conventional external-powered GDs, the selfpowered GDs partially recycle the energy of "snubbers" (the power extracting parts which extract and absorb the energy from the power loop) to supply the gate driving parts, which eliminates the need of external auxiliary power supply configuration. Beside this, the design burdens related to voltage isolation and common mode noise are eased drastically [26].…”

“…When T P is turned off after a constant on-time duration T on , i P(i) decreases to zero rapidly and the stored power of the primary side is transferred to the secondary side. The secondary voltage limiting circuit and the following gate driving part will consume the transferred power so that the energy stored in this "snubber" will not get accumulated [26]. Therefore, by integrating v C(i) •i P(i) over time and combining it with (3), the extracting power p (i) (i = 1, 2) from power loop can be obtained as:…”

“…As for other parts such as the voltage limiting circuit in Fig. 5, their detailed descriptions have already been provided in [26]. Since this adaptive-impedance self-powered GD does not involve any closed-loop control, its optimized passive "snubber" characteristic makes it attractive if a less control complexity is expected in series connection.…”

“…As for the potential dip of DC bus voltage when the system is running, two approaches can be adopted to ensure the safety: (1) from the power side, vC(i) can be sampled by the controller, and once the tolerable lowest voltage threshold is reached, the controller will force the output PWM to be "low"; (2) from the gate driver side, the under-voltage detection function can be integrated into the gate driver part, once its input voltage (v out ) is below the threshold, an "error" signal will be sent to the controller and the output PWM is forced to be "low" immediately. Another issue exists during the system startup [26] Voltage limiting circuit [26] k‧v C(i) + - process when v DC is gradually increasing to the working voltage from zero. Before v C(i) reaches the startup voltage threshold, the input impedance of this proposed "snubber" is determined by the resistor divider as depicted in Fig.…”

“…In response to those issues, as a continuation of the previously published article where a scalable self-powered GD design was proposed for SiC MOSFET [26], this article makes two major contributions as follows:…”