Page 51 - PEN eBook May 2023

DESIGN DESIGN

Figure 1: Grid-connected energy-storage elements are critical to future power T&D.

Storage is also increasingly used to balance out INTEGRATING BESS WITH MV GRID
intermittent power supplies from renewable-energy A battery energy storage system (BESS) is integrated
resources like wind and solar. to an MV grid (2.3 kV, 4.16 kV or 13.8 kV) using an
isolated topology like a dual active bridge (DAB) Figure 2: System topology for interconnecting the BESS system to an MV grid
SiC DRIVES STORAGE INNOVATION followed by an active front-end converter. A three-level
Use of all-SiC inverters will revolutionize electricity (neutral-point–clamped) topology reduces both the
delivery, renewable-energy integration and energy filter requirements compared with a two-level topology requirement for a very low isolation capacitance in the Using MV 3.3-kV SiC MOSFET diodes in place of
storage. It is well recognized that silicon-based and the voltage stress across the SiC MOSFETs. gate-drive circuit. Power transmission stage design series-connected lower-voltage (1,200 V or 1,700 V)
semiconductors have inherent limitations that reduce Depending on grid voltage, a series connection of objectives are high isolation requirements, low coupling MOSFETs or IGBTs has tremendous advantages,
their suitability for utility-scale applications. With SiC, the SiC 3.3-kV MOSFET diode devices is possible, as capacitance and optimized gate-driver footprint. In including simpler gate driving, reduced parasitic
however, power electronics applications including static shown in Figure 2. Additional topologies can also be general, MV applications require series connection of inductance associated with replacing multiple
transfer switches, dynamic voltage restorers, static var considered for analysis. The low-voltage (LV) side is devices for redundancy and high operating voltages. lower-voltage transistors and rectifiers with a single MV
compensators, high-voltage direct-current transmission made through 1,200-V SiC devices. In the DAB, the MV Series connection of MV SiC devices requires gate device, lower conduction losses and higher efficiency.
and flexible alternate-current–transmission systems all transformer (LV to MV conversion) can be operated drivers that can switch all devices simultaneously. Overall size, weight and cooling requirements of the
become economically feasible. With SiC, between 10 and 20 kHz. A single-phase or a Delay in turn-on of the series-connected devices may power converter can therefore be significantly reduced.
medium-voltage (MV) inverter manufacturers can three-phase system can be used depending on the result in voltage mismatch, leading to overvoltage or
realize efficiencies of >97.8% at 100 kW to 1 MW, power requirements. improper voltage sharing across devices. Tests of circuit efficiency and maximum junction
allowing more compact inverters to be deployed temperatures on a 3.3-kV/400-A GeneSiC SiC MOSFET,
at large scale across residential and industrial The MV SiC MOSFETs’ fast-switching transients can
implementations. result in a dV/dt as high as 100 kV/µs, imposing a

Figure 3: Third-quadrant I-V characteristics measured on 3.3-kV, 40-mΩ, discrete SiC MOSFET (left) and SiC MOSFET with
monolithically integrated MPS diode (right)

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