MV SiC Based Power Conditioning Systems

As of 2020, the US has over 100 MW of wind energy capacity installed into the electric grid. In Europe, wind energy accounts for more than 44% of all new power installations, representing 11% of Europe’s total electricity demand. Installations all over the world are expected to increase at an exponential rate, driving the need for higher efficiency and lower cost systems. One method to address these needs is to make ever larger electric machines that are more cost effective to manufacture and maintain. As an example of this, GE recently installed the Halidate-X wind turbine, the largest of its kind rated at 12 MW. However, this turbine system still utilizes legacy low-voltage (LV) silicon (Si) based devices for the power electronic interface between the wind turbine and the utility grid. Furthermore, galvanic isolation between these components is still realized with century old 60 Hz transformers. To truly enable significant installation potential of offshore wind energy systems, a more power dense, lightweight, and cost-effective power electronic conversion system (PCS) is required. The goal of this proposal is to develop a medium voltage (MV) silicon carbide (SiC) based PCS capable of interfacing to >69 kV utility grid and emerging MW scale wind turbines. To this end, RCT Systems (RCT) proposes utilizing a MV SiC building block that we are currently developing for the US Navy, to be used in shipboard power distribution equipment. The naval building block is composed of a 10 kV SiC based AC-DC converter on the high voltage interface. This converter then interfaces to a 10 kV and 1.7 kV based zero-voltage-switching DC-DC converter that provides galvanic isolation and a regulated output voltage. These building blocks will be utilized to develop the >69 kV grid interface (series stacked CHB building blocks), for a power rating of >3 MW per phase, for a total power rating of >10 MW. The proposed converter architecture can be further scaled for varying interface grid voltages (>69 kV), wind turbine interface voltages (13.8 kV), or power levels through a multi-tap transformer and scaled converter architecture. Wolfspeed will supplying the MV SiC modules. RCT has also partnered with Prof. Andrew Lemmon of the University of Alabama (UA), who has unique expertise in EMI effects of MV SiC devices, modules, and systems. Phase I will consist of detailed electro-thermal modeling of the proposed three-stage PCS, including initial CAD layout, MV insulation system design, and thermal system design. UA will develop/provide RCT with MV SiC device, module, and system models for use in RCT trade studies. GE will provide interface specifications/requirements for the PCS. Elimination of bulky 60 Hz transformers and the simplification of power electronic topologies will reduce the cost and size of this critical component of offshore wind turbine systems, in turn reducing the cost and footprint of the entire system, or allowing for greater capacity in the same footprint. The use of this power electronics building block will also be useful for distributed energy sources such as grid-tied energy storage systems and/or solar power systems, both of which require this type of converter to interface their generated output to the utility grid.