Bench Talk

(Source: Emanuel / stock.adobe.com; generated with AI)

Picture a bustling city on a sweltering summer evening, with air conditioners at full output while electric vehicles are charging for the next day’s activities. As power demand surges, there's a threat of brownouts, but fortunately, these can be averted in part thanks to the availability of battery energy storage systems (BESS) (Figure 1).

Figure 1: Battery energy storage systems for capturing the output of solar arrays and other sources can be sited indoors or outdoors and configured as single or multiple modular transportable units. (Source: scharfsinn86/stock.adobe.com)

These trailer-size units store generated electrical energy from conventional and intermittent renewable sources during surplus generation periods, then give it back to the grid as needed, functioning as a peak-demand power reservoir.

Multiple features make BESS attractive:

• High energy density and high efficiency when storing and delivering power
• Modular and easily transported
• Adjustable to different power grid needs and installation sites—outdoor or indoor
• Scalability in total size and capacity
• Low maintenance and downtime needs
• Quiet and emission-free

As this technology continues to make its impact on smart grid applications and more, it is vital that energy solutions match their progress. This blog examines how silicon carbide (SiC) power modules advance BESS, focusing on their efficiency, scalability, and system reliability features, and considers versatile power modules from Wolfspeed.

SiC Strengthens Switch Technology

The practicality of implementing a BESS design is due to several factors. First, of course, there is an increasing need for the function it provides, especially when used in conjunction with intermittent energy sources. However, demand alone is not enough, as it also requires electronic components ranging from basic passive connectors and circuit protection devices to the active power-switching devices needed to transform the stored DC energy into useful power.

Increasingly, among those components is the power-switching device based on SiC technology. SiC features multiple superior attributes compared to existing devices based on silicon only.

It has a far higher breakdown voltage and a wider bandgap energy than silicon. This allows SiC components to operate at higher voltages while exhibiting lower leakage current and enhanced efficiency in high-power applications. Its higher thermal stability and conductivity (~3.7W/cm·K vs. 1.5W/cm·K for Si) allow SiC devices to be used at junction temperatures exceeding 200°C in some cases, thus requiring smaller heatsinks. However, actual temperature limits depend on device design and manufacturer specifications. In addition, SiC features lower conduction losses due to its lower on-state resistance (R_DS(on))—typically 2 to 3 times lower than silicon-based devices at high voltages. Finally, SiC can operate at switching speeds up to 5 to10 times faster than silicon IGBTs, resulting in significantly greater operation efficiency.

Wolfspeed’s Innovation Makes a Difference

Even a superior SiC device is not a “drop-in” power device in its final application. A complete power-conversion design requires careful attention to layout, substrate, support components, thermal management, and various other considerations. For these reasons, a complete and ready-to-use power module is a desirable option for potential customers planning to use SiC devices.

That’s why Wolfspeed’s WolfPACK™ silicon-carbide power modules are a breakthrough technology for energy storage systems and more. The 2300V baseplate-less SiC power modules for 1500VDC-bus applications were developed and launched using devices fabricated on Wolfspeed’s state-of-the-art, 200mm silicon carbide wafers (Figure 2), enhancing yield and reducing manufacturing costs.

Figure 2: The 2300V baseplate-less SiC power modules for 1500VDC-bus applications were developed and launched using Wolfspeed’s state-of-the-art 200mm silicon carbide wafers. (Source: Wolfspeed)

The benefits of these power modules are clear: they improve system efficiency, increase system power density, reduce the number of passive components, and reduce overall system cost. As a discrete design consolidated into a single package, it also includes a negative temperature coefficient (NTC) thermistor to ease the measurement of module temperature.

These WolfPACK modules are available in half-bridge, six-pack, and T-type configurations, with half-bridge modules currently released for 2300V (Figure 3). All modules offer the option of pre-applied thermal interface material. This technology achieves a 77 percent reduction in switching losses over IGBTs and a 2 to 3 times reduction in switching losses when compared to other available silicon carbide devices intended for 1500V applications. The 2300V half-bridge configuration is currently available in a compact package with a footprint of approximately 57mm × 63mm and a 12mm height.

Figure 3: The Wolfspeed CAB5R0A23GM4, a 2300V, 5.0mΩ silicon carbide half-bridge module (left), offers device integration, including a built-in thermistor (represented in the schematic on the right). (Source: Wolfspeed)

This technology supports power modules as building blocks for highly modular, flexible system implementations to ease scaling up to larger installations. Scalability is delivered through design simplification, resulting in easily maintained mass-produced systems that can be rapidly deployed. This allows designers to leverage lower cost printed circuit boards (PCBs) to reduce manufacturing costs and significantly reduce development time compared to legacy solutions.

Wolfspeed’s 2300V modules support a two-level topology for a simplified system design and reduced number of gate drivers compared to IGBT-based three-level configurations. When used in a two-level implementation, these modules reduce the amount of potential failure points across the system. Designers using the modules get in-depth support from tools, including Spice and thermal models, interface and driver details, mounting specifics, application notes on thermal management, parasitics, EMI considerations, and more.

Proven Performance in Next-Generation Renewable Energy Systems

The benefits of Wolfspeed’s modules are already disrupting the industry. For example, Wolfspeed is partnering with EPC Power, a leader in power conversion solutions, launching their M system, a next-generation renewable power inverter platform designed to optimize energy storage at the grid level.^[1]

Based on the Wolfspeed 2300V WolfPACK power modules, this system offers unmatched flexibility with its modular construction, allowing configurations ranging from a single 5.3 megavolt-amp inverter block to 10 independent 537 kilovolt-amp inverters. Its innovative architecture is designed to streamline production, reduce footprint, and maximize profitability by delivering the highest levels of reliability, availability, and efficiency.

Wolfspeed’s SiC solutions are helping bridge the clean energy gap, accelerating the next era of modern energy technologies while reinforcing US manufacturing leadership in this area. As pioneers in SiC, they are creating solutions to facilitate a new era of modern energy sourcing and delivery. Energy efficiency, reliability, and scalability are top of mind for Wolfspeed, who recognizes the substantial advantages that silicon carbide modules offer.

Author

Bill Schweber is a contributing writer for Mouser Electronics and an electronics engineer who has written three textbooks on electronic communications systems, as well as hundreds of technical articles, opinion columns, and product features. In past roles, he worked as a technical website manager for multiple topic-specific sites for EE Times, as well as both the Executive Editor and Analog Editor at EDN.

At Analog Devices, Inc. (a leading vendor of analog and mixed-signal ICs), Bill was in marketing communications (public relations); as a result, he has been on both sides of the technical PR function, presenting company products, stories, and messages to the media and also as the recipient of these.

Prior to the MarCom role at Analog, Bill was associate editor of their respected technical journal, and also worked in their product marketing and applications engineering groups. Before those roles, Bill was at Instron Corp., doing hands-on analog- and power-circuit design and systems integration for materials-testing machine controls.

He has an MSEE (Univ. of Mass) and BSEE (Columbia Univ.), is a Registered Professional Engineer, and holds an Advanced Class amateur radio license. Bill has also planned, written, and presented online courses on a variety of engineering topics, including MOSFET basics, ADC selection, and driving LEDs.

[1] https://www.wolfspeed.com/company/news-events/news/wolfspeed-unveils-cutting-edge-silicon-carbide-module-solution-to-boost-clean-energy-capacity/