The UPS market is anticipated to expand dramatically during the next few years. The key driver behind this expansion is the requirement for creating a datacenter infrastructure that can provide a high level of efficiency in order to reduce the expenses associated with the supply of electricity. The global economy is becoming more digitalized, and there have been significant investments made in new datacenters that can meet the rising demand for cloud-based services. The UPS (Uninterruptible Power Supply) is an important element in this scenario, as it prevents any failure or interruption of the mains voltage from having an effect on a company’s everyday operations.
Datacenters must have redundant power supply and ensure complete continuity of electricity in order to operate at peak efficiency 24/7. One of the key goals of every business owner and manager is to increase the data center’s PUE (Power Usage Effectiveness). In this article, we will examine how, in comparison to conventional silicon-based power devices, SiC technology provides appreciable advantages in terms of energy efficiency and not only that.
UPS components
A reliable, continuous power supply is required in a datacenter, just like in any other site where high technological devices are operating. VFI (Voltage and Frequency Independent) UPS systems are typically employed to fulfill this need.
A typical VFI UPS includes an AC-DC converter (rectifier), a DC-AC converter (inverter), and a DC-link. A bypass switch is typically used during maintenance to directly link the UPS output to the AC voltage source at the input. We’ll learn later that this connection is also utilized in “eco-mode,” a particular and unique operating mode. The battery, which is typically made up of many cells, is attached to a buck or boost converter and is responsible for supplying power in the case of a mains power failure. Regarding the technical specs, we can say that a middle-class UPS offers output power of several hundred kVA, output current of several hundred amperes, nominal voltage of three-phase 480V, and frequency of 50/60 Hz.
One of the most common UPS architecture is the double conversion type, where the alternating voltage at the input is first transformed into direct voltage and then again into a perfectly sinusoidal alternating output voltage (hence its name). The result is the elimination of any supply voltage variation, enabling the UPS to provide the load with a steady and clean signal. The system is separated from the power source during the voltage conversion process, shielding the load from any potential power spikes or power drop. Up until recently, IGBT transistors with 3-level switching topologies produced the best efficiency performance. That technology, capable of achieving 96% efficiency, has long been considered a notable advance over earlier UPS models that were still relied on transformers.
Active standby mode
With this operating mode, also known as “eco mode” or “multi-mode”, the inverter and the rectifier circuits are kept in a “offline” condition or, in any case, are not a part of the common power path. As a result, in typical circumstances, the load is powered directly by the mains voltage. Therefore, the “bypass” path corresponds to the power path used when eco-mode is enabled.
The UPS continuously monitors the “healthy status” of the incoming supply voltage, and in the event of an interruption, it automatically activates the “online” power path, which consists of the double conversion circuit. In order to pursue greater efficiency, this mode has been designed to limit power absorption. That means that inverters and rectifiers are only switched on in the event of a real failure. However, it should be emphasized that this improvement is quite marginal (about 1%), and many data center operators still favor the conventional approach in which the right supply is consistently ensured to the load without any interruption.
How SiC improves UPS
In recent years, the use of SiC-based transistors in UPS power stages has allowed for a significant increase in efficiency, with values above 98% and practically independent of the proportion of load utilization. The typical efficiency curve of a commercial UPS built around SiC power devices shows that the efficiency keeps remaining above 98% following a nearly flat curve for load utilization percentages greater than 30%.
The physical and electric properties of wide bandgap semiconductors (WBG), to which silicon carbide belongs, make it possible to achieve this kind of results. WBG semiconductors can operate at higher temperatures, frequencies, and voltages than conventional silicon-based devices like MOSFETs and IGBTs. Up to 70% less power is lost in SiC-based devices, resulting in efficiency values that are independent of load and are equivalent to, or higher, than 98.6%. Better thermal management (or heat dissipation), which in turn enables operation at higher temperatures, is another advantage of SiC-based UPSs. This feature enables designers to use cooling systems that are more efficient and smaller. Overall, compared to a comparable model with silicon-based components, a SiC-based UPS is more effective, lighter, and smaller.
