High Efficiency High Power Density Isolated Matrix-Type Rectifier for Telecom and Data Center Applications

Jahangir Afsharian

doi:10.32920/ryerson.14649273.v1

Abstract

With the fast development of information technology (IT) industry, the demand and market volume for off-line power supplies keep increasing, especially those for telecommunication, computer servers and data centers. As the capital expenditure was measured by the square footage occupied rather than power consumption, the development of high power density converter system is of greater interesting. The rising energy prices have resulted in the cost of power and cooling exceeding the purchase cost in less than two years. Therefore, highly efficient power conversion is required for the power converter system. Generally, the power supply unit (PSU) for power distribution system (PDS) in data center and telecom are the standard two-stage approach which normally consists of power factor correction (PFC) circuit and isolated DC-DC converter. The two-stage power conversion has demonstrated excellent performance and high reliability, since the design can be optimized for each stage. However, limitations to prevent the existing two-stage PSU to fulfill future requirements for the PDS in data center and telecom applications are revealed, and a very promising and fundamentally different approach with the single-stage isolated converter is proposed in this dissertation. The development of single-stage converters with the option of placing the energy storage outside of the PSU creates new degrees of freedom regarding e.g. simplified rectifier racks in telecom and data center. This provides tangible benefits in the form of space saving, better airflow for power unit in rectifier racks and improved lifespan. The three-phase isolated buck matrix-type rectifier, capable of achieving high power density and high efficiency, is identified as an excellent candidate for the medium power level (5 kW~10 kW) single-stage power supply design. Nevertheless, the matrix-type rectifiers are known for their relatively complex modulation and commutation techniques, and lack of ride-through capability such as the stringent case of one phase loss operation. This dissertation work provides comprehensive study on the commutation method and modulation scheme design for the isolated buck matrix-type rectifier. It aims to analyze the operation principle of the rectifier and propose viable modulation and commutation schemes for this rectifier under both three-phase and single-phase operation. The method is verified by the hardware experiments of the PSUs with high efficiency (> 98%) and high power density (> 70 W/in3 ) for 54 V and 380 VDC applications. The prototypes demonstrated in the experiments show the effectiveness of the proposed modulation and commutation schemes for industry.

Highlights

With the explosive development of information technology, the communication and computing systems, such as data centers, telecoms, and servers have become a large market for the power supply industry
It is shown that the proposed six-segment PWM scheme (“Type A”) is the optimal PWM scheme for the MOSFET devices employed for bidirectional switches in the isolated buck matrix-type rectifier
The output voltage drop of the rectifier and the required upper limit of the average output inductor current for one phase loss operation is studied for two cases: “case 1” applying three-phase PWM scheme such as “Type A” to one phase loss operation and “case 2” with desired PWM scheme proposed for one phase loss operation

Summary

Introduction

With the explosive development of information technology, the communication and computing systems, such as data centers, telecoms, and servers have become a large market for the power supply industry. The rest of the power is lost in power conversion, distribution, and cooling, resulting in high utility bills, a large environmental footprint and the inability to fill equipment racks [1]. Over the past decade energy efficiency and power density have become the top concerns for power conversions in data center and telecom. The demand for compact power supply unit (PSU) grows significantly It requires PSU with high efficiency, low profile and high power density. The power supplies for power distribution system in data center and telecom are the standard two-stage approach [5, 6, 7, 8]. The cost for this type of approach is high due to relatively large number of components to accomplish the required functions of the front-end converters

Objectives

Results

Discussion

Conclusion