Research on Power Semiconductor Filter Technology for Power Factor Correction


Student thesis: Doctoral Thesis

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Award date23 Jun 2020


Power electronics has become an integral part of our daily lives. It is used in various industries such as automotive, consumer electronics, and aerospace and defense. The primary functions of a power electronic system is to convert and regulate electrical energy from one form of power into another by using solid-state electronic devices. It is estimated that by 2030, up to 80% of the electricity generated will be reprocessed or recycled through some form of power electronic system.

Therefore, the number of electrical devices continues to increase and thus increase the energy consumption from the distribution network. The input characteristic of those devices is dominantly non ideal and nonlinear that will greatly increase line current harmonics. Hence, the devices can increase the burden and reduce the utilization of the power distribution system, such as overheating problems in power transformers and the requirements for higher VA ratings of components. These may ultimately affect the stability of the distribution system. Hence, many countries have set out statutory power quality requirements for those devices.

Reducing the current harmonics generated by grid-connected equipment can highly maintain high input power quality. Power factor corrector (PFC) is one of the key power processing elements in the AC grid environment. It can maintain good input power quality regardless of the type of load. It provides an input current curve in phase with the grid voltage with low current harmonic distortion. By using PFC as the front-end power supply of the equipment, the utilization rate of the power distribution system can be improved and the rating requirements in the power system design can be released. This is because the peak VA required for specific active power transmission is reduced, which also means lower current harmonics. In addition, the thermal problem of the power element due to the reduction in the ratio of the harmonic current is improved. The rating of the components in the power supply has also been reduced.

In recent decades, PFC-related technologies have been widely studied and used in higher power quality power systems. The research areas include topology research, control system design, and design optimization. In order to further promote the development of this field, this paper presents research results on power factor correction technology, topology, and the use of power semiconductor filter (PSF) technology to control switching power supplies. It is based on the characteristics of configuring a low harmonic content input current by connecting a series pass device (SPD) at the input terminal of the switching converter. Unlike the traditional PFC operating principle, the PSF limits the input current amplitude without fluctuations, instead of using only high-frequency switching currents to describe the waveform and phase. As a result, the newly introduced technology can be integrated into a single chip and provide a smaller and lighter solution for input filtering. In addition, the operating point of the SPD is adjusted between the linear and saturation regions of a bipolar junction transistor (BJT) or between the triode and ohmic regions of a MOSFET ("knee"). Therefore, power consumption on the SPD can be minimized. Further, the small signal models of the converters that are implemented PSF technology for power factor correction are also studied for stability issue. Therefore, the design guideline for the particular feedback controllers can be established.

Throughout the research, the basic concept of using a single series device (SPD) in a PFC switching power supply has been proven and evaluated. Then, technologies with improved performance that utilize low-voltage devices in high-voltage applications using high-voltage barrier structures have been developed. This opens up new space for further optimization of PSF technology. Finally, the use of low-voltage devices in high-power PFC only proves the new potential of PSF in high-power applications, and its power consumption based on bidirectional power conversion is reduced. This brings the possibility of monolithic integration of PSF technology in the future.