Study of a Three-Phase Boost AC to DC Converter with Fixed Switching Frequency

• Main Authors: Chiang-nan Chen, 陳江男
• Other Authors: Tien-Chi Chen
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/58vscn

碩士 === 國立成功大學 === 工程科學系碩博士班 === 90 === Because of the need for a unity power factor and reducing the line current harmonics, the traditional diode rectifier is ineffective at the higher standard. The boost AC to DC converter has therefore been developed. The common control theorem method is hysteresis current control (HCC). This method has the advantages of simple implementation and design. The input current is kept within a hysteresis band about the reference current wave to reach the unity power factor. The HCC dynamic response to load variations is fast. However, the major problem in HCC control is that the switching frequency varies with the DC load current. At heavy loads the frequency increases substantially. The switching frequency is uneven and random, causing excessive stress and switching losses on the devices. The input filter is also difficult to design. In this thesis, a switching algorithm that uses a fixed switching frequency for a three-phase boost AC-DC converter is proposed. Using this switching algorithm the input current waveform can be controlled close to a sinusoidal template that is derived from the input voltage waveform. This converter has the advantages of a unity power factor, the current response is kept fast and the filter is easier to design. The switching algorithm uses the principle of one voltage vector used in one switching period. The switching count for this device is therefore greatly reduced. The stress and losses in the switching devices are substantially reduced. A relationship between the current error, switching frequency and boost inductor was developed in this thesis. The current error can be restricted within a definite range using an appropriate switching frequency and boost inductor. The proposed scheme was implemented using a 32-bit digital signal processor TMS320C32, analog to digital converter and digital to analog converter. The simulations and experimental results demonstrate the feasibility of this control system.