Phase-shifting rectifier transformer – an important supporting role in high-voltage inverters
06-02 2025 | By:
One of the biggest advantages of the high-voltage inverter (structure shown in Figure 1) using power unit series multi-level technology is the use of phase-shifting transformers to achieve input multiplexing and reduce input harmonics.
Phase-shifting rectifier transformer
The phase-shifting transformer has three functions:
① to achieve phase shifting of the primary and secondary line voltages to eliminate harmonics.
② to transform the required second ary voltage.
③ to achieve electrical isolation between the rectifier and the power grid. In this paper, the author studied the phase-shifting technology, multiple rectification technology and harmonic analysis of the phase-shifting transformer! .
For a clear understanding, the following assumptions are made.
(1) The phase-shifting transformer is an ideal transformer without the influence of impedance and leakage reactance.
(2) Power electronic devices such as diodes are ideal devices without switching time, etc.
(3) LC filtering is used on the DC side after rectification, and it is assumed that the filter inductance L is large enough and the DC current is a constant value.
2 Phase-shifting transformer extended triangle phase-shifting technology According to the different connection methods of the windings, the phase-shifting transformer is divided into two types of transformers: forward extension and reverse extension. That is, the phase of the transformer secondary winding line voltage leads or lags the primary winding line voltage by an angle .
Advantages of phase-shifting transformer
In the field of high-voltage frequency conversion, the frequency conversion speed regulation device is a perfect harmonic-free high-voltage frequency conversion device. The rectifier transformer in the device is an indispensable and important component. The rectifier transformer belongs to a multi-winding phase-shifting rectifier transformer. The use of phase-shifting rectifier transformer can effectively eliminate the harmonic pollution of the inverter to the power grid, making the design of high-voltage inverter more flexible.
In the case of three-phase voltage of the power grid, a multi-phase rectifier circuit is used, and the low-voltage DC side output after rectification has a better waveform and less harmonic components.
The phase-shifting transformer is equivalent to 48 pulses. Theoretically, 47 harmonics can be offset, so the output waveform of the frequency conversion device will not cause resonance of the motor. It complies with IEEE5191992 and the most stringent requirements of China’s power supply department for voltage distortion, which is higher than the national standard GB14549-93’s requirement that harmonic distortion should not exceed 4%.
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