CN-122001227-A - Three-phase DCDC converter and rectification control method thereof

CN122001227ACN 122001227 ACN122001227 ACN 122001227ACN-122001227-A

Abstract

The invention discloses a three-phase DCDC converter and a rectification control method thereof, which relate to the field of switching power supplies and comprise a three-phase inverter circuit, a three-phase resonant isolation circuit and a three-phase rectification circuit which are sequentially connected, wherein an upper bus capacitor and a lower bus capacitor which are connected in series are connected between two output ends of the three-phase rectification circuit, each phase rectification circuit comprises four communication states, namely a positive output end is communicated, a grounding end is communicated, a midpoint between the upper bus capacitor and the lower bus capacitor is communicated, and the three-phase DCDC converter is in a no-current state. The invention can widen the output voltage range and provide a transient high-gain or transient high-voltage output state.

Inventors

YIN XIANGYANG
Yin Zenghe
YUAN YUAN
HE LEI

Assignees

广州金升阳科技有限公司

Dates

Publication Date: 20260508
Application Date: 20251231

Claims (6)

1. The three-phase DC converter comprises a three-phase inverter circuit, a three-phase resonant isolation circuit and a three-phase rectification circuit which are sequentially connected, wherein the three-phase rectification circuit comprises a first phase rectification circuit, a second phase rectification circuit and a third phase rectification circuit which are respectively connected with three-phase output of the three-phase resonant isolation circuit and are used for converting three-phase alternating current transmitted by the three-phase resonant isolation circuit into direct current output; The three-phase DCDC converter comprises three working states: one phase of current in the three-phase rectifying circuit is larger than zero, and the other two phases of current are smaller than zero; the second state is that one phase current in the three-phase rectifying circuit is smaller than zero, and the other two phases current is larger than zero; a third state, wherein one-phase current in the three-phase rectifying circuit is larger than zero, one-phase current is smaller than zero, and one-phase current is equal to zero; When the three-phase DCDC converter works, the communication state of each phase of rectifying circuit is controlled through a switching tube, the upper bus capacitor and the lower bus capacitor are charged simultaneously or independently, so that the output voltage of the three-phase rectifying circuit is controlled, the three-phase DCDC converter periodically rotates between the first state and the second state in the same working period, or the three-phase DCDC converter periodically rotates between the first state, the second state and the third state in the same working period, and the output voltage gain of the three-phase rectifying circuit is regulated through the action time of the third state.
2. The three-phase DCDC converter of claim 1, wherein the three-phase rectification circuit is composed of three-phase diode clamping three-level bridge arms, each phase rectification circuit comprises a first active switch tube, a second active switch tube, a first diode, a second diode, a third diode and a fourth diode, wherein the first diode, the first active switch tube, the second active switch tube and the fourth diode are sequentially connected between two output ends of the three-phase rectification circuit, one end of the second diode and one end of the third diode are connected between the first active switch tube and the first diode after being connected in series, the other end of the second diode is connected between the second active switch tube and the fourth diode, a connecting point between the first active switch tube and the second active switch tube is correspondingly connected with one phase output of the three-phase resonant isolation circuit, and a connecting point between the second diode and the third diode is connected with a midpoint between the upper bus capacitor and the lower bus capacitor.
3. The three-phase DCDC converter of claim 2, wherein the three-phase resonant isolation circuit is configured to perform isolation filtering on three-phase output of the three-phase inverter circuit by using a three-phase LLC resonant circuit, and the three-phase DC converter comprises a three-phase resonant inductor, a three-phase resonant capacitor and a three-phase transformer, wherein primary sides and side sides of the three-phase transformer form a star Y-star Y connection.
4. A rectification control method of a three-phase DCDC converter, characterized in that a three-phase DCDC converter according to any one of claims 1 to 3 is used, the switching states of a first phase rectifying circuit, a second phase rectifying circuit and a third phase rectifying circuit of the three-phase rectifying circuits are combined, wherein the combined state of the circuit switches for charging only the upper bus capacitor is denoted as an upper middle vector, the combined state of the circuit switches for charging only the lower bus capacitor is denoted as a lower middle vector, and the three-phase DCDC converter is controlled by the combined state of the switches to execute the following three operation modes: The first working mode is a conventional working mode of the three-phase DCDC converter, wherein synchronous rectification drive or drive control is applied to control a three-phase rectification circuit to charge the upper bus capacitor and the lower bus capacitor simultaneously, and the output voltage of the three-phase rectification circuit is Vo; In the second working mode, in the same working period, the three-phase DCDC converter performs periodic conversion between the first state and the second state, the action time of the upper middle vector is the same as that of the lower middle vector, the action time is not zero, the upper bus capacitor and the lower bus capacitor are charged, and the output voltage of the three-phase rectifying circuit is 2Vo; In the same working period, the three-phase DCDC converter performs periodic conversion of the first state, the second state and the third state, the action time of the upper middle vector is the same as that of the lower middle vector, the action time is not zero, the action time of the third working state is increased to improve the output voltage of the three-phase rectifying circuit, and the output voltage of the three-phase rectifying circuit is more than 2Vo.
5. The method according to claim 4, wherein the state one selects an upper middle vector and the state two selects a lower middle vector.
6. The method according to claim 5, wherein the state one selects a lower intermediate vector and the state two selects an upper intermediate vector.

Description

Three-phase DCDC converter and rectification control method thereof Technical Field The invention relates to the field of switching power supplies, in particular to a high-power three-phase DCDC converter. Background A smart city or a direct-current micro-grid power supply system based on a direct-current power grid provides new requirements for a high-power wide-voltage output power supply. Compared with the traditional half-bridge or full-bridge converter, the three-phase converter can better realize power improvement and better output ripple and has an automatic current equalizing function. Such a three-phase series resonant type converter as shown in fig. 1 can obtain higher efficiency, but the frequency modulation operation mode is difficult to meet the requirement of wide gain. The reason is analyzed that frequency modulation shifts the resonant frequency of the resonant cavity, resulting in a wider tuning range and lower efficiency, designing a wider frequency range or introducing PWM tuning to achieve a gain widening, and also results in an increase in loss, and a limited gain widening, so that the output voltage range of such converters is about 0.7-1.3Vo. In the high-voltage quick-charging occasion, the high-voltage output is required to be met, and the wide-range output can be realized. In the prior art, a power module series-parallel scheme is adopted to realize the requirement of a high-voltage quick-charging occasion, and the scheme needs to adopt a direct-current relay to switch the series-parallel mode of output voltage at an output end. The direct current relay has higher cost, seamless switching is difficult to achieve, and the problem of energy balance among modules can also cause cost rise. Therefore, the converter which can satisfy the output voltage gain and has the characteristics of small ripple and high efficiency has wide application prospect and economic value. In addition, in order to improve the safety performance of the system, the requirements for power-down holding time are continuously increased in high-power application occasions such as data protection, industrial automation system safety, medical treatment, rail transit and the like, and on the premise of not increasing the system cost, if a transient high-gain mode can be provided, larger benefits can be obtained. There are special power supply occasions, such as PVD power supply or plasma excitation power supply, in the semiconductor application process, and a transient high voltage is required for the plasma excitation process, so that the metal granularity can be improved. Therefore, the high-power DCDC power supply has higher safety performance and economic value if a transient high-gain or transient high-voltage output state can be provided while the output gain of the high-power DCDC power supply is widened. Disclosure of Invention The invention provides a three-phase DCDC converter, which has the first purpose of widening the output voltage range of the high-power three-phase DCDC converter and the second purpose of providing a transient high-gain or transient high-voltage output state on the premise of not increasing the system cost. The three-phase DCDC converter adopts the following technical scheme: The three-phase DC converter comprises a three-phase inverter circuit, a three-phase resonant isolation circuit and a three-phase rectifying circuit which are sequentially connected, wherein the three-phase rectifying circuit comprises a first phase rectifying circuit, a second phase rectifying circuit and a third phase rectifying circuit which are respectively connected with three-phase output of the three-phase resonant isolation circuit and are used for converting three-phase alternating current transmitted by the three-phase resonant isolation circuit into direct current output, an upper bus capacitor and a lower bus capacitor which are connected in series are connected between two output ends of the three-phase rectifying circuit, the first phase rectifying circuit, the second phase rectifying circuit and the third phase rectifying circuit form a three-phase three-level bridge arm, each phase rectifying circuit comprises four communication states, wherein a positive output end is marked as a P state, a ground end is marked as an N state, a midpoint between the upper bus capacitor and the lower bus capacitor is marked as an O state, and a non-current state is marked as a G state; The three-phase DCDC converter comprises three working states: one phase of current in the three-phase rectifying circuit is larger than zero, and the other two phases of current are smaller than zero; the second state is that one phase current in the three-phase rectifying circuit is smaller than zero, and the other two phases current is larger than zero; a third state, wherein one-phase current in the three-phase rectifying circuit is larger than zero, one-phase current is smaller than zero, and one-phase current is equal to zero; Wh