EP-4738675-A1 - METHOD FOR CONTROLLING CYCLOCONVERTER CIRCUIT, CYCLOCONVERTER CIRCUIT, AND ISOLATED CONVERTER

EP4738675A1EP 4738675 A1EP4738675 A1EP 4738675A1EP-4738675-A1

Abstract

The present disclosure discloses a method for controlling a cycloconverter circuit, a cycloconverter circuit, and an isolated converter, belonging to the technical field of power control. The cycloconverter circuit is configured to perform alternating current to alternating current conversion and includes a plurality of switch elements connected in a plurality of current paths. The plurality of switch elements are divided into a plurality of groups of switch elements. Each of the plurality of groups of switch elements includes at least one switch element disposed in each of the plurality of current path. The method according to the present disclosure includes: when the cycloconverter circuit is in a zero-crossing detection stage, controlling a first group of switch elements to be turned on complementarily and a second group of switch elements to switch between an on state and an off state. During a dead time between drive signals for the first group of switch elements, a first target switch element in the second group of switch elements is turned on. Thus, a freewheeling loop is provided for a switch element located in a same-direction current path as a switch element in the first group of switch elements that is turned on after the dead time, releasing a leakage inductance current and reducing a risk of voltage overstress on a switch tube.

Inventors

CHEN, LONGYU
GAO, Wenqiang

Assignees

Sigenergy Technology Co., Ltd.

Dates

Publication Date: 20260506
Application Date: 20250613

Claims (10)

A method for controlling a cycloconverter circuit, wherein the cycloconverter circuit is configured to perform alternating current to alternating current conversion and comprises a plurality of switch elements connected in a plurality of current paths, wherein the plurality of switch elements are divided into a plurality of groups of switch elements, each of the plurality of groups of switch elements comprising at least one switch element disposed in each of the plurality of current paths; the method comprises: when the cycloconverter circuit is in a zero-crossing detection stage, controlling a first group of switch elements to be turned on complementarily and a second group of switch elements to be turned on complementarily, wherein: during a dead time between drive signals for the first group of switch elements, a first target switch element in the second group of switch elements is turned on and remains turned on at least until an end of the dead time, the first target switch element being a switch element located in a same-direction current path as a switch element in the first group of switch elements that is turned on after the dead time; during the zero-crossing detection stage, the drive signals for the first group of switch elements and drive signals for the second group of switch elements are each pulse signals, the drive signals for the second group of switch elements lead in phase relative to the drive signals for the first group of switch elements, and a phase lead amount of the drive signals for the second group of switch elements relative to the drive signals for the first group of switch elements is greater than or equal to the dead time between the drive signals for the first group of switch elements.
The method for controlling the cycloconverter circuit according to claim 1, wherein the drive signals for the second group of switch elements have a same duty cycle and/or a same period as the drive signals for the first group of switch elements.
The method for controlling the cycloconverter circuit according to claim 1 or 2, further comprising: obtaining a voltage at an output side of the cycloconverter circuit; and determining, from the plurality of groups of switch elements of the cycloconverter circuit, the first group of switch elements and the second group of switch elements based on whether the voltage is positive or negative, wherein a grouping configuration of the plurality of groups of switch elements when the voltage is positive is inverse to that when the voltage is negative.
The method for controlling the cycloconverter circuit according to claim 3, further comprising, subsequent to said obtaining the voltage at the output side of the cycloconverter circuit: determining, when an absolute value of the voltage is smaller than or equal to a first voltage threshold, that the cycloconverter circuit enters the zero-crossing detection stage.
An isolated converter, comprising: a transformer; a control unit; and a cycloconverter circuit connected to a first side of the transformer, wherein the control unit is connected to the cycloconverter circuit and is configured to the method for controlling the cycloconverter circuit according to any one of claims 1 to 4.
A cycloconverter circuit, comprising a first group of switch elements and a second group of switch elements, wherein during a zero-crossing detection stage, the first group of switch elements are turned on complementarily, the second group of switch elements are turned on complementarily, and drive signals for the second group of switch elements lead in phase relative to drive signals for the first group of switch elements, wherein a phase lead amount of the drive signals for the second group of switch elements relative to the drive signals for the first group of switch elements is greater than or equal to the dead time between the drive signals for the first group of switch elements.
The cycloconverter circuit according to claim 6, wherein the zero-crossing detection stage comprises a positive voltage stage and a negative voltage stage, a grouping configuration of the switch elements during the positive voltage stage being inverse to that during the negative voltage stage, wherein the grouping configuration of the switch elements refers to a correspondence between the first group of switch elements and the second group of switch elements and switch elements in the cycloconverter circuit.
The cycloconverter circuit according to claim 6, comprising a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a first capacitor, and a second capacitor, wherein the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube are sequentially connected in series and electrically connected between power supply lines, the first capacitor and the second capacitor are connected in series and electrically connected between the power supply lines, a connection node between the second switch tube and the third switch tube is electrically connected to a first terminal of a secondary winding of the transformer electrically connected to the cycloconverter circuit, and a connection node between the first capacitor and the second capacitor is electrically connected to a second terminal of the secondary winding of the transformer, wherein during the zero-crossing detection stage: when a voltage at an output side of the cycloconverter circuit is positive, the first group of switch elements comprises the first switch tube and the third switch tube, and the second group of switch elements comprises the second switch tube and the fourth switch tube; when the voltage at the output side of the cycloconverter circuit is negative, the first group of switch elements comprises the second switch tube and the fourth switch tube, and the second group of switch elements comprises the first switch tube and the third switch tube.
The cycloconverter circuit according to claim 6, comprising a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a third capacitor, and a fourth capacitor, wherein the fifth switch tube, the sixth switch tube, the seventh switch tube, and the eighth switch tube are sequentially connected in series and electrically connected between power supply lines, the third capacitor is electrically connected between the power supply lines, a connection node between the sixth switch tube and the seventh switch tube is electrically connected, via the fourth capacitor, to a first terminal of a secondary winding of the transformer electrically connected to the cycloconverter circuit, and a connection node between the eighth switch tube and the power supply line is electrically connected to a second terminal of the secondary winding of the transformer, wherein during the zero-crossing detection stage: when a voltage at an output side of the cycloconverter circuit is positive, the first group of switch elements comprises the fifth switch tube and the seventh switch tube, and the second group of switch elements comprises the sixth switch tube and the eighth switch tube; when the voltage at the output side of the cycloconverter circuit is negative, the first group of switch elements comprises the sixth switch tube and the eighth switch tube, and the second group of switch elements comprises the fifth switch tube and the seventh switch tube.
The cycloconverter circuit according to claim 6, comprising a ninth switch tube, a tenth switch tube, an eleventh switch tube, a twelfth switch tube, a fifth capacitor, and a sixth capacitor, wherein the ninth switch tube, the tenth switch tube, the eleventh switch tube, and the twelfth switch tube are sequentially connected in series and electrically connected between power supply lines, the fifth capacitor is electrically connected between the power supply lines, a connection node between the ninth switch tube and the tenth switch tube is electrically connected, via the sixth capacitor, to a first terminal of a secondary winding of the transformer electrically connected to the cycloconverter circuit, and a connection node between the eleventh switch tube and the twelfth switch tube is electrically connected to a second terminal of the secondary winding of the transformer, wherein during the zero-crossing detection stage: when a voltage at an output side of the cycloconverter circuit is positive, the first group of switch elements comprises the ninth switch tube and the eleventh switch tube, and the second group of switch elements comprises the tenth switch tube and the twelfth switch tube; when the voltage at the output side of the cycloconverter circuit is negative, the first group of switch elements comprises the tenth switch tube and the twelfth switch tube, and the second group of switch elements comprises the ninth switch tube and the eleventh switch tube.

Description

FIELD The present disclosure belongs to the technical field of power control, and more particularly, relates to a method for controlling a cycloconverter circuit, a cycloconverter circuit, and an isolated converter. BACKGROUND In new energy photovoltaic, energy storage, and charging scenarios, high-efficiency conversion circuits are required. Among various topological solutions of the conversion circuits, an isolated single-stage topology based on a direct-current side active full-bridge and cycloconverter has attracted increasing attention in the industry due to its advantages of few circuit elements, high conversion efficiency, and input and output electrical isolation. Switch tubes are classified into high-frequency tubes and low-frequency tubes during a control process of the cycloconverter, and an interchange between the high-frequency tubes and the low-frequency tubes occurs at a zero-crossing point of a voltage of a grid power. In practical applications, a dead time is set during the interchange process in order to avoid a short circuit of a bridge arm caused by shoot-through during the interchange process. During the dead time, all the switch tubes are turned off. However, this can lead to a risk of overstress on the switch tubes. SUMMARY The present disclosure aims to solve at least one of the technical problems in the related art. To this end, the present disclosure provides a method for controlling a cycloconverter circuit, a cycloconverter circuit, and an isolated converter, which reduces a risk of voltage overstress on switch tubes and makes it easier to meet a soft-switching condition of zero-voltage switching. In a first aspect, the present disclosure provides a method for controlling a cycloconverter circuit. The cycloconverter circuit is configured to perform alternating current to alternating current conversion and includes a plurality of switch elements connected in a plurality of current paths. The plurality of switch elements are divided into a plurality of groups of switch elements. Each of the plurality of groups of switch elements includes at least one switch element disposed in each of the plurality of current paths. The method for controlling the cycloconverter circuit includes: when the cycloconverter circuit is in a zero-crossing detection stage, controlling a first group of switch elements to be turned on complementarily and a second group of switch elements to switch between an on state and an off state. During a dead time between drive signals for the first group of switch elements, a first target switch element in the second group of switch elements is turned on. The first target switch element is a switch element located in a same-direction current path as a switch element in the first group of switch elements that is turned on after the dead time. In the method for controlling the cycloconverter circuit according to the present disclosure, when the cycloconverter circuit is in the zero-crossing detection stage, the first target switch element in the second group of switch elements is turned on within the dead time between the drive signals for the first group of switch elements. Thus, a freewheeling loop is provided for the switch element in the first group of switch elements that is turned on after the dead time, releasing a leakage inductance current and reducing a risk of voltage overstress on a switch tube. As a result, it is easier to meet a soft switching condition of zero-voltage switching. According to an embodiment of the present disclosure, the first target switch element remains turned on at least until an end of the dead time. According to an embodiment of the present disclosure, the first target switch element is turned on prior to a start of the dead time. According to an embodiment of the present disclosure, during the zero-crossing detection stage, the drive signals for the first group of switch elements and drive signals for the second group of switch elements are each pulse signals, and the drive signals for the second group of switch elements lead in phase relative to the drive signals for the first group of switch elements. According to an embodiment of the present disclosure, a phase lead amount of the drive signals for the second group of switch elements relative to the drive signals for the first group of switch elements is greater than or equal to the dead time between the drive signals for the first group of switch elements. According to an embodiment of the present disclosure, the drive signals for the second group of switch elements have a same duty cycle and/or a same period as the drive signals for the first group of switch elements. According to an embodiment of the present disclosure, the method further includes: obtaining a voltage at an output side of the cycloconverter circuit; and determining, from the plurality of groups of switch elements of the cycloconverter circuit, the first group of switch elements and the second group of switch ele