DIRECT CURRENT TO DIRECT CURRENT (DCDC) CONVERTER AND CONTROL METHOD

The present disclosure provides a Direct Current to Direct Current (DCDC) converter and a control method thereof. The Direct Current to Direct Current (DCDC) converter comprises: at least one DCDC conversion module and a controller, wherein each of the DCDC conversion modules comprises two bidirectional isolated DCDC units connected in parallel, each of the bidirectional isolated DCDC units comprises a resonant circuit and a non-isolated buck/boost circuit connected in cascade; if the number of the DCDC conversion modules is greater than or equal to 2, the DCDC conversion modules are connected in parallel; the controller is connected to each of the bidirectional isolated DCDC units, and control current sharing among the non-isolated buck/boost circuits. The Direct Current to Direct Current (DCDC) converter and the control method thereof according to the embodiments of the present disclosure reduce the manufacturing cost of the Direct Current to Direct Current (DCDC) converter.

TECHNICAL FIELD

The present disclosure relates to the technical field of power electronic devices, and particularly to a Direct Current to Direct Current (DCDC) converter and a control method thereof.

BACKGROUND

With the popularization of new energy vehicles, the demand for household direct-current charging piles is increasing, and the power requirement of the charging piles is becoming higher.

The charging pile may be equipped with a bidirectional converter, through which not only an electric vehicle can be charged, but also a power battery of the electric vehicle can be used as an emergency power supply. When an electricity price of a grid is relatively cheap, the electric vehicle can be charged, and when a power failure is caused by earthquakes, typhoons and other reasons, the power battery of the electric vehicle can be used as an emergency power supply for household appliances, and at the same time, the power battery may be connected to the grid for power generation in a period where the electricity price is relatively high. As a key link of a bidirectional charging device, the bidirectional converter has a great influence on the performance of the whole device.

SUMMARY

In order to improve the power of a bidirectional converter, a plurality of transformer windings are connected in series, which leads to complex manufacturing, difficult realization and high manufacturing cost of a transformer. Aiming at the problem that a high-power bidirectional converter increases the manufacturing cost of the transformer, the embodiments of the present disclosure provide a bidirectional isolated DCDC converter and a control method thereof, which can at least partially solve the above problem.

In an aspect, the present disclosure provides a Direct Current to Direct Current (DCDC) converter, comprising at least one DCDC conversion module and a controller, wherein:each of the DCDC conversion modules comprises two bidirectional isolated DCDC units connected in parallel, each of the bidirectional isolated DCDC units comprises a resonant circuit and a non-isolated buck/boost circuit connected in cascade; wherein a working frequency of each of the resonant circuits is fixed; and if the number of the DCDC conversion modules is greater than or equal to 2, the DCDC conversion modules are connected in parallel;the controller is electrically connected to each of the bidirectional isolated DCDC units, and is configured to control current sharing among the non-isolated buck/boost circuits.

Further, the resonant circuit comprises a three-phase LLC circuit or an LLC extension circuit.

Further, the three-phase LLC circuit comprises a first three-phase circuit, a second three-phase circuit and three transformers, wherein:the first three-phase circuit is connected to primary sides of the three transformers, and the second three-phase circuit is connected to secondary sides of the three transformers.

Further, the non-isolated buck/boost circuit comprises a first branch, a second branch, a seventh inductor and an eighth inductor, wherein:the first branch and the second branch are connected in parallel, the first branch comprises a thirteenth switch tube and a fourteenth switch tube connected in series, and the second branch comprises a fifteenth switch tube and a sixteenth switch tube connected in series; a first end of the seventh inductor is connected to a second end of the fifteenth switch tube and a first end of the sixteenth switch tube, a first end of the eighth inductor is connected to a second end of the thirteenth switch tube and a first end of the fourteenth switch tube, and a second end of the seventh inductor is connected to a second end of the eighth inductor.

In another aspect, the present disclosure provides a bidirectional charging and discharging device, comprising the Direct Current to Direct Current (DCDC) converter according to any one of the aforementioned embodiments.

In still another aspect, the present disclosure provides a control method of the Direct Current to Direct Current (DCDC) converter according to any one of the aforementioned embodiments, comprising:during an operation in a first direction, controlling driving of the two resonant circuits comprised in each of the DCDC conversion modules at corresponding positions to be opposite, and controlling each of the non-isolated buck/boost circuits to work in a buck state and causing output current of each of the non-isolated buck/boost circuits to be equal; andduring an operation in a second direction, controlling driving of the two resonant circuits comprised in each of the DCDC conversion modules at corresponding positions to be opposite, and controlling each of the non-isolated buck/boost circuits to work in a DC boost state and causing output current of each of the non-isolated buck/boost circuits to be equal, wherein the first direction is opposite to the second direction.

Further, controlling each of the non-isolated buck/boost circuits to work in a buck state and causing output current of each of the non-isolated buck/boost circuits to be equal comprises:

generating a first current reference value according to a preset voltage reference value and an output voltage sampling value, and adjusting a duty ratio of each of the non-isolated buck/boost circuits according to the first current reference value and the output current sampling value of each of the non-isolated buck/boost circuits, so as to cause the output current of each of the non-isolated buck/boost circuits to be equal.

Further, controlling each of the non-isolated buck/boost circuits to work in a DC boost state and causing output current of each of the non-isolated buck/boost circuits to be equal comprises: controlling each of the non-isolated buck/boost circuits to generate an intermediate bus voltage of each of the bidirectional isolated DCDC units, and obtaining a second current reference value according to an intermediate bus voltage reference value and an intermediate bus voltage sampling value of each of the bidirectional isolated DCDC units; andadjusting a duty ratio of each of the non-isolated buck/boost circuits according to the second current reference value and an input current sampling value of each of the non-isolated buck/boost circuits, so as to cause input current of each of the non-isolated buck/boost circuits to be equal. The embodiments of the present disclosure provide a Direct Current to Direct Current (DCDC) converter and a control method thereof. The Direct Current to Direct Current (DCDC) converter comprises: at least one DCDC conversion module and a controller, wherein each of the DCDC conversion modules comprises two bidirectional isolated DCDC units connected in parallel, each of the bidirectional isolated DCDC units comprises a resonant circuit and a non-isolated buck/boost circuit connected in cascade; the controller is electrically connected to each of the bidirectional isolated DCDC units, and is configured to control current sharing among the non-isolated buck/boost circuits. The method is applied to the Direct Current to Direct Current (DCDC) converter. The power requirement of the Direct Current to Direct Current (DCDC) converter is satisfied by at least one DCDC conversion module, thereby reducing the manufacturing cost of the Direct Current to Direct Current (DCDC) converter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order that the objectives, technical solutions and advantages of the embodiments of the present disclosure are clearer, the embodiments of the present disclosure are further described in detail below with reference to the drawings. Here, the exemplary embodiments of the present disclosure and the description thereof are used to explain, rather than limiting the present disclosure. It should be noted that the embodiments of the present disclosure and the features in the embodiments can be combined with each other arbitrarily without conflict.

In order to facilitate the understanding of the technical solutions provided by the present disclosure, firstly the related content of the technical solutions of the present disclosure will be explained below. In the embodiments of the present disclosure, at least two temperature sensors, or at least two filtering algorithms which are corresponding to a same temperature sensor, are needed to collect temperatures of a target object. In the embodiments of the present disclosure, for the convenience of description, one channel is corresponding to one temperature sensor or one filtering algorithm. A temperature processing method according to the embodiments of the present disclosure may be applied in a temperature detection system of an electric vehicle, or any other scene requiring a temperature collection, which is not limited in the embodiments of the present disclosure.

FIG.1is a structural diagram of a Direct Current to Direct Current (DCDC) converter according to a first embodiment of the present disclosure. As illustrated inFIG.1, the Direct Current to Direct Current (DCDC) converter according to the embodiment of the present disclosure includes at least one DCDC conversion module1and a controller, wherein:each of the DCDC conversion modules1includes two bidirectional isolated DCDC units11connected in parallel, each of the bidirectional isolated DCDC units includes a resonant circuit111and a non-isolated buck/boost circuit112connected in cascade; wherein a working frequency of each of the resonant circuits111is fixed; and if the number of the DCDC conversion modules1is greater than or equal to 2, the DCDC conversion modules1are connected in parallel;the controller is electrically connected to each of the bidirectional isolated DCDC units11, and is configured to control current sharing among the non-isolated buck/boost circuits112.

Specifically, the Direct Current to Direct Current (DCDC) converter according to the embodiment of the present disclosure can realize a bidirectional power flow, i.e., the Direct Current to Direct Current (DCDC) converter may charge a connected charging object and work in a charging mode, and may output electric energy stored in the charging object to the outside and work in a power supply mode. In the charging mode, external current flows from the resonant circuit111to the non-isolated buck/boost circuit112to charge the charging object, wherein the resonant circuit111serves for boosting, the non-isolated buck/boost circuit112serves for bucking, and the Direct Current to Direct Current (DCDC) converter operates in a first direction. In the power supply mode, current supplied by the charging object flows from the non-isolated buck/boost circuit112to the resonant circuit111, and then is output to the outside. At this time, the non-isolated buck/boost circuit112serves for boosting, the resonant circuit111serves for bucking, and the Direct Current to Direct Current (DCDC) converter operates in a second direction. In practical uses, the current may be connected to a Power Factor Correction (PFC) circuit from the resonant circuit111, and the non-isolated buck/boost circuit112may be connected to a rechargeable battery.

The controller is configured to drive each of the bidirectional isolated DCDC units and each of the non-isolated buck/boost circuits112. The controller reduces Electromagnetic Interference (EMI) noise of the Direct Current to Direct Current (DCDC) converter by controlling driving two resonant circuits included in each of the DCDC conversion modules at corresponding positions to be opposite. The controller controls the output current of each of the non-isolated buck/boost circuits to be equal, so as to achieve the current sharing among the non-isolated buck/boost circuits112. A voltage isolation of each of the resonant circuits111is achieved by fixing the working frequency thereof, wherein the controller may adopt a Microcontroller Unit (MCU) or a Digital Signal Processing (DSP) chip.

A power expansion of the Direct Current to Direct Current (DCDC) converter is achieved by increasing the number of the DCDC conversion modules1, and greater power can be supported as the number of the DCDC conversion modules1increases. The number of the DCDC conversion modules1is set according to the needs of actual power, e.g., 2 to 10 DCDC conversion modules1may be set, which is only an example, and the number of the DCDC conversion modules1is not limited in the embodiments of the present disclosure.

As illustrated inFIG.2, the Direct Current to Direct Current (DCDC) converter according to the present disclosure includes two DCDC conversion modules1connected in parallel, which improves the power of the Direct Current to Direct Current (DCDC) converter compared with the structure including one DCDC conversion module1as illustrated inFIG.1.

The Direct Current to Direct Current (DCDC) converter according to the embodiments of the present disclosure includes at least one DCDC conversion module and a controller, each of the DCDC conversion modules includes two bidirectional isolated DCDC units connected in parallel, each of the bidirectional isolated DCDC units includes a resonant circuit and a non-isolated buck/boost circuit connected in cascade, and the controller is electrically connected to each of the bidirectional isolated DCDC units and is configured to control current sharing among the non-isolated buck/boost circuits. The power requirement of the Direct Current to Direct Current (DCDC) converter is satisfied by at least one DCDC conversion module, thereby avoiding the use of complex transformer structure and reducing the manufacturing cost of the Direct Current to Direct Current (DCDC) converter.

Based on the above embodiments, further, the resonant circuit111includes a three-phase LLC circuit or an LLC extension circuit. An input and output ripple ratio of the three-phase LLC circuit is small. The LLC extension circuit is a three-phase resonant circuit modified or improved based on the above three-phase LLC circuit.

FIG.3is a structural diagram of a Direct Current to Direct Current (DCDC) converter according to a third embodiment of the present disclosure. As illustrated inFIG.3, based on the above embodiments, further, the three-phase LLC circuit includes a first three-phase circuit310, a second three-phase circuit320and three transformers, wherein:

The first three-phase circuit310is connected to primary sides of the three transformers, and the second three-phase circuit320is connected to secondary sides of the three transformers. The second three-phase circuit320is connected to the non-isolated buck/boost circuit112.

The first three-phase circuit310may adopt the circuit structures illustrated inFIG.3,4,5or6, or any other three-phase circuit in which electronic components such as inductor, capacitor, resistor, switch tube and the like are added or reduced based on the first three-phase circuit, which is not limited here. The second three-phase circuit320may adopt the circuit structures illustrated inFIG.7,8,9or10, or any other three-phase circuit in which electronic components such as inductor, capacitor, resistor, switch tube and the like are added or reduced based on the second three-phase circuit, which is not limited here.

FIG.4is a structural diagram of a first three-phase circuit according to a fourth embodiment of the present disclosure. As illustrated inFIG.4, based on the above embodiments, further, the first three-phase circuit310includes a first switch tube M1, a second switch tube M2, a third switch tube M3, a fourth switch tube M4, a fifth switch tube M5, a sixth switch tube M6, a first inductor L1, a second inductor L2, a third inductor L3, a first capacitor C1, a second capacitor C2and a third capacitor C3; the first switch tube M1and the second switch tube M2are connected in series, the third switch tube M3and the fourth switch tube M4are connected in series, and the fifth switch tube M5and the sixth switch tube M6are connected in series; a first end of the first inductor L1is connected between the first switch tube M1and the second switch tube M2, a first end of the second inductor L2is connected between the third switch tube M3and the fourth switch tube M4, and a first end of the third inductor L3is connected between the fifth switch tube M5and the sixth switch tube M6; a second end of the first inductor L1is connected to a first end of a primary side of a first transformer T1, a second end of the primary side of the first transformer Tl is connected to a first end of the first capacitor C1, a second end of the second inductor L2is connected to a first end of a primary side of a second transformer T2, a second end of the primary side of the second transformer T2is connected to a first end of the second capacitor C2, a second end of the third inductor L3is connected to a first end of a primary side of a third transformer T3, a second end of the primary side of the third transformer T3is connected to a first end of the third capacitor C3, and a second end of the first capacitor C1and a second end of the second capacitor C2are connected to a second end of the third capacitor C3; a first end of the first switch tube M1and a first end of the third switch tube M3are connected to a first end of the fifth switch tube M5, and a second end of the second switch tube M2and a second end of the fourth switch tube M4are connected to a second end of the sixth switch tube M6.

FIG.5is a structural diagram of a first three-phase circuit according to a fifth embodiment of the present disclosure. As illustrated inFIG.5, based on the above embodiments, further, the first three-phase210circuit includes a first switch tube M1, a second switch tube M2, a third switch tube M3, a fourth switch tube M4, a fifth switch tube M5, a sixth switch tube M6, a first capacitor C1, a second capacitor C2and a third capacitor C3; the first switch tube M1and the second switch tube M2are connected in series, the third switch tube M3and the fourth switch tube M4are connected in series, and the fifth switch tube M5and the sixth switch tube M6are connected in series; a first end of a primary side of a first transformer T1is connected between the first switch tube M1and the second switch tube M2, a first end of a primary side of a second transformer T2is connected between the third switch tube M3and the fourth switch tube M4, and a first end of a primary side of a third transformer T3is connected between the fifth switch tube M5and the sixth switch tube M6; a second end of the primary side of the first transformer T1is connected to a first end of the first capacitor C1, a second end of the primary side of the second transformer T2is connected to a first end of the second capacitor C2, a second end of the primary side of the third transformer T3is connected to a first end of the third capacitor C3, a second end of the first capacitor C1and a second end of the second capacitor C2are connected to a second end of the third capacitor C3.

FIG.6is a structural diagram of a first three-phase circuit according to a sixth embodiment of the present disclosure. As illustrated inFIG.6, based on the above embodiments, further, the first three-phase circuit310includes a first switch tube M1, a second switch tube M2, a third switch tube M3, a fourth switch tube M4, a fifth switch tube M5, a sixth switch tube M6, a first inductor L1, a second inductor L2and a third inductor L3; the first switch tube M1and the second switch tube M2are connected in series, the third switch tube M3and the fourth switch tube M4are connected in series, and the fifth switch tube M5and the sixth switch tube M6are connected in series; a first end of the first inductor L1is connected between the first switch tube M1and the second switch tube M2, a first end of the second inductor L2is connected between the third switch tube M3and the fourth switch tube M4, and a first end of the third inductor L3is connected between the fifth switch tube M5and the sixth switch tube M6; a second end of the first inductor L1is connected to a first end of a primary side of a first transformer T1, a second end of the second inductor L2is connected to a first end of a primary side of a second transformer T2, and a second end of the third inductor L3is connected to a first end of a primary side of the third transformer T3; a second end of the primary side of the first transformer T1and a second end of the primary side of the second transformer T2are connected to a second end of the primary side of the third transformer T3.

FIG.7is a structural diagram of a first three-phase circuit according to a seventh embodiment of the present disclosure. As illustrated inFIG.7, based on the above embodiments, further, the first three-phase circuit further includes a first switch tube M1, a second switch tube M2, a third switch tube M3, a fourth switch tube M4, a fifth switch tube M5and a sixth switch tube M6; the first switch tube M1and the second switch tube M2are connected in series, the third switch tube M3and the fourth switch tube M4are connected in series, and the fifth switch tube M5and the sixth switch tube M6are connected in series; a first end of a primary side of the first transformer

T1is connected between the first switch tube M1and the second switch tube M2, a first end of a primary side of the second transformer T2is connected between the third switch tube M3and the fourth switch tube M4, and a first end of a primary side of the third transformer T3is connected between the fifth switch tube M5and the sixth switch tube M6; a second end of the primary side of the first transformer T1and a second end of the primary side of the second transformer T2are connected to a second end of the primary side of the third transformer T3.

FIG.8is a structural diagram of a second three-phase circuit according to an eighth embodiment of the present disclosure. As illustrated inFIG.8, based on the above embodiments, further, the second three-phase circuit320includes a seventh switch tube M7, an eighth switch tube M8, a ninth switch tube M9, a tenth switch tube M10, an eleventh switch tube M11, a twelfth switch tube M12, a fourth inductor L4, a fifth inductor L5, a sixth inductor L6, a fourth capacitor C4, a fifth capacitor C5, and a sixth capacitor C6; the seventh switch tube M7and the eighth switch tube M8are connected in series, the ninth switch tube M9and the tenth switch tube M10are connected in series, and the eleventh switch tube M11and the twelfth switch tube M12are connected in series; a first end of a secondary side of a first transformer T1is connected to a first end of the fourth inductor L4, and a second end of the fourth inductor L4is connected between the seventh switch tube M7and the eighth switch tube M8; a first end of a secondary side of a second transformer T2is connected to a first end of the fifth inductor L5, and a second end of the fifth inductor L5is connected between the ninth switch tube M9and the tenth switch tube M10; a first end of a secondary side of a third transformer T3is connected to a first end of the sixth inductor L6, and a second end of the sixth inductor L6is connected between the eleventh switch tube M11and the twelfth switch tube M12; a second end of the secondary side of the first transformer T1is connected to a first end of the fourth capacitor C4, a second end of the secondary side of the second transformer T2is connected to a first end of the fifth capacitor C5, a second end of the secondary side of the third transformer T3is connected to a first end of the sixth capacitor C6, and a second end of the fourth capacitor C4and a second end of the fifth capacitor C5are connected to a second end of the sixth capacitor C6.

FIG.9is a structural diagram of a second three-phase circuit according to a ninth embodiment of the present disclosure. As illustrated inFIG.9, based on the above embodiments, further, the second three-phase circuit320includes a seventh switch tube M7, an eighth switch tube M8, a ninth switch tube M9, a tenth switch tube M10, an eleventh switch tube M11, a twelfth switch tube M12, a fourth capacitor C4, a fifth capacitor C5and a sixth capacitor C6; the seventh switch tube M7and the eighth switch tube M8are connected in series, the ninth switch tube M9and the tenth switch tube M10are connected in series, and the eleventh switch tube M11and the twelfth switch tube M12are connected in series; a first end of a secondary side of a first transformer T1is connected between the seventh switch tube M7and the eighth switch tube M8; a first end of a secondary side of a second transformer T2is connected between the ninth switch tube M9and the tenth switch tube M10; a first end of a secondary side of a third transformer T3is connected between the eleventh switch tube M11and the twelfth switch tube M12; a second end of the secondary side of the first transformer T1is connected to a first end of the fourth capacitor C4, a second end of the secondary side of the second transformer T2is connected to a first end of the fifth capacitor C5, a second end of the secondary side of the third transformer T3is connected to a first end of the sixth capacitor C6, and a second end of the fourth capacitor C4and a second end of the fifth capacitor C5are connected to a second end of the sixth capacitor C6.

FIG.10is a structural diagram of a second three-phase circuit according to a tenth embodiment of the present disclosure. As illustrated inFIG.10, based on the above embodiments, further, the second three-phase circuit320includes a seventh switch tube M7, an eighth switch tube M8, a ninth switch tube M9, a tenth switch tube M10, an eleventh switch tube M11, a twelfth switch tube M12, a fourth inductor L4, a fifth inductor L5and a sixth inductor L6; the seventh switch tube M7and the eighth switch tube M8are connected in series, the ninth switch tube M9and the tenth switch tube M10are connected in series, and the eleventh switch tube M11and the twelfth switch tube M12are connected in series; a first end of a secondary side of a first transformer T1is connected to a first end of the fourth inductor L4, and a second end of the fourth inductor L4is connected between the seventh switch tube M7and the eighth switch tube M8; a first end of a secondary side of a second transformer T2is connected to a first end of the fifth inductor L5, and a second end of the fifth inductor L5is connected between the ninth switch tube M9and the tenth switch tube M10; a first end of a secondary side of a third transformer T3is connected to a first end of the sixth inductor L6, and a second end of the sixth inductor L6is connected between the eleventh switch tube M11and the twelfth switch tube M12; and a second end of the secondary side of the first transformer T1and a second end of the secondary side of the second transformer T2are connected to a second end of the secondary side of the third transformer T3.

FIG.11is a structural diagram of a second three-phase circuit according to an eleventh embodiment of the present disclosure. As illustrated inFIG.11, based on the above embodiments, further, the second three-phase circuit320includes a seventh switch tube M7, an eighth switch tube M8, a ninth switch tube M9, a tenth switch tube M10, an eleventh switch tube M11and a twelfth switch tube M12; the seventh switch tube M7and the eighth switch tube M8are connected in series, the ninth switch tube M9and the tenth switch tube M10are connected in series, and the eleventh switch tube M11and the twelfth switch tube M12are connected in series; a first end of a secondary side of a first transformer T1is connected between the seventh switch tube M7and the eighth switch tube M8, a first end of a secondary side of a second transformer T2is connected between the ninth switch tube M9and the tenth switch tube M10, a first end of a secondary side of a third transformer T3is connected between the eleventh switch tube M11and the twelfth switch tube M12, and a second end of the secondary side of the first transformer T1and a second end of the secondary side of the second transformer T2are connected a second end of the secondary side of the third transformer T3.

Based on the above embodiments, further, the non-isolated buck/boost circuit112adopts an interleaving buck/boost circuit or a single-stage buck/boost circuit.

Based on the above embodiments, further, as illustrated inFIG.12, the non-isolated buck/boost circuit112includes a first branch330, a second branch340, a seventh inductor L7and an eighth inductor L8, wherein:the first branch330is connected in parallel with the second branch340, the first branch330includes a thirteenth switch tube M13and a fourteenth switch tube M14connected in series, and the second branch340includes a fifteenth switch tube M15and a sixteenth switch tube M16connected in series; a first end of the seventh inductor L7is connected to a second end of the fifteenth switch tube M15and a first end of the sixteenth switch tube M16, a first end of the eighth inductor L8is connected to a second end of the thirteenth switch tube M13and a first end of the fourteenth switch tube M14, and a second end of the seventh inductor L7is connected to a second end of the eighth inductor. The first branch330and the second branch340are connected to the resonant circuit111, respectively.

As illustrated inFIG.3, the first three-phase circuit310adopts the circuit structure illustrated inFIG.3, the second three-phase circuit320adopts the circuit structure illustrated inFIG.11, and the non-isolated buck/boost circuit112adopts the circuit structure illustrated inFIG.12.

In which, an external port of the first three-phase circuit310may be provided with a first filter capacitor C7and a second filter capacitor C8connected in series, a first end of the first filter capacitor C7is connected to a first end of the external port of the first three-phase circuit310, a second end of the first filter capacitor C7is connected to a first end of the second filter capacitor C8, and a second end of the second filter capacitor C8is connected to a second end of the external port of the first three-phase circuit310. A first end of the first switch tube M1, a first end of the third switch tube M3and a first end of the fifth switch tube M5are connected to the first end of the external port of the first three-phase circuit310, and a second end of the second switch tube M2, a second end of the fourth switch tube M4and a second end of the sixth switch tube M6are connected to the second end of the external port of the first three-phase circuit310.

The first switch tube M1and the second switch tube M2are driven complementarily, the third switch tube M3and the fourth switch tube M4are driven complementarily, and the fifth switch tube M5and the sixth switch tube M6are driven complementally; a first bridge arm to which the first switch tube M1and the second switch tube M2belong, a second bridge arm to which the third switch tube M3and the fourth switch tube M4belong and a third bridge arm to which the fifth switch tube M5and the sixth switch tube M6belong are driven at the same position by a difference of 120 degrees.

The seventh switch tube M7and the eighth switch tube M8are driven complementarily, the ninth switch tube M9and the tenth switch tube M10are driven complementarily, and the eleventh switch tube M11and the twelfth switch tube M12are driven complementarily; a fourth bridge arm to which the seventh switch tube M7and the eighth switch tube M8belong, a fifth bridge arm to which the ninth switch tube M9and the tenth switch tube M10belong and a sixth bridge arm to which the eleventh switch tube M11and the twelfth switch tube M12belong are driven at the same position by a difference of 120 degrees.

In which, an external port of the non-isolated buck/boost circuit112may be provided with a third filter capacitor C9, a first end of which is connected to a second end of the seventh inductor L7and a second end of the eighth inductor L8, respectively, and a second end of which is connected to a second end of the fourteenth switch tube M14and a second end of the sixteenth switch tube M16, respectively. A first end of the external port of the non-isolated buck/boost circuit112is connected to the first end of the third filter capacitor C9, the second end of the seventh inductor L7and the second end of the eighth inductor L8, respectively. A second end of the external port of the non-isolated buck/boost circuit112is connected to the second end of the third filter capacitor C9, the second end of the fourteenth switch tube M14and the second end of the sixteenth switch tube M16, respectively. The non-isolated buck/boost circuit112inFIG.3is an interleaving buck/boost circuit.

In which, a first bus capacitor C10is disposed between the second three-phase circuit320and the non-isolated buck/boost circuit112, and a voltage across the first bus capacitor may be referred to as an intermediate bus voltage, which is an output end voltage of the resonant circuit111during an operation in a first direction and an output end voltage of the non-isolated buck/boost circuit112during an operation in a second direction. The first bus capacitor C10is connected in parallel with the second three-phase circuit320; a first end of the first bus capacitor C10is connected to the first end of the seventh switch tube M7, the first end of the ninth switch tube M9and the first end of the eleventh switch tube M11, respectively, and a second end of the first bus capacitor C10is connected to the second end of the eighth switch tube M8, the second end of the tenth switch tube M10and the second end of the twelfth switch tube M12, respectively.

As illustrated inFIG.13, the first three-phase circuit310adopts the circuit structure illustrated inFIG.5, and the second three-phase circuit320adopts the circuit structure illustrated inFIG.11.

The non-isolated buck/boost circuit112includes a seventeenth switch tube M17, an eighteenth switch tube M18and a ninth inductor L9, wherein:the seventeenth switch tube M17and the eighteenth switch tube M18are connected in series, a second end of the seventeenth switch tube M17is connected to a first end of the eighteenth switch tube M18, and a first end of the ninth inductor L9is connected to the second end of the seventeenth switch tube M17and the first end of the eighteenth switch tube M18, respectively; a first end of the seventeenth switch tube M17and a second end of the eighteenth switch tube M18are connected to the second three-phase circuit320.

The external port of the non-isolated buck/boost circuit112may be provided with a fourth filter capacitor C11, a first end of which is connected to a second end of the ninth inductor L9, and a second end of which is connected to the second end of the eighteenth switch tube M18. A first end of the external port of the non-isolated buck/boost circuit112is connected to the second end of the ninth inductor L9and the first end of the fourth filter capacitor C11, respectively, and a second end of the external port of the non-isolated buck/boost circuit112is connected to the second end of the fourth filter capacitor C11and the second end of the eighteenth switch tube M18, respectively. The non-isolated buck/boost circuit112inFIG.13is a single-stage buck/boost circuit.

As illustrated inFIG.13, a second bus capacitor C12is disposed between the second three-phase circuit320and the non-isolated buck/boost circuit112, and a voltage across the second bus capacitor C12may be referred to as an intermediate bus voltage. The second bus capacitor C12and the second three-phase circuit320are connected in parallel, and a first ends of the second bus capacitor C12are connected to the first end of the seventh switch tube M7, the first end of the ninth switch tube M9and the first end of the eleventh switch tube M11, respectively. A second end of the second bus capacitor C12is connected to the second end of the eighth switch tube M8, the second end of the tenth switch tube M10and the second end of the twelfth switch tube M12, respectively.

A bidirectional charging and discharging device according to an embodiment of the present disclosure includes the Direct Current to Direct Current (DCDC) converter according to any one of the aforementioned embodiments. The bidirectional charging and discharging device may be applied to a charging pile.

FIG.14is a flowchart of a control method of a Direct Current to Direct Current (DCDC) converter according to a fourteenth embodiment of the present disclosure. As illustrated inFIG.14, the control method of the Direct Current to Direct Current (DCDC) converter according to the embodiment of the present disclosure may be applied to the Direct Current to Direct Current (DCDC) converter according to any one of the aforementioned embodiments, including:

S1401: during an operation in a first direction, controlling driving of the two resonant circuits included in each of the DCDC conversion modules at corresponding positions to be opposite, and controlling each of the non-isolated buck/boost circuits to work in a buck state and causing output current of each of the non-isolated buck/boost circuits to be equal.

Specifically, when the Direct Current to Direct Current (DCDC) converter works in a charging mode, i.e., operating in the first direction, current flows from each of the resonant circuits to the cascaded non-isolated buck/boost circuit, and the controller drives each of the resonant circuits to buck an input voltage to obtain an intermediate bus voltage, while controlling driving of the two resonant circuits included in each of the DCDC conversion modules at corresponding positions to be opposite, so as to reduce EMI noise of the Direct Current to Direct Current (DCDC) converter. The controller drives each of the non-isolated buck/boost circuits to work in a buck state, and buck and output the intermediate bus voltage, while controlling output current of each of the non-isolated buck/boost circuits to be equal, so as to achieve the current sharing among the non-isolated buck/boost circuits.

S1402: during an operation in a second direction, controlling driving of the two resonant circuits included in each of the DCDC conversion modules at corresponding positions to be opposite, and controlling each of the non-isolated buck/boost circuits to work in a DC boost state and causing output current of each of the non-isolated buck/boost circuits to be equal, wherein the first direction is opposite to the second direction.

Specifically, when the Direct Current to Direct Current (DCDC) converter works in a power supply mode, i.e., operating in the second direction, current flows from each of the non-isolated buck/boost circuits to the cascaded resonant circuit, and the controller drives each of the non-isolated buck/boost circuits to work in a buck state, converts a voltage input from an input end into an intermediate bus voltage, while controlling the output current of each of the non-isolated buck/boost circuits to be equal, so as to achieve the current sharing among the non-isolated buck/boost circuits. The controller drives each of the resonant circuits to buck and output the intermediate bus voltage, while controlling driving of the two resonant circuits included in each of the DCDC conversion modules at corresponding positions to be opposite, so as to reduce EMI noise of the DC-DC DCDC converter, wherein the first direction is opposite to the second direction. It can be understood that there is no sequential relationship between step S401and step S402.

The control method of the Direct Current to Direct Current (DCDC) converter according to the embodiment of the present disclosure, during an operation in a first direction, controls driving of the two resonant circuits included in each of the DCDC conversion modules at corresponding positions to be opposite, and controls each of the non-isolated buck/boost circuits to work in a buck state while causing output current of each of the non-isolated buck/boost circuits to be equal; and during an operation in a second direction, controls driving of the two resonant circuits included in each of the DCDC conversion modules at corresponding positions to be opposite, and controls each of the non-isolated buck/boost circuits to work in a DC boost state while causing output current of each of the non-isolated buck/boost circuits to be equal, so as to achieve the current sharing among the non-isolated buck/boost circuits, reduce the capacitance ripples between the resonant circuit and the non-isolated buck/boost circuit, and improve the reliability of the Direct Current to Direct Current (DCDC) converter.

Based on the above embodiments, further, controlling each of the non-isolated buck/boost circuits to work in a buck state and causing output current of each of the non-isolated buck/boost circuits to be equal includes:generating a first current reference value according to a preset voltage reference value and an output voltage sampling value, and adjusting a duty ratio of each of the non-isolated buck/boost circuits according to the first current reference value and the output current sampling value of each of the non-isolated buck/boost circuits, so as to cause the output current of each of the non-isolated buck/boost circuits to be equal.

Specifically, during the operation in the first direction, an output voltage at the output end of the Direct Current to Direct Current (DCDC) converter is sampled to obtain an output voltage sampling value, and the controller compares a preset voltage reference value with the output voltage sampling value to generate a first current reference value. The output current of each of the non-isolated buck/boost circuits is sampled to obtain the output current sampling value of each of the non-isolated buck/boost circuits, and the controller takes the first current reference value as a common current reference for the non-isolated buck/boost circuits, and adjusts a duty ratio of each of the non-isolated buck/boost circuits by comparing the first current reference value with the output current sampling value of each of the non-isolated buck/boost circuits to cause the output current of each of the non-isolated buck/boost circuits to be equal. In which, the preset voltage reference value is set according to actual needs, and is not limited in the embodiments of the present disclosure.

For example,FIG.15is a control diagram of an operation in a first direction according to a fifteenth embodiment of the present disclosure. As illustrated inFIG.15, a preset voltage reference value is compared with an output voltage sampling value, and according to a comparison result thereof, an output voltage regulator generates a first current reference value. By regulating the output current of each of the non-isolated buck/boost circuits according to the comparison result of the first current reference value and the output current sampling value of each of the non-isolated buck/boost circuits, the duty ratio of each of the non-isolated buck/boost circuits is adjusted, so as to regulate the output current of each of the non-isolated buck/boost circuits, thereby causing the output current of each of the non-isolated buck/boost circuits to be equal.

Based on the above embodiments, further, controlling each of the non-isolated buck/boost circuits to work in a DC boost state and causing output current of each of the non-isolated buck/boost circuits to be equal includes:controlling each of the non-isolated buck/boost circuits to generate an intermediate bus voltage of each of the bidirectional isolated DCDC units, and obtaining a second current reference value according to an intermediate bus voltage reference value and an intermediate bus voltage sampling value of each of the bidirectional isolated DCDC units;adjusting a duty ratio of each of the non-isolated buck/boost circuits according to the second current reference value and an input current sampling value of each of the non-isolated buck/boost circuits, so as to cause input current of each of the non-isolated buck/boost circuits to be equal.

Specifically, during an operation in a second direction, the controller controls each of the non-isolated buck/boost circuits to boost an external input voltage to generate an intermediate bus voltage of each of the bidirectional isolated DCDC units, i.e., an output voltage of each of the bidirectional isolated DCDC units. An intermediate bus voltage sampling value of each of the bidirectional isolated DCDC units may be obtained by sampling the intermediate bus voltage of each of the bidirectional isolated DCDC units, and the controller may calculate an average value of the intermediate bus voltage sampling values of the bidirectional isolated DCDC units and take the calculated average value as an intermediate bus voltage comparison value, or acquire a maximum value of the intermediate bus voltage sampling values of the bidirectional isolated DCDC units as the intermediate bus voltage comparison value. The controller compares an intermediate bus voltage reference value with the intermediate bus voltage comparison value to generate a second current reference value as a common current reference for the non-isolated buck/boost circuits.

An input current sampling value of each of the non-isolated buck/boost circuits may be obtained by sampling the input current of each of the non-isolated buck/boost circuits. The controller adjusts a duty ratio of each of the non-isolated buck/boost circuits by comparing the second current reference value with the input current sampling value of each of the non-isolated buck/boost circuits, so as to cause the output current of each of the non-isolated buck/boost circuits to be equal. In which, the intermediate bus voltage reference value is set according to actual needs and is not limited in the embodiments of the present disclosure.

For example,FIG.16is a control diagram of an operation in a second direction according to a sixteenth embodiment of the present disclosure. As illustrated inFIG.16, an intermediate bus voltage sampling value of each of the bidirectional isolated DCDC units is obtained, and then an average value is calculated to obtain an intermediate bus voltage comparison value. Next, an intermediate bus voltage reference value is compared with the intermediate bus voltage comparison value, and according to a comparison result thereof, an intermediate bus voltage regulator generates a second current reference value. By regulating the input current of each of the non-isolated buck/boost circuits according to the comparison result of the second current reference value and the input current sampling value of each of the non-isolated buck/boost circuits, the duty ratio of each of the non-isolated buck/boost circuits is adjusted, so as to regulate the output current of each of the non-isolated buck/boost circuits, thereby causing the output current of each of the non-isolated buck/boost circuits to be equal.

In the present disclosure, descriptions referring to the terms such as ‘an embodiment’, ‘a specific embodiment’, ‘some embodiments’, ‘for example’, ‘an example’, ‘a specific example’ or ‘some examples’ mean that the specific features, structures, materials or characteristics described in connection with the embodiment(s) or example(s) are included in at least one embodiment or example of the present disclosure. In the present disclosure, the schematic expressions of the above terms do not necessarily refer to a same embodiment or example. Further, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

When a circuit or electronic component is referred to as being ‘connected to’ or ‘accessing’ another circuit or electronic component, it should be understood that the circuit or electronic component may be directly connected to or access another circuit or electronic component, or there may be still another circuit or electronic component therebetween.

The above specific embodiments further explain the objectives, technical solutions and advantageous effects of the present disclosure in detail. It should be understood that those described above are only specific embodiments of the present disclosure, and are not intended to limit the protection scope of the present disclosure. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present disclosure should fall within the protection scope of the present disclosure.