TWI776564B - Single-phase and three-phase compatible ac-dc conversion circuit and method of controlling discharge thereof - Google Patents

Abstract

A single-phase and three-phase compatible AC-DC conversion circuit is provided between an AC side and a DC side. The AC side has a three-phase power source. The AC-DC conversion circuit includes a first switching element, a second switching element, a third switching element, three switch bridge arms, a fourth switching element, a pre-charge resistor, a capacitor bank, and a control unit. Each switch bridge arm has upper switches and lower switches connected in series. The fourth switching element is coupled between a first phase of the three-phase power source and a common-connected node corresponding to a second phase of the three-phase power source. The control unit turns on the fourth switching element, turns on the upper switch coupled to the first switching element, and turns on the lower switch coupled to the fourth switching element to provide a discharge path so that the capacitor bank discharges through the pre-charge resistor on the discharge path.

Description

Single-phase and three-phase compatible AC-DC conversion circuit and discharge control method thereof

The invention relates to an AC-DC conversion circuit and a discharge control method thereof, in particular to a single-phase and three-phase compatible AC-DC conversion circuit and a discharge control method thereof.

In response to changes in the global environment, countries around the world have gradually attached importance to the concept of green energy and environmental protection. With the vigorous development of electrification and intelligent technologies in recent years, various car manufacturers have also begun to actively develop electric vehicles (EVs) to reduce carbon emissions. For electric vehicles, the on-board charger is the core, which is mainly responsible for transferring charging energy to the high-voltage battery. In addition, with the continuous development of electric vehicles, the battery cruising range is increasing, and the requirements for charging power are also increasing. The original single-phase charger is gradually developing into a three-phase charger. Considering that users may encounter different Charging conditions, the on-board charger with single-phase and three-phase (compatible) functions will bring more convenience to users.

However, it should be noted that when the on-board charger stops charging, there is still energy in the capacitance of its internal circuit. Considering the operational safety of users and maintenance technicians, a discharge path needs to be provided to release this energy. Generally speaking, the energy release methods can be divided into passive discharging and active discharging.

The former (passive discharge) can use the dummy load of the internal circuit of the on-board charger for natural discharge, however, the discharge time will be quite long. The latter (active discharge) can use an additional parallel circuit with power switch switching to release the capacitor energy, so that the shortest discharge can be obtained time. However, using the active discharge method will increase the circuit cost and increase the complexity of circuit control because additional circuits are required.

Therefore, how to design a single-phase and three-phase compatible AC-DC conversion circuit and its discharge control method to solve the problems and technical bottlenecks in the prior art is an important subject studied by the present inventor.

One object of the present invention is to provide a single-phase and three-phase compatible AC-DC conversion circuit with discharge control, which solves the problems of the prior art.

In order to achieve the purpose disclosed above, the single-phase and three-phase compatible AC-DC conversion circuit with discharge control proposed by the present invention is arranged between the AC side and the DC side, and the AC side has a three-phase power supply. The AC-DC conversion circuit with discharge control includes a first switching element, a second switching element, a third switching element, a switch bridge arm group, a fourth switching element, a pre-charging resistor, a capacitor group and a control unit. The switch bridge arm group includes three groups of switch bridge arms. Each switch bridge arm includes an upper switch and a lower switch connected in series; the plurality of common contacts of the upper switch and the corresponding lower switch are respectively coupled to the three-phase power supply through the first switching element, the second switching element and the third switching element. The fourth switching element is coupled between the first phase of the three-phase power supply and the common contact of the switch bridge arms corresponding to the second phase of the three-phase power supply. The pre-charging resistor is coupled in parallel with the first switching element. The capacitor group is coupled to the switch bridge arm group in parallel to form a DC side. The control unit controls the conduction of the fourth switching element, the conduction of the upper switch of the switching bridge arm coupled to the first switching element, and the conduction of the lower switch of the switching bridge arm coupled to the fourth switching element to provide a discharge path, so that the capacitor bank can pass through The precharge resistor on the discharge path discharges.

With the proposed single-phase and three-phase compatible AC-DC conversion circuit with discharge control, single-phase and three-phase compatible charging can be completed, and the active charging can be realized without additional circuit components. In addition, in order to prevent the large current generated by the instantaneous conduction of the power switch element from causing damage to its own elements and pre-charge resistors, the switching technology is introduced to improve it to control the pulse width modulation and optimize it in time to adjust the power switch. The duty cycle of the components can not only effectively reduce the current stress of the power switching components, but also improve the tolerance and system reliability of the power switching components.

Another object of the present invention is to provide a charging and discharging control method of a single-phase and three-phase compatible AC-DC conversion circuit to solve the problems of the prior art.

In order to achieve the purpose disclosed above, the charging and discharging control method of a single-phase and three-phase compatible AC-DC conversion circuit proposed by the present invention, wherein the AC-DC conversion circuit receives the AC power supply; the AC-DC conversion circuit comprises: three groups of switch bridge arms, a fourth switching element, a pre-charging resistor and a capacitor group; each switch bridge arm includes an upper switch and a lower switch connected in series; the plurality of common contacts of the upper switch and the corresponding lower switch respectively pass through the first switching element, the second switching element and the third switching element The switching element is coupled to the three-phase power supply; the fourth switching element is coupled between the first phase of the three-phase power supply and the common point of the switch bridge arm corresponding to the second phase of the three-phase power supply; the pre-charging resistor is coupled to the first phase in parallel The switch element; the capacitor group is coupled to each switch bridge arm in parallel. The discharge control method includes: (a), the AC power supply charges the capacitor bank in a single-phase or three-phase manner; (b), when it is determined that the capacitor bank is about to discharge, controlling the fourth switching element to conduct; (c), controlling the coupling The upper switch of the switching bridge arm connected to the first switching element is turned on, and the lower switch of the switching bridge arm coupled to the fourth switching element is controlled to be turned on to provide a discharge path; and (d), the capacitor bank is discharged through the precharge resistor on the discharge path .

The single-phase and three-phase compatible charging can be completed by the proposed charging and discharging control method of the AC-DC conversion circuit that is compatible with single-phase and three-phase, and the function of active discharge can be realized without additional circuit components. , In order to prevent the large current generated by the instantaneous conduction of the power switching element from causing damage to its own elements and pre-charging resistors, the switching technology is introduced to improve it to control the timely optimization of the pulse width modulation and adjust the duty cycle of the power switching element. Not only can the current stress of the power switching element be effectively reduced, but also the tolerance of the power switching element and the system reliability can be improved.

In order to further understand the technology, means and effect adopted by the present invention to achieve the predetermined purpose, please refer to the following detailed description and accompanying drawings of the present invention. For specific understanding, however, the accompanying drawings are only provided for reference and description, and are not intended to limit the present invention.

S _AC : AC side

S _DC : DC side

V _L1N : first phase voltage

V _L2N : second phase voltage

V _L3N : third phase voltage

N _AC1 : the first AC node

N _AC2 : Second AC Node

N _AC3 : The third AC node

N: neutral node

10: Switch bridge arm group

20: Diode bridge arm

30: Capacitor bank

40: Control unit

11: The first switch bridge arm

12: Second switch bridge arm

13: The third switch bridge arm

Q ₁ : The first switch

Q ₂ : Second switch

Q ₃ : The third switch

Q ₄ : Fourth switch

Q ₅ : Fifth switch

Q ₆ : Sixth switch

D ₁ : first diode

D ₂ : Second diode

C ₁ : the first capacitor

C ₂ : second capacitor

N ₁ : the first node

N ₂ : second node

N ₃ : the third node

N ₄ : Fourth node

N ₅ : fifth node

RL ₁ : first switching element

RL ₂ : second switching element

RL ₃ : the third switching element

RL ₄ : Fourth switching element

RL ₅ : Fifth switching element

RL ₆ : sixth switching element

RL ₇ : seventh switching element

RL ₈ : Eighth switching element

R ₁ : Precharge resistor

L ₁ : first phase inductance

L ₂ : The second phase inductance

L ₃ : The third phase inductance

S _CON : Control signal

Fig. 1 is a circuit diagram of the single-phase and three-phase compatible AC-DC conversion circuit of the present invention.

FIG. 2 is a circuit diagram of the state of the switching elements when the single-phase and three-phase compatible AC-DC conversion circuit of the present invention is in single-phase charging operation.

FIG. 3 is a circuit diagram of the state of the switching elements when the single-phase and three-phase compatible AC-DC conversion circuit of the present invention is in a three-phase charging operation.

FIG. 4 is a circuit diagram of the state of the switching element when the single-phase and three-phase compatible AC-DC conversion circuit of the present invention is in discharge operation.

FIG. 5 is a circuit diagram of the current path when the single-phase and three-phase compatible AC-DC conversion circuit of the present invention is in discharge operation.

FIG. 6 is a flow chart of the discharge control method of the single-phase and three-phase compatible AC-DC conversion circuit of the present invention.

The technical content and detailed description of the present invention are described as follows in conjunction with the drawings.

Please refer to FIG. 1 , which is a circuit diagram of the single-phase and three-phase compatible AC-DC conversion circuit of the present invention. The AC-DC conversion circuit is configured between the AC side S _AC and the DC side S _DC . Wherein, the AC side S _AC is used to provide an AC power supply, such as a three-phase AC power supply or a single-phase AC power supply, which will be described in detail later. Therefore, the single-phase and three-phase compatible AC-DC conversion circuit of the present invention is a single-phase and three-phase (compatible) AC-DC conversion circuit. In addition, in different embodiments, it is a better implementation that a single-phase and three-phase (compatible) AC-DC conversion circuit can be a bidirectional circuit structure, but the present invention is not limited thereto.

Since the AC side S _AC can provide three-phase AC power and single-phase AC power, the AC side S _AC has a first AC node N _AC1 , a second AC node N _AC2 , a third AC node N _AC3 and a neutral node N. Taking a three-phase power supply as an example, the first phase voltage _VL1N of the three-phase power supply is arranged between the first AC node N _AC1 and the neutral node N, and the second phase voltage _VL2N of the three-phase power supply is arranged at the second AC node N Between _AC2 and the neutral node N, and the third phase voltage _VL3N of the three-phase power supply is arranged between the third AC node N _AC3 and the neutral node N.

The single-phase and three-phase compatible AC-DC conversion circuit includes a switch bridge arm group 10 , a fourth switching element RL ₄ , a fifth switching element RL ₅ , a pre-charging resistor R ₁ , a diode bridge arm 20 , a capacitor group 30 and a control unit 40.

The switch bridge arm group 10 includes three groups of parallel switch bridge arms, which are a first switch bridge arm 11 , a second switch bridge arm 12 and a third switch bridge arm 13 respectively. The first switch bridge arm 11 includes a first switch Q ₁ and a second switch Q ₂ that are commonly connected to the first node N ₁ , and the first node N ₁ is coupled to the first AC node N _AC1 through the first switching element RL ₁ . When the first switching element RL ₁ is turned on, the first node N ₁ can be coupled to the first phase voltage V _L1N through the first phase inductor L ₁ . The second switch bridge arm 12 includes a third switch Q ₃ and a fourth switch Q ₄ that are commonly connected to the second node N ₂ , and the second node N ₂ is coupled to the second AC node N _AC2 through the second switching element RL ₂ . When the second switching element RL ₂ is turned on, the second node N ₂ can be coupled to the second phase voltage V _L2N through the second phase inductor L ₂ . The third switch bridge arm 13 includes a fifth switch Q ₅ and a sixth switch Q ₆ that are commonly connected to the third node N ₃ , and the third node N ₃ is coupled to the third AC node N _AC3 through the third switching element RL ₃ . When the third switching element RL ₃ is turned on, the third node N ₃ can be coupled to the third phase voltage V _L3N through the third phase inductor L ₃ .

The fourth switching element RL ₄ is coupled between the first AC node N _AC1 and the second node N ₂ , that is, when the fourth switching element RL ₄ is turned on, it is overlapped (cross-connected) in the three-phase power supply between the first phase loop and the second phase loop. The fifth switching element RL ₅ is coupled between the first AC node N _AC1 and the third node N ₃ , that is, when the fifth switching element RL ₅ is turned on, it is overlapped (crossed) in the three-phase power supply between the first phase loop and the third phase loop. The above switching element can be implemented using a relay.

The pre-charging resistor R ₁ is coupled to the first switching element RL ₁ in parallel. When the electric vehicle (such as an electric vehicle) is in the charging process, the AC-DC conversion circuit plays the role of converting the three-phase or single-phase AC power of the AC side S _AC to the DC power output at the DC side S _DC to charge the electric vehicle. . Therefore, the pre-charging resistor R1 provides suppression of large currents, such as inrush currents, at the beginning of _a charging operation, such as when a user starts charging an electric vehicle. The present invention discharges the energy stored in the capacitor of the DC side S _DC after the high voltage is accumulated after charging, and the pre-charging resistor R ₁ is used as a component for providing a discharge path, so the pre-charging resistor R ₁ is not in the discharge process. It plays the role of a discharge resistor, that is, during the discharge operation, no additional circuit elements are added, and the existing circuit structure in the pre-charge process is used to discharge the stored energy of the capacitor. As for the detailed description _of the operation of the precharge resistor R1, it will be described later.

The diode bridge arm 20 is coupled to the switch bridge arm group 10 in parallel. In this embodiment, the diode bridge arm 20 includes a first diode D ₁ and a second diode D ₂ coupled to the fourth node N ₄ in series with the first diode D ₁ . In applications with different current resistance, each diode of the diode bridge arm 20 can also be connected in parallel with a plurality of diodes, so the diode bridge arm 20 shown in FIG. 1 is not limited.

The capacitor group 30 is coupled to the diode bridge arm 20 in parallel to form the DC side S _DC . In this embodiment, the capacitor group 30 includes a first capacitor C ₁ and a second capacitor C ₂ coupled to the fifth node N ₅ in series with the first capacitor C ₁ . In the application of electric vehicle charging, the capacitor bank 30 is used to store the DC power obtained by converting the AC-DC conversion circuit to the three-phase or single-phase AC power, so that the DC power output by the DC side S _DC can be used by the next-stage conversion circuit. , to charge the battery of the electric vehicle.

The control unit 40 provides the control signal S _CON . Since the switches Q ₁ ˜Q ₆ of the switch arms 11 , 12 , and 13 and the switching elements RL ₁ ˜RL ₈ are all controlled by the control unit 40 to be turned on and off, the shown control signal S _CON includes a plurality of The signals corresponding to the control switches Q ₁ to Q ₆ and the switching elements RL ₁ to RL ₈ respectively, will be described together first.

In addition, the single-phase and three-phase compatible AC-DC conversion circuit further includes a sixth switching element RL ₆ and a seventh switching element RL ₇ . One end of the _sixth switching element RL6 is coupled to the diode bridge arm 20, and the other end is coupled to the neutral node N with the _seventh switching element RL7. Since the present invention is a single-phase and three-phase (compatible) AC-DC conversion circuit, the sixth switching element RL ₆ and the seventh switching element RL ₇ are used for controlling the single-phase and three-phase power supply, and are also used for control. That is, when the AC side S _AC is powered by a single-phase AC power supply, the sixth switching element RL ₆ is controlled to be turned on (see FIG. 2 ), or when the AC side S _AC is powered by a three-phase AC power supply, the seventh switching element RL 6 is controlled to be turned on. The switching element RL ₇ is turned on (see FIG. 3 ), which will be described in detail later.

In addition, the single-phase and three-phase compatible AC-DC conversion circuit further includes an eighth switching element RL ₈ . The eighth switching element RL ₈ is coupled to the pre-charging resistor R ₁ in series to form a series structure, and the series structure is coupled to the first switching element RL ₁ in parallel. By arranging the eighth switching element RL ₈ , the purpose of disconnecting the pre-charging resistor R ₁ can be further achieved. However, the eighth switching element RL ₈ can also be omitted.

The technical feature of the present invention is that with the proposed AC-DC conversion circuit and control method, single-phase and three-phase compatible charging can be completed without additional circuit elements, and only the on-board charger internal circuit power switch elements are used for pre-charging The resistor R ₁ can realize the function of active discharge. In addition, in order to prevent the high current generated by the instantaneous conduction of the power switch element from causing damage to its own element and the pre-charging resistor R ₁ , a switching technique is introduced for improvement. , in order to control the pulse width modulation (PWM) to optimize in time and adjust the duty cycle of the power switch element, that is, the ratio of the on and off time, which can not only effectively reduce the current stress of the power switch element , and can also improve the tolerance of power switching components and system reliability.

When the on-board charger is running, it can be divided into single-phase and three-phase circuit operation according to the input terminal conditions of the charging pile. Please refer to FIG. 2 , which is a circuit diagram of the state of the switching element when the single-phase and three-phase compatible AC-DC conversion circuit of the present invention is in single-phase charging operation. When the AC input is a single-phase voltage, the AC input has only two terminals. For example, taking the first phase voltage V _L1N as the power supply voltage as an example, the first switching element RL ₁ , the fourth switching element RL ₄ , The fifth switching element RL ₅ and the sixth switching element RL ₆ are switched to a turned-on state (the remaining switching elements are turned-off states), so that only the first phase voltage V _L1N passes through the AC and DC In the conversion circuit, each switch bridge arm of the switch bridge arm group 10 and the diode bridge arm 20 form a totem pole PFC circuit to realize the function of energy transfer. Therefore, although the AC input is a single-phase voltage, through the conduction of the fourth switching element RL ₄ and the fifth switching element RL ₅ , the three groups of parallel switch bridge arms of the switch bridge arm group 10 (ie, the first switch bridge arm) can be used. The arm 11 , the second switch arm 12 and the third switch arm 13 ) are commonly coupled to the first phase voltage V _L1N , the three groups of parallel switch arms all participate in the operation of the pulse width modulation control, and the parallel arms also Interleaved Control can further be used. Therefore, the output power can be increased by avoiding idleness of the bridge arms. It is worth mentioning that the _fifth switching element RL5 may be omitted depending on the actual power demand, in other words, the third switching bridge arm 13 may not be involved in the operation.

Please refer to FIG. 3 , which is a circuit diagram of the state of the switching elements when the single-phase and three-phase compatible AC-DC conversion circuit of the present invention is in a three-phase charging operation. When the AC input is a three-phase voltage condition, the first switching element RL ₁ , the second switching element RL ₂ , the third switching element RL ₃ , and the seventh switching element RL ₇ are switched to an on state (the rest of the switching elements are in an off state) ), in this way, the first-phase voltage _VL1N , the second-phase voltage _VL2N , and the third-phase voltage _VL3N all pass through the AC-DC conversion circuit, and the switch bridge arm group 10 and the capacitor group 30 form a half-bridge power factor correction (half bridge power factor correction) PFC) circuit topology operation to realize the function of energy transfer.

Regardless of whether the AC input is a single-phase or three-phase circuit operation, when the vehicle charger stops charging, the power capacitors (ie, the first capacitor C ₁ and the second capacitor C ₂ of the capacitor bank 30 ) still have energy. Considering the operational safety of users and maintenance technicians, it is still necessary to provide a discharge path in order to release this energy. Therefore, according to the above description, the original on-board charger internal circuit power switch element and the pre-charging resistor R ₁ are used to realize the function of active discharge, and the technical solution of the discharge operation is described in the following steps.

First, when the on-board charger stops charging, the first phase voltage V _L1N , the second phase voltage V _L2N , and the third phase voltage V _L3N are disconnected, and all switching elements return to the disconnected state, such as Figure 1.

Then, in order to establish an energy release path for the power capacitors (the first capacitor C ₁ and the second capacitor C ₂ ), the eighth switching element RL ₈ and the fourth switching element RL ₄ are switched to the conducting state and wait for the discharge operation to be started. As shown in FIG. 4 , it is a circuit diagram of the state of the switching element when the single-phase and three-phase compatible AC-DC conversion circuit of the present invention is in discharge operation.

Then, the discharge operation is started, as shown in FIG. 5 , which is a circuit diagram of the current path of the single-phase and three-phase compatible AC-DC conversion circuit of the present invention when the discharge operation is performed. At this time, the eighth switching element RL ₈ and the fourth switching element RL ₄ maintain the conducting state, and the first switch Q ₁ of the first switching bridge arm 11 and the fourth switch Q ₄ of the second switching bridge arm 12 are switched to the conducting state . Further, the duty cycle of the power switch element can be changed/adjusted in time through pulse width modulation (PWM), so that the power capacitor (the first capacitor C ₁ and the second capacitor C ₂ ) can be paired with each other. _Precharge resistor R1 for discharge. The discharge path is shown in the direction of the arrow shown in FIG. 5 , that is, the control unit 40 controls the discharge path for discharging the capacitor bank 30 to control the fourth switching element RL ₄ , the eighth switching element RL ₈ , and the first switch It is realized by the conduction _of Q1 and the _fourth switch Q4, so the discharge path from the capacitor bank 30 will pass through the _first switch Q1, the _eighth switching element RL8, the pre _- charging resistor R1, the _fourth switching element RL4 and the fourth switching element RL4. switch _Q4 . The eighth switching element RL ₈ can also be omitted and replaced by a short circuit, so the discharge path does not include the eighth switching element RL ₈ . Through the control of the duty cycle ratio and the switching frequency of the switch, the magnitude of the discharge current will be directly affected. Therefore, the discharge current can be suppressed by controlling the duty cycle ratio and the switching frequency of the switch.

Finally, when the voltages of the power capacitors (the first capacitor C ₁ and the second capacitor C ₂ ) are discharged to a safe voltage range (or safe operating area (SOA)), the active switching modulation strategy is terminated. Therefore, the first switch Q ₁ and the fourth switch Q ₄ maintain the off state, and all the switching elements (including the eighth switching element RL ₈ and the fourth switching element RL ₄ ) are switched to the off state, so the switches of the entire circuit, Switch the state of the device, as shown in Figure 1, the voltage of the power capacitor is slowly and continuously discharged.

Incidentally, the aforementioned AC-DC conversion circuit is only one embodiment, and not every element must be present, because the power conversion circuit can have different implementations. Taking FIG. 1 as an example, when the single-phase operation does not require much power application, the fifth switching element RL ₅ can be omitted. Alternatively, the diode bridge arm 20, the _sixth switching element RL6 and the _seventh switching element RL7 can also be omitted, and the fifth node _N5 is directly connected to the neutral node N, so that both single-phase operation and three-phase operation use a half-bridge The power factor correction circuit topology operates in a single-phase operation, where single-phase operation connects the AC phase to the two bridge arms, and three-phase operation connects each phase to the corresponding bridge arm. Therefore, the main spirit of the present invention is to use the switching element to achieve the charging operation compatible with single-phase and three-phase AC input, and after the charging is completed, the switch of the bridge arm, the switching element and the pre-charging resistor are used to form a discharge loop to discharge the capacitor. To achieve this purpose, it is not limited to use only the front-mounted AC-DC conversion circuit.

Please refer to FIG. 6 , which is a flow chart of the discharge control method of the single-phase and three-phase compatible AC-DC conversion circuit of the present invention. The invention discloses a charging and discharging control method of a single-phase and three-phase compatible AC-DC converting circuit, wherein the AC-DC converting circuit receives AC power. The AC-DC conversion circuit includes: three groups of switching bridge arms, a fourth switching element, a pre-charging resistor and a capacitor group. Each switch bridge arm includes an upper switch and a lower switch connected in series. The upper switches and the plurality of common contacts corresponding to the lower switches are respectively coupled to the AC power source through the first switching element, the second switching element and the third switching element. fourth switching element The element is coupled between the first phase of the AC power supply and the common contact of the switch bridge arms corresponding to the second phase of the AC power supply. The pre-charging resistor is coupled in parallel with the first switching element. The capacitor group is coupled to each switch bridge arm in parallel.

The discharge control method includes the following steps. First, the AC power source charges the capacitor bank in a single-phase or three-phase manner (S11). Then, when it is determined that the capacitor group is about to discharge, the fourth switching element is controlled to be turned on (S12). Then, the upper switch of the switching bridge arm coupled to the first switching element is controlled to be turned on, and the lower switch of the switching bridge arm coupled to the fourth switching element is controlled to be turned on to provide a discharge path ( S13 ). Then, the capacitor bank is discharged through the precharge resistor on the discharge path (S14).

Incidentally, the discharge control method provided by the present invention can correspond to the operation of the AC-DC conversion circuit that is compatible with single-phase and three-phase. Therefore, the specifics and details of the control method can be found in the corresponding description. More to say.

To sum up, the present invention has the following features and advantages:

1. Using the existing pre-charge circuit structure for charging operation, only the original power switch element and the pre-charge resistor R ₁ are used to realize the function of active discharge, so there is no need to add additional components, which can save the circuit cost and reduce the circuit size .

2. The power switch element in the internal circuit of the on-board charger is matched with the pre-charging resistor R ₁ , which can quickly discharge the voltage of the power capacitor (the first capacitor C ₁ and the second capacitor C ₂ ) to a safe voltage range, so as to improve the safety of the user and the user. Operational safety for maintenance technicians.

3. In order to prevent the large current generated by the instantaneous conduction of the power switching element from causing damage to its own elements and pre-charging resistors, the switching technology is introduced to improve it to control the timely optimization of pulse width modulation (PWM). Adjusting the duty cycle of the power switch element, that is, the ratio of the turn-on and turn-off time, can not only effectively reduce the current stress of the power switch element, but also improve the power switch element tolerance and system reliability.

The above descriptions are only detailed descriptions and drawings of preferred embodiments of the present invention, but the features of the present invention are not limited thereto, and are not intended to limit the present invention. The entire scope of the present invention should be defined as follows: The scope of the patent application shall prevail. All the embodiments that are in line with the spirit of the scope of the patent application of the present invention and similar variations thereof shall be included in the scope of the present invention. Changes or modifications can be covered by the following patent scope of this case.

S _AC : AC side

S _DC : DC side

V _L1N : first phase voltage

V _L2N : second phase voltage

V _L3N : third phase voltage

N _AC1 : the first AC node

N _AC2 : Second AC Node

N _AC3 : The third AC node

N: neutral node

10: Switch bridge arm group

20: Diode bridge arm

30: Capacitor bank

40: Control unit

11: The first switch bridge arm

12: Second switch bridge arm

13: The third switch bridge arm

Q ₁ : The first switch

Q ₂ : Second switch

Q ₃ : The third switch

Q ₄ : Fourth switch

Q ₅ : Fifth switch

Q ₆ : Sixth switch

D ₁ : first diode

D ₂ : Second diode

C ₁ : the first capacitor

C ₂ : second capacitor

N ₁ : the first node

N ₂ : second node

N ₃ : the third node

N ₄ : Fourth node

N ₅ : fifth node

RL ₁ : first switching element

RL ₂ : second switching element

RL ₃ : the third switching element

RL ₄ : Fourth switching element

RL ₅ : Fifth switching element

RL ₆ : sixth switching element

RL ₇ : seventh switching element

RL ₈ : Eighth switching element

R ₁ : Precharge resistor

L ₁ : first phase inductance

L ₂ : The second phase inductance

L ₃ : The third phase inductance

S _CON : Control signal

Claims (13)

A single-phase and three-phase compatible AC-DC conversion circuit is arranged between an AC side and a DC side, the AC side has a three-phase power supply, and the AC-DC conversion circuit comprises: a first switching element, a second switching element a switching element and a third switching element; a switch bridge arm group, comprising: a first switch bridge arm, including a first switch and a second switch coupled to the first switch element; a second switch bridge arm, including a third switch and a fourth switch coupled to the second switching element; and a third switch bridge arm including a fifth switch and a sixth switch coupled to the third switching element; wherein the first switch The common contact of the switch and the second switch is coupled to the three-phase power supply through the first switching element, the common contact of the third switch and the fourth switch is coupled to the three-phase power supply through the second switching element, and the The common contact of the fifth switch and the sixth switch is coupled to the three-phase power supply through the third switching element; a fourth switching element is coupled to a first phase of the three-phase power supply and a corresponding three-phase power supply between the common contacts of the switch bridge arms of a second phase; a precharge resistor coupled in parallel with the first switching element; a capacitor group coupled in parallel with the switch bridge arm set to form the DC side; and a control unit, which controls the fourth switching element to be turned on, and controls the first switch and the fourth switch to be turned on to provide a discharge path, so that the capacitor group is discharged through the precharge resistor on the discharge path. The single-phase and three-phase compatible AC-DC conversion circuit as claimed in claim 1, further comprising: a fifth switching element coupled to the first phase of the three-phase power supply and a third phase corresponding to the three-phase power supply between the common contacts of the switch bridge arms of the phases. The single-phase and three-phase compatible AC-DC conversion circuit as claimed in claim 1, further comprising: a diode bridge arm coupled to the switch bridge arm group in parallel; a sixth switching element coupled to the diode a bridge arm; and a seventh switching element coupled to the sixth switching element and a neutral node of the three-phase power supply. The single-phase and three-phase compatible AC-DC conversion circuit as claimed in claim 1, further comprising: an eighth switching element coupled in series with the pre-charging resistor to form a series structure, and the series structure is coupled in parallel with the first a switching element. The single-phase and three-phase compatible AC-DC conversion circuit according to claim 4, wherein the control unit controls the fourth switching element and the eighth switching element to conduct, and controls the first switch and the fourth switch to conduct, so that the The capacitor bank is discharged through the precharge resistor. The single-phase and three-phase compatible AC-DC conversion circuit as claimed in claim 1, wherein the control unit controls the first switching element and the fourth switching element to conduct, and controls the first switching bridge arm and the second switching bridge The arm moves to charge the first phase of the three-phase power supply to the capacitor bank. The single-phase and three-phase compatible AC-DC conversion circuit as claimed in claim 2, wherein the control unit controls the first switching element, the fourth switching element and the fifth switching element to conduct and control the first switching bridge arm , the second switch bridge arm and the third switch bridge arm act to make the first phase of the three-phase power supply charge the capacitor bank. The single-phase and three-phase compatible AC-DC conversion circuit as claimed in claim 1, wherein the control unit controls the first switching element, the second switching element and the third switching element to conduct, control The first switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch are controlled to operate, so that the three-phase power supply charges the capacitor bank. A charging and discharging control method of a single-phase and three-phase compatible AC-DC conversion circuit, the AC-DC conversion circuit receives an AC power source; the AC-DC conversion circuit comprises: three groups of switch bridge arms, a fourth switching element, and a pre-charging resistor and a capacitor bank; each of the switch bridge arms includes an upper switch and a lower switch connected in series; the plurality of common contacts of the upper switches and the corresponding lower switches respectively pass through the first switching element, the second switching element and the first switching element Three switching elements are coupled to the AC power supply; the fourth switching element is coupled between a first phase of the AC power supply and the common point of the switch bridge arm corresponding to a second phase of the AC power supply; The charging resistor is coupled to the first switching element in parallel; the capacitor group is coupled to each of the switch bridge arms in parallel; the discharge control method includes: (a), the AC power supply charges the capacitor group in a single-phase or three-phase manner; (b), when it is determined that the capacitor group is about to discharge, control the fourth switching element to be turned on; (c), control the upper switch of the switch bridge arm coupled to the first switching element to be turned on, and control the first switching element to be coupled The lower switch of the switch bridge arm of the four-switching element is turned on to provide a discharge path; and (d), the capacitor group is discharged through the precharge resistor on the discharge path. The charge-discharge control method according to claim 9, wherein the AC-DC conversion circuit further comprises an eighth switching element, which is coupled to the pre-charging resistor in series to form a series structure, and the series structure is coupled to the first switching element in parallel element; wherein in step (b), it further includes controlling the eighth switching element to be turned on. The charge-discharge control method as claimed in claim 9, wherein in step (a), the first switching element, the second switching element and the third switching element are controlled to be turned on, and the corresponding upper switch and the lower switch are controlled action to make the AC power supply charge the capacitor bank in a three-phase manner. The charge-discharge control method as claimed in claim 9, wherein in step (a), the first switching element and the fourth switching element are controlled to be turned on, and the corresponding upper switch and the lower switch are controlled to operate, so that the AC power supply A phase of charging the capacitor bank. The charge-discharge control method as claimed in claim 9, wherein the AC-DC conversion circuit further comprises a fifth switching element; in step (a), the first switching element, the fourth switching element and the fifth switching element are controlled The element is turned on, so that the three groups of switch bridge arms are commonly coupled to one phase of the AC power supply, so as to charge the capacitor group.

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