A kind of bleeder and pre-charging device and control method of low-power DC charger

Abstract

The application discloses a kind of small power DC charger's discharge and pre-charging device and control method, and the application belongs to DC charger control field, it is related to a kind of DC charger discharge and pre-charging device and control method technical field, solve the independent circuit of discharge and pre-charging of prior art, leading to high cost, large in size, and there is no discharge and pre-charging circuit in power module, when whole pile design needs to increase external circuit, and by main control module control, not only increase cost but also exist circuit failure risk technical problem;The application includes main control module, power module, battery system;Main control module is connected with power module and battery system communication;Power module output is connected with battery system input;Power module includes power unit, control unit, discharge pre-charging unit;Wherein discharge pre-charging unit has high-voltage pre-charging and high-voltage discharge control;The application can effectively reduce cost, reduce size, improve safety performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of direct current charger control, and relates to a discharge and pre-charging device and control method for a small-power direct current charger. BACKGROUND

[0002] With the popularization of new energy vehicles, the direct current charging market is also developing. At present, the output voltage range of the direct current charger is 200-1000V. Because the output of the charger is disconnected, a large-capacity capacitor is used to maintain the output stability. Therefore, from the safety point of view, the national standard requires that the output end of the charger needs to have a discharge control, and the output voltage needs to be discharged to below 60V within 1s after the charger is turned off. Under normal circumstances, a discharge resistor is added to the output end of the charger for active discharge.

[0003] With the attention to vehicle-to-grid interaction and the requirements of vehicle manufacturers on charging equipment, bidirectional direct current chargers have also entered the market. The charger with V2G / V2L function can realize the discharging function of the vehicle battery. Because of the existence of a large-capacity capacitor at the output end, directly powering the output end will cause a large current at the moment of power-on, which may cause the capacitor to be damaged by breakdown. In addition, there is a fuse at the output end, and this current will also cause the fuse to be damaged. Therefore, when the battery is discharging, a pre-charging circuit needs to be added to the output port for current limiting processing.

[0004] The existing technology uses independent circuits for discharge and pre-charging. This design method has high cost and large space occupation. In addition, some power modules do not have discharge and pre-charging circuits. When designing the whole pile, external circuits need to be added, and the control is performed by the main control module. This not only increases the cost but also causes unreasonable control timing, which leads to circuit failure.

[0005] The application provides a discharge and pre-charging device and control method for a small-power direct current charger to solve the above problems. SUMMARY

[0006] The application aims to solve at least one of the technical problems existing in the prior art. To this end, the application provides a discharge and pre-charging device and control method for a small-power direct current charger, which is used to solve the technical problems that the existing technology uses independent circuits for discharge and pre-charging, and some power modules do not have discharge and pre-charging circuits. When designing the whole pile, external circuits need to be added, and the control is performed by the main control module. This not only increases the cost but also causes circuit failure risk. The application provides a discharge and pre-charging device and control method for a direct current charger power module, which can not only help to reduce the cost and size, but also improve the safety of the system by controlling the power module to solve the above problems.

[0007] Due to the requirement of discharging the output voltage to below 60V within 1s after the charging machine is powered off from the security point of view, and directly powering on the output terminal will cause a large current at the power-on moment, which may cause the capacitor to be damaged by breakdown, so the discharge and pre-charge functions are needed.

[0008] To achieve the above purpose, the first aspect of the present application provides a discharge and pre-charge device and control method of a small power DC charger, comprising:

[0009] a main control module, a power module and a battery system;

[0010] The main control module is in communication connection with the power module and the battery system, and the communication mode can be CAN, MODBUS, EATHERCAT, serial port protocol, etc.

[0011] The power module is electrically connected with the battery system;

[0012] The main control module is used for receiving the state data of the battery system, analyzing the state data, and generating control instructions;

[0013] The power module is used for determining the working mode according to the control instructions; discharging and pre-charging control is performed according to the working mode to realize the charging and discharging of the battery system; wherein the working mode includes charging mode or discharging mode.

[0014] Further, the power module includes a control unit, a power unit and a discharge and pre-charge unit;

[0015] The power unit is electrically connected with the control unit and the discharge and pre-charge unit;

[0016] The control unit is electrically connected with the discharge and pre-charge unit;

[0017] The control unit is used for receiving the control instructions sent by the main control module, determining the working mode according to the control instructions, and rectifying and transforming the power unit according to the working mode;

[0018] The discharge and pre-charge unit is used for discharging and pre-charging control according to the working mode determined by the control unit.

[0019] Further, the input voltage of the power module is Vac;

[0020] The output end of the power unit is DC+ and DC-, and the voltage between DC+ and DC- is Vdc;

[0021] The input end of the discharge and pre-charge unit is Vin+ and Vin-, and the output end is Vout+ and Vout-, and the voltage between Vout+ and Vout- is Vbat;

[0022] The bleeder pre-charge unit comprises a first control element S1, a second control element S2, a third control element S3, a fourth control element S4, a circuit element D1 and a resistor R1;

[0023] The power unit output end is DC+ and DC-, and the voltage between DC+ and DC- is Vdc;

[0024] The bleeder pre-charge unit input end is Vin+ and Vin-, and the output end is Vout+ and Vout-, and the voltage between Vout+ and Vout- is Vbat;

[0025] DC+ is connected with Vin+; and DC- is connected with Vin-;

[0026] One end of the first control element S1 is connected with Vin+, and the other end is connected with Vout+;

[0027] One end of the resistor R1 is connected with Vin+, and the other end of the resistor R1 is connected with one end of the second control element S2 and one end of the third control element S3 respectively;

[0028] The other end of the second control element S2 is connected with Vout+, and the other end of the third control element S3 is connected with Vout-;

[0029] One end of the fourth control element S4 is connected with Vout+, and the other end is connected with the cathode of the circuit element D1;

[0030] The anode of the circuit element D1 is connected to Vin+;

[0031] The circuit element D1 is a unidirectional diode or a unidirectional thyristor;

[0032] Vin- is connected with Vout-.

[0033] Further, the first control element S1 is a relay or a MOS tube;

[0034] The second control element S2 is a relay or a MOS tube;

[0035] The third control element S3 is a relay or a MOS tube;

[0036] The fourth control element S4 is a relay or a MOS tube;

[0037] The circuit element D1 is a unidirectional diode or a unidirectional thyristor.

[0038] Another aspect of the present application is a bleeder and pre-charge control method of a small power DC charger, comprising:

[0039] The control unit receives the control instruction issued by the master control module, and determines the working mode according to the control instruction;

[0040] When the working mode is the charging mode, the following steps are included:

[0041] The first control element S1 is opened, and the fourth control element S4 is closed;

[0042] When the shutdown instruction sent by the control unit is received in the charging mode, it is determined whether the output Vdc exceeds the first threshold value. If the output Vdc exceeds the first threshold value, the bleeder control is performed.

[0043] When the working mode is the discharging mode, the following steps are included:

[0044] The pre-charge control is entered. The pre-charge control is performed by controlling the bleeder pre-charge unit, connecting a resistor in series in the discharging circuit, and reducing the current impact formed by the voltage of the battery system on the power module.

[0045] The voltage difference between Vdc and Vbat is continuously detected. When the voltage difference is less than the second threshold value, the pre-charge control is ended.

[0046] The voltage difference between Vdc and Vbat is continuously detected. When the voltage difference is less than the second threshold value, the first control element S1 is closed first, and then the second control element S2 is opened.

[0047] When the discharging mode is ended, the first control element S1 is opened according to the discharging shutdown instruction sent by the main control module.

[0048] It is determined whether the output Vdc exceeds the first threshold value. If the output Vdc exceeds the first threshold value, the bleeder control is performed.

[0049] Further, the bleeder control includes the following steps:

[0050] It is determined whether the output Vdc exceeds the first threshold value.

[0051] If the output Vdc exceeds the first threshold value, the second control element S2 is opened, and the third control element S3 is closed.

[0052] The Vdc voltage is continuously detected. When the voltage does not exceed the first threshold value and the duration does not exceed the third threshold value, the bleeder control is ended, and the third control element S3 is opened. When the voltage exceeds the first threshold value and the duration exceeds the third threshold value, the bleeder control is ended, the third control element S3 is opened, and the bleeder abnormality alarm is reported.

[0053] Further, the pre-charge control includes the following steps:

[0054] The first control element S1, the third control element S3, and the fourth control element S4 are opened, and the second control element S2 is closed.

[0055] Continuously detect the voltage difference between Vdc and Vbat, when the voltage difference is less than the second threshold, then close the first control element S1 first, and then open the second control element S2.

[0056] Compared with the prior art, the beneficial effects of the present application are:

[0057] 1. At present, with the popularity of electric vehicles, the cost performance, portability and safety of charging devices are needed, and the existing technology adopts independent circuit for discharge and pre-charging. This design method has high cost and large space occupation. The present application integrates the pre-charging and discharge circuit through the power module, which helps to reduce the cost and miniaturization design.

[0058] 2. At present, there is no discharge and pre-charging circuit in the power module, and external circuit needs to be added during the whole pile design, and controlled by the main control module. This not only increases the cost but also has the risk of circuit failure. The power module of the present application includes power unit, main control unit, discharge and pre-charging unit; it can quickly identify the demand for voltage reduction, which helps to shorten the voltage reduction time; at the same time, the power module controls to ensure the timely and reliable timing, avoids the burning of resistor, and improves the safety of the system. BRIEF DESCRIPTION OF DRAWINGS

[0059] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0060] Figure 1 It is the overall circuit layout of the present application;

[0061] Figure 2 It is the working flowchart of the embodiment of the present application;

[0062] Figure 3 It is the discharge flowchart of the embodiment of the present application;

[0063] Figure 4 It is the pre-charging flowchart of the embodiment of the present application. DETAILED DESCRIPTION

[0064] The technical solutions of the present application will be described below in conjunction with the embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0065] Please refer to Figure 1The application provides a bleeder and pre-charging device of a low-power direct-current charger in a further embodiment, comprising a main control module, a power module and a battery system;

[0066] The main control module is connected with the power module and the battery system through CAN protocol for signal transmission and through Cat6 twisted pair for connection.

[0067] The output end of the power module is connected with the input end of the battery system.

[0068] The power module comprises a control unit, a power unit and a bleeder and pre-charging unit.

[0069] The power unit is electrically connected with the control unit and the bleeder and pre-charging unit.

[0070] The control unit is electrically connected with the bleeder and pre-charging unit.

[0071] The control unit is used for receiving a control instruction sent by the main control module and determining a working mode according to the control instruction; and rectifying and transforming control is performed on the power unit according to the working mode.

[0072] The bleeder and pre-charging unit is used for performing bleeder and pre-charging control according to the working mode determined by the control unit.

[0073] The input voltage of the power module is Vac, and the voltage is 380V of three-phase industrial power supply.

[0074] The output end of the power unit is DC+ and DC-, and the input end of the bleeder and pre-charging unit is Vin+ and Vin-, and the output end is Vout+ and Vout-.

[0075] The bleeder and pre-charging unit comprises a first control element S1, a second control element S2, a third control element S3, a fourth control element S4, a circuit element D1 and a resistor R1.

[0076] DC+ is connected with Vin+.

[0077] DC- is connected with Vin-.

[0078] One end of the first control element S1 is connected with Vin+, and the other end is connected with Vout+.

[0079] One end of the second control element S2 is connected with Vout+, and the other end is connected with the resistor R1.

[0080] One end of the third control element S3 is connected with Vout-, and the other end is connected with the resistor R1.

[0081] One end of the fourth control element is connected with Vout+, and the other end is connected with the cathode of the circuit element D1.

[0082] The anode of the circuit element D1 is connected to Vin+.

[0083] The other end of resistor R1 is connected to DC+;

[0084] Vin- is directly connected to Vout-.

[0085] Furthermore, the first control element S1, the second control element S2, the third control element S3, and the fourth control element S4 are all relays.

[0086] Circuit element D1 is a unidirectional diode;

[0087] The resistance range of resistor R1 is 200Ω to 500Ω;

[0088] Please see Figure 2 In a further embodiment, this application provides a method for discharging and pre-charging a low-power DC charger, comprising:

[0089] Step S200: Determine the working mode by issuing command parameters through the main control module of the charger;

[0090] Step S210: If the instruction working mode is charging mode, disconnect the first control element S1, close the fourth control element S4, and connect a diode between Vin+ and Vout+ to prevent backflow.

[0091] Step S220: In charging mode, after receiving the power-off command from the charger main control module, the power module turns off the power transistor and then judges the magnitude of the voltage Vdc between the output DC+ and DC-.

[0092] Step S230: Discharge mode. In order to reduce the current impact of the battery system voltage on the power module, pre-charge control is entered.

[0093] Step S240: Pre-charge control, a resistor is connected in the circuit to reduce the voltage of the battery system;

[0094] Step S250: After the discharge is completed, upon receiving the discharge shutdown command from the main control module, the power module shuts down the power transistor, disconnects the first control element S1, and judges the magnitude of the voltage Vdc between the output DC+ and DC-.

[0095] Step S260: Determine whether the output Vdc exceeds the first threshold: if yes, proceed to step S270; if no, proceed to step S280.

[0096] Step S270: Perform discharge control;

[0097] Step S280: Do not perform discharge control;

[0098] Please see Figure 3The discharge control steps in the discharge and pre-charge method for a low-power DC charger provided in this application are as follows:

[0099] Step S300: Monitor the value of Vdc;

[0100] Step S310: Determine whether the output Vdc exceeds the first threshold: if yes, proceed to step S330; if no, proceed to step S320.

[0101] In this embodiment, the first threshold is set based on experience and actual conditions, and can be 60V;

[0102] Step S320: Discharge ends;

[0103] Step S330: Disconnect the second control element S2, close the third control element S3, and start the timing with a timing period of 10ms;

[0104] Step S340: Determine whether the duration exceeds the third threshold; if yes, proceed to step S350; if no, proceed to step S310.

[0105] In this embodiment, the third threshold is 1 second;

[0106] Step S350: End the discharge control, disconnect the third control element S3, and report a discharge abnormality alarm.

[0107] Please see Figure 4 The pre-charge control steps in the discharge and pre-charge method for a low-power DC charger provided in this application are as follows:

[0108] Step S400: Disconnect the first control element S1, the third control element S3, and the fourth control element S4, and close the second control element S2;

[0109] Step S410: Continuously detect the voltage difference between Vdc and Vbat, and determine whether the voltage difference is less than the second threshold; if yes, proceed to step S420; if no, proceed to step S400.

[0110] In this practical example, the second threshold is set based on experience and actual conditions, and can be 5V;

[0111] Step S420: Close the first control element S1, and after a delay of 200ms, open the second control element S2 to end the pre-charge control.

[0112] The working principle of this application is as follows: When the battery system is charging, in order to prevent reverse current flow, a unidirectional diode is connected during charging by controlling the pre-charge discharge unit;

[0113] At the end of charging, in order to quickly reduce the output voltage to below 60V, the pre-charge discharge unit is controlled to connect a resistor during the discharge process, so that the electrical energy is converted into heat energy and consumed, thus achieving rapid discharge.

[0114] During battery system discharge, in order to prevent excessive current from damaging the capacitor, a resistor is connected in the circuit by controlling the precharge discharge unit to reduce the current surge caused by the battery system voltage on the power module. When the voltage reaches a safe value, the resistor is removed by controlling the precharge discharge unit to achieve normal discharge.

[0115] The above embodiments are only used to illustrate the technical methods of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical methods of this application without departing from the spirit and scope of the technical methods of this application.

Claims

1. A discharge and pre-charge device for a low-power DC charger, characterized in that, Includes the main control module, power module, and battery system; The main control module is communicatively connected to the power module and the battery system, respectively. The power module is electrically connected to the battery system; The main control module is used to receive the status data of the battery system, analyze the status data, and generate control commands. The power module is used to determine the operating mode according to the control command; and to perform pre-charge control based on the operating mode to realize the charging and discharging of the battery system; wherein the operating mode includes a charging mode or a discharging mode. The power module includes a control unit, a power unit, and a discharge precharge unit; The power unit is electrically connected to the control unit and the discharge precharge unit; The control unit is electrically connected to the discharge precharge unit; The control unit is used to receive control commands sent by the main control module, determine the operating mode according to the control commands, and perform rectification and transformation control on the power unit according to the operating mode. The discharge pre-charge unit is used to perform internal circuit control according to the working mode determined by the control unit. The power module input voltage is Vac; The power unit outputs DC+ and DC-, and the voltage between DC+ and DC- is Vdc. The input terminals of the discharge precharge unit are Vin+ and Vin-, and the output terminals are Vout+ and Vout-. The voltage between Vout+ and Vout- is Vbat. The discharge pre-charge unit includes a first control element S1, a second control element S2, a third control element S3, a fourth control element S4, a circuit element D1, and a resistor R1. The DC+ is connected to the Vin+; the DC- is connected to the Vin-. One end of the first control element S1 is connected to Vin+, and the other end is connected to Vout+; One end of the resistor R1 is connected to Vin+, and the other end of the resistor R1 is connected to one end of the second control element S2 and one end of the third control element S3, respectively. The other end of the second control element S2 is connected to Vout+, and the other end of the third control element S3 is connected to Vout-. One end of the fourth control element S4 is connected to Vout+, and the other end is connected to the cathode of the circuit element D1; the anode of the circuit element D1 is connected to Vin+. The circuit element D1 is a unidirectional diode or a unidirectional thyristor; Vin- connects to Vout-.

2. The discharge and pre-charge device for a low-power DC charger according to claim 1, characterized in that, The first control element S1 is a relay or a MOSFET; The second control element S2 is a relay or a MOSFET; The third control element S3 is a relay or a MOSFET; The fourth control element S4 is a relay or a MOSFET.

3. A method for discharging and pre-charging control of a low-power DC charger, based on the discharging and pre-charging device for a low-power DC charger according to claim 1, characterized in that, include: The control unit receives control commands from the main control module and determines the operating mode based on the control commands. When the operating mode is charging mode, the following steps are included: Disconnect the first control element S1 and close the fourth control element S4; When a power-off command is received from the control unit in charging mode, it is determined whether the output Vdc exceeds the first threshold. If it exceeds the first threshold, discharge control is performed. When the operating mode is discharge mode, the following steps are included: Entering pre-charge control, the pre-charge control reduces the current surge of the battery system voltage on the power module by controlling the discharge pre-charge unit; The voltage difference between Vdc and Vbat is continuously monitored. When the voltage difference is less than the second threshold, the pre-charge control ends. When the discharge mode operation ends, the first control element S1 is disconnected according to the discharge shutdown command issued by the main control module; Determine whether Vdc exceeds the first threshold; if it does, perform discharge control.

4. A method for discharging and pre-charging control of a low-power DC charger according to claim 3, characterized in that, The discharge control includes the following steps: Determine if the output Vdc exceeds the first threshold; If Vdc exceeds the first threshold, the second control element S2 is disconnected and the third control element S3 is closed. The Vdc voltage is continuously monitored. If the voltage does not exceed the first threshold and the duration does not exceed the third threshold, the discharge control is terminated and the third control element S3 is disconnected. If the voltage exceeds the first threshold and the duration exceeds the third threshold, the discharge control is terminated, the third control element S3 is disconnected, and a discharge abnormality alarm is reported.

5. A method for discharging and pre-charging control of a low-power DC charger according to claim 3, characterized in that, The precharge control includes the following steps: Disconnect the first control element S1, the third control element S3, and the fourth control element S4, and close the second control element S2; The voltage difference between Vdc and Vbat is continuously monitored. When the voltage difference is less than the second threshold, the first control element S1 is closed first, and then the second control element S2 is opened, thus ending the pre-charging.

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