CN111251941A - Pre-charging device for high-voltage bus capacitor of new energy automobile - Google Patents
Pre-charging device for high-voltage bus capacitor of new energy automobile Download PDFInfo
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- CN111251941A CN111251941A CN202010238241.5A CN202010238241A CN111251941A CN 111251941 A CN111251941 A CN 111251941A CN 202010238241 A CN202010238241 A CN 202010238241A CN 111251941 A CN111251941 A CN 111251941A
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- 230000002457 bidirectional effect Effects 0.000 claims abstract description 33
- 238000006243 chemical reaction Methods 0.000 claims abstract description 33
- 238000005070 sampling Methods 0.000 claims abstract description 11
- 238000010586 diagram Methods 0.000 description 5
- 238000000034 method Methods 0.000 description 3
- 230000003071 parasitic effect Effects 0.000 description 2
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
- B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L3/00—Electric devices on electrically-propelled vehicles for safety purposes; Monitoring operating variables, e.g. speed, deceleration or energy consumption
- B60L3/0023—Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train
- B60L3/0046—Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train relating to electric energy storage systems, e.g. batteries or capacitors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
- H02M3/1582—Buck-boost converters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/72—Electric energy management in electromobility
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
A pre-charging device for a high-voltage bus capacitor of a new energy automobile comprises the high-voltage bus capacitor, a capacitor voltage sampling circuit, a bidirectional DC-DC conversion circuit, a charging power supply and a controller. Two ends of the high-voltage bus capacitor are respectively connected with the positive electrode and the negative electrode of the direct-current bus of the new energy automobile. The output end of the capacitor voltage sampling circuit is coupled with the input end of the controller. The bidirectional DC-DC conversion circuit is coupled between the DC bus capacitor and a charging power supply and comprises a Buck-Boost circuit, an inductor Lpre, a follow current element Dpre and a switching tube QsafeAnd a capacitance Cfafe. When the controller is in a pre-charging mode, the bidirectional DC-DC conversion circuit firstly charges the high-voltage bus capacitor in a voltage reduction mode, and charges the capacitor in the high-voltage bus capacitorAnd after the voltage reaches a preset threshold value, the bidirectional DC-DC conversion circuit charges the high-voltage bus capacitor in a boosting mode. The invention has simple structure, light weight, safety and reliability.
Description
Technical Field
The invention relates to the field of new energy automobiles, in particular to a pre-charging device of a high-voltage bus capacitor of a new energy automobile.
Background
As shown in fig. 1, an electric System of a hybrid vehicle generally includes a 48V high-voltage Battery pack 91, a Battery Management System (BMS) 92, a terminal box 93, a 48V high-voltage electrical device 94, and the like, and when the vehicle is started, the Battery Management System 92 controls the terminal box 93 to connect the 48V high-voltage Battery pack 91 and the 48V high-voltage electrical device 94, and the 48V high-voltage Battery pack 91 charges the 48V high-voltage electrical device 94. The 48V high voltage electrical appliance 94 may be a variety of high voltage electrical devices such as a high voltage DC-DC converter, an inverter, a vehicle charger, and the like. The high-voltage electric equipment is connected in parallel on a 48V high-voltage direct-current bus, and a 48V high-voltage bus capacitor C1 is usually arranged at the direct-current input end of the high-voltage electric equipment. In a 48V system of a hybrid vehicle, a BSG controller and other electric equipment are generally present, so that the electric capacity on a 48V high-voltage direct-current bus is very large, and a pre-charging circuit for pre-charging the 48V high-voltage bus capacitor is required to ensure the electric safety at the moment when a 48V high-voltage battery is turned on.
The conventional pre-charging circuit mainly comprises a pre-charging contactor 95 (usually a relay) and a pre-charging resistor 96, and the pre-charging resistor 96 limits the impact current when the 48V high-voltage battery is wrapped on the 48V high-voltage bus capacitor, but this causes heat loss of the resistor and the contactor, consumes the energy of the battery, and also causes a potential risk of thermal failure of parts. Although a pre-charging device of a high-voltage bus capacitor is disclosed for a pure electric vehicle in the prior art, a pre-charging resistor is not required, but since the voltage of a high-voltage battery of the pure electric vehicle is greater than 60V, a DC-DC converter of the pure electric vehicle is of an isolated type, and a topological structure of the pre-charging device is different from that of a 48V DC-DC converter of a hybrid electric vehicle shown in fig. 2, a pre-charging scheme of the high-voltage bus capacitor of the pure electric vehicle cannot be applied to the hybrid electric vehicle. Compared with an electric system of a hybrid electric vehicle, the 48V side capacitor of the common 48V DC-DC converter is small, the risk of pre-charging is low, and a pre-charging circuit is not required.
Disclosure of Invention
The invention aims to provide a pre-charging device of a high-voltage bus capacitor of a new energy automobile, which has the advantages of simple structure, low energy loss, safety and reliability.
The embodiment of the invention provides a pre-charging device for a high-voltage bus capacitor of a new energy automobile, wherein the new energy automobile is provided with a direct-current bus and a charging power supply, one end of the high-voltage bus capacitor is connected with the positive electrode of the direct-current bus of the new energy automobile, and the other end of the high-voltage bus capacitor is connected with the negative electrode of the direct-current bus of the new energy automobile; the pre-charging device comprises a bidirectional DC-DC conversion circuit, a capacitor voltage sampling circuit and a controller; the bidirectional DC-DC conversion circuit is coupled between the high-voltage bus capacitor and the charging power supply, so that the charging power supply can charge the high-voltage bus capacitor through the bidirectional DC-DC conversion circuit; the output end of the capacitor voltage sampling circuit is coupled with the input end of the controller, and the capacitor voltage sampling circuit is used for collecting the voltage of the high-voltage bus capacitor; the bidirectional DC-DC conversion circuit is characterized by comprising a Buck-Boost circuit, an inductor Lpre, a follow current element Dpre and a switching tube QsafeAnd a capacitance Cfafe; a first input/output end of the Buck-Boost circuit is connected with the high-voltage bus capacitor in parallel, and the anode of a second input/output end of the Buck-Boost circuit is connected with one end of an inductor Lpre; the other end of the inductor Lpre and the switching tube QsafeThe second conducting end of the first conducting terminal is connected; switch tube QsafeThe first conducting end of the first conducting terminal is connected with the anode of the charging power supply; the negative end of the follow current element Dpre is connected with the other end of the inductor Lpre and the switching tube QsafeAnd one end of the capacitor Csafe is connected to the switching tube QsafeThe first conducting end of the first conducting terminal is connected with the common contact point of the positive electrode of the charging power supply; the negative electrode of the second input/output end of the Buck-Boost circuit, the positive electrode end of the follow current element Dpre and the negative electrode of the charging power supply are respectively connected with the negative electrode of the direct current bus; the controller is respectively connected with the control end of the Buck-Boost circuit and the switching tube QsafeThe control end of the controller is connected; the controller can control the bidirectional DC-DC conversion circuit to work in a pre-charging mode, the bidirectional DC-DC conversion circuit firstly charges the high-voltage bus capacitor in a voltage reduction mode in the pre-charging mode, and the bidirectional DC-DC conversion circuit charges the high-voltage bus capacitor in a voltage boosting mode after the voltage of the high-voltage bus capacitor reaches a preset threshold value until the voltage of the high-voltage bus capacitor reaches a preset charging voltage value.
The invention has at least the following technical effects:
1. according to the pre-charging device provided by the embodiment of the invention, the branch circuits of the inductor Lpre and the follow current element Dpre are added to the basic topological structure of the high-voltage DC-DC converter of the existing new energy automobile, so that the two-stage pre-charging function is realized; the first stage is converted into a Buck (voltage reduction) circuit, a basic voltage is established on the high-voltage bus capacitor, and after the basic voltage is established, the second stage is switched into a Boost (voltage boosting) circuit, so that the high-voltage bus capacitor is charged to a final target voltage, the generation of impact current during charging is avoided, and the safety and reliability of the charging process are improved;
2. the pre-charging device provided by the embodiment of the invention has the advantages that the basic topological structure of the high-voltage DC-DC converter is slightly changed, and the circuit structure and the control process are simple;
3. according to the pre-charging device provided by the embodiment of the invention, the pre-charging resistor is not arranged, the energy loss is low, and the charging efficiency is improved.
Drawings
Fig. 1 shows a schematic block diagram of an electrical system of a conventional hybrid vehicle.
Fig. 2 shows a schematic diagram of a 48V DC-DC converter circuit of a conventional hybrid vehicle.
Fig. 3 shows a schematic circuit diagram of an embodiment of the precharge device according to the present invention.
Fig. 4 shows the operation of the pre-charging device in the buck mode according to an embodiment of the present invention.
Fig. 5 shows an operation timing diagram of the switch tube of the pre-charging device in the step-down mode according to an embodiment of the invention.
Fig. 6 shows the operation principle of the precharge device in the boost mode according to an embodiment of the present invention.
Fig. 7 shows an operation timing diagram of the switch tube of the pre-charging device in the boost mode according to an embodiment of the invention.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments.
Please refer to fig. 3. The pre-charging device for the high-voltage bus capacitor of the new energy automobile comprises a capacitor voltage sampling circuit 2, a bidirectional DC-DC conversion circuit 3 and a controller 4.
The capacitor voltage sampling circuit 2 is used for collecting the voltage of the high-voltage bus capacitor C48, and the output end of the capacitor voltage sampling circuit 2 is coupled with the input end of the controller 4 so as to send the collected voltage signal of the high-voltage bus capacitor C48 to the controller 4. One end of the high-voltage bus capacitor C48 is connected with the positive electrode of the direct-current bus of the new energy automobile, and the other end of the high-voltage bus capacitor C48 is connected with the negative electrode of the direct-current bus of the new energy automobile.
The bidirectional DC-DC conversion circuit 3 is coupled between the high-voltage bus capacitor C48 and the charging power supply V12_batSo that the charging power supply V12_batThe high-voltage bus capacitor C48 can be charged by the bidirectional DC-DC converter circuit 3. R in the figureLDRepresenting the load. The bidirectional DC-DC conversion circuit 3 comprises a Buck-Boost circuit 31, an inductor Lpre, a follow current element Dpre and a switching tube QsafeAnd a capacitance Cfafe.
A first input/output end of the Buck-Boost circuit 31 is connected with a high-voltage bus capacitor C48 in parallel, and the positive electrode of a second input/output end of the Buck-Boost circuit 31 is connected with one end of an inductor Lpre; the other end of the inductor Lpre and the switching tube QsafeIs connected with the second conducting end of the switching tube QsafeThe first conducting terminal and the charging power supply V12_batThe positive electrodes of the two electrodes are connected; the negative end of the follow current element Dpre is connected with the other end of the inductor Lpre and the switching tube QsafeAnd one end of the capacitor Csafe is connected to the switching tube QsafeThe first conducting terminal and the charging power supply V12_batThe common junction of the positive electrode of (1); the negative electrode of the second input/output terminal of the Buck-Boost circuit 31, the positive electrode of the freewheel element Dpre, the other end of the capacitor Csafe, and the charging power supply V12_batAre connected to the negative poles of the dc bus bars, respectively.
The controller 4 is respectively connected with the control end of the Buck-Boost circuit 31 and the switching tube QsafeIs connected with the control end of the controller. The controller 4 can control the bidirectional DC-DC conversion circuit 3 to operate in a pre-charging mode, and in the pre-charging mode, the bidirectional DC-DC conversion circuit 3 firstly performs a voltage reduction on the high-voltage bus capacitor C48And charging, namely charging the high-voltage bus capacitor C48 by the bidirectional DC-DC conversion circuit 3 in a boosting mode after the voltage of the high-voltage bus capacitor reaches a preset threshold value until the voltage of the high-voltage bus capacitor C48 reaches a preset charging voltage value.
In the present embodiment, as shown in fig. 3, the Buck-Boost circuit 31 includes a bridge arm, an inductor Lf, and a capacitor C12.
The bridge arm comprises a switch tube Qh and a switch tube Ql, the switch tube Qh and the switch tube Ql are provided with body diodes, a first conduction end of the switch tube Qh is connected with one end of a high-voltage bus capacitor C48, a second conduction end of the switch tube Qh is connected with the first conduction end of the switch tube Ql, and the second conduction end of the switch tube Ql is connected with the other end of the high-voltage bus capacitor C48. One end of the inductor Lf is connected to a common junction point of the second conduction end of the switching tube Qh and the first conduction end of the switching tube Ql, and the other end of the inductor Lf is connected to one end of the inductor Lpre; one end of the capacitor C12 is connected to a common junction point of the other end of the inductor Lf and one end of the inductor Lpre. The other end of the capacitor C12 is connected to the negative electrode of the dc bus.
The controller 4 is respectively connected with the control end of the switch tube Qh and the control end of the switch tube Ql, and the controller 4 is used for controlling the switch tube Qh and the switch tube Ql to be normally opened and controlling the capacitor Csafe and the switch tube QsafeThe follow current element Dpre, the inductor Lpre and the capacitor C12 form a Buck circuit so that the bidirectional DC-DC conversion circuit 3 works in a voltage reduction mode; the controller 4 is used for controlling the switch tube QsafeNormally open, the capacitor C12, the inductor Lf, the switching tube Qh, the switching tube Ql and the high-voltage bus capacitor C48 are controlled to form a Boost circuit, so that the bidirectional DC-DC conversion circuit 3 works in a Boost mode.
In this embodiment, the freewheel element Dpre is a diode. In other implementations, the freewheeling element Dpre may also be a MOS transistor.
In this embodiment, the new energy vehicle is a hybrid vehicle, the charging power supply is a rechargeable battery, the output voltage of the charging power supply is 12V, the high-voltage power supply is a high-voltage battery, the output voltage of the high-voltage power supply is 48V, and the high-voltage bus capacitor C48 is a 48V bus capacitor. Since the low voltage side will typically be provided with an EMI differential mode filter inductance, the inductance Lpre can multiplex the EMI differential mode filter inductance. If the low voltage side is not provided with an EMI differential mode filter inductor, an additional inductor Lpre is needed.
Optionally, the switch tube Qh, the switch tube Ql and the switch tube Q are as described abovesafeThe NMOS transistors are all NMOS transistors, the grid electrode of each NMOS transistor is a control end, the drain electrode of each NMOS transistor is a first conduction end, and the source electrode of each NMOS transistor is a second conduction end. The diode Dh and the capacitor Ch are respectively a body diode and a parasitic capacitor of the switching tube Qh, and the diode Dl and the capacitor Cl are respectively a body diode and a parasitic capacitor of the switching tube Ql. In this embodiment, a high voltage power supply V is connected in parallel with a high voltage bus capacitor C4848_batAnd a pre-charge contactor 95 is connected in series between the positive pole of the high voltage bus capacitor C48.
In this embodiment, the bidirectional DC-DC conversion circuit 3 pre-charges the high-voltage bus capacitor C48 in two stages, the first stage is a step-down mode stage, and the charging source V is connected to the first stage12V_batThe output voltage of the high-voltage bus capacitor C48 is charged to a predetermined threshold value close to the charging power supply V through a Buck circuit12_batThe output voltage of (1); the second stage is a Boost mode stage, and the high-voltage bus capacitor C48 is continuously charged in a current mode or a voltage mode through a conventional Boost circuit until the voltage is charged to a final target voltage (close to the high-voltage power supply V)48_batThe output voltage of).
In the first phase, as shown in FIG. 4, the capacitor Cslow, the switch QsafeThe free-wheeling element Dpre, the inductor Lpre and the capacitor C12 constitute a first-stage pre-charge Buck circuit (see the dashed-line box region in fig. 4). At this stage, the operation sequence of the switching tube is as shown in fig. 5, the switching tube Qh and the switching tube Ql are always in the off state, and the high-voltage bus capacitor C48 is charged by controlling the duty ratio of the switching tube Qsafe. Switch tube QsafeThe duty ratio of (C) is gradually increased from 0% to 100%, according to the Buck circuit principle, a slowly rising voltage with a value equal to the voltage of the capacitor Csafe multiplied by the duty ratio is obtained at the capacitor C12, meanwhile, the capacitor C12 charges the high-voltage bus capacitor C48 through the inductor Lf and the body diode Dh of the switching tube Qh, the high-voltage bus capacitor C48 also obtains the same slowly rising voltage, and the charging path is as shown by the dashed line in fig. 4The arrows indicate, thereby eliminating the impinging flow problem. When the voltage V of the high-voltage bus capacitor C48C48Charge to a predetermined threshold (in this embodiment, the charging power supply V)12_batOutput voltage of) high voltage supply V48_batThe base voltage necessary for the boost topology has been obtained. The first stage can adopt open-loop control or closed-loop control, and the method is to adopt a voltage signal on the high-voltage bus capacitor C48 to carry out voltage mode control or adopt average current on the high-voltage side as a feedback signal to carry out current mode control. Finally, when the voltage on the high voltage bus capacitor C48 reaches a predetermined threshold, a switch is made to the second phase of pre-charging.
In the second stage, as shown in fig. 6, the control capacitor C12, the inductor Lf, the switching tube Qh, the switching tube Ql, and the high-voltage bus capacitor C48 form a Boost circuit (see the dashed-line box area in fig. 6). At this stage, the operation sequence of the switch tube is shown in FIG. 7, and the switch tube QsafeAlways in a normal on state, according to the principle of a Boost circuit, the duty ratio of the switching tube Ql is gradually increased from 0 percent to (V)48V_bat-V12V_bat)/V48V_batThe voltage of the high-voltage bus capacitor is smoothly increased, and large voltage and current overshoot is avoided; the complementary output of the switch tube Qh and the switch tube Ql is the charging path as shown by the dotted arrow in fig. 6 until the voltage V of the high-voltage bus capacitor C48C48Is charged to the final target voltage (in this embodiment, the high-voltage power supply V)48_batOutput voltage of) is detected. A dead time is set between the driving edges of the switch tube Ql and the switch tube Qh to prevent direct connection. The second stage may use the voltage signal on the high voltage bus capacitor C48 for voltage mode control or the current on the inductor Lf as a feedback signal for current mode control.
The pre-charging device for the high-voltage bus capacitor of the new energy automobile can also work in a forward Buck (Buck) mode and a reverse Boost (Boost) mode.
In the forward voltage reduction mode, the high-voltage power supply V is connected with the power supply voltage source V through controlling the switch tube Qh48_batThe output direct current is chopped into PWM voltage, and the PWM voltage is filtered by follow current of a switching tube Ql, an inductor Lf and a capacitor C12,a dc current with a lower voltage (e.g., 12V) is obtained at the low voltage side.
In reverse boost mode, the charging source V12V_batAnd auxiliary power supply is carried out to the high-voltage side. The inductor Lf, the switch tube Ql and the switch tube Qh form a Boost circuit to charge the low-voltage side of the power supply V12_batThe output voltage of (2) is boosted. Low-voltage side charging source V12_batThe inductor Lf is stored with energy through the switch tube Ql to generate voltage, and the charging power supply V is charged through the switch tube Qh12_batThe output voltage and the voltage of the inductor Lf are sent to the high-voltage side, filtering is carried out through a high-voltage bus capacitor C48, and the high-voltage side obtains direct current with higher voltage.
If the pre-charging contactor between the high-voltage power supply (e.g. 48V battery) and the high-voltage electrical appliance (e.g. 48V high-voltage electrical appliance) is directly pulled in, a large inrush current is generated because the high-voltage side capacitance is usually over 10mF, so that the low-voltage side charging power supply (e.g. 12V battery) is required to pre-charge the capacitor of the high-voltage electrical appliance first. While the low-voltage side is directly closed if the switch tube Q is closedsafeSimilarly, even if the low-voltage side charging power supply and the high-voltage bus capacitor are close to being directly connected in parallel, a very large inrush current may be caused, which may cause the switching tube Q to be turned on or offsafeAnd failure of the switching tube Qh and other potential failures. According to the invention, through the idea of topology conversion, the low-voltage side charging power supply and the high-voltage bus capacitor are not directly connected in parallel, but are multiplexed through the multiplexing switch tube QsafeA group of inductor Lpre and a follow current element Dpre are added, a Buck sub-circuit is generated in the first stage of pre-charging, a capacitor C12 and a high-voltage bus capacitor C48 are gradually charged to a basic voltage (for example, 12V) from 0V by utilizing the characteristic that the impact current is very small when the Buck circuit is in soft starting, the current impact is solved, the high-voltage bus capacitor C48 is further charged through a Boost circuit in the second stage of pre-charging, and the overall pre-charging function is realized. Compared with the prior art, the circuit structure of the pre-charging device saves the pre-charging resistor, is environment-friendly and energy-saving, and reduces the cost.
Claims (10)
1. Pre-charging of high-voltage bus capacitor of new energy automobileThe new energy automobile is provided with a direct current bus and a charging power supply, one end of the high-voltage bus capacitor is connected with the positive electrode of the direct current bus of the new energy automobile, and the other end of the high-voltage bus capacitor is connected with the negative electrode of the direct current bus of the new energy automobile; the pre-charging device comprises a bidirectional DC-DC conversion circuit, a capacitor voltage sampling circuit and a controller; the bidirectional DC-DC conversion circuit is coupled between the high-voltage bus capacitor and the charging power supply, so that the charging power supply can charge the high-voltage bus capacitor through the bidirectional DC-DC conversion circuit; the output end of the capacitor voltage sampling circuit is coupled with the input end of the controller, and the capacitor voltage sampling circuit is used for collecting the voltage of the high-voltage bus capacitor; the bidirectional DC-DC conversion circuit is characterized by comprising a Buck-Boost circuit, an inductor Lpre, a follow current element Dpre and a switching tube QsafeAnd a capacitance Cfafe;
a first input/output end of the Buck-Boost circuit is connected with the high-voltage bus capacitor in parallel, and a positive electrode of a second input/output end of the Buck-Boost circuit is connected with one end of an inductor Lpre; the other end of the inductor Lpre and the switching tube QsafeThe second conducting end of the first conducting terminal is connected; switch tube QsafeThe first conducting end of the first conducting terminal is connected with the positive electrode of the charging power supply; the negative end of the follow current element Dpre is connected with the other end of the inductor Lpre and the switching tube QsafeAnd one end of the capacitor Csafe is connected to the switching tube QsafeThe first conducting end of the first conducting terminal is connected with the common contact point of the positive electrode of the charging power supply; the negative electrode of the second input/output end of the Buck-Boost circuit, the positive electrode end of the follow current element Dpre, the other end of the capacitor Cslow and the negative electrode of the charging power supply are respectively connected with the negative electrode of the direct current bus;
the controller is respectively connected with the control end of the Buck-Boost circuit and the switching tube QsafeThe control end of the controller is connected; the controller can control the bidirectional DC-DC conversion circuit to work in a pre-charging mode, the bidirectional DC-DC conversion circuit firstly charges the high-voltage bus capacitor in a voltage reduction mode in the pre-charging mode, and the bidirectional DC-DC conversion circuit charges the high-voltage bus capacitor in a voltage boosting mode after the voltage of the high-voltage bus capacitor reaches a preset threshold valueAnd until the voltage of the high-voltage bus capacitor reaches a preset charging voltage value.
2. The pre-charging device for the high-voltage bus capacitor of the new energy automobile according to claim 1, wherein the Buck-Boost circuit comprises a bridge arm, an inductor Lf and a capacitor C12;
the bridge arm comprises a switch tube Qh and a switch tube Ql, the switch tube Qh and the switch tube Ql are provided with body diodes, a first conduction end of the switch tube Qh is connected with one end of the high-voltage bus capacitor, a second conduction end of the switch tube Qh is connected with the first conduction end of the switch tube Ql, and the second conduction end of the switch tube Ql is connected with the other end of the high-voltage bus capacitor;
one end of the inductor Lf is connected to a common junction point of the second conduction end of the switching tube Qh and the first conduction end of the switching tube Ql, and the other end of the inductor Lf is connected to one end of the inductor Lpre; one end of the capacitor C12 is connected to a common junction point of the other end of the inductor Lf and one end of the inductor Lpre, and the other end of the capacitor C12 is connected to the negative electrode of the direct-current bus;
the controller is respectively connected with the control end of the switch tube Qh and the control end of the switch tube Ql, and is used for controlling the switch tube Qh and the switch tube Ql to be normally opened and controlling the capacitor Cslow and the switch tube QsafeThe follow current element Dpre, the inductor Lpre and the capacitor C12 form a Buck circuit, so that the bidirectional DC-DC conversion circuit works in the voltage reduction mode; the controller is used for controlling the switching tube QsafeAnd normally opening, and controlling a capacitor C12, an inductor Lf, a switching tube Qh, a switching tube Ql and a high-voltage bus capacitor to form a Boost circuit so as to enable the bidirectional DC-DC conversion circuit to work in the Boost mode.
3. The pre-charging device for the high-voltage electrical apparatus of the new energy automobile as claimed in claim 2, wherein the controller is configured to control a switch Q when the bidirectional DC-DC conversion circuit is in the step-down modesafeIs gradually increased.
4. The pre-charging device for the high-voltage electrical apparatus of the new energy automobile according to claim 2, wherein the controller is configured to control the duty ratio of the switching tube Ql to gradually increase when the bidirectional DC-DC conversion circuit is in the boost mode.
5. The pre-charging device for the high-voltage electrical apparatus of the new energy automobile according to claim 2, wherein the controller is configured to control the duty ratio of the switching tube Ql to gradually increase from 0 to (V) when the bidirectional DC-DC conversion circuit is in the boost mode48V_bat-V12V_bat)/V48V_batWherein V is12V_batIs the output voltage of the charging power supply, V48V_batIs the output voltage of a high-voltage power supply connected in parallel with the high-voltage bus capacitor.
6. The pre-charging device for the high-voltage electric appliance of the new energy automobile according to claim 5, wherein the new energy automobile is a hybrid automobile, the output voltage of the charging power supply is 12V, the output voltage of the high-voltage power supply is 48V, and the high-voltage bus capacitor is a 48V bus capacitor.
7. The pre-charging device for the high-voltage electrical apparatus of the new energy automobile according to claim 1, wherein the inductor Lpre is an EMI differential mode filter inductor.
8. The pre-charging device for the high-voltage electric appliance of the new energy automobile according to claim 2, wherein the switch tube Qh, the switch tube Ql and the switch tube Q are connected in seriessafeThe NMOS transistor is characterized in that the NMOS transistor is an NMOS transistor, a grid electrode of the NMOS transistor is a control end, a drain electrode of the NMOS transistor is a first conduction end, and a source electrode of the NMOS transistor is a second conduction end.
9. The pre-charging device for the high-voltage bus capacitor of the new energy automobile as claimed in claim 1, wherein the freewheeling element is a diode or a MOS transistor.
10. The pre-charging device for the high-voltage bus capacitor of the new energy automobile according to any one of claims 1 to 9, wherein a pre-charging contactor is connected in series between a positive electrode of a high-voltage power supply connected in parallel with the high-voltage bus capacitor and one end of the high-voltage bus capacitor.
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| CN202010238241.5A CN111251941B (en) | 2020-03-30 | 2020-03-30 | Pre-charging device of high-voltage bus capacitor of new energy automobile |
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| CN111251941B (en) | 2024-05-14 |
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