CN113615031A

CN113615031A - Vehicle pre-charging system

Info

Publication number: CN113615031A
Application number: CN202080022586.5A
Authority: CN
Inventors: 达斯·苏拉吉特; V·拉马林加姆; G·克里希纳莫汉; S·杰贝兹迪纳加
Original assignee: TVS Motor Co Ltd
Current assignee: TVS Motor Co Ltd
Priority date: 2019-03-26
Filing date: 2020-03-19
Publication date: 2021-11-05
Also published as: WO2020194341A1

Abstract

The present subject matter discloses a pre-charge system in a vehicle. The present subject matter particularly describes systems and methods for reducing the effects of inrush current due to the presence of a capacitor load (304) in a circuit. The controller uses a Pulse Width Modulation (PWM) signal (310) to control the duty cycle to limit peak current and prevent contactor damage that may result from sudden inrush currents.

Description

Vehicle pre-charging system

Technical Field

The present subject matter relates generally to a vehicle. More particularly, but not exclusively, the present subject matter relates to a system for a pre-charge system for a vehicle.

Background

Vehicles that use batteries as a source of energy for vehicle operation typically employ high voltage battery packs due to the high demands placed on the generation of sufficient tractive effort. The battery pack typically includes a main contactor to switch battery power to a load. The circuit includes capacitors that generate a large amount of inrush current when the contactor is closed. In order to overcome the surge current, the circuit is provided with a pre-charge circuit. The pre-charge circuit may include a combination of a resistor or inductor in series with the contactor, connected across the contactor, and a semiconductor device such as a unijunction diode.

Other pre-charging techniques may include increasing the firing angle of the semiconductor devices (e.g., thyristors) in the rectifier until the capacitor on the dc bus charges to a certain level or connecting a resistor with a contactor in parallel with the bypass resistor via the contactor after the dc capacitor charges. In another type of pre-charge circuit, a three-phase switch may be involved, which may be connected to the dc bus to pre-charge or disconnect the dc bus.

Drawings

Fig. 1 illustrates a left side view of an exemplary vehicle including the present subject matter.

Fig. 2 shows a block diagram depicting the basic components of the present subject matter.

Fig. 3 shows a circuit level diagram including the present subject matter.

Fig. 4 shows a flow chart of a system used in the present subject matter.

Detailed Description

Typically, during charging or discharging of the energy source of the electrical device, the maximum instantaneous input current brought about by the electrical device when switched on may be several times the normal full load current for a certain number of input waveform cycles at the first power on. This is commonly referred to as input rush current or inrush current and can occur for a short time due to the higher initial power loading of the capacitor. Therefore, many circuits require protection from such inrush currents. In case of frequent switching on or off of the electrical equipment, the possibility of inrush current increases, which is detrimental to the durability and safety of the system.

DC (direct current) bus capacitors are typically present with all high power supplies to provide ripple current. These dc bus capacitors will dissipate the high inrush current while closing the main relay contactor that connects the high power supply to the dc bus with the inverter circuit bridge. This surge current can cause high peaks in the contactor and power supply (typically a battery) which can damage or shorten the life of both systems. Furthermore, high inrush currents in the contactor can lead to permanent welding of the contactor material. Frequent high inrush current problems can cause the life of the battery to be shortened due to overcurrent strain on the battery cells. Therefore, to avoid these high inrush currents, a pre-charge circuit is typically used in parallel with the main contactor.

A typical pre-charge circuit may consist of a switch in series with a resistor connected in parallel with the main contactor. Before the main contactor is closed, the precharge switch is closed and current flows through the precharge switch and the resistor. It is expected that the precharge process will be completed in a short time so that other processes are completed in a timely manner without any loss or damage. The charging time depends on the RC (resistance-capacitance) time constant. The pre-charge resistor must be large enough to limit inrush current, which can result in undesirably long delays, and the dc bus capacitance must have a relatively large capacitance, which can result in high capacitive potential loss according to the formula 1/2CV 2. Furthermore, the presence of an additional load on the main dc bus affects the pre-charging by increasing the impedance.

Devices and methods using resistors and using techniques such as increasing the firing angle of semiconductor devices result in an increase in power consumption and heat dissipation. Techniques involving one or more circuit breakers to connect or disconnect the drive to the dc bus increase overall size. Accordingly, there is a need to provide an improved pre-charge system that is compact, cost-effective and efficient, overcoming all of the above-mentioned problems and others with the prior art.

The present subject matter provides a pre-charging system and method configured to automatically detect a dc bus voltage, compare the dc bus voltage to a battery voltage and prevent sudden inrush currents due to the presence of one or more capacitors, thereby preventing potential damage to contactor relay switches. Further, the present subject matter provides a controller to monitor charging of a capacitor coupled to an inverter circuit.

Another embodiment of the present subject matter controls the duty cycle via the controller by providing a Pulse Width Modulation (PWM) signal to limit the peak current from the battery and to control the charge rate.

Yet another embodiment of the present subject matter provides a precharge circuit having two MOSFET switches. One of the switches is a switching MOSFET which is fed with a PWM (pulse width modulated signal) (310) and the PWM (pulse width modulated signal) (310) is controlled by a controller. The other switch is a bypass MOSFET. The switching between the two switches is controlled by a controller.

Another embodiment of the present subject matter is to provide a relay contactor connected in parallel with a pre-charge circuit. The relay contactor starts operating when the dc bus voltage is equal to the battery voltage. The relay type contactor is provided with a relay switch which is turned on or off when a relay coil is respectively energized or de-energized by a battery. The relay is controlled by a relay control signal provided by the controller.

Another embodiment of the present subject matter is to provide automatic switching between the pre-charge circuit and the bypass circuit by the controller, and to control the relay switches from any potential damage that may be caused by inrush current.

Yet another embodiment of the present subject matter is to provide automatic detection of voltage of a dc bus. If the DC bus voltage is lower than the battery voltage, the pre-charge circuit is activated to allow the DC bus voltage to rise to the level of the battery voltage. In the case of a rapid ignition ON/OFF sequence, the dc bus voltage will be at a potential level above zero volts but below the battery voltage. Thus, after the precharge process is completed, precharge begins and the bypass switch closes. During the pre-charging process, the inverter circuit operating circuit is kept in a sleep state to prevent any damage to the circuits including the microprocessor due to the sudden inrush of current.

Another embodiment of the present subject matter provides a precharge circuit that completely eliminates the need for manually operated switches and high power consuming circuits that include passive devices such as resistors.

Yet another embodiment of the present subject matter is to provide a small size inductor that does not compromise the duty cycle, as the duty cycle is monitored and controlled by the controller.

These and other advantages of the present subject matter will be described in more detail in the following description in conjunction with embodiments of a two-wheel scooter (scooter) type hybrid vehicle and the accompanying drawings.

Fig. 1 illustrates a left side view of an exemplary motor vehicle (100) according to an embodiment of the present subject matter. The illustrated vehicle (100) has a frame member (105). In the present embodiment, the frame member (105) is of a step type, and includes a head pipe (105A) and a main frame (105B) extending rearward and downward from a front portion of the head pipe (105A). The main frame (105B) extends obliquely rearward to the rear of the vehicle (100).

The vehicle (100) includes one or more prime movers connected to the frame member (105). In the present embodiment, one of the prime movers is an Internal Combustion (IC) engine (115) mounted to the frame member (105). In the depicted embodiment, the IC engine (115) is mounted to a structural member (135) that pivots to a frame member (105). In one embodiment, the structural member (135) is a rigid member made of a material including metal. The vehicle (100) also includes another prime mover, namely an electric motor (120). In a preferred embodiment, the electric motor (120) is mounted to one wheel of the vehicle (100) via a hub. In another embodiment, one or more electric motors are mounted to a wheel or frame of the vehicle. In the depicted embodiment, the vehicle (100) includes at least two wheels, and the electric motor (120) is mounted to a rear wheel (125) of the vehicle through a wheel hub. The front wheel (110) is rotatably supported by the frame member (105) and is connected to a handle assembly (130) capable of maneuvering the vehicle (100).

Further, the vehicle (100) includes a high-capacity vehicle-mounted battery (not shown) that drives the electric motor (120). The high-capacity battery may include one or more high-capacity battery packs or one or more low-capacity battery cells. The high-capacity battery may be disposed at the front, rear, or center of the vehicle (100). The high-capacity battery is supported by a frame member (105), and the vehicle (100) includes a plurality of vehicle body panels mounted to the frame member (105) to cover various components of the vehicle (100). The plurality of panels includes a front panel (140A), a leg shield (140B), a seat lower cover (140C), and left and right side panels (140D). The glove box may be mounted to the leg shield (140B).

The bottom plate (145) is provided at a step portion defined by the main pipe (105B). A seat assembly (150) is disposed rearward of the stride portion, and is mounted to the main frame (105B). A seat assembly (150) elongated in a longitudinal direction F-R of the vehicle (100) enables a user to operate the vehicle in a riding posture. One or more suspensions connect the wheels (110), (125) to the vehicle (100) and provide a comfortable ride. The vehicle (100) includes a plurality of electrical and electronic components including a head lamp (155A), a tail lamp (155B), a starter motor (not shown), a horn, and the like. Further, the vehicle (100) includes a main control unit (not shown) that controls the overall operation of the vehicle (100), including the operation of the IC engine (115), the operation of the electric motor (120), the charging of the battery by the magneto/Integrated Starter Generator (ISG), the driving of the load by the magneto/ISG, the charging of the high capacity battery by the electric motor operating in the generator mode, and any other operation associated with the operation of the vehicle (100). The vehicle (100) shown in fig. 1 is an exemplary vehicle and the present subject matter may be used for a two-wheeled vehicle, a three-wheeled vehicle, or a four-wheeled vehicle.

Fig. 2 illustrates a block diagram of an embodiment of the present subject matter. The vehicle is required to start as soon as possible when the driver turns on the vehicle, so it is desirable to complete the pre-charging process in a short time. The electric drive of an electric or hybrid vehicle is provided with a DC (direct current) power source (201), for example a battery (201) of about 48 volts (which may be higher depending on vehicle requirements). The power from the battery (201) needs to be stepped down according to the requirements of the various inputs present in the vehicle. Further, the power source may be converted from direct current to alternating current, depending on the type of load. An inverter circuit (206) that converts the dc power to ac power at a particular frequency to drive traction motors and other applicable electrical loads at a particular speed is also configured to the contactor (202). The inverter circuit (206) is coupled with at least one capacitor load (304) (see fig. 3) to remove ripple carried by the power signal from the battery. Thus, the pre-charge circuit (300) that charges the capacitor load (304) when coupled with the inverter circuit (206) is referred to as pre-charging of the dc bus (305) (see fig. 3). When the dc bus (305) is only charging, the battery voltage will be applied to the load (207). When the dc bus potential drops below a certain level, the dc bus (305) may be recharged. After the precharge function is completed, the inverter circuit (206) starts to operate by turning off the precharge circuit (300) via the controller (205).

The battery (201) is connected to a contactor (202), and the contactor (202) is responsible for powering loads (207), such as traction motors and electrical loads (e.g., headlamps, tail lamps, turn signals, speedometers, several input switches and sensors). The contactor (202) has an input adapted for connection with a battery (201) and an output connected to a load (207). The contactor (202) is of the relay contactor type, which is energized and de-energized to switch between an open state and a closed state enabled by a relay switch (313) (see fig. 3). The power on and off is controlled by a controller (205). The dc bus (305) is coupled to the capacitor load (304) and the output of the relay-based contactor (202).

The pre-charge circuit is electrically configured in parallel between the battery (dc power supply) and the capacitor to prevent damage to the contactor (202) due to a few seconds of sudden current transients caused by inrush currents. The pre-charge circuit (300) provides a controlled current supply from the battery (201) to the capacitor load (304). The amount of current supplied to the load (207) is controlled by the controller (205).

The precharge circuit (300) includes a precharge switch (204) and a bypass switch (203). The switching between the bypass switch (203) and the precharge switch (204) is controlled by a controller (205). The controller (205) signals the contactor (202) to begin transferring power to the inverter circuit (206) to run the load (207) based on the dc bus voltage, and at the same time the pre-charge switch (204) is closed.

Fig. 3 shows an embodiment of a precharge circuit (300). The bypass switch (203) and the precharge switch (204) are active devices such as MOSFETs. The source of the precharge switch (204) is electrically connected to the positive terminal of the battery (201). Likewise, the source of the bypass switch (203), also referred to as the on/off of the control MOSFET switch, is connected to the positive terminal of the battery (201). The active solid state device MOSFET may be a depletion MOSFET or an enhancement MOSFET. The gate of the precharge switch (204) is connected to a controller (205) that provides a series of pulses. The pulses provided by the controller (205) to the gate of the precharge switch (204) are Pulse Width Modulated (PWM) signals (310). Similarly, the gate of the bypass switch (203) receives a control signal (309) from the controller (205). The on/off function of the precharge switch (204) can be controlled by the bypass switch (203). When the precharge circuit (300) matches the dc bus voltage to the battery voltage, the controller (205) turns off the precharge process and the controller turns on the bypass switch (203). The source of energy may be a battery or any other rectified ac power source. The capacitor load (304) and the inverter circuit (206) are both connected in parallel, and the dc bus is connected to the capacitor load (304) and the inverter circuit (206).

The drain of the precharge switch (204) is connected to the n-side of the unijunction diode (303) and the inductor (302). The drain of a bypass switch (203) that controls on/off control of the precharge switch (204) is electrically connected to the inverter circuit (206), at least one capacitor load (304), and the inductor (302). The diode (303) has been reverse biased with its positive terminal (p-side) connected to the negative terminal of the battery (201), and the p-side of the diode (303) connected to the drain of the precharge switch (204) and the inductor (302).

The circuit is also provided with a contactor (202), the contactor (202) being electrically configured in parallel with the pre-charge switch (204). The source of the bypass switch (203) and the source of the pre-charge switch (204) are electrically connected to the relay input (306) of the contactor (202). The contactor (202) includes a relay coil (314) having a terminal a, which controls the relay by first monitoring the pre-charge process and providing a relay control signal (312) from the controller (205) to control the function of the contactor (202) based on the dc bus voltage. The other input of the contactor (202) is a terminal B which is grounded at zero potential. The relay coil (314) is energized, and the relay coil (314) activates switching of the relay switch (313). When the relay switch (313) is closed or on, current flows from the contactor (202) to the load (207). The controller (205) sends a relay control signal (312) to energize and de-energize the relay coil (314), thereby controlling the flow of current through the relay switch (313) to the load (207). Thus, the relay-based contactor (202) operates based on a relay control input received from the controller (205).

FIG. 4 illustrates a method of implementing the described precharge system. To initiate the precharge process, the controller (205) enables the precharge switch (204) in step 401. In step 402, the voltage level of the dc bus is detected and the gate of the precharge switch (204) receives a Pulse Width Modulation (PWM) signal (310) and controls the current to the capacitor load (305) by controlling the duty cycle and limiting the peak current value. The precharge switch (204) provides a controlled small amount of constant current to increase the level of the dc bus voltage. The duty cycle and the switching frequency are appropriately selected based on at least one of the voltage and the rise time of the inductance. In step 403, the duty cycle is controlled based on the voltage rise of the dc bus capacitor load (304).

In step 404, the dc bus voltage is compared to the battery voltage in step 404. The method is repeated until the dc bus voltage reaches the battery voltage. When the voltage match is met, then the precharge switch is turned off (204) in step 405. The gate provided to the precharge switch (204) is used to vary the duty cycle to adjust the output peak current and control the charge rate pulse width modulated signal (310) to be controlled by the controller. Pulse Width Modulation (PWM) (310) provides a time delay to prevent any surge in current.

Further, the bypass switch (406) is activated in step 406, and the relay switch (313) closes the circuit by closing the relay input (306) and the relay output (307) in step 407. When the contactor (202) is closed and the capacitor load (304) is fully charged, then the inverter circuit (206) receives power.

To prevent damage, the precharge circuit (300) is configured to continuously monitor the duty cycle with a controller (205), the controller (205) using a pulse modulation (PWM) signal (310) provided to the MOSFET-based recharge circuit. Implementing resistors in the precharge circuit (300) adds undesirable delay and therefore, inductors are used to avoid delay. Incorporating large size inductors reduces delay time but overall material costs can rise and using smaller inductors can result in more delay but smaller duty cycles. Thus, to control the duty cycle by incorporating a smaller inductor, a pre-charge switch (204) is utilized and the controller (205) provides a PWM (pulse width modulation) signal (310). The PWM signal helps to speed up the switching frequency of the precharge switch (204) and at the same time controls the duty cycle to limit the peak current.

The controlled current continues to flow to the pre-charge circuit until the voltage across the dc bus equals the battery voltage. When the dc bus reaches a voltage equal to the battery (201) voltage, the bypass switch (203) is turned on and the precharge switch (204) is turned off.

Claims

1. A precharge system, comprising:

a power supply (201); one or more DC buses (305), the one or more DC buses (305) connected to one or more inverter circuits (206), the inverter circuits (206) electrically configured to one or more loads (207); a pre-charge circuit (300) is electrically configured to the capacitor load (304), the pre-charge circuit (300) comprising one or more switches (203, 204) controlled by a controller (205), a contactor (202) electrically controlled by the controller (205) supplying power to the inverter circuit (206), the inverter circuit (206) supplying power to one or more loads (207); and

the one or more switches (203, 204) are operated by the controller (205) via a pulse width modulated signal (310) to control one or more duty cycles to regulate charging of the capacitor load (304).

2. The pre-charging system of claim 1, wherein the contactor (202) is a relay contactor provided with a relay control signal (312) for powering on and off.

3. The pre-charging system of claim 1, wherein the one or more switches are a bypass switch (203) and a pre-charge switch (204).

4. The pre-charging system according to claim 1, wherein the pre-charging circuit (300) controls to turn off the pre-charging switch (204) when the voltage reaches a voltage equal to that of the power supply (201).

5. A pre-charging system according to claim 3, wherein the pre-charging switch (204) is provided with a Pulse Width Modulation (PWM) signal (310) to control the one or more duty cycles to limit the peak current from the power supply (201).

6. A method for pre-charging a capacitor load (304), comprising the steps of:

enabling a pre-charge switch (204);

detecting a rise and a duty ratio of the voltage;

checking a direct current bus voltage and comparing the direct current bus voltage with a power supply voltage;

closing the pre-charge switch (204);

turning on a bypass switch (203); and

closing a contactor (202) to transfer power to an inverter circuit (206);

7. the method for pre-charging a capacitor load (304) according to claim 6, wherein the pre-charging operation is turned off when a DC bus voltage becomes equal to the supply voltage.

8. The method for pre-charging a capacitor load (304) according to claim 6, wherein a pre-charge operation is initiated when the DC bus voltage is not equal to a battery voltage.

9. The method for pre-charging a capacitor load (304) according to claim 6, wherein the duty cycle is controlled by the controller (205) by a Pulse Width Modulation (PWM) signal (310).

10. The method for pre-charging a capacitor load (304) according to claim 6, wherein the DC (direct current) power source (201) is a battery (201).