Vehicle-mounted charging system and associated control procedure

Abstract

The present invention provides a vehicle-mounted charging system and a control method therefor. The vehicle-mounted charging system comprises: a converter that can be coupled on the one hand to an external AC power source outside a vehicle and on the other hand to a traction battery of the vehicle; an inverter that is coupled between the traction battery and an electric motor of the vehicle and comprises several bridge branches and a DC capacitor, wherein each of the bridge branches comprises an upper bridge branch switch and a lower bridge branch switch, and wherein a positive and a negative busbar are bridged by the DC capacitor;a group of on / off switches comprising a first on / off switch and a second on / off switch, wherein the first on / off switch is located in the positive busbar and the second on / off switch is connected to the intermediate node between the upper bridge branch switch and the lower bridge branch switch of one of the multiple bridge branches; and a controller configured to control the operation of the vehicle-mounted charging system by controlling the on / off switches and the combined states of the upper and lower bridge branch switches of another bridge branch or of two other bridge branches of the multiple bridge branches that are not connected to the second on / off switch.

Description

Technical field

[0001] The invention belongs to the field of vehicle-mounted charging technologies. In particular, the present invention relates to a vehicle-mounted charging system and a control method for it. State of the art

[0002] Hybrid electric vehicles (HEVs) and electric vehicles (EVs) are two main types of new energy vehicles, both equipped with a vehicle-mounted charging system. Such a system converts grid-side alternating current at the grid frequency into direct current to charge a vehicle's traction battery (i.e., a vehicle-mounted traction battery).

[0003] In the prior art, the vehicle-mounted charging system typically comprises a two-stage topology, consisting primarily of two converter stages: an AC-DC converter stage and a DC-DC converter stage. High-capacitance busbar capacitors are connected in parallel between these two stages. This is because the input side of the AC-DC converter stage receives a sinusoidal alternating current and voltage, resulting in a ripple at twice the mains frequency in the input signal. Since the frequency of the alternating current is low at the mains frequency (e.g., 50 Hz), the high-capacitance busbar capacitors between the AC-DC and DC-DC converter stages are necessary to eliminate this ripple.

[0004] However, such a high-capacity busbar capacitor has a high capacitance value, is relatively expensive, and thus increases manufacturing costs. Furthermore, the volume of a high-capacity busbar capacitor is relatively large, which increases the space required for the vehicle-mounted system. In practical applications, an electrolytic capacitor is usually chosen as the busbar capacitor to meet the high capacitance requirement, since an electrolytic capacitor typically has a higher capacitance than a film capacitor for the same volume. However, electrolytic capacitors have the problem of a short lifespan. Disclosure of the invention

[0005] Against this background, the embodiments of the present invention propose an improved vehicle-mounted charging system which can use a converter without a busbar capacitor and can control the operation of the vehicle-mounted charging system by controlling the combined state of several switches of the vehicle-mounted charging system.

[0006] According to an embodiment of one aspect of the present invention, a vehicle-mounted charging system is provided, comprising: a converter which is coupled on the one hand to an external AC power source outside a vehicle and on the other hand to a traction battery of the vehicle; an inverter which is coupled between the traction battery and an electric motor of the vehicle and which comprises several bridge branches and a DC capacitor, wherein each of the bridge branches comprises an upper bridge branch switch which is coupled to a positive busbar and a lower bridge branch switch which is coupled to a negative busbar, and wherein the positive and the negative busbar are bridged by the DC capacitor;a group of on / off switches coupled between the inverter and the vehicle's traction battery, the group of on / off switches comprising a first on / off switch and a second on / off switch, the first on / off switch being located in the positive busbar and the second on / off switch being connected to the intermediate node between the upper bridge branch switch and the lower bridge branch switch of one of the multiple bridge branches; and a controller configured to control the operation of the vehicle-mounted charging system by controlling the on / off switches and the combined states of the upper and lower bridge branch switches of another bridge branch or of two other bridge branches of the multiple bridge branches that are not connected to the second on / off switch.

[0007] According to an embodiment of another aspect of the present invention, a method for controlling a vehicle-mounted charging system is provided. The vehicle-mounted charging system comprises: a converter that can be coupled on the one hand to an external AC power source outside a vehicle and on the other hand to a traction battery of the vehicle; an inverter that is coupled between the traction battery and an electric motor of the vehicle and comprises several bridge branches and a DC capacitor, wherein each of the bridge branches comprises an upper bridge branch switch that is coupled to a positive busbar and a lower bridge branch switch that is coupled to a negative busbar, and wherein the positive and the negative busbars are bridged by the DC capacitor;A group of on / off switches coupled between the inverter and the vehicle's traction battery, the group of on / off switches comprising a first on / off switch and a second on / off switch, the first on / off switch being located in the positive busbar and the second on / off switch being connected to the intermediate node between the upper bridge branch switch and the lower bridge branch switch of one of the multiple bridge branches. The method comprises: controlling the operation of the vehicle-mounted charging system by controlling the on / off switches and the combined states of the upper and lower bridge branch switches of another bridge branch or of two other bridge branches of the multiple bridge branches that are not connected to the second on / off switch.

[0008] So far, an overview of the important aspects of the present invention has been given to establish a basic understanding of these aspects. This overview is by no means intended to limit the scope of any or all aspects of the present invention. Its purpose is to briefly describe some possible realizations of these aspects, thereby providing an introduction for the subsequent more detailed explanation. Brief description of the characters

[0009] The following detailed description, in conjunction with the accompanying drawings, clarifies the technical solution of the present invention. It is understood that the drawings serve solely as an example and do not limit the scope of protection of the present invention. They show: Fig. 1A an application scenario of a vehicle-mounted charging system according to an embodiment of the present invention, Fig. 1B another application scenario of the vehicle-mounted charging system according to an embodiment of the present invention, Fig. 2A an example circuit of the vehicle-mounted charging system according to an embodiment of the present invention, which in the application scenario according to Fig. is connected to 1A, Fig. 2B an example circuit of the vehicle-mounted charging system according to an embodiment of the present invention, which in the application scenario according to Fig. 1B is connected, Fig. 3 a flowchart of a method for controlling a vehicle-mounted charging system according to an embodiment of the present invention. Fig. 4 a flowchart of a method for controlling a vehicle-mounted charging system according to a further embodiment of the present invention. Fig. 5 a flowchart of a method for controlling a vehicle-mounted charging system according to a further embodiment of the present invention. Detailed descriptions

[0010] Exemplary embodiments of the present invention relate to a vehicle-mounted charging system and an associated control method. In this vehicle-mounted charging system, a converter is designed as a two-stage converter without a busbar capacitor. According to one exemplary embodiment of the present invention, the storage / release of reactive power energy in a DC capacitor is achieved by controlling the combined state of several switches of the vehicle-mounted charging system, thereby improving the power quality and increasing system stability and reliability. This eliminates the need for a busbar capacitor between the two converter stages of the converter.

[0011] According to one embodiment of the present invention, the vehicle-mounted charging system can operate in a mode selectable from AC charging mode, traction mode, and vehicle-to-load mode of the traction battery. According to one embodiment of the present invention, several switches of the vehicle-mounted charging system and the DC capacitor form a bidirectional boost / boost converter. By controlling this bidirectional boost / boost converter, the vehicle-mounted traction battery can be charged by an external AC power source, regardless of whether the instantaneous power supplied by the external AC power source is greater or less than the required charging power of the vehicle-mounted traction battery.

[0012] Furthermore, according to an embodiment of the present invention, the storage / release of reactive power energy in a DC capacitor can be realized in both the AC charging mode and the vehicle-to-load mode of the traction battery, thereby achieving reactive power compensation.

[0013] Detailed embodiments of the present invention are described below with reference to the accompanying drawings.

[0014] Fig. Figure 1A shows a vehicle-mounted charging system 100 (hereinafter sometimes referred to simply as "System 100") according to an embodiment of the present invention, which is connected to an external AC power source 200 outside the vehicle. In this case, System 100 can operate in AC charging mode.

[0015] In AC charging mode, the vehicle V does not move and an inverter of the vehicle-mounted charging system 100 does not need to perform DC-AC conversion. In this mode, a traction battery 110 of the vehicle V receives electrical power from the external AC power source 200 (e.g., an AC charging station).

[0016] According to an embodiment of the present invention, in AC charging mode, even if the instantaneous power output of the external AC power source 200 is not equal to the current charging power required by the traction battery 110 (the current charging power required by the traction battery 110 can be output by a battery management system BMS), for example, if the instantaneous power output of the external AC power source 200 is greater or less than the current charging power required by the traction battery 110, it can still be achieved by controlling the vehicle-mounted charging system 100 that the external AC power source is suitable for charging the traction battery 110.

[0017] Fig. Figure 1B shows the vehicle-mounted charging system 100 according to an embodiment of the present invention, which is connected to a load outside the vehicle (e.g., a high-power electrical appliance such as a kettle or an induction cooktop). In this case, the system 100 can operate in the vehicle-to-load mode of the traction battery.

[0018] In the vehicle-to-load mode of the traction battery, the vehicle is not moving and the inverter of the vehicle-mounted charging system 100 does not need to perform DC-AC conversion. In this mode, the electrical energy stored in the traction battery 110 is supplied to the load.

[0019] Furthermore, in the vehicle-to-load mode of the traction battery, the electrical energy stored in the traction battery 110 can also be supplied to the power grid. For example, during peak load times throughout the day, the electrical energy stored in the vehicle-mounted traction battery 110 is fed back into the power grid (vehicle-to-load mode of the traction battery). During off-peak times throughout the day, electrical energy from the power grid is used to charge the vehicle-mounted traction battery 110 (AC charging mode).

[0020] The vehicle-mounted charging system 100 according to an embodiment of the present invention can also operate in traction mode. In traction mode, the vehicle is moving and the inverter performs a DC-AC conversion to convert the direct current from the traction battery 110 into alternating current and supply it to an electric motor 120, thus powering the vehicle.

[0021] Fig. Figure 2A shows an example circuit of the vehicle-mounted charging system 100. As can be seen from Fig. 2A results in the system 100 primarily comprising: a converter 10, an inverter 20, a group of on / off switches 30 and a control unit 40.

[0022] The converter 10 is designed as a two-stage converter without a busbar capacitor and serves to transfer electrical energy from the external AC power source 200 to the traction battery 110 on the vehicle. Specifically, the converter 10 comprises, with reference to Fig. 2A an AC / DC converter 11 and an isolated DC / DC converter 12, wherein there is no busbar capacitor between the AC / DC converter 11 and the isolated DC / DC converter 12 by which a positive and a negative busbar are bridged.

[0023] The inverter 20, which can also be called a traction inverter, is connected between the traction battery 110 and the electric motor 120 of the vehicle. The inverter 20 is able to convert direct current from the traction battery 110 into alternating current and supply this alternating current to the electric motor 120 to power the vehicle. As shown in Fig. As shown in Figure 2, the electric motor 120 is a three-phase motor comprising three phase windings, and the inverter 20 comprises three bridge branches: a first bridge branch 20A, a second bridge branch 20B, and a third bridge branch 20C. Each bridge branch includes an upper bridge branch switch connected to the positive busbar and a lower bridge branch switch connected to the negative busbar. An intermediate node between the upper bridge branch switch and the lower bridge branch switch of each bridge branch is connected to a corresponding phase winding of the electric motor 120.For example, the intermediate node NA of the upper bridge branch switch Q1 and the lower bridge branch switch Q2 of the first bridge branch 120A is coupled to a motor winding 120A; the intermediate node NB of the upper bridge branch switch Q3 and the lower bridge branch switch Q4 of the second bridge branch 120B is coupled to a motor winding 120B; and the intermediate node NC of the upper bridge branch switch Q5 and the lower bridge branch switch Q6 of the third bridge branch 120C is coupled to a motor winding 120C. The motor windings 120A-120C are, respectively, the A-phase winding, the B-phase winding, and the C-phase winding of the electric motor 120.

[0024] Each of the switches Q1 to Q6 can be implemented as a controllable power semiconductor device. In one embodiment, each switch can be implemented as a metal-oxide-semiconductor field-effect transistor (MOSFET). This transistor includes a parasitic diode with a freewheeling function. In another embodiment, each switch can be implemented as an insulated-gate bipolar transistor (IGBT) and a diode, wherein the cathode of the diode is connected to the collector of the transistor and the anode is connected to the emitter of the transistor. The insulated-gate bipolar transistor (IGBT) is a controllable switching device. The diode is an uncontrollable switching device and can implement the freewheeling function.

[0025] The inverter 20 further includes a direct current (DC) capacitor C1, which serves to store the reactive power component (e.g., the ripple component with twice the frequency in the output of the converter 10) of the energy output by the converter 10 or to release the stored energy to perform reactive power compensation for the output of the converter 10. As shown in Fig. As shown in Figure 2, the positive and negative busbars are bridged by the DC capacitor C1. Specifically, one terminal of the DC capacitor C1 is connected to a switch terminal of the upper bridge branch switch of the single bridge branch of the inverter 20 that is connected to the positive busbar, while the other terminal of the DC capacitor C1 is connected to a switch terminal of the lower bridge branch switch of the single bridge branch of the inverter 20 that is connected to the negative busbar.

[0026] The group of on / off switches 30 is connected between the vehicle's traction battery 110 and the inverter 20 and comprises a first on / off switch 31 and a second on / off switch 32. The first on / off switch 31 and the second on / off switch 32 can each be electronic switches (e.g., relays) and have two states: on (ON) and off (OFF). Both the on / off switch 31 and the on / off switch 32 can be set to an on or off state by the controller 40.

[0027] The on / off switch 31 is located on the positive busbar. The switch branch 32 is connected to one of the several bridge branches, e.g., the first bridge branch 20A. Specifically, one switch terminal of the first on / off switch 31 is connected to the switch terminal of the upper bridge branch switch Q1 of the first bridge branch 20A that is connected to the positive busbar, the other switch terminal of the first on / off switch is connected to a switch terminal of the second on / off switch 32, and the other switch terminal of the second on / off switch 32 is connected to the intermediate node between the upper bridge branch switch Q1 and the lower bridge branch switch Q2 of the first bridge branch 20A.

[0028] It is understood that, according to one embodiment of the present invention, the second on / off switch 32 can be connected to the intermediate node of the upper and lower bridge branch switches of any one of the three bridge branches. Fig. 2A and in the above description, it is shown by way of example that the second on / off switch 32 is connected to the intermediate node of the upper and lower bridge branch switches of the first bridge branch 20A. In some further embodiments, the second on / off switch 32 can be connected to the intermediate node of the upper and lower bridge branch switches of the second bridge branch 20B or the third bridge branch 20C.

[0029] According to one embodiment of the present invention, the DC capacitor C1, one or two other bridge branches of the multiple bridge branches that are not connected to the second on / off switch 32, and at least a portion of the multiple motor windings form a bidirectional boost / drag converter. This bidirectional boost / drag converter can be operated in either forward boost mode or reverse buck mode, thus accommodating the AC load under various scenarios.

[0030] According to one embodiment of the present invention, the system 100 can further comprise an electromagnetic interference (EMI) filter 50. The EMI filter bridges the positive and negative busbars and is coupled to the input side of the converter 10 to eliminate or reduce electromagnetic interference from the external AC power source 200 (e.g., the mains power supply), thereby improving the performance of the system 100 and ensuring that the system 100 meets the relevant electromagnetic compatibility (EMC) standards.

[0031] According to one embodiment of the present invention, the system 100 can further comprise a capacitor Co. The positive and negative busbars are bridged by the capacitor Co, and the capacitor is coupled to the output side of the converter 10. This capacitor Co can also be referred to as an output capacitor and serves to stabilize the output voltage and for filtering.

[0032] The controller 40 controls the operation of the vehicle-mounted charging system 100 by controlling the on / off switches and the combined states of the upper and lower bridge branch switches of at least one of the further bridge branches of the multiple bridge branches that are not connected to the second on / off switch 32. According to an embodiment of the present invention, the combined state comprises: the on / off state of each on / off switch, the on / off state of a switch from the upper and lower bridge branch switches of at least one bridge branch, and the duty cycle of the other switch.

[0033] The following are some exemplary embodiments of the control scheme, using the example in which the control unit 40 controls the respective on / off switches as well as the upper and lower bridge branch switches of the second bridge branch 20B.

[0034] In one embodiment, the controller 40 controls the on / off state of the respective on / off switches as well as the combined state of the upper and lower bridge branch switches of the second bridge branch 20B in order to operate the vehicle-mounted charging system 100 in AC charging mode, in which the electrical energy is transferred from the external AC power source 200 to the traction battery 110.

[0035] In AC charging mode, the bidirectional boost / drag converter can operate in either forward boost mode or reverse boost mode. The instantaneous power output (i.e., the instantaneous charging power) from the converter is compared to the current charging power requirement of the traction battery to obtain a comparison result. Based on this comparison, it is determined whether the bidirectional boost / drag converter operates in forward boost mode or reverse boost mode; in other words, the current operating mode of the bidirectional boost / drag converter is determined.

[0036] If the instantaneous power output by the converter is greater than the current charging power required by the traction battery, the controller 40 controls the bidirectional boost / step-down converter in such a way that it operates in forward boost mode in order to store a reactive power component of the energy output by the converter in the DC capacitor and to transfer electrical energy from the external AC power source 200 to the traction battery 110: 1) Controlling the first on / off switch 31 so that it is switched off; 2) Controlling the second on / off switch 32 so that it is switched on; 3) Applying a PWM signal to the lower bridge branch switch Q4 of the second bridge branch 20B, and either not applying a drive signal or applying a drive signal complementary to the PWM signal of switch Q4 to the upper bridge branch switch Q3 of the second bridge branch 20B.

[0037] If the instantaneous power output by the converter is less than the current charging power required by the traction battery, the controller 40 controls the bidirectional boost / step-down converter to operate in reverse buck mode in order to release the energy stored in the DC capacitor, thus performing reactive power compensation for the converter output and transferring electrical energy from the external AC power source 200 to the traction battery 110: 1) Controlling the first on / off switch 31 to switch it off; 2) Controlling the second on / off switch 32 to switch it on; 3) Applying a PWM signal to the upper bridge branch switch Q3 of the second bridge branch 20B, and neither applying a drive signal nor applying a drive signal complementary to the PWM signal of switch Q3 to the lower bridge branch switch Q4 of the second bridge branch 20B.

[0038] In one embodiment of the present invention, the “complementary” drive signal denotes a drive signal with opposite phase. For example, a PWM signal is applied to one switch and a PWM signal complementary to this PWM signal is applied to another switch, whereby these two switches are not switched on and off simultaneously, but are always in a state in which one is switched on and the other is switched off.

[0039] Fig. Figure 2B shows the situation in which the vehicle-mounted charging system 100 operates in the vehicle-to-load mode of the traction battery. In this mode, the control scheme, which is implemented by controlling the bidirectional boost / drag converter to store the reactive power component of the output energy of converter 10 in the DC capacitor or to release the stored energy and thus perform reactive power compensation for the output of converter 10, is identical to the control scheme described above in AC charging mode. Therefore, the above explanations regarding the control scheme in AC charging mode are equally applicable here. The difference between the vehicle-to-load mode of the traction battery and the AC charging mode is as follows: In the vehicle-to-load mode of the traction battery, the electrical energy flows from the traction battery 110 to the load 300 or the external AC power source (e.g., a car).the power grid); while in AC charging mode the electrical energy flows from the external AC power source into the vehicle-mounted traction battery 110.

[0040] Furthermore, the control unit 60 causes the operation of the vehicle-mounted charging system 100 in traction mode by means of the following control measures: 1) controlling the first on / off switch 31 so that it is switched on; 2) controlling the second on / off switch 32 so that it is switched off; and 3) controlling the on / off state of the respective bridge branch switches of the inverter 20 according to a predetermined switching sequence, so that the inverter 20 is able to convert direct current from the traction battery 110 into alternating current and to supply this alternating current to the electric motor 120 to drive the vehicle.

[0041] Fig. Figure 3 shows a method 400 for controlling a vehicle-mounted charging system according to an embodiment of the present invention. The method 400 can be implemented by controlling the system 100 by means of the control unit 40 described above.

[0042] Method 400 comprises the following: The controller 40 controls (block 410) the operation of the vehicle-mounted charging system by controlling the on / off switches and the combination states of the upper and lower bridge branch switches of another bridge branch of the several bridge branches that are not connected to the second on / off switch 32 (e.g., one of the two bridge arms 20B and 20C that are not connected to the second on / off switch).

[0043] The following section explains the sub-steps contained in block 410. In block 411, the controller 40 detects the position of the q-axis of the rotor of the vehicle electric motor.

[0044] It should be understood that the position of the q-axis of the rotor of the electric motor can be obtained in various ways, for example by direct position measurement, induction methods, calculations based on observers, etc. The present invention does not impose any restrictions regarding the manner in which the position of the q-axis of the rotor of the electric motor is obtained.

[0045] In block 412, the control 40 selects one further bridge branch from the several bridge branches (i.e., one of the two further bridge branches that are not connected to the second on / off switch 32) so that the equivalent magnetic flux generated by the stator coil is directed as far as possible in the direction of the position of the q-axis of the rotor.

[0046] It is therefore obvious that the selection of the other bridge branch depends on the engine's braking position when the vehicle is stationary. By selecting the other bridge branch for reuse in this way, efficiency can be increased and losses reduced.

[0047] In block 413, the control unit 40 compares the current power output by the converter with the current charging power required by the traction battery.

[0048] If the comparison result shows that the instantaneous power output by the converter is greater than the current charging power required by the traction battery, procedure 400 in block 414 is initiated.

[0049] In block 414, the controller 40 controls the bidirectional boost / step-down converter such that it operates in forward boost mode in order to store a reactive power component of the energy output by the converter in the DC capacitor and to transfer electrical energy from the external AC power source to the traction battery: 1) controlling the first on / off switch so that it is switched off; 2) controlling the second on / off switch so that it is switched on; and 3) applying a PWM signal to the lower bridge branch switch of the further bridge branch, and applying no drive signal or a drive signal complementary to the PWM signal (i.e., the PWM signal applied to the lower bridge branch switch of the further bridge branch) to the upper bridge branch switch of the further bridge branch.

[0050] If the comparison result shows that the instantaneous power output by the converter is less than the current charging power required by the traction battery, procedure 400 in block 415 is initiated.

[0051] In block 415, the controller 40 controls the bidirectional boost / drag converter such that it operates in reverse buck mode to release the energy stored in the DC capacitor, thus performing reactive power compensation for the converter output and transferring electrical energy from the external AC power source to the traction battery: 1) controlling the first on / off switch to turn it off; 2) controlling the second on / off switch to turn it on; and 3) applying a PWM signal to the upper bridge branch switch of the further bridge branch, and applying no drive signal or a drive signal complementary to the PWM signal (i.e., the PWM signal applied to the upper bridge branch switch of the further bridge branch) to the lower bridge branch switch of the further bridge branch.

[0052] Fig. Figure 4 shows a method 500 for controlling a vehicle-mounted charging system according to a further embodiment of the present invention. The method 500 can be implemented by controlling the system 100 by means of the control unit 40 described above.

[0053] Method 500 comprises the following: The controller 40 controls (block 510) the operation of the vehicle-mounted charging system by controlling the on / off switches and the combination states of the upper and lower bridge branch switches of two further bridge branches of the several bridge branches that are not connected to the second on / off switch 32 (e.g. the two bridge arms 20B and 20C that are not connected to the second on / off switch).

[0054] The following control method applies to the two remaining bridge branches: Two switches located at corresponding positions on the two bridge branches are controlled by the same drive signal. With this control method, the switching transistors at the corresponding positions on the two bridge branches receive identical drive signals. This means that when the switching transistor of one bridge branch is switched on, the corresponding switching transistor of the other bridge branch is also switched on; conversely, when the switching transistor of one bridge branch is switched off, the corresponding switching transistor of the other bridge branch is also switched off. This control method is suitable for scenarios in which two bridge branches must operate synchronously, for example, when both bridge branches must supply current simultaneously to generate the required magnetic field or torque.

[0055] The following section explains the substeps contained in block 510.

[0056] In block 511, the control unit 40 compares the current power output by the converter with the current charging power required by the traction battery.

[0057] If the comparison result shows that the instantaneous power output by the converter is greater than the current charging power required by the traction battery, procedure 500 in block 512 is initiated.

[0058] In block 512, the controller 40 controls the bidirectional boost / step-down converter such that it operates in forward boost mode in order to store a reactive power component of the energy output by the converter in the DC capacitor and to transfer electrical energy from the external AC power source to the traction battery: 1) Controlling the first on / off switch so that it is switched off; 2) Controlling the second on / off switch so that it is switched on; 3) Applying a first PWM signal to the lower bridge branch switch of one bridge branch of the two other bridge branches, and applying no drive signal or a drive signal complementary to the first PWM signal to the upper bridge branch switch of one bridge branch;and 4) applying a second PWM signal to the lower bridge branch switch of the other bridge branch of the two further bridge branches, and applying no drive signal or a drive signal complementary to the second PWM signal to the upper bridge branch switch of the other bridge branch.;

[0059] If the comparison result shows that the instantaneous power output by the converter is less than the current charging power required by the traction battery, procedure 500 in block 513 is initiated.

[0060] In block 513, the controller 40 controls the bidirectional boost / drag converter such that it operates in reverse buck mode to release the energy stored in the DC capacitor, thus performing reactive power compensation for the converter output and transferring electrical energy from the external AC power source to the traction battery: 1) Controlling the first on / off switch so that it is switched off; 2) Controlling the second on / off switch so that it is switched on; 3) Applying a first PWM signal to the upper bridge branch switch of one of the two other bridge branches, and applying no drive signal or a drive signal complementary to the first PWM signal to the lower bridge branch switch of one of the other bridge branches;and 4) applying a second PWM signal to the upper bridge branch switch of the other bridge branch of the two further bridge branches, and applying no drive signal or a drive signal complementary to the second PWM signal to the lower bridge branch switch of the other bridge branch.;

[0061] In this embodiment, the first PWM signal and the second PWM signal are completely identical; there is no phase difference between them.

[0062] Fig. Figure 5 shows a method 600 for controlling a vehicle-mounted charging system according to a further embodiment of the present invention. The method 600 can be implemented by controlling the system 100 by means of the control unit 40 described above.

[0063] Method 600 comprises the following: The controller 40 controls (block 610) the operation of the vehicle-mounted charging system by controlling the on / off switches and the combination states of the upper and lower bridge branch switches of two further bridge branches of the several bridge branches that are not connected to the second on / off switch (e.g. the two bridge arms 20B and 20C that are not connected to the second on / off switch 32).

[0064] The following control method applies to the two remaining bridge branches: The control is achieved by phase-shifting the drive signals. This means that for two switches located at corresponding positions on the two bridge branches, their drive signals will have a phase difference (for example, the phase difference might be 180 degrees or 90 degrees). In this way, if the switching transistor of one bridge branch is conducting, the corresponding switching transistor of the other bridge branch can be either off or about to be off; the reverse is also true. This control method can generate a wider variety of current waveforms, thus enabling more precise control of the circuit. Substeps contained in block 610 are explained below.

[0065] In block 611, the control unit 40 compares the current power output by the converter with the current charging power required by the traction battery.

[0066] If the comparison result shows that the instantaneous power output by the converter is greater than the current charging power required by the traction battery, procedure 600 in block 612 is initiated.

[0067] In block 612, the controller 40 controls the bidirectional boost / step-down converter such that it operates in forward boost mode in order to store a reactive power component of the energy output by the converter in the DC capacitor and to transfer electrical energy from the external AC power source to the traction battery: 1) Controlling the first on / off switch so that it is switched off; 2) Controlling the second on / off switch so that it is switched on; 3) Applying a first PWM signal to the lower bridge branch switch of one bridge branch of the two other bridge branches, and applying no drive signal or a drive signal complementary to the first PWM signal to the upper bridge branch switch of one bridge branch;and 4) applying a second PWM signal to the lower bridge branch switch of the other bridge branch of the two further bridge branches, and applying no drive signal or a drive signal complementary to the second PWM signal to the upper bridge branch switch of the other bridge branch.;

[0068] If the comparison result shows that the instantaneous power output by the converter is less than the current charging power required by the traction battery, procedure 600 in block 613 is initiated.

[0069] In block 613, the controller 40 controls the bidirectional boost / drag converter such that it operates in reverse buck mode to release the energy stored in the DC capacitor, thus performing reactive power compensation for the converter output and transferring electrical energy from the external AC power source to the traction battery: 1) Controlling the first on / off switch so that it is switched off; 2) Controlling the second on / off switch so that it is switched on; 3) Applying a first PWM signal to the upper bridge branch switch of one of the two other bridge branches, and applying no drive signal or a drive signal complementary to the first PWM signal to the lower bridge branch switch of one of the other bridge branches;and 4) applying a second PWM signal to the upper bridge branch switch of the other bridge branch of the two further bridge branches, and applying no drive signal or a drive signal complementary to the second PWM signal to the lower bridge branch switch of the other bridge branch.;

[0070] In this embodiment, there is a phase difference between the first PWM signal and the second PWM signal, for example, a phase shift of 180 degrees or 90 degrees between the two.

[0071] In one embodiment, the controller 60 can be configured to include a memory and a processor. The memory stores an executable instruction which, when executed by the processor, implements the method 400 for controlling a vehicle-mounted charging system according to an embodiment of the present invention.

[0072] According to an embodiment of the present invention, a computer program product is further provided which comprises a computer-executable instruction which, when executed, causes one or more processors to execute the method 400 for controlling a vehicle-mounted charging system according to an embodiment of the present invention.

[0073] It is understood that a processor may be implemented using electronic hardware, computer software, or any combination thereof. Whether such processors are implemented as hardware or software depends on the specific application and the general design constraints imposed on the system. For example, the processor, any part of the processor, or any combination of the processors specified in the present invention may be implemented as a microprocessor, a microcontroller, a digital signal processor (DSP), a field-programmable gate array (FPGA), a programmable logic device (PLD), a state machine, gate logic, discrete hardware circuits, and other suitable processing components configured to perform various functions described in the present disclosure.The functions of the processor, any part of the processor, or any combination of processors specified in the present invention can be implemented as software executed by a microprocessor, a microcontroller, a DSP, or other suitable platforms.

[0074] It is understood that software, in its broadest sense, is to be understood as instruction, instruction set, code, code segment, program code, program, subroutine, software module, application, software application, software package, routine, subroutine, object, running thread, process, function, etc. The software may reside on a computer-readable medium. The computer-readable medium may, for example, include memory, and the memory may be, for example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic stripe), optical disk, smart card, flash memory device, random-access memory (RAM), read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), register, or removable media. Although memory is presented in various aspects of this disclosure as being separate from the processor, memory may also be located within the processor (e.g., a cache or a register).

[0075] Although some embodiments have been described above, these embodiments are only given as examples and are not intended to limit the scope of the invention. The appended claims and their equivalent substitutions aim to include any modifications, substitutions, and alterations within the scope and basic ideas of the present invention.

Claims

[1] Vehicle-mounted charging system, comprising: a converter that can be coupled to an external AC power source outside a vehicle on the one hand and to a traction battery of the vehicle on the other hand; an inverter coupled between the traction battery and an electric motor of the vehicle, comprising several bridge branches and a DC capacitor, each of the bridge branches comprising an upper bridge branch switch coupled to a positive busbar and a lower bridge branch switch coupled to a negative busbar, and wherein the positive and negative busbars are bridged by the DC capacitor; a group of on / off switches coupled between the inverter and the vehicle's traction battery, wherein the group of on / off switches comprises a first on / off switch and a second on / off switch, the first on / off switch being located in the positive busbar and the second on / off switch being connected to the intermediate node between the upper bridge branch switch and the lower bridge branch switch is connected to one of the several bridge branches; and a controller configured to control the operation of the vehicle-mounted charging system by controlling the on / off switches as well as the combined states of the upper and lower bridge branch switches of another bridge branch or two other bridge branches of the multiple bridge branches that are not connected to the second on / off switch. [2] Vehicle-mounted charging system according to claim 1, wherein the intermediate node between the upper bridge branch switch and the lower bridge branch switch of each of the bridge branches is coupled to one of several windings of the vehicle motor; and the DC capacitor, the further bridge branch and at least some of the several windings of the motor form a bidirectional boost / drag converter, the bidirectional boost / drag converter having a forward boost mode and a reverse buck mode, which are provided for AC charging under different scenarios. [3] Vehicle-mounted charging system according to claim 1, wherein the controller is configured to control the operation of the vehicle-mounted charging system, such that the vehicle-mounted charging system is operated in traction mode, AC charging mode or vehicle-to-load mode of the traction battery. [4] Vehicle-mounted charging system according to claim 1, wherein a switch terminal of the first on / off switch is connected to the switch terminal of one bridge branch which is connected to the positive busbar, the other switch terminal of the first on / off switch is connected to a switch terminal of the second on / off switch, and the other switch terminal of the second on / off switch is connected to the intermediate node between the upper bridge branch switch and the lower bridge branch switch of the first bridge branch. [5] Vehicle-mounted charging system according to claim 2, wherein the control system is configured to to compare the current power output of the converter with the current charging power required by the traction battery; to switch the bidirectional boost / step-down converter into forward boost mode if the comparison result indicates that the instantaneous power output by the converter is greater than the current charging power required by the traction battery; and to switch the bidirectional boost / descent converter into reverse-dip mode if the comparison result indicates that the instantaneous power output by the converter is less than the current charging power required by the traction battery. [6] Vehicle-mounted charging system according to claim 2 or 5, wherein the controller controls the bidirectional boost / step-down converter such that it is operated in forward boost mode to store a reactive power component of the energy output by the converter in the DC capacitor and to transfer electrical energy from the external AC power source to the traction battery: - Controlling the first on / off switch in such a way that it is switched off; - Controlling the second on / off switch so that it is switched on; and - Applying a PWM signal to the lower bridge branch switch of the further bridge branch, and not applying a drive signal or a drive signal complementary to the PWM signal to the upper bridge branch switch of the further bridge branch. [7] Vehicle-mounted charging system according to claim 2 or 5, wherein the controller controls the bidirectional boost / drag converter such that it is operated in reverse buck mode to release the energy stored in the DC capacitor, so that reactive power compensation is performed for the converter output and electrical energy is transferred from the external AC power source to the traction battery: - Controlling the first on / off switch in such a way that it is switched off; - Controlling the second on / off switch so that it is switched on; and - Applying a PWM signal to the upper bridge branch switch of the further bridge branch, and not applying a drive signal or a drive signal complementary to the PWM signal to the lower bridge branch switch of the further bridge branch. [8] Vehicle-mounted charging system according to claim 1, wherein the control is configured to determine the further bridge branch such that: Determining the position of the q-axis of the rotor of the vehicle engine; and selecting the further bridge branch from the bridge branches that are not connected to the second on / off switch, such that the equivalent magnetic flux generated by the stator coil is directed as close as possible to the position of the q-axis of the rotor. [9] Vehicle-mounted charging system according to claim 2 or 5, wherein the controller controls the bidirectional boost / step-down converter such that it is operated in forward boost mode to store a reactive power component of the energy output by the converter in the DC capacitor and to transfer electrical energy from the external AC power source to the traction battery: - Controlling the first on / off switch in such a way that it is switched off; - Controlling the second on / off switch so that it is switched on; - Applying a PWM signal to the lower bridge branch switch of one of the two other bridge branches, and applying no drive signal or a drive signal complementary to the PWM signal to the upper bridge branch switch of that one bridge branch; and - Applying a drive signal that is identical or phase-shifted to the drive signal at the upper and lower bridge branch switches of one bridge branch of the two other bridge branches, to the upper and lower bridge branch switches of the other bridge branch of the two other bridge branches. [10] Vehicle-mounted charging system according to claim 2 or 5, wherein the controller controls the bidirectional boost / drag converter such that it is operated in reverse buck mode to release the energy stored in the DC capacitor, so that reactive power compensation is performed for the converter output and electrical energy is transferred from the external AC power source to the traction battery: - Controlling the first on / off switch in such a way that it is switched off; - Controlling the second on / off switch so that it is switched on; - Applying a PWM signal to the upper bridge branch switch of one of the two other bridge branches, and applying no drive signal or a drive signal complementary to the PWM signal to the lower bridge branch switch of that one bridge branch; and - Applying a drive signal that is identical or phase-shifted to the drive signal at the upper and lower bridge branch switches of one bridge branch of the two other bridge branches, to the upper and lower bridge branch switches of the other bridge branch of the two other bridge branches. [11] Method for controlling a vehicle-mounted charging system, wherein the vehicle-mounted charging system comprises: a converter that can be coupled to an external AC power source outside a vehicle on the one hand and to a traction battery of the vehicle on the other hand; an inverter coupled between the traction battery and an electric motor of the vehicle, comprising several bridge branches and a DC capacitor, each of the bridge branches comprising an upper bridge branch switch coupled to a positive busbar and a lower bridge branch switch coupled to a negative busbar, and wherein the positive and negative busbars are bridged by the DC capacitor; and a group of on / off switches coupled between the inverter and the traction battery of the vehicle. where the group of on / off switches comprises a first on / off switch and a second on / off switch, wherein the first on / off switch is arranged in the positive busbar and the second on / off switch is connected to the intermediate node between the upper bridge branch switch and the lower bridge branch switch of one of the multiple bridge branches; the procedure includes: Controlling the operation of the vehicle-mounted charging system by controlling the on / off switches and the combined states of the upper and lower bridge branch switches of another bridge branch or two other bridge branches of the multiple bridge branches that are not connected to the second on / off switch.

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