Battery ac heating circuit for a vehicle

Abstract

The application relates to the technical field of battery heating, and provides a battery alternating current heating circuit of a vehicle. The battery alternating current heating circuit comprises a transformer, an on-off switch, a power battery and a motor control circuit; one end of a secondary side of the transformer is connected with a positive electrode of the power battery, the other end of the secondary side of the transformer is connected with a high-voltage bus positive electrode of the motor control circuit, and the ratio of the number of turns of a primary side of the transformer to the number of turns of the secondary side of the transformer is greater than 1; a negative electrode of the power battery is connected with a high-voltage bus negative electrode of the motor control circuit; one end of the primary side of the transformer is connected with one end of the on-off switch, and the other end of the on-off switch and the other end of the primary side of the transformer are connected with an output end of the motor control circuit. The battery alternating current heating circuit of the vehicle provided by the application can reduce the heat generation of the motor control circuit when the power battery is heated, and can heat the battery regardless of whether the vehicle is running or not.

Description

Technical Field

[0001] This application relates to the field of battery heating technology, specifically to an AC heating circuit for a vehicle battery. Background Technology

[0002] In low-temperature environments, the internal materials of electric vehicles' batteries undergo changes, limiting charging and discharging power. Therefore, to ensure normal battery operation, the electric vehicle's battery needs to be heated. One related technology involves AC heating of the battery. This technology uses a motor control circuit, composed of an inverter and a motor, connected to the battery for charging and discharging cycles to generate AC current on the bus, thus heating the battery. However, generating sufficient current to heat the battery requires a large-amplitude oscillating current within the motor windings. This current causes severe overheating of the motor control circuit, limiting the battery heating power. Furthermore, current AC heating technology is generally only suitable for stationary vehicles and is difficult to apply while the vehicle is in motion. Summary of the Invention

[0003] This application aims to at least solve one of the technical problems existing in the related art. To this end, this application proposes a battery AC heating circuit for a vehicle that can reduce the heat generated by the motor control circuit when the power battery is heated.

[0004] This application also proposes an electric vehicle.

[0005] The vehicle battery AC heating circuit according to the first aspect of this application includes:

[0006] Transformers, on / off switches, power batteries, and motor control circuits;

[0007] One end of the secondary side of the transformer is connected to the positive terminal of the power battery, and the other end of the secondary side of the transformer is connected to the positive terminal of the high-voltage bus of the motor control circuit. The turns ratio of the primary side to the secondary side of the transformer is greater than 1.

[0008] The negative terminal of the power battery is connected to the negative terminal of the high-voltage bus of the motor control circuit.

[0009] One end of the primary side of the transformer is connected to one end of the on / off switch, and the other end of the on / off switch and the other end of the primary side of the transformer are connected to the output terminal of the motor control circuit.

[0010] The motor control circuit includes a three-phase inverter circuit and a three-phase drive motor. One end of each phase winding of the three-phase drive motor is connected to the other end, and the other end is connected to the three-phase inverter circuit.

[0011] By connecting a transformer with a primary-to-secondary turns ratio greater than 1 and an on / off switch between the power battery and the motor control circuit, the primary side only needs a small current to meet the heating power requirements when heating the power battery. Therefore, the additional current added to the motor control circuit is reduced during heating, and the heat generation of the motor control circuit will not be significantly increased. This reduces the heat generation of the motor control circuit when the power battery is heated, thus avoiding affecting the normal operation of the motor control circuit.

[0012] According to one embodiment of this application, the other end of the on / off switch is connected to the neutral point of the three-phase drive motor, or to the terminal connecting any motor winding of the three-phase drive motor to the three-phase inverter circuit, and the other end of the primary side of the transformer is connected to the negative terminal of the high-voltage bus of the motor control circuit through a DC blocking capacitor.

[0013] According to one embodiment of this application, the other end of the on / off switch is connected to the terminal connecting the first winding of the three-phase drive motor to the three-phase inverter circuit, and the other end of the primary side of the transformer is connected to the terminal connecting the second winding of the three-phase drive motor to the three-phase inverter circuit.

[0014] According to one embodiment of this application, the other end of the on / off switch is connected to the terminal of any winding of the three-phase drive motor connected to the three-phase inverter circuit, and the other end of the primary side of the transformer is connected to the neutral point of the three-phase drive motor.

[0015] According to one embodiment of this application, a DC blocking capacitor is also included;

[0016] The DC blocking capacitor is connected between the other end of the primary side of the transformer and the output terminal of the motor control circuit.

[0017] The vehicle battery AC heating circuit according to the second aspect embodiment of this application includes:

[0018] Transformers, on / off switches, power batteries, and motor control circuits;

[0019] One end of the secondary side of the transformer is connected to the positive terminal of the power battery, and the other end of the secondary side of the transformer is connected to the positive terminal of the high-voltage bus of the motor control circuit. The turns ratio of the primary side to the secondary side of the transformer is greater than 1.

[0020] The negative terminal of the power battery is connected to the negative terminal of the high-voltage bus of the motor control circuit.

[0021] One end of the primary side of the transformer is connected to one end of the on / off switch, and the other end of the primary side of the transformer and the other end of the on / off switch are connected to the output terminal of the motor control circuit.

[0022] The motor control circuit includes an inverter circuit.

[0023] According to one embodiment of this application, the inverter circuit includes a first half-bridge and a second half-bridge;

[0024] The first half-bridge includes a first upper bridge arm and a first lower bridge arm. One end of the first upper bridge arm is connected to the positive terminal of the high-voltage busbar, the other end of the first upper bridge arm is connected to the other end of the on / off switch and one end of the first lower bridge arm, and the other end of the first lower bridge arm is connected to the negative terminal of the high-voltage busbar.

[0025] The second half-bridge includes a second upper bridge arm and a second lower bridge arm. One end of the second upper bridge arm is connected to the positive terminal of the high-voltage bus. One end of the second lower bridge arm is connected to the other end of the primary side of the transformer and one end of the second lower bridge arm. The other end of the second lower bridge arm is connected to the negative terminal of the high-voltage bus.

[0026] According to one embodiment of this application, the second upper bridge arm includes a first capacitor, and the second lower bridge arm includes a second capacitor.

[0027] According to one embodiment of this application, a DC blocking capacitor is also included;

[0028] The DC blocking capacitor is located between the other end of the primary winding of the transformer and the inverter circuit.

[0029] The electric vehicle according to the second aspect of this application includes the battery AC heating circuit of the vehicle described in any of the above embodiments.

[0030] The above-described one or more technical solutions in the embodiments of this application have at least one of the following technical effects:

[0031] By connecting a transformer with a primary-to-secondary turns ratio greater than 1 and an on / off switch between the power battery and the motor control circuit, the primary current can be relatively small to meet the heating power requirements when heating the power battery. Therefore, the additional current to the motor control circuit is reduced during heating, and it does not affect the heat generation of the motor control circuit. This reduces the heat generated by the motor control circuit when the power battery is heated, preventing it from affecting the normal operation of the motor control circuit. Simultaneously, the high-frequency AC voltage of the drive transformer originates from the PWM voltage of the inverter bridge during inverter operation (the fundamental frequency of the high-frequency AC voltage is equal to the PWM frequency). Moreover, the inverter can provide this high-frequency PWM wave whether the vehicle is parked or driving. Therefore, this solution can achieve battery heating functionality both when the vehicle is parked and driving. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the AC heating circuit for a vehicle battery in related technologies;

[0034] Figure 2 This is a schematic diagram of the structure of the vehicle battery AC heating circuit provided in the embodiments of this application;

[0035] Figure 3 This is a schematic diagram of the equivalent circuit structure of the battery AC heating circuit provided in the embodiments of this application;

[0036] Figure 4 This is a schematic diagram of the structure of a battery AC heating circuit provided in another embodiment of this application;

[0037] Figure 5 This is a schematic diagram of the structure of a battery AC heating circuit provided in another embodiment of this application;

[0038] Figure 6 This is a schematic diagram of the structure of a battery AC heating circuit provided in another embodiment of this application;

[0039] Figure 7 This is a schematic diagram of the structure of a battery AC heating circuit provided in another embodiment of this application;

[0040] Figure 8 This is a schematic diagram of the structure of a battery AC heating circuit provided in another embodiment of this application;

[0041] Figure 9 This is a schematic diagram of the structure of a battery AC heating circuit provided in another embodiment of this application;

[0042] Figure 10 This is a schematic diagram of the structure of a battery AC heating circuit provided in another embodiment of this application;

[0043] Figure 11 This is a schematic diagram of the structure of a battery AC heating circuit provided in another embodiment of this application;

[0044] Figure 12 This is a schematic diagram of the structure of a battery AC heating circuit provided in another embodiment of this application. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0046] The battery AC heating circuit of the vehicle provided in this application will be described in detail and explained through several specific embodiments.

[0047] In low-temperature environments, the charging and discharging power of electric vehicles is limited due to changes in the internal material properties of the battery. Therefore, to achieve fast charging or normal operation in low-temperature environments, the electric vehicle's battery needs to be heated. Existing heating methods typically use multiple PTC automotive heaters to heat the coolant, thereby heating the battery. However, this indirect heating method requires heat to be transferred to the battery through the coolant and external battery structure, resulting in a significant amount of heat not being effectively transferred to the battery, leading to a slow temperature rise and low energy utilization. Therefore, related technologies, such as... Figure 1 As shown, it uses a motor control circuit consisting of an inverter circuit and a motor connected to the power battery for charging and discharging cycles, thereby heating the power battery. However, in order to effectively stimulate the bus voltage fluctuation and thus stimulate the alternating current in the battery, this heating method requires a large-amplitude oscillating current in the motor windings. These currents will cause the motor control circuit to overheat severely, resulting in a limitation on the heating power. On the other hand, this technology is difficult to use in driving conditions because it is difficult for the motor current to achieve large-amplitude high-frequency oscillations under driving conditions.

[0048] Therefore, in one embodiment, such as Figure 2 As shown, a battery AC heating circuit for a vehicle is provided, comprising:

[0049] Transformer Tx, on / off switch K, power battery U1 and motor control circuit 1;

[0050] One end of the secondary side of the transformer Tx is connected to the positive terminal of the power battery U1, and the other end of the secondary side of the transformer Tx is connected to the positive terminal of the high voltage bus of the motor control circuit 1. The turns ratio of the primary side of the transformer Tx to the secondary side of the transformer Tx is greater than 1.

[0051] The negative terminal of the power battery U1 is connected to the negative terminal of the high-voltage bus of the motor control circuit 1;

[0052] One end of the primary side of the transformer Tx is connected to one end of the on / off switch K, and the other end of the on / off switch K and the other end of the primary side of the transformer Tx are connected to the output terminal of the motor control circuit 1.

[0053] The motor control circuit 1 includes a three-phase inverter circuit 11 and a three-phase drive motor 12. One end of each phase winding of the three-phase drive motor 12 is connected to the other end, and the other end is connected to the three-phase inverter circuit 11.

[0054] Among them, the negative terminal of the high-voltage bus of motor control circuit 1 is the negative terminal of the high-voltage bus of the three-phase inverter circuit.

[0055] In one embodiment, the three-phase inverter circuit 1 includes multiple half-bridges and a capacitor Cdc. Each half-bridge includes an upper arm and a lower arm. One end of the capacitor Cdc is connected to the upper arm of each half-bridge to be connected to the positive terminal of the DC bus of the three-phase inverter circuit 1, and the other end is connected to the lower arm of each half-bridge to be connected to the negative terminal of the DC bus of the three-phase inverter circuit 1. Each upper arm and each lower arm includes a switch.

[0056] For example, such as Figure 2 As shown, the first upper bridge switch Q1, the second upper bridge switch Q3, and the third upper bridge switch Q5 form three upper bridge arms. One end of each of these switches is connected to the positive terminal of each power battery in the power battery U1. The first lower bridge switch Q2, the second lower bridge switch Q4, and the third lower bridge switch Q6 form three lower bridge arms. One end of the first lower bridge switch Q2 is connected to the other end of the first upper bridge switch Q1, one end of the second lower bridge switch Q4 is connected to the other end of the second upper bridge switch Q3, and one end of the third lower bridge switch Q6 is connected to the other end of the third upper bridge switch Q5. The other ends of these switches are connected to the negative terminal of each power battery in the power battery U1.

[0057] In one embodiment, the above circuit structure can be equivalent to as follows: Figure 3 The equivalent circuit is shown. Since the capacitance of other equipment on the high-voltage DC bus of the vehicle is generally small and negligible, the motor control circuit can be equivalent to the total parallel capacitance Cdc,bus on the high-voltage DC bus, and the AC voltage source UAC connected to the primary side of the transformer Tx. This allows a transformer Tx to be connected in series between the DC bus and the power battery U1, and the transformer is driven by AC current on the primary side of the transformer Tx. In this way, an alternating voltage is generated between Cdc,bus and the power battery U1, which causes the battery to generate a large AC current, ultimately heating the power battery U1.

[0058] When the battery needs to be heated, the on / off switch K is closed, and the switching frequency of the three-phase inverter circuit 11 of the motor control circuit is adjusted to fr. The three-phase drive motor is then controlled according to normal SVPWM and other modulation modes. At this time, an AC common-mode current will flow out of the motor control circuit and cause a large alternating current to be generated on the secondary side of the transformer Tx through the primary side. This alternating current is then used to flow through the power battery and heat it.

[0059] When the heating power needs to be adjusted, the switching frequency of the three-phase inverter circuit 11 can be adjusted away from fr, thereby gradually moving away from the resonant frequency. The primary impedance of the transformer Tx gradually increases, the current gradually decreases, and the heating power decreases. When heating is not needed at all, the on / off switch K can be disconnected.

[0060] Since the turns ratio K of the primary side to the secondary side of transformer Tx is greater than 1, according to the transformer turns ratio relationship, the primary current : secondary current = 1 : K. Therefore, when there is a large oscillating current on the secondary side, the corresponding current on the primary side will be very small. In this case, only a small current needs to flow through the primary side to meet the heating power requirement, which means that only a small amount of current flows through the motor control circuit. Because the primary current is relatively small during heating, the additional current added to the switching transistors of the three-phase drive motor and the three-phase inverter circuit in the motor control circuit is very small when driving the motor. Therefore, it has almost no impact on the heating of the three-phase drive motor and the three-phase inverter circuit switches, and has little impact on the power output of the electric drive system. This reduces the heat generation of the motor control circuit when the power battery is heated.

[0061] By connecting a transformer with a primary-to-secondary turns ratio greater than 1 and an on / off switch between the power battery and the motor control circuit, the primary current can be relatively small to meet the heating power requirements when heating the power battery. Therefore, the additional current added to the motor control circuit is reduced during heating, which will not affect the heating of the motor control circuit. This reduces the heat generated by the motor control circuit when the power battery is heated, thus avoiding affecting the normal operation of the motor control circuit.

[0062] In one embodiment, such as Figure 4 or Figure 5 As shown, the other end of the on / off switch K is connected to the neutral point of the three-phase drive motor 12, or to the terminal connecting any motor winding of the three-phase drive motor 12 to the three-phase inverter circuit 11. The other end of the primary side of the transformer Tx is connected to the negative terminal of the high-voltage bus of the motor control circuit 1 through the capacitor Cr.

[0063] In one embodiment, such as Figure 4As shown, the other end of the on / off switch K is connected to the neutral point of the three-phase drive motor 12, and the other end of the primary side of the transformer Tx is connected to the negative terminal of the high-voltage bus of the three-phase inverter circuit 11 through the capacitor Cr.

[0064] When the three-phase inverter circuit 11 drives the three-phase drive motor 12, regardless of whether the three-phase drive motor 12 is stationary or running, its neutral point voltage exhibits high-frequency voltage fluctuations. The frequency of these fluctuations is consistent with the switching frequency of the three-phase inverter circuit 11, and the amplitude of the fluctuations varies depending on the operating conditions, but is on the same order of magnitude as the power battery voltage. When it is necessary to heat the power battery, the switch K is closed, and the three-phase inverter circuit 11 adjusts its switching frequency to fr, controlling the three-phase drive motor 12 according to normal SVPWM or other modulation modes. At this time, an AC common-mode current flows out of the neutral point, causing a large alternating current to be generated on the secondary side of the transformer through the primary side. This alternating current flows through the power battery and then heats it.

[0065] In one embodiment, such as Figure 5 As shown, in addition to connecting the other end of the on / off switch K to the neutral point of the three-phase drive motor 12, the other end of the on / off switch K can also be connected to any one of the motor windings in the three-phase drive motor 12 to reuse one phase half-bridge in the three-phase inverter circuit 11. For example, the other end of the on / off switch K is connected to the motor windings of switches Q5 and Q6 in the three-phase drive motor 12 that are connected to the three-phase inverter circuit 11. When it is necessary to heat the power battery, the switch K is closed, the three-phase inverter circuit 11 adjusts the switching frequency to fr, and controls the three-phase drive motor 12 according to normal SVPWM or other modulation modes. At this time, an AC common-mode current flows out of the motor winding connected to the other end of the switch K, and through the primary side, it causes a large alternating current to be generated on the secondary side of the transformer. This alternating current flows through the power battery and then heats the power battery.

[0066] In one embodiment, such as Figure 6 As shown, the other end of the on / off switch K is connected to the terminal connecting the first winding of the three-phase drive motor 12 and the three-phase inverter circuit 11, and the other end of the primary side of the transformer is connected to the terminal connecting the second winding of the three-phase drive motor 12 and the three-phase inverter circuit 11.

[0067] The first winding and the second winding are different motor windings.

[0068] For example, such as Figure 6 As shown, the other end of the on / off switch K is connected to the first motor windings of switches Q3 and Q4 in the three-phase drive motor 12 that are connected to the three-phase inverter circuit 11, and the other end of the transformer primary side is connected to the first motor windings of switches Q5 and Q6 in the three-phase drive motor 12 that are connected to the three-phase inverter circuit 11, thereby reusing the two-phase half-bridge of the three-phase inverter circuit 11.

[0069] Considering that when the other end of the on / off switch K is connected to the first winding of the three-phase drive motor 12 and the other end of the transformer primary side is connected to the second winding of the three-phase drive motor 12, when the three-phase drive motor 12 is stationary or at low speed, if ordinary SVPWM modulation is used, the excitation voltage on the primary side of the transformer Tx will be very small because the voltage difference between each phase is very small. Therefore, when the other end of the on / off switch K is connected to the first winding of the three-phase drive motor 12 and the other end of the transformer primary side is connected to the second winding of the three-phase drive motor 12, a three-phase PWM modulation method with high and low level position switching can be used to increase the primary side AC voltage. In this case, only the high and low level positions of any one of the two multiplexed half-bridges need to be switched.

[0070] For example, such as Figure 6 As shown, the other end of the on / off switch K is connected to the first half-bridge composed of Q3 and Q4, and the other end of the primary side of the transformer is connected to the second half-bridge composed of Q5 and Q6. Although the average voltage is still calculated according to SVPWM or other PWM modulation methods, the relative positions of the PWM high levels in one of the half-bridges, such as Q5 and Q6, are swapped during the switch's on-time. That is, before the timing shift, the on-time centers of the three high-voltage side switches Q1, Q3, and Q5 are aligned at a single moment, while the on-time centers of the three low-voltage side switches Q2, Q4, and Q6 are aligned at moments differing by half a PWM cycle. After the timing shift of Q5 and Q6, Q1, Q3, and Q6 are aligned with the on-time centers of Q2, Q4, and Q5, respectively. At this point, the voltage difference between the first and second windings of the three-phase drive motor increases significantly, thereby effectively driving the primary side of the transformer Tx.

[0071] In one embodiment, such as Figure 7 As shown, the other end of the on / off switch K is connected to the terminal of any winding of the three-phase drive motor 12 and the three-phase inverter circuit 11, and the other end of the primary side of the transformer Tx is connected to the neutral point of the three-phase drive motor 12.

[0072] For example, such as Figure 7 As shown, the other end of the on / off switch K is connected to the motor windings of switches Q5 and Q6 in the three-phase drive motor 12, which are connected to the three-phase inverter circuit 11. The other end of the primary side of the transformer is connected to the neutral point of the three-phase drive motor 12, thereby reusing one phase half-bridge of the three-phase inverter circuit 11 and the neutral point of the three-phase drive motor 12.

[0073] Considering that when the other end of the on / off switch K is connected to the motor winding of the three-phase drive motor 12, and the other end of the transformer primary side is connected to the neutral point of the three-phase drive motor 12, the primary side excitation voltage is still insufficient when the vehicle is stationary or moving at low speed. Therefore, when the other end of the on / off switch K is connected to the motor winding of the three-phase drive motor 12, and the other end of the transformer primary side is connected to the neutral point of the three-phase drive motor 12, a three-phase PWM modulation method with high and low level position switching can be used to increase the primary side AC voltage. At this time, it is only necessary to switch the high and low level positions of any one phase in the three-phase inverter circuit 11.

[0074] To prevent transformer Tx from becoming magnetically saturated, in one embodiment, such as Figures 6-7 As shown, the battery AC heating circuit also includes a DC blocking capacitor Cr;

[0075] The DC blocking capacitor Cr is connected between the other end of the primary side of the transformer Tx and the output terminal of the motor control circuit 1.

[0076] By adding a DC blocking capacitor Cr between the primary side of transformer Tx and motor control circuit 1, the DC component in the voltage across the primary side is blocked, thereby preventing the transformer from becoming magnetically saturated.

[0077] also, Figures 4-7 The DC blocking capacitor Cr, the leakage inductance of the transformer Tx, and the common-mode inductance of the three-phase drive motor 12 can form an LC resonant circuit. The resonant frequency fr of this circuit can be designed by selecting the value of the DC blocking capacitor Cr, meaning it can be designed to be very high. At the resonant frequency fr, the impedances of Cr, the transformer leakage inductance, and the motor common-mode inductance cancel each other out, the primary side exhibits pure resistivity, the primary impedance reaches a minimum, and the corresponding primary current reaches a maximum. The secondary side battery heating current also reaches a maximum. At this point, the switching frequency of the three-phase inverter circuit can be adjusted up to the resonant frequency fr, maximizing the heating current.

[0078] Since the designed oscillation current frequency can be very high, such as 10kHz or 20kHz, the human ear is not sensitive to such high frequencies, thus reducing the acoustic noise generated when the battery is heated.

[0079] Meanwhile, since the high-frequency oscillating AC current on the secondary side only flows back and forth between the power battery and the DC bus support capacitor Cdc, and because the frequency is very high, while the voltage fluctuation of the capacitor is inversely proportional to the current frequency, the voltage fluctuation on the capacitor Cdc is relatively small.

[0080] For example, taking an electric vehicle model with a battery internal resistance of 0.03Ω, a battery voltage of 400V, a transformer leakage inductance + motor common-mode inductance of 20uH, and a battery heating requirement of 10kW as an example, calculations show that the transformer Tx ratio is 10.4, the effective value of the secondary current is 577A, and the primary current is only 55A. The average current per phase of the three-phase drive motor increases by 18.51A, while the rated current per phase of the drive motor in a new energy vehicle can reach over 200A. The additional current accounts for less than 10% of the motor's rated current. If the capacitor Cdc = 500uF and the switching frequency is 15kHz, the bus voltage fluctuation amplitude is 17.3V, meaning there is a fluctuation of about 4.3% in the bus voltage. This is completely tolerable for electrical appliances on the high-voltage bus.

[0081] In one embodiment, such as Figure 8 As shown, a vehicle battery AC heating circuit is also provided, comprising:

[0082] Transformer Tx, on / off switch K, power battery U1, and motor control circuit;

[0083] One end of the secondary side of the transformer Tx is connected to the positive terminal of the power battery U1, and the other end of the secondary side of the transformer Tx is connected to the positive terminal of the high voltage bus of the motor control circuit. The turns ratio of the primary side to the secondary side of the transformer is greater than 1.

[0084] The negative terminal of the power battery U1 is connected to the negative terminal of the high-voltage bus of the motor control circuit.

[0085] One end of the primary side of the transformer Tx is connected to one end of the on / off switch K, and the other end of the primary side of the transformer Tx and the other end of the on / off switch K are connected to the output terminal of the motor control circuit.

[0086] The motor control circuit includes an inverter circuit 11. The negative terminal of the high-voltage bus of the motor control circuit is the negative terminal of the high-voltage bus of the inverter circuit 11, and the output terminal of the motor control circuit is the output terminal of the inverter circuit 11.

[0087] In one embodiment, the inverter circuit 11 can be a full-bridge inverter circuit or a half-bridge inverter circuit. In this case, the AC current on the primary side of the transformer Tx can be generated by the inverter circuit 11.

[0088] Since the turns ratio K of the primary side to the secondary side of transformer Tx is greater than 1, according to the transformer turns ratio relationship, the ratio of primary current to secondary current is 1:K. Therefore, when there is a large oscillating current on the secondary side, the corresponding current on the primary side will be very small. In this case, only a small current needs to flow through the primary side to meet the heating power requirement. Because the vehicle's motor and its inverter circuit do not participate in heating at this time, the motor's driving function will not be affected in any way.

[0089] By connecting a transformer with a primary-to-secondary turns ratio greater than 1 and an on / off switch between the power battery and the motor control circuit, the primary current can be relatively small to meet the heating power requirements when heating the power battery. Therefore, the additional current added to the motor control circuit is reduced during heating, which will not affect the heating of the motor control circuit. This reduces the heat generated by the motor control circuit when the power battery is heated, thus avoiding affecting the normal operation of the motor control circuit.

[0090] In one embodiment, such as Figure 9 As shown, the inverter circuit 11 includes a first half-bridge and a second half-bridge;

[0091] The first half-bridge includes a first upper bridge arm and a first lower bridge arm. One end of the first upper bridge arm is connected to the positive terminal of the high-voltage busbar, the other end of the first upper bridge arm is connected to the other end of the on / off switch and one end of the first lower bridge arm, and the other end of the first lower bridge arm is connected to the negative terminal of the high-voltage busbar.

[0092] The second half-bridge includes a second upper bridge arm and a second lower bridge arm. One end of the second upper bridge arm is connected to the positive terminal of the high-voltage bus. One end of the second lower bridge arm is connected to the other end of the primary side of the transformer Tx and one end of the second lower bridge arm. The other end of the second lower bridge arm is connected to the negative terminal of the high-voltage bus.

[0093] like Figure 9 As shown, the first upper bridge arm includes a first upper bridge switch Q1, and the first lower bridge arm includes a first lower bridge switch Q2. One end of the first upper bridge switch Q1 is connected to the positive terminal of the high-voltage bus of the inverter circuit, and the other end of the first upper bridge switch Q1 is connected to one end of the first lower bridge switch Q2, forming a first half-bridge. The other end of the first lower bridge switch Q2 is connected to the negative terminal of the high-voltage bus of the inverter circuit. The second upper bridge arm includes a second upper bridge switch Q3, and the second lower bridge arm includes a second lower bridge switch Q4. One end of the second upper bridge switch Q3 is connected to the positive terminal of the high-voltage bus of the inverter circuit, and the other end of the second upper bridge switch Q3 is connected to one end of the second lower bridge switch Q4, forming a second half-bridge. The other end of the second lower bridge switch Q4 is connected to the negative terminal of the high-voltage bus of the inverter circuit. In this case, the inverter circuit 11 is a full-bridge circuit.

[0094] The other end of the on / off switch K is connected between the first upper bridge switch Q1 and the first lower bridge switch Q2, and the other end of the primary side of the transformer is connected between the second bridge switch Q3 and the second lower bridge switch Q4.

[0095] To prevent transformer magnetic saturation, in one embodiment, such as Figure 10As shown, it also includes a DC blocking capacitor Cr, which is located between the other end of the primary side of the transformer Tx and the inverter circuit 11. That is, one end of the DC blocking capacitor Cr is connected to the other end of the primary side of the transformer Tx, and the other end of the DC blocking capacitor Cr is connected between the second upper bridge switch Q3 and the second lower bridge switch Q4.

[0096] In one embodiment, such as Figure 11 As shown, the second upper bridge arm can be the first capacitor Cdc1, and the second lower bridge arm can be the second capacitor Cdc2. That is, the other end of the on / off switch K is connected between the first upper bridge switch Q1 and the first lower bridge switch Q2, and the other end of the primary side of the transformer is connected between the first capacitor Cdc1 and the second capacitor Cdc2. At this time, the inverter circuit 11 is a half-bridge inverter circuit.

[0097] To prevent transformer magnetic saturation, in one embodiment, such as Figure 12 As shown, it also includes a DC blocking capacitor Cr, which is located between the other end of the primary winding of transformer Tx and inverter circuit 11. That is, one end of the DC blocking capacitor Cr is connected to the other end of the primary winding of transformer Tx, and the other end of the DC blocking capacitor Cr is connected between the first capacitor Cdc1 and the second capacitor Cdc2. At this time, the first capacitor Cdc1, the second capacitor Cdc2, and the DC blocking capacitor Cr can be considered as a single capacitor Cr. Simultaneously, the other end of capacitor Cr can also be considered as connected to the positive terminal of a battery, or as connected to a series connection point in a battery, or as connected to the positive terminal of the DC bus of the inverter circuit, etc.

[0098] In one embodiment, an electric vehicle is also provided, which includes a battery AC heating circuit for a vehicle as described in any of the above embodiments.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A battery AC heating circuit for a vehicle, characterized in that, include: Transformers, on / off switches, power batteries, and motor control circuits; One end of the secondary side of the transformer is connected to the positive terminal of the power battery, and the other end of the secondary side of the transformer is connected to the positive terminal of the high-voltage bus of the motor control circuit. The turns ratio of the primary side to the secondary side of the transformer is greater than 1. The negative terminal of the power battery is connected to the negative terminal of the high-voltage bus of the motor control circuit. One end of the primary side of the transformer is connected to one end of the on / off switch, and the other end of the on / off switch and the other end of the primary side of the transformer are connected to the output terminal of the motor control circuit. The motor control circuit includes a three-phase inverter circuit and a three-phase drive motor. One end of each phase winding of the three-phase drive motor is connected to the other end, and the other end is connected to the three-phase inverter circuit.

2. The vehicle battery AC heating circuit according to claim 1, characterized in that, The other end of the on / off switch is connected to the neutral point of the three-phase drive motor, or to the terminal connecting any motor winding of the three-phase drive motor to the three-phase inverter circuit. The other end of the primary side of the transformer is connected to the negative terminal of the high-voltage bus of the motor control circuit through a DC blocking capacitor.

3. The vehicle battery AC heating circuit according to claim 1, characterized in that, The other end of the on / off switch is connected to the terminal connecting the first winding of the three-phase drive motor to the three-phase inverter circuit, and the other end of the primary side of the transformer is connected to the terminal connecting the second winding of the three-phase drive motor to the three-phase inverter circuit. The first winding and the second winding are different motor windings.

4. The vehicle battery AC heating circuit according to claim 1, characterized in that, The other end of the on / off switch is connected to the terminal of any winding of the three-phase drive motor connected to the three-phase inverter circuit, and the other end of the primary side of the transformer is connected to the neutral point of the three-phase drive motor.

5. The vehicle battery AC heating circuit according to claim 3 or 4, characterized in that, It also includes DC blocking capacitors; The DC blocking capacitor is connected between the other end of the primary side of the transformer and the output terminal of the motor control circuit.

6. A battery AC heating circuit for a vehicle, characterized in that, include: Transformers, on / off switches, power batteries, and motor control circuits; One end of the secondary side of the transformer is connected to the positive terminal of the power battery, and the other end of the secondary side of the transformer is connected to the positive terminal of the high-voltage bus of the motor control circuit. The turns ratio of the primary side to the secondary side of the transformer is greater than 1. The negative terminal of the power battery is connected to the negative terminal of the high-voltage bus of the motor control circuit. One end of the primary side of the transformer is connected to one end of the on / off switch, and the other end of the primary side of the transformer and the other end of the on / off switch are connected to the output terminal of the motor control circuit. The motor control circuit includes an inverter circuit.

7. The vehicle battery AC heating circuit according to claim 6, characterized in that, The inverter circuit includes a first half-bridge and a second half-bridge. The first half-bridge includes a first upper bridge arm and a first lower bridge arm. One end of the first upper bridge arm is connected to the positive terminal of the high-voltage busbar, the other end of the first upper bridge arm is connected to the other end of the on / off switch and one end of the first lower bridge arm, and the other end of the first lower bridge arm is connected to the negative terminal of the high-voltage busbar. The second half-bridge includes a second upper bridge arm and a second lower bridge arm. One end of the second upper bridge arm is connected to the positive terminal of the high-voltage bus, and the other end of the second upper bridge arm is connected to the other end of the primary side of the transformer and one end of the second lower bridge arm. The other end of the second lower bridge arm is connected to the negative terminal of the high-voltage bus.

8. The vehicle battery AC heating circuit according to claim 7, characterized in that, The second upper bridge arm includes a first capacitor, and the second lower bridge arm includes a second capacitor.

9. The vehicle battery AC heating circuit according to any one of claims 6-8, characterized in that, It also includes DC blocking capacitors; The DC blocking capacitor is located between the other end of the primary side of the transformer and the inverter circuit.

10. An electric vehicle, characterized in that, Includes the vehicle battery AC heating circuit according to any one of claims 1-9.

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