CN218228714U - Battery heating circuit and electric vehicle based on transformer - Google Patents
Battery heating circuit and electric vehicle based on transformer Download PDFInfo
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Abstract
The embodiment of the application provides a battery heating circuit and electric vehicle based on transformer, relates to power battery technical field. In the battery heating circuit, a first battery half-bridge circuit is formed by connecting a first battery with a second battery in series, a second battery half-bridge circuit is formed by connecting a third battery with a fourth battery in series, and the first battery half-bridge circuit is connected with the second battery half-bridge circuit in parallel; the transformer is provided with a primary side and a secondary side, two ends of the secondary side are respectively connected with the midpoint of the first battery half-bridge circuit and the midpoint of the second battery half-bridge circuit, and one end of the primary side is connected with one endpoint of the preset endpoint set; the three-phase motor is respectively connected with the other end of the primary side and the three-phase inverter, and the three-phase motor is connected with the transformer through the heating relay. The battery heating circuit can realize the technical effects that the heating of components is less when the battery is heated, the battery heating circuit can be used in a driving state, and the influence on the dynamic property of the motor is small.
Description
Technical Field
The application relates to the technical field of power batteries, in particular to a battery heating circuit based on a transformer and an electric vehicle.
Background
At present, a new energy automobile refers to an automobile which adopts unconventional automobile fuel as a power source (or adopts conventional automobile fuel and a novel vehicle-mounted power device), integrates advanced technologies in the aspects of power control and driving of the automobile, and has advanced technical principle, new technology and new structure. The new energy automobile comprises a pure electric automobile, a hybrid electric automobile and the like.
In the prior art, the low-temperature performance of a power battery of an electric automobile is poor, so that the battery temperature needs to be improved at a low temperature. Currently, a commonly used battery heating method generally heats a battery by using a cold zone liquid after heating the cold zone liquid by using Positive Temperature Coefficient (PTC) resistors, an electric drive system to generate heat and the like, so as to realize indirect heating, or realizes charging and discharging of a motor winding through a motor controller, so that alternating current is generated in the battery, and the battery is heated by heating of internal resistance of the battery, namely, the internal resistance of the battery is directly heated, or the battery is self-heated. In the current common battery heating method, the indirect heating method has low efficiency, and a large amount of heat cannot be effectively transferred to the battery and is dissipated to the environment; the heat transfer is slow, the heat needs to be input into the battery through cold zone liquid, the external structure of the battery and the like, and the temperature rise of the battery is slow; the battery is unevenly heated, and the temperature rise of the battery core close to the cold area liquid is fast; when the traditional method of directly heating by using a motor winding is adopted, the heating current frequency is lower, the alternating current frequency for directly heating is about 2kHz generally, the human ear is very sensitive, and the noise is very large; the method is not easy to use in the running state of the vehicle, and is easy to cause torque jitter or influence the power output of the motor.
SUMMERY OF THE UTILITY MODEL
An object of the embodiment of the application is to provide a battery heating circuit and electric vehicle based on transformer, can realize when heating the battery that the part generates heat few, feasible car state heats and to the little technological effect of motor dynamic nature influence.
In a first aspect, an embodiment of the present application provides a transformer-based battery heating circuit, which includes a battery pack, a transformer, a three-phase inverter, a heating relay, and a three-phase motor;
the battery pack comprises a first sub battery, a second sub battery, a third sub battery and a fourth sub battery, wherein the first sub battery and the second sub battery are connected in series to form a first battery half-bridge circuit, the third sub battery and the fourth sub battery are connected in series to form a second battery half-bridge circuit, and the first battery half-bridge circuit and the second battery half-bridge circuit are connected in parallel;
the transformer is provided with a primary side and a secondary side, two ends of the secondary side are respectively connected with the midpoint of the first battery half-bridge circuit and the midpoint of the second battery half-bridge circuit, one end of the primary side is connected with one endpoint of a preset endpoint set, and the preset endpoint set comprises the midpoint of the second battery half-bridge circuit, the anode of a direct current bus, the cathode of the direct current bus, an internal level point of the battery, a positive bus capacitor voltage-dividing point, the midpoint of a direct current bus capacitor and a second battery half bridge;
the three-phase motor is respectively connected with the other end of the primary side and the three-phase inverter, and the three-phase motor is connected with the transformer through the heating relay.
In the implementation process, under the condition that the battery is required to be heated, the heating relay is closed, and no matter the vehicle is in a parking state or a running state, the three-phase current of the three-phase motor is controlled through PWM modulation of the three-phase inverter, so that the three-phase motor generates corresponding torque (in the running state, the vehicle is driven to run, and in the static state, zero torque is output); the PWM modulation of the three-phase inverter can generate common-mode voltage on the three-phase motor, the common-mode voltage acts on the transformer, alternating current is generated on the secondary side of the transformer, the alternating current flows through the internal resistance of each sub-battery in the battery pack, and the batteries are heated and heated, so that the performance of the batteries in a low-temperature environment is improved, and the cruising ability and the dynamic property of a vehicle are improved; therefore, the battery heating circuit can achieve the technical effects of less component heating, feasible vehicle state heating and small influence on the dynamic property of the motor when the battery is heated.
Further, the three-phase inverter comprises three power switch tube assemblies, one end of each power switch tube assembly is connected with one end of the first battery half-bridge circuit, and the other end of each power switch tube assembly is connected with the other end of the second battery half-bridge circuit.
Further, the power switch tube assembly comprises two power switch tubes, and the two power switch tubes are connected in series.
Further, three phase motor is provided with three cables, three cables are connected respectively three power switch tube assembly.
Further, the battery heating circuit further comprises a capacitor, and the capacitor is connected with the heating relay in series.
Further, the battery heating circuit further comprises a first relay connected in series at one end of the first battery half-bridge circuit.
Further, the battery heating circuit further comprises a second relay connected in series to the other end of the first battery half-bridge circuit.
In the implementation process, the first relay and the second relay are respectively a positive relay and a negative relay of the battery pack.
Further, the three-phase motor is a star-connected three-phase motor.
Further, the three-phase motor is one of a permanent magnet synchronous motor, a brushless motor and an asynchronous motor.
In a second aspect, embodiments of the present application provide an electric vehicle comprising a transformer-based battery heating circuit according to any of the first aspects.
Additional features and advantages of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the above-described techniques.
In order to make the aforementioned objects, features and advantages of the present application more comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments of the present application will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and that those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.
Fig. 1a is a schematic circuit diagram of a first transformer-based battery heating circuit according to an embodiment of the present disclosure;
fig. 1b is a schematic circuit diagram of a second transformer-based battery heating circuit according to an embodiment of the present disclosure;
FIG. 1c is a schematic circuit diagram of a third transformer-based battery heating circuit according to an embodiment of the present disclosure;
FIG. 1d is a schematic circuit diagram of a fourth transformer-based battery heating circuit according to an embodiment of the present disclosure;
fig. 1e is a schematic circuit diagram of a fifth transformer-based battery heating circuit according to an embodiment of the present disclosure;
fig. 1f is a schematic circuit diagram of a sixth transformer-based battery heating circuit according to an embodiment of the present disclosure;
fig. 1g is a schematic circuit diagram of a seventh transformer-based battery heating circuit according to an embodiment of the present disclosure;
FIG. 2 is a simplified model schematic diagram of a transformer-based battery heating circuit according to an embodiment of the present application;
fig. 3 is a schematic circuit diagram of a battery heating circuit of a battery stack according to an embodiment of the present disclosure;
fig. 4 is a schematic circuit diagram of a battery heating circuit in which batteries are connected in series according to an embodiment of the present disclosure;
fig. 5 is a schematic circuit diagram of a first half-bridge of a battery cell provided in an embodiment of the present application;
fig. 6 is a schematic circuit diagram of a second half-bridge of a single battery according to an embodiment of the present application;
fig. 7 is a schematic circuit diagram of a primary side circuit connected to one phase of a motor according to an embodiment of the present disclosure.
Detailed Description
The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present application, the terms "first", "second", and the like are used only for distinguishing the description, and are not to be construed as indicating or implying relative importance.
The embodiment of the application provides a transformer-based battery heating circuit and an electric vehicle, which can be applied to a battery heating process; under the condition that the battery is required to be heated, the heating relay is closed, and no matter the vehicle is in a parking state or a running state, the three-phase current of the three-phase motor is controlled through the PWM modulation of the three-phase inverter, so that the three-phase motor generates corresponding torque (in a driving state, the vehicle is driven to run, and in a vehicle static state, zero torque is output); the PWM modulation of the three-phase inverter can generate common-mode voltage on the three-phase motor, the common-mode voltage acts on the transformer, alternating current is generated on the secondary side of the transformer, the alternating current flows through the internal resistance of each sub-battery in the battery pack, and the batteries heat to raise the temperature, so that the performance of the batteries in a low-temperature environment is improved, and the cruising ability and the dynamic property of a vehicle are improved; therefore, the battery heating circuit can achieve the technical effects of less component heating, feasible vehicle state heating and small influence on the dynamic property of the motor when the battery is heated.
Referring to fig. 1a, fig. 1a is a schematic circuit diagram of a first transformer-based battery heating circuit according to an embodiment of the present disclosure, where the transformer-based battery heating circuit includes a battery pack 100, a transformer 200, a three-phase inverter 300, a heating relay Ka, and a three-phase motor 400.
Illustratively, the battery pack 100 includes a first sub-battery U1, a second sub-battery U2, a third sub-battery U3, and a fourth sub-battery U4, wherein the first sub-battery U1 and the second sub-battery U2 are connected in series to form a first battery half-bridge circuit, the third sub-battery U3 and the fourth sub-battery U4 are connected in series to form a second battery half-bridge circuit, and the first battery half-bridge circuit and the second battery half-bridge circuit are connected in parallel.
In some embodiments, the first sub-battery U1 and the second sub-battery U2 are symmetrical, and the third sub-battery U3 and the fourth sub-battery U4 are symmetrical; the voltage of the first sub-battery U1 is the same as that of the third sub-battery U3, and the voltage of the second sub-battery U2 is the same as that of the fourth sub-battery U4. The first sub-battery U1, the second sub-battery U2, the third sub-battery U3 and the fourth sub-battery U4 are respectively connected in series to form two half-bridge circuits, and then the two half-bridge circuits are connected in parallel to form a full-bridge.
Optionally, the capacities of the first sub-battery U1 and the third sub-battery U3 are different, and the capacities of the second sub-battery U2 and the fourth sub-battery U4 are different, so as to keep the temperature rise consistent.
Illustratively, the transformer 200 is provided with a primary side and a secondary side, two ends of the secondary side are respectively connected to a midpoint of the first battery half-bridge circuit and a midpoint of the second battery half-bridge circuit, one end of the primary side is connected to one of endpoints of a preset endpoint set, and the preset endpoint set comprises the midpoint of the second battery half-bridge circuit, a positive electrode of the dc bus, a negative electrode of the dc bus, an internal level point of the battery, a positive/negative bus capacitance voltage-dividing point, and a midpoint of the dc bus capacitance, namely the second battery half-bridge.
Illustratively, in the embodiment shown in fig. 1a, one end of the primary side is connected to the midpoint of the second battery half-bridge circuit; the midpoint of the first battery half-bridge circuit and the midpoint of the second battery half-bridge circuit are connected by a secondary side of a transformer 200; the primary side of the transformer 200 is also connected to the midpoint of the second battery half-bridge circuit, i.e. this end is therefore also connected to the synonym terminal of the secondary side. The transformation ratio of the transformer is designed according to the voltage of the battery, the internal resistance of the battery and the heating power requirement of the battery.
A Transformer (Transformer) is an apparatus for changing an alternating voltage by using the principle of electromagnetic induction, and main components are a primary coil, a secondary coil, and an iron core (magnetic core), for example. The main functions are as follows: voltage transformation, current transformation, impedance transformation, isolation, and the like. According to the application, the method can be divided into: power transformers and special transformers (furnace transformers, rectification transformers, power frequency test transformers, voltage regulators, mining transformers, audio transformers, intermediate frequency transformers, high frequency transformers, impact transformers, transformers for instruments, electronic transformers, reactors, mutual inductors, etc.). The primary side of the transformer 200 is an input side of the voltage, and the secondary side is an output side of the voltage converted by the transformer.
Illustratively, the three-phase motor 400 is connected to the other end of the primary side of the transformer 200 and the three-phase inverter 300, respectively, and the three-phase motor 400 is connected to the transformer 200 through a heating relay Ka.
Illustratively, by the heating relay Ka, on one hand, the circuit can be cut off for protection in a vehicle fault state, and on the other hand, the circuit can be cut off to stop the battery heating when the battery has no heating requirement.
In the case that the battery heating is required, the heating relay Ka is closed, and the three-phase current of the three-phase motor is controlled by PWM modulation of the three-phase inverter 300 no matter the vehicle is in a stopped state or in an operating state, so that the three-phase motor 400 generates a corresponding torque (in a driving state, the vehicle is driven to operate; in a vehicle stationary state, zero torque is output); the PWM modulation of the three-phase inverter 300 generates a common mode voltage at the three-phase motor 400, the common mode voltage acts on the transformer, and an alternating current is generated at the secondary side of the transformer, the alternating current flows through the internal resistance of each sub-battery in the battery pack 100, and the battery is heated by the internal resistance, so that the performance of the battery in a low-temperature environment is improved, and the cruising ability and the dynamic property of the vehicle are improved; therefore, the battery heating circuit can achieve the technical effects of less component heating, feasible vehicle state heating and small influence on the dynamic property of the motor when the battery is heated.
Illustratively, pulse Width Modulation (PWM) is an analog control method, and modulates the bias of the base of a transistor or the gate of a field effect transistor according to the change of a corresponding load to change the conduction time of the transistor or the field effect transistor, so as to change the output of a switching voltage-stabilized power supply. This way the output voltage of the power supply can be kept constant when the operating conditions change, which is a very effective technique for controlling an analog circuit by means of the digital signal of the microprocessor. Are widely used in many fields ranging from measurement, communication to power control and conversion.
In some embodiments, the three-phase inverter 300 may be controlled using SPWM (sinusoidal PWM modulation), SVPWM (space vector PWM modulation), or other modulation methods, such as DPWM (discontinuous PWM modulation); it should be noted that the PWM modulation scheme of the three-phase inverter 300 is only exemplary and not limiting.
Illustratively, the three-phase inverter 300 includes three power switch tube assemblies, one end of which is connected to one end of the first battery half-bridge circuit and the other end of which is connected to the other end of the second battery half-bridge circuit.
Illustratively, the power switch tube assembly includes two power switch tubes, the two power switch tubes being connected in series.
Illustratively, the three power switching tube assemblies include 6 power switching tubes Q1-Q6, i.e., 6 semiconductor power switching tubes of the three-phase inverter 300 that drive the three-phase motor 400 to operate.
In some embodiments, the power switch tube of the power switch tube assembly may be a semiconductor power switch device such as a field effect transistor or an insulated gate bipolar transistor.
Illustratively, the three-phase motor is provided with three cables which are respectively connected with three power switch tube assemblies.
Illustratively, the battery heating circuit further comprises a capacitor, and the capacitor is connected with the heating relay in series.
Illustratively, the transformer 200 is connected to the three-phase motor 400 through a capacitor Cn, a heating relay Ka. The capacitor Cn functions to isolate dc current to prevent the transformer 200 from magnetic bias saturation, and to resonate with common mode inductance of the three-phase motor 400 and leakage inductance of the transformer 200.
It should be noted that, when the primary side coil of the transformer, the capacitor Cn (i.e. the resonant capacitor) and the heating relay Ka are connected in series, their relative sequence does not affect the circuit, and all the sequenced circuits are equivalent when the primary side coil, the capacitor Cn and the heating relay Ka are connected in series.
In some embodiments, the transformer 200 is connected to the star-connected neutral point of the three-phase motor 400 by a capacitor Cn and a heating relay Ka.
Illustratively, the battery heating circuit further comprises a first relay K1, and the first relay K1 is connected in series with one end of the first battery half-bridge circuit.
The battery heating circuit further comprises a second relay K2, the second relay K2 being connected in series to the other end of the first battery half-bridge circuit.
Illustratively, the first relay K1 and the second relay K2 are a positive relay and a negative relay of the battery pack 100, respectively.
Illustratively, the three-phase motor 400 is a star-connected three-phase motor.
Illustratively, the three-phase inverter 300 controls the three-phase currents of the three-phase motor 400 during the PWM modulation, thereby allowing the three-phase motor 400 to generate the torque required by the vehicle. These PWM modulations generate a high frequency common mode voltage at the star connected neutral point of the three-phase motor 400, the main frequency component of which is the switching frequency of the three-phase inverter bridge (i.e., the three-phase inverter 300).
Illustratively, the three-phase motor is one of a permanent magnet synchronous motor, a brushless motor, and an asynchronous motor.
Illustratively, the embodiment of the application provides an electric vehicle, and the electric vehicle comprises a battery heating circuit based on a transformer shown in fig. 1 a.
For example, in the battery heating circuit provided in the embodiment of the present application, one end of the "primary circuit" (i.e., the primary coil + the capacitor Cn + the heating relay Ka) is connected to the neutral point of the motor, which is an alternative connection manner; in some embodiments, where the battery heating circuit has a coupling capacitor, one end of the primary circuit may be connected in addition to the midpoint of the battery bridge, as follows.
Referring to fig. 1b, fig. 1b is a schematic circuit diagram of a second transformer-based battery heating circuit according to an embodiment of the present disclosure; as shown in fig. 1b, one end of the primary side circuit is connected to the positive electrode of the dc bus; alternatively, one end of the primary side circuit can be connected to the left end or the right end of K1, which is not limited herein.
Referring to fig. 1c, fig. 1c is a schematic circuit diagram of a third transformer-based battery heating circuit according to an embodiment of the present disclosure; as shown in fig. 1c, one end of the primary side circuit is connected to the negative electrode of the dc bus; in principle, the connection can be made at the left end or the right end of K2, and is not limited herein.
Referring to fig. 1d, fig. 1d is a schematic circuit diagram of a fourth transformer-based battery heating circuit according to an embodiment of the present disclosure; as shown in fig. 1d, one end of the primary circuit is connected to the internal level point of the battery, which may be any level point inside the battery, not necessarily an intermediate point.
Referring to fig. 1e, fig. 1e is a schematic circuit diagram of a fifth transformer-based battery heating circuit according to an embodiment of the present disclosure; as shown in fig. 1e, the capacitor Cn becomes a "three-terminal capacitor" (divided into a capacitor Cn1 and a capacitor Cn 2), two ends of the capacitor Cn are connected across positive and negative buses (i.e., the positive and negative buses divide voltage by capacitors), and a central point is connected to a primary side circuit (at this time, the primary side circuit = the heating relay Ka + the primary side coil).
For example, the connection shown in fig. 1e has the following advantages compared with the connection shown in fig. 1a to 1 d: after the circuit is powered on (K1 and K2 are closed), the initial voltage of the capacitor Cn1 and the capacitor Cn2 has almost the same difference with the voltage during stable operation, when the circuit starts to heat, the transient resonance such as the voltage of the capacitor Cn1 and the capacitor Cn2, the current flowing through the primary side and the like is less in the process from the start of operation to the reaching of the steady resonance, and the transient maximum voltage and the maximum current on components such as a transformer and the capacitor Cn (= Cn1+ Cn 2) and the like are favorably reduced, so that the specification requirements on the components are favorably reduced, and the cost is reduced.
For example, in the connection manner shown in fig. 1a to 1d, the initial voltage on the capacitor Cn after power-on is generally zero, and when the capacitor Cn is heated by resonance in a steady state, the voltage is about half of the dc bus voltage, so a transition process is performed from the initial state to the steady state, and during this process, an instantaneous large value of the voltage across the capacitor Cn and the primary side current exists, and a large specification is required for the component, which may result in an increase in cost.
Referring to fig. 1f, fig. 1f is a schematic circuit diagram of a sixth transformer-based battery heating circuit according to an embodiment of the present disclosure; as shown in fig. 1f, the primary circuit is connected to the midpoint of the dc bus capacitor Cdc, and the dc bus capacitor Cdc is divided into two parts (capacitor Cdc1 and capacitor Cdc 2) and divided into two upper and lower parts with equal capacities; this connection method also has the advantage of a small transient process, but the dc bus capacitor Cdc becomes complex and costly.
Referring to fig. 1g, fig. 1g is a schematic circuit diagram of a seventh transformer-based battery heating circuit according to an embodiment of the present disclosure; as shown in fig. 1g, on the basis of fig. 1f, the capacitor Cn is omitted, and the dc bus capacitor has both resonance and dc blocking functions; this connected mode need compromise the normal direct current bus steady voltage effect of direct current bus electric capacity Cdc, the resonance blocking effect when giving consideration to the heating again.
Referring to fig. 2, fig. 2 is a simplified model schematic diagram of a transformer-based battery heating circuit according to an embodiment of the present disclosure.
Illustratively, if the transformer 200 transformation ratio is large enough such that the primary current of the transformer 200 is negligible compared to the secondary current, the circuit of fig. 1a can be simplified to the circuit model shown in fig. 2.
Illustratively, ucom is the common mode voltage of the three-phase motor 400 with respect to the midpoint of the series battery pack 100; ls is a common mode inductor, which comprises the common mode inductor of the three-phase motor 400, the leakage inductor of the transformer 200 and the stray inductor of the cable; lm is the excitation inductance of the transformer 200; r is the entire internal resistance of the battery pack 100.
Illustratively, at the time of vehicle stop, the Ucom is a square wave with a frequency equal to the switching frequency of the three-phase inverter bridge, whether using SPWM modulation or SVPWM modulation. In the case of vehicle operation, the Ucom waveform deviates from a square wave, but the frequency of the dominant component is still the switching frequency of the three-phase inverter bridge. Therefore, to simplify the analysis process, ucom can be assumed to be a sine wave with a frequency equal to the frequency of the three-phase inverter bridge.
Wherein the function eta (f) s /f ac M) is the adjustment coefficient of the common mode voltage amplitude under different working conditions, which is the current frequency f of the motor ac And the voltage utilization m of the three-phase inverter 300.
When the vehicle is stopped and the three-phase motor 400 is stationary, under the condition of adopting SVPWM modulation or SPWM modulation, there are:
the effective value is:
according to the circuit shown in fig. 2, assuming that Lm is much larger than Ls and can be ignored, the effective value of the current on the internal resistance R can be calculated as:
wherein the transformation ratio n = Np/Ns, f of the transformer 200 r Is the resonant frequency of Ls and Cn, Z r For the resonant impedances, they are related to Ls, cn as follows:
the current flowing through the neutral point of the motor is:
the following formula 4 and 7 can be obtained:
exemplarily, an example of an operation mode of the battery heating circuit provided in the embodiment of the present application is as follows:
ls is basically controlled by the common mode inductance of the three phase motor 400, the adjustable range is small, so the main adjustable quantities of the circuit are the capacity of Cn and the transformer transformation ratio n.
Cn is selected such that f s ≈f r Then, there are:
on the basis, n is selected according to the required heating power P of the battery, namely:
at this time, the following steps are provided:
in this mode, as can be seen from equation 4, by adjusting the switching frequency f s The heating power can be adjusted within a certain range. When battery heating is not required at all, the heating relay Ka is switched.
The battery heating circuit based on transformer that this application example provided, the common mode current that flows through the motor during operation is little, consequently possesses following advantage: a) When the battery is heated, the components such as the three-phase motor 400 and the like generate less heat; b) When the battery is heated in a running state, the influence on the dynamic property is small.
Illustratively, since the battery heating circuit operates in a resonance state, and since the internal resistance of the battery with small resistance of the secondary side is converted into a larger resistance of the primary side through the conversion of the transformer 200, the power factor of the circuit is high, the current flowing through the neutral point of the motor is small, and the heat generation of the motor is small. When the motor is heated in the running state, the current flowing through the middle point is smaller, and the current distributed to the three phases of the motor is only 1/3 of the current of the middle point, so that only little current capacity is reserved for heating the battery by the three phases of the motor, and most of the residual capacity can be used for driving the motor, thereby having little influence on the output capacity of the motor in the running state.
In some implementation scenarios, for a certain electric drive system, the battery voltage is 400V, the whole-pack ohmic internal resistance is 20m Ω, the common-mode inductance of the motor is 15uH, the rated switching frequency of the inverter is 10kHz, the rated current of each phase of three phases of the inverter is 300A effective value, the short-time peak current is 530A effective value, and the target battery heating power is 20kW. The transformer transformation ratio is selected to be 9,cn =16.9uf, where the effective value of the neutral current is only 111A, and after being equally distributed to the three phases, each phase has only 37A, which is much smaller than the rated current and the peak current. However, at this time, the secondary side of the transformer has a heating current of 1000A, and the battery can obtain a heating power of 20kW.
Illustratively, the resonant frequency f r Can be used forThe switching frequency is chosen to be much higher than normal, for example 20kHz, and is adjusted when heating is required s To near f r . The low temperature when heating is required allows the inverter switching frequency to be increased, thereby increasing the heat generated by the inverter to heat the cold zone fluid.
Alternatively, the connection manner of the transformer 200 and the battery pack 100 may be varied, and the number of the transformer 200 and the battery pack 100 may be plural, which is only an example of a combination of two transformers. For example, the transformer 200 may be implemented by connecting the primary sides in parallel, in series, and connecting the secondary sides in parallel in series, where a plurality of secondary sides are respectively corresponding to a "battery full bridge", a plurality of battery full bridges are connected in series, in parallel, and the like, and the combination of the above may be various.
Referring to fig. 3 and 4, fig. 3 is a schematic circuit diagram of a battery heating circuit of a battery stack according to an embodiment of the present disclosure, and fig. 4 is a schematic circuit diagram of a battery heating circuit of a battery stack according to an embodiment of the present disclosure; the battery pack 100 includes eight sub-batteries U1 to U8 and two transformers 200.
In some embodiments, the battery is heated, and the cold zone liquid can be heated by heating of the battery, and then the member cabin is heated by means of a heat pump or the like.
In some embodiments, high-frequency alternating current is injected into the battery, which can be used for measuring the internal impedance of the battery, so as to know the temperature and the health condition of the battery.
Referring to fig. 5, fig. 5 is a schematic circuit diagram of a half bridge of a first battery cell provided in an embodiment of the present application.
In some implementation scenarios, if the battery pack cannot be split into two half-bridges, one half-bridge may be implemented by a set of capacitors, as shown in fig. 5, and the capacitor Cb1 and the capacitor Cb2 are used to form the half-bridge.
Referring to fig. 6, fig. 6 is a schematic circuit diagram of a second half-bridge of a single cell according to an embodiment of the present disclosure.
Optionally, the dc bus capacitor Cdc of the three-phase inverter of the motor may be split into two parts Cdc1 and Cdc2 to form a capacitor half bridge.
Referring to fig. 7, fig. 7 is a schematic circuit diagram of a primary side circuit connected to one phase of a motor according to an embodiment of the present disclosure.
For example, in all the connection modes shown in fig. 1a to 6, the other end of the primary circuit may be directly connected to one phase of the motor instead of the neutral point of the motor, as shown in fig. 7. The principle is basically the same, and only the primary side of the transformer is changed into the voltage of one phase of three phases from the common-mode voltage of the neutral point of the motor.
It is to be noted that in the circuits shown in fig. 1a to 7, the three-phase inverter 300 by default contains a dc bus capacitance Cdc, even if not identified in the circuit diagram.
In the several embodiments provided in the present application, it should be understood that each functional module in each embodiment may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.
The above description is only an example of the present application and is not intended to limit the scope of the present application, and various modifications and changes may be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of another identical element in a process, method, article, or apparatus that comprises the element.
Claims (10)
1. A battery heating circuit based on a transformer is characterized by comprising a battery pack, the transformer, a three-phase inverter, a heating relay and a three-phase motor;
the battery pack comprises a first sub battery, a second sub battery, a third sub battery and a fourth sub battery, wherein the first sub battery and the second sub battery are connected in series to form a first battery half-bridge circuit, the third sub battery and the fourth sub battery are connected in series to form a second battery half-bridge circuit, and the first battery half-bridge circuit and the second battery half-bridge circuit are connected in parallel;
the transformer is provided with a primary side and a secondary side, two ends of the secondary side are respectively connected with the midpoint of the first battery half-bridge circuit and the midpoint of the second battery half-bridge circuit, one end of the primary side is connected with one endpoint of a preset endpoint set, and the preset endpoint set comprises the midpoint of the second battery half-bridge circuit, the anode of a direct current bus, the cathode of the direct current bus, a battery internal level point, positive and negative bus capacitance voltage-dividing points and the midpoint of a direct current bus capacitance;
the three-phase motor is respectively connected with the other end of the primary side and the three-phase inverter, and the three-phase motor is connected with the transformer through the heating relay.
2. The transformer-based battery heating circuit of claim 1, wherein the three-phase inverter comprises three power switching tube assemblies, one end of the power switching tube assemblies being connected to one end of the first battery half-bridge circuit, the other end of the power switching tube assemblies being connected to the other end of the second battery half-bridge circuit.
3. The transformer-based battery heating circuit of claim 2, wherein the power switching tube assembly comprises two power switching tubes, the two power switching tubes being connected in series.
4. The transformer-based battery heating circuit of claim 2, wherein the three-phase motor is provided with three electrical cables that connect to the three power switching tube assemblies, respectively.
5. The transformer-based battery heating circuit of claim 1, further comprising a capacitor in series with the heating relay.
6. The transformer-based battery heating circuit of claim 1, further comprising a first relay connected in series at one end of the first battery half-bridge circuit.
7. The transformer-based battery heating circuit of claim 6, further comprising a second relay connected in series with the other end of the first battery half-bridge circuit.
8. The transformer-based battery heating circuit of claim 1, wherein the three-phase motor is a star-connected three-phase motor.
9. The transformer-based battery heating circuit of claim 1 or 8, wherein the three-phase motor is one of a permanent magnet synchronous motor, a brushless motor, and an asynchronous motor.
10. An electric vehicle, characterized in that it comprises a transformer based battery heating circuit according to any of claims 1 to 9.
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| CN202222837866.0U CN218228714U (en) | 2022-10-26 | 2022-10-26 | Battery heating circuit and electric vehicle based on transformer |
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| CN202222837866.0U CN218228714U (en) | 2022-10-26 | 2022-10-26 | Battery heating circuit and electric vehicle based on transformer |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102023108118B3 (en) | 2023-03-30 | 2024-05-29 | Rainer Marquardt | Device and method for heating traction batteries |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102023108118B3 (en) | 2023-03-30 | 2024-05-29 | Rainer Marquardt | Device and method for heating traction batteries |
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