A low-temperature preheating circuit topology system of a lithium ion battery

Abstract

The application discloses a low-temperature preheating circuit topology system of a lithium ion battery, which comprises a three-phase inverter, a permanent magnet synchronous motor, a power battery pack, a two-phase bridge and a controller; a positive electrode of the power battery pack is connected with one end of the two-phase bridge, and a negative electrode of the power battery pack is connected with one end of the three-phase inverter; the other two ends of the two-phase bridge are connected with the other two ends of the three-phase inverter respectively; three phases of the permanent magnet synchronous motor are connected with the three-phase inverter and the controller respectively; and the controller is connected with the two-phase bridge and the three-phase inverter through driving signals respectively. The application does not need to use an additional power supply, does not generate motor vibration noise, and has important engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery modeling and management applications, specifically relating to a low-temperature preheating circuit topology system for lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries, as the power source for electric vehicles, feature high energy density, high charging rate, and good cycle life. However, their performance is significantly affected by low temperatures, and directly charging lithium-ion batteries in cold environments poses certain safety hazards. Therefore, specific strategies must be employed to preheat lithium-ion batteries before charging.

[0003] Currently, common methods for heating power batteries at low temperatures are mainly divided into external heating and internal heating.

[0004] External heating is simple in principle and easy to implement, such as using hot air or hot mineral oil as a medium to heat the battery or covering the battery surface with a metal film. However, the battery is prone to uneven heating during the heating process, and there is a lot of loss and low energy utilization.

[0005] Internal heating methods generate heat from the battery's internal resistance, resulting in higher energy efficiency and a more uniform temperature distribution across the battery pack. Methods include applying a current of a specific amplitude and frequency to the battery or using an external switching transistor to generate a large current through a momentary short circuit. However, most internal heating methods require additional power supplies or modifications to the battery's structure, making them complex and increasing the size of the power supply system, hindering large-scale modifications to widely used lithium-ion batteries. Another method involves changing the series-parallel connection of the battery pack, using an onboard inverter and motor to create a current path for heating the battery. This method, however, generates vibration and noise from the motor. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a low-temperature preheating circuit topology system for lithium-ion batteries that requires no additional power supply and does not generate motor vibration noise, thus possessing significant engineering application value.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] A low-temperature preheating circuit topology system for a lithium-ion battery includes: a three-phase inverter, a permanent magnet synchronous motor, a power battery pack, a two-phase bridge, and a controller.

[0009] The positive terminal of the power battery pack is connected to one end of the two-phase bridge, and the negative terminal of the power battery pack is connected to one end of the three-phase inverter.

[0010] The other two ends of the two-phase bridge are respectively connected to the other two ends of the three-phase inverter;

[0011] The three phases of the permanent magnet synchronous motor are respectively connected to the three-phase inverter and the controller;

[0012] The controller is connected to the two-phase bridge and the three-phase inverter respectively via drive signals.

[0013] Preferably, the power battery pack includes two groups, Bat1 and Bat2, which are connected in parallel with each other, have the same number of cells, and are connected in the same way.

[0014] Preferably, the three-phase inverter is composed of switching transistors S1, S2, S3, S4, S5, and S6, wherein the upper bridge arm switching transistors of phases A, B, and C are S1, S3, and S5, respectively, and the lower bridge arm switching transistors of phases A, B, and C are S2, S4, and S6, respectively; at the same time, each switching transistor is connected in reverse parallel with a diode, namely D1, D2, D3, D4, D5, and D6, with the positive terminal of the diode connected to the source (S) terminal of the switching transistor and the negative terminal of the diode connected to the drain (D) terminal of the switching transistor;

[0015] The S poles of the upper bridge arm switching transistors S1, S3, and S5 of phases A, B, and C are respectively connected to the three phases of the permanent magnet synchronous motor, and the connection between the D poles of the upper bridge arm switching transistors S1 and S3 of phases A and B is disconnected.

[0016] The negative terminals of both Bat1 and Bat2 are connected to the S terminal of the lower bridge arm switch transistor of the three-phase inverter.

[0017] Preferably, the two-phase bridge is a two-phase inverter circuit added between the power battery pack and the three-phase inverter, consisting of switching transistors S7, S8, S9, and S1. 10 The configuration is such that the drain (D) terminal of S8 is connected to the positive terminal of Bat1, and S... 10 The D terminal is connected to the positive terminal of Bat2, S8, S 10 The source (S) terminals of S7 and S9 are connected together to the drain (D) terminal of the upper bridge arm S1 of phase A of the three-phase inverter; the drain (D) terminals of S7 and S9 are connected together to the drain (D) terminals of the upper bridge arms S3 and S5 of phases B and C of the three-phase inverter; simultaneously, each switching transistor is connected in reverse parallel with a diode, namely D7, D8, D9, and D1. 10 The positive terminal of the diode is connected to the source (S) terminal of the switching transistor, and the negative terminal is connected to the drain (D) terminal of the switching transistor.

[0018] Preferably, the controller includes: a current decoupling unit, a PI controller, a first drive unit, and a second drive unit;

[0019] The current decoupling unit is connected to the PI controller; the PI controller is connected to the first drive unit.

[0020] Preferably, the SVPWM wave emitted by the first driving unit is connected to the switching transistors S1, S2, S3, S4, S5, and S6 via the driving circuit.

[0021] Preferably, the current loop generated by the current decoupling unit controls the current of the permanent magnet synchronous motor to be a DC current of a predetermined amplitude.

[0022] Preferably, the PWM wave with a constant duty cycle of 50% emitted by the second driving unit controls each switch of the two-phase bridge. In the first half-cycle, switches S8 and S9 are simultaneously turned on, while switches S7 and S8 are turned on. 10 Simultaneous closure is called state 1; in the second half of the cycle, switching transistors S7 and S8... 10 When both are turned on, switches S8 and S9 are closed simultaneously, which is called state 2. The two states alternate, with a frequency f = 1 / T.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) It can generate square wave heating current on batteries Bat1 and Bat2, and its amplitude and frequency are individually adjustable. The lower limit of the amplitude is zero, and the upper limit depends on the rated current of the motor; the frequency f is adjustable in the range of 1 to 1 kHz. It can heat the battery from -20°C to 0°C within 20 minutes.

[0025] (2) It does not produce noise. Attached Figure Description

[0026] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is the schematic diagram of the main circuit of an existing electric vehicle drive circuit.

[0028] Figure 2 The above are the schematic diagram and control block diagram of the improved driving circuit main circuit in the embodiments of the present invention.

[0029] Figure 3 This is a schematic diagram of the three-phase current of the motor in an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of the d-axis and q-axis currents of the motor in an embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of the heating current flowing through two sets of batteries in an embodiment of the present invention;

[0032] Figure 6This is a schematic diagram of the positive half-cycle current path in an embodiment of the present invention, showing the charging of the Bat2 battery pack to the Bat1 battery pack.

[0033] Figure 7 This is a schematic diagram of the negative half-cycle current path in an embodiment of the present invention, showing the charging of the Bat1 battery pack to the Bat2 battery pack. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1

[0037] like Figure 1 The diagram shown is a schematic of the main circuit of the drive circuit used in an electric vehicle, including a three-phase inverter composed of switching transistors S1, S2, S3, S4, S5, and S6. The source (S) terminals of the upper bridge arm switching transistors S1, S3, and S5 in phases A, B, and C are respectively connected to the three phases of the permanent magnet synchronous motor. The positive and negative terminals of the power battery pack are respectively connected to the drain (D) terminal of the upper bridge arm transistor and the source (S) terminal of the lower bridge arm transistor in the inverter. The topology proposed in this invention makes two changes to this:

[0038] like Figure 2 As shown, the present invention provides a low-temperature preheating circuit topology system for lithium-ion batteries, including: a three-phase inverter, a permanent magnet synchronous motor, a power battery pack, a two-phase bridge, and a controller;

[0039] The positive terminal of the power battery pack is connected to one end of the two-phase bridge, and the negative terminal of the power battery pack is connected to one end of the three-phase inverter.

[0040] The other two ends of the two-phase bridge are connected to the other two ends of the three-phase inverter, respectively.

[0041] The three phases of the permanent magnet synchronous motor are connected to a three-phase inverter and a controller, respectively.

[0042] The controller is connected to the two-phase bridge and the three-phase inverter respectively via drive signals.

[0043] In this embodiment, the battery pack connection method is changed. The power battery pack in the original topology can be split into two groups that are connected in parallel, with an equal number of cells and the same connection method, namely Bat1 and Bat2.

[0044] In this embodiment, the three-phase inverter consists of switching transistors S1, S2, S3, S4, S5, and S6. The upper bridge arm switching transistors for phases A, B, and C are S1, S3, and S5, respectively, and the lower bridge arm switching transistors for phases A, B, and C are S2, S4, and S6, respectively. Simultaneously, each switching transistor is connected in reverse parallel with a diode, numbered D1, D2, D3, D4, D5, and D6, for freewheeling. The anode of the diode is connected to the source (S) terminal of the switching transistor, and the cathode of the diode is connected to the drain (D) terminal of the switching transistor.

[0045] The S poles of the upper bridge arm switching transistors S1, S3, and S5 in phases A, B, and C are respectively connected to the three phases of the permanent magnet synchronous motor, and the connection between the D poles of the upper bridge arm switching transistors S1 and S3 in phases A and B is disconnected.

[0046] The negative terminals of both Bat1 and Bat2 are connected to the S terminal of the lower arm switch transistor of the three-phase inverter.

[0047] In this embodiment, the two-phase bridge is a two-phase inverter circuit added between the power battery pack and the three-phase inverter, consisting of switching transistors S7, S8, S9, and S1. 10 The configuration is such that the drain (D) terminal of S8 is connected to the positive terminal of Bat1, and S... 10 The drain terminal is connected to the positive terminal of Bat2, S8, S 10 The source (S) terminals of the transistors S7 and S9 are connected together to the drain (D) terminal of the upper bridge arm S1 of phase A of the three-phase inverter; the drain terminals of S7 and S9 are connected together to the drain terminals of the upper bridge arms S3 and S5 of phases B and C of the three-phase inverter; simultaneously, each switching transistor is connected in reverse parallel with a diode, namely D7, D8, D9, and D1. 10 It is used for freewheeling. The positive terminal of the diode is connected to the source (S) terminal of the switching transistor, and the negative terminal is connected to the drain (D) terminal of the switching transistor.

[0048] In this embodiment, the controller includes: a current decoupling unit, a PI controller, a first drive unit, and a second drive unit;

[0049] The current decoupling unit is connected to the PI controller; the PI controller is connected to the first drive unit.

[0050] The SVPWM wave emitted by the first driving unit is connected to the switching transistors S1, S2, S3, S4, S5, and S6 through the driving circuit.

[0051] The current loop generated by the current decoupling unit controls the current of the permanent magnet synchronous motor to be a DC current of a predetermined amplitude.

[0052] The second drive unit generates a PWM wave with a constant duty cycle of 50% to control the switching transistors of the two-phase bridge. In the first half of the cycle, switching transistors S8 and S9 are simultaneously turned on, while switching transistors S7 and S8 are turned on. 10 Simultaneous closure is called state 1; in the second half of the cycle, switching transistors S7 and S8... 10When both are turned on, switches S8 and S9 are closed simultaneously, which is called state 2. The two states alternate, with a frequency f = 1 / T.

[0053] In this embodiment, the stator current i of the motor is transformed by coordinate transformation. A i B i C Convert to i d i q The relationship is as shown in formula (1), i d i q These represent the excitation component and the torque component, respectively.

[0054]

[0055] In the formula, θ is the electrical angle. During the preheating process of the battery pack, the motor remains stationary, so the electrical angle θ is a constant value, which can be set to 0 degrees. Substituting θ = 0 into formula (1) yields...

[0056] i d =i A (2)

[0057] Controlling the excitation component i d This value is constant, ensuring the stability of the stator flux linkage. The direction and amplitude remain unchanged, preventing rotor vibration and noise.

[0058] The functionality of this topology was verified in a simulation platform:

[0059] Figure 3 The three-phase current i of the motor A i B i C The currents in phases B and C are the same. Figure 4 For the d-axis and q-axis currents i of the motor d i q , where i q The value is approximately zero, ensuring that the motor does not generate electromagnetic torque and the vehicle remains stationary.

[0060] Figure 5 This represents the current flowing through the two battery packs. During the positive half-cycle, the Bat2 battery pack charges the Bat1 battery pack, and the current path is as follows: Figure 6 As shown, the two-phase bridge S8 and S9 are turned on (i.e., state 1); during the negative half-cycle, the Bat1 battery pack charges the Bat2 battery pack, and the current path is as follows. Figure 7 As shown, the two-phase bridge S7, S 10 On (i.e., state 2), and Figure 6 Compared to i A The direction remains unchanged. The current on the Bat1 and Bat2 battery packs is the heating current, and its amplitude and frequency can be adjusted independently by the three-phase inverter and the two-phase bridge.

[0061] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A low temperature preheat circuit topology system for a lithium ion battery, characterized by, include: Three-phase inverter, permanent magnet synchronous motor, power battery pack, two-phase bridge and controller; The positive terminal of the power battery pack is connected to one end of the two-phase bridge, and the negative terminal of the power battery pack is connected to one end of the three-phase inverter. The other two ends of the two-phase bridge are respectively connected to the other two ends of the three-phase inverter; The three phases of the permanent magnet synchronous motor are respectively connected to the three-phase inverter and the controller; The controller is connected to the two-phase bridge and the three-phase inverter respectively via drive signals; The power battery pack includes two groups connected in parallel, with an equal number of cells and the same connection method, namely Bat1 and Bat2. The three-phase inverter is composed of switching transistors S1, S2, S3, S4, S5, and S6. The upper bridge arm switching transistors for phases A, B, and C are S1, S3, and S5, respectively, and the lower bridge arm switching transistors for phases A, B, and C are S2, S4, and S6, respectively. At the same time, each switching transistor is connected in reverse parallel with a diode, namely D1, D2, D3, D4, D5, and D6. The positive terminal of the diode is connected to the source (S) terminal of the switching transistor, and the negative terminal of the diode is connected to the drain (D) terminal of the switching transistor. The S poles of the upper bridge arm switching transistors S1, S3, and S5 of phases A, B, and C are respectively connected to the three phases of the permanent magnet synchronous motor, and the connection between the D poles of the upper bridge arm switching transistors S1 and S3 of phases A and B is disconnected. The negative terminals of both Bat1 and Bat2 are connected to the S terminal of the lower bridge arm switch transistor of the three-phase inverter. The two-phase bridge is a two-phase inverter circuit added between the power battery pack and the three-phase inverter, consisting of switching transistors S7, S8, S9, and S10. The drain (D) of S8 is connected to the positive terminal of Bat1, and the drain (D) of S10 is connected to the positive terminal of Bat2. The source (S) terminals of S8 and S10 are connected together to the drain of the upper bridge arm S1 of phase A of the three-phase inverter. The drains of S7 and S9 are connected together to the drains of the upper bridge arms S3 and S5 of phases B and C of the three-phase inverter. At the same time, each switching transistor is connected in reverse parallel with a diode, namely D7, D8, D9, and D10, with the positive terminal of the diode connected to the source (S) terminal of the switching transistor and the negative terminal connected to the drain (D) terminal of the switching transistor.

2. The low temperature preheat circuit topology system for a lithium-ion battery of claim 1, wherein, The controller includes: a current decoupling unit, a PI controller, a first drive unit, and a second drive unit; The current decoupling unit is connected to the PI controller; the PI controller is connected to the first drive unit.

3. The low temperature preheat circuit topology system for a lithium-ion battery of claim 2, wherein, The SVPWM wave emitted by the first driving unit is connected to the switching transistors S1, S2, S3, S4, S5, and S6 respectively through the driving circuit.

4. The low temperature preheat circuit topology system for a lithium-ion battery of claim 2, wherein, The current loop generated by the current decoupling unit controls the current of the permanent magnet synchronous motor to be a DC current of a predetermined amplitude.

5. The low temperature preheat circuit topology system for a lithium-ion battery of claim 2, wherein, The duty ratio of the PWM wave emitted by the second driving unit is always 50%, which controls the switch tubes of the two-phase bridge. In the first half cycle, switch tubes S8 and S9 are turned on at the same time, switch tubes S7 and S 10 are turned off at the same time, which is called state 1; in the second half cycle, switch tubes S7 and S 10 are turned on at the same time, switch tubes S8 and S9 are turned off at the same time, which is called state 2, and the two states appear alternately with a frequency f = 1 / T.

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