A battery pack system and a control method thereof

Abstract

The application discloses a battery pack system and a control method thereof. The battery pack system comprises a DC / DC regulator, a direct current transformer DCX, a controller and a battery pack system. The input end of the DC / DC regulator is connected with the output end of the battery pack system, and the output end of the DC / DC regulator is connected with the input end of the direct current transformer DCX. The controller is connected with the DC / DC regulator and the direct current transformer DCX respectively. The controller is used for obtaining the current flowing through the inductor in the DC / DC regulator and the first voltage between the capacitors, thereby obtaining the corresponding power value. The controller is also used for obtaining the second voltage between the capacitors between the output ends of the DC / DC regulator. The controller is also used for outputting the signal for controlling the charging or discharging of the DC / DC regulator and the direct current transformer DCX based on the power value and the second voltage. The application can realize high efficiency and easy balancing, and meet the high flexibility configuration requirements of users.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of storage, in particular to a battery pack system and a control method thereof. BACKGROUND

[0002] With the wide use of lithium battery energy storage systems, battery packs are increasingly used as the heart of energy storage systems in various applications, such as electric vehicles, mobile energy storage, and household energy storage. As users demand more power from energy storage systems, the capacity of battery packs is also increasing, and the cost is decreasing. Due to the obvious efficiency advantage of high-voltage battery pack systems, high-voltage battery solutions are the first choice for large-capacity energy storage systems.

[0003] Currently, whether it is an electric vehicle energy storage or a household energy storage system, high-voltage battery packs use battery series to achieve high-voltage output of the battery pack. The most obvious disadvantage of this solution is that the higher the voltage of the battery pack, the more the number of series-connected batteries, and the worse the balance between the cells. The efficiency of the series system is low, and it cannot meet the flexible configuration requirements of different capacity systems.

[0004] In order to solve the balancing problem caused by battery pack series connection, some solutions propose to add an optimizer in each battery pack to adjust the output characteristics of the battery pack to optimize the SOC of the battery pack. This solution has made significant progress in terms of battery pack balancing capability and system efficiency. However, it lacks flexibility in meeting customers' different capacity configuration requirements and lacks compatibility for different capacity PCS. SUMMARY

[0005] In view of this, the present application provides a battery pack system and a control method thereof to solve the above technical problems.

[0006] The present application discloses a battery pack system, comprising a DC / DC regulator, a direct current transformer DCX, a controller and a battery pack system; wherein the input end of the DC / DC regulator is connected with the output end of the battery pack system, and the output end of the DC / DC regulator is connected with the input end of the direct current transformer DCX; the controller is connected with the DC / DC regulator and the direct current transformer DCX respectively;

[0007] The controller is used to obtain the current flowing through the inductor in the DC / DC regulator and the first voltage across the capacitor, thereby obtaining the corresponding power value;

[0008] The controller is also used to obtain the second voltage across the capacitor between the output ends of the DC / DC regulator;

[0009] The controller is further configured to output a signal for controlling the DC / DC regulator and the DC transformer DCX to charge or discharge based on the power value and the second voltage.

[0010] Further, the controller comprises a first difference device, a power regulator connected to the first difference device, a second difference device, a voltage regulator connected to the second difference device, a first comparator, a third difference device connected to the first comparator, a current regulator connected to the third difference device.

[0011] The first difference device is configured to subtract the power value from a reference power and input the difference to the power regulator.

[0012] The second difference device is configured to subtract the second voltage from a reference voltage and input the difference to the voltage regulator.

[0013] The first comparator is configured to compare the output of the power regulator and the voltage regulator and output the minimum value to the third difference device.

[0014] The third difference device is configured to subtract the output of the third difference device from a current in the DC / DC regulator and input the difference to the current regulator.

[0015] The current regulator is configured to output a control signal to control the conduction or closure of the fifth switch and the sixth switch in the DC / DC regulator and the first switch, the second switch, the third switch, and the fourth switch in the DC transformer DCX.

[0016] Further, the DC / DC regulator comprises a first capacitor, a current sensor, a first inductor, a fifth switch, a fifth diode, a sixth switch, a sixth diode, and a second capacitor.

[0017] The first capacitor is connected to one end of the first inductor through the current sensor, and the other end of the first inductor is connected to the input end of the fifth diode and the output end of the sixth diode, respectively.

[0018] The fifth diode and the sixth diode are connected in series, the fifth switch and the sixth switch are connected in parallel with the fifth diode and the sixth diode, respectively, and the second capacitor is connected to the output end of the fifth diode and the input end of the sixth diode, respectively.

[0019] Further, the DC transformer DCX comprises a first switch with anti-parallel first diode, a second switch with anti-parallel second diode, a third switch with anti-parallel third diode, and a fourth switch with anti-parallel fourth diode.

[0020] The direct current transformer DCX further comprises a transformer, a second inductor, a third capacitor, and a fourth capacitor;

[0021] One end of a primary winding of the transformer is connected with an input end of the first diode, another end of the primary winding of the transformer is connected with an input end of the second diode, one end of a secondary winding of the transformer is connected with one end of the second inductor, another end of the secondary winding of the transformer is connected with an input end of the fourth diode, another end of the second inductor is connected with an output end of the fourth diode and an input end of the third diode through the third capacitor, and the fourth capacitor is connected with an output end of the third diode and an input end of the fourth diode.

[0022] Further, the transformer is a high-frequency transformer.

[0023] The transformer comprises two primary windings and one secondary winding, an input end of the sixth diode is connected with a common end of the two primary windings of the transformer, and an output end of the fifth diode is connected with an output end of the first diode.

[0024] Further, the battery pack system comprises a battery pack, an isolation switch, a soft start switch, a resistor, and a BMS.

[0025] A positive electrode of the battery pack is connected with a common end of the isolation switch and the soft start switch through a fuse, and a negative electrode of the battery pack is connected with the DC / DC regulator.

[0026] The isolation switch and the soft start switch are connected in parallel, and are used for cutting off the connection between the battery cell and the load or the power supply, so as to protect the safety of the battery pack system; the soft start switch and the resistor are connected in series, and are used for slow starting of the output voltage of the battery pack system.

[0027] A common end of the resistor and the isolation switch is connected with the DC / DC regulator.

[0028] The BMS is used for sampling the voltage and current of each battery cell in the series-connected battery pack, sampling the temperature of each component in the battery pack system, and generating a driving signal of the isolation switch and the soft start switch.

[0029] Further, the battery pack comprises a plurality of battery units connected in series.

[0030] The application further discloses a control method of a battery pack system, which is applied to the battery pack system and comprises the following steps.

[0031] Step 1: obtaining a power value in the DC / DC regulator and a voltage value between the second capacitor.

[0032] Step 2: obtaining the control signal of the DC / DC regulator and the DC transformer DCX based on the power value, the voltage value across the second capacitor, and the reference power value and the reference voltage.

[0033] Further, the obtaining of the power value in the DC / DC regulator comprises:

[0034] The current value flowing through the first inductor and the voltage value across the first capacitor in the DC / DC regulator are obtained, and the corresponding power value is obtained;

[0035] The step 2 comprises:

[0036] Step 21: subtracting the power value from the reference power value and inputting the result into the power regulator; subtracting the voltage value across the capacitor from the reference voltage and inputting the result into the voltage regulator;

[0037] Step 22: obtaining the minimum value in the output results of the power regulator and the voltage regulator;

[0038] Step 23: subtracting the current value obtained from the DC / DC regulator from the minimum value and inputting the result into the current regulator;

[0039] Step 24: obtaining the output signal of the current regulator.

[0040] Further, the output signal in the step 24 is the control signal for turning on or closing the fifth switch and the sixth switch in the DC / DC regulator and the first switch, the second switch, the third switch and the fourth switch in the DC transformer DCX.

[0041] Due to the adoption of the above technical solutions, the application has the following advantages: the DC / DC regulator and the DC transformer DCX circuit and the corresponding control method are added to the traditional battery pack, the output voltage of the battery pack and the flexible configuration of the cell capacity and the number of series are realized, the high efficiency of the battery pack system is maintained, the control system is simple and low in cost, the requirement for the PCS interface is greatly reduced, the demand for directly parallel connection of multiple battery packs and direct hanging of the PCS bus is met, and great convenience is provided for the expansion of the energy storage system. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the embodiments of the application, and other drawings can be obtained by those skilled in the art based on these drawings.

[0043] Figure 1A schematic diagram of a battery pack system according to an embodiment of the present application;

[0044] Figure 2 A schematic diagram of a DC / DC converter and a DC transformer of a battery pack and a connection relationship with a controller according to an embodiment of the present application;

[0045] Figure 3 A schematic diagram of a DC / DC converter control method according to an embodiment of the present application;

[0046] Figure 4 A control block diagram of a DC transformer according to an embodiment of the present application. DETAILED DESCRIPTION

[0047] The present application will be further described with reference to the drawings and embodiments, obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art shall belong to the scope of protection of the embodiments of the present application.

[0048] At present, the battery capacity demand of household energy storage is generally 5-30kwh, according to different customer application scenarios in different regions, customers need different battery capacity. However, the grid voltage is usually 220 / 380VAC, which leads to different battery configurations to meet the application under the same grid voltage system, either sacrificing the efficiency of battery charging and discharging, or adding a level of converter with adjusting the output impedance of the battery at the battery interface, to realize the high efficiency charging and discharging of different battery configurations to the unified grid system. At present, the mainstream way is to add a level of battery converter in the converter to meet the adaptation of the converter to different customer battery pack configurations. This method has low cost and is widely used. However, the most obvious problem is that the battery configuration of some users will lead to low system efficiency, and the capacity limit of single battery is also very large, such as limiting the 51v battery pack below 50Ah. For 100AH battery, the charging and discharging is limited and even cannot be used. This seriously affects the adaptation problem between the converter and the battery, thereby indirectly affecting the economic effect of the energy storage system.

[0049] Under this circumstance, the battery pack system of the present application avoids the above problems, which can effectively adjust the output impedance characteristics of the battery, and efficiently realize the demand of different batteries to the unified grid system.

[0050] Reference Figure 1The battery pack system of the application is applied to a low-voltage large-capacity battery pack with BMS function, and the system comprises: a battery pack with N+1 battery cells in series, a fuse FUSE, a disconnecting switch K1, a soft start switch K2 and a resistor R1, a DC / DC regulator, a DC transformer DCX, a BMS and a controller. The input end of the DC / DC regulator is connected with the output end of the battery pack system, and the output end of the DC / DC regulator is connected with the input end of the DC transformer DCX; the controller is connected with the DC / DC regulator and the DC transformer DCX respectively.

[0051] The controller is used for acquiring the current flowing through the inductor in the DC / DC regulator and the first voltage across the capacitor, so as to obtain the corresponding power value;

[0052] The controller is also used for acquiring the second voltage across the capacitor between the output ends of the DC / DC regulator;

[0053] The controller is also used for outputting a signal for controlling the charging or discharging of the DC / DC regulator and the DC transformer DCX based on the power value and the second voltage.

[0054] The battery pack with N+1 battery cells in series constitutes the required battery capacity, wherein the capacity of the single battery cell can be flexibly selected as the optimal battery cell scheme in the market in terms of cost, so as to ensure that the entire battery pack and the energy storage system have the optimal cost performance.

[0055] The fuse FUSE is used for ensuring the safety in case of failure of the battery pack, and in an extreme case, the battery cell can be disconnected to avoid out of control;

[0056] The disconnecting switch K1 is used for cutting off the connection between the battery cell and the load or the power supply, so as to ensure that the battery pack can effectively perform protection actions such as overcharging, overdischarging, overcurrent and short circuit;

[0057] The soft start switch K2 and the resistor R1 are used for slow start of the output voltage of the battery pack;

[0058] The BMS controller is used for sampling the voltage and current of each battery cell in series, sampling the temperature of each component of the battery pack, and generating a driving signal of the disconnecting switch and the soft start switch, and simultaneously realizing SOC, SOH, equalization control, overcharge and discharge protection, over-temperature protection and other functions for the battery cell.

[0059] The DC / DC regulator is used for battery pack voltage adjustment, realizing charging and discharging of the battery pack, and adjusting the output port characteristics of the battery pack, so as to satisfy direct parallel connection of multiple battery packs and parallel connection with a PCS DC bus.

[0060] The DC transformer DCX is used for high-ratio DC voltage conversion, so as to satisfy flexible configuration of the battery pack interface voltage and the battery pack voltage, and simultaneously maintain high efficiency of the system.

[0061] The controller unit is used for voltage and current sampling of the DC / DC regulator and the DC transformer DCX, semiconductor device driving signal, battery pack output voltage and current and power control of the DC / DC regulator and the DC transformer DCX, fault protection and other functions.

[0062] The battery pack outputs positive and negative B+B-, the DC / DC regulator outputs positive and negative DCLINK+ DCLINK-, and the DC transformer DCX outputs positive and negative P+P-.

[0063] The battery pack output positive and negative B+B- is connected to the DC / DC regulator input, the DC / DC regulator output DCLINK+ DCLINK- is connected to the DC transformer DCX input, and the DC transformer DCX output is connected to the battery pack output P+P-. In addition, the controller is connected to the BMS module through the communication line, and the controller is connected to the DC / DC regulator and the DC transformer DCX through the sampling signal and the driving signal respectively, wherein the sampling signal includes voltage and current sampling signals of the input and output interfaces.

[0064] Referring to Figure 2 , the controller is used to obtain the current flowing through the inductor in the DC / DC regulator and the first voltage across the capacitor, thereby obtaining the corresponding power value;

[0065] The controller is also used to obtain the second voltage across the capacitor between the DC / DC regulator output terminals;

[0066] The controller is also used to output a signal for controlling the charging or discharging of the DC / DC regulator and the DC transformer DCX based on the power value and the second voltage.

[0067] The controller includes a first difference device, a power regulator connected to the first difference device, a second difference device, a voltage regulator connected to the second difference device, a first comparator, a third difference device connected to the first comparator, and a current regulator connected to the third difference device.

[0068] The first difference device is used to subtract the power value from a reference power and input the difference to the power regulator;

[0069] The second difference device is used to subtract the second voltage from a reference voltage and input the difference to the voltage regulator;

[0070] The first comparator is used to compare the outputs of the power regulator and the voltage regulator and output the minimum value to the third difference device;

[0071] The third difference device is used to subtract the output of the third difference device from the current in the DC / DC regulator and input the difference to the current regulator;

[0072] The current regulator is used to output a control signal to control the conduction or closure of the fifth switch and the sixth switch in the DC / DC regulator and the first switch, the second switch, the third switch and the fourth switch in the DC transformer DCX.

[0073] The DC / DC regulator comprises a first capacitor, a current sensor, a first inductor, a fifth switch, a fifth diode, a sixth switch, a sixth diode and a second capacitor.

[0074] The first capacitor is connected to one end of the first inductor through the current sensor.

[0075] The fifth diode and the sixth diode are connected in series.

[0076] The DC transformer DCX comprises a first switch with a first anti-parallel diode, a second switch with a second anti-parallel diode, a third switch with a third anti-parallel diode and a fourth switch with a fourth anti-parallel diode.

[0077] The DC transformer DCX further comprises a transformer, a second inductor, a third capacitor and a fourth capacitor.

[0078] One end of the primary winding of the transformer is connected to the input end of the first diode.

[0079] The transformer is a high-frequency transformer.

[0080] The transformer comprises two primary windings and one secondary winding.

[0081] The DC / DC regulator comprises a first capacitor, a current sensor, a first inductor, a fifth switch, a fifth diode, a sixth switch, a sixth diode and a second capacitor. Figure 3 The DC transformer DCX comprises a first switch with a first anti-parallel diode, a second switch with a second anti-parallel diode, a third switch with a third anti-parallel diode and a fourth switch with a fourth anti-parallel diode. Figure 4The DC / DC regulator uses common DC / DC converter topologies, such as BUCK, BOOST, etc. with voltage stabilization function. It contains inductance current sampling, input and output voltage sampling, and switch driving signal. Its control module contains power regulator, voltage regulator, and current regulator. Power measurement value Pmeas is obtained through voltage and current sampling calculation, and then subtracted from Pref and input to the power regulator. Voltage measurement value is obtained through voltage sampling, and then subtracted from voltage given value Vref and input to the voltage regulator. The smaller of the outputs of the voltage regulator and the current regulator is subtracted from current measurement value Imeas and input to the current regulator, and the current regulator generates PWM driving signal through operation to control the fifth switch and the sixth switch in the DC / DC regulator and the first switch, the second switch, the third switch, and the fourth switch in the DC transformer DCX to be turned on or closed.

[0082] The DCX DC transformer uses common DC transformer topologies, such as LLC, CLLC, charge pump, SRC, etc. It contains but is not limited to driving signals of power switch tubes. Fixed switching frequency or fixed duty cycle is used to generate driving signals of power tubes, so that the converter has the characteristics of DC transformer, and the input and output voltages meet the set transformation ratio.

[0083] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced by the same, without departing from the spirit and scope of the present application. Any modification or equivalent replacement, which does not depart from the spirit and scope of the present application, should be covered within the protection scope of the claims of the present application.

Claims

1. A battery pack system, characterized by, The system comprises a DC / DC regulator, a DC transformer DCX, a controller and a battery pack system, wherein an input end of the DC / DC regulator is connected with an output end of the battery pack system, an output end of the DC / DC regulator is connected with an input end of the DC transformer DCX, and the controller is connected with the DC / DC regulator and the DC transformer DCX respectively; The controller is configured to acquire a current flowing through an inductor in the DC / DC regulator and a first voltage across a capacitor, thereby obtaining a corresponding power value; The controller is further configured to acquire a second voltage across the capacitor between output ends of the DC / DC regulator; The controller is further configured to output a signal for controlling the DC / DC regulator and the DC transformer DCX to charge or discharge based on the power value and the second voltage; The controller comprises a first difference device, a power regulator connected with the first difference device, a second difference device, a voltage regulator connected with the second difference device, a first comparator, a third difference device connected with the first comparator, and a current regulator connected with the third difference device; The first difference device is configured to subtract the power value from a reference power and input a difference value into the power regulator; The second difference device is configured to subtract the second voltage from a reference voltage and input a difference value into the voltage regulator; The first comparator is configured to compare outputs of the power regulator and the voltage regulator and output a minimum value to the third difference device; The third difference device is configured to subtract a current in the DC / DC regulator from an output of the third difference device and input a difference value into the current regulator; The current regulator is configured to output a control signal to control the fifth switch and the sixth switch in the DC / DC regulator and the first switch, the second switch, the third switch and the fourth switch in the DC transformer DCX to be turned on or closed.

2. The battery pack system of claim 1, wherein, The DC / DC regulator comprises a first capacitor, a current sensor, a first inductor, a fifth switch, a fifth diode, a sixth switch, a sixth diode and a second capacitor; The first capacitor is connected with one end of the first inductor through the current sensor, and the other end of the first inductor is connected with an input end of the fifth diode and an output end of the sixth diode respectively; The fifth diode and the sixth diode are connected in series, the fifth switch and the sixth switch are connected in parallel with the fifth diode and the sixth diode respectively, and the second capacitor is connected with an output end of the fifth diode and an input end of the sixth diode respectively.

3. The battery pack system of claim 2, wherein, The DC transformer DCX comprises a first switch with an anti-parallel first diode, a second switch with an anti-parallel second diode, a third switch with an anti-parallel third diode and a fourth switch with an anti-parallel fourth diode; The DC transformer DCX further comprises a transformer, a second inductor, a third capacitor and a fourth capacitor. One end of the primary winding of the transformer is connected with the input end of the first diode; the other end of the primary winding of the transformer is connected with the input end of the second diode; one end of the secondary winding of the transformer is connected with one end of the second inductor; the other end of the secondary winding of the transformer is connected with the input end of the fourth diode; the other end of the second inductor is connected with the output end of the fourth diode and the input end of the third diode through the third capacitor respectively; the fourth capacitor is connected with the output end of the third diode and the input end of the fourth diode respectively.

4. The battery pack system of claim 3, wherein, The transformer is a high-frequency transformer; The transformer comprises two primary windings and one secondary winding; the input end of the sixth diode is connected with the common end of the two primary windings of the transformer; the output end of the fifth diode is connected with the output end of the first diode.

5. The battery pack system of claim 1, wherein, The battery pack system comprises a battery pack, an isolation switch, a soft start switch, a resistor and a BMS; The positive electrode of the battery pack is connected with the common end of the isolation switch and the soft start switch through a fuse; the negative electrode of the battery pack is connected with the DC / DC regulator; The isolation switch and the soft start switch are connected in parallel, for cutting off the connection between the battery cell and the load or the power supply, to protect the safety of the battery pack system; the soft start switch and the resistor are connected in series, for slow starting of the output voltage of the battery pack system; The common end of the resistor and the isolation switch is connected with the DC / DC regulator; The BMS is used for sampling the voltage and current of each battery cell in the series-connected battery pack, sampling the temperature of each component in the battery pack system, and generating the driving signal of the isolation switch and the soft start switch.

6. The battery pack system of claim 5, wherein, The battery pack comprises a plurality of battery units connected in series.

7. A control method of a battery pack system characterized by, The method is applied to the battery pack system of any one of claims 1 to 6, and the method comprises: Step 1: obtaining the power value in the DC / DC regulator and the voltage value across the second capacitor; Step 2: obtaining the control signal of the DC / DC regulator and the DC transformer DCX based on the power value, the voltage value across the second capacitor, and reference power value and reference voltage.

8. The method of claim 7, wherein, The power value in the DC / DC regulator is obtained by: obtaining the current value flowing through the first inductor in the DC / DC regulator and the voltage value across the first capacitor, so as to obtain the corresponding power value; The step 2 comprises: Step 21: subtracting the power value from the reference power value, and inputting the result of the subtraction into a power regulator; subtracting the voltage value across the capacitor from the reference voltage, and inputting the result of the subtraction into a voltage regulator; Step 22: obtaining the minimum value in the output results of the power regulator and the voltage regulator; Step 23: subtracting the minimum value from the current value obtained from the DC / DC regulator, and inputting the result of the subtraction into a current regulator; Step 24: obtaining the output signal of the current regulator.

9. The method of claim 8, wherein, The output signal in the step 24 is a control signal for turning on or closing the fifth switch and the sixth switch in the DC / DC regulator and the first switch, the second switch, the third switch and the fourth switch in the direct current transformer DCX. The output signal in the step 24 is a control signal for turning on or closing the fifth switch and the sixth switch in the DC / DC regulator and the first switch, the second switch, the third switch and the fourth switch in the direct current transformer DCX.

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