High-side series drive sodium battery protection method and system

Abstract

The invention discloses a high-side series drive sodium battery protection method and system, and relates to the technical field of battery protection, and the method comprises the steps: collecting the data information of each monomer of a sodium battery pack through a sensor, and carrying out the preprocessing; judging based on the preprocessed data, and starting balancing operation; a PWM signal with a fixed frequency is generated to control the on and off of the MOSFET switch; and the duty ratio and the frequency of the PWM signal are adjusted in real time by monitoring the voltage fluctuation of the resonant capacitor. Through an active equalization mode of the switched capacitor, efficient equalization of voltage in the battery pack is realized, energy loss and heating are reduced, and the service life of the battery is prolonged. According to the invention, a high-side protection framework is adopted, so that the system can keep stable communication even when battery protection is triggered, and the overall safety and stability are improved; the system integrates a self-developed chip master control module and SOC calculation and fault diagnosis functions, can monitor the battery state in real time and perform intelligent management, and significantly improves the reliability and expansibility of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of battery protection, and in particular to a high-side series-driven sodium battery protection method and system. Background Art

[0002] In order to ensure the long-term stable charging of electric bicycles, the safety and reliability of the battery system need to be further improved. The voltage of sodium battery cells is 2.8-4.2V. A single battery cannot meet the capacity and voltage requirements of electric bicycles. Therefore, the batteries are connected in parallel to increase the capacity of the battery pack, and the batteries are connected in series to increase the terminal voltage of the battery pack. However, there are inevitably slight differences in the electrification parameters of the battery during the manufacturing process. At the same time, the battery charging and discharging process is a process that involves the mutual conversion of electrical energy, chemical energy and thermal energy. It has internal reaction opacity and is easily affected by many factors such as operating temperature, electrode degradation and charge and discharge rate. The battery terminal voltage is highly nonlinear and uncertain. Long-term series charging and discharging causes the problem of unbalanced battery cell voltage. Subject to the "short board effect", the actual capacity of the battery pack depends on the highest voltage cell and the lowest voltage cell. The unbalanced battery cells lead to a decrease in the actual capacity of the battery. Traditional battery charging circuits often judge the energy in the battery pack by the terminal voltage of the battery pack. When the high-voltage cell reaches the threshold voltage, the remaining cells are not fully charged, and the battery pack voltage is also lower than the threshold. If the charger continues to charge, it will cause the high-voltage battery pack to overcharge. Overcharging will cause serious attenuation of the battery cell capacity. Long-term overcharging or over-discharging can cause thermal runaway, combustion or explosion of batteries. Electric bicycles frequently catch fire or spontaneously combust during charging, and most of these accidents are caused by thermal runaway after battery deterioration. Therefore, battery pack voltage imbalance has become a major hidden danger threatening energy security.

[0003] At present, there are several main methods to improve the consistency of each monomer in the battery pack: (1) improve the battery manufacturing process and sorting grouping technology, or manually select batteries with similar performance to reduce the difference in electrochemical parameters between monomers in the battery pack; (2) ensure the consistency of external parameters during the operation of the battery, and use heat dissipation devices and management systems to ensure that the temperature, current rate and charge and discharge depth of the battery pack are consistent during operation to avoid uneven monomer voltage caused by external factors; (3) by introducing a balancing circuit, using energy storage elements and switching elements to redistribute the energy of each monomer in the battery pack to improve the battery voltage consistency. The first two methods are difficult to guarantee with advanced technology, so we can only hope that method (3) can be achieved by introducing a balancing circuit.

[0004] The current balancing method is through energy dissipation / transfer. The existing battery pack voltage balancing topology can be divided into passive balancing method and active balancing method according to the energy dissipated / transferred during the balancing process. The passive balancing method consumes the energy in the high-voltage battery pack through power resistors to ensure the consistency of the voltage of each cell. Its advantages are simple circuit structure, low cost, simple control logic and high reliability, and it is widely used in energy storage systems. However, in the passive balancing process, energy is consumed in the form of heat energy through power resistors, resulting in low balancing efficiency, and the heat generated at the resistor end will also cause uneven heat dissipation. The active balancing system uses energy storage components to transfer energy to low-voltage batteries to achieve battery pack balancing. This equalizer has a higher balancing efficiency. However, the circuit structure of the active balancing method is more complex than that of the passive balancing method, so how to reduce the complexity of the equalizer circuit has become a research hotspot. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] Therefore, the technical problem solved by the present invention is: how to effectively realize voltage balancing of battery packs in a high-side series-driven sodium battery protection system, while reducing energy consumption and heat generation during the balancing process, extending battery life, and ensuring the stability and safety of the system under long-term operation.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a high-side series drive sodium battery protection method, which comprises the following steps:

[0008] Use sensors to collect data information from each cell of the sodium battery pack for preprocessing;

[0009] Make judgments based on the preprocessed data and start the balancing operation;

[0010] Generate a fixed-frequency PWM signal to control the on and off of the MOSFET switch;

[0011] By monitoring the voltage fluctuation of the resonant capacitor, the duty cycle and frequency of the PWM signal can be adjusted in real time.

[0012] As a preferred solution of the high-side series-driven sodium battery protection method of the present invention, wherein: the data information of each monomer of the sodium battery group is collected by using a sensor to collect the voltage data of each monomer of the sodium battery group in real time, and the voltage difference threshold is designed;

[0013] The preprocessing is to filter the collected data to remove high-frequency noise and abnormal data generated during the collection process to obtain stable voltage data.

[0014] As a preferred solution of the high-side series-driven sodium battery protection method described in the present invention, wherein: the judgment based on the preprocessed data and the start of the balancing operation include:

[0015] The voltage data of each single cell of the sodium battery group that has been preprocessed are analyzed, and the voltage difference between each single cell is compared; when the voltage difference between any two or more single cells exceeds the set threshold, it is determined that the sodium battery group is in a voltage imbalance state, and a balance start signal is generated.

[0016] As a preferred solution of the high-side series-driven sodium battery protection method described in the present invention, the balancing operation includes:

[0017] When the sodium battery group is in a voltage imbalance state, it includes state one and state two;

[0018] State 1 is to turn on the MOSFET switch by controlling the PWM signal, so that the current flows from the high-voltage single battery to the low-voltage single battery;

[0019] State 2 is to turn on the MOSFET switch by controlling the PWM signal, so that the current flows from the low-voltage single battery to the high-voltage single battery;

[0020] By switching between state 1 and state 2 alternately, the voltages of the high-voltage monomer and the low-voltage monomer gradually approach the middle value until a preset equilibrium state is reached, thus completing the equilibrium operation.

[0021] As a preferred solution of the high-side series drive sodium battery protection method described in the present invention, wherein: the generation of a fixed-frequency PWM signal to control the on and off of the MOSFET switch includes:

[0022] Equations are established for state 1 and state 2 for analysis. When a single battery pack is converted to a multi-battery pack, the operating frequency remains unchanged and the balancing current works in a resonant state. The expression is:

[0023]

[0024] When the resonant circuit is connected in series, the resonant frequency expression is:

[0025]

[0026] When the resonant circuit is in parallel, the resonant frequency expression is:

[0027]

[0028] Among them, a is the product of L and C, L is the inductance of the resonant inductor, and C is the capacitance of the resonant capacitor.

[0029] Another object of the present invention is to provide a high-side series-driven sodium battery protection system, which can reduce energy loss and heat generation while maintaining battery pack voltage balance through an active balancing method based on a series resonant switch capacitor, thereby extending battery life and improving system stability. When there is a voltage difference in the battery pack, the energy flow direction is dynamically adjusted in real time to automatically achieve efficient balancing of battery cell voltages without unnecessary energy consumption, thereby solving the problems of excessive energy loss, low efficiency and heat generation during the balancing process of the existing sodium battery protection system.

[0030] In order to solve the above technical problems, the present invention provides the following technical solutions: a high-side series drive sodium battery protection system, comprising: an acquisition module, a power module, a balancing module, a self-developed chip main control module, a SOC calculation module, a fault diagnosis module, a display module, a positioning and wireless data transmission module;

[0031] The acquisition module collects the voltage, current and temperature data of the sodium battery in real time and transmits them to the self-developed chip main control module;

[0032] The power module obtains energy from the sodium battery and converts it into a suitable voltage to supply power to the acquisition module, the balancing module, and the self-developed chip main control module;

[0033] The balancing module is used to keep the voltage of each monomer of the series-connected sodium battery balanced with each other. The balancing command is sent by the self-developed chip main control module to the battery balancing module to adjust the sodium battery;

[0034] The self-developed chip main control module calculates the SOC of the sodium battery based on the voltage, current and temperature data collected by the acquisition module, and performs real-time diagnosis of faults;

[0035] The SOC calculation module obtains the battery data of the battery sampling module and uses a high-precision coulomb meter to calculate the battery SOC and the charged power;

[0036] The fault diagnosis module provides real-time safety protection of sodium batteries and fault diagnosis through overcharge, short circuit, over discharge, over current, disconnection and over temperature protection methods;

[0037] The display module is a self-developed chip main control module that displays the voltage, current and temperature data of the sodium battery collected in real time via Bluetooth;

[0038] The positioning and wireless data transmission module is a self-developed chip main control module that reads and sends relevant data to a remote system through a serial port. The data also includes real-time geographic location information.

[0039] As a preferred solution of the high-side series-driven sodium battery protection method described in the present invention, the acquisition module includes a plurality of strings of sodium-ion batteries for sampling, and transmits battery power parameters between the self-developed chip main control module through the SP-interface;

[0040] The power module utilizes the sodium ion battery voltage to power the high-side series-driven sodium ion battery management system.

[0041] As a preferred solution of the high-side series-driven sodium battery protection method described in the present invention, the balancing module controls a plurality of strings of sodium-ion batteries, performs real-time active balancing, takes high and supplements low, does not consume energy during energy transfer, does not generate heat during balancing, suppresses the increase of pressure difference, and optimizes battery life.

[0042] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the high-side series-driven sodium battery protection method as described above are implemented.

[0043] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the high-side series-driven sodium battery protection method as described above.

[0044] The beneficial effects of the present invention are as follows: through an active balancing method based on a series resonant switched capacitor, efficient voltage balancing in the battery pack is achieved, energy loss and heat generation are effectively reduced, and thus battery life is extended; the system adopts a high-side protection architecture, so that the system can maintain stable communication even when the battery protection is triggered, thereby improving overall safety and stability; at the same time, the system integrates a self-developed chip main control module, SOC calculation and fault diagnosis functions, which can monitor the battery status in real time and perform intelligent management, significantly improving the reliability and scalability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0046] Figure 1 An overall flow chart of a high-side series-driven sodium battery protection method provided by the first embodiment of the present invention;

[0047] Figure 2 A structural diagram of a high-side series-driven sodium battery protection system provided by a second embodiment of the present invention;

[0048] Figure 3 A series resonant switch capacitor balancing topology diagram of a high-side series drive sodium battery protection system provided by the second embodiment of the present invention;

[0049] Figure 4 A current flow analysis diagram of a minimum balancing unit of a high-side series-driven sodium battery protection system provided by the second embodiment of the present invention, 4a is a current flow diagram of the circuit in state 1, and 4b is a current flow diagram of the circuit in state 2;

[0050] Figure 5 A series equalization circuit current and capacitor terminal voltage waveform diagram of a high-side series drive sodium battery protection system provided by the second embodiment of the present invention;

[0051] Figure 6 The experimental result diagram of a sodium ion battery balancing module of a high-side series drive sodium battery protection system provided by the second embodiment of the present invention, 6a is based on the series resonant switch capacitor diagram, and 6b is based on the series switch capacitor diagram;

[0052] Figure 7 The experimental waveform diagram of a switching frequency of 16kHz for a high-side series drive sodium battery protection system provided by the second embodiment of the present invention, 7a is based on a series resonant switch capacitor diagram, and 7b is based on a series switch capacitor diagram;

[0053] Figure 8 A diagram showing dynamic experimental results of a battery balancing circuit of a high-side series-driven sodium battery protection system during constant current charging provided by a second embodiment of the present invention;

[0054] Fig. 9 A diagram showing dynamic experimental results of a battery balancing circuit of a high-side series-driven sodium battery protection system during constant current discharge provided by the second embodiment of the present invention. DETAILED DESCRIPTION

[0055] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0056] Example 1, reference Figure 1 According to an embodiment of the present invention, a high-side series drive sodium battery protection method is provided, comprising:

[0057] Use sensors to collect data information from each cell of the sodium battery pack for preprocessing;

[0058] Make judgments based on the preprocessed data and start the balancing operation;

[0059] Generate a fixed-frequency PWM signal to control the on and off of the MOSFET switch;

[0060] By monitoring the voltage fluctuation of the resonant capacitor, the duty cycle and frequency of the PWM signal can be adjusted in real time.

[0061] The sensor is used to collect the voltage data of each cell of the sodium battery pack in real time, and the voltage difference threshold is designed; the collected data is filtered to remove the high-frequency noise and abnormal data generated during the collection process to obtain stable voltage data.

[0062] The voltage data of each single cell of the sodium battery group that has been preprocessed are analyzed, and the voltage difference between each single cell is compared; when the voltage difference between any two or more single cells exceeds the set threshold, it is determined that the sodium battery group is in a voltage imbalance state, and a balance start signal is generated.

[0063] When the sodium battery group is in a voltage imbalance state, it includes state one and state two;

[0064] State 1 is to turn on the MOSFET switch by controlling the PWM signal, so that the current flows from the high-voltage single battery to the low-voltage single battery;

[0065] State 2 is to turn on the MOSFET switch by controlling the PWM signal, so that the current flows from the low-voltage single battery to the high-voltage single battery;

[0066] By switching between state 1 and state 2 alternately, the voltages of the high-voltage monomer and the low-voltage monomer gradually approach the middle value until a preset equilibrium state is reached, thus completing the equilibrium operation.

[0067] Equations are established for state 1 and state 2 for analysis. When a single battery pack is converted to a multi-battery pack, the operating frequency remains unchanged and the balancing current works in a resonant state. The expression is:

[0068]

[0069] When the resonant circuit is connected in series, the resonant frequency expression is:

[0070]

[0071] When the resonant circuit is in parallel, the resonant frequency expression is:

[0072]

[0073] Among them, a is the product of L and C, L is the inductance of the resonant inductor, and C is the capacitance of the resonant capacitor.

[0074] Example 2, reference Figure 2 to Figure 9 As an embodiment of the present invention, a system for a high-side series-driven sodium battery protection method is provided, comprising: an acquisition module, a power module, a balancing module, a self-developed chip main control module, a SOC calculation module, a fault diagnosis module, a display module, a positioning and wireless data transmission module;

[0075] The acquisition module collects the voltage, current and temperature data of the sodium battery in real time and transmits them to the self-developed chip main control module;

[0076] The power module obtains energy from the sodium battery and converts it into a suitable voltage to supply power to the acquisition module, the balancing module, and the self-developed chip main control module;

[0077] The balancing module is used to keep the voltage of each monomer of the series-connected sodium battery balanced with each other. The balancing command is sent by the self-developed chip main control module to the battery balancing module to adjust the sodium battery;

[0078] The self-developed chip main control module calculates the SOC of the sodium battery based on the voltage, current and temperature data collected by the acquisition module, and performs real-time diagnosis of faults;

[0079] The SOC calculation module obtains the battery data of the battery sampling module and uses a high-precision coulomb meter to calculate the battery SOC and the charged power;

[0080] The fault diagnosis module provides real-time safety protection of sodium batteries and fault diagnosis through overcharge, short circuit, over discharge, over current, disconnection and over temperature protection methods;

[0081] The display module is a self-developed chip main control module that displays the voltage, current and temperature data of the sodium battery collected in real time via Bluetooth;

[0082] The positioning and wireless data transmission module is a self-developed chip main control module that reads and sends relevant data to a remote system through a serial port. The data also includes real-time geographic location information.

[0083] Furthermore, the acquisition module samples 3 to 19 strings of sodium-ion batteries and uses an SP-interface to facilitate the transmission of battery power parameters between the self-developed chip main control module.

[0084] Furthermore, the power module is capable of utilizing the sodium ion battery voltage to power the high-side series-driven sodium ion battery management system.

[0085] Furthermore, the high-side series drive is relative to the low-side series drive, which involves two major issues: high-side solution or low-side solution, series architecture or parallel architecture. (1) The low-side solution is currently a more mature and easier to implement solution, and most two-wheeled vehicles are also designed based on the low-side solution. At the same time, most current analog front ends also integrate low-side drive capabilities. However, the low-side protection solution has a disadvantage:

[0086] When the MOSFET is turned off, the ground of the battery pack and the ground of the system end are no longer shared, so once the protection is triggered to turn off the charging and discharging MOSFETs, the battery end and the system end can no longer communicate directly.

[0087] If you want to continue to communicate, you need to use isolated communication, which will not only increase the cost, but also increase the power consumption. Especially during undervoltage protection, excessive communication power consumption will make the battery pack that is already undervoltage even worse.

[0088] Therefore, the low-side solution is mainly used in products that are more cost-sensitive and do not have complex communications. Compared with the low-side protection, the high-side protection solution still shares the same ground with the system end even after the protection is triggered, so communication between them can still be achieved without adding isolated communication, and the positive end of the battery is disconnected after the protection is triggered, making the system safer. (2) The charging port and the discharging port of the series architecture share one port. The disadvantage is that the number of MOSFETs needs to be selected according to the maximum value of the charge and discharge current. If the difference between the charging current and the discharge current is large, such as the charging current of the lithium battery pack of a general electric vehicle is smaller than the discharge current, if the series architecture is selected, more MOSFETs need to be selected than actually needed, resulting in unnecessary waste. In addition, whether it is charging or discharging, all currents need to pass through the MOSFET, which will generate more losses and heat, and to a certain extent reduce the effective capacity of the battery. The advantage is that there is no need to consider the problem of reverse current, because the back-to-back connection of the MOSFET can block the reverse current. In addition, the series architecture can save a power line and a terminal. Compared with the series architecture, the parallel architecture can select the number and model of MOSFETs according to the actual charge and discharge current. And whether charging or discharging, it only passes through one level of MOSFET, so the loss and heat are less. The disadvantage is that the reverse current needs to be considered, such as flowing to the charging port through the body diode of MOSFET, or flowing to the battery cell through the body diode of MOSFET. If these current paths are to be blocked, additional circuit assistance is required.

[0089] Furthermore, the self-developed chip main control module adopts the self-developed ultra-low power IoT chip PQ32L048-LP48-TG, which is based on the ARMCortex-M0+ ultra-low power 32-bit MCU, with up to 256KBFlash, 32KB SRAM, LCD interface, ADC and DACs and AES module, and is designed with an independent watchdog, with stable performance and no crash.

[0090] Furthermore, the SOC calculation module obtains the battery data of the battery sampling module and uses a high-precision coulomb meter (based on the current-time integration) to accurately calculate the battery SOC and the amount of charge. A mature solution is adopted and will not be described here.

[0091] Furthermore, the fault diagnosis module has six real-time safety protection and fault diagnosis functions: overcharging, short circuit, over-discharging, over-current, disconnection, and over-temperature protection.

[0092] Furthermore, the display module is capable of displaying the operating status of the sodium-ion battery module and the operating status of the high-side series-driven sodium-ion BMS board.

[0093] Furthermore, the positioning and wireless data transmission module obtains the longitude and latitude of the device in real time based on the Beidou function, and interacts with the monitoring system in real time with the 4G / 5G function.

[0094] Furthermore, the balancing module controls 3 to 19 strings of sodium-ion batteries, and has real-time active balancing, taking high and supplementing low, energy transfer without consumption, balancing without heat generation, suppressing the increase of voltage difference, and extending battery life. In order to reduce the complexity of the balancing circuit, the cost of the balancing system and the complexity of the control logic, a series resonant switch capacitor balancing topology is designed.

[0095] Furthermore, the series resonant switched capacitor balancing topology is as follows: Figure 3 In order to describe its principle, the working principle is explained by taking 4 series of sodium ion batteries as an example. After MOSFET Q1, Q3, Q5 and Q7 are turned on, batteries B1, B2, B3 and the resonant capacitor converter are connected in series. After MOSFET Q2, Q4, Q6 and Q8 are turned on, batteries B2, B3, B4 and the resonant capacitor converter are connected in series. The entire circuit is controlled by using a pair of fixed-frequency complementary PWM signals, and MOSFET Q1, Q3, Q5 and Q7 are controlled by the positive pulse signal of PWM. MOSFET Q2, Q4, Q6 and Q8 are controlled by the negative pulse signal of PWM.

[0096] To simplify the analysis, the internal parameters of the circuit are assumed as follows.

[0097] C n and L n (n=1, 2, 3) represent battery B respectivelyn The corresponding capacitors and inductors. All capacitors and inductors have the same value, C and L respectively, and the equivalent resistance R n =R;

[0098] V Bn Represents battery B n voltage, assuming that the initial battery voltage satisfies V B1 >V B2 >V B3 >V B4 .

[0099] The full switch is controlled by a pair of fixed frequency complementary PWM signals.

[0100] In steady state, the balancing circuit of the series resonant switched capacitor includes state 1 and state 2 in one switching cycle.

[0101] State 1 (t0-t1): MOSFETQ1 and Q3 are turned on, while MOSFETQ2 and Q4 are turned off. Figure 4 (a). In this state, battery B1 transfers energy to the resonant switch capacitor 1 and resonant switch capacitor 2 converters through Q1 and Q3. The charging current i Ci and capacitor voltage u Ci It can be expressed as

[0102]

[0103] Where V Cn represents the voltage at the series terminals of capacitors C1 and C2 at time t0, ρ = RC / 2L,

[0104] State 2 (t1-t2): MOSFETQ2 and Q4 are turned on, while MOSFETQ1 and Q3 are turned off. Figure 4 As shown in (b), the energy stored in the resonant switch capacitor is transferred to battery B2 through switches Q2 and Q4, and the energy is transferred from the high-voltage battery to the low-voltage battery, achieving balance. According to KVL, the balance current i flowing through B2 during state 2 is Ci and capacitor voltage u Ci It can be expressed as:

[0105]

[0106] Where V Cm Represents the voltage at the series terminals of capacitors C1 and C2 at time t1.

[0107] The key waveforms of the series resonant switched capacitor balanced topology are as follows: Figure 5 In state 1, when Q1 is turned on, the current waveform flowing through the switch is a half-sine wave, and the battery B1 charges the resonant capacitor, and the voltage VC1 Increases from the minimum value to the maximum value; in state 2, when Q2 is turned on, the current waveform flowing through the switch is a half-sine wave, the resonant capacitor charges the battery B2, and the capacitor voltage V C1 From maximum to minimum.

[0108] Substituting equation (1) into equation (2), V Cn and V Cm It can be expressed as:

[0109]

[0110] Solving equation (3), the voltage fluctuation ΔV of capacitor C in one cycle is C It can be expressed as:

[0111]

[0112] Battery B in one cycle n The average current flowing out is

[0113] i Bn =f×C×ΔV C (5)

[0114] Substituting formula (4) into formula (5), the average current of capacitor C in one balancing cycle is

[0115]

[0116] Among them, the average balancing current of the series switched capacitor is f×C×(V B1 -V B2 ), formula (6) shows that the average current of the series resonant switch capacitor is greater than the average current of the series switch capacitor.

[0117] The analysis process of multi-battery module unit is consistent with the analysis process of the minimum balancing unit current flow. The equations are still established from the two situations of state 1 (t0-t1) and state 2 (t1-t2) for analysis, but the equation dimension is larger, so it will not be repeated here. The conclusion is that after the addition of multiple battery packs, the operating frequency of the entire system remains unchanged, and the balancing current works in a resonant state.

[0118] The resonant frequency of the two resonant switched capacitor circuit branches is f, which can be obtained as follows

[0119]

[0120] Where a is the product of L and C.

[0121] The resonant frequency of two series LC resonant circuits is:

[0122]

[0123] When the branches are connected in series, the resonant frequency remains the same.

[0124]

[0125] By connecting in series, the shunt resistor R s becomes 2R, and L s It also becomes 2L, making the actual resonant frequency f1 equal to f.

[0126] The balancing module is applied in the sodium ion battery system based on the series resonant switched capacitor, and its performance is evaluated. Taking 4 strings of sodium ions and their protection system as an example, the sodium ion battery voltage V B 3~4.2V, all switches on the circuit board use N-channel MOSFET, model RFB7437PBF, and its on-resistance R D The MOSFET gate driver is controlled by a pair of complementary signals generated by the interrupt of the self-developed chip main control module. The capacitor uses a ceramic capacitor C1210C106M5R2C7186, with a capacitance of C n The ESR resistor R is 10μF C The resonant inductor L is 31mΩ. S The inductance is 10μH, the ESR resistor R L The working or control frequency f is 16kHz. The H-OK-voltage recorder LR8431 records the battery cell voltage. In order to verify the advantages of the series resonant switch capacitor topology compared with the series switch capacitor topology, a control group was set up with the same four sodium ion battery cells, and the inductor was removed and shorted. The capacitance value of the series switch capacitor and the system operating frequency were consistent with the series resonant switch capacitor balancing module.

[0127] The experimental results of the balancing module based on series resonant switched capacitors are as follows Figure 6 As shown in (a), the initial battery voltages are 3.655V, 3.801V, 3.897V and 3.461V, respectively. The maximum voltage gap between the batteries is 0.436V. It takes 52 minutes to achieve the balance of each battery pack. After balance, the battery voltages are 3.783V, 3.793V, 3.792V and 3.782V, respectively. The maximum voltage gap of the battery is 0.011V, which is much smaller than the international standard of 0.05V for the balance voltage difference. The module can always achieve simultaneous convergence of the battery cell voltages. Even under different voltage distributions, the series resonant capacitor balance module can achieve simultaneous balance. The results of the control group using a series switch capacitor balancer are shown in Figure 2. Figure 6As shown in (b), the initial battery voltages are 3.895V, 3.797V, 3.649V and 3.487V, with a maximum voltage difference of 0.436V. The equalizer performs equalization for 80 minutes, and the battery voltages after equalization are 3.781V, 3.753V, 3.825V and 3.723V, respectively, with a maximum voltage difference of 0.058V.

[0128] The experimental results of the balancing module based on series resonant switched capacitors are as follows Figure 7 As shown in (a), i Q1 is the current flowing through switch Q1 when the resonant switch capacitor is connected in series with the battery. By comparing with the formula, it can be concluded that in state 1, the resonant switch capacitor charges the battery. After turning on, the entire current waveform is a half-wave resonant wave. C1 It can be seen from the waveform that when the switch Q1 is turned on, the voltage value in the capacitor is the peak in a cycle. When the capacitor is fully charged by battery 1, when Q1 is turned off, the voltage at the capacitor C1 is the valley point. The experimental results are consistent with the theoretical analysis results. Figure 7 As shown in (b), when the maximum voltage gap of the battery is 0.1V, the voltage of capacitor C1 increases from 0.85V to 1.57V in one cycle, and the energy transmitted by capacitor C1 in one cycle is 8.73E-6J. Adding inductance at the same frequency increases the balancing speed by 3 times. In addition, the proposed topology circuit eliminates the inrush current.

[0129] The dynamic balancing results based on the series resonant switched capacitor balancing module under constant current charging conditions are as follows: Figure 8 The experimental results show that even when the battery pack is charging, the series resonant switched capacitor balancing module can ensure the voltage consistency of all battery cells and show good dynamic balancing performance.

[0130] The dynamic balancing results based on the series resonant switched capacitor balancing module under constant current discharge conditions are as follows: Fig. 9 As shown. The experimental results show that even when the battery pack is discharging, the series resonant switch capacitor balancing module ensures the voltage consistency of all battery cells and exhibits good dynamic balancing performance. Therefore, the series resonant switch capacitor balancing module can be used in static, charging or discharging states.

[0131] Based on the series resonant switched capacitor balancing module, the instantaneous balancing efficiency is measured to be 93.6%, the input power is 2.72 W, and the output power is 2.54 W. The calculated power loss of the system includes internal resistance loss of 0.108 W, switch conduction loss of 0.044 W, ESR loss of 0.027 W, and switching loss of 0.001 W.

[0132] The present invention realizes a simple and easy-to-use high-side series drive sodium battery protection system based on series resonant switch capacitor equalization. The system controls all switches in the circuit through a pair of fixed-frequency complementary PWM signals for equalization within the battery pack. The method can increase the equalization current by 3 times compared with the battery equalization module based on series switch capacitors at the same frequency, and at the same time uses inductors and capacitors to achieve resonant equalization to eliminate the current shock generated when the switch is turned on. Compared with the parallel capacitor equalization circuit, each battery cell requires 2 switches, and the complexity of the circuit is reduced. The energy of the single series resonant switch capacitor equalization circuit cannot be directly transferred to the low-voltage battery. The equalization efficiency is 93.6%, which is suitable as an equalization circuit in the battery pack. The system adopts high-side series drive, which solves the problem of low-side protection MOSFET being turned off without realizing direct communication. The series architecture saves a power line and a terminal, which is very suitable for application in electric bicycles.

[0133] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program code.

[0134] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0135] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0136] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0137] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A high-side series drive sodium battery protection method, characterized in that: include: Use sensors to collect data information from each cell of the sodium battery pack for preprocessing; Make judgments based on the preprocessed data and start the balancing operation; Generate a fixed-frequency PWM signal to control the on and off of the MOSFET switch; By monitoring the voltage fluctuation of the resonant capacitor, the duty cycle and frequency of the PWM signal can be adjusted in real time.

2. A high-side series drive sodium battery protection method as claimed in claim 1, characterized in that: The data information of each cell of the sodium battery group is collected by using a sensor to collect the voltage data of each cell of the sodium battery group in real time, and a voltage difference threshold is designed; The preprocessing is to filter the collected data to remove high-frequency noise and abnormal data generated during the collection process to obtain stable voltage data.

3. A high-side series drive sodium battery protection method as claimed in claim 2, characterized in that: The determination based on the preprocessed data and the initiation of the balancing operation include: The voltage data of each single cell of the sodium battery group that has been preprocessed are analyzed, and the voltage difference between each single cell is compared; when the voltage difference between any two or more single cells exceeds the set threshold, it is determined that the sodium battery group is in a voltage imbalance state, and a balance start signal is generated.

4. A high-side series drive sodium battery protection method as claimed in claim 3, characterized in that: The balancing operation includes: When the sodium battery group is in a voltage imbalance state, it includes state one and state two; State 1 is to turn on the MOSFET switch by controlling the PWM signal, so that the current flows from the high-voltage single battery to the low-voltage single battery; State 2 is to turn on the MOSFET switch by controlling the PWM signal, so that the current flows from the low-voltage single battery to the high-voltage single battery; By switching between state 1 and state 2 alternately, the voltages of the high-voltage monomer and the low-voltage monomer gradually approach the middle value until a preset equilibrium state is reached, thus completing the equilibrium operation.

5. A high-side series drive sodium battery protection method as claimed in claim 4, characterized in that: The generating of a fixed frequency PWM signal to control the on and off of the MOSFET switch comprises: Equations are established for state 1 and state 2 for analysis. When a single battery pack is converted to a multi-battery pack, the operating frequency remains unchanged and the balancing current works in a resonant state. The expression is: Where a is the product of L and C, L is the inductance of the resonant inductor, and C is the capacitance of the resonant capacitor; When the resonant circuit is connected in series, the resonant frequency expression is: When the resonant circuit is in parallel, the resonant frequency expression is:

6. A system using a high-side series drive sodium battery protection method as claimed in any one of claims 1 to 5, characterized in that: Acquisition module, power module, balancing module, self-developed chip main control module, SOC calculation module, fault diagnosis module, display module, positioning and wireless data transmission module; The acquisition module collects the voltage, current and temperature data of the sodium battery in real time and transmits them to the self-developed chip main control module; The power module obtains energy from the sodium battery and converts it into a suitable voltage to supply power to the acquisition module, the balancing module, and the self-developed chip main control module; The balancing module is used to keep the voltage of each monomer of the series-connected sodium battery balanced with each other. The balancing command is sent by the self-developed chip main control module to the battery balancing module to adjust the sodium battery; The self-developed chip main control module calculates the SOC of the sodium battery based on the voltage, current and temperature data collected by the acquisition module, and performs real-time diagnosis of faults; The SOC calculation module obtains the battery data of the battery sampling module and uses a high-precision coulomb meter to calculate the battery SOC and the charged power; The fault diagnosis module provides real-time safety protection of sodium batteries and fault diagnosis through overcharge, short circuit, over discharge, over current, disconnection and over temperature protection methods; The display module is a self-developed chip main control module that displays the voltage, current and temperature data of the sodium battery collected in real time via Bluetooth; The positioning and wireless data transmission module is a self-developed chip main control module that reads and sends relevant data to a remote system through a serial port. The data also includes real-time geographic location information.

7. A high-side series drive sodium battery protection system as claimed in claim 6, characterized in that: The acquisition module includes a plurality of strings of sodium ion batteries for sampling, and transmits battery power parameters between the self-developed chip main control module through the SP-interface; The power module utilizes the sodium ion battery voltage to power the high-side series-driven sodium ion battery management system.

8. A high-side series drive sodium battery protection system as claimed in claim 7, characterized in that: The balancing module controls a plurality of strings of sodium ion batteries, performs real-time active balancing, takes high voltage to compensate low voltage, transfers energy without consumption, generates no heat during balancing, suppresses increase in pressure difference, and optimizes battery life.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of a high-side series drive sodium battery protection method according to any one of claims 1 to 5 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of a high-side series drive sodium battery protection method as claimed in any one of claims 1 to 5 are implemented.

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