Wide voltage range power battery module load balancing system and method

Abstract

The invention discloses a wide-voltage-range power battery module load balancing system and method, and belongs to the technical field of power battery balancing. The system comprises a new battery module, a whole vehicle remaining battery module, a power balancing board and a control board; the power equalization board is provided with a front side interface, a rear side interface and a communication interface; a front-side interface of the power equalization board is connected with the remaining battery module of the whole vehicle, and a rear-side interface of the power equalization board is connected with the new battery module; a communication interface of the power equalization board is connected with the control board; and the power equalization board uploads the working state to the control board, receives an equalization instruction issued by the control board, and equalizes the remaining battery modules and the new battery modules of the whole vehicle according to the equalization instruction. Balancing of the new battery module and the remaining battery module of the whole vehicle can be achieved without external charging and discharging equipment, convenience is taken into account, and meanwhile waste of energy charged into the battery is avoided; an active equalization mode is realized, and the energy utilization rate is higher; the problem of wide input voltage range is solved, and the design is relatively simpler.

Description

Technical Field

[0001] The present invention belongs to the technical field of power battery balancing, and in particular relates to a power battery module load balancing system and method with a wide voltage range. Background Art

[0002] The development of new energy vehicles can not only reduce carbon emissions, but also reduce dependence on fossil fuels and reduce environmental pollution. The number of pure electric vehicles accounts for a large proportion of the total number of new energy vehicles, representing the development trend of new energy vehicles. Power batteries are one of the core components of pure electric vehicles. At present, lithium-ion power batteries have been widely used in the field of pure electric vehicles due to their high energy density, low self-discharge rate, and long cycle life. However, the voltage and capacity of lithium-ion batteries are low, and multiple cells need to be connected in series or in parallel to form a battery pack to meet the voltage and power requirements of pure electric vehicles. But first of all, due to the limited level of battery manufacturing, even different batteries produced in the same batch have different characteristics. Secondly, there are slight differences in the working environment of different battery cells in the battery pack. With the increase of usage time, the inconsistency of the battery pack gradually increases, and the "barrel effect" leads to a decrease in cruising range and a rapid decay of cycle life.

[0003] When the inconsistency of the cells inside the battery pack is serious, the power battery needs to be maintained and serviced. If there is a failed module, it needs to be replaced. However, under normal circumstances, there are large differences in the characteristic parameters such as voltage and charge state between the new module and the rest of the vehicle modules, and the "barrel effect" still exists. Therefore, after replacing the new module, charging or discharging balancing is still required to improve consistency. The current battery module balancing process has the following problems: First, external charging and discharging equipment is required, which is less convenient; second, passive balancing technology is used to dissipate excess energy in resistors, and the energy utilization rate is low.

[0004] This is a shortcoming of the prior art. Therefore, in view of the above-mentioned defects in the prior art, it is very necessary to provide a power battery module load balancing system and method with a wide voltage range. Summary of the invention

[0005] In view of the above-mentioned pure electric vehicle power batteries of the prior art are usually connected in series and parallel to form a battery pack for use, but due to the differences between the batteries, inconsistencies will occur as use increases. When the inconsistency is serious, the module needs to be replaced, and the new module needs to be charged and discharged balanced with the whole vehicle module. The existing balancing method requires external charging and discharging equipment, and adopts passive balancing, which wastes energy. The present invention provides a wide voltage range power battery module load balancing system and method to solve the above technical problems.

[0006] In a first aspect, the present invention provides a wide voltage range power battery module load balancing system, including a new battery module, a remaining battery module of a vehicle, a power balancing board and a control board;

[0007] The power balancing board is provided with a front side interface, a rear side interface and a communication interface;

[0008] The front interface of the power balancing board is connected to the remaining battery modules of the vehicle, and the rear interface of the power balancing board is connected to the new battery module;

[0009] The communication interface of the power balancing board is connected to the control board;

[0010] The power balancing board uploads the working status to the control board through the communication interface, and receives the balancing instructions issued by the control board through the communication interface, and balances the remaining battery modules and new battery modules of the vehicle according to the balancing instructions. Furthermore, the power balancing board is provided with a front-stage voltage conversion module, a rear-stage closed-loop control module, a voltage acquisition module, a current acquisition module, a communication module and a main control module;

[0011] The main control module is connected to the front-stage voltage conversion module, the rear-stage closed-loop control module, the voltage acquisition module, the current acquisition module and the communication module;

[0012] The input side of the front-stage voltage conversion module is connected to the remaining battery modules of the whole vehicle, the output side of the front-stage voltage conversion module is connected to the input side of the rear-stage closed-loop control module, and the output side of the rear-stage closed-loop control module is connected to the new battery module; the controlled side of the front-stage voltage conversion module and the controlled side of the rear-stage closed-loop control module are both connected to the main control module; the voltage acquisition module collects the voltage of the remaining battery modules and the new battery modules of the whole vehicle, and provides them to the main control module; the current acquisition module collects the current of the remaining battery modules and the new battery modules of the whole vehicle, and provides them to the main control module; the communication module is connected to the control board through the communication interface.

[0013] Furthermore, the front-stage voltage conversion module includes a voltage transformation unit, a resonance network unit, a switch network unit and a switch isolation control unit;

[0014] The switch network unit comprises a primary side switch network unit and a secondary side switch network unit;

[0015] The resonance unit includes a primary side resonance unit and a secondary side resonance unit;

[0016] The input end of the primary side switch network unit is connected to the remaining battery module of the vehicle, the output end of the primary side switch network is connected to the first end of the primary side resonance unit, the second end of the primary side resonance unit is connected to the primary side of the transformer unit, the secondary side resonance unit of the transformer unit is connected, the secondary side resonance unit is connected to the input end of the secondary side switch network unit, and the output end of the secondary side switch network unit is connected to the post-stage closed-loop control module. Further, the primary side switch network unit includes MOS tube Q1, MOS tube Q2, MOS tube Q3, MOS tube Q4, capacitor Ci1, capacitor Ci2, capacitor Ci3, capacitor Ci4;

[0017] The primary side resonant unit includes capacitor Cr1, inductor Lr, and inductor Lm;

[0018] The transformer unit includes a transformer T;

[0019] The secondary side resonant unit includes a capacitor Cr2;

[0020] The secondary side switch unit includes MOS transistor Q5, MOS transistor Q6, MOS transistor Q7, MOS transistor Q8, capacitor Ci5, capacitor Ci6, capacitor Ci7, and capacitor Ci8;

[0021] The remaining battery modules of the vehicle are connected in parallel with capacitor C H , and the positive electrode of the remaining battery module of the whole vehicle is connected to the drain of the MOS tube Q1 and the drain of the MOS tube Q2, and the negative electrode of the remaining battery module of the whole vehicle is connected to the source of the MOS tube Q3 and the source of the MOS tube Q4;

[0022] The source of the MOS transistor Q1 is connected to the drain of the MOS transistor Q3 and to the first end of the capacitor Cr1. The first end of the capacitor Cr1 is connected to the first end of the inductor Lr. The second end of the inductor Lr is connected to the first end of the inductor Lm and the first end of the primary side of the transformer T.

[0023] The source of the MOS transistor Q2 is connected to the drain of the MOS transistor Q4, and is connected to the second end of the inductor Lm and the second end of the primary side of the transformer T;

[0024] Capacitor Ci1 is connected in parallel between the source and drain of MOS tube Q1, capacitor Ci2 is connected in parallel between the source and drain of MOS tube Q2, capacitor Ci3 is connected in parallel between the drain and source of MOS tube Q3, and capacitor Ci4 is connected in parallel between the drain and source of MOS tube Q4;

[0025] The first end of the secondary side of the transformer T is connected to the first end of the capacitor Cr2, the second end of the capacitor Cr2 is connected to the source of the MOS transistor Q6 and the drain of the MOS transistor Q8, and the second end of the secondary side of the transformer T is connected to the source of the MOS transistor Q5 and the drain of the MOS transistor Q7;

[0026] The drain of the MOS transistor Q5 is connected to the drain of the MOS transistor Q6 and is connected to the first resonance output terminal, and the source of the MOS transistor Q7 is connected to the source of the MOS transistor Q8 and is connected to the second resonance output terminal;

[0027] Capacitor Ci5 is connected in parallel between the source and drain of MOS tube Q5, capacitor Ci6 is connected in parallel between the source and drain of MOS tube Q6, capacitor Ci7 is connected in parallel between the drain and source of MOS tube Q7, and capacitor Ci8 is connected in parallel between the drain and source of MOS tube Q8;

[0028] The first resonant output terminal and the second resonant output terminal are connected in parallel with a capacitor C M , and the first resonant output end and the second resonant output end are connected to the post-stage closed-loop control module;

[0029] The gate of the MOS transistor Q1, the gate of the MOS transistor Q2, the gate of the MOS transistor Q3, the gate of the MOS transistor Q4, the gate of the MOS transistor Q5, the gate of the MOS transistor Q6, the gate of the MOS transistor Q7, and the gate of the MOS transistor Q8 are all connected to the switch isolation control unit, and the other end of the switch isolation control unit is connected to the control module;

[0030] The switch isolation control unit receives the switch control signal of the main control module, and generates a drive signal after isolation and power discharge to control the on and off of MOS tubes Q1, MOS tube Q2, MOS tube Q3, MOS tube Q4, MOS tube Q5, MOS tube Q6, MOS tube Q7, and MOS tube Q8.

[0031] Furthermore, the post-stage closed-loop control module includes a main control unit, a switch control unit, a closed-loop switch unit and a current sampling unit;

[0032] The main control unit is connected to the switch control unit and the current sampling unit, and the current sampling unit, the switch control unit and the closed-loop switch unit are all connected;

[0033] The current sampling unit collects the current of the closed-loop switch unit and provides it to the main control unit;

[0034] The main control unit compares the current value collected by the current sampling unit with the pre-stored setting value, and then generates a modulation signal after calculation using the fuzzy PI algorithm and sends it to the switch control unit;

[0035] The switch control unit receives the modulation signal from the main control unit, generates a drive signal after power amplification, and drives the closed-loop switch unit to work.

[0036] Furthermore, the closed-loop switch unit includes a MOS tube Q9, a MOS tube Q10, an inductor Ls and a capacitor C LThe drain of MOS tube Q9 is connected to the first end of the resonant output, the source of MOS tube Q9 is connected to the drain of MOS tube Q10 and the first end of inductor Ls, and the second end of inductor Ls is connected to capacitor C L First end connection;

[0037] The source of MOS tube Q10 and the second end of the resonant output and capacitor C L The second end is connected;

[0038] Capacitor C L Connected in parallel with the new battery module, and the capacitor C L The first end is connected to the positive electrode of the new battery module, and the capacitor C L The second end is connected to the negative electrode of the new battery module;

[0039] The current sampling unit collects the current of the inductor Ls and provides it to the main control unit to generate a modulation signal;

[0040] After receiving the modulation signal from the main control unit, the switch control unit generates a driving signal after power amplification, and drives the MOS tube Q9 and the MOS tube Q10 to be turned on and off through the driving signal.

[0041] In a second aspect, the present invention provides a method for load balancing of a power battery module with a wide voltage range, comprising the following steps:

[0042] S1. Analyze the forward and reverse working states of the front-stage voltage conversion module using fundamental wave analysis;

[0043] S2. Use soft start mode to control the duty ratio of the two MOS tubes of the subsequent closed-loop control module when starting;

[0044] S3. Use a pulse charging-based balancing strategy to control the power balancing process of the new battery module and the remaining battery modules of the vehicle.

[0045] Furthermore, the specific steps of step S1 are as follows:

[0046] S11. Set the forward working state of the front-stage voltage conversion module to transfer power from the remaining battery module of the vehicle on the primary side of the transformer T to the new battery module on the secondary side of the transformer T, and the new battery module operates in an uncontrolled rectification mode;

[0047] S12. The reverse working state of the front voltage conversion module is set to transfer power from the new battery module on the secondary side of the transformer T to the remaining battery modules of the vehicle on the primary side of the transformer T, and the remaining battery modules of the vehicle operate in an uncontrolled rectification mode;

[0048] S13. Construct the equivalent circuit diagram of the front-stage voltage conversion module in the forward and reverse working states respectively;

[0049] S14. Calculate the forward first resonant frequency and the forward second resonant frequency of the front-stage voltage conversion module based on the equivalent circuit diagram of the forward working state, and set the frequency range between the forward first resonant frequency and the forward second resonant frequency as the switching frequency of each MOS tube of the primary-side switch network unit and the secondary-side switch network unit;

[0050] S15. Calculate the reverse first resonant frequency and the reverse second resonant frequency of the front-stage voltage conversion module based on the equivalent circuit diagram of the reverse working state, and set the frequency range between the reverse first resonant frequency and the reverse second resonant frequency as the switching frequency of each MOS tube of the primary side switch network unit and the secondary side switch network unit;

[0051] The specific steps of step S2 are as follows:

[0052] S21. Select one of the two MOS tubes in the post-stage closed-loop control module as a master switch tube and the other as a slave switch tube;

[0053] S22. Start soft start, so that the duty cycle of the slave switch tube complements the duty cycle of the master switch tube;

[0054] S23. Set the duty cycle of the main control switch tube to increase from zero according to the set step size;

[0055] S24. Determine whether the duty cycle of the master switch tube and the slave switch tube reaches the set threshold;

[0056] If so, the soft start ends and the process goes to step S3;

[0057] If not, the duty cycle of the main control switch tube continues to increase according to the set step size, and the process returns to step S24.

[0058] Furthermore, the specific steps of step S3 are as follows:

[0059] S31. Obtain the working status, determine the balancing direction of the remaining battery modules and the new battery modules of the vehicle according to the working status, use the high-power battery module as the main balancing party, and use the low-power battery module as the slave balancing party; S32. Divide the process of power balancing from the balancing party in the main balancing direction into a charging stage, a discharging stage, and a static stage;

[0060] S33. Charging phase starts;

[0061] S34. Control the battery pack of the master balancer to apply a positive current pulse of a set amplitude to the slave balancer in the balance direction with the high level time of the duty cycle as the duration, and detect whether the charging cut-off condition is met during the low level time of the duty cycle;

[0062] If yes, go to step S35;

[0063] If not, enter the next duty cycle and return to step S34;

[0064] S35. Discharge phase starts;

[0065] S36. Control the battery pack of the main balancing party to apply a set number opposite to the charging stage, and set the duty cycle of the negative current pulse to depolarize the battery pack of the slave balancing party;

[0066] S37. The static phase starts;

[0067] S38. Collect the voltage difference between the master balancing battery group and the slave balancing battery group within the set static time, and determine whether the voltage difference is less than the set first voltage threshold;

[0068] If so, equilibrium ends;

[0069] If not, the set amplitudes of the positive current pulse and the negative current pulse are reduced according to the set ratio, and the process returns to step S33.

[0070] Furthermore, the charging cut-off condition in step S34 is that the operating voltage during charging reaches the charging cut-off voltage or the voltage difference between the master balancing battery group and the slave balancing battery group during the low level time of the duty cycle is less than a set second voltage threshold.

[0071] The beneficial effects of the present invention are:

[0072] The wide voltage range power battery module load balancing system and method provided by the present invention can achieve balancing of a new battery module with the remaining battery modules of the whole vehicle without the need for external charging and discharging equipment, while taking into account convenience and avoiding waste of energy charged into the battery; the present invention adopts an active balancing method, and compared with the traditional passive balancing method, the battery energy will not be dissipated in vain on the resistor, and the energy utilization rate is higher; the balancing topology of the present invention solves the problem of a wide input voltage range, and is relatively more reliable and relatively simpler in design than the traditional method.

[0073] In addition, the invention has a reliable design principle, a simple structure and a very broad application prospect.

[0074] It can be seen that compared with the prior art, the present invention has outstanding substantive features and significant progress, and the beneficial effects of its implementation are also obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0076] Figure 1 It is an overall schematic diagram of the wide voltage range power battery module load balancing system of the present invention.

[0077] Figure 2 It is a connection diagram of various modules of the power balancing board of the power battery module load balancing system within the voltage range of the present invention.

[0078] Figure 3 It is a circuit diagram of a front-stage voltage conversion module of a power battery module load balancing system within a voltage range of the present invention.

[0079] Figure 4 It is an equivalent circuit diagram of the forward working state of the front-stage voltage conversion module of the present invention.

[0080] Figure 5 It is an equivalent circuit diagram of the reverse working state of the front-stage voltage conversion module of the present invention.

[0081] Figure 6 It is a flow chart of the load balancing method of a power battery module with a wide voltage range according to the present invention.

[0082] Figure 7 It is a schematic diagram of the current curve of the balancing process in the load balancing method of the power battery module with a wide voltage range of the present invention. DETAILED DESCRIPTION

[0083] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0084] In order to meet the voltage range of the vehicle battery module of most models and improve the applicability of the device, it was found through actual investigation that the voltage range is approximately between 200V and 400V. The wide voltage range brings certain difficulties to the design of the balancing topology. At present, variable mode control, two-stage cascade and variable topology control are mainly used to broaden the voltage input range. Among them, the parameter design of variable mode control is relatively complex, the flexible switching of variable topology control is relatively difficult and the reliability is low, so a two-stage cascade topology is adopted. The balancing topology adopted in this application is as follows Figure 3 As shown, the front stage is a front stage voltage conversion module as a bidirectional full-bridge CLLC resonant circuit, and the rear stage is a rear stage closed-loop control module as a bidirectional Buck / Boost circuit.

[0085] See also Figure 1The figure shows a specific implementation of a wide voltage range power battery module load balancing system, including a new battery module, a remaining battery module of the vehicle, a power balancing board and a control board;

[0086] The power balancing board is provided with a front side interface, a rear side interface and a communication interface;

[0087] The front interface of the power balancing board is connected to the remaining battery modules of the vehicle, and the rear interface of the power balancing board is connected to the new battery module;

[0088] The communication interface of the power balancing board is connected to the control board; the communication interface adopts the CAN communication interface;

[0089] The power balancing board uploads the working status to the control board through the communication interface, and receives the balancing instruction issued by the control board through the communication interface, and balances the remaining battery modules and new battery modules of the vehicle according to the balancing instruction. Figure 2 As shown, the power balancing board is provided with a front-stage voltage conversion module, a rear-stage closed-loop control module, a voltage acquisition module, a current acquisition module, a communication module and a main control module;

[0090] The main control module is connected to the front-stage voltage conversion module, the rear-stage closed-loop control module, the voltage acquisition module, the current acquisition module and the communication module;

[0091] The input side of the front-stage voltage conversion module is connected to the remaining battery modules of the vehicle, the output side of the front-stage voltage conversion module is connected to the input side of the rear-stage closed-loop control module, and the output side of the rear-stage closed-loop control module is connected to the new battery module; the controlled side of the front-stage voltage conversion module and the controlled side of the rear-stage closed-loop control module are both connected to the main control module; the voltage acquisition module collects the voltage of the remaining battery modules and the new battery modules of the vehicle and provides them to the main control module; the current acquisition module collects the current of the remaining battery modules and the new battery modules of the vehicle and provides them to the main control module; the communication module is connected to the control board through the communication interface;

[0092] The front-stage voltage conversion module includes a voltage transformation unit, a resonant network unit, a switch network unit and a switch isolation control unit;

[0093] The switch network unit comprises a primary side switch network unit and a secondary side switch network unit;

[0094] The resonance unit includes a primary side resonance unit and a secondary side resonance unit;

[0095] The input end of the primary side switch network unit is connected to the remaining battery module of the whole vehicle, the output end of the primary side switch network is connected to the first end of the primary side resonance unit, the second end of the primary side resonance unit is connected to the primary side of the transformer unit, the secondary side resonance unit of the transformer unit is connected, the secondary side resonance unit is connected to the input end of the secondary side switch network unit, and the output end of the secondary side switch network unit is connected to the post-stage closed-loop control module; Figure 3 As shown, the primary side switch network unit includes MOS transistor Q1, MOS transistor Q2, MOS transistor Q3, MOS transistor Q4, capacitor Ci1, capacitor Ci2, capacitor Ci3, capacitor Ci4;

[0096] The primary side resonant unit includes capacitor Cr1, inductor Lr, and inductor Lm;

[0097] The transformer unit includes a transformer T;

[0098] The secondary side resonant unit includes a capacitor Cr2;

[0099] The secondary side switch unit includes MOS transistor Q5, MOS transistor Q6, MOS transistor Q7, MOS transistor Q8, capacitor Ci5, capacitor Ci6, capacitor Ci7, and capacitor Ci8;

[0100] The remaining battery modules of the vehicle are connected in parallel with capacitor C H , and the positive electrode of the remaining battery module of the whole vehicle is connected to the drain of the MOS tube Q1 and the drain of the MOS tube Q2, and the negative electrode of the remaining battery module of the whole vehicle is connected to the source of the MOS tube Q3 and the source of the MOS tube Q4;

[0101] The source of the MOS transistor Q1 is connected to the drain of the MOS transistor Q3 and to the first end of the capacitor Cr1. The first end of the capacitor Cr1 is connected to the first end of the inductor Lr. The second end of the inductor Lr is connected to the first end of the inductor Lm and the first end of the primary side of the transformer T.

[0102] The source of the MOS transistor Q2 is connected to the drain of the MOS transistor Q4, and is connected to the second end of the inductor Lm and the second end of the primary side of the transformer T;

[0103] Capacitor Ci1 is connected in parallel between the source and drain of MOS tube Q1, capacitor Ci2 is connected in parallel between the source and drain of MOS tube Q2, capacitor Ci3 is connected in parallel between the drain and source of MOS tube Q3, and capacitor Ci4 is connected in parallel between the drain and source of MOS tube Q4;

[0104] The first end of the secondary side of the transformer T is connected to the first end of the capacitor Cr2, the second end of the capacitor Cr2 is connected to the source of the MOS transistor Q6 and the drain of the MOS transistor Q8, and the second end of the secondary side of the transformer T is connected to the source of the MOS transistor Q5 and the drain of the MOS transistor Q7;

[0105] The drain of the MOS transistor Q5 is connected to the drain of the MOS transistor Q6 and is connected to the first resonance output terminal, and the source of the MOS transistor Q7 is connected to the source of the MOS transistor Q8 and is connected to the second resonance output terminal;

[0106] Capacitor Ci5 is connected in parallel between the source and drain of MOS tube Q5, capacitor Ci6 is connected in parallel between the source and drain of MOS tube Q6, capacitor Ci7 is connected in parallel between the drain and source of MOS tube Q7, and capacitor Ci8 is connected in parallel between the drain and source of MOS tube Q8;

[0107] The first resonant output terminal and the second resonant output terminal are connected in parallel with a capacitor C M , and the first resonant output end and the second resonant output end are connected to the post-stage closed-loop control module;

[0108] The gate of the MOS transistor Q1, the gate of the MOS transistor Q2, the gate of the MOS transistor Q3, the gate of the MOS transistor Q4, the gate of the MOS transistor Q5, the gate of the MOS transistor Q6, the gate of the MOS transistor Q7, and the gate of the MOS transistor Q8 are all connected to the switch isolation control unit, and the other end of the switch isolation control unit is connected to the control module;

[0109] The resonant network consists of the resonant inductor L r , transformer excitation inductance L m , the resonant capacitor C on the primary side r1 and the resonant capacitor C on the secondary side r2 Composition, at the same time C r1 and C r2 It also has the function of preventing magnetic bias;

[0110] The post-stage closed-loop control module includes a main control unit, a switch control unit, a closed-loop switch unit and a current sampling unit;

[0111] The main control unit is connected to the switch control unit and the current sampling unit, and the current sampling unit, the switch control unit and the closed-loop switch unit are all connected;

[0112] The current sampling unit collects the current of the closed-loop switch unit and provides it to the main control unit;

[0113] The main control unit compares the current value collected by the current sampling unit with the pre-stored setting value, and then generates a modulation signal after calculation using the fuzzy PI algorithm and sends it to the switch control unit;

[0114] The switch control unit receives the modulation signal from the main control unit, generates a drive signal after power amplification, and drives the closed-loop switch unit to work;

[0115] The switch isolation control unit receives the switch control signal of the main control module, and generates a drive signal after isolation and power discharge to control the on and off of MOS tubes Q1, MOS tube Q2, MOS tube Q3, MOS tube Q4, MOS tube Q5, MOS tube Q6, MOS tube Q7, and MOS tube Q8;

[0116] The closed-loop switch unit includes MOS tube Q9, MOS tube Q10, inductor Ls and capacitor C L ;

[0117] The drain of MOS tube Q9 is connected to the first end of the resonant output, the source of MOS tube Q9 is connected to the drain of MOS tube Q10 and the first end of inductor Ls, and the second end of inductor Ls is connected to capacitor C L First end connection;

[0118] The source of MOS tube Q10 and the second end of the resonant output and capacitor C L The second end is connected;

[0119] Capacitor C L Connected in parallel with the new battery module, and the capacitor C L The first end is connected to the positive electrode of the new battery module, and the capacitor C L The second end is connected to the negative electrode of the new battery module;

[0120] The current sampling unit collects the current of the inductor Ls and provides it to the main control unit to generate a modulation signal;

[0121] After receiving the modulation signal from the main control unit, the switch control unit generates a driving signal after power amplification, and drives the MOS tube Q9 and the MOS tube Q10 to be turned on and off through the driving signal.

[0122] The following is an embodiment of a method for load balancing a power battery module with a wide voltage range provided in an embodiment of the present disclosure. This method and the load balancing system for a power battery module with a wide voltage range of the above-mentioned embodiments belong to the same inventive concept. For details not described in detail in the embodiment of the method for load balancing a power battery module with a wide voltage range, reference can be made to the embodiment of the load balancing system for a wide voltage range of the above-mentioned power battery module.

[0123] like Figure 6 As shown, the method comprises the following steps:

[0124] S1. Analyze the forward and reverse working states of the front-stage voltage conversion module using fundamental wave analysis;

[0125] S2. Use soft start mode to control the duty ratio of the two MOS tubes of the subsequent closed-loop control module when starting;

[0126] S3. Use a pulse charging-based balancing strategy to control the power balancing process of the new battery module and the remaining battery modules of the vehicle.

[0127] In this embodiment, the specific steps of step S1 are as follows:

[0128] S11. Set the forward working state of the front-stage voltage conversion module to transfer power from the remaining battery module of the vehicle on the primary side of the transformer T to the new battery module on the secondary side of the transformer T, and the new battery module operates in an uncontrolled rectification mode;

[0129] S12. The reverse working state of the front voltage conversion module is set to transfer power from the new battery module on the secondary side of the transformer T to the remaining battery modules of the vehicle on the primary side of the transformer T, and the remaining battery modules of the vehicle operate in an uncontrolled rectification mode;

[0130] S13. Construct the equivalent circuit diagram of the front-stage voltage conversion module in the forward and reverse working states respectively; the forward working state equivalent circuit diagram is shown in 4, and the reverse working state equivalent circuit diagram is shown in Figure 5 As shown;

[0131] S14. Calculate the forward first resonant frequency and the forward second resonant frequency of the front-stage voltage conversion module based on the equivalent circuit diagram of the forward working state, and set the frequency range between the forward first resonant frequency and the forward second resonant frequency as the switching frequency of each MOS tube of the primary-side switch network unit and the secondary-side switch network unit;

[0132] S15. Calculate the reverse first resonant frequency and the reverse second resonant frequency of the front-stage voltage conversion module based on the equivalent circuit diagram of the reverse working state, and set the frequency range between the reverse first resonant frequency and the reverse second resonant frequency as the switching frequency of each MOS tube of the primary side switch network unit and the secondary side switch network unit;

[0133] The analysis methods of the front-stage voltage conversion module mainly include: time domain analysis method and fundamental wave approximation analysis method. Although the time domain analysis method can obtain accurate voltage and current waveform expressions and gain curves, the secondary side of the front-stage voltage conversion module contains a resonant capacitor. In the process of transferring energy from the secondary side to the primary side, the secondary side voltage of the transformer T is equal to the sum of the voltage of the resonant capacitor and the voltage of the secondary side output capacitor, which is a non-constant value, resulting in a nonlinear increase in the excitation current. This brings great difficulties to the time domain analysis. Therefore, this application adopts the fundamental wave analysis method, which contains 8 modes in both forward and reverse operation. The equivalent model in forward operation is as follows: Figure 4 As shown, the equivalent model when working in reverse is as follows Figure 5As shown in the figure, the front-stage voltage conversion module using the bidirectional full-bridge CLLC resonant converter has one more resonant capacitor than the bidirectional full-bridge LLC resonant converter. This resonant capacitor will also participate in the resonance, causing the resonant frequency to change. Similar to the LLC resonant circuit, the front-stage voltage conversion module also contains two resonant frequencies. The resonant capacitor Cr1, the resonant inductor Lr and the transformer excitation inductor Lm on the primary side form the forward first resonant frequency ff1, and its magnitude is: The second forward resonant frequency ff2 is approximately equal to the resonant frequency formed by the equivalent capacitance formed by the primary side resonant capacitor Cr1 and the secondary side resonant capacitor Cr2 and the resonant inductor Lr, and its magnitude is approximately: The reverse first resonant frequency fr1 and the reverse second resonant frequency fr2 are similar; according to the magnitude relationship between the switching frequency fs and the two resonant frequencies, they can be divided into three working areas, namely fs <f f1 、f f1 <fs<f f2 and fs>f f2 ; When fs <f f1 When the switch tube can only achieve zero current shutdown (Zero Current Switching, ZCS); when f f1 <fs<f f2 When fs>f f2 Although the primary switch can achieve zero voltage switching (ZVS), the secondary switch has a reverse recovery problem. f1 <fs<f f2 The regional switching loss is relatively small, so this is the working area selected for this application;

[0134] The specific steps of step S2 are as follows:

[0135] S21. Select one of the two MOS tubes in the post-stage closed-loop control module as a master switch tube and the other as a slave switch tube;

[0136] S22. Start soft start, so that the duty cycle of the slave switch tube complements the duty cycle of the master switch tube;

[0137] S23. Set the duty cycle of the main control switch tube to increase from zero according to the set step size;

[0138] S24. Determine whether the duty cycle of the master switch tube and the slave switch tube reaches the set threshold;

[0139] If so, the soft start ends and the process goes to step S3;

[0140] If not, the duty cycle of the main control switch tube continues to increase according to the set step length, and the process returns to step S24;

[0141] like Figure 3 As shown in the figure, the bidirectional Buck / Boost circuit mainly consists of MOS tube Q9 and MOS tube Q10 as switch tubes, inductor Ls and capacitor C L The soft start method is used to reduce the voltage spike caused by parasitic inductance of the switch tube at startup. The specific method is: at startup, the duty cycle of the main control switch tube starts from zero and gradually increases, and the other switch tube applies a complementary drive signal until both reach a given duty cycle. The soft start ends and the bidirectional Buck / Boost works normally. In this way, synchronous rectification can be achieved during the soft start process, which protects the switch tube and reduces losses;

[0142] The specific steps of step S3 are as follows:

[0143] S31. Obtain the working status, determine the balancing direction of the remaining battery modules and the new battery modules of the vehicle according to the working status, use the high-power battery module as the main balancing party, and use the low-power battery module as the slave balancing party;

[0144] S32. The process of performing power balancing from the balancing side in the main balancing direction is divided into the following steps: Figure 7 The charging phase, discharging phase and rest phase shown;

[0145] S33. Charging phase starts;

[0146] S34. Control the battery pack of the master balancer to apply a positive current pulse of a set amplitude to the slave balancer in the balance direction with the high level time of the duty cycle as the duration, and detect whether the charging cut-off condition is met during the low level time of the duty cycle;

[0147] If yes, go to step S35;

[0148] If not, enter the next duty cycle and return to step S34;

[0149] S35. Discharge phase starts;

[0150] S36. Control the battery pack of the main balancing party to apply a set number opposite to the charging stage, and set the duty cycle of the negative current pulse to depolarize the battery pack of the slave balancing party;

[0151] S37. The static phase starts;

[0152] S38. Collect the voltage difference between the master balancing battery group and the slave balancing battery group within the set static time, and determine whether the voltage difference is less than the set first voltage threshold;

[0153] If so, equilibrium ends;

[0154] If not, reduce the set amplitudes of the positive current pulse and the negative current pulse according to the set ratio, and return to step S33;

[0155] In step S34, the charging cut-off condition is that the working voltage during charging reaches the charging cut-off voltage or the voltage difference between the master balancing battery group and the slave balancing battery group during the low level time of the duty cycle is less than the set second voltage threshold;

[0156] The pulse charging method based balancing strategy was selected from five aspects: charging time, efficiency, control complexity, battery cycle life, and the number of electrical quantities to be measured.

[0157] Figure 4 The current curve in the balancing process, the balancing strategy used in the embodiment of the present invention is divided into three stages: the first stage uses a maintenance time of T on The module is charged and balanced with a positive current pulse, and the voltage is detected at the end of each cycle. This stage ends when the charging cut-off condition is met; the charging cut-off condition is that the working voltage during charging reaches the charging cut-off voltage or the voltage difference measured in the charging stop stage is less than the set value β1; the second stage is the discharge depolarization stage, and applying a pulse opposite to the charging process can accelerate the depolarization of the battery. However, if the duty cycle is too small, the depolarization effect is too weak, and if the duty cycle is too large, it will affect the balancing efficiency; combined with relevant literature and multiple simulation results, two negative current pulses with the same size as the positive current pulse and a duty cycle of 20% are applied in this stage to accelerate the depolarization of the battery; the third stage is the static stage, and the voltage measured at the end of this stage is approximately regarded as the open circuit voltage. If the voltage difference at this time is less than the set value, it is considered that the consistency has met the requirements and the balancing is over; if the conditions are not met, it will continue to be executed from the first stage, but the amplitude of the positive and negative current pulses should be reduced until the voltage difference measured in the static stage is less than the set value β2, and the balancing is over.

[0158] It should be understood that the order of execution of the steps in the above embodiment does not mean that the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0159] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. A wide voltage range power battery module load balancing system, characterized in that: Including new battery modules, remaining battery modules of the vehicle, power balancing boards and control boards; The power balancing board is provided with a front side interface, a rear side interface and a communication interface; The front interface of the power balancing board is connected to the remaining battery modules of the vehicle, and the rear interface of the power balancing board is connected to the new battery module; The communication interface of the power balancing board is connected to the control board; The power balancing board uploads the working status to the control board through the communication interface, and receives the balancing instructions issued by the control board through the communication interface, and balances the remaining battery modules and new battery modules of the whole vehicle according to the balancing instructions.

2. The wide voltage range power battery module load balancing system according to claim 1, characterized in that: The power balancing board is provided with a front-stage voltage conversion module, a rear-stage closed-loop control module, a voltage acquisition module, a current acquisition module, a communication module and a main control module; The main control module is connected to the front-stage voltage conversion module, the rear-stage closed-loop control module, the voltage acquisition module, the current acquisition module and the communication module; The input side of the front-stage voltage conversion module is connected to the remaining battery modules of the vehicle, the output side of the front-stage voltage conversion module is connected to the input side of the rear-stage closed-loop control module, and the output side of the rear-stage closed-loop control module is connected to the new battery module; the controlled side of the front-stage voltage conversion module and the controlled side of the rear-stage closed-loop control module are both connected to the main control module; The voltage acquisition module collects the voltage of the remaining battery modules and the new battery modules of the whole vehicle, and provides it to the main control module; the current acquisition module collects the current of the remaining battery modules and the new battery modules of the whole vehicle, and provides it to the main control module; The communication module is connected to the control board via a communication interface.

3. The wide voltage range power battery module load balancing system according to claim 2, characterized in that: The front-stage voltage conversion module includes a voltage transformation unit, a resonant network unit, a switch network unit and a switch isolation control unit; The switch network unit comprises a primary side switch network unit and a secondary side switch network unit; The resonance unit includes a primary side resonance unit and a secondary side resonance unit; The input end of the primary side switch network unit is connected to the remaining battery modules of the whole vehicle, the output end of the primary side switch network is connected to the first end of the primary side resonance unit, the second end of the primary side resonance unit is connected to the primary side of the transformer unit, the secondary side resonance unit of the secondary side of the transformer unit is connected, the secondary side resonance unit is connected to the input end of the secondary side switch network unit, and the output end of the secondary side switch network unit is connected to the post-stage closed-loop control module.

4. The wide voltage range power battery module load balancing system according to claim 3, characterized in that: The primary side switch network unit includes MOS tube Q1, MOS tube Q2, MOS tube Q3, MOS tube Q4, capacitor Ci1, capacitor Ci2, capacitor Ci3, capacitor Ci4; The primary side resonant unit includes capacitor Cr1, inductor Lr, and inductor Lm; The transformer unit includes a transformer T; The secondary side resonant unit includes a capacitor Cr2; The secondary side switch unit includes MOS transistor Q5, MOS transistor Q6, MOS transistor Q7, MOS transistor Q8, capacitor Ci5, capacitor Ci6, capacitor Ci7, and capacitor Ci8; The remaining battery modules of the vehicle are connected in parallel with capacitor C H , and the positive electrode of the remaining battery module of the whole vehicle is connected to the drain of the MOS tube Q1 and the drain of the MOS tube Q2, and the negative electrode of the remaining battery module of the whole vehicle is connected to the source of the MOS tube Q3 and the source of the MOS tube Q4; The source of the MOS transistor Q1 is connected to the drain of the MOS transistor Q3 and to the first end of the capacitor Cr1. The first end of the capacitor Cr1 is connected to the first end of the inductor Lr. The second end of the inductor Lr is connected to the first end of the inductor Lm and the first end of the primary side of the transformer T. The source of the MOS transistor Q2 is connected to the drain of the MOS transistor Q4, and is connected to the second end of the inductor Lm and the second end of the primary side of the transformer T; Capacitor Ci1 is connected in parallel between the source and drain of MOS tube Q1, capacitor Ci2 is connected in parallel between the source and drain of MOS tube Q2, capacitor Ci3 is connected in parallel between the drain and source of MOS tube Q3, and capacitor Ci4 is connected in parallel between the drain and source of MOS tube Q4; The first end of the secondary side of the transformer T is connected to the first end of the capacitor Cr2, the second end of the capacitor Cr2 is connected to the source of the MOS transistor Q6 and the drain of the MOS transistor Q8, and the second end of the secondary side of the transformer T is connected to the source of the MOS transistor Q5 and the drain of the MOS transistor Q7; The drain of the MOS transistor Q5 is connected to the drain of the MOS transistor Q6 and is connected to the first resonance output terminal, and the source of the MOS transistor Q7 is connected to the source of the MOS transistor Q8 and is connected to the second resonance output terminal; Capacitor Ci5 is connected in parallel between the source and drain of MOS tube Q5, capacitor Ci6 is connected in parallel between the source and drain of MOS tube Q6, capacitor Ci7 is connected in parallel between the drain and source of MOS tube Q7, and capacitor Ci8 is connected in parallel between the drain and source of MOS tube Q8; The first resonant output terminal and the second resonant output terminal are connected in parallel with a capacitor C M , and the first resonant output end and the second resonant output end are connected to the post-stage closed-loop control module; The gate of the MOS transistor Q1, the gate of the MOS transistor Q2, the gate of the MOS transistor Q3, the gate of the MOS transistor Q4, the gate of the MOS transistor Q5, the gate of the MOS transistor Q6, the gate of the MOS transistor Q7, and the gate of the MOS transistor Q8 are all connected to the switch isolation control unit, and the other end of the switch isolation control unit is connected to the control module; The switch isolation control unit receives the switch control signal of the main control module, and generates a drive signal after isolation and power discharge to control the on and off of MOS tubes Q1, MOS tube Q2, MOS tube Q3, MOS tube Q4, MOS tube Q5, MOS tube Q6, MOS tube Q7, and MOS tube Q8.

5. The wide voltage range power battery module load balancing system according to claim 4, characterized in that: The post-stage closed-loop control module includes a main control unit, a switch control unit, a closed-loop switch unit and a current sampling unit; The main control unit is connected to the switch control unit and the current sampling unit, and the current sampling unit, the switch control unit and the closed-loop switch unit are all connected; The current sampling unit collects the current of the closed-loop switch unit and provides it to the main control unit; The main control unit compares the current value collected by the current sampling unit with the pre-saved set value, and then generates a modulation signal after calculation using the fuzzy PI algorithm and sends it to the switch control unit; the switch control unit receives the modulation signal from the main control unit, generates a drive signal after power amplification, and drives the closed-loop switch unit to work.

6. The wide voltage range power battery module load balancing system according to claim 5, characterized in that: The closed-loop switch unit includes MOS tube Q9, MOS tube Q10, inductor Ls and capacitor C L ; The drain of MOS tube Q9 is connected to the first end of the resonant output, the source of MOS tube Q9 is connected to the drain of MOS tube Q10 and the first end of inductor Ls, and the second end of inductor Ls is connected to capacitor C L First end connection; The source of MOS tube Q10 and the second end of the resonant output and capacitor C L The second end is connected; Capacitor C L Connect the new battery module in parallel with the capacitor C L The first end is connected to the positive electrode of the new battery module, and the capacitor C L The second end is connected to the negative electrode of the new battery module; The current sampling unit collects the current of the inductor Ls and provides it to the main control unit to generate a modulation signal; After receiving the modulation signal from the main control unit, the switch control unit generates a driving signal after power amplification, and drives the MOS tube Q9 and the MOS tube Q10 to be turned on and off through the driving signal.

7. A method for load balancing of power battery modules in a wide voltage range, characterized in that: The steps include: S1. Analyze the forward and reverse working states of the front-stage voltage conversion module using fundamental wave analysis; S2. Use soft start mode to control the duty ratio of the two MOS tubes of the subsequent closed-loop control module when starting; S3. Use a pulse charging-based balancing strategy to control the power balancing process of the new battery module and the remaining battery modules of the vehicle.

8. The method for load balancing of power battery modules with a wide voltage range as claimed in claim 7, characterized in that: The specific steps of step S1 are as follows: S11. Set the forward working state of the front-stage voltage conversion module to transfer power from the remaining battery module of the vehicle on the primary side of the transformer T to the new battery module on the secondary side of the transformer T, and the new battery module operates in an uncontrolled rectification mode; S12. The reverse working state of the front voltage conversion module is set to transfer power from the new battery module on the secondary side of the transformer T to the remaining battery modules of the vehicle on the primary side of the transformer T, and the remaining battery modules of the vehicle operate in an uncontrolled rectification mode; S13. Construct the equivalent circuit diagram of the front-stage voltage conversion module in the forward and reverse working states respectively; S14. Calculate the forward first resonant frequency and the forward second resonant frequency of the front-stage voltage conversion module based on the equivalent circuit diagram of the forward working state, and set the frequency range between the forward first resonant frequency and the forward second resonant frequency as the switching frequency of each MOS tube of the primary-side switch network unit and the secondary-side switch network unit; S15. Calculate the reverse first resonant frequency and the reverse second resonant frequency of the front-stage voltage conversion module based on the equivalent circuit diagram of the reverse working state, and set the frequency range between the reverse first resonant frequency and the reverse second resonant frequency as the switching frequency of each MOS tube of the primary side switch network unit and the secondary side switch network unit; The specific steps of step S2 are as follows: S21. Select one of the two MOS tubes in the post-stage closed-loop control module as a master switch tube and the other as a slave switch tube; S22. Start soft start, so that the duty cycle of the slave switch tube complements the duty cycle of the master switch tube; S23. Set the duty cycle of the main control switch tube to increase from zero according to the set step size; S24. Determine whether the duty cycle of the master switch tube and the slave switch tube reaches the set threshold; If so, the soft start ends and the process goes to step S3; If not, the duty cycle of the main control switch tube continues to increase according to the set step size, and the process returns to step S24.

9. The method for load balancing of power battery modules with a wide voltage range as claimed in claim 8, characterized in that: The specific steps of step S3 are as follows: S31. Obtain the working status, determine the balancing direction of the remaining battery modules and the new battery modules of the vehicle according to the working status, use the high-power battery module as the main balancing party, and use the low-power battery module as the slave balancing party; S32. The process of power balancing from the balancing side in the main balancing direction is divided into a charging phase, a discharging phase and a rest phase; S33. Charging phase starts; S34. Control the battery pack of the master balancer to apply a positive current pulse of a set amplitude to the slave balancer in the balance direction with the high level time of the duty cycle as the duration, and detect whether the charging cut-off condition is met during the low level time of the duty cycle; If yes, go to step S35; If not, enter the next duty cycle and return to step S34; S35. Discharge phase starts; S36. Control the battery pack of the main balancing party to apply a set number opposite to the charging stage, and set the duty cycle of the negative current pulse to depolarize the battery pack of the slave balancing party; S37. The static phase starts; S38. Collect the voltage difference between the master balancing battery group and the slave balancing battery group within the set static time, and determine whether the voltage difference is less than the set first voltage threshold; If so, equilibrium ends; If not, the set amplitudes of the positive current pulse and the negative current pulse are reduced according to the set ratio, and the process returns to step S33.

10. The method for load balancing of power battery modules with a wide voltage range as claimed in claim 9, characterized in that: In step S34, the charging cut-off condition is that the operating voltage during charging reaches the charging cut-off voltage or the voltage difference between the master balancing battery group and the slave balancing battery group during the low level time of the duty cycle is less than the set second voltage threshold.

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