A BBU module active balancing circuit considering balanced current

Abstract

The present application relates to a kind of BBU module active equalization circuit considering equalization current, it is related to power supply design field.Circuit includes: MCU, MCU is connected with the equalization current detection module of two-way converter connection, the charge-discharge current detection module connected with BBU module, and the voltage detection of battery in BBU module is carried out to MCU;Auxiliary battery is connected BBU module via two-way converter and selection switch module to provide equalization energy, and two-way converter and selection switch module are electrically connected to MCU.The present application is synchronized to two batteries by two-way converter and carries out energy supplement, to realize the energy equalization of BBU module.Supports MCU to estimate battery current using equalization current, and then carries out SOC estimation, considers the influence of equalization electric current on SOC, and the battery to be equalized according to SOC selection is more accurate.

Description

Technical Field

[0001] This invention relates to the field of power supply design, and more particularly to an active balancing circuit for a BBU module that takes into account balancing current. Background Technology

[0002] Current industry storage systems typically employ a PSU+BBU module for redundant power supply. When the mains power to the data center fails, the storage system can seamlessly switch to the backup battery BBU module if it detects an abnormality in the PSU power supply. The BBU module provides continuous power, ensuring that data in the storage system controller's write cache is written completely and safely to non-volatile media such as HDDs and SSDs, preventing data loss.

[0003] To ensure business continuity of data storage, BBU modules need to have long cycle life and high reliability. However, due to battery manufacturing processes, inconsistencies are inevitable between individual cells, specifically in terms of capacity, internal resistance, and self-discharge rate. As charge and discharge cycles continue, these inconsistencies become increasingly severe, with some cells deteriorating in performance and becoming easier to fully charge. These poor-performing cells act like the short plank of a barrel, limiting the storage capacity of the battery pack. Over time, this directly impacts the cycle life of the battery pack, which in turn severely affects the reliability of the storage system.

[0004] Currently, battery pack energy balancing is an effective technology for improving inconsistencies. Based on different energy transfer methods, balancing circuits can be divided into two types: dissipative balancing (also called passive balancing) and non-dissipative balancing (also called active balancing). Passive balancing uses resistors to discharge the charge from high-voltage batteries, thereby achieving a consistent energy state across the battery pack. While it has a simple control method, it consumes a large amount of energy, has very low energy utilization, slow balancing speed, and affects the charging speed of the battery pack. Active balancing transfers excess charge from high-capacity batteries to low-capacity batteries through energy storage components. Although it has higher energy utilization, the presence of balancing current during the energy transfer process affects the estimation of battery state of charge, thus affecting the judgment of battery pack balancing consistency. Furthermore, balancing speed is also a challenge for active balancing; current active battery pack balancing technologies have complex circuit topologies, slow balancing speeds, and do not consider the impact of balancing current on battery state of charge estimation. Generally, the BBU module of a storage system uses a battery management chip and external resistors to achieve passive charging equalization. It can only achieve charging equalization of the battery pack, and the equalization speed is slow, the energy utilization rate is low, the equalization effect is poor, and there may also be problems such as circuit overheating. Summary of the Invention

[0005] To solve the above-mentioned technical problems, or at least partially solve them, the present invention provides an active balancing circuit for a BBU module that takes into account balancing current.

[0006] This invention provides an active balancing circuit for a BBU module that considers balancing current. The circuit comprises: an MCU connected to a balancing current detection module connected to a bidirectional converter; a BBU module connected to a charge / discharge current detection module; the charge / discharge current detection module electrically connected to the MCU; and the MCU electrically connected to a battery in the BBU module to detect the battery voltage. An auxiliary battery is connected to the BBU module via a bidirectional converter and a selection switch module to provide balancing energy. The bidirectional converter and selection switch module are electrically connected to the MCU.

[0007] The MCU collects the voltage of the batteries in the BBU module, detects the balancing current using the balancing current detection module, and collects the charging and discharging current of the BBU module using the charging and discharging current detection module. It then uses the balancing current and the charging and discharging current of the BBU module to obtain the current of each battery cell in the BBU module. Based on the current and voltage of each battery cell, the extended Kalman algorithm is used to estimate the SOC of each battery cell. The MCU selects the two batteries with the lowest SOC and controls the selection switch module to connect these two batteries to the bidirectional converter for synchronous energy replenishment, thus achieving energy balancing in the BBU module.

[0008] Furthermore, the bidirectional converter includes: a BUCK conversion circuit and a BUCK-BOOST conversion circuit connected to an auxiliary battery; the selection switch module includes: a plurality of intermediate selection switches Blockx for selecting the positive and negative terminals of the bidirectional converter, a switch SW2x-1 for controlling the connection between the battery in the BBU module and the intermediate selection switch Blockx, and a switch SW2x for controlling the connection between the battery in the BBU module and ground. Switches SW2x-1 and SW2x are connected to the corresponding positive terminals of the batteries in the BBU module. The intermediate selection switches Blockx, SW2x-1, and SW2x are controlled to be connected to the MCU.

[0009] Furthermore, the BUCK switching circuit includes: a field-effect transistor S1 whose source is connected to the positive terminal of the auxiliary battery; the drain of the field-effect transistor S1 is connected to an inductor L1; the inductor L1 is connected to the positive plate of a capacitor C1; the negative plate of the capacitor C1 is connected to the negative terminal of the auxiliary battery; the drain of the field-effect transistor S1 is connected to the source of a field-effect transistor S2; the drain of the field-effect transistor S2 is connected to the negative terminal of the auxiliary battery; and the gates of the field-effect transistors S1 and S2 are electrically connected to the MCU.

[0010] Furthermore, the MCU controls the field-effect transistor S1 to be turned on and the field-effect transistor S2 to be turned off, so that the field-effect transistor S1, the inductor L1 and the capacitor C1 form a circuit, which assists the battery in charging the inductor L1 and the capacitor C1; the MCU controls the field-effect transistor S1 to be turned off and the field-effect transistor S2 to be turned on, so that the field-effect transistor S2, the inductor L1 and the battery in the BBU module form a circuit, and the inductor L1 discharges to provide energy to the battery.

[0011] Furthermore, the BUCK-BOOST conversion circuit includes: a field-effect transistor S3 whose source is connected to the positive terminal of the auxiliary battery; the drain of the field-effect transistor S3 is connected to an inductor L2, and the inductor L2 is connected to the negative terminal of the auxiliary battery; the drain of the field-effect transistor S3 is connected to the source of the field-effect transistor S4; the drain of the field-effect transistor S4 is connected to the negative plate of the capacitor C2; the positive plate of the capacitor C2 is connected to the inductor L2; and the gates of the field-effect transistors S3 and S4 are electrically connected to the MCU.

[0012] Furthermore, the MCU controls the field-effect transistor S3 to be turned on and the field-effect transistor S4 to be turned off, so that the field-effect transistor S3 and the inductor L2 form a circuit, which assists the battery in charging the inductor L2; the capacitor C2 and the battery in the BBU module form a circuit, which provides energy to the battery in the BBU module to replenish the battery energy; the MCU controls the field-effect transistor S3 to be turned off and the field-effect transistor S4 to be turned on, so that the inductor L2 and the battery in the BBU module form a circuit, and the inductor L2 discharges to provide energy to the battery.

[0013] Furthermore, the method of using the extended Kalman algorithm to estimate the SOC of each battery cell includes: constructing a first-order Thevenin equivalent circuit model of the battery to obtain the circuit expression of the state variables in the first-order Thevenin equivalent circuit model when the battery is working; combining the battery SOC recursive formula and the circuit expression to obtain the relationship between the state and SOC in the discrete first-order Thevenin equivalent circuit model of the battery; using the battery operating current in the state as the control variable and the battery voltage in the state as the observation variable; and executing the extended Kalman algorithm to estimate the battery SOC.

[0014] Furthermore, the circuit expression for the state variables of the first-order Thevenin equivalent circuit model of the battery includes: V = EV P -IR0,

[0015] The recursive formula for battery SOC is: SOC k+1 =SOC k -i k Δt / Q k i k Given the battery current over k time periods, the battery SOC recursive formula, combined with the circuit expression, yields the discretized formula as follows:

[0016] Vk+1 =f k+1 (SOC k+1 )-V p,k+1 -R0i k+1 ,

[0017] V P,K+1 =V p,k exp(-Δt / R p C p )+R p i k (1-exp(-Δt / R p C p )),

[0018] The resulting state equation and observation equation are shown below:

[0019]

[0020]

[0021] By combining the state equation and observation equation with the extended Kalman algorithm, using the battery operating current in the state as the control variable and the battery voltage in the state as the observation variable, the extended Kalman algorithm is executed to estimate the battery SOC.

[0022] Furthermore, the extended Kalman algorithm for battery SOC estimation includes:

[0023] The state parameter values ​​are initialized based on the battery performance test data;

[0024] Initialize the initial values ​​of the state estimation error covariance P1+, process noise covariance Q, and observation noise covariance R when estimating the battery SOC at time k=1;

[0025] By detecting the initial terminal voltage of the battery, the initial SOC1 of the battery is calculated using the OCV-SOC curve, and the state vector at time k=1 is initialized as X1 = [SOC1, 0]. T ;

[0026] With battery current i k As the control vector for the extended Kalman algorithm, the battery voltage V is used. k As the observation vector of the Extended Kalman Algorithm, the battery state is recursively calculated according to the principle of the Extended Kalman Algorithm to realize the state vector X at time k+1. k+1 The estimation is used to achieve the battery voltage and SOC at time k+1. k+1 Online estimation;

[0027] The state variables and error covariance are updated based on the actual voltage measurements.

[0028] The parameter update is determined based on the error covariance; if no update is needed, the online estimation of lithium-ion battery terminal voltage and SOC is continuously performed.

[0029] If an update is needed, the RLS method is used to update the parameters of the first-order Thevenin equivalent circuit model based on the voltage and current data of the battery at time k+1. Then, after updating the state vector, the online estimation of the lithium-ion battery terminal voltage and SOC is performed.

[0030] Furthermore, the current flowing through each battery cell is calculated as follows:

[0031]

[0032] Among them, I c I is the main circuit current detected by the charge / discharge current detection module. b The equalization current detected by the equalization current detection module.

[0033] The technical solutions provided in the embodiments of the present invention have the following advantages compared with the prior art:

[0034] In this application, energy is transferred from the auxiliary battery to the BBU module via a bidirectional converter and a selection switch. The auxiliary battery serves as the energy source for BBU module balancing. The MCU detects the balancing current of energy transfer in real time through a balancing current detection module and the charging / discharging current flowing through the main circuit in real time through a charging / discharging current detection module. The MCU detects the voltage of the BBU module and estimates the current of each battery cell in the BBU module using the balancing current and charging / discharging current. Considering the impact of the balancing current on the State of Charge (SOC), the MCU estimates the SOC using the battery current and voltage. The MCU selects the two batteries with the lowest SOC and controls the intermediate selection switch Blockx, switch SW2x-1, and switch SW2x to connect the two batteries with the lowest SOC to the BUCK-BOOST conversion circuit and the BUCK-BOOST conversion circuit, respectively, for synchronous energy replenishment, thus achieving energy balancing of the BBU module. It supports synchronous energy replenishment of two batteries via the bidirectional converter to achieve energy balancing of the BBU module. The switch selection module has a simple structure, is easy to control, and supports rapid connection of the battery being balanced during energy balancing.

[0035] Using only a charge / discharge current detection module and an equalization current detection module, a total of three current sensors, the current of each battery cell can be accurately estimated. During the State of Charge (SOC) estimation process, the battery current calculation takes into account the equalization current, making the SOC estimation more accurate. This solves the problem that the equalization current affects the estimation of battery state of charge, providing an accurate basis for judging the consistency of battery pack equalization. Attached Figure Description

[0036] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 An architecture diagram of an active balancing circuit for a BBU module considering balancing current is provided for an embodiment of the present invention.

[0039] Figure 2 Circuit diagram of the selection switch module and bidirectional converter provided for embodiments of the present invention;

[0040] Figure 3 A state diagram of the BUCK switching circuit provided in an embodiment of the present invention;

[0041] Figure 4 This is another state diagram of the BUCK switching circuit provided in an embodiment of the present invention;

[0042] Figure 5 A state diagram of a BUCK-BOOST conversion circuit provided in an embodiment of the present invention;

[0043] Figure 6 A state diagram of a BUCK-BOOST conversion circuit provided in an embodiment of the present invention;

[0044] Figure 7 A schematic diagram of a first-order Thevenin equivalent circuit model of a battery provided in an embodiment of the present invention;

[0045] Figure 8 The flowchart illustrates the extended Kalman algorithm for estimating SOC in an embodiment of the present invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0048] Example 1

[0049] See Figure 1 As shown, this embodiment of the invention provides an active balancing circuit for a BBU module that considers balancing current, comprising: an MCU, wherein the MCU is connected to a balancing current detection module connected to a bidirectional converter, the BBU module is connected to a charge / discharge current detection module, the charge / discharge current detection module is electrically connected to the MCU, the MCU is electrically connected to a battery in the BBU module to detect the voltage of the battery in the BBU module; an auxiliary battery is connected to the BBU module via a bidirectional converter and a selection switch module to provide balancing energy, the bidirectional converter and the selection switch module being electrically connected to the MCU.

[0050] In a preferred embodiment, the auxiliary battery comprises at least two batteries connected in series. The MCU is electrically connected to the auxiliary battery to detect its voltage.

[0051] See Figure 2 As shown, the bidirectional converter includes a BUCK conversion circuit and a BUCK-BOOST conversion circuit connected to the auxiliary battery. Specifically, the BUCK conversion circuit includes a field-effect transistor (FET) S1 whose source is connected to the positive terminal of the auxiliary battery; the drain of FET S1 is connected to an inductor L1; the inductor L1 is connected to the positive plate of capacitor C1; the negative plate of capacitor C1 is connected to the negative terminal of the auxiliary battery; the drain of FET S1 is connected to the source of FET S2; and the drain of FET S2 is connected to the negative terminal of the auxiliary battery. The BUCK-BOOST conversion circuit includes a field-effect transistor (FET) S3 whose source is connected to the positive terminal of the auxiliary battery; the drain of FET S3 is connected to an inductor L2; the inductor L2 is connected to the negative terminal of the auxiliary battery; the drain of FET S3 is connected to the source of FET S4; the drain of FET S4 is connected to the negative plate of capacitor C2; and the positive plate of capacitor C2 is connected to inductor L2.

[0052] The gates of field-effect transistors S1, S2, S3, and S4 are electrically connected to the MCU. The MCU controls the states of field-effect transistors S1, S2, S3, and S4 to switch the bidirectional converter mode. The bidirectional converter mode includes:

[0053] See Figure 3 As shown, the MCU controls the field-effect transistor S1 to be turned on and the field-effect transistor S2 to be turned off, so that the field-effect transistor S1, inductor L1 and capacitor C1 form a circuit, which assists the battery in charging inductor L1 and capacitor C1; see reference Figure 4 As shown, the MCU controls the field-effect transistor S1 to be turned off and the field-effect transistor S2 to be turned on, so that the field-effect transistor S2, the inductor L1 and the battery in the BBU module form a circuit, and the inductor L1 discharges to provide energy to the battery.

[0054] See Figure 5 As shown, the MCU controls the field-effect transistor S3 to be turned on and the field-effect transistor S4 to be turned off, so that the field-effect transistor S3 and the inductor L2 form a circuit, which assists the battery in charging the inductor L2; the capacitor C2 and the battery in the BBU module form a circuit, which provides energy to the battery in the BBU module to replenish the battery energy; the MCU controls the field-effect transistor S3 to be turned off and the field-effect transistor S4 to be turned on, so that the inductor L2 and the battery in the BBU module form a circuit, and the inductor L2 discharges to provide energy to the battery.

[0055] See Figure 2 As shown, the selection switch module includes: a plurality of intermediate selection switches Blockx for selecting the positive and negative terminals of the bidirectional converter; a switch SW2x-1 for controlling the connection between the battery in the BBU module and the intermediate selection switches Blockx; and a switch SW2x for controlling the connection between the battery in the BBU module and ground. Switches SW2x-1 and SW2x are connected to the corresponding positive terminals of the batteries in the BBU module, and the intermediate selection switches Blockx, SW2x-1, and SW2x are controlled to be connected to the MCU.

[0056] Taking simultaneous equalization charging of batteries B1 and B2 as an example, switches SW1 and SW3 are turned on. Switch SW1 is connected to the positive terminal through intermediate selection switch Block1, and switch SW3 is connected to the negative terminal through intermediate selection switch Block2. Switch SW2 is grounded. The BUCK switching circuit transfers energy to the connected battery B1, such as... Figure 3As shown, when the MCU controls MOSFET S1 to turn on and MOSFET S2 to turn off, energy from the auxiliary battery is transferred to inductor L1 and output to battery B1, while inductor L1 stores energy. Conversely, when the MCU controls MOSFET S1 to turn off and MOSFET S2 to turn on, energy from inductor L1 is output to battery B1, transferring energy to battery B1. The BUCK-BOOST conversion circuit transfers energy to the connected battery B2, as shown... Figure 4 As shown, when the MCU controls the MOSFET S3 to turn on and the MOSFET S4 to turn off, the auxiliary battery charges the inductor L2, the inductor L2 stores energy, and the energy of the capacitor C2 is transferred to the battery B2 to replenish the energy of the battery B2; when the MCU controls the MOSFET S3 to turn off and the MOSFET S4 to turn on, the inductor L2 discharges, and the energy of the inductor is transferred to the battery B2 to replenish the energy of the battery B2.

[0057] The MCU executes the following process cyclically: It uses the main circuit current detected by the charge / discharge current detection module and the equalization current detected by the equalization current detection module to obtain the current flowing through each battery in the BBU module. Based on the current and voltage of each battery, an extended Kalman algorithm is used to estimate the State of Charge (SOC) of each battery. The MCU selects the two batteries with the lowest SOC and controls the intermediate selection switch Blockx, switch SW2x-1, and switch SW2x so that the two batteries with the lowest SOC are connected to the BUCK conversion circuit and the BUCK-BOOST conversion circuit respectively, synchronously replenishing energy to achieve energy balance in the BBU module.

[0058] Specifically, when performing SOC estimation, a first-order Thevenin equivalent circuit model of the battery is constructed. The constructed first-order Thevenin equivalent circuit model of the battery is as follows: Figure 7 As shown, the circuit expressions for the state variables of the first-order Thevenin equivalent circuit model of the battery include: V = EV P -IR0,

[0059] The recursive formula for battery SOC is: SOC k+1 =SOC k -i k Δt / Q k i k Given the battery current over k time periods, the battery SOC recursive formula, combined with the circuit expression, yields the discretized formula as follows:

[0060] V k+1 =f k+1 (SOC k+1 )-V p,k+1 -R0i k+1 ,

[0061] V P,K+1 =V p,kexp(-Δt / R p C p )+R p i k (1-exp(-Δt / R p C p )),

[0062] The resulting state equation and observation equation are shown below:

[0063]

[0064]

[0065] By combining the state equation and observation equation with the extended Kalman algorithm, using the battery operating current in the state as the control variable and the battery voltage in the state as the observation variable, the extended Kalman algorithm is executed to estimate the battery SOC.

[0066] The specific process includes:

[0067] The state parameter values ​​are initialized based on the battery performance test data.

[0068] Initialize the initial values ​​of the state estimation error covariance P1+, process noise covariance Q, and observation noise covariance R when estimating the battery SOC at time k=1.

[0069] By detecting the initial terminal voltage of the battery, the initial SOC1 of the battery is calculated using the OCV-SOC curve, and the state vector at time k=1 is initialized as X1 = [SOC1, 0]. T .

[0070] With battery current i k As the control vector for the extended Kalman algorithm, the battery voltage V is used. k As the observation vector of the Extended Kalman Algorithm, the battery state is recursively calculated according to the principle of the Extended Kalman Algorithm to realize the state vector X at time k+1. k+1 The estimation is used to achieve the battery voltage and SOC at time k+1. k+1 Online estimation.

[0071] The state variables and error covariance are updated based on the actual voltage measurements.

[0072] The need for parameter updates is determined based on the error covariance. If no update is needed, online estimation of the lithium-ion battery terminal voltage and SOC is performed continuously. If an update is needed, the parameters of the first-order Thevenin equivalent circuit model are updated using the RLS method based on the voltage and current data of the battery at time k+1. Then, the state vector is updated before online estimation of the lithium-ion battery terminal voltage and SOC is performed.

[0073] When performing SOC estimation, the MCU estimates the current flowing through a single battery cell: This application utilizes an equalization current detection module to detect the equalization current during the energy transfer process, and employs a charge / discharge current detection module to detect the main circuit current flowing through the BBU module. The equalization current detection module includes two current sensors, which respectively detect the current flowing through inductor L1 and inductor L2. The current flowing through inductor L1 is approximately the equalization current during BUCK-BOOST circuit operation, and the current flowing through inductor L2 is approximately the equalization current during BUCK-BOOST circuit operation. The current flowing through each battery cell is calculated as follows:

[0074]

[0075] Among them, I c I is the main circuit current detected by the charge / discharge current detection module. b The equalization current detected by the equalization current detection module.

[0076] The MCU selects the two batteries with the lowest SOC and controls the intermediate selection switch Blockx, switch SW2x-1 and switch SW2x so that the two batteries with the lowest SOC are connected to the BUCK conversion circuit and the BUCK-BOOST conversion circuit respectively, so as to replenish energy synchronously and realize the energy balance of the BBU module.

[0077] When the MCU controls the bidirectional converter, it periodically executes the following processes: The MCU controls the field-effect transistor S1 to be turned on and the field-effect transistor S2 to be turned off, so that the field-effect transistor S1, inductor L1 and capacitor C1 form a circuit, assisting the battery in charging inductor L1 and capacitor C1; The MCU controls the field-effect transistor S1 to be turned off and the field-effect transistor S2 to be turned on, so that the field-effect transistor S2, inductor L1 and the battery in the BBU module form a circuit, and inductor L1 discharges to provide energy to the battery. The MCU controls the field-effect transistor S3 to be turned on and the field-effect transistor S4 to be turned off, so that the field-effect transistor S3 and inductor L2 form a circuit, assisting the battery in charging inductor L2; capacitor C2 and the battery in the BBU module form a circuit, providing energy to the battery in the BBU module to replenish the battery energy; The MCU controls the field-effect transistor S3 to be turned off and the field-effect transistor S4 to be turned on, so that the inductor L2 and the battery in the BBU module form a circuit, and inductor L2 discharges to provide energy to the battery.

[0078] Example 2

[0079] This invention provides an active balancing method for BBU modules considering balancing current, comprising:

[0080] First, a first-order Thevenin equivalent circuit model of the battery is constructed. The constructed first-order Thevenin equivalent circuit model of the battery is as follows: Figure 7As shown, the circuit expressions for the state variables of the first-order Thevenin equivalent circuit model of the battery include: V = EV P -IR0,

[0081] The recursive formula for battery SOC is: SOC k+1 =SOC k -i k Δt / Q k i k Given the battery current over k time periods, the battery SOC recursive formula, combined with the circuit expression, yields the discretized formula as follows:

[0082] V k+1 =f k+1 (SOC k+1 )-V p,k+1 -R0i k+1 ,

[0083] V P,K+1 =V p,k exp(-Δt / R p C p )+R p i k (1-exp(-Δt / R p C p )),

[0084] The resulting state equation and observation equation are shown below:

[0085]

[0086]

[0087] By combining the state equation and observation equation with the extended Kalman algorithm, using the battery operating current in the state as the control variable and the battery voltage in the state as the observation variable, the extended Kalman algorithm is executed to estimate the battery SOC.

[0088] The specific process includes:

[0089] The state parameter values ​​are initialized based on the battery performance test data.

[0090] Initialize the initial values ​​of the state estimation error covariance P1+, process noise covariance Q, and observation noise covariance R when estimating the battery SOC at time k=1.

[0091] By detecting the initial terminal voltage of the battery, the initial SOC1 of the battery is calculated using the OCV-SOC curve, and the state vector at time k=1 is initialized as X1 = [SOC1, 0]. T .

[0092] With battery current i k As the control vector for the extended Kalman algorithm, the battery voltage V is used. k As the observation vector of the Extended Kalman Algorithm, the battery state is recursively calculated according to the principle of the Extended Kalman Algorithm to realize the state vector X at time k+1. k+1 The estimation is used to achieve the battery voltage and SOC at time k+1. k+1 Online estimation.

[0093] The state variables and error covariance are updated based on the actual voltage measurements.

[0094] The need for parameter updates is determined based on the error covariance. If no update is needed, online estimation of the lithium-ion battery terminal voltage and SOC is performed continuously. If an update is needed, the parameters of the first-order Thevenin equivalent circuit model are updated using the RLS method based on the voltage and current data of the battery at time k+1. Then, the state vector is updated before online estimation of the lithium-ion battery terminal voltage and SOC is performed.

[0095] When performing SOC estimation, the MCU estimates the current flowing through a single battery cell: This application utilizes an equalization current detection module to detect the equalization current during the energy transfer process, and employs a charge / discharge current detection module to detect the main circuit current flowing through the BBU module. The equalization current detection module includes two current sensors, which respectively detect the current flowing through inductor L1 and inductor L2. The current flowing through inductor L1 is approximately the equalization current during BUCK-BOOST circuit operation, and the current flowing through inductor L2 is approximately the equalization current during BUCK-BOOST circuit operation. The current flowing through each battery cell is calculated as follows:

[0096]

[0097] Among them, I c I is the main circuit current detected by the charge / discharge current detection module. b The equalization current detected by the equalization current detection module.

[0098] The MCU selects the two batteries with the lowest SOC and controls the intermediate selection switch Blockx, switch SW2x-1 and switch SW2x so that the two batteries with the lowest SOC are connected to the BUCK conversion circuit and the BUCK-BOOST conversion circuit respectively, so as to replenish energy synchronously and realize the energy balance of the BBU module.

[0099] When the MCU controls the bidirectional converter, it periodically executes the following processes: The MCU controls the field-effect transistor S1 to be turned on and the field-effect transistor S2 to be turned off, so that the field-effect transistor S1, inductor L1 and capacitor C1 form a circuit, assisting the battery in charging inductor L1 and capacitor C1; The MCU controls the field-effect transistor S1 to be turned off and the field-effect transistor S2 to be turned on, so that the field-effect transistor S2, inductor L1 and the battery in the BBU module form a circuit, and inductor L1 discharges to provide energy to the battery. The MCU controls the field-effect transistor S3 to be turned on and the field-effect transistor S4 to be turned off, so that the field-effect transistor S3 and inductor L2 form a circuit, assisting the battery in charging inductor L2; capacitor C2 and the battery in the BBU module form a circuit, providing energy to the battery in the BBU module to replenish the battery energy; The MCU controls the field-effect transistor S3 to be turned off and the field-effect transistor S4 to be turned on, so that the inductor L2 and the battery in the BBU module form a circuit, and inductor L2 discharges to provide energy to the battery.

[0100] Example 3

[0101] This invention provides a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the active balancing method for a BBU module considering balancing current. The method includes: an MCU acquiring the voltage of the batteries in the BBU module; the MCU detecting the balancing current using a balancing current detection module; the MCU acquiring the charging and discharging current of the BBU module using a charging and discharging current detection module; obtaining the current of each battery cell in the BBU module using the balancing current and the charging and discharging current; and estimating the state of charge (SOC) of each battery cell using the classic extended Kalman algorithm based on the current and voltage of each battery cell. Specifically, estimating the SOC of each battery cell using the extended Kalman algorithm involves: constructing a first-order Thevenin equivalent circuit model of the battery to obtain the circuit expression of the state variables in the first-order Thevenin equivalent circuit model when the battery is operating; combining the battery SOC recursive formula and the circuit expression to obtain discrete relationships between the states and SOC in the first-order Thevenin equivalent circuit model; using the battery operating current in the state as a control variable and the battery voltage in the state as an observation variable; and executing the extended Kalman algorithm to estimate the battery SOC.

[0102] The MCU selects the two batteries with the lowest SOC and controls the intermediate selection switch Blockx, switch SW2x-1 and switch SW2x so that the two batteries with the lowest SOC are connected to the BUCK conversion circuit and the BUCK-BOOST conversion circuit respectively, so as to replenish energy synchronously and realize the energy balance of the BBU module.

[0103] Of course, the computer program stored in the computer-readable storage medium provided in the embodiments of the present invention is not limited to the method operation described above, but can also execute related operations in the active balancing method of BBU module considering balancing current provided in any embodiment of the present invention.

[0104] In the embodiments provided by this invention, it should be understood that the disclosed structures and methods can be implemented in other ways. For example, the structural embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, structures, or units, and may be electrical, mechanical, or other forms.

[0105] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0106] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0107] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An active balancing circuit for a BBU module considering balancing current, characterized in that, Includes: an MCU, which is connected to a balancing current detection module connected to a bidirectional converter; a BBU module connected to a charge / discharge current detection module, which is electrically connected to the MCU; and the MCU is electrically connected to the battery in the BBU module to detect the voltage of the battery in the BBU module. An auxiliary battery is connected to the BBU module via a bidirectional converter and a selection switch module to provide balancing energy, and the bidirectional converter and selection switch module are electrically connected to the MCU. The bidirectional converter includes: a BUCK conversion circuit and a BUCK-BOOST conversion circuit connected to the auxiliary battery; The BUCK switching circuit includes: a field-effect transistor S1 whose source is connected to the positive terminal of the auxiliary battery; the drain of the field-effect transistor S1 is connected to an inductor L1; the inductor L1 is connected to the positive plate of a capacitor C1; the negative plate of the capacitor C1 is connected to the negative terminal of the auxiliary battery; the drain of the field-effect transistor S1 is connected to the source of a field-effect transistor S2; the drain of the field-effect transistor S2 is connected to the negative terminal of the auxiliary battery; and the gates of the field-effect transistors S1 and S2 are electrically connected to the MCU. The BUCK-BOOST conversion circuit includes: a field-effect transistor S3 whose source is connected to the positive terminal of the auxiliary battery; the drain of the field-effect transistor S3 is connected to an inductor L2, and the inductor L2 is connected to the negative terminal of the auxiliary battery; the drain of the field-effect transistor S3 is connected to the source of the field-effect transistor S4; the drain of the field-effect transistor S4 is connected to the negative plate of the capacitor C2; the positive plate of the capacitor C2 is connected to the inductor L2; and the gates of the field-effect transistors S3 and S4 are electrically connected to the MCU. The selection switch module includes: a plurality of intermediate selection switches Blockx for selecting the positive and negative terminals of the bidirectional converter, a switch SW2x-1 for controlling the connection between the battery in the BBU module and the intermediate selection switch Blockx, and a switch SW2x for controlling the connection between the battery in the BBU module and ground. Switches SW2x-1 and SW2x are connected to the corresponding positive terminals of the batteries in the BBU module. The intermediate selection switches Blockx, SW2x-1, and SW2x are controlled to be connected to the MCU. The MCU collects the battery voltage in the BBU module, detects the balancing current using the balancing current detection module, and collects the charging and discharging current of the BBU module using the charging and discharging current detection module. It then uses the balancing current and the charging and discharging current of the BBU module to obtain the current of each battery cell in the BBU module. Based on the current and voltage of each battery cell, the extended Kalman algorithm is used to estimate the SOC of each battery cell. The MCU selects the battery with the lowest SOC corresponding to the BUCK-BOOST conversion circuit and the battery with the lowest SOC corresponding to the BUCK-BOOST conversion circuit. It controls the selection switch module to connect the two selected batteries with the lowest SOC to the bidirectional converter for synchronous energy replenishment, thus achieving energy balancing in the BBU module.

2. The active balancing circuit of the BBU module considering balancing current according to claim 1, characterized in that, The MCU controls the field-effect transistor S1 to be turned on and the field-effect transistor S2 to be turned off, so that the field-effect transistor S1, the inductor L1 and the capacitor C1 form a circuit, which assists the battery in charging the inductor L1 and the capacitor C1; the MCU controls the field-effect transistor S1 to be turned off and the field-effect transistor S2 to be turned on, so that the field-effect transistor S2, the inductor L1 and the battery in the BBU module form a circuit, and the inductor L1 discharges to provide energy to the battery.

3. The active balancing circuit of the BBU module considering balancing current according to claim 1, characterized in that, The MCU controls the MOSFET S3 to turn on and the MOSFET S4 to turn off, so that the MOSFET S3 and the inductor L2 form a circuit, which assists the battery in charging the inductor L2; the capacitor C2 and the battery in the BBU module form a circuit, which provides energy to the battery in the BBU module to replenish the battery energy; the MCU controls the MOSFET S3 to turn off and the MOSFET S4 to turn on, so that the inductor L2 and the battery in the BBU module form a circuit, and the inductor L2 discharges to provide energy to the battery.

4. The active balancing circuit of the BBU module considering balancing current according to claim 1, characterized in that, The method of using the extended Kalman algorithm to estimate the SOC of each battery cell includes: constructing a first-order Thevenin equivalent circuit model of the battery to obtain the circuit expression of the state variables in the first-order Thevenin equivalent circuit model when the battery is working; combining the battery SOC recursive formula and the circuit expression to obtain the relationship between the state and SOC in the discrete first-order Thevenin equivalent circuit model of the battery; using the battery operating current in the state as the control variable and the battery voltage in the state as the observation variable; and executing the extended Kalman algorithm to estimate the battery SOC.

5. The BBU module active balancing circuit considering balancing current according to claim 4, characterized in that, The circuit expressions for the state variables of the first-order Thevenin equivalent circuit model of a battery include: , , The recursive formula for battery SOC is: ; Given the battery current over k time periods, the battery SOC recursive formula, combined with the circuit expression, yields the discretized formula as follows: ， ， The resulting state equation and observation equation are shown below: ， ； By combining the state equation and observation equation with the extended Kalman algorithm, using the battery operating current in the state as the control variable and the battery voltage in the state as the observation variable, the extended Kalman algorithm is executed to estimate the battery SOC.

6. The active balancing circuit for a BBU module considering balancing current according to claim 5, characterized in that, The extended Kalman algorithm for battery SOC estimation includes: The state parameter values ​​are initialized based on the battery performance test data; Initialize the initial values ​​of the state estimation error covariance P1+, process noise covariance Q, and observation noise covariance R when estimating the battery SOC at time k=1; By detecting the initial terminal voltage of the battery, the initial SOC1 of the battery is calculated using the OCV-SOC curve, and the state vector at time k=1 is initialized as X1=[SOC1, 0]. T ; With battery current i k As the control vector for the extended Kalman algorithm, the battery voltage V is used. k As the observation vector of the Extended Kalman Algorithm, the battery state is recursively calculated according to the principle of the Extended Kalman Algorithm to realize the state vector X at time k+1. k+1 The estimation is used to achieve the battery voltage and SOC at time k+1. k+1 Online estimation; The state variables and error covariance are updated based on the actual voltage measurements. The parameter update is determined based on the error covariance; if no update is needed, the online estimation of lithium-ion battery terminal voltage and SOC is continuously performed. If an update is needed, the RLS method is used to update the parameters of the first-order Thevenin equivalent circuit model based on the voltage and current data of the battery at time k+1. Then, after updating the state vector, the online estimation of the lithium-ion battery terminal voltage and SOC is performed.

7. The active balancing circuit for a BBU module considering balancing current according to claim 1, characterized in that, The current flowing through each battery cell is calculated as follows: ； in, The main circuit current detected by the charge / discharge current detection module. The equalization current detected by the equalization current detection module.

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