TWI756980B - Autonomous active battery balancer and method therefor - Google Patents

Abstract

The present invention relates to an autonomous active battery balancer and a method thereof, comprising: a battery stack, a set of first relays, a set of second relays and a battery management system, which are connected to normally open connections of the first relays. The point (a contact) is connected with an inductive element; by connecting each first relay normally closed circuit (com contact, b contact), each DC battery and each second relay normally closed circuit (com contact, b contact) in series point) to form a battery discharge mode; by paralleling each DC battery, the normally open circuit (com contact, a contact) and each inductance of each first relay, a battery charging mode is formed, and the The battery management system performs automatic switching control of two modes, so that the present invention has the advantages of fast response rate of battery capacity balance, true capacity balance and the like.

Description

Autonomous active battery balancer and method therefor

The present invention relates to the field of batteries, in particular to the field of an autonomous active battery balancer.

Press, the current lithium-ion battery is currently a green rechargeable battery, lithium-ion battery has a higher rated voltage (3.4 ~ 4.2 volts) and energy density, high voltage and high capacity can be easily achieved by connecting lithium-ion batteries in series; At the same time, the battery cycle life is about 4~5 times that of ordinary rechargeable batteries, and 8~10 times higher than the high discharge power of ordinary rechargeable batteries (which can generate large currents instantaneously).

In addition, the battery capacity of the lithium ion battery is unbalanced or other cell imbalance problems cause the battery working time to decrease. In order to avoid the above defects, a protection circuit must be added inside the lithium ion battery. Therefore, engineers usually have to use a Cell Balance (CB) circuit to solve the cell imbalance problem.

Looking back at the existing cell balancing (CB) or cell equalizer (CE) technology, it is mainly divided into passive and active. As shown in Figure 5, the passive cell balancing technology mainly uses resistance as the discharge element, although it has The advantages of simple architecture and low cost, but the waste heat and low energy efficiency caused by cell balancing are the main disadvantages.

Further, the active battery balancing technology mainly uses energy storage elements such as capacitors and inductors as the intermediate medium for discharging/charging, which has the advantage of high energy efficiency. The most important disadvantage is that the battery with high battery capacity (State of Charge, SOC) → the balance voltage of capacitor/inductor discharge is still Higher than the balance voltage of capacitor/inductor → battery charging, that is, the battery balance purpose of true SOC is not achieved.

Further, the DC/DC converter battery balancing technology uses the pulse width modulation (PWM) technology of the DC/DC converter to control the output voltage/current of the corresponding battery to achieve the purpose of battery balancing, and has a fast response rate. , but the control system is complex and the cost is high.

However, the transformer-type battery balancing technology uses the transformer active element as the charging/discharging element, which not only has high cost, but also has the potential difference of high SOC battery→transformer balancing voltage, voltmeter→low SOC battery balancing voltage. Evaluation and analysis There is currently no relevant technology for a battery balancer design that is cost-effective and has consistent cell voltages after balancing.

Taking the existing battery balancer using inductors as an example, traditional inductive balancers can be divided into traditional single shunt inductive battery balancers 5, as shown in the system architecture diagram in Figure 6, and traditional individual shunt inductive battery balancers. (Individual shunt inductive) battery balancer 6, as shown in the system architecture diagram shown in FIG. 7 .

The traditional inductive battery balancer needs to have two control switches, which are used for high-capacity battery discharge and low-capacity battery charging. It can reach the same voltage level as the high-capacity battery (generally lower than the high-capacity battery voltage level), and then the inductor is charged with the low-capacity battery, as shown in Figure 9, so the voltage level of the traditional inductive battery balancer after balancing is still lower than the original inductor voltage level.

FIG. 10 shows the balancing time required by the conventional inductive battery balancer and the voltage levels of the balanced high-capacity batteries, balanced inductors, and low-capacity batteries. Observing from Figures 8 and 9, it can be found that the voltage levels of the high-capacity and low-capacity batteries still differ slightly after the existing battery balancers of various capacitors, inductors and transformers are balanced, which cannot truly achieve the purpose of battery balancing.

Therefore, the inventor of the present invention has developed an autonomous active cell balancer of the present invention with great efforts. Therefore, the main purpose of the present invention is to provide an autonomous active cell balancer with fast balancing reaction rate and true capacitance balance.

In order to achieve the above object, the present invention uses the following technical means: an autonomous active battery balancer, which includes: a battery stack, which is composed of the first to Nth DC batteries; a group of first relays, which are Set as the 1st to Nth ones, and are respectively installed in front of the corresponding DC batteries, and the first relay further includes a first control part; in addition, the normally open contact (a contact) of each first relay An inductive element is connected; a group of second relays are set as the first to (N-1)th, and are respectively installed after the corresponding DC battery and before the corresponding first relay, and the second relay It further includes a second control part; and a battery management system, including a battery balancing module, and the battery balancing module is electrically connected to the first control part of each first relay, and is electrically connected to the first control part of each second relay The second control part; by connecting the normally closed circuits of the first relays (com contacts, b contacts), the DC batteries and the normally closed circuits of the second relays (com contacts, b contacts) in series to form a Battery discharge mode; by paralleling each DC battery, the normally open circuit (com contact, a contact) of each first relay and each inductance, a battery charging mode is formed, and the battery balance mode of the battery management system is used. The group performs automatic switching control of two modes.

The common contact (com contact) of each first relay is electrically connected to the positive electrode of each DC battery, and the common contact (com contact) of each second relay is electrically connected to the negative electrode of each DC battery.

The control voltage signal of the battery balance module of the battery management system is set to 5, 12, 24 or 48V _DC , and the first relay and the second relay are both set as high current relays.

The DC battery is set as a lithium-ion battery.

Regarding the independent active battery balancing method of the present invention, it includes: a hardware construction step, which is to construct the 1st to Nth DC batteries, and to construct the 1st to Nth first relays and respectively It is installed before the corresponding DC battery; in addition, an inductance element is connected to the normally open contact (contact a) of each first relay; the first to (N-1) second relays are also built and respectively It is installed after the corresponding DC battery and before the corresponding first relay; a battery discharge mode establishment step is to connect the normally closed circuits (com contacts and b contacts) of the first relays, the DC batteries and the second relays in series. A relay normally closed circuit (com contact, b contact), according to which a battery discharge mode is formed; a battery charging mode establishment step is connected in parallel with the normally open circuits of each DC battery and each first relay (com contact, a contacts) and each inductance to form a battery charging mode; and a battery management system building step is to build a battery management system with a battery balancing module, and the battery balancing module is electrically connected to each A first control part provided in a relay, and a second control part provided in each second relay electrically connected to provide automatic switching control of the battery discharging mode and the battery charging mode.

The "autonomous active battery balancer" of the present invention can achieve the following effects: the present invention mainly uses the voltage-current characteristics of the inductor to achieve high impedance inrush current protection, zero impedance/short-circuit battery capacity balance, synchronization required for battery balancing The independent active battery balancing function such as high-capacity (SOC) battery discharge/low-capacity battery discharge, etc., has the advantages of fast response rate and true capacity balance compared with battery balancers of various capacitors, inductors and transformers.

A: Active battery balancer

B: Active cell balancing method

a: Hardware construction steps

b: Steps for establishing battery discharge mode

c: Steps for establishing battery charging mode

d: Steps to build the battery management system

1: battery stack

2: The first relay

21: The first control department

22: Inductance

3: The second relay

31: Second Control Department

4: Battery management system

41: Cell Balancing Module

5: Traditional single shunt inductor type battery balancer

6: Traditional individual shunt inductor type battery balancer

[Fig. 1] The structure diagram of the autonomous active battery balancer of the present invention.

[FIG. 2] The structure diagram of the battery balancing mode of the autonomous active battery balancer of the present invention.

[FIG. 3] The time domain response diagram of the autonomous active battery balancer of the present invention.

[FIG. 4] The flow chart of the autonomous active cell balancing method of the present invention.

[Figure 5] Tree diagram of cell balancing technology.

[Figure 6] A block diagram of a conventional single-shunt inductor type cell balancer.

[Fig. 7] A block diagram of a conventional individual shunt inductor type cell balancer.

[Fig. 8] and [Fig. 9] The traditional single-shunt inductor type battery balancer works.

[Fig. 10] Time domain response graph of voltage level of conventional inductance balancer.

First, please refer to FIG. 1 , the present invention relates to an autonomous active battery balancer A, which is mainly provided as a balancer for lithium-ion batteries, which includes: a battery stack 1 , a set of first relays 2 , a set of Components such as the second relay 3 and a battery management system 4; the above components are described in the following with the drawings respectively.

The battery stack 1 is composed of the first to Nth DC batteries, wherein the number of the N DC battery terminals is determined according to requirements and design; the first relay 2 of the group is set as the first The first relay 2 further includes a first control part 21 ; and the normally open contact (a contact) of each first relay 2 is connected to There is an inductor 22 element; the group of second relays 3 are set as the first to (N-1)th, and are respectively installed after the corresponding DC battery and before the corresponding first relay 2, and then The second relay 3 further includes a second control unit 31 ; the battery management system 4 includes a battery balancing module 41 , and the battery balancing module 41 is electrically connected to the first control unit of each first relay 2 part 21 , and a second control part 31 electrically connected to each of the second relays 3 .

A battery discharge mode is formed by connecting the normally closed circuits (com contacts and b contacts) of the first relays 2, the DC batteries and the second relays 3 normally closed circuits (com contacts and b contacts) in series. ; by The DC batteries, the normally open circuits (com contacts, a contacts) of the first relays 2 and the inductors 22 are connected in parallel to form a battery charging mode, which is performed by the battery balancing module 41 of the battery management system 4 Two-mode automatic switching control.

Therefore, the "autonomous active battery balancer A" of the present invention provides a better solution as a balancer for lithium-ion batteries or other battery balancers: it mainly uses the inductor itself, which has high impedance at high current rate of change and short-circuit at DC. Features, as the best passive component for battery balancing, and the control switch of the battery balancer adopts a high-current relay (High-current relay), with the working voltage of the battery stack (Pack), the control voltage signal can use 5/12/24/ 48V _DC (Vlots, Direct-Current). The system architecture diagram of the autonomous active battery balancer A is shown in Figure 1. The battery system is generally divided into a discharge mode and a charge mode, and the working description of its autonomous active battery balancer A is as follows.

Battery discharge mode: As shown in Figure 1, the high-current relay control switch of the battery balancer A of the present invention is rated close (Nominal close, NC), and the battery forms a series mode through the normally closed "b contact" of the high-current relay. In order to provide a general battery discharge mode, to provide power supply load.

Battery charging mode: When the battery is about to enter the charging mode, the battery management system (BMS) will stop the external power supply of the battery, and the “autonomous active battery balancer A” of the present invention uses the battery management system (BMS) to generate a battery balance control signal , drive the high-current relay to switch to open-circuit mode; that is, each battery is connected to an inductor through the normally open "a contact" of the high-current relay to form a parallel mode. Battery Capacity (SOC) The cells are automatically charged, and each cell can autonomously form a cell balance at a single voltage level. After the battery is balanced, the battery management system (BMS) cuts off the cell balance control signal, the high-current relay automatically switches to closed-circuit mode, and the battery automatically enters the discharge mode.

The "autonomous active battery balancer A" of the present invention is completely different from the existing battery balancers and the existing battery balancers of various capacitors, inductors and transformers. As shown in FIG. 2, before the battery is charged, the battery is directly Enter the battery balancing mode, and perform the autonomous battery balancing function of discharging high-capacity batteries and charging low-capacity batteries simultaneously in parallel.

To sum up, the power balance of each battery in the rechargeable battery stack is carried out before the battery stack is charged. When the high-power (SOC) battery is discharged or the low-power battery is charged, the internal resistance of the battery itself is very small (generally less than 3mΩ). ), even if the potential difference between the high-power battery and the low-power battery is only tens/hundreds of mV, an inrush current of tens/hundreds of amperes (A) may be generated, causing the battery to be overloaded and over-discharged and charged. damage.

Therefore, the "autonomous active battery balancer A" of the present invention uses the voltage-current characteristics of the inductance (inductance value L ):

Among them, v _L ( t ), i _L ( t ) are the terminal voltage and current of the inductor. When the battery stack is to be balanced, the high-battery battery and the low-battery battery both form a parallel circuit through a series inductance. At this time, the high-battery battery The inrush current caused by the potential difference with the low-battery battery will create a voltage drop at the inductor terminal due to the voltage-current characteristics of the inductor, thereby reducing the potential difference and inrush current between the high-battery and low-battery batteries. At this time, the inductance can be regarded as the inrush current of the battery discharge/discharge Current limiter, which has the function of protecting battery discharge/discharge. When the potential difference between the high-battery battery and the low-battery battery is close to 0, the current flowing through the inductor is close to 0, and the voltage drop at the inductance terminal is close to 0, which can be regarded as a short circuit. voltage level to achieve the purpose of true battery balance.

In other words, the time domain response of the cell balancing of the "autonomous active cell balancer A" of the present invention is shown in FIG. 3 . Therefore, it can be clearly seen from Figure 3 and Figure 10: (1), the present invention "autonomous active Battery Balancer A” has the functions of simultaneously discharging high-power (SOC) batteries and charging low-power batteries. The battery balancing time is significantly shorter than that of traditional battery balancers with various capacitors, inductors, and transformers, and the response rate in the time domain is fast. (2) The inductor structure designed by the "autonomous active battery balancer A" of the present invention has the function of inrush current protection of the battery at the beginning of battery balancing. (3) The inductor structure designed by the "autonomous active battery balancer A" of the present invention has the function of achieving true voltage uniformity and capacitance balance for all batteries during battery balancing.

Summarizing the above-mentioned active battery balancer A of the present invention, as shown in FIG. 4 (in conjunction with FIG. 1 ), the active battery balancing method B of the present invention can be obtained, which includes: a hardware construction step a, the 1st to Nth DC batteries are built, and the 1st to Nth first relays 2 are built and respectively installed before the corresponding DC batteries; in addition, each first relay 2 is normally open An inductance 22 element is connected to the contact (contact a); the first to (N-1) second relays 3 are also built and installed after the corresponding DC battery and before the corresponding first relay 2 respectively. ; A battery discharge mode establishment step b is to connect in series each of the first relays 2 normally closed circuits (com contacts, b contacts), each of the DC batteries and each of the second relays 3 normally closed circuits (com contacts, b contacts) ), according to form a battery discharge mode; a battery charging mode establishment step c, connected in parallel with each DC battery, the normally open circuit (com contact, a contact) of each first relay 2 and each inductance 22, according to A battery charging mode is formed; and a battery management system building step d is to build a battery management system 4 of a battery balancing module 41 , and the battery balancing module 41 is electrically connected to each of the first relays 2 . A first control unit 21 and a second control unit 31 electrically connected to each of the second relays 3 to provide automatic switching control between the battery discharging mode and the battery charging mode.

To sum up, the present invention relates to an "autonomous active battery balancer and method thereof", and its constituent devices and methods have not been found in books or published in public use, and it is in line with the requirements for patent application. Granted the patent, most grateful; What needs to be stated, the above are the specific embodiments of the patent application and the technical principles used. If the changes are made according to the concept of the patent application, the functions produced by them will not exceed the description and drawings. The spirit covered shall be stated within the scope of this patent application.

A: Active battery balancer

1: battery stack

2: The first relay

21: The first control department

22: Inductive components

3: The second relay

31: Second Control Department

4: Battery management system

41: Cell Balancing Module

Claims (7)

An autonomous active battery balancer includes: a battery stack, which is composed of the first to the Nth DC batteries; a group of first relays, which are set as the first to the Nth, and are respectively Before the corresponding DC battery, the first relay further includes a first control part; in addition, an inductive element is connected to the normally open contact (a contact) of each first relay; a group of second relays, are set as the first to (N-1)th, and are respectively installed after the corresponding DC battery and before the corresponding first relay, and the second relay further includes a second control part; and a battery management The system includes a battery balancing module, and the battery balancing module is electrically connected to the first control part of each first relay, and is electrically connected to the second control part of each second relay; by connecting the first relays in series Normally closed circuit (com contact, b contact), each DC battery and each second relay normally closed circuit (com contact, b contact), according to form a battery discharge mode; The normally open circuit (com contact, a contact) and each inductance of the first relay form a battery charging mode, and the battery balancing module of the battery management system performs automatic switching control between the two modes. The autonomous active battery balancer according to claim 1, wherein a common contact (com contact) of each first relay is electrically connected to the positive electrode of each DC battery. The autonomous active battery balancer according to claim 1, wherein a common contact (com contact) of each second relay is electrically connected to the negative electrode of each DC battery. The autonomous active battery balancer as claimed in claim 1, wherein the control voltage signal of the battery balancing module of the battery management system is set to 5, 12, 24 or 48V _DC . The autonomous active battery balancer according to claim 1, wherein the first relay and the second relay are both set as high-current relays. The autonomous active battery balancer according to any one of claims 1 to 5, wherein the DC battery is a lithium-ion battery. An autonomous active battery balancing method, which includes: a hardware construction step, which is to construct the first to Nth DC batteries, and construct the first to Nth first relays, which are respectively arranged in the In front of the corresponding DC battery; an inductance element is connected to the normally open contact (contact a) of each first relay; the first to (N-1) second relays are also built and respectively installed in After the corresponding DC battery and before the corresponding first relay; a battery discharge mode establishment step is to connect the normally closed circuits (com contacts and b contacts) of the first relays, the DC batteries and the second relays in series; A closed circuit (com contact, b contact) is formed to form a battery discharge mode; a battery charging mode establishment step is connected in parallel with the normally open circuits (com contact, a contact) of each DC battery and each first relay ) and each inductance to form a battery charging mode; and a battery management system building step is to build a battery management system with a battery balancing module, and the battery balancing module is electrically connected to the first relays A first control unit is provided, and a second control unit is electrically connected to each second relay, so as to provide automatic switching control of the battery discharging mode and the battery charging mode.

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