TWI697182B - Bidirectional soc balancing system with surge current suppressing ability - Google Patents

Abstract

A bidirectional SOC balancing system with surge current suppressing ability, comprises: a battery balancing switch set; a bidirectional flyback converter, wherein the battery balancing switch set is connected between a primary side of the bidirectional flyback converter and each battery, and a secondary side of the bidirectional flyback converter is connected to two ends of a battery pack; a battery monitoring module; and a controlling module which controls the bidirectional flyback converter and the battery balancing switch set according to the voltage and the current measured by the battery monitoring module, wherein the controlling module controls the bidirectional flyback converter to enable the battery pack to precharge the primary side to a precharge voltage just before a specific switch is turned on so as to suppressing a surge current.

Description

Bidirectional battery balancing system with inrush current suppression function

The present invention relates to a battery balancing system, in particular to a two-way battery balancing system.

Due to manufacturing errors and differences in usage conditions, etc., each battery in the battery pack may have different impedance or capacity. Without cell balancing, the common charge or discharge of these batteries will cause some batteries to be overcharged or overdischarged, resulting in a further reduction in battery life and performance.

The cell balancing system is divided into passive balancing and active balancing. Passive cell balancing systems are simply batteries that consume a high amount of power. An active cell balancing system charges a battery with a higher power to a battery with a lower power, and has better power usage efficiency. However, during the operation of the active cell balancing system, the switches in the system will switch multiple times. Each moment the switch is turned on, a surge current that is much higher than the steady state is briefly generated, resulting in a reduction in the life of the switch and other components.

Therefore, the object of the present invention is to provide a two-way cell balancing system with a surge current suppression function to reduce the damage caused by the surge current and extend the service life.

The technical means adopted by the present invention to solve the problems of the conventional technology is to provide a two-way cell balancing system for suppressing inrush current when cell balancing is performed on a battery pack having a plurality of batteries connected in series. The cell balancing system includes: a battery balancing switch group with a plurality of primary side switches, each of which corresponds to one of the primary side switches; a bidirectional flyback converter, each primary side switch of the battery balancing switch group is connected Between the primary side of the bidirectional flyback converter and each battery, and the secondary side of the bidirectional flyback converter is connected to the two ends of the battery pack; a battery monitoring module is connected to each of the The battery measures the voltage and current of each battery; a control module connected to the bidirectional flyback converter, a plurality of primary switches and the battery monitoring module, the control module is based on the battery monitoring module The measured voltage and current determine the battery to be balanced among the plurality of batteries, and control the bidirectional flyback converter and the primary switch corresponding to the battery to be balanced, and the battery to be balanced The corresponding primary switch is set to a designated primary switch, and the voltage of the battery to be balanced is the voltage of the battery to be balanced, wherein the control module controls the bidirectional flyback before turning on the designated primary switch The converter causes the battery pack to boost the primary side of the bidirectional flyback converter to a precharge voltage through the bidirectional flyback converter, and the difference between the precharge voltage and the battery voltage to be balanced is When 0, the control module controls the specified primary switch to be turned on.

In an embodiment of the present invention, a bidirectional battery balancing system is provided, and the primary side switch is a photorelay.

In an embodiment of the present invention, a two-way cell balancing system is provided, and the primary side switch is a power switch, a solid state relay, or an electromagnetic relay.

In an embodiment of the present invention, a two-way battery balancing system is provided, which further includes a battery state estimation module and a battery state estimation switch, the control module is connected to the battery state estimation module, and the control module The group measures the impedance of each battery through the state-of-charge estimation module. The state-of-charge estimation switch is connected between the state-of-charge estimation module and the battery pack. The control module is based on According to the voltage and current measured by the battery monitoring module and the impedance measured by the state-of-charge estimation module, a battery to be balanced among a plurality of batteries is determined, and the bidirectional flyback is controlled A converter and a plurality of the primary side switches, and the control module is connected to the power state estimation switch to control the power state estimation switch.

In an embodiment of the present invention, a two-way cell balancing system is provided, and the number of the batteries to be balanced determined by the control module is a plurality of lower than the number of all the batteries.

In an embodiment of the invention, a two-way cell balancing system is provided. The control module estimates the state of the cell by using the relationship between the battery voltage change and the battery current change during the pumping period.

In an embodiment of the present invention, a two-way power balance system is provided. The control module estimates the power state by using a Kalman filter, neural network, genetic algorithm, or multi-level RC equivalent. The estimation method of module etc. realizes electricity estimation.

Through the technical means adopted by the two-way cell balancing system of the present invention, the control module will control the two-way flyback converter before the designated primary side switch is turned on to make the battery pack fly back to the two-way through the two-way flyback converter The primary side of the converter is boosted to the precharge voltage. When the precharge voltage is within a predetermined range, the control module controls the designated primary side switch to conduct. Therefore, the voltage difference between the two sides of the primary switch is 0, and the inrush current generated when the primary switch is turned on is weak. In this way, the inrush current generated when the switch is turned on is suppressed, and the problems of component damage and battery life reduction caused by the inrush current are reduced, thereby further improving system stability.

100: Two-way battery balancing system

1: battery balancing switch group

11: Primary side switch

11': Designated primary side switch

2: Bidirectional flyback converter

3: battery monitoring module

4: control module

5: Power state estimation module

6: Power state estimation switch

B: battery

B': battery to be balanced

P: battery pack

Vb: battery voltage to be balanced

Vc: pre-charge voltage

[Figure 1] is a block diagram showing a two-way cell balancing system according to an embodiment of the present invention; [Figure 2] is a partial circuit schematic diagram showing a bidirectional cell balancing system according to an embodiment of the invention; [Figure 3] is a partial circuit schematic diagram showing a bidirectional cell balancing system according to an embodiment of the invention; [Figure 4] is a partial circuit diagram showing a bidirectional cell balancing system according to an embodiment of the present invention; [Figure 5] is a flowchart showing a bidirectional cell balancing system according to an embodiment of the present invention;

Hereinafter, the embodiments of the present invention will be described based on FIGS. 1 to 5. This description is not intended to limit the embodiments of the present invention, but is one of the examples of the present invention.

As shown in FIGS. 1 to 4, a bidirectional cell balancing system 100 according to an embodiment of the present invention is used to suppress inrush current when cell balancing is performed on a battery pack P. The battery pack P has a plurality of serial numbers A battery B, a two-way cell balancing system 100 includes: a battery balancing switch group 1, with a plurality of primary side switches 11, each battery B corresponds to a primary side switch 11; a bidirectional flyback converter 2, a battery balancing switch Each primary side switch 11 of the group 1 is connected between the primary side of the bidirectional flyback converter 2 and each battery B, and the secondary side of the bidirectional flyback converter 2 is connected to both ends of the battery pack P; The battery monitoring module 3 is connected to each battery B to measure the voltage and current of each battery B; a control module 4 is connected to the bidirectional flyback converter 2, a plurality of primary side switches 11 and the battery monitoring module 3 The control module 4 determines the battery B'to be balanced among the plurality of batteries B according to the voltage and current measured by the battery monitoring module 3, and controls the bidirectional flyback converter 2 and the battery to be balanced B' The corresponding primary side switch 11, and the primary side switch 11 corresponding to the battery B'to be balanced is set to a designated primary side switch 11', the voltage of the battery to be balanced B'is the battery voltage Vb to be balanced, wherein, the control Before the module turns on the designated primary side switch 11', it controls the bidirectional flyback converter to make the battery pack fly back to the bidirectional through the bidirectional flyback converter The primary side of the converter is boosted to a precharge voltage. When the difference between the precharge voltage Vc and the battery voltage Vb to be balanced is 0, the control module controls the designated primary side switch 11' to be turned on.

The primary side switch 11 is a photorelay. Compared with the conventional power switch, this embodiment has lower system control complexity and manufacturing cost. In other embodiments, the primary switch 11 may also be a power switch, a solid-state relay, or an electromagnetic relay.

The functions of the primary side and the secondary side of the bidirectional flyback converter 2 are the same, can operate bidirectionally, and have better flexibility in use. In detail, the battery balance of the present invention may be that the battery B'on the first side can charge the battery pack P on the secondary side, or all the batteries B on the secondary side can charge the battery on the first side B'to charge. Furthermore, through the use of a battery-balanced switch group, the bidirectional flyback converter 2 of the present invention can achieve the battery cell P balance using only a set of dual-winding transformers, and reduce the number of transformer windings and the use of transformer coils. Significantly reduce system complexity.

As shown in FIG. 1, the state-of-charge estimation switch 6 is connected between the state-of-charge estimation module 5 and the battery pack P. The control module 4 is connected to the power state estimation switch 6. When performing the state-of-charge estimation, the control module 4 controls the state-of-charge estimation switch 6 to be turned on so that the state-of-charge estimation module 5 is connected to the battery pack P to calculate the impedance of each battery B.

In detail, the power state estimation module 5 is a resonant load. The control module 4 is connected to the state-of-charge estimation module 5 and controls the state-of-charge estimation module 5 to perform sine wave pumping with a preset amplitude on each battery B. In this embodiment, the pumping type is to draw a sine wave current from the battery B. The control module 4 calculates the impedance of the battery B according to the voltage and current changes measured by the battery monitoring module 3 during the pumping period, and then estimates the state of charge (SOC) of each battery B . The control module 4 can also use Kalman filter, neural network, genetic algorithm or multi-level resistor-capacitor (RC) equivalent modeling and other estimation methods, according to the impedance of each battery B, The SOC of each battery B is estimated based on the voltage and current. Compared to estimating the battery B’s For the estimation method of SOC, this embodiment takes into account the life and performance of each battery B to make the estimation of SOC more accurate.

The control module 4 determines the battery B'to be balanced among the plurality of batteries B according to the SOC of each battery B, and controls the designated primary side switch 11 corresponding to the bidirectional flyback converter 2 and the battery to be balanced B' '.

As shown in FIG. 4, the number of batteries B′ to be balanced determined by the control module 4 is one. In other embodiments, the number of batteries B′ to be balanced determined by the control module 4 may also be a plurality of batteries that are lower than the number of all batteries B, and multiple batteries with the highest SOC or the lowest SOC are performed at a time. Battery balance. For example, the battery pack P has four batteries in total, and the control module 4 determines one to three batteries with the highest SOC or the lowest SOC as the battery B′ to be balanced according to the SOC.

After the SOC estimation is completed, the control module 4 controls the power state estimation switch 6 to be off, and then precharges the primary side of the bidirectional flyback converter 2 to reduce the two ends of the designated primary side switch 11' The voltage difference is to reduce the difference between the precharge voltage Vc and the battery voltage Vb to be balanced.

When the difference between the pre-charge voltage Vc and the battery voltage Vb to be balanced is 0, which means that when the pre-charge voltage Vc is equal to the battery voltage Vb to be balanced, the control module 4 controls the designated primary side switch 11' to be turned on, and the surge is suppressed. Wave current effect.

As shown in FIG. 5, the battery monitoring module 3 continuously measures the voltage and current of each battery B, and stops the bidirectional cell balancing system 100 of the present invention when the voltage or current of the battery B exceeds safe operating conditions. And has the function of under voltage, over voltage and over current protection. When the voltage or current of each battery B meets the safe operating conditions, the subsequent processes of SOC estimation, pre-charging, and battery balancing are performed.

The above descriptions and descriptions are only for the description of the preferred embodiments of the present invention. Those who have general knowledge of this technology can make other modifications based on the scope of the patent application as defined below and the above description, but these modifications should still be It is within the scope of the rights of the invention for the spirit of the invention.

100: Two-way battery balancing system

1: battery balancing switch group

2: Bidirectional flyback converter

3: battery monitoring module

4: control module

5: Power state estimation module

6: Power state estimation switch

P: battery pack

Claims (7)

A bidirectional cell balancing system with inrush current suppression function is used to suppress inrush current when performing cell balancing on a battery pack. The battery pack has a plurality of batteries connected in series. The bidirectional cell balancing system includes: a cell balancing switch Group, with a plurality of primary side switches, each of the batteries corresponds to one primary side switch; a bidirectional flyback converter, each primary side switch of the battery balancing switch group is connected to the bidirectional flyback converter Between the primary side and each of the batteries, and the secondary side of the bidirectional flyback converter is connected to the two ends of the battery pack; a battery monitoring module is connected to each of the batteries to measure the voltage of each of the batteries And current; a control module connected to the bidirectional flyback converter, the plurality of primary switches and the battery monitoring module, the control module is based on the voltage and current measured by the battery monitoring module And determine the battery to be balanced among the plurality of batteries, and control the bidirectional flyback converter and the primary switch corresponding to the battery to be balanced, and set the primary switch corresponding to the battery to be balanced to A designated primary switch, the voltage of the battery to be balanced is the voltage of the battery to be balanced, wherein, before the designated primary switch is turned on, the control module controls the bidirectional flyback converter so that the battery pack passes through the The bidirectional flyback converter boosts the primary side of the bidirectional flyback converter to a precharge voltage. When the difference between the precharge voltage and the battery voltage to be balanced is 0, the control module controls the The designated primary switch is turned on. As in the two-way cell balancing system of claim 1, the primary switch is a photorelay. As in the two-way cell balancing system of claim 1, the primary side switch is a power switch, solid state relay or electromagnetic relay. For example, the two-way battery balancing system of claim 1, further includes a battery state estimation module and a battery state estimation switch, the control module is connected to the battery state estimation module, and the control module is transparent The impedance of each battery is measured through the state-of-charge estimation module. The state-of-charge estimation switch is connected between the state-of-charge estimation module and the battery pack. The control module is based on the battery monitoring module. The measured voltage and current and the impedance measured by the state-of-charge estimation module determine the battery to be balanced among the plurality of batteries, and control the bidirectional flyback converter and the plurality of primary Side switch, and the control module is connected to the power state estimation switch to control the power state estimation switch. As in the two-way cell balancing system of claim 1, wherein the number of the batteries to be balanced determined by the control module is a plurality of cells that are lower than the number of all the batteries. As in the bidirectional battery balancing system of claim 1, wherein the control module estimates the state of charge by using the battery state estimation module to calculate the relationship between the battery voltage change and the battery current change during the current draw of the battery . For example, the bidirectional battery balancing system of claim 1, wherein the control module estimates the state of the battery by using a Kalman filter, neural network, genetic algorithm or multi-level resistance-capacitance equivalent modeling, etc. The estimation method realizes electricity estimation.

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