Battery online capacity checking system based on half-bridge LLC

Abstract

The utility model discloses a half-bridge LLC-based battery on-line capacity checking system, relates to the field of electric power conversion, and solves the problems that a post-stage load device has a power failure risk and an abnormal battery cannot be rapidly positioned in the capacity checking operation switching period of an existing capacity checking device. According to the technical scheme, the system is characterized by comprising a plurality of to-be-tested batteries, an electric switch device and a plurality of capacity checking devices, a plurality of batteries to be tested are connected in series and then connected to a direct current bus through an electric switch device, each battery to be tested is connected in parallel with a capacity checking device, and the capacity checking devices are connected with the direct current bus; the capacity checking device carries out charge and discharge capacity checking on a to-be-tested battery based on a half-bridge LLC structure. The capacity checking device based on the half-bridge LLC topology is additionally arranged, parallel capacity checking is carried out on a single battery, online capacity checking is achieved, redundant and complex switching operation is not needed, capacity checking can be carried out on one or more batteries, the risk of load power failure can be greatly reduced, and the abnormal condition of a certain battery can be rapidly known.

Description

Technical Field

[0001] This utility model relates to the field of power conversion, and more specifically, it relates to an online battery capacity control system based on a half-bridge LLC. Background Technology

[0002] Battery capacity assessment devices are primarily used for real-time monitoring and evaluation of battery capacity and health status. They perform capacity-controlled discharge on batteries to simulate real-world usage scenarios and verify battery capacity and performance. Commercially available batteries typically consist of multiple cells connected in series to form a high-voltage DC circuit. A common method for battery capacity assessment is to connect the battery to a load via a switching switch for discharge capacity assessment. However, during the switching operation, downstream load equipment faces a significant risk of power loss. Furthermore, if capacity assessment fails, it is difficult to quickly and accurately identify which battery is malfunctioning. Additionally, the switching operation is complex and prone to misoperation.

[0003] Therefore, this application proposes an online battery capacity control system based on a half-bridge LLC to solve the above problems. Utility Model Content

[0004] The technical problem this application aims to solve is that existing capacity balancing devices pose a significant risk of power loss to downstream load equipment during capacity balancing operations. Furthermore, when capacity balancing fails, it is impossible to quickly and accurately identify which battery cell is malfunctioning. Additionally, the switching operations are complex and prone to misoperation. This application adds a capacity balancing device based on a half-bridge LLC topology to the existing series-connected battery configuration. This allows for parallel capacity balancing of individual batteries, achieving online capacity balancing without the need for complex switching operations. It also allows for the designation of one or more batteries for capacity balancing, significantly reducing the risk of load power loss and enabling rapid identification of any battery malfunction.

[0005] This application is achieved through the following technical solution:

[0006] The battery online capacity verification system based on half-bridge LLC includes: multiple batteries under test, an electric switch device, and multiple capacity verification devices; the multiple batteries under test are connected in series and then connected to a DC bus through the electric switch device, and a capacity verification device is connected in parallel to each battery under test, and the capacity verification device is connected to the DC bus; wherein, the capacity verification device performs charge and discharge capacity verification of the battery under test based on the half-bridge LLC structure.

[0007] As one possible implementation, the nuclear capacity device includes: a reverse connection protection circuit, a half-bridge LLC, an auxiliary power supply circuit, a control circuit, a communication circuit, and a sampling circuit; one end of the reverse connection protection circuit is used to connect to the battery under test, and the other end is connected to the half-bridge LLC. The half-bridge LLC is used to connect to the DC bus. Both the DC bus and the battery under test are connected to the auxiliary power supply circuit. The auxiliary power supply circuit is connected to the control circuit. The control circuit is connected to the control terminal of the half-bridge LLC. The control circuit is also connected to the communication circuit and the sampling circuit.

[0008] As one possible implementation, the half-bridge LLC includes: an inverter network, a resonant network, a transformer, and a rectifier-filter network. The inverter network is connected to the resonant network, the resonant network is connected to the primary side of the transformer, and the secondary side of the transformer is connected to the rectifier-filter network through a center tap.

[0009] As one possible implementation, the input of the inverter network is connected to the DC bus, and the output of the rectifier filter network is connected to the reverse connection protection circuit.

[0010] As one possible implementation, the inverter network consists of two MOSFETs, their body diodes, and parasitic capacitances.

[0011] As one possible implementation, the inverter network employs two N-MOSFETs.

[0012] In one possible implementation, the nuclear capacity device has two states: standby or operation, and the state switching of the nuclear capacity device is determined by the state of the electric switching device.

[0013] As one possible implementation, when the electric switch is in the engaged state, the capacity storage device switches to standby state; when the electric switch is in the disengaged state, the capacity storage device switches to operating state.

[0014] In one possible implementation, the battery under test is a lead-acid battery, a lithium battery, or a sodium battery.

[0015] In one possible implementation, the battery under test consists of 108 2V dc batteries with a DC bus of 220V dc.

[0016] Compared with the prior art, this application has the following advantages: In the case of the original battery series connection, a capacity-limiting device based on a half-bridge LLC topology is added, and the capacity-limiting device is connected in parallel with the battery to perform parallel capacity-limiting of a single battery, realizing online capacity-limiting. There is no need for complicated switching operations. It is also possible to specify one or more batteries for individual capacity-limiting without affecting the operation of the entire system. This greatly reduces the risk of load power failure in traditional capacity-limiting and can quickly identify the abnormal situation of a battery. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present invention and form part of this application, do not constitute a limitation on the embodiments of this application. In the drawings:

[0018] Figure 1 A structural diagram of a battery online capacity balancing system based on a half-bridge LLC provided in an embodiment of this application;

[0019] Figure 2 A structural diagram of the nuclear capacity device provided in the embodiments of this application;

[0020] Figure 3 This is a structural diagram of a half-bridge LLC provided in an embodiment of this application;

[0021] Figure 4 This is a schematic diagram of the working waveform of a half-bridge LLC;

[0022] Figure 5 This is a diagram showing the operating states of each component in a half-bridge LLC during the T0 to T1 operating phase.

[0023] Figure 6 This is a diagram showing the operating states of each component in a half-bridge LLC during the T1 to T2 operating phases.

[0024] Figure 7 This is a diagram showing the operating states of each component in a half-bridge LLC during the T2 to T3 operating phases.

[0025] Figure 8 This is a diagram showing the operating status of each component in a half-bridge LLC during the T3 to T4 operating phases.

[0026] Figure 9 This is a diagram showing the operating status of each component in a half-bridge LLC during the T4 to T5 operating phase.

[0027] Figure 10 This is a diagram showing the operating status of each component in a half-bridge LLC during the T5 to T6 operating phases. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this utility model are only used to explain this utility model and are not intended to limit this utility model.

[0029] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly or indirectly attached to that other component. When a component is referred to as being "connected to" another component, it can be directly or indirectly connected to that other component.

[0030] Please see Figure 1 As shown, Figure 1 This is a structural diagram of an online battery capacity verification system based on a half-bridge LLC, provided in an embodiment of this application. The online battery capacity verification system includes: multiple batteries under test, an electric switch, and multiple capacity verification devices; the multiple batteries under test are connected in series and then connected to a DC bus via the electric switch; each battery under test is connected in parallel with a capacity verification device, which is connected to the DC bus; wherein, the capacity verification device performs charge-discharge capacity verification on the battery under test based on a half-bridge LLC structure.

[0031] Specifically, commercially available systems often use multiple batteries connected in series to a DC bus to power downstream equipment loads. The purpose of this application is to perform online charge-discharge capacity verification on these batteries. In the capacity verification system, multiple batteries are connected in series to a DC bus for power supply; an electric switch controls the connection of the batteries to the DC bus, opening during charge-discharge capacity verification testing and closing when the test ends; the capacity verification device is connected in parallel with a single battery, allowing for individual charge-discharge capacity verification of the battery.

[0032] The working logic of this application is as follows: During normal operation, the capacity accumulator is in standby mode, the electric switch is engaged, and multiple batteries are connected in series to the DC bus to supply power to the downstream equipment load through the electric switch. When capacity accumulator is required, the capacity accumulator operates, and the electric switch is disengaged to cut off the battery series circuit and switch to parallel operation mode. The capacity accumulator charges and discharges the battery cells for capacity accumulator. After the capacity accumulator is completed, the electric switch is engaged, the capacity accumulator is in standby mode, and switches back to series operation mode.

[0033] The improvement of this application lies in the addition of a capacity-capacitance device based on a half-bridge LLC topology to the original series battery configuration, and the capacity-capacitance device is connected in parallel with the battery to perform parallel capacity-capacitance on a single battery, realizing online capacity-capacitance without the need for complicated switching operations. It can also specify one or more batteries for individual capacity-capacitance without affecting the operation of the entire system, greatly reducing the risk of load power failure present in traditional capacity-capacitance, and can quickly detect abnormal conditions of a battery.

[0034] Please see Figure 2 As shown, Figure 2 This is a structural diagram of a capacity testing device provided in an embodiment of this application. As one possible implementation, the capacity testing device includes: a reverse connection protection circuit, a half-bridge LLC, an auxiliary power supply circuit, a control circuit, a communication circuit, and a sampling circuit. One end of the reverse connection protection circuit is connected to the battery under test, and the other end is connected to the half-bridge LLC. The half-bridge LLC is connected to the DC bus. Both the DC bus and the battery under test are connected to the auxiliary power supply circuit. The auxiliary power supply circuit is connected to the control circuit. The control circuit is connected to the control terminal of the half-bridge LLC. The control circuit is also connected to the communication circuit and the sampling circuit.

[0035] Specifically, in the capacity balancing device, the reverse connection protection circuit is mainly used for reverse connection protection on the battery side. Compared with traditional DC converters, the half-bridge LLC has higher efficiency and power density. During charging capacity balancing, the half-bridge LLC converts the high-voltage DC power from the DC bus into a DC voltage suitable for the battery. During discharging capacity balancing, the half-bridge LLC feeds energy back from the battery to the DC bus, which can meet the requirements of boosting the battery's discharge voltage and also stepping down the high-voltage DC power from the DC bus to the battery voltage to charge the battery, thereby realizing the charge and discharge capacity balancing of a single battery. The auxiliary power supply circuit mainly supplies power through the battery or the DC bus, and then supplies power to the control circuit. In the case of battery discharging capacity balancing, the battery is used first, and the voltage is boosted to supply power to the control circuit. After the high voltage of the DC bus is established, the DC bus is used for power supply, and the voltage is reduced to supply power to the control circuit. The control circuit mainly generates waves for driving the power transistors of the half-bridge LLC, thereby controlling the system's operating logic and realizing the charge and discharge capacity balancing of the battery. The sampling circuit and communication circuit are not improvements in this application and can directly use existing circuit modules, so they will not be described in detail here.

[0036] The improvement of this application lies in the adoption of a high-efficiency half-bridge LLC topology, which enables efficient and stable energy conversion between the high-voltage DC bus and the low-voltage battery under test, and achieves DC-to-DC isolation conversion, making it widely applicable to uninterrupted DC power supply for control equipment. Furthermore, the capacity unit can be configured with other related additional functions such as BMS, charge / discharge management, and automatic switching.

[0037] Please see Figure 3 As shown, Figure 3 This is a structural diagram of a half-bridge LLC provided in an embodiment of this application. The half-bridge LLC includes: an inverter network, a resonant network, a transformer, and a rectifier-filter network. The inverter network is connected to the resonant network, the resonant network is connected to the primary side of the transformer, and the secondary side of the transformer is connected to the rectifier-filter network through a center tap.

[0038] Furthermore, the input of the inverter network is connected to the DC bus, and the output of the rectifier filter network is connected to the reverse connection protection circuit.

[0039] Furthermore, the inverter network consists of two MOSFETs (Q1 and Q2), their body diodes (DQ1 and DQ2), and parasitic capacitors (CQ1 and CQ2). The resonant network consists of a magnetizing inductor Lm, a resonant inductor Lr, and resonant capacitors C1 and C2. The secondary winding of transformer T1 requires a center tap. The rectifier filter network consists of an output filter capacitor C0.

[0040] Furthermore, the inverter network employs two N-MOSFETs.

[0041] Specifically, Figure 3In the diagram, Vin is the high voltage on the DC bus side, and Vout is the battery side voltage; Lr is the primary resonant inductance, which also includes the primary leakage inductance; C1 and C2 are the primary resonant capacitors, which, together with the resonant inductance, generate a high-frequency resonant frequency; and the transformer's magnetizing inductance is Lm. Power flow direction: from left to right is the power supply mode, with positive flow; from right to left is the charging mode, with negative flow.

[0042] When the primary-side switch transfers energy, the primary-side main switch operates in inverter mode. Here, we only discuss the secondary-side asynchronous rectification method, i.e., diode rectification mode. Below, we analyze one energy transfer direction: the power supply mode from the primary side to the secondary side. In the charging mode where energy is transferred from the secondary side to the primary side, the circuit principle and efficiency are completely the same.

[0043] In general, the switching action of the LLC half-bridge resonant circuit is no different from that of the half-bridge circuit. However, due to the addition of the resonant cavity, the operation of the upper and lower MOSFETs in the LLC half-bridge resonant circuit is quite different; it can achieve zero-voltage turn-on of the MOSFETs. Its operating waveform is shown in Figure 4. Figure 4 This is a schematic diagram of the working waveform of a half-bridge LLC.

[0044] Figure 4 In the diagram, Vgs1 and Vgs2 are the driving waveforms of Q1 and Q2, respectively; Ir is the inductor current waveform of the resonant inductor Lr; Im is the current waveform of the transformer leakage inductance Lm; Id1 and Id2 are the waveforms of the secondary-side output rectifier diodes; and Ids1 is the conduction current of Q1. The waveform diagram is divided into 6 stages according to different operating states. The following is a detailed analysis of each state and the operation of the LLC resonant circuit:

[0045] T0~T1: Q1 is off, Q2 is on; at this time, the current in the resonant inductor is negative and flows towards Q2. During this stage, the transformer's magnetizing inductance does not participate in the resonance; Cr and Lr form the resonant frequency, and the output energy comes from Cr and Lr. This stage ends when Q2 is turned off. Figure 5 This is a diagram showing the operating states of each component in a half-bridge LLC during the T0 to T1 operating phases.

[0046] T1~T2: Q1 and Q2 are both off. This is the dead time of the half-bridge circuit. The current in the resonant inductor is still negative. The resonant current discharges the output capacitor (CQ1) of Q1 and charges the output capacitor (CQ2) of Q2 until the voltage of the output capacitor of Q2 equals the input voltage (Vin), creating the condition for zero-voltage turn-on of Q1. Since the body diode of Q1 is forward biased and the body diode of Q2 is reverse biased, the current in the two inductors is equal. The output voltage is higher than the secondary voltage of the transformer, so D1 and D2 are reverse biased, and the output terminal is disconnected from the transformer. During this stage, Lm, Lr, and Cr participate in the resonance. As Q1 turns on, the T1~T2 stage ends. Figure 6 This is a diagram showing the operating status of each component in a half-bridge LLC during the T1 to T2 operating phases.

[0047] T2~T3: Q1 is on, Q2 is off (once the output capacitor of Q1 is discharged to zero). At this time, the current in the resonant inductor is still negative, flowing back to the input terminal (Vin) through Q1. Simultaneously, the output rectifier diode (D1) is turned on, providing energy to the output terminal. The transformer magnetizing inductor (Lm) is continuously charged during this stage. Only Lr and Cr participate in resonance. The T2~T3 stage ends once the current in the resonant inductor Lr reaches zero. Figure 7 This is a diagram showing the operating status of each component in a half-bridge LLC during the T2 to T3 operating phases.

[0048] T3-T4: This stage begins when the current in the resonant inductor Lr changes from negative to positive, Q1 turns on, and Q2 turns off, similar to the T2-T3 stage. The resonant inductor current begins to flow from the input terminal through Q1 to ground. The transformer leakage inductance Lm is charged by this current, so only Lr and Cr participate in the resonance. Energy is still transferred at the output terminal by D1. The T3-T4 stage ends when Q1 turns off. (Continue below) Figure 8 This is a diagram showing the operating status of each component in a half-bridge LLC during the T3 to T4 operating phases.

[0049] T4~T5: Q1 is off, Q2 is off; this is the dead time of the half-bridge circuit. During this time, the resonant inductor current charges the output capacitor CQ1 of Q1 and discharges the output capacitor CQ2 of Q2 until the voltage across the output capacitor of Q2 is zero, turning on the body diode of Q2 and creating conditions for Q2 to turn on at zero voltage. During this period, the secondary side of the transformer is disconnected from the primary side, just like in the T1~T2 stage. During the dead time, the transformer leakage inductance Lm participates in resonance. This stage ends when Q2 turns on. Figure 9 This is a diagram showing the operating status of each component in a half-bridge LLC during the T4 to T5 operating phases.

[0050] T5~T6: Q1 is off, Q2 is on. Since the output capacitor of Q2 has been discharged to zero during T4~T5, Q2 is turned on with zero voltage during T5~T6. Energy is supplied by the resonant inductor Lr through Q2 freewheeling, and the output terminal is powered by D2. At this time, Lm does not participate in the resonance of Lr and Cr. This stage ends when the current in the resonant inductor Lr becomes zero, and the T0~T1 state is repeated. Figure 10 This is a diagram showing the operating status of each component in a half-bridge LLC during the T5 to T6 operating phases.

[0051] Depend on Figure 4-10 As shown in the diagram, except for the dead times of Q1 and Q2, the circuit can operate at a relatively high resonant frequency formed by Lr and Cr for most of the time. In this case, the transformer leakage inductance, clamped by the output voltage, exists as a load in the Lr and Cr series resonant cavity and does not participate in the entire resonance process. Due to this passive load, the LLC resonant converter no longer needs a very high frequency for light-load voltage regulation. Moreover, due to this passive Lm load, it can be guaranteed to operate in a zero-voltage switching state under any load condition.

[0052] In one possible implementation, the nuclear capacity device has two states: standby or operation, and the state switching of the nuclear capacity device is determined by the state of the electric switching device.

[0053] Furthermore, when the electric switch is in the engaged state, the capacity verification device switches to standby mode; when the electric switch is in the disengaged state, the capacity verification device switches to operating mode. It is understood that the electric switch capacity verification device can cooperate with monitoring equipment, controlling the electric switch to engage or disengage based on capacity verification commands issued by the monitoring system, eliminating the need for manual operation and reducing the risk of misoperation. When capacity verification is required, the electric switch is disengaged, and the capacity verification device operates to perform charge and discharge capacity verification on individual battery cells; after verification is complete, the electric switch is engaged, and the capacity verification device enters standby mode.

[0054] In one possible implementation, the battery under test is a lead-acid battery, a lithium battery, or a sodium battery.

[0055] In one possible implementation, the battery under test uses 108 2V DC batteries, with a DC bus of 220V DC. The online capacity verification system of this application can realize online automatic charging and discharging capacity verification of batteries from 2V to 220V.

[0056] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this utility model. It should be understood that the above description is only a specific embodiment of this utility model and is not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A battery on-line capacity determination system based on half-bridge LLC, characterized in that, include: Multiple batteries under test, electric switching device, and multiple capacity devices; Multiple batteries under test are connected in series and then connected to the DC bus via the electric switch device. Each battery under test is connected in parallel with a capacity device, which is connected to the DC bus. The capacity-integrating device is based on a half-bridge LLC structure to perform charge-discharge capacity integration of the battery under test.

2. The half bridge LLC based battery on-line state of charge system of claim 1, wherein, The nuclear capacity device includes: a reverse connection protection circuit, a half-bridge LLC, an auxiliary power supply circuit, a control circuit, a communication circuit, and a sampling circuit; One end of the reverse connection protection circuit is used to connect to the battery under test, and the other end is connected to the half-bridge LLC. The half-bridge LLC is used to connect to the DC bus. Both the DC bus and the battery under test are connected to the auxiliary power circuit. The auxiliary power circuit is connected to the control circuit. The control circuit is connected to the control terminal of the half-bridge LLC. The control circuit is also connected to the communication circuit and the sampling circuit.

3. The half bridge LLC based battery on-line state of charge system of claim 2, wherein, The half-bridge LLC includes an inverter network, a resonant network, a transformer, and a rectifier-filter network. The inverter network is connected to the resonant network, the resonant network is connected to the primary side of the transformer, and the secondary side of the transformer is connected to the rectifier-filter network through a center tap.

4. The half bridge LLC based battery on-line state of charge system of claim 3, wherein, The input terminal of the inverter network is connected to the DC bus, and the output terminal of the rectifier filter network is connected to the reverse connection protection circuit.

5. The half bridge LLC based battery on-line state of charge system of claim 3, wherein, The inverter network consists of two MOSFETs, their body diodes, and parasitic capacitances.

6. The half bridge LLC based battery on-line state of charge system of claim 5, wherein, The inverter network uses two N-MOSFETs.

7. The half bridge LLC based battery on-line state of charge system of claim 1, wherein, The nuclear capacity device has two states: standby and operation. The state switching of the nuclear capacity device is determined by the state of the electric switching device.

8. The half bridge LLC based battery on-line state of charge system of claim 7, wherein, When the electric switch is in the engaged state, the capacity storage device switches to standby state; when the electric switch is in the disengaged state, the capacity storage device switches to operating state.

9. The half bridge LLC based battery on-line state of charge system of claim 1, wherein, The battery under test is a lead-acid battery, a lithium battery, or a sodium battery.

10. The half bridge LLC based battery on-line state of charge system of claim 1, wherein, The battery under test consists of 108 2V dc batteries, and the DC bus is 220V dc.

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