Double-row multi-flying capacitor voltage balancing system and capacity setting method thereof

Abstract

The invention relates to a double-row multi-flying capacitor voltage balancing system and a capacity setting method thereof, the double-row multi-flying capacitor voltage balancing system comprises n levels of balancing units which are arranged in sequence, and each balancing unit comprises a flying capacitor, a super capacitor and a bipolar switch; the super capacitors in any two adjacent equalization units are connected in series, and the flying capacitors in any two adjacent equalization units are connected in series. One electrode of the bipolar switch in the first-stage balancing unit is electrically connected with the positive electrode of the super capacitor, and one electrode of the bipolar switch in each of the rest stages of balancing units is electrically connected with the negative electrode of the previous stage of super capacitor and the positive electrode of the same stage of super capacitor; a double-row structure is formed by adding a row of flying capacitors, so that the current flowing path is increased, the ineffective energy flow is effectively reduced, and the voltage balancing speed is remarkably accelerated.

Description

Technical Field

[0001] The present invention relates to the technical field of battery equalization, and in particular to a dual-row multi-flying capacitor voltage equalization system and a capacity setting method thereof. Background Art

[0002] In modern battery management systems (BMS), voltage balance of each unit is a key issue when batteries or supercapacitors are used in series. Due to factors such as manufacturing process and material properties, the capacity and performance of each battery or supercapacitor will be different. During the series charging and discharging process, this difference will lead to voltage imbalance of each unit. This will not only reduce the overall performance of the battery pack, but also shorten its service life and even cause safety hazards. Therefore, achieving voltage balance of series-connected batteries or supercapacitors is crucial to improving system performance and safety.

[0003] Currently, voltage balancing technology is mainly divided into two categories: passive balancing and active balancing:

[0004] 1. Passive balancing: The energy of the high-voltage unit is consumed through the discharge resistor to reduce its voltage to the same level as other units. This method has a simple structure and low cost, but there is a problem of energy waste and the overall efficiency is low.

[0005] 2. Active balancing: voltage balancing is achieved through energy transfer, transferring the energy of the high-voltage unit to the low-voltage unit; common active balancing methods include inductive balancing and capacitive balancing; among them, the flying capacitor voltage balancing scheme is a typical active balancing method, which transfers the energy of the high-voltage unit to the capacitor by controlling the on-off of the switch tube, and then the capacitor transfers the energy to the low-voltage unit.

[0006] Although the flying capacitor voltage equalization solution solves the problem of voltage imbalance to a certain extent, it still has the following limitations in practical applications:

[0007] 1. Ineffective energy flow: When there are a large number of cells in series, energy needs to be transferred through multiple capacitors, resulting in increased ineffective energy flow; for example, when energy is transferred from the battery cell with the highest voltage to the cell with the lowest voltage, it will pass through many other cells, which will cause energy loss.

[0008] 2. Long balancing time: Due to the existence of invalid energy flow, the voltage balancing process is relatively slow, especially when the voltage difference between adjacent cells is small, the balancing speed drops significantly.

[0009] 3. Lack of guidance on capacity setting: The existing technology lacks detailed guidance on the selection and setting methods of flyback capacitor capacity, which makes it difficult for designers to determine the optimal capacitor capacity in practical applications, thus affecting the balancing effect.

[0010] Therefore, it urgently needs to be resolved. Summary of the invention

[0011] In view of the current status of the above-mentioned prior art, the technical problem to be solved by the present invention is to provide a dual-row multi-flying capacitor voltage balancing system and its capacity setting method which effectively reduces the flow of invalid energy and significantly speeds up the voltage balancing speed, and also provides a capacity setting method to optimize the performance of the balancing circuit.

[0012] The technical solution adopted by the present invention to solve the above technical problems is: a dual-row multi-flying capacitor voltage equalization system, characterized in that it includes n levels of equalization units arranged in sequence, and the equalization units include a flying capacitor, a super capacitor and a bipolar switch;

[0013] The supercapacitors in any two adjacent balancing units are connected in series with each other, and the flyback capacitors in any two adjacent balancing units are connected in series with each other;

[0014] One of the electrodes of the bipolar switch in the first-level balancing unit is electrically connected to the positive electrode of the supercapacitor, and one of the electrodes of the bipolar switch in each of the remaining balancing units is electrically connected to the negative electrode of the previous-level supercapacitor and the positive electrode of the supercapacitor in the same level;

[0015] The moving contact of the bipolar switch in the first-level balancing unit is electrically connected to the positive electrode of the same-level flyback capacitor, and the moving contact of the bipolar switch in each of the remaining balancing units is electrically connected to the negative electrode of the previous-level flyback capacitor and the positive electrode of the same-level flyback capacitor;

[0016] The other electrode of the bipolar switch in each level of balancing unit is electrically connected to the negative electrode of the super capacitor of the same level and the positive electrode of the super capacitor of the next level.

[0017] A capacity setting method for a dual-row multi-flying capacitor voltage equalization system, characterized in that it comprises the following steps:

[0018] S1: Under two pulse states, list the mesh current formula:

[0019]

[0020] The above solution can be converted into the voltage equation of the capacitor in the frequency domain, and the formula (2) is obtained:

[0021]

[0022] S2: Convert the frequency domain voltage equation into the time domain, convert D1T and D2T into states A and B at time T respectively, and then solve the six equations for the initial voltage of the capacitor at the same time;

[0023] S3: According to the discharge time matrix, the initial discharge voltage, the end voltage, the single cell capacity of the supercapacitor, and the resistance value of the resistor are calculated to obtain the calculation formula (3) of the balancing current:

[0024]

[0025] S4: After simplifying formula (3), we get formula (4), f sw is the switching frequency, V' CA and V' CB They are the voltages of the flying capacitor in state A and state B, as shown below:

[0026]

[0027] S5: After transformation, the capacity setting formula (5) is obtained as shown below:

[0028]

[0029] Preferably, in step S3, the time average current through any capacitor path is calculated based on its frequency, capacitance value and its change in end-state voltage.

[0030] Compared with the prior art, the present invention has the advantages that: by adding a column of flying capacitors to form a double-column structure, the present invention not only increases the path through which the current flows, effectively reduces the flow of invalid energy, but also significantly accelerates the voltage balancing speed.

[0031] In addition, the present invention provides a capacity setting principle and method of a dual-row multi-flying capacitor by deducing a mathematical formula, providing clear guidance for practical design, thereby optimizing the performance of the balancing circuit.

[0032] The present invention significantly improves the speed and efficiency of voltage equalization while maintaining a simple circuit structure, overcomes the main defects in the prior art, is applicable to series systems of various batteries and supercapacitors, and has broad application prospects and market potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the topological structure of the present invention;

[0034] Figure 2 It is the waveform diagram of the driver control signal;

[0035] Figure 3 It is the mesh current diagram of the present invention in state A;

[0036] Figure 4 It is the mesh current diagram of the present invention in state B;

[0037] Figure 5It is a voltage waveform diagram of the flyback capacitor of the present invention;

[0038] Figure 6 This is the simulation result diagram of the multi-flying capacitor voltage equalization solution;

[0039] Figure 7 This is the maximum overvoltage diagram of the battery in the multi-fly capacitor voltage equalization solution;

[0040] Figure 8 This is the voltage equalization stability diagram of the multi-flying capacitor voltage equalization solution;

[0041] Fig. 9 It is a diagram of the equalization simulation result of the present invention;

[0042] Fig.10 It is the maximum overvoltage diagram of the battery of the present invention;

[0043] Fig.11 This is the voltage balance stability diagram of the present invention. DETAILED DESCRIPTION

[0044] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0045] In order to keep the following description of the embodiments of the present invention clear and concise, detailed descriptions of well-known functions and well-known components are omitted.

[0046] like Figures 1-2 As shown, a dual-row multi-flying capacitor voltage equalization system includes n-level equalization units arranged in sequence, and the equalization unit includes a flying capacitor, a super capacitor and a bipolar switch;

[0047] The supercapacitors in any two adjacent balancing units are connected in series, and the flying capacitors in any two adjacent balancing units are connected in series;

[0048] One of the electrodes of the bipolar switch in the first-stage balancing unit is electrically connected to the positive electrode of the supercapacitor, and one of the electrodes of the bipolar switch in each of the remaining balancing units is electrically connected to the negative electrode of the previous-stage supercapacitor and the positive electrode of the supercapacitor in the same stage;

[0049] The moving contact of the bipolar switch in the first-stage balancing unit is electrically connected to the positive electrode of the same-stage flyback capacitor, and the moving contact of the bipolar switch in each of the remaining balancing units is electrically connected to the negative electrode of the previous-stage flyback capacitor and the positive electrode of the same-stage flyback capacitor;

[0050] The other electrode of the bipolar switch in each level of balancing unit is electrically connected to the negative electrode of the supercapacitor of the same level and the positive electrode of the supercapacitor of the next level;

[0051] Working principle:

[0052] like Figures 3 to 5 As shown, taking n=3 as an example, C1, C2, and C3 are supercapacitors, C f1 , C fn-1 , C fn It is a flying capacitor, and the two capacitors are connected by a switch tube; its working principle is: when state A comes, the switch is closed upward, at this time C1 and C f1 Connect in parallel to form a loop, C2 and C fn-1 Connect in parallel to form a loop, C f1 , C fn-1 and C fn The series connection forms a loop. After the D1T period ends, the voltages across the flyback capacitor and the supercapacitor will be basically equal. When state B comes, the switch is closed downward, and C2 and C f1 Parallel, C n With C fn-1 Parallel, C f1 , C fn-1 and C fn A loop is also formed in series. After the D2T period, the voltages at both ends of the flyback capacitor and the supercapacitor are basically equal. After several pulses, the supercapacitors C1, C2, and C n The voltage across the terminals will be approximately equal.

[0053] The advantage of this method is that when the supercapacitor and the flyback capacitor are voltage-balanced, the three flyback capacitors C f1 , C fn-1 , C fn The voltage is also equalized between each other to achieve voltage balance; then when other pulses arrive, the speed of voltage balancing will become faster, which improves work efficiency and greatly saves time.

[0054] In order to facilitate the calculation, we convert the balanced voltage value between the supercapacitor and the flying capacitor into the transmission of average current between the two capacitors. At the same time, in order to meet our needs, we perform an equivalent transformation of the circuit.

[0055] We equate the switch to two resistors R with equal resistance, and the series resistance rc of all capacitors is equal. For the specific mesh current diagram, see Figure 3 and Figure 4 .

[0056] Due to the different pulses, the switch reaches different positions and has two states, A or B (see Figure 2 ), the equivalent circuits of the two states A and B are shown in FIG.

[0057] Through the action of the switch, the supercapacitor and the flyback capacitor are fully charged and discharged, so that the voltage of any capacitor cycles from one pulse cycle to the next pulse cycle.

[0058] In this case, the voltage at which any capacitor in the circuit is in state A after time D1T is the starting voltage of the capacitor in state B, and the ending voltage of state B at D2T is the starting voltage of state A, respectively expressed as V'. CA and V' CB To indicate, see Figure 5 .

[0059] A capacity setting method for a dual-row multi-flying capacitor voltage equalization system comprises the following steps:

[0060] S1: Under two pulse states, list the mesh current formula:

[0061]

[0062] The above solution can be converted into the voltage equation of the capacitor in the frequency domain, as shown in the following formula (2):

[0063]

[0064] S2: Convert the frequency domain voltage equation into the time domain, convert D1T and D2T into states A and B at time T respectively, and then solve the six equations for the initial voltage of the capacitor at the same time;

[0065] S3: According to the discharge time matrix, the initial discharge voltage, the end voltage, the single capacity of the supercapacitor, and the resistance value of the resistor are calculated to obtain the calculation formula of the balancing current, as shown in the following formula (3):

[0066]

[0067] The time-averaged current through any capacitor path is calculated based on its frequency, capacitance value and its change in end-state voltage.

[0068] S4: After simplifying formula (3), we get formula (4), f sw is the switching frequency, V' CA and V' CB They are the voltages of the flying capacitor in state A and state B, as shown below:

[0069]

[0070] S5: After transformation, the capacity setting formula (5) is obtained as shown below:

[0071]

[0072] like Figures 6 to 11 As shown, the simulation software PSIM is used to simulate and verify the multi-flying capacitor voltage balancing solution and the dual-row multi-flying capacitor voltage balancing solution; compared from the two perspectives of maximum overvoltage value and balancing stabilization time, the dual-row flying capacitor voltage balancing solution is obviously superior.

[0073] The following is a comparison table between the present invention and the multi-fly capacitor voltage equalization solution:

[0074] Serial number Initial voltage U / V Initial capacity C / F Multi-fly capacitor voltage U / V at time t1 Voltage U / V of double-row multi-flying capacitor at time t2 1 0 14.4 16.01 16.01 2 0.7 15 16.00 16.01 3 0.1 17 16.00 16.00 4 0.3 18 15.99 16.00 5 0.4 19 15.99 15.99 6 0.2 20 15.99 15.99 Voltage balancing time t / s 146.07 139.34

[0075] The present invention overcomes the main defects of the prior art through an innovative dual-row multi-flying capacitor voltage equalization solution, and brings the following beneficial effects:

[0076] 1. Improve voltage balancing efficiency;

[0077] Reduce invalid energy flow: The double-row structure increases the path for current to flow, reducing the number of times the energy passes through other units during the energy transfer process, thereby reducing the loss in energy transfer.

[0078] Accelerate the voltage balancing process: Due to the reduction of ineffective energy flow, the voltage balancing process is more efficient, significantly shortening the balancing time and improving the overall performance of the system.

[0079] 2. Optimize the capacitance setting;

[0080] Scientific capacity setting method: Through mathematical formula derivation, the setting principle and method of double-row multi-fly capacitor capacity are proposed, providing clear guidance for designers. This ensures that the appropriate capacitor capacity can be selected in different application scenarios to optimize circuit performance.

[0081] Improve design flexibility: The provided setting method enables designers to adjust the capacitance according to specific application requirements and flexibly cope with different working environments and battery types.

[0082] 3. Improve system reliability;

[0083] Simple and reliable structure: despite the introduction of a double-row structure, the present invention maintains the simplicity of the circuit, reduces potential failure points, and improves the reliability of the system.

[0084] Strong adaptability: The dual-row multi-fly capacitor solution is suitable for various types of batteries and supercapacitors, and can be widely used in various application scenarios such as electric vehicles, energy storage systems, and portable electronic devices.

[0085] 4. Energy saving and environmental protection;

[0086] High energy utilization rate: By reducing the loss in the energy transfer process, the energy utilization rate is improved, the energy consumption of system operation is reduced, and it helps to achieve the goal of energy conservation and environmental protection.

[0087] Extend battery life: Effective voltage balancing extends the service life of battery cells, reduces the frequency of battery replacement, and thus reduces the generation of electronic waste, which is of environmental significance.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dual-row multi-flying capacitor voltage equalization system, characterized in that: It comprises n levels of balancing units arranged in sequence, wherein the balancing units comprise a flying capacitor, a super capacitor and a bipolar switch; The supercapacitors in any two adjacent balancing units are connected in series with each other, and the flyback capacitors in any two adjacent balancing units are connected in series with each other; One of the electrodes of the bipolar switch in the first-level balancing unit is electrically connected to the positive electrode of the supercapacitor, and one of the electrodes of the bipolar switch in each of the remaining balancing units is electrically connected to the negative electrode of the previous-level supercapacitor and the positive electrode of the supercapacitor in the same level; The moving contact of the bipolar switch in the first-level balancing unit is electrically connected to the positive electrode of the same-level flyback capacitor, and the moving contact of the bipolar switch in each of the remaining balancing units is electrically connected to the negative electrode of the previous-level flyback capacitor and the positive electrode of the same-level flyback capacitor; The other electrode of the bipolar switch in each level of balancing unit is electrically connected to the negative electrode of the super capacitor of the same level and the positive electrode of the super capacitor of the next level.

2. A capacity setting method for a dual-row multi-flying capacitor voltage equalization system, characterized in that: The following steps are involved: S1: Under two pulse states, list the mesh current formula: The above solution can be converted into the voltage equation of the capacitor in the frequency domain, and the formula (2) is obtained: S2: Convert the frequency domain voltage equation into the time domain, convert D1T and D2T into states A and B at time T respectively, and then solve the six equations for the initial voltage of the capacitor at the same time; S3: According to the discharge time matrix, the initial discharge voltage, the end voltage, the single cell capacity of the supercapacitor, and the resistance value of the resistor are calculated to obtain the calculation formula (3) of the balancing current: S4: After simplifying formula (3), we get formula (4), f sw is the switching frequency, V' CA and V' CB They are the voltages of the flying capacitor in state A and state B, as shown below: S5: After transformation, the capacity setting formula (5) is obtained as shown below:

3. The capacity setting method of the dual-row multi-flying capacitor voltage equalization system according to claim 2 is characterized in that: In step S3, the time average current through any capacitor path is calculated based on its frequency, capacitance value and its change in end-state voltage.

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