Two-stage three-level high-voltage battery charging and discharging device and control method

Abstract

The invention relates to a two-stage three-level high-voltage battery charging and discharging device and a control method. The two-stage three-level high-voltage battery charging and discharging device comprises an ACDC circuit connected with a power grid and used for converting alternating current into direct current; the DCDC circuit comprises a first capacitor, a second capacitor, a third capacitor and a first flying capacitor control circuit; the anode of the first capacitor is connected to the first flying capacitor control circuit through a first connection point, and the cathode of the first capacitor is connected with the anode of the second capacitor; the negative electrode of the second capacitor is connected to the first flying capacitor control circuit through a third connection point; the positive electrode of the third capacitor is connected to the first flying capacitor control circuit through a fourth connection point, and the negative electrode of the third capacitor is connected to the first flying capacitor control circuit through a fifth connection point; the first flying capacitor control circuit is connected to the ACDC circuit through a second connection point; and the LC filter circuit is connected with the DCDC circuit. The system stability and reliability are enhanced, and the test requirements of the high-voltage battery are met.

Description

Technical Field

[0001] The present application relates to the field of new energy technology, and in particular to a two-stage three-level high-voltage battery charging and discharging device and a control method. Background Art

[0002] With the rapid development of electric vehicles and electrochemical energy storage technology, batteries, as core components, need to undergo rigorous performance tests and safety tests to ensure their reliability and adaptability. In particular, the widespread application of high-voltage and large-capacity batteries has put forward higher requirements for battery testing equipment. In the existing market, high-voltage battery charge and discharge test devices are mainly based on a two-level topology: the first level is an ACDC circuit, which is used to connect to the power grid and convert AC power into DC power; the other level is a DCDC circuit, which is used to adjust the DC voltage to meet the battery's charging and discharging requirements. In ACDC and DCDC circuits, the three-level topology has gradually become the mainstream choice for high-voltage scenarios. Compared with the traditional two-level topology, the three-level topology can significantly reduce the voltage stress of the switching device, reduce switching losses, and improve power density, while showing better advantages in device size and cost. In particular, the flying capacitor design in the DCDC circuit achieves efficient operation of the circuit by sharing voltage and balancing energy, further improving the reliability and stability of the system.

[0003] Although three-level topology technology has been widely used in the field of energy storage, there is still room for improvement. For example, the voltage control of the flying capacitor needs to be more precise to ensure the efficient operation of the device under high voltage and high current conditions. At the same time, in order to adapt to the increasing testing needs, the system needs to take into account multiple factors such as high power density, low cost and maintenance convenience. These have put forward the need for further optimization of the existing two-stage three-level high-voltage battery charging and discharging device. Summary of the invention

[0004] In order to solve the above technical problems, the present application proposes a two-stage three-level high-voltage battery charging and discharging device and a control method.

[0005] In a first aspect, the present application provides a two-stage three-level high-voltage battery charging and discharging device, the device comprising: ACDC circuit, connected to the power grid, for converting AC power into DC power; A DCDC circuit, comprising a first capacitor, a second capacitor, a third capacitor and a first flying capacitor control circuit; the positive electrode of the first capacitor is connected to the first flying capacitor control circuit through a first connection point, and the negative electrode of the first capacitor is connected to the positive electrode of the second capacitor; the negative electrode of the second capacitor is connected to the first flying capacitor control circuit through a third connection point; the positive electrode of the third capacitor is connected to the first flying capacitor control circuit through a fourth connection point, and the negative electrode of the third capacitor is connected to the first flying capacitor control circuit through a fifth connection point; the first flying capacitor control circuit is connected to the ACDC circuit through a second connection point; The LC filter circuit is connected to the DCDC circuit.

[0006] Optionally, the DCDC circuit also includes a power tube T5, a power tube T6, a power tube T7, a power tube T8, a diode D5, a diode D6, a diode D7 and a diode D8, and the power tube T5 is connected in series with the power tube T6, the power tube T7 and the power tube T8 in sequence; the power tube T5 is connected in parallel with the diode D5, and one end of the power tube T5 is connected to the positive electrode of the third capacitor, and the other end is connected to the positive electrode of the first capacitor; the power tube T8 is connected in parallel with the diode D8, and one end of the power tube T8 is connected to the negative electrode of the third capacitor, and the other end is connected to the negative electrode of the second capacitor.

[0007] Optionally, the DCDC circuit further includes: A second flying capacitor control circuit is connected between the power tube T5 and the power tube T6 through a sixth connection point; or, The third flying capacitor control circuit is connected between the power tube T7 and the power tube T8 through a seventh connection point.

[0008] Optionally, the DCDC circuit also includes a fourth capacitor, a power tube T9, a power tube T10, a power tube T11 and a power tube T12, the power tube T9 is connected in series with the power tube T10, the power tube T11 and the power tube T12 in sequence; the positive electrode of the fourth capacitor is connected to the second flying control circuit or the third flying control circuit through an eighth connection point, and the negative electrode of the fourth capacitor is connected to the second flying control circuit or the third flying control circuit through a ninth connection point; the positive electrode of the fourth capacitor is also connected between the power tube T9 and the power tube T10, and the negative electrode of the fourth capacitor is also connected between the power tube T11 and the power tube T12.

[0009] Optionally, the first flying capacitor control circuit includes a power tube T1, a power tube T2, a power tube T3, a power tube T4, a diode D1, a diode D2, a diode D3 and a diode D4; the power tube T1 is connected in parallel with the diode D1, and one end of the power tube T1 is connected to the first connection point, and the other end is connected to the fourth connection point through a resistor R1; the power tube T2 is connected in parallel with the diode D2, and one end of the power tube T2 is connected to the second connection point, and the other end is connected to the fourth connection point through a resistor R2; the power tube T3 is connected in parallel with the diode D3, and one end of the power tube T3 is connected to the second connection point, and the other end is connected to the fifth connection point through a resistor R3; the power tube T4 is connected in parallel with the diode D4, and one end of the power tube T4 is connected to the third connection point, and the other end is connected to the fifth connection point through a resistor R4.

[0010] Optionally, when the power tube T5 is turned on, the power tube T8 is not turned on; when the power tube T8 is turned on, the power tube T5 is not turned on; When the power tube T5 is turned on, the power tube T1 and the power tube T3 are turned on; when the power tube T8 is turned on, the power tube T2 and the power tube T4 are turned on; the turn-on time of the power tube T1 and the power tube T3 is the same as that of the power tube T2 and the power tube T4.

[0011] Optionally, the second flying capacitor control circuit includes a power tube T9, a power tube T10, a diode D9, a diode D10, a resistor R5 and a resistor R6; the power tube T9 is connected in parallel with the diode D9, and one end of the power tube T9 is connected to the sixth connection point, and the other end is connected to the eighth connection point through the resistor R5; the power tube T10 is connected in parallel with the diode D10, and one end of the power tube T10 is connected to the seventh connection point, and the other end is connected to the ninth connection point through the resistor R6.

[0012] Optionally, the third flying capacitor control circuit includes a resistor R7 and a resistor R8, one end of the resistor R7 is connected to the sixth connection point, and the other end is connected to the eighth connection point; one end of the resistor R8 is connected to the seventh connection point, and the other end is connected to the ninth connection point.

[0013] In a second aspect, the present application provides a control method for the above-mentioned two-stage three-level high-voltage battery charging and discharging device, the method comprising: The DC bus capacitor is charged through the ACDC circuit until the DC output voltage reaches the target value; The flying capacitor is charged by the flying capacitor control circuit, and the flying capacitor voltage is controlled to rise to a target value. After completion, the flying capacitor control circuit enters a waiting state; The LC filter circuit voltage is adjusted by the DCDC circuit power tube so that the LC filter circuit voltage reaches a value close to the high-voltage battery voltage; When the main switch on the DC side is closed, the DCDC circuit and the high-voltage battery form a closed loop and enter normal operation.

[0014] Optionally, the method further comprises: When the absolute value of the difference between the actual voltage of the flying capacitor and the rated voltage exceeds a set limit, the flying capacitor control circuit enters the operating state from the waiting operating state to adjust the voltage of the flying capacitor; or, When the operating current of the two-stage three-level high-voltage battery charging and discharging device is less than a preset current value, the flying capacitor control circuit enters the operating state from the waiting operating state and adjusts the voltage of the flying capacitor.

[0015] The present application provides a two-stage three-level high-voltage battery charging and discharging device and control method, which converts alternating current into direct current through an ACDC circuit, and realizes efficient regulation of the DC voltage in combination with a DCDC circuit. The flying capacitor control circuit is adopted in the DCDC circuit, which can effectively improve the accuracy of voltage control and improve the stability of the device. The device has a reasonable structure, can achieve the advantages of small size, low cost and reliable operation, and meet the requirements of high power density and performance of high-voltage battery charging and discharging test equipment.

[0016] Furthermore, the present application not only improves the voltage balancing capability of the flying capacitor, but also significantly enhances the operating efficiency and reliability of the device in high current and high voltage scenarios by adding multiple sets of flying capacitor control circuits to the DCDC circuit and optimizing the connection layout of the power tube and capacitor. The technical solution of the present application optimizes the voltage control accuracy of the flying capacitor by adding a small number of low current power tubes and resistors, significantly reduces the cost of the device without adding isolation transformers and high-frequency high-power devices, while maintaining the simplicity of the device structure and the reliability of operation. In addition, the design optimizes the power distribution and current sharing characteristics of the device, reduces the stress of the power device, avoids the problem of overheating or uneven current of the power tube, and provides a more stable and efficient solution for high-voltage battery testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A circuit diagram of a two-stage three-level high-voltage battery charging and discharging device according to an embodiment of the present application is shown; Figure 2 The following is a diagram showing an ACDC ANPC three-level circuit according to an embodiment of the present application; Figure 3 A circuit diagram of a two-stage three-level high-voltage battery charging and discharging device according to another embodiment of the present application is shown; Figure 4 A circuit diagram of a first flying capacitor control circuit according to an embodiment of the present application is shown; Figure 5 A circuit diagram of a second flying capacitor control circuit according to an embodiment of the present application is shown; Figure 6 A circuit diagram of a third flying capacitor control circuit according to an embodiment of the present application is shown; Figure 7 A schematic flow chart of a control method for a two-stage three-level high-voltage battery charging and discharging device according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0018] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. It is to be understood that the specific embodiments described herein are only used to explain the present application, rather than to limit the present application. It should also be noted that, for ease of description, only some structures related to the present application are shown in the accompanying drawings, rather than all structures. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0019] The terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products or devices.

[0020] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0021] Figure 1 FIG. 1 shows a circuit diagram of a two-stage three-level high-voltage battery charging and discharging device according to an embodiment of the present application. Figure 1 As shown, the flying capacitor control circuit includes: ACDC circuit, connected to the power grid, is used to convert alternating current into direct current.

[0022] The ACDC circuit is connected to the power grid and is responsible for converting alternating current (AC) into direct current (DC), providing a stable DC voltage for the subsequent DCDC circuit. The ACDC circuit usually adopts a three-level topology, which can effectively reduce switching losses and improve efficiency and power density. The ACDC circuit achieves seamless connection with the power grid, meets high-voltage requirements, provides a stable DC bus voltage, and lays the foundation for the operation of the DCDC circuit and the flying capacitor control circuit.

[0023] A DCDC circuit comprises a first capacitor, a second capacitor, a third capacitor, a first flying capacitor control circuit, a first connection point, a second connection point, a third connection point, a fourth connection point and a fifth connection point; the positive electrode of the first capacitor is connected to the first flying capacitor control circuit through the first connection point, and the negative electrode of the first capacitor is connected to the positive electrode of the second capacitor; the negative electrode of the second capacitor is connected to the first flying capacitor control circuit through the third connection point; the positive electrode of the third capacitor is connected to the first flying capacitor control circuit through the fourth connection point, and the negative electrode of the third capacitor is connected to the first flying capacitor control circuit through the fifth connection point; and the first flying capacitor control circuit is connected to the ACDC circuit through the second connection point.

[0024] The first capacitor C1 and the second capacitor C2 are connected in series, and connected in parallel with the third capacitor C3. Through series voltage division and parallel filtering, a stable voltage platform is provided under high voltage conditions to support voltage conversion of three-level topology. The third capacitor C3 is a flying capacitor. In order to maintain the stability of the device circuit voltage, the present application adjusts and maintains the voltage of the flying capacitor C3 at the rated value through the first flying capacitor control circuit, so that the entire system remains stable during operation, and the voltage distribution of the power tube is optimized at the same time. The technical solution of the present application reduces the voltage stress of a single power device by managing high voltage in sections, so that power devices of low voltage levels can be used to reduce costs. The stability and efficiency of the DCDC circuit are improved through precise control of the flying capacitor C3, ensuring reliability in high-voltage charging and discharging scenarios.

[0025] The LC filter circuit is connected to the DCDC circuit.

[0026] The LC filter circuit is composed of an inductor and a capacitor, which filters out the high-frequency ripple during the switching process of the DCDC circuit, provides a smooth DC voltage, and adjusts the current waveform to reduce current spikes. The LC filter circuit provides a stable DC voltage with small ripples, protecting the high-voltage battery from excessive high-frequency interference. It improves the system's voltage accuracy and current output stability, meeting the strict requirements of high-voltage battery charge and discharge testing.

[0027] The two-stage three-level high-voltage battery charging and discharging device of the present application realizes bidirectional energy flow during the high-voltage battery charging and discharging process: during charging, the AC power grid rectifies the AC power into DC power through the ACDC module, and transmits it to the DC capacitor side of the DCDC circuit, and then adjusts it to a voltage suitable for the high-voltage battery through the DCDC converter, and completes the charging of the battery through the LC filter circuit and the DC main switch. During discharge, the energy flows in the opposite direction, and after the high-voltage battery is adjusted to DC power through the DCDC converter, it is inverted into AC power through the ACDC module and transmitted back to the power grid, realizing efficient energy feedback.

[0028] According to the above embodiment, the ACDC circuit is used to convert the AC power into the DC power, and the DCDC circuit is combined to realize the efficient regulation of the DC voltage. The flying capacitor control circuit is adopted in the DCDC circuit, which can effectively improve the accuracy of the voltage control and improve the stability of the device. The device has a reasonable structure, can achieve the advantages of small size, low cost and reliable operation, and meet the requirements of high power density and performance of high-voltage battery charging and discharging test equipment.

[0029] Figure 2 FIG. 2 shows a three-level ACDC ANPC circuit diagram according to an embodiment of the present application. Figure 2 As shown, the above ACDC circuit adopts the ANPC three-level topology to complete AC / DC power conversion. The three-level topology has the advantages of high power density, low cost, excellent performance and high reliability. The AC input end of the device is connected to the AC grid through the main switch, AC pre-charging circuit and LC filter network. After filtering, the input voltage is connected to the ANPC three-level circuit composed of IGBT or MOSFET power tube and power diode for current conversion. The ANPC three-level topology realizes efficient conversion of AC to DC, and is connected to the DC bus capacitor in the subsequent topology through the DC side output. The design realizes the bidirectional flow of energy between the AC grid and the DC side capacitor, meeting the requirements of efficient energy transmission in high-voltage and high-power scenarios.

[0030] In some embodiments, the DCDC circuit also includes a power tube T5, a power tube T6, a power tube T7, a power tube T8, a diode D5, a diode D6, a diode D7 and a diode D8, and the power tube T5 is connected in series with the power tube T6, the power tube T7 and the power tube T8 in sequence; the power tube T5 is connected in parallel with the diode D5, and one end of the power tube T5 is connected to the positive electrode of the third capacitor C3, and the other end is connected to the positive electrode of the first capacitor C1; the power tube T8 is connected in parallel with the diode D8, and one end of the power tube T8 is connected to the negative electrode of the third capacitor C3, and the other end is connected to the negative electrode of the second capacitor C2.

[0031] The power tube T5 is connected in series with the power tube T6, the power tube T7, and the power tube T8. By controlling the on and off of these power tubes, the DCDC circuit can achieve voltage regulation and energy transfer in different switching states. The diode D5 is connected in parallel with the power tube T5, the diode D6 is connected in parallel with the power tube T6, the diode D7 is connected in parallel with the power tube T7, and the diode D8 is connected in parallel with the power tube T8. These diodes provide a freewheeling path. When the power tube is turned off, the diode is turned on to prevent energy from being interrupted instantly and maintain the continuity of the current. The power tube T5 is connected to the positive electrode of the third capacitor C3 and the positive electrode of the first capacitor C1, and the power tube T8 is connected to the negative electrode of the third capacitor C3 and the negative electrode of the second capacitor C2. This connection can control the voltage distribution and energy flow by adjusting the on and off of the power tube, and realize the voltage balance of the flying capacitor and the precise adjustment of the output voltage. In the DCDC conversion process, the on and off of the power tubes T5 and T8 not only adjust the flow direction of the main current, but also provide energy storage and buffering through the capacitor, optimizing the dynamic response of the circuit. This three-level topology reduces the voltage stress of the power tube and reduces the switching loss, thereby improving the circuit efficiency and reliability. By connecting the power tube T5 and the power tube T8 to multiple capacitors, the circuit can realize the voltage control of the flying capacitor, balance the DC side voltage, and reduce the impact of capacitor voltage fluctuations on system performance. Through the above connection, the control logic of the power tube can relatively simply realize the precise adjustment of the output voltage and the smooth transmission of energy, thereby improving the stability of the circuit control.

[0032] Figure 3 A circuit diagram of a two-stage three-level high-voltage battery charging and discharging device according to another embodiment of the present application is shown.

[0033] In some embodiments, when the power demand of the two-stage three-level high-voltage battery charging and discharging device is large, a DCDC multi-bridge arm staggered parallel structure is adopted. The DCDC part is composed of multiple independent flying capacitor three-level circuits, and each circuit unit realizes the power conversion function through its independent bridge arm. The output end of each flying capacitor three-level circuit is connected together in a staggered parallel manner to form a unified output. This staggered connection design can effectively divide the power load of each circuit and reduce the pressure on a single circuit. Figure 3 As shown, the two-stage three-level high-voltage battery charging and discharging device also includes: The second flying capacitor control circuit is connected between the power tube T5 and the power tube T6 through the sixth connection point.

[0034] The second flying capacitor control circuit is connected between the power tube T5 and the power tube T6 through the sixth connection point, and its main function is to control the voltage balance of the flying capacitor. By adjusting the charge and discharge state of the flying capacitor, it is ensured that the voltage between the power tube T5 and the power tube T6 is always balanced, thereby reducing the voltage stress of the switching device and improving the stability of the circuit. By setting the second flying capacitor control circuit, the voltage of T5 and the power tube T6 is effectively balanced during the voltage division process, extending the service life of the power tube. At the same time, by staggering the second flying capacitor control circuit and the first flying capacitor control circuit in parallel, the voltage of the flying capacitor can be accurately controlled, which helps to improve the dynamic response performance of the system.

[0035] In some embodiments, the circuit connected in parallel with the first flying capacitor control circuit in the two-stage three-level high-voltage battery charging and discharging device may also be a third flying capacitor control circuit. Figure 3 The third flying capacitor control circuit is connected between the power tube T7 and the power tube T8 through the seventh connection point.

[0036] Similar to the second flying capacitor control circuit, the third flying capacitor control circuit is connected between the power tube T7 and the power tube T8 through the seventh connection point, and is responsible for voltage regulation and balancing of the flying capacitor to ensure that the power tube T7 and the power tube T8 maintain uniform voltage distribution under different working conditions.

[0037] refer to Figure 3 The DCDC circuit also includes a fourth capacitor C4, a power tube T9, a power tube T10, a power tube T11 and a power tube T12, wherein the power tube T9 is connected in series with the power tube T10, the power tube T11 and the power tube T12 in sequence; the positive electrode of the fourth capacitor C4 is connected to the second flying control circuit or the third flying control circuit through the eighth connection point, and the negative electrode of the fourth capacitor C4 is connected to the second flying control circuit or the third flying control circuit through the ninth connection point; the positive electrode of the fourth capacitor C4 is also connected between the power tube T9 and the power tube T10, and the negative electrode of the fourth capacitor C4 is also connected between the power tube T11 and the power tube T12.

[0038] The power tubes T9 to T12 are connected in series in sequence to form a basic three-level topology structure for efficiently converting current. Through the series connection, each power tube only bears part of the total voltage, thereby reducing the voltage stress of a single switch device and improving its reliability and service life. The fourth capacitor C4 is connected to the eighth connection point between the power tube T9 and the power tube T10 and the ninth connection point between the power tube T11 and the power tube T12, and plays the role of energy storage, voltage division and voltage balance. At the same time, the fourth capacitor C4 dynamically adjusts the voltage across the fourth capacitor C4 through the connection with the second flying control circuit or the third flying control circuit to ensure the normal operation of the circuit and the stability of the output voltage. Through the three-level topology structure and the flying capacitor voltage division, the voltage stress borne by the power tube T9 to the power tube T12 is only a part of the total voltage, which reduces the withstand voltage requirements for the power tube and improves the flexibility of device selection. The fourth capacitor C4 dynamically adjusts the voltage through the connection with the flying control circuit, avoids voltage deviation or imbalance, and enhances the overall stability of the system.

[0039] In the above embodiment, when the power demand of the two-stage three-level high-voltage battery charging and discharging device is large, a DCDC multi-bridge arm staggered parallel structure is adopted. By connecting multiple flying capacitor three-level circuits in a staggered parallel manner, the power load can be evenly distributed to each circuit unit. The power burden borne by each circuit unit is effectively reduced, avoiding the overload of a single circuit unit, thereby improving the overall stability of the system. In a high-power scenario, the load of a single circuit may cause overheating, overload or performance degradation of the power device. By staggering multiple circuits in parallel, the pressure of each circuit is relieved, the reliability of the system is effectively improved, and the problem of local overload is avoided. The staggered parallel design not only balances the power output between each circuit, but also optimizes the efficiency loss in the power conversion process. Multiple circuits running in parallel can reduce the switching loss and transmission loss of the circuit and improve the energy efficiency of the overall system. At the same time, multiple circuits in parallel means that the system has better redundancy. If a circuit fails or works unstable, other circuits can continue to provide power, thereby ensuring the continuous operation of the system and improving fault tolerance. The power load shared by each circuit unit is small, so the heat output of each circuit will be relatively low. This reduces the temperature rise of a single circuit unit, helps improve thermal management of the entire system, and reduces the risk of device failure due to excessive temperature rise.

[0040] Figure 4 FIG. 2 shows a circuit diagram of a first flying capacitor control circuit according to an embodiment of the present application. Figure 4 As shown, the first flying capacitor control circuit includes: Power tube T1, power tube T2, power tube T3, power tube T4, diode D1, diode D2, diode D3 and diode D4; power tube T1 is connected in parallel with diode D1, and one end of power tube T1 is connected to the first connection point, and the other end is connected to the fourth connection point through resistor R1; power tube T2 is connected in parallel with diode D2, and one end of power tube T2 is connected to the second connection point, and the other end is connected to the fourth connection point through resistor R2; power tube T3 is connected in parallel with diode D3, and one end of power tube T3 is connected to the second connection point, and the other end is connected to the fifth connection point through resistor R3; power tube T4 is connected in parallel with diode D4, and one end of power tube T4 is connected to the third connection point, and the other end is connected to the fifth connection point through resistor R4.

[0041] Power tube T1 is connected in parallel with diode D1, power tube T2 is connected in parallel with diode D2, power tube T3 is connected in parallel with diode D3, and power tube T4 is connected in parallel with diode D4. Each pair of power tubes and diodes works together to ensure that current can flow in different circuit states. When the current needs to flow in a specific direction, the power tube will be turned on, and when the current flows in the reverse direction, the diode will play a conductive role to prevent the reverse current from damaging the circuit. This control method helps to optimize the charging and discharging process of the flying capacitor.

[0042] One end of the power tube T1 is connected to the first connection point, and the other end is connected to the fourth connection point through the resistor R1. Figure 4 , the first connection point is connected to the positive terminal of the first capacitor C1, and the fourth connection point is connected to the positive terminal of the third capacitor C3, that is, one end of the power tube T1 is connected to the positive electrode of the first capacitor C1, and the other end is connected to the third capacitor C3, and is also connected between the power tube T5 and the power tube T6. Similarly, one end of the power tube T4 is connected to the negative electrode of the second capacitor C2, and the other end is connected to the negative electrode of the third capacitor C3, and is also connected between the power tube T7 and the power tube T8. When the circuit needs to transmit electric energy from the first capacitor C1 to the third capacitor C3, the power tube T5 provides a low impedance path by being turned on. The current flows to the third capacitor C3 through the power tube T5, which can effectively regulate the flow of voltage and current and ensure the voltage stability of the flying capacitor. Similarly, when it is necessary to charge the second capacitor C2, the power tube T8 is turned on, and the current flows to the second capacitor C2 through the power tube T8, thereby realizing the smooth transmission of electric energy.

[0043] Through the precise control of the power tube and the diode, the voltage of the flying capacitor can be ensured to operate within a stable range, effectively avoiding the impact of voltage fluctuations on the battery charging and discharging process, and improving the reliability of the battery charging and discharging device. The control circuit can optimize the current flow path, reduce unnecessary power loss, and improve the energy efficiency of the overall system. In addition, the configuration of the power tube and diode in parallel makes the current control more flexible and efficient.

[0044] In some embodiments, when the power tube T5 is turned on, the power tube T8 is turned off; when the power tube T8 is turned on, the power tube T5 is turned off.

[0045] In this embodiment, the conduction of the power tube T5 and the power tube T8 is alternate, which means that when one is turned on, the other remains off. This alternating conduction is to ensure that the current flow between different capacitors in the circuit does not interfere with each other, and when energy flows from the endpoints of different capacitors to the battery or load, efficient power transmission and voltage control can be achieved. For example, when the power tube T5 is turned on, it will provide current through the circuit path to which it is connected, so that energy is transferred from one capacitor (such as the first capacitor C1 or the third capacitor C3) to another capacitor. When the power tube T8 is turned on, different current transmission tasks will be performed, which may involve voltage adjustment with different capacitors to prevent current and voltage from interfering with each other. The power tube T5 and the power tube T8 control different capacitors, and their conduction times are mutually exclusive to ensure that no current conflict or short circuit will occur in the circuit. For example, if the power tube T5 and the power tube T8 are turned on at the same time, it may cause the current to flow in opposite paths, resulting in unstable or invalid current transmission, affecting the efficiency and stability of the entire circuit. By ensuring that the power tube T5 and the power tube T8 are turned on alternately, the current flow direction is always orderly, and conflicting conduction operations are avoided.

[0046] When the power tube T5 is turned on, the power tubes T1 and T3 are turned on; when the power tube T8 is turned on, the power tubes T2 and T4 are turned on; the turn-on time of the power tubes T1 and T3 is the same as that of the power tubes T2 and T4.

[0047] When the power tube T5 is turned on, it is responsible for connecting the positive electrode of the first capacitor C1 and the positive electrode of the third capacitor C3, so that the energy of the first capacitor C1 can flow to the third capacitor C3, or transfer the electric energy to the third capacitor C3 when charging. When the power tube T5 is turned on, the power tube T1 and the power tube T3 are turned on at the same time, thereby providing a continuous current path for the entire circuit. The power tube T1 and the power tube T3 are connected to different ends of the first capacitor C1 and the third capacitor C3 respectively, ensuring that the current is stably transmitted between the two capacitors. When the power tube T5 is turned on, the power tube T1 and the power tube T3 are turned on together to form a complete current loop, so that energy can flow from the first capacitor C1 to the third capacitor C3. The time when the power tube T1 and the power tube T3 are turned on is set to be synchronized, which means that the control of the two power tubes is matched with each other, ensuring that the flow direction of the current and the voltage are stable, and avoiding current reversal or voltage overshoot. Through the coordinated conduction of the power tube T5, the power tube T1 and the power tube T3, it can be ensured that the electric energy transmission from the first capacitor C1 to the third capacitor C3 is smooth and smooth. This process reduces energy loss and improves energy conversion efficiency. Similarly, when the power tube T8 is turned on, it cooperates with the power tube T2 and the power tube T4 to form a loop, so that current can flow between the second capacitor C2 and the third capacitor C3, and the overall voltage of the control circuit is stable.

[0048] At the same time, the conduction time of power tubes T1, T3 is consistent with that of power tubes T2 and T4, that is, when the current flows through two different circuit paths, the current distribution is balanced. By making the conduction time of these power tubes the same, it can be ensured that the current load passing through them is relatively consistent, thereby avoiding excessive current in a certain path causing circuit instability or damage. This synchronous control ensures that each part of the circuit can evenly bear its corresponding load, prevents overload of any path, and improves the operating efficiency and safety of the entire circuit. If the conduction time of power tubes T1, T3 is inconsistent with that of power tubes T2 and T4, it may cause uneven voltage of the capacitor, affecting the stability and efficiency of the entire system, and may even cause overvoltage or damage to the capacitor.

[0049] Figure 5 FIG. 2 shows a circuit diagram of a second flying capacitor control circuit according to an embodiment of the present application. Figure 5 As shown, the second flying capacitor control circuit includes: Power tube T9, power tube T10, diode D9, diode D10, resistor R5 and resistor R6; the power tube T9 is connected in parallel with the diode D9, and one end of the power tube T9 is connected to the sixth connection point, and the other end is connected to the eighth connection point through the resistor R5; the power tube T10 is connected in parallel with the diode D10, and one end of the power tube T10 is connected to the seventh connection point, and the other end is connected to the ninth connection point through the resistor R6.

[0050] The function of the power tube T9 is to control the flow of current and to achieve reverse current protection by working in parallel with the diode D9. When the power tube T9 is turned on, the current flows from the sixth connection point to the eighth connection point. If the current direction is reversed, the diode D9 will be turned on to ensure that the current can flow normally without damaging other components. Similar to the power tube T9, the parallel design of the power tube T10 and the diode D10 is used to ensure the direction of current flow control and provide protection. When the power tube T10 is turned on, the current flows from the seventh connection point to the ninth connection point, and the reverse current is turned on through the diode D10. Resistors R5 and R6 are connected in series with the power tube T9 and the power tube T10 respectively. Their function is to limit the current size and prevent excessive current from causing damage to the power tube or other parts of the circuit. They can also help stabilize the current flow of the circuit, ensure that the current flows smoothly within the control area, and prevent overcurrent from affecting the control circuit.

[0051] The design of the control circuit allows the flying capacitor voltage to be effectively controlled to ensure that the voltage is not too large, thereby improving the stability of the capacitor. Through the cooperation of power tubes T9 and T10 with the diode, the voltage across the capacitor can be effectively adjusted to ensure that the circuit always remains within a safe voltage range during operation.

[0052] Figure 6 FIG. 4 shows a circuit diagram of a third flying capacitor control circuit according to an embodiment of the present application. Figure 6 As shown, the third flying capacitor control circuit includes: Resistor R7 and resistor R8, one end of resistor R7 is connected to the sixth connection point, and the other end is connected to the eighth connection point; one end of resistor R8 is connected to the seventh connection point, and the other end is connected to the ninth connection point.

[0053] The third flying capacitor control circuit includes a resistor R7 and a resistor R8, which are connected to the sixth and seventh connection points and the eighth and ninth connection points, respectively. The function of these resistors is to balance and adjust the current distribution in the circuit and ensure that the voltage of the flying capacitor is effectively controlled and stabilized. Resistors R7 and R8 prevent the circuit from being damaged by excessive current by limiting the flow of current, and provide appropriate current feedback for the flying capacitor, which helps to control the accuracy and stability of the capacitor voltage.

[0054] Combined with the connection mode of the first flying capacitor control circuit, resistors R7 and R8 help coordinate the working states between multiple circuit units, ensuring that the voltage of each flying capacitor reaches the target value evenly and accurately, thereby improving the reliability and stability of the entire system. By reasonably configuring the resistance value of the resistor, the current distribution can be optimized under different voltage and load conditions, and the performance and efficiency of the circuit can be improved.

[0055] In the above embodiment, when the novel staggered parallel two-stage three-level high-voltage battery charging and discharging device is started, the flying capacitor control circuits A, B (or C) operate simultaneously until all flying capacitors reach the target value, and then the corresponding control circuits are turned off to enter the operation stage. During the operation, when the difference between the voltage of any flying capacitor and the rated voltage exceeds the set limit, or the operating current is lower than the set value, all flying capacitor control circuits will restart to adjust the capacitor voltage to ensure stable operation of the system.

[0056] According to the above embodiments, the present application not only improves the voltage balancing capability of the flying capacitor, but also significantly enhances the operating efficiency and reliability of the device in high current and high voltage scenarios by adding multiple flying capacitor control circuits to the DCDC circuit and optimizing the connection layout of the power tube and the capacitor. The technical solution of the present application optimizes the voltage control accuracy of the flying capacitor by adding a small number of low current power tubes and resistors, significantly reduces the cost of the device without adding isolation transformers and high-frequency high-power devices, while maintaining the simplicity of the device structure and the reliability of operation. In addition, the design optimizes the power distribution and current sharing characteristics of the device, reduces the stress of the power device, avoids the problem of overheating or uneven current of the power tube, and provides a more stable and efficient solution for high-voltage battery testing.

[0057] Figure 7 FIG. 1 is a flow chart showing a control method of a two-stage three-level high-voltage battery charging and discharging device according to an embodiment of the present application. Figure 7 As shown, the present application also provides a control method for the above-mentioned two-stage three-level high-voltage battery charging and discharging device, the method comprising the following steps: Step S100, charging the DC bus capacitor through the ACDC circuit until the DC output side voltage reaches a target value.

[0058] In this step, the ACDC circuit converts AC power into DC power and charges the DC bus capacitor, gradually increasing the voltage to the predetermined target value. This process is the key to system startup, ensuring that the DC bus capacitor has sufficient voltage support, laying a solid foundation for the stable operation of subsequent circuits. By precisely controlling the voltage increase, the system can smoothly transition to the flying capacitor charging stage in the subsequent steps, ensuring efficient and stable battery charging and discharging process.

[0059] Step S200, charging the flying capacitor through the flying capacitor control circuit, controlling the flying capacitor voltage to rise to a target value, and after completion, the flying capacitor control circuit enters a waiting state.

[0060] In step S200, the flying capacitor control circuit accurately adjusts the charging process of the flying capacitor to ensure that its voltage gradually rises to the target value. This process strictly controls the flying capacitor voltage to avoid the risk of overvoltage or undervoltage, thereby improving the stability and safety of the system. After charging is completed, the flying capacitor control circuit enters the waiting state, ready to dynamically adjust the capacitor voltage when needed, creating necessary conditions for the smooth operation of the DCDC circuit and ensuring the reliability of the entire system.

[0061] Step S300, adjusting the LC filter circuit voltage through the DCDC circuit power tube so that the LC filter circuit voltage reaches a value close to the high-voltage battery voltage.

[0062] In step S300, the DCDC circuit accurately controls the output voltage of the LC filter circuit by adjusting the working state of the power tube to match the voltage of the high-voltage battery. In this process, the role of the DCDC circuit is to ensure that the output voltage is stable and suitable for the battery charging or discharging requirements. Through precise adjustment, the battery is prevented from being overcharged or over-discharged, while ensuring the charging efficiency, thereby improving the battery life and the overall performance of the system. This step lays the foundation for safe battery charging.

[0063] Step S400, closing the DC side main switch, the DCDC circuit and the high-voltage battery form a closed loop, and enter a normal operating state.

[0064] Finally, the main switch on the DC side is closed, and the DCDC circuit forms a closed-loop control with the high-voltage battery, entering the normal charging and discharging state. At this point, the voltage and current control between the battery and the circuit begins to be precisely coordinated to ensure that the battery is charged or discharged under optimal conditions, and the entire system enters a stable and efficient working state. Through closed-loop control, the system can adjust the voltage and current in real time to cope with load changes, achieve the best effect of battery charging and discharging, and maximize the operating efficiency and reliability of the system.

[0065] In some embodiments, when the absolute value of the difference between the actual voltage of the flying capacitor and the rated voltage exceeds a set limit, the flying capacitor control circuit enters the operating state from the waiting state to adjust the voltage of the flying capacitor.

[0066] The voltage deviation of the flying capacitor will affect the overall stability and performance of the system. If the voltage is too high or too low, it may cause overvoltage or overcurrent of the power tube, which will affect the efficiency of the charging and discharging device, and may even cause failure or damage. Therefore, it is necessary to adjust the flying capacitor voltage in time to keep the system running in a safe and efficient working state.

[0067] Alternatively, when the operating current of the two-stage three-level high-voltage battery charging and discharging device is less than a preset current value, the flying capacitor control circuit enters the operating state from the waiting operating state and adjusts the voltage of the flying capacitor.

[0068] When the operating current of the two-stage three-level high-voltage battery charging and discharging device is less than the preset current value, the flying capacitor control circuit will also enter the operating state from the waiting state to adjust the voltage. This situation usually occurs when the load changes greatly or during the battery charging and discharging process. The current drop may indicate a reduction in system load or other problems. At this time, the voltage of the flying capacitor may need to be adjusted to optimize the system operation. Through the voltage adjustment at this time, the battery charging and discharging process can be ensured to be stable, avoiding problems caused by current fluctuations or voltage instability in the system, and improving the reliability and safety of the overall device.

[0069] By dynamically adjusting the voltage of the flying capacitor, the system can be ensured to remain stable under various operating conditions to avoid equipment damage or efficiency loss due to voltage fluctuations. Real-time monitoring and adjustment of the flying capacitor voltage can effectively prevent system failures caused by voltage deviation or low current conditions and improve the reliability of the device.

[0070] In the control method of the flying capacitor control circuit, the specific implementation methods in different situations refer to the relevant contents of the embodiment of the circuit, which will not be described in detail here.

[0071] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0072] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A two-stage three-level high-voltage battery charging and discharging device, characterized in that: The device comprises: ACDC circuit, connected to the power grid, for converting AC power into DC power; A DCDC circuit, comprising a first capacitor, a second capacitor, a third capacitor and a first flying capacitor control circuit; the positive electrode of the first capacitor is connected to the first flying capacitor control circuit through a first connection point, and the negative electrode of the first capacitor is connected to the positive electrode of the second capacitor; the negative electrode of the second capacitor is connected to the first flying capacitor control circuit through a third connection point; the positive electrode of the third capacitor is connected to the first flying capacitor control circuit through a fourth connection point, and the negative electrode of the third capacitor is connected to the first flying capacitor control circuit through a fifth connection point; the first flying capacitor control circuit is connected to the ACDC circuit through a second connection point; The LC filter circuit is connected to the DCDC circuit.

2. The two-stage three-level high-voltage battery charging and discharging device according to claim 1, characterized in that: The DCDC circuit also includes a power tube T5, a power tube T6, a power tube T7, a power tube T8, a diode D5, a diode D6, a diode D7 and a diode D8, wherein the power tube T5 is connected in series with the power tube T6, the power tube T7 and the power tube T8 in sequence; the power tube T5 is connected in parallel with the diode D5, and one end of the power tube T5 is connected to the positive electrode of the third capacitor, and the other end is connected to the positive electrode of the first capacitor; the power tube T8 is connected in parallel with the diode D8, and one end of the power tube T8 is connected to the negative electrode of the third capacitor, and the other end is connected to the negative electrode of the second capacitor.

3. The two-stage three-level high-voltage battery charging and discharging device according to claim 2, characterized in that: The DCDC circuit further includes: A second flying capacitor control circuit is connected between the power tube T5 and the power tube T6 through a sixth connection point; or, The third flying capacitor control circuit is connected between the power tube T7 and the power tube T8 through a seventh connection point.

4. The two-stage three-level high-voltage battery charging and discharging device according to claim 3, characterized in that: The DCDC circuit also includes a fourth capacitor, a power tube T9, a power tube T10, a power tube T11 and a power tube T12, wherein the power tube T9 is connected in series with the power tube T10, the power tube T11 and the power tube T12 in sequence; the positive electrode of the fourth capacitor is connected to the second flying control circuit or the third flying control circuit through an eighth connection point, and the negative electrode of the fourth capacitor is connected to the second flying control circuit or the third flying control circuit through a ninth connection point; the positive electrode of the fourth capacitor is also connected between the power tube T9 and the power tube T10, and the negative electrode of the fourth capacitor is also connected between the power tube T11 and the power tube T12.

5. The two-stage three-level high-voltage battery charging and discharging device according to claim 1, characterized in that: The first flying capacitor control circuit includes a power tube T1, a power tube T2, a power tube T3, a power tube T4, a diode D1, a diode D2, a diode D3 and a diode D4; the power tube T1 is connected in parallel with the diode D1, and one end of the power tube T1 is connected to the first connection point, and the other end is connected to the fourth connection point through a resistor R1; the power tube T2 is connected in parallel with the diode D2, and one end of the power tube T2 is connected to the second connection point, and the other end is connected to the fourth connection point through a resistor R2; the power tube T3 is connected in parallel with the diode D3, and one end of the power tube T3 is connected to the second connection point, and the other end is connected to the fifth connection point through a resistor R3; the power tube T4 is connected in parallel with the diode D4, and one end of the power tube T4 is connected to the third connection point, and the other end is connected to the fifth connection point through a resistor R4.

6. The two-stage three-level high-voltage battery charging and discharging device according to claim 5, characterized in that: When the power tube T5 is turned on, the power tube T8 is not turned on; when the power tube T8 is turned on, the power tube T5 is not turned on; When the power tube T5 is turned on, the power tube T1 and the power tube T3 are turned on; When the power tube T8 is turned on, the power tube T2 and the power tube T4 are turned on; the turn-on time of the power tube T1 and the power tube T3 is the same as that of the power tube T2 and the power tube T4.

7. The two-stage three-level high-voltage battery charging and discharging device according to claim 4, characterized in that: The second flying capacitor control circuit includes a power tube T9, a power tube T10, a diode D9, a diode D10, a resistor R5 and a resistor R6; the power tube T9 is connected in parallel with the diode D9, and one end of the power tube T9 is connected to the sixth connection point, and the other end is connected to the eighth connection point through the resistor R5; the power tube T10 is connected in parallel with the diode D10, and one end of the power tube T10 is connected to the seventh connection point, and the other end is connected to the ninth connection point through the resistor R6.

8. The two-stage three-level high-voltage battery charging and discharging device according to claim 4, characterized in that: The third flying capacitor control circuit includes a resistor R7 and a resistor R8, one end of the resistor R7 is connected to the sixth connection point, and the other end is connected to the eighth connection point; one end of the resistor R8 is connected to the seventh connection point, and the other end is connected to the ninth connection point.

9. A control method for a two-stage three-level high-voltage battery charging and discharging device as claimed in any one of claims 1 to 8, characterized in that: The method comprises: The DC bus capacitor is charged through the ACDC circuit until the DC output voltage reaches the target value; The flying capacitor is charged by the flying capacitor control circuit, and the flying capacitor voltage is controlled to rise to a target value. After completion, the flying capacitor control circuit enters a waiting state; The LC filter circuit voltage is adjusted by the DCDC circuit power tube so that the LC filter circuit voltage reaches a value close to the high-voltage battery voltage; When the main switch on the DC side is closed, the DCDC circuit and the high-voltage battery form a closed loop and enter normal operation.

10. The control method according to claim 9, characterized in that: The method further comprises: When the absolute value of the difference between the actual voltage of the flying capacitor and the rated voltage exceeds a set limit, the flying capacitor control circuit enters the operating state from the waiting operating state to adjust the voltage of the flying capacitor; or, When the operating current of the two-stage three-level high-voltage battery charging and discharging device is less than a preset current value, the flying capacitor control circuit enters the operating state from the waiting operating state and adjusts the voltage of the flying capacitor.

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