DCDC bidirectional charging and discharging device and control method thereof

Abstract

The invention discloses a DCDC bidirectional charging and discharging device and a control method thereof.The DCDC bidirectional charging and discharging device comprises a first bidirectional inversion module, a transformer, a second bidirectional inversion module, a first current detection module, a second current detection module and a control module, and the control module collects output end current through the second current detection module; and when the absolute value of the output end current is greater than a preset current value, the input end current is calculated according to a preset transformer turn ratio, and when the absolute value of the output end current is not greater than the preset current value, the first current detection module is started, and the input end current is detected through the first current detection module. According to the technical scheme, when the current of the output end is small, the first current detection module is directly started to detect the current of the input end, and the error caused by indirectly calculating the current through the turn ratio in a traditional scheme is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage inverters, and in particular to a DCDC bidirectional charging and discharging device and a control method thereof. Background Art

[0002] With the rapid development of renewable energy systems, especially solar photovoltaic power generation systems, energy storage inverters, as key equipment connecting the power generation end with the power grid or load, are directly related to the efficiency and stability of the entire system. In energy storage systems, lithium batteries are widely used due to their high energy density, long life and good charge and discharge performance. However, in order to ensure the reliability and safety of lithium batteries, higher and higher requirements are placed on the measurement accuracy of current in practical applications.

[0003] Accurate current measurement is essential to prevent overcharging or over-discharging of batteries. Overcharging can cause internal heating of the battery, which can lead to battery damage or even safety hazards in severe cases, while over-discharging can have a negative impact on the battery life. Traditional solutions usually calculate the actual battery current indirectly through battery sensors (such as Hall sensors) on the high-voltage side. This solution uses the transformer ratio to infer the battery current, but due to the magnetic loss of the transformer and other external interference, it is often difficult to achieve accurate measurement when the current is low, thus affecting the measurement accuracy under low current conditions. This is difficult to provide sufficient accuracy for accurately controlling the charging and discharging process of lithium batteries, especially when the battery is close to full or low power. Summary of the invention

[0004] The embodiment of the present invention provides a DCDC bidirectional charging and discharging device and a control method thereof to solve the above technical problems.

[0005] A first aspect of an embodiment of the present invention provides a DCDC bidirectional charging and discharging circuit, comprising: A first bidirectional inverter module performs bidirectional conversion between DC voltage and AC voltage; A transformer, comprising a primary coil and a secondary coil, wherein the primary coil is connected to the first bidirectional inverter module; A second bidirectional inverter module, connected to the secondary coil, to perform bidirectional conversion between AC voltage and DC voltage; A first current detection module, connected between the DC input terminal and the first bidirectional inverter module, for detecting the input terminal current; A second current detection module, connected between the second bidirectional inverter module and the DC output terminal, for detecting the output terminal current; A control module, which is respectively connected to the first current detection module and the second current detection module, and is used to collect the output end current through the second current detection module, and when the absolute value of the output end current is greater than the preset current value, calculate the input end current according to the turns ratio of the preset transformer, and when the absolute value of the output end current is not greater than the preset current value, start the first current detection module and detect the input end current through the first current detection module.

[0006] Optionally, the first current detection module includes a first switch module, a collection module and a differential amplifier module, wherein two ends of the first switch module and the collection module after being connected in parallel are respectively connected to the DC input end and the first bidirectional inverter module, two ends of the collection module are also respectively connected to two input ends of the differential amplifier module, and an output end of the differential amplifier module is connected to the control module; When the absolute value of the output current is greater than a preset current value, the control module controls the first switch module to be turned on; When the absolute value of the output current is not greater than the preset current value, the control module controls the first switch module to be turned on, the acquisition module acquires the input current, the differential amplifier module acquires the voltage difference signal on the acquisition module, and amplifies the voltage difference signal and outputs it to the control module.

[0007] Optionally, the second current detection module is a Hall sensor, and the Hall sensor is used to detect the output current.

[0008] Optionally, the DCDC bidirectional charge and discharge device also includes a first light-emitting diode, a second switch module, a first photodiode, a second light-emitting diode, a third switch module, a second photodiode and a divider. The first light-emitting diode and the second switch module are connected in parallel between the DC input end and the first current detection module. The second light-emitting diode and the third switch module are connected in parallel between the DC output end and the second current detection module. The first input end of the divider is connected to the first photodiode, the second input end of the divider is connected to the second photodiode, and the output end of the divider is connected to the control module. The control module is also connected to the first bidirectional inverter and the second bidirectional inverter respectively.

[0009] A second aspect of an embodiment of the present invention provides a control method for the DCDC bidirectional charge and discharge device according to the first aspect, the control method comprising: When the absolute value of the output terminal current is greater than a preset current value, calculating the input terminal current according to a preset transformer turns ratio; When the absolute value of the output-end current is not greater than a preset current value, the first current detection module is started, and the input-end current is detected according to the first current detection module.

[0010] Optionally, the first current detection module includes a first switch module, a collection module and a differential amplification module, and detecting the input end current according to the first current detection module includes: The first switch module is controlled to be turned on, the input end current is collected by the collection module to form a voltage difference, the voltage difference signal on the collection module is obtained by the differential amplification module, and the voltage difference signal is amplified.

[0011] Optionally, the step of detecting the input end current according to the first current detection module further includes: When it is determined that an error occurs in the transformer according to the detected input terminal current and the calculated input terminal current, compensation is performed by controlling the first bidirectional inverter module or the second bidirectional inverter module.

[0012] Optionally, when it is determined according to the detected input end current and the calculated input end current that the transformer fails, compensation is performed by controlling the first bidirectional inverter module or the second bidirectional inverter module, including: When the detected input current is higher than the calculated input terminal, it is determined that there is additional energy loss in the transformer resulting in reduced transmission efficiency, and the first bidirectional inverter module or the second bidirectional inverter module is controlled to increase the input current.

[0013] Optionally, the DCDC bidirectional charge and discharge device further includes a first light-emitting diode, a second switch module, a first photodiode, a second light-emitting diode, a third switch module, a second photodiode and a divider, wherein the first light-emitting diode and the second switch module are connected in parallel between the DC input end and the first current detection module, the second light-emitting diode and the third switch module are connected in parallel between the DC output end and the second current detection module, the first input end of the divider is connected to the first photodiode, the second input end of the divider is connected to the second photodiode, the output end of the divider is connected to the control module, and the control module is also connected to the first bidirectional inverter and the second bidirectional inverter respectively; The method further comprises: determining that a fault occurs according to the input terminal current obtained by detection and the input terminal current obtained by calculation; and then: The second switch module and the third switch module are controlled to be turned on, so that the first light-emitting diode, the first photodiode, the second light-emitting diode, the second photodiode and the divider start working, and the first bidirectional inverter module or the second bidirectional inverter module is controlled to perform compensation according to the ratio between the input current and the output current and the turns ratio of the transformer.

[0014] Optionally, controlling the first bidirectional inverter module or the second bidirectional inverter module to perform compensation according to the ratio between the input current and the output current and the turns ratio of the transformer includes: When the difference between the ratio of the input current to the output current and the turns ratio of the transformer is outside the error range, the first bidirectional inverter module or the second bidirectional inverter module is controlled to perform compensation.

[0015] The technical effect of the embodiment of the present invention is as follows: when the current at the output end is small, the first current detection module is directly started to detect the current at the input end, thereby avoiding the error of indirectly calculating the current through the turns ratio in the traditional solution. This direct measurement method improves the detection accuracy under low current conditions, ensuring that precise control can be achieved when the battery is close to full charge or low power. When the output current is large, the control module calculates the input current through the transformer turns ratio and no longer starts the first current detection module. Through this dynamic switching, the input current can be quickly obtained under high current conditions, reducing the load of the detection module and reducing power consumption. In the present technical solution, the control module monitors the actual values ​​of the output and input currents, and combines the preset transformer turns ratio to achieve real-time monitoring and precise control of the charge and discharge status. Even when the battery is close to full or the power is low, overcharging or over-discharging can be avoided through accurate measurement of small currents. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0017] Figure 1 This is a first structural schematic diagram of a DCDC bidirectional charging and discharging device provided in Embodiment 1 of the present invention; Figure 2 This is a second structural schematic diagram of a DCDC bidirectional charging and discharging device provided in the first embodiment of the present invention; Figure 3 This is a third structural schematic diagram of a DCDC bidirectional charging and discharging device provided in the first embodiment of the present invention; Figure 4 is a circuit diagram of a DCDC bidirectional charging and discharging device provided in Embodiment 1 of the present invention; Figure 5 is a flow chart of a control method of a DCDC bidirectional charging and discharging device provided in Embodiment 2 of the present invention; In the figure: 101, a first bidirectional inverter module; 102, a transformer; 103, a second bidirectional inverter module; 104, a first current detection module; 105, a second current detection module; 106, a control module; 107, a first light-emitting diode; 108, a first photodiode; 109, a second light-emitting diode; 110, a second photodiode; 111, a divider; 140, a first switch module; 141, a collection module; 142, a differential amplifier module; 151, a second switch module; 152, a third switch module. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] It should be understood that the present invention can be implemented in different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, providing these embodiments will make the disclosure thorough and complete and fully convey the scope of the present invention to those skilled in the art. In the accompanying drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. The same reference numerals throughout represent the same elements.

[0020] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to or coupled to other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on, directly adjacent to, directly connected to or directly coupled to other elements or layers, there may be no intervening elements or layers. It should be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below may be represented as a second element, component, region, layer or part.

[0021] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0022] In order to fully understand the present invention, detailed structures and steps will be presented in the following description to illustrate the technical solutions proposed by the present invention. The preferred embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0023] Embodiment 1 This embodiment 1 provides a DCDC bidirectional charging and discharging device, such as Figure 1 As shown, including: A first bidirectional inverter module 101 performs bidirectional conversion between a DC voltage and an AC voltage; A transformer 102, comprising a primary coil and a secondary coil, wherein the primary coil is connected to the first bidirectional inverter module 101; A second bidirectional inverter module 103, which is connected to the secondary coil to perform bidirectional conversion between AC voltage and DC voltage; A first current detection module 104, which is connected between the DC input terminal VIN and the first bidirectional inverter module 101, and is used to detect the input terminal current; A second current detection module 105, which is connected between the second bidirectional inverter module 103 and the DC output terminal VOUT and is used to detect the output terminal current; The control module 106 is connected to the first current detection module 104 and the second current detection module 105 respectively, and is used to collect the output current through the second current detection module 105, and when the absolute value of the output current is greater than the preset current value, calculate the input current according to the preset turns ratio of the transformer 102, and when the absolute value of the output current is not greater than the preset current value, start the first current detection module 104 and detect the input current through the first current detection module 104.

[0024] Among them, the first bidirectional inverter module 101 converts DC voltage into AC voltage, or converts AC voltage into DC voltage, to achieve bidirectional conversion from DC to AC and AC to DC. In charging mode, the module converts DC power into AC voltage and transmits it to the primary coil of the transformer 102; in discharging mode, the module receives the AC voltage of the primary coil of the transformer 102 and converts it into DC voltage for output. The transformer 102 realizes voltage conversion and electrical isolation through the primary coil and the secondary coil. In charging mode, the first bidirectional inverter module 101 converts DC voltage into AC voltage and inputs it into the primary coil of the transformer 102. After the turns ratio of the transformer 102 is transformed, the corresponding AC voltage is generated in the secondary coil and transmitted to the second bidirectional inverter module 103; in discharging mode, the electric energy is transmitted back from the secondary coil of the transformer 102 to the primary coil, completing the bidirectional transmission of energy. The second bidirectional inverter module 103 converts AC voltage into DC voltage, or converts DC voltage into AC voltage, to achieve bidirectional conversion between AC and DC. In charging mode, the module converts the AC voltage of the secondary coil of the transformer 102 into a DC voltage output; in discharging mode, the input DC voltage is converted into an AC voltage and transmitted to the secondary coil of the transformer 102. The first current detection module 104 detects the current value of the DC input terminal. In the charging mode with a small current, the first current detection module 104 monitors the current flowing from the DC input terminal to the first bidirectional inverter module 101 so that the control module 106 can obtain real-time current information. The second current detection module 105 detects the current value of the DC output terminal, and can monitor the output current in real time during the charging and discharging process. The control module 106 controls the charging and discharging process of the entire system, selects an appropriate current detection method, and ensures safe and stable operation of the system. When the output current is small, the control module 106 directly obtains the input current through the first current detection module 104. When the absolute value of the output current exceeds the preset threshold, the control module 106 will turn off the first current detection module 104, and obtain the output current through the second current detection module 105, and calculate the corresponding input current according to the turns ratio of the transformer 102. The calculation formula is: Iin=Iout×(N1 / N2), Iin is the input current, Iout is the output current, and N1 / N2 is the turns ratio of the transformer 102.

[0025] The technical effect of the technical solution provided in the first embodiment is that when the output current is small, the first current detection module is directly started to detect the input current, avoiding the error of the indirect current inference through the turns ratio in the traditional solution. This direct measurement method improves the detection accuracy under the low current state, ensuring that accurate control can be achieved when the battery is close to full power or low power state. When the output current is large, the control module calculates the input current through the transformer turns ratio and no longer starts the first current detection module. Through this dynamic switching, the input current can be quickly obtained under the high current state, reducing the load of the detection module and reducing power consumption. In this technical solution, the control module monitors the actual values ​​of the output and input currents and combines the preset transformer turns ratio to achieve real-time monitoring and precise control of the charging and discharging state. Even when the battery is close to full or the power is low, overcharging or over-discharging can be avoided by accurate measurement of small current. This technical solution effectively solves the influence of magnetic loss and interference on the accuracy of small current in the traditional solution through accurate small current detection, dynamic switching measurement method, and reliable charging and discharging control, ensuring safety and efficiency during the charging and discharging process of lithium batteries. This improvement enhances the battery's protection capabilities, prevents the risks of overcharging and over-discharging, extends battery life, and ultimately improves the overall system performance and reliability.

[0026] As an implementation method, Figure 2 As shown, the first current detection module 104 includes a first switch module 140, a collection module 141 and a differential amplifier module 142. The two ends of the first switch module 140 and the collection module 141 after being connected in parallel are respectively connected to the DC input end and the first bidirectional inverter module 101. The two ends of the collection module 141 are also respectively connected to the two input ends of the differential amplifier module 142. The output end of the differential amplifier module 142 is connected to the control module 106. When the absolute value of the output end current is greater than the preset current value, the control module 106 controls the first switch module 140 to be turned on; when the absolute value of the output end current is not greater than the preset current value, the control module 106 controls the first switch module 140 to be turned off, the collection module 141 collects the input end current, and the differential amplifier module 142 obtains the voltage difference signal on the collection module 141, and amplifies the voltage difference signal and outputs it to the control module 106.

[0027] Among them, when the control module 106 controls the first switch module 140 to be disconnected, the acquisition module 141 acquires the DC input current, and reflects the magnitude of the input current by the change of the voltage at both ends. When the current flows through the acquisition module 141, a corresponding voltage difference will be generated at both ends of the acquisition module 141, and the voltage difference is proportional to the input current. The differential amplifier module 142 differentially amplifies the voltage difference output by the acquisition module 141, and amplifies the small current signal to a voltage range suitable for the control module 106 to process. The two input ends of the differential amplifier module 142 are respectively connected to the two ends of the acquisition module 141 to receive the voltage difference signal. Through the design of the differential amplifier circuit, the module amplifies the tiny voltage difference and outputs an amplified signal proportional to the input current. The differentially amplified signal is transmitted to the control module 106 for real-time monitoring of the input current. The second current detection module 105 is a Hall sensor, which detects the current at the DC output end and obtains the current information through the magnetic field induction generated by the Hall effect. When the output end generates current, the Hall sensor senses the magnitude of the current according to the magnetic field strength generated by the current, and converts it into an electrical signal and outputs it to the control module 106. The control module 106 receives input current information from the acquisition module 141 through the differential amplifier module 142, which is mainly used for precise control of a small current range; at the same time, the control module 106 receives current information at the output end through the Hall sensor, which is used for monitoring and control of a large current range. According to different current states, the control module 106 can intelligently switch the current detection source to ensure that accurate and real-time current information can be obtained in different working modes.

[0028] The technical effect of this implementation is that the acquisition module and the differential amplifier module in the first current detection module provide high sensitivity and low error in small current detection, which is suitable for precise control; the Hall sensor of the second current detection module has the advantages of non-contact and low power consumption in the high current range. By controlling the first switch module to switch between the two detection modes, the combination of the two enables the system to efficiently respond to detection requirements under different current ranges, providing a strong guarantee for the safety and efficiency of the charging and discharging device.

[0029] As an implementation method, Figure 3As shown, the DCDC bidirectional charge and discharge device also includes a first light-emitting diode 107, a second switch module 151, a first photodiode 108, a second light-emitting diode 109, a third switch module 152, a second photodiode 110 and a divider 111. The first light-emitting diode 107 and the second switch module 151 are connected in parallel between the DC input end and the first current detection module 104, the second light-emitting diode 109 and the third switch module 152 are connected in parallel between the DC output end and the second current detection module 105, the first input end of the divider 111 is connected to the first photodiode 108, the second input end of the divider 111 is connected to the second photodiode 110, the output end of the divider 111 is connected to the control module 106, and the control module 106 is also connected to the first bidirectional inverter module 101 and the second bidirectional inverter module 103 respectively.

[0030] Among them, the control module 106 controls the second switch module 151 and the third switch module 152 to be turned on, and the main function of the first light-emitting diode 107 is to emit an optical signal corresponding to the input state according to the input voltage or current change. This optical signal is used to characterize the electrical characteristics of the input end (such as the magnitude and change of voltage or current). When the first bidirectional inverter module 101 receives the input voltage or current, the first light-emitting diode 107 emits a corresponding optical signal, and its intensity is proportional to the input voltage or current. This optical signal is used to transmit the input state and cooperate with the subsequent photodiode for signal processing. The first photodiode 108 is used to receive the optical signal from the first light-emitting diode 107 and convert the optical signal into a corresponding current signal. The current signal represents the voltage or current change at the input end of the first bidirectional inverter module 101, as one of the feedback signals of the system. The first photodiode 108 receives the optical signal emitted by the first light-emitting diode 107, converts the optical signal into a current signal, and transmits it to the first input end of the divider 111. The function of the second photodiode 110 is to receive the optical signal emitted by the second light-emitting diode 109, indicating the output end state of the second bidirectional inverter module 103. By converting the optical signal into a current signal, the second photodiode 110 provides a feedback signal of the output end for the second input end of the divider 111. The divider 111 plays a core role in signal processing in the system. By dividing the two feedback signals, the ratio of the system input to the output end is obtained. The control module 106 compares the ratio from the divider 111 with the turns ratio of the transformer 102, and adjusts the working state (such as PWM duty cycle or switching frequency) of the first bidirectional inverter module 101 and the second bidirectional inverter module 103 in real time. The turns ratio of the transformer 102 represents the theoretical input-output ratio. If the ratio signal and the turns ratio are close, it means that the input and output current or voltage state is balanced; if there is a deviation, it means that the input and output current or voltage is unbalanced and needs to be adjusted. The control module 106 determines whether it is necessary to adjust the working parameters of the bidirectional inverter module based on the difference between the ratio signal and the turns ratio. If the ratio signal deviates significantly from the turns ratio (for example, the ratio is higher or lower than the allowable error range of the turns ratio), it means that the current or voltage at the input and output ends do not match, which may lead to reduced system operating efficiency or even overcurrent or overvoltage. If an imbalance between the input and output ends is detected, the control module 106 will adjust the operating parameters of the bidirectional inverter module to restore the system balance. By changing the PWM duty cycle, the output voltage or current of the bidirectional inverter module can be adjusted, thereby affecting the power transmission of the system and helping to restore the input-output balance. The control module 106 can also affect the efficiency and transmission characteristics of the inverter module by adjusting the switching frequency to adapt to the changing requirements of the input and output and ensure higher conversion efficiency and stability. After the adjustment is completed, the control module 106 will continue to receive the ratio signal of the divider 111 and dynamically monitor the input and output status.When the ratio signal is close to the turns ratio, the adjustment is completed; if there is still a deviation, the control module 106 continues to fine-tune until the system reaches an ideal balance state.

[0031] The technical effect of this embodiment is that the above working mechanism of the control module ensures the dynamic balance adjustment capability of the system, so that the input and output can remain stable under different loads and working conditions. By adjusting the PWM duty cycle and switching frequency of the bidirectional inverter module, the control module can optimize the power conversion efficiency, prevent overcurrent or overvoltage protection from being triggered, and ultimately improve the safety, stability and working efficiency of the system.

[0032] The present embodiment is described below through a specific circuit structure: Figure 4 As shown, the first bidirectional inverter module 101 includes a first MOS transistor Q1, a second MOS transistor Q2, a third MOS transistor Q3 and a fourth MOS transistor Q4; the drain of the first MOS transistor Q1 and the drain of the second MOS transistor Q2 are connected together as a first end of the first bidirectional inverter module 101, the source of the third MOS transistor Q3 and the source of the fourth MOS transistor Q4 are connected together as a second end of the first bidirectional inverter module 101, the source of the first MOS transistor Q1 and the drain of the third MOS transistor Q3 are connected together as a third end of the first bidirectional inverter module 101, and the source of the second MOS transistor Q2 and the drain of the fourth MOS transistor Q4 are connected together as a fourth end of the first bidirectional inverter module 101. The second end of the first bidirectional inverter module 101 is respectively connected to one end of the resistor R0, one end of the resistor R1 and one end of the switch K, the other end of the resistor R0 is respectively connected to the other end of the switch K and one end of the resistor R2, the other end of the resistor R1 is connected to the non-inverting input end of the operational amplifier U1, the other end of the resistor R2 is connected to the inverting input end of the operational amplifier U1, and the output end of the operational amplifier U1 and the control end of the switch K are respectively connected to the MCU.

[0033] The second bidirectional inverter module 103 includes a first IGBT module Q5, a second IGBT module Q6, a third IGBT module Q7 and a fourth IGBT module Q8; the second end of the first IGBT module Q5 and the first end of the second IGBT module Q6 are connected together as the second end of the second bidirectional inverter module 103, the second end of the third IGBT module Q7 and the first end of the fourth IGBT module Q8 are connected together as the first end of the second bidirectional inverter module 103, the first end of the first IGBT module Q5 and the first end of the third IGBT module Q7 are connected together as the third end of the second bidirectional inverter module 103, the second end of the second IGBT module Q6 and the second end of the fourth IGBT module Q8 are connected together as the fourth end of the second bidirectional inverter module 103, and the third end of the second bidirectional inverter module 103 is connected to the Hall sensor HCT, which is also connected to the MCU.

[0034] The working process of this circuit structure is as follows: the energy storage system is running, and the current I2 on the secondary high voltage side is measured by the Hall sensor HCT. The primary current I1=I2×n is obtained through the transformer turns ratio N2 / N1=n, and the battery current value can be obtained. When the battery current is less than 5A, the current detection value on the secondary high voltage side is (5 / n)A. The larger the ratio, the more difficult it is to detect small currents. The MCU of the energy storage inverter generally uses an 8-bit resolution, but the measurement current range is relatively large, so when the current is smaller, the sampling will have a relatively large error. The MCU collects current less than 5A through the battery side sampling resistor R0, with an 8-bit sampling accuracy and a sampling range of -5A to +5A, which greatly improves the sampling accuracy. By using the resistor R0 and HCT sampling to calculate I3 and I1 for comparison and calibration, an accurate current value can be obtained. In lithium battery charging, poor small current accuracy often causes battery overvoltage. When the lithium battery is nearly full, only a small current is needed, which will cause the battery voltage to rise rapidly, resulting in overvoltage protection and affecting the battery life.

[0035] Embodiment 2 This embodiment 2 provides a control method for the DCDC bidirectional charging and discharging device provided in embodiment 1, and the control method includes: Step S101: When the absolute value of the output current is greater than a preset current value, the input current is calculated according to a preset transformer turns ratio.

[0036] Step S102: When the absolute value of the output-end current is not greater than the preset current value, the first current detection module is started, and the input-end current is detected according to the first current detection module.

[0037] Among them, the control module monitors the absolute value of the current at the output end in real time and compares it with the preset current threshold. When it is detected that the absolute value of the current at the output end is greater than the preset current value, the control module does not start the first current detection module, but directly calculates the input end current according to a preset turns ratio. The calculation formula is: Iin=Iout×(N1 / N2), where N1 / N2 is the turns ratio of the transformer. When it is detected that the current value at the output end is not greater than the preset current value, the control module starts the first current detection module to directly measure the actual current value at the input end. The first current detection module directly measures the actual current at the input end and feeds the measured current value back to the control module for real-time control and adjustment of the system.

[0038] The technical effect of this embodiment is that under high current conditions, the input current is calculated by the turns ratio, which simplifies the detection process and reduces power consumption; under low current conditions, the first current detection module is directly used to measure the input current and obtain current data. By adopting this dynamic switching detection method, the best detection accuracy and efficiency can be achieved within different current ranges, ensuring the safety and stability of the charging and discharging process.

[0039] As an implementation mode, the first current detection module includes a first switch module, a collection module and a differential amplification module. The first current detection module detects the input current, including: The first switch module is controlled to be turned on, the input current is collected by the collection module to form a voltage difference, the voltage difference signal on the collection module is obtained by the differential amplifier module, and the voltage difference signal is amplified.

[0040] Among them, the first current detection module starts working by controlling the first switch module to be turned on. When the current flows through the acquisition module, the acquisition module will generate a voltage difference proportional to the input current. The two input ends of the differential amplifier module are respectively connected to the endpoints of the acquisition module to receive the voltage difference signal. By amplifying the voltage difference, the differential amplifier module makes the voltage signal after the tiny input current change amplified for detection and analysis by the subsequent processing module, and can maintain the position even in a small current range. In addition, the amplified signal provides accurate feedback for the control module, improving the dynamic response capability of the system.

[0041] The technical effect of this embodiment is that the process realizes accurate measurement of input current through the collaboration of the first switch module, the acquisition module and the differential amplifier module. The current-voltage conversion of the acquisition module makes the signal more processable, the design of the differential amplifier module ensures the anti-interference of the signal, and the amplification step further improves the accuracy and precision of the detection. Finally, the signal processing queue improves the stability and response speed of the system, and can reliably monitor and feedback the input current in real time.

[0042] As an implementation manner, the input terminal current is detected according to the first current detection module, and then the method further includes: When it is determined that an error occurs in the transformer according to the detected input terminal current and the calculated input terminal current, compensation is performed by controlling the first bidirectional inverter module or the second bidirectional inverter module.

[0043] Specifically, when the detected input current is higher than the calculated input terminal, it is determined that the transformer has additional energy loss resulting in reduced transmission efficiency, and the first bidirectional inverter module or the second bidirectional inverter module is controlled to increase the input current.

[0044] Among them, according to the deviation direction of the input current (that is, the detected current is greater than or less than the calculated current), the control module determines whether the transformer has losses. If the detected input current is higher than the calculated current, it is determined that the transformer has additional energy loss, resulting in reduced transmission efficiency. If the system needs to increase the input power, the control module can increase the PWM duty cycle of the first bidirectional inverter module so that more energy is transmitted to the transformer and the input current is increased. In addition to adjusting the first bidirectional inverter module, the working state of the second bidirectional inverter module can also be adjusted to further optimize the power transmission efficiency: appropriately increase or decrease the switching frequency of the second bidirectional inverter module to affect the output current size and response speed to meet the compensation requirements. The adjustment of the second bidirectional inverter module is mainly based on the changes in the demand of the load end, helping to transmit the compensated power to the output end more efficiently. After completing the preliminary compensation, the control module continues to monitor the difference between the actual value and the calculated value of the input current in real time. If the difference gradually decreases, it means that the compensation is effective; if the difference still exists, the control module will further fine-tune the working parameters of the two inverter modules.

[0045] The technical effect of this implementation is that the control module increases or decreases the transmission power by finely adjusting the PWM duty cycle and switching frequency of the first bidirectional inverter module, and improves the responsiveness of the output end by optimizing the state of the second bidirectional inverter module, thereby achieving effective compensation for transformer loss. Ultimately, the compensation mechanism improves the stability of the system, ensures the balance of power transmission, and avoids problems such as efficiency reduction and current mismatch caused by transformer loss.

[0046] As an implementation mode, the DCDC bidirectional charge and discharge device further includes a first light emitting diode, a second switch module, a first photodiode, a second light emitting diode, a third switch module, a second photodiode and a divider, wherein the first light emitting diode and the second switch module are connected in parallel between the DC input terminal and the first current detection module, the second light emitting diode and the third switch module are connected in parallel between the DC output terminal and the second current detection module, the first input terminal of the divider is connected to the first photodiode, the second input terminal of the divider is connected to the second photodiode, the output terminal of the divider is connected to the control module, and the control module is also connected to the first bidirectional inverter and the second bidirectional inverter respectively; According to the input terminal current obtained by detection and the input terminal current obtained by calculation, it is judged that a fault occurs, and then it also includes: The second switch module and the third switch module are controlled to be turned on, so that the first light-emitting diode, the first photodiode, the second light-emitting diode, the second photodiode and the divider start working, and the first bidirectional inverter module or the second bidirectional inverter module is controlled to perform compensation according to the ratio between the input current and the output current and the turns ratio of the transformer.

[0047] Controlling the first bidirectional inverter module or the second bidirectional inverter module to perform compensation according to the ratio between the input current and the output current and the turns ratio of the transformer, including: When the difference between the ratio of the input current to the output current and the turns ratio of the transformer is outside the error range, the first bidirectional inverter module or the second bidirectional inverter module is controlled to perform compensation.

[0048] Among them, the first light-emitting diode is started, and the first light-emitting diode emits a light signal according to the magnitude of the input current, and its light intensity is proportional to the input current. The first photodiode receives the light signal from the first light-emitting diode, converts it into a current signal, and transmits it to the first input end of the divider. The second light-emitting diode is started, and the second light-emitting diode emits a light signal according to the magnitude of the output current, and its light intensity is proportional to the output current. The second photodiode receives the light signal from the second light-emitting diode, converts it into a current signal, and transmits it to the second input end of the divider. The divider receives current signals from the first photodiode and the second photodiode, which represent the input current and the output current respectively. The divider performs a ratio operation on the two signals, calculates the ratio between the input current and the output current, and transmits the result to the control module. The control module compares the input-output current ratio calculated by the divider with the turns ratio of the transformer. The turns ratio represents the ideal input-output current ratio. If the ratio deviates from the turns ratio range (for example, the threshold is set to ±5%), it is determined that the system has energy loss or mismatch. When the difference between the ratio and the turns ratio exceeds a preset threshold, the control module starts the compensation operation, which is as follows: If it is detected that the ratio deviates from the turns ratio, it indicates that the input energy is insufficient or the transformer loss increases. The control module can increase the input current by adjusting the PWM duty cycle or switching frequency of the first bidirectional inverter module to compensate for the energy loss. In some cases, the output power can also be optimized by adjusting the parameters of the second bidirectional inverter module (such as PWM or switching frequency). After compensation, the control module continues to monitor the input-output current ratio. If the ratio approaches the turns ratio, it means that the compensation is successful; if the deviation still exists, the system will continue to fine-tune the parameters of the first or second bidirectional inverter module until a balanced state is reached.

[0049] The technical effect of this embodiment is that the state of the input and output currents is monitored by starting the photoelectric coupling module and the divider, and the ratio is compared with the transformer turns ratio to determine whether compensation is required. When there is an imbalance or loss, the control module compensates by adjusting the working parameters of the inverter module to restore the ideal state of the system. This process ensures efficient transmission and stable operation of the system under various load conditions.

[0050] Furthermore, the light-emitting diode and the photodiode can also be used to detect the temperature, and the temperature can be estimated by using the change characteristics of the forward voltage and the change of the luminous efficiency of the LED. The specific implementation method is as follows: The luminous efficiency and forward voltage characteristics of the light-emitting diode will change with temperature, and these characteristics can be used as the basis for temperature detection. Photodiodes can be used to receive light signals from light-emitting diodes and then detect temperature changes. Connect the first light-emitting diode and the second light-emitting diode to a constant current source. When the temperature rises, the forward voltage of the first light-emitting diode and the second light-emitting diode will decrease. Use the control module to monitor the change in the forward voltage of the first light-emitting diode and the second light-emitting diode, and map this voltage change to a temperature value. Establish a calibration curve of forward voltage and temperature in the system, and estimate the real-time temperature by detecting the voltage change. When the temperature rise is detected, temperature compensation is performed by adjusting the input or output parameters of the transformer. For example, the duty cycle or operating frequency of the inverter module is appropriately adjusted to reduce the power loss caused by the temperature rise. When the temperature rises, the influence of high temperature on the circuit performance is reduced by reducing the current density or improving the heat dissipation efficiency, so as to maintain the efficient operation of the transformer.

[0051] In a DCDC bidirectional charging and discharging device, the power loss caused by the temperature rise can be reduced by appropriately adjusting the duty cycle or operating frequency of the inverter module. This can usually be achieved through the following control strategies and technologies: When the temperature exceeds the preset threshold, the control module automatically triggers the adjustment of the duty cycle or operating frequency according to the temperature feedback to reduce the power loss. The control module dynamically adjusts the PWM duty cycle of the inverter module to reduce the power loss: When the temperature rises, the duty cycle can be reduced to reduce the current peak flowing through the transformer or inverter module. By reducing the power output and limiting the current, the copper loss and switching loss caused by high temperature can be effectively reduced. A graded temperature control mechanism is designed to adjust the duty cycle and frequency to different degrees by setting multiple temperature thresholds. For example: Low temperature (below the safe temperature range): maintain normal frequency and duty cycle. Medium temperature (close to the upper limit temperature): reduce a certain percentage of the duty cycle and slightly reduce the operating frequency. High temperature (exceeding the upper limit of the safe temperature): further reduce the duty cycle or significantly reduce the operating frequency to ensure system safety. The control module will automatically select different adjustment schemes according to the current temperature range to achieve graded adjustment, thereby taking into account both efficiency and safety.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such 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, and should be included in the protection scope of the present invention.

Claims

1. A DCDC bidirectional charging and discharging device, characterized in that: include: A first bidirectional inverter module performs bidirectional conversion between DC voltage and AC voltage; A transformer, comprising a primary coil and a secondary coil, wherein the primary coil is connected to the first bidirectional inverter module; A second bidirectional inverter module, connected to the secondary coil, to perform bidirectional conversion between AC voltage and DC voltage; A first current detection module, connected between the DC input terminal and the first bidirectional inverter module, for detecting the input terminal current; A second current detection module, connected between the second bidirectional inverter module and the DC output terminal, for detecting the output terminal current; A control module, which is respectively connected to the first current detection module and the second current detection module, and is used to collect the output end current through the second current detection module, and when the absolute value of the output end current is greater than the preset current value, calculate the input end current according to the turns ratio of the preset transformer, and when the absolute value of the output end current is not greater than the preset current value, start the first current detection module and detect the input end current through the first current detection module.

2. The DCDC bidirectional charge and discharge device according to claim 1, characterized in that: The first current detection module includes a first switch module, a collection module and a differential amplifier module, wherein two ends of the first switch module and the collection module connected in parallel are respectively connected to the DC input end and the first bidirectional inverter module, and two ends of the collection module are also respectively connected to two input ends of the differential amplifier module, and the output end of the differential amplifier module is connected to the control module; When the absolute value of the output current is greater than a preset current value, the control module controls the first switch module to be turned on; When the absolute value of the output current is not greater than the preset current value, the control module controls the first switch module to be turned on, the acquisition module acquires the input current, the differential amplifier module acquires the voltage difference signal on the acquisition module, and amplifies the voltage difference signal and outputs it to the control module.

3. The DCDC bidirectional charge and discharge device according to claim 1, characterized in that: The second current detection module is a Hall sensor, and the Hall sensor is used to detect the output end current.

4. The DCDC bidirectional charge and discharge device according to claim 1, characterized in that: The DCDC bidirectional charge and discharge device also includes a first light emitting diode, a second switch module, a first photodiode, a second light emitting diode, a third switch module, a second photodiode and a divider. The first light emitting diode and the second switch module are connected in parallel between the DC input end and the first current detection module. The second light emitting diode and the third switch module are connected in parallel between the DC output end and the second current detection module. The first input end of the divider is connected to the first photodiode, the second input end of the divider is connected to the second photodiode, the output end of the divider is connected to the control module, and the control module is also connected to the first bidirectional inverter and the second bidirectional inverter respectively.

5. A control method based on the DCDC bidirectional charge and discharge device according to claim 1, characterized in that: The control method comprises: When the absolute value of the output terminal current is greater than a preset current value, calculating the input terminal current according to a preset transformer turns ratio; When the absolute value of the output-end current is not greater than a preset current value, the first current detection module is started, and the input-end current is detected according to the first current detection module.

6. The control method according to claim 5, characterized in that: The first current detection module includes a first switch module, a collection module and a differential amplification module. The input terminal current is detected according to the first current detection module, including: The first switch module is controlled to be turned on, the input end current is collected by the collection module to form a voltage difference, the voltage difference signal on the collection module is obtained by the differential amplification module, and the voltage difference signal is amplified.

7. The control method according to claim 5, characterized in that: After detecting the input terminal current according to the first current detection module, the method further includes: When it is determined that an error occurs in the transformer according to the detected input terminal current and the calculated input terminal current, compensation is performed by controlling the first bidirectional inverter module or the second bidirectional inverter module.

8. The control method according to claim 7, characterized in that: When it is determined according to the input end current obtained by detection and the input end current obtained by calculation that the transformer fails, compensation is performed by controlling the first bidirectional inverter module or the second bidirectional inverter module, including: When the detected input current is higher than the calculated input terminal, it is determined that there is additional energy loss in the transformer resulting in reduced transmission efficiency, and the first bidirectional inverter module or the second bidirectional inverter module is controlled to increase the input current.

9. The control method according to claim 7, characterized in that: The DCDC bidirectional charge and discharge device further includes a first light emitting diode, a second switch module, a first photodiode, a second light emitting diode, a third switch module, a second photodiode and a divider. The first light emitting diode and the second switch module are connected in parallel between the DC input terminal and the first current detection module. The second light emitting diode and the third switch module are connected in parallel between the DC output terminal and the second current detection module. The first input terminal of the divider is connected to the first photodiode, the second input terminal of the divider is connected to the second photodiode, the output terminal of the divider is connected to the control module, and the control module is also connected to the first bidirectional inverter and the second bidirectional inverter respectively. The method further comprises: determining that a fault occurs according to the input terminal current obtained by detection and the input terminal current obtained by calculation; and then: The second switch module and the third switch module are controlled to be turned on, so that the first light-emitting diode, the first photodiode, the second light-emitting diode, the second photodiode and the divider start working, and the first bidirectional inverter module or the second bidirectional inverter module is controlled to perform compensation according to the ratio between the input current and the output current and the turns ratio of the transformer.

10. The control method according to claim 9, characterized in that: The controlling the first bidirectional inverter module or the second bidirectional inverter module to perform compensation according to the ratio between the input current and the output current and the turns ratio of the transformer includes: When the difference between the ratio of the input current to the output current and the turns ratio of the transformer is outside the error range, the first bidirectional inverter module or the second bidirectional inverter module is controlled to perform compensation.

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