DCDC Bidirectional Charging and Discharging Device and Its Control Method

Abstract

The present invention discloses a DCDC bidirectional charge and discharge device and its control method. The DCDC bidirectional charge and discharge device includes a first bidirectional inverter module, a transformer, a second bidirectional inverter module, a first current detection module, a second current detection module, and a control module. The control module collects the output current through the second current detection module, and when the absolute value of the output current is greater than a preset current value, calculates the input current according to the preset transformer turns ratio, and when the absolute value of the output current is not greater than the preset current value, activates the first current detection module and detects the input current through the first current detection module. This technical solution directly activates the first current detection module to detect the input current when the output current is small, avoiding the error of indirectly calculating the current through the turns ratio in the traditional solution.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage inverters, and particularly relates 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 devices connecting the power generation end to the power grid or load, their performance is 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 put forward for the measurement accuracy of current in actual applications.

[0003] Accurate current measurement is crucial for preventing overcharging or over-discharging of the battery. Overcharging will cause internal heating of the battery, which may lead to battery damage or even safety hazards in severe cases, while over-discharging will have a negative impact on the battery life. The traditional solution usually indirectly calculates the actual current of the battery through a battery sensor (such as a Hall sensor) on the high-voltage side. This solution uses the turns ratio relationship of the transformer to deduce the battery current, but due to the magnetic loss of the transformer and other external interferences, it is often difficult to achieve accurate measurement when the current is low, thus affecting the measurement accuracy in the small current state. This is difficult to provide sufficient accuracy for accurately controlling the charge and discharge process of lithium batteries, especially when the battery is close to full charge or low power state. Summary of the Invention

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

[0005] In a first aspect of embodiments of the present invention, a DCDC bidirectional charging and discharging circuit is provided, including:

[0006] A first bidirectional inverter module for bidirectionally converting DC voltage and AC voltage;

[0007] A transformer including a primary coil and a secondary coil, the primary coil being connected to the first bidirectional inverter module;

[0008] A second bidirectional inverter module connected to the secondary coil for bidirectionally converting AC voltage and DC voltage;

[0009] A first current detection module connected between the DC input terminal and the first bidirectional inverter module for detecting the input terminal current;

[0010] A second current detection module connected between the second bidirectional inverter module and the DC output terminal for detecting the output terminal current;

[0011] A control module, which is respectively connected to the first current detection module and the second current detection module, is configured to collect the output current through the second current detection module, calculate the input current according to the turns ratio of a preset transformer when the absolute value of the output current is greater than a preset current value, and start the first current detection module and detect the input current through the first current detection module when the absolute value of the output current is not greater than the preset current value.

[0012] Optionally, the first current detection module includes a first switch module, a collection module, and a differential amplification module. The two ends after the parallel connection of the first switch module and the collection module are respectively connected to the DC input end and the first bidirectional inverter module. The two ends of the collection module are also respectively connected to the two input ends of the differential amplification module, and the output end of the differential amplification module is connected to the control module;

[0013] When the absolute value of the output current is greater than the preset current value, the control module controls the first switch module to conduct;

[0014] 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 conduct, the collection module collects the input current, the differential amplification module obtains the voltage difference signal on the collection module, and outputs the amplified voltage difference signal to the control module.

[0015] Optionally, the second current detection module is a Hall sensor, and the Hall sensor is configured to detect the output current.

[0016] 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. 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 respectively connected to the first bidirectional inverter and the second bidirectional inverter.

[0017] A second aspect of the embodiments of the present invention provides a control method based on the DCDC bidirectional charge and discharge device described in the first aspect. The control method includes:

[0018] When the absolute value of the output current is greater than the preset current value, calculate the input current according to the preset transformer turns ratio;

[0019] When the absolute value of the current at the output terminal is not greater than the preset current value, start the first current detection module and detect the input terminal current according to the first current detection module.

[0020] Optionally, the first current detection module includes a first switch module, a collection module, and a differential amplification module. The detecting the input terminal current according to the first current detection module includes:

[0021] Control the first switch module to conduct, collect the input terminal current through the collection module to form a voltage difference, obtain the voltage difference signal on the collection module through the differential amplification module, and amplify the voltage difference signal.

[0022] Optionally, after detecting the input terminal current according to the first current detection module, it further includes:

[0023] When it is determined that the transformer has an error according to the detected input terminal current and the calculated input terminal current, compensate by controlling the first bidirectional inverter module or the second bidirectional inverter module.

[0024] Optionally, when it is determined that the transformer has a fault according to the detected input terminal current and the calculated input terminal current, compensating by controlling the first bidirectional inverter module or the second bidirectional inverter module includes:

[0025] 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 control the first bidirectional inverter module or the second bidirectional inverter module to increase the input current.

[0026] 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. 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 further connected to the first bidirectional inverter and the second bidirectional inverter respectively;

[0027] After determining a fault according to the detected input terminal current and the calculated input terminal current, it further includes:

[0028] Control the second switch module and the third switch module to conduct, so that the first light-emitting diode, the first photodiode, the second light-emitting diode, the second photodiode, and the divider start to work, and control 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.

[0029] Optionally, 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:

[0030] 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, control the first bidirectional inverter module or the second bidirectional inverter module to perform compensation.

[0031] The technical effect of the embodiment of the present invention is as follows: In this technical solution, when the output current is small, the first current detection module is directly activated to detect the input current, avoiding the error of indirectly calculating the current through the turns ratio in the traditional solution. This direct measurement method improves the detection accuracy in the small current state, ensuring precise control 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 turns ratio of the transformer and does not activate the first current detection module. Through this dynamic switching, the input current can be quickly obtained in the large current state, reducing the load of the detection module and lowering the power consumption. In this technical solution, the control module monitors the actual values of the output current and the input current, and combines the preset turns ratio of the transformer to achieve real-time monitoring and precise control of the charge and discharge state. Even when the battery is close to full charge or has low power, overcharging or over-discharging can be avoided through the precise measurement of small currents. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 It is the first structural schematic diagram of a DCDC bidirectional charge and discharge device provided by Embodiment 1 of the present invention;

[0034] Figure 2 It is the second structural schematic diagram of a DCDC bidirectional charge and discharge device provided by Embodiment 1 of the present invention;

[0035] Figure 3It is the third structural schematic diagram of a DCDC bidirectional charge and discharge device provided in Embodiment 1 of the present invention;

[0036] Figure 4 It is the circuit diagram of a DCDC bidirectional charge and discharge device provided in Embodiment 1 of the present invention;

[0037] Figure 5 It is the flowchart of a control method of a DCDC bidirectional charge and discharge device provided in Embodiment 2 of the present invention;

[0038] In the figure: 101, the first bidirectional inverter module; 102, the transformer; 103, the second bidirectional inverter module; 104, the first current detection module; 105, the second current detection module; 106, the control module; 107, the first light emitting diode; 108, the first photodiode; 109, the second light emitting diode; 110, the second photodiode; 111, the divider; 140, the first switch module; 141, the acquisition module; 142, the differential amplification module; 151, the second switch module; 152, the third switch module. Detailed implementation manners

[0039] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0040] It should be understood that the present invention can be implemented in different forms and should not be construed as limited to the embodiments presented herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals denote the same elements throughout the drawings.

[0041] It should be understood that when an element or layer is referred to as "on", "adjacent to", "connected to", or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as "directly on", "directly adjacent to", "directly connected to", or "directly coupled to" another element or layer, there are 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. Thus, without departing from the teachings of the present invention, the first element, component, region, layer, or part discussed below may be denoted as the second element, component, region, layer, or part.

[0042] The purpose of the terms used herein is only to describe specific embodiments and is not a limitation of the present invention. As used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. As used herein, the term "and / or" includes any and all combinations of the associated listed items.

[0043] To thoroughly 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. However, in addition to these detailed descriptions, the present invention may have other embodiments.

[0044] Embodiment 1

[0045] The first embodiment provides a DCDC bidirectional charge and discharge device, as Figure 1 shown, comprising:

[0046] A first bidirectional inverter module 101 for bidirectionally converting DC voltage and AC voltage;

[0047] A transformer 102, which includes a primary coil and a secondary coil, and the primary coil is connected to the first bidirectional inverter module 101;

[0048] A second bidirectional inverter module 103, which is connected to the secondary coil to bidirectionally convert AC voltage and DC voltage;

[0049] The first current detection module 104, which is connected between the DC input terminal VIN and the first bidirectional inverter module 101, is used to detect the input terminal current;

[0050] The second current detection module 105, which is connected between the second bidirectional inverter module 103 and the DC output terminal VOUT, is used to detect the output terminal current;

[0051] The control module 106, which is respectively connected to the first current detection module 104 and the second current detection module 105, is used to collect the output terminal current through the second current detection module 105, and when the absolute value of the output terminal current is greater than the preset current value, calculate the input terminal current according to the turns ratio of the preset transformer 102, and when the absolute value of the output terminal current is not greater than the preset current value, start the first current detection module 104 and detect the input terminal current through the first current detection module 104.

[0052] Among them, the first bidirectional inverter module 101 converts DC voltage into AC voltage or converts AC voltage into DC voltage, realizing bidirectional conversion between DC and AC. In the charging mode, this module converts the DC power supply into AC voltage and transmits it to the primary coil of the transformer 102; in the discharging mode, this 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 the charging mode, the first bidirectional inverter module 101 converts DC voltage into AC voltage and inputs it to the primary coil of the transformer 102. After the turns ratio conversion of the transformer 102, a corresponding AC voltage is generated in the secondary coil and transmitted to the second bidirectional inverter module 103; in the discharging mode, electrical energy is transmitted back from the secondary coil of the transformer 102 to the primary coil to complete bidirectional energy transmission. The second bidirectional inverter module 103 converts AC voltage into DC voltage or converts DC voltage into AC voltage, realizing bidirectional conversion between AC and DC. In the charging mode, this module converts the AC voltage of the secondary coil of the transformer 102 into DC voltage for output; in the discharging mode, it converts the input DC voltage into AC voltage and transmits it to the secondary coil of the transformer 102. The first current detection module 104 detects the current value at the DC input end. In the charging mode with a small current, the first current detection module 104 monitors the current flowing from the DC input end 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 at the DC output end and can monitor the output current in real time during both the charging and discharging processes. The control module 106 controls the charging and discharging processes of the entire system, selects an appropriate current detection method to ensure the 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), where Iin is the input current, Iout is the output current, and N1 / N2 is the turns ratio of the transformer 102.

[0053] The technical effect of the technical solution provided in the first embodiment is as follows: when the output current is small, the first current detection module is directly activated to detect the input current, avoiding the error of indirectly calculating the current through the turns ratio in the traditional solution. This direct measurement method improves the detection accuracy in the small current state, ensuring precise control 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 does not activate the first current detection module. Through this dynamic switching, the input current can be quickly obtained in the large current state, reducing the load of the detection module and lowering the power consumption. In this technical solution, the control module monitors the actual values of the output and input currents and, in combination with the preset transformer turns ratio, realizes real-time monitoring and precise control of the charge and discharge states. Even when the battery is close to full charge or has low power, overcharge or over-discharge can be avoided through precise measurement of small currents. This technical solution effectively solves the influence of magnetic loss and interference on the small current accuracy in the traditional solution through precise small current detection, dynamic switching measurement methods, and reliable charge and discharge control, ensuring the safety and efficiency during the lithium battery charge and discharge process. This improvement enhances the battery protection ability, prevents the risk of overcharge and over-discharge, extends the battery life, and ultimately improves the overall system performance and reliability.

[0054] As an implementation manner, as Figure 2 shown, the first current detection module 104 includes a first switch module 140, a sampling module 141, and a differential amplification module 142. The two ends after the parallel connection of the first switch module 140 and the sampling module 141 are respectively connected to the DC input end and the first bidirectional inverter module 101. The two ends of the sampling module 141 are also respectively connected to the two input ends of the differential amplification module 142. The output end of the differential amplification module 142 is connected to the control module 106. When the absolute value of the output current is greater than the preset current value, the control module 106 controls the first switch module 140 to conduct; when the absolute value of the output current is not greater than the preset current value, the control module 106 controls the first switch module 140 to disconnect. The sampling module 141 samples the input current, and the differential amplification module 142 obtains the voltage difference signal on the sampling module 141, amplifies the voltage difference signal, and outputs it to the control module 106.

[0055] Among them, when the control module 106 controls the first switch module 140 to disconnect, the acquisition module 141 acquires the DC input current, and reflects the magnitude of the input current through 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 this voltage difference is proportional to the input current. The differential amplification module 142 performs differential amplification on the voltage difference output by the acquisition module 141, and amplifies the small current signal to a voltage range suitable for processing by the control module 106. The two input terminals of the differential amplification module 142 are respectively connected to both ends of the acquisition module 141 to receive the voltage difference signal. Through the design of the differential amplification circuit, this 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 terminal current. The second current detection module 105 is a Hall sensor, and the Hall sensor detects the current at the DC output terminal and obtains the current information through the magnetic field induction generated by the Hall effect. When a current is generated at the output terminal, 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 the input current information from the acquisition module 141 through the differential amplification module 142, which is mainly used for precise control in the small current range; at the same time, the control module 106 receives the current information at the output terminal through the Hall sensor for monitoring and control in the large current range. According to different current states, the control module 106 can intelligently switch the current detection source to ensure accurate and real-time current information can be obtained under different working modes.

[0056] The technical effect of this embodiment is as follows: The acquisition module and the differential amplification module in the first current detection module provide high sensitivity and low error in small current detection and are 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 realize the switching between the two detection methods, the combination of the two enables the system to efficiently meet the detection requirements under different current ranges, providing a strong guarantee for the safety and efficiency of the charge and discharge device.

[0057] As an implementation manner, such as Figure 3As shown, the DCDC bidirectional charging and discharging device further 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 terminal 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 terminal and the second current detection module 105. The first input terminal of the divider 111 is connected to the first photodiode 108, the second input terminal of the divider 111 is connected to the second photodiode 110, and the output terminal of the divider 111 is connected to the control module 106. The control module 106 is further connected to the first bidirectional inverter module 101 and the second bidirectional inverter module 103 respectively.

[0058] Among them, the control module 106 controls the second switch module 151 and the third switch module 152 to conduct. The main function of the first light-emitting diode 107 is to emit an optical signal corresponding to the input state according to the change of the input voltage or current. 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 this optical signal into a corresponding current signal. This current signal represents the voltage or current change at the input end of the first bidirectional inverter module 101 and is 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 this system. By performing a division calculation on 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 states (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 indicates that the input-output current or voltage state is balanced; if there is a deviation, it indicates that the input-output current or voltage is unbalanced and needs to be adjusted. The control module 106 determines whether to adjust the working parameters of the bidirectional inverter module according to the difference between the ratio signal and the turns ratio. If the ratio signal significantly deviates from the turns ratio (for example, the ratio is higher or lower than the allowable error range of the turns ratio), it indicates that the current or voltage at the input end and the output end do not match, which may lead to a decrease in the system operation efficiency and even overcurrent or overvoltage conditions. If it is detected that the input-output end is unbalanced, the control module 106 will adjust the working 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 from the divider 111 and dynamically monitor the input-output state.When the ratio signal approaches the turns ratio, the adjustment ends; if there is still a deviation, the control module 106 continues to finely adjust until the system reaches an ideal balanced state.

[0059] The technical effect of this embodiment is that the above working mechanism of the control module ensures the dynamic balance adjustment ability of the system, enabling the input and output to 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 the triggering of overcurrent or overvoltage protection, and ultimately improve the safety, stability, and working efficiency of the system.

[0060] The following will illustrate this embodiment through a specific circuit structure: As Figure 4 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 drains of the first MOS transistor Q1 and the second MOS transistor Q2 are commonly connected as the first end of the first bidirectional inverter module 101, the sources of the third MOS transistor Q3 and the fourth MOS transistor Q4 are commonly connected as the 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 commonly connected as the 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 commonly connected as the 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 a resistor R0, one end of a resistor R1, and one end of a switch K. The other end of the resistor R0 is respectively connected to the other end of the switch K and one end of a resistor R2. The other end of the resistor R1 is connected to the non-inverting input terminal of an operational amplifier U1, and the other end of the resistor R2 is connected to the inverting input terminal of the operational amplifier U1. The output terminal of the operational amplifier U1 and the control terminal of the switch K are respectively connected to the MCU.

[0061] 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 commonly connected 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 commonly connected 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 commonly connected as the third end of the second bidirectional inverter module 103, and the second end of the second IGBT module Q6 and the second end of the fourth IGBT module Q8 are commonly connected as the fourth end of the second bidirectional inverter module 103. The third end of the second bidirectional inverter module 103 is connected to a Hall sensor HCT, and the Hall sensor HCT is also connected to the MCU.

[0062] The working process of this circuit structure is as follows: When the energy storage system is operating, the current I2 on the secondary high-voltage side is measured through the Hall sensor HCT. By the transformer turns ratio N2 / N1 = n, the primary-side current I1 = I2 × n can be obtained, and the battery current value can be obtained. When the battery current is less than 5A, the detected current value on the secondary high-voltage side is (5 / n)A. The larger the turns ratio, the more difficult it is to detect small currents. Currently, the resolution of the energy storage inverter MCU is generally 8 bits, but the measured current range is relatively large. Therefore, when the current is smaller, there will be a relatively large sampling error. The MCU collects the current less than 5A through the sampling resistor R0 on the battery side. With 8-bit sampling accuracy and a sampling range of -5A to +5A, the sampling accuracy is greatly improved. By calculating I3 and I1 through the resistor R0 and HCT sampling and comparing and calibrating them, an accurate current value can be obtained. During the charging of lithium batteries, poor small-current accuracy often causes battery overvoltage. When the lithium battery is close to full charge, only a very small current can cause the battery voltage to rise rapidly, resulting in overvoltage protection and affecting the battery life.

[0063] Embodiment 2

[0064] Embodiment 2 provides a control method for the DCDC bidirectional charge and discharge device provided in Embodiment 1. The control method includes:

[0065] Step S101. When the absolute value of the output current is greater than the preset current value, calculate the input current according to the preset transformer turns ratio.

[0066] Step S102. When the absolute value of the output current is not greater than the preset current value, start the first current detection module and detect the input current according to the first current detection module.

[0067] Among them, the control module monitors the absolute value of the output current in real time and compares it with the preset current threshold. When it is detected that the absolute value of the output current is greater than the preset current value, the control module does not start the first current detection module, but directly calculates the input 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 output current value is not greater than the preset current value, the control module starts the first current detection module to directly measure the actual current value of the input end. The first current detection module directly measures the actual current of the input end and feeds the measured current value back to the control module for real-time control and adjustment of the system.

[0068] The technical effect of this embodiment is as follows: under high-current conditions, the input current is calculated through the turns ratio, simplifying the detection process and reducing power consumption; while under low-current conditions, the first current detection module is directly used to measure the input current to 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 charge and discharge process.

[0069] As an implementation manner, the first current detection module includes a first switch module, a collection module, and a differential amplification module. Detecting the input end current according to the first current detection module includes:

[0070] Control the first switch module to conduct, collect the input end current through the collection module to form a voltage difference, obtain the voltage difference signal on the collection module through the differential amplification module, and amplify the voltage difference signal.

[0071] Among them, controlling the first switch module to conduct enables the first current detection module to start working. When the current flows through the collection module, the collection module will generate a voltage difference proportional to the input current. The two input ends of the differential amplification module are respectively connected to the endpoints of the collection module to receive the voltage difference signal. By amplifying the voltage difference, the differential amplification module makes the amplified voltage signal of the tiny input current change for subsequent processing modules to detect and analyze, and can maintain the position even in the low-current range. In addition, the amplified signal provides accurate feedback for the control module, improving the dynamic response ability of the system.

[0072] The technical effect of this implementation manner is as follows: this process realizes the accurate measurement of the input current through the cooperation of the first switch module, the collection module, and the differential amplification module. The current-voltage conversion of the collection module makes the signal more processable, the design of the differential amplification module ensures the anti-interference ability of the signal, and the amplification step further improves the accuracy and precision of the detection. Finally, this signal processing queue improves the stability and response speed of the system, and can reliably monitor and feedback the input end current in real time.

[0073] As an implementation manner, after detecting the input end current according to the first current detection module, it further includes:

[0074] When it is determined that there is an error in the transformer according to the detected input end current and the calculated input end current, compensate by controlling the first bidirectional inverter module or the second bidirectional inverter module.

[0075] Specifically, when the detected input current is higher than the calculated input end, it is determined that there is additional energy loss in the transformer, resulting in a reduction in transmission efficiency, and control the first bidirectional inverter module or the second bidirectional inverter module to increase the input current.

[0076] Among them, according to the deviation direction of the input terminal current (i.e., the detected current is greater than or less than the calculated current), the control module determines whether there is a loss in the transformer. If the detected input current is higher than the calculated current, it is determined that there is additional energy loss in the transformer, resulting in a decrease in 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 operating 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 magnitude and response speed of the output current to meet the compensation requirements. The adjustment of the second bidirectional inverter module is mainly based on the demand changes at the load end to help transmit the compensated power to the output end more efficiently. After the control module completes the preliminary compensation, it 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 indicates that the compensation is effective; if the difference still exists, the control module will further finely adjust the operating parameters of the two inverter modules.

[0077] The technical effect of this embodiment is that the control module increases or decreases the transmission power through the fine adjustment of the PWM duty cycle and switching frequency of the first bidirectional inverter module, and improves the response ability of the output end through the state optimization of the second bidirectional inverter module, thereby realizing the effective compensation of transformer losses. Finally, this 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 losses.

[0078] As an embodiment, 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;

[0079] A fault is determined based on the detected input terminal current and the calculated input terminal current. After that, it further includes:

[0080] Control the second switch module and the third switch module to conduct, so that the first light-emitting diode, the first photodiode, the second light-emitting diode, the second photodiode, and the divider start to work, and control 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.

[0081] Compensate by controlling the first bidirectional inverter module or the second bidirectional inverter module according to the ratio between the input current and the output current and the turns ratio of the transformer, including:

[0082] When the difference between the ratio between the input current and the output current and the turns ratio of the transformer is outside the error range, control the first bidirectional inverter module or the second bidirectional inverter module to perform compensation.

[0083] Among them, start the first light-emitting diode. The first light-emitting diode emits a light signal according to the magnitude of the input terminal current, and its light intensity is proportional to the input current. The first photodiode receives the light signal from the first light-emitting diode and converts it into a current signal, which is transmitted to the first input terminal of the divider. Start the second light-emitting diode. The second light-emitting diode emits a light signal according to the magnitude of the output terminal current, and its light intensity is proportional to the output current. The second photodiode receives the light signal from the second light-emitting diode and converts it into a current signal, which is transmitted to the second input terminal of the divider. The divider receives the current signals from the first photodiode and the second photodiode, which respectively represent the input current and the output current. 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 set threshold is ±5%), it is determined that there is energy loss or mismatch in the system. When the difference between the ratio and the turns ratio exceeds the preset threshold, the control module starts the compensation operation, and the specific method 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 the switching frequency of the first bidirectional inverter module to compensate for the energy loss. In some cases, the parameters of the second bidirectional inverter module (such as PWM or switching frequency) can also be adjusted to optimize the output power. 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.

[0084] The technical effect of this embodiment is that: by starting the opto-coupling module and the divider to monitor the states of the input and output currents, and comparing the ratio with the turns ratio of the transformer, it is determined whether compensation is required. When there is 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 the efficient transmission and stable operation of the system under various load conditions.

[0085] Furthermore, using light-emitting diodes and photodiodes can also detect temperature. The forward voltage change characteristics and luminous efficiency change of the LED are used to estimate the temperature. The specific implementation method is as follows:

[0086] The luminous efficiency and forward voltage characteristics of the light-emitting diode change with temperature, and these characteristics can be used as the basis for temperature detection. The photodiode can be used to receive the optical signal of the light-emitting diode, and then detect the temperature change. Connect the first light-emitting diode and the second light-emitting diode to a constant current source. When the temperature rises, the forward voltages of the first light-emitting diode and the second light-emitting diode will decrease. Use the control module to monitor the forward voltage changes 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 through the detected voltage change. When the detected temperature rises, perform temperature compensation by adjusting the input or output parameters of the transformer. For example, appropriately adjust the duty cycle or operating frequency of the inverter module to reduce the power loss caused by the temperature rise. When the temperature rises, reduce the current density or improve the heat dissipation efficiency to reduce the impact of high temperature on the circuit performance and maintain the efficient operation of the transformer.

[0087] In the DCDC bidirectional charge and discharge device, reducing the power loss caused by the temperature rise by appropriately adjusting the duty cycle or operating frequency of the inverter module can usually be achieved through the following control strategies and technologies: When the detected 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. Dynamically adjust the PWM duty cycle of the inverter module through the control 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 the 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. Design a hierarchical temperature control mechanism, and perform different degrees of duty cycle and frequency adjustment by setting multiple temperature thresholds. For example: Low temperature (below the safe temperature range): Maintain the normal frequency and duty cycle. Medium temperature (close to the upper limit temperature): Reduce a certain proportion of the duty cycle and slightly reduce the operating frequency at the same time. High temperature (exceeding the safe temperature upper limit): Further reduce the duty cycle or significantly lower the operating frequency to ensure system safety. The control module will automatically select different adjustment schemes according to the current temperature range to achieve hierarchical adjustment, so as to balance efficiency and safety.

[0088] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included within 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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