Adaptive switching method of dc / dc converter control mode based on voltage margin

Abstract

The application relates to a voltage margin-based DC / DC converter control mode adaptive switching method, which comprises the following steps: collecting the port voltage of a DC / DC converter in real time; and switching the operation mode of the DC / DC converter into a current source mode, a voltage source mode or a lockout protection mode according to the voltage difference between the collected port voltage and a reference voltage. Wherein, the DC / DC converter can adopt a double-loop proportional integral control, the control loop of which comprises a control outer loop and a current control inner loop, and the control outer loop is switched into a current control outer loop or a voltage control outer loop to correspond to working in the current source mode or the voltage source mode. The application can adaptively perform voltage control or current control according to the fluctuation range of the DC bus voltage, maximally exert the role of the DC / DC converter in an AC / DC microgrid, reduce the DC bus failure rate, and improve the operation stability of the DC microgrid and the reliability of DC load power supply.

Description

Technical Field

[0001] This invention relates to the field of low-voltage power distribution network technology, and in particular to an adaptive switching method for DC / DC converter control modes based on voltage margin. Background Technology

[0002] Microgrids, as an effective carrier of distributed power sources, can support the main power grid and have become one of the solutions for large-scale development and utilization of renewable energy due to their flexible operation modes and controllability. AC / DC hybrid microgrids, based on AC microgrids, combine the advantages of DC microgrids and have significant advantages. Currently, more and more devices are connected to AC / DC microgrids. The DC bus, as the interface for energy exchange among various DC power sources, energy storage systems, DC loads, and other distributed resources, directly affects the stable operation of the AC / DC microgrid. DC / DC converters, with functions such as voltage regulation and power flow control, are a crucial component of AC / DC microgrids. Existing technical solutions mostly use complex hardware circuits to achieve automatic switching between voltage and current modes in DC / DC converters, which are unsuitable for energy storage DC / DC converters in microgrids. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an adaptive switching method for DC / DC converter control mode based on voltage margin, which can adaptively perform voltage control or current control according to the fluctuation range of DC bus voltage, maximize the role of DC / DC converter in AC / DC microgrid, reduce DC bus failure rate, and improve the operational stability of DC microgrid and the reliability of DC load power supply.

[0004] The technical solution adopted by this invention to solve its technical problem is: to provide an adaptive switching method for the control mode of a DC / DC converter based on voltage margin, wherein the DC / DC converter is a four-switch bidirectional buck-boost converter, comprising:

[0005] The inductor current and port electrical quantities of the DC / DC converter are collected in real time, including port voltage and port current.

[0006] Calculate the voltage difference between the port voltage and the reference voltage, and switch the operating mode of the DC / DC converter to current source mode, voltage source mode or lockout protection mode according to the magnitude of the voltage difference. The reference voltage is a preset value.

[0007] The control outer loop is determined based on the current operating mode. The control outer loop is either a current control outer loop or a voltage control outer loop. The difference between the corresponding port electrical quantity and the set target value is calculated as the input of the control outer loop.

[0008] The difference between the output of the outer control loop and the inductor current is used as the input of the inner current control loop, and the switching action of the DC / DC converter is controlled by a dual-loop proportional-integral control.

[0009] Furthermore, when the DC / DC converter operates in the current source mode:

[0010] The control outer loop of the DC / DC converter is set as a current control outer loop;

[0011] The difference between the port current and the target current is used as the input of the current control outer loop;

[0012] The switching action of the DC / DC converter is controlled based on the duty cycle obtained by normalizing the output of the current control inner loop.

[0013] Furthermore, when the DC / DC converter operates in the voltage source mode:

[0014] The control outer loop of the DC / DC converter is set as a voltage control outer loop;

[0015] The difference between the port voltage and the target voltage is used as the input of the voltage control outer loop;

[0016] The switching action of the DC / DC converter is controlled based on the duty cycle obtained by normalizing the output of the current control inner loop.

[0017] Furthermore, the step of switching the operating mode of the DC / DC converter to current source mode, voltage source mode, or lockout protection mode based on the magnitude of the voltage difference includes:

[0018] If the voltage difference is less than the first voltage deviation value and the duration exceeds the first set duration, then the DC / DC converter is controlled to operate in the current source mode.

[0019] If the voltage difference is greater than the second voltage deviation value and less than the third voltage deviation value, and the duration exceeds the second set duration, then the DC / DC converter is controlled to operate in the voltage source mode.

[0020] If the voltage difference is greater than the third voltage deviation value and the duration exceeds the third set duration, then the DC / DC converter is controlled to operate in the lockout protection mode.

[0021] The first voltage deviation is less than the second voltage deviation, the second voltage deviation is less than the third voltage deviation, and the first voltage deviation, the second voltage deviation, and the third voltage deviation are all set values.

[0022] Furthermore, when the DC / DC converter operates in voltage source mode, the target voltage is the sum or difference between the reference voltage and the deviation value of the second voltage.

[0023] Furthermore, if the port voltage is less than the reference voltage, the target voltage is the difference between the reference voltage and the second voltage deviation value; if the port voltage is greater than the reference voltage, the target voltage is the sum of the reference voltage and the second voltage deviation value.

[0024] Furthermore, one side of the DC / DC converter is connected to a DC bus, and the port voltage is the DC bus side voltage.

[0025] Furthermore, the four-switch bidirectional buck-boost converter includes four fully controlled switches and an inductor forming an H-bridge circuit structure, with capacitors connected in parallel to each of the two ports of the H-bridge circuit structure.

[0026] Beneficial effects

[0027] By adopting the above-mentioned technical solution, this invention has the following advantages and positive effects compared with the prior art: This invention acquires the port voltage of the DC / DC converter in real time and switches the corresponding operating mode of the DC / DC converter according to the voltage difference between the acquired port voltage and the reference voltage. This allows the DC / DC converter to perform charging and discharging current control when the port voltage is stable, and automatically switches to voltage control when the port voltage fluctuates, thereby maintaining port voltage stability. This invention uses a dual-loop proportional-integral control DC / DC converter and controls the outer loop to switch between current control and voltage control to operate in the corresponding current source mode or voltage source mode. It can adaptively switch operating modes according to the fluctuation range of the port voltage without complex circuit design. By connecting the DC / DC converter to the DC bus and using the method described in this invention to control the DC / DC converter to perform charging and discharging current control when the DC bus voltage is stable, and automatically switching to voltage control when the DC bus voltage fluctuates, it can stabilize the DC bus voltage, maximize the role of the DC / DC converter in the AC / DC microgrid, reduce the DC bus failure rate, and improve the operational stability of the DC microgrid and the reliability of DC load power supply. Attached Figure Description

[0028] Figure 1 This is a circuit diagram of a DC / DC converter according to an embodiment of the present invention;

[0029] Figure 2 This is a flowchart of an embodiment of the present invention;

[0030] Figure 3 This is a control block diagram of an embodiment of the present invention. Detailed Implementation

[0031] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0032] The embodiments of the present invention relate to an adaptive switching method for control modes of a DC / DC converter based on voltage margin, comprising:

[0033] Real-time acquisition of port voltages of the DC / DC converter;

[0034] The voltage difference between the acquired port voltage and the reference voltage is calculated, and the operating mode of the DC / DC converter is switched to current source mode, voltage source mode or lockout protection mode according to the magnitude of the voltage difference, where the reference voltage is a preset value.

[0035] More specifically, the DC / DC converter can adopt dual-loop proportional-integral control, which includes an outer control loop and an inner control loop. The inner control loop adopts a current control loop, and the outer control loop can be switched to either a current control loop or a voltage control loop to operate in the current source mode or voltage source mode respectively.

[0036] Users can connect one side of the DC / DC converter to the DC bus and the other side to an energy storage battery or DC power supply, depending on the site conditions. The DC / DC converter detects and controls the voltage on the side connected to the DC bus and adaptively switches the operating mode according to the detected DC bus voltage.

[0037] by Figure 1 This embodiment will be further explained using a four-switch bidirectional buck-boost circuit as an example. It should be noted that this embodiment is also applicable to other DC / DC converters, including buck circuits, boost circuits, or their multiplexing circuits.

[0038] The DC / DC converter collects port voltage V, port current I, and inductor current data in real time. .

[0039] The current source mode employs dual-loop proportional-integral control, consisting of an outer current control loop and an inner current control loop, with a preset target current. The difference between the current sample value I and the current sample value is used as the proportional-integral control (PIC) outer loop for current control. The output of the current control outer loop is proportional to the inductor current sample value. The difference is used as the inner loop of current control through proportional-integral control. The output of the inner loop of current control is normalized to obtain the duty cycle d, which controls the switching action of the DC / DC converter.

[0040] The voltage source mode employs a proportional-integral dual-loop control, consisting of an outer voltage control loop and an inner current control loop. The difference between the target voltage and the voltage sample value V is used as the outer voltage control loop via proportional-integral control. The output of the outer voltage control loop is compared with the inductor current sample value. The difference is used as the inner loop of current control through proportional-integral control. The output of the inner loop of current control is normalized to obtain the duty cycle d, which controls the switching action of the DC / DC converter.

[0041] Specific control strategies include Figure 2 As shown, the reference voltages are set respectively. First voltage deviation value Second voltage deviation value Third voltage deviation value First set duration Second set duration The third setting is the duration. .

[0042] When the detected voltage fluctuation range does not exceed And the duration exceeds The DC / DC converter operates in current source mode, with a target current value of The outer control loop switches to a current control outer loop; when the voltage fluctuation range exceeds... But not exceeding And the duration exceeds The DC / DC converter operates in voltage source mode, and the control outer loop switches to voltage control outer loop, with the target voltage value being... When the voltage fluctuates downwards beyond a certain range... But not exceeding And the duration exceeds The DC / DC converter operates in voltage source mode, and the control outer loop switches to voltage control outer loop, with the target voltage value being... When voltage fluctuations exceed And the duration exceeds DC / DC converter lockout protection.

[0043] A preferred embodiment of this implementation is a voltage / current control adaptive switching method for a DC / DC converter based on voltage margin. One side of the DC / DC converter is connected to a DC bus, and the switching between voltage source mode, current source mode, and blocking protection is performed according to the fluctuation range of the DC bus voltage.

[0044] The operating modes of the DC / DC converter under different voltage ranges are shown in Table 1 below.

[0045] Table 1

[0046]

[0047] When the detected voltage fluctuation range does not exceed And the duration exceeds The DC / DC converter operates in current source mode, with a target current value of The outer control loop switches to a current control outer loop; when the voltage fluctuation range exceeds... But not exceeding And the duration exceeds The DC / DC converter operates in voltage source mode, and the control outer loop switches to voltage control outer loop, with the target voltage value being... When the voltage fluctuates downwards beyond a certain range... But not exceeding And the duration exceeds The DC / DC converter operates in voltage source mode, and the control outer loop switches to voltage control outer loop, with the target voltage value being... When voltage fluctuations exceed And the duration exceeds DC / DC converter lockout protection.

[0048] in, This is the reference value for the DC bus voltage. This is the constant current charging and discharging reference value for the DC / DC converter. The threshold voltage for stable operation of the DC bus. The maximum permissible voltage threshold for equipment operation on the DC bus. The safe operating voltage threshold for DC / DC converters ( ).

[0049] like Figure 3 As shown, the DC / DC converter acquires real-time data on the DC bus voltage V, current I, and inductor current. .

[0050] The current source mode employs dual-loop proportional-integral control, consisting of an outer current control loop and an inner current control loop. Current preset value. The difference between the current sample value I and the current sample value is used as the proportional-integral control (PIC) outer loop for current control. The output of the current control outer loop is proportional to the inductor current sample value. The difference is used as the inner loop of current control through proportional-integral control. The output of the inner loop of current control is normalized to obtain the duty cycle d, which controls the switching action of the DC / DC converter.

[0051] The voltage source mode employs a proportional-integral dual-loop control, consisting of an outer voltage control loop and an inner current control loop. (Voltage preset value) The difference between the voltage sample value V and the voltage input is used as the voltage control outer loop via proportional-integral control. The output of the voltage control outer loop is related to the inductor current sample value. The difference is used as the inner loop of current control through proportional-integral control. The output of the inner loop of current control is normalized to obtain the duty cycle d, which controls the switching action of the DC / DC converter.

Claims

1. An adaptive switching method for control mode of a DC / DC converter based on voltage margin, wherein the DC / DC converter is a four-switch bidirectional buck-boost converter, characterized in that, include: The inductor current and port electrical quantities on the DC bus side of the DC / DC converter are collected in real time, including port voltage and port current. Calculate the voltage difference between the port voltage and the reference voltage, where the reference voltage is a preset value; The operating mode of the DC / DC converter is switched to current source mode, voltage source mode or lockout protection mode according to the magnitude of the voltage difference: if the voltage difference is less than the first voltage deviation value, the DC / DC converter is controlled to operate in the current source mode. If the voltage difference is greater than the second voltage deviation value and less than the third voltage deviation value, the DC / DC converter is controlled to operate in the voltage source mode; if the voltage difference is greater than the third voltage deviation value, the DC / DC converter is controlled to operate in the lockout protection mode. The first voltage deviation is less than the second voltage deviation, and the second voltage deviation is less than the third voltage deviation; The control outer loop is determined based on the current operating mode. The control outer loop is either a current control outer loop or a voltage control outer loop. The difference between the corresponding port electrical quantity and the set target value is calculated as the input of the control outer loop. The difference between the output of the outer control loop and the inductor current is used as the input of the inner current control loop, and the switching action of the DC / DC converter is controlled by a dual-loop proportional-integral control.

2. The method according to claim 1, characterized in that, When the DC / DC converter is operating in the current source mode: the control outer loop of the DC / DC converter is set as the current control outer loop; the difference between the port current and the target current is used as the input of the current control outer loop; The switching action of the DC / DC converter is controlled based on the duty cycle obtained by normalizing the output of the current control inner loop.

3. The method according to claim 1, characterized in that, When the DC / DC converter is operating in the voltage source mode: the control outer loop of the DC / DC converter is set as the voltage control outer loop; the difference between the port voltage and the target voltage is used as the input of the voltage control outer loop; The switching action of the DC / DC converter is controlled based on the duty cycle obtained by normalizing the output of the current control inner loop.

4. The method according to claim 1, characterized in that, The step of switching the operating mode of the DC / DC converter to current source mode, voltage source mode, or lockout protection mode based on the magnitude of the voltage difference includes: If the voltage difference is less than the first voltage deviation value and the duration exceeds the first set duration, then the DC / DC converter is controlled to operate in the current source mode. If the voltage difference is greater than the second voltage deviation value and less than the third voltage deviation value, and the duration exceeds the second set duration, then the DC / DC converter is controlled to operate in the voltage source mode. If the voltage difference is greater than the third voltage deviation value and the duration exceeds the third set duration, then the DC / DC converter is controlled to operate in the lockout protection mode. The first voltage deviation value, the second voltage deviation value, and the third voltage deviation value are all set values.

5. The method according to claim 4, characterized in that, When the DC / DC converter operates in voltage source mode, the target voltage is the sum or difference between the reference voltage and the deviation value of the second voltage.

6. The method according to claim 5, characterized in that, If the port voltage is less than the reference voltage, the target voltage is the difference between the reference voltage and the second voltage deviation value; if the port voltage is greater than the reference voltage, the target voltage is the sum of the reference voltage and the second voltage deviation value.

7. The method according to claim 1, characterized in that, The four-switch bidirectional buck-boost converter includes four fully controlled switches and an inductor forming an H-bridge circuit structure, with capacitors connected in parallel to the ports on both sides of the H-bridge circuit structure.

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