DC / DC converter control mode adaptive switching method based on voltage margin

Abstract

The invention relates to a DC / DC converter control mode self-adaptive switching method based on voltage margin. The method comprises the following steps: acquiring 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 latch-up protection mode according to the voltage difference between the acquired port voltage and the reference voltage. Wherein the DC / DC converter can adopt double-ring proportional-integral control, a control loop of the DC / DC converter comprises a control outer ring and a current control inner ring, and the DC / DC converter correspondingly works in a current source mode or a voltage source mode by switching the control outer ring into the current control outer ring or the voltage control outer ring. According to the invention, voltage control or current control can be adaptively carried out according to the fluctuation range of the DC bus voltage, the effect of the DC / DC converter in the AC / DC micro-grid can be maximized, the fault rate of the DC bus can be reduced, and the operation stability of the DC micro-grid and the power supply reliability of the DC load can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of low-voltage distribution networks, and in particular to a method for adaptively switching a DC / DC converter control mode based on voltage margin. Background Art

[0002] As an effective carrier of distributed power sources, microgrids can support large power grids and become one of the solutions for the large-scale development and utilization of renewable energy with their flexible operating modes and controllability. AC / DC hybrid microgrids combine the advantages of DC microgrids on the basis of AC microgrids and have outstanding advantages. Currently, more and more devices are connected to AC / DC microgrids. The DC bus serves as an interface for energy exchange between various distributed resources such as DC power supplies, energy storage systems, and DC loads. Its stability directly affects the stable operation of AC / DC microgrids. DC / DC converters have functions such as voltage regulation and power flow control and are an important part of AC / DC microgrids. Most existing technical solutions use complex hardware circuits to realize the automatic switching of DC / DC converters between voltage mode and current mode, which is not suitable for energy storage DC / DC in microgrids. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a DC / DC converter control mode adaptive switching method based on voltage margin, which can adaptively perform voltage control or current control according to the fluctuation range of 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 operating stability of the DC microgrid and the reliability of DC load power supply.

[0004] The present invention solves the technical problem by providing a method for adaptively switching the control mode of a DC / DC converter based on voltage margin. The DC / DC converter is a four-switch bidirectional buck-boost converter, comprising:

[0005] collecting the inductor current and port electrical quantities of the DC / DC converter in real time, wherein the port electrical quantities include port voltage and port current; Calculating a voltage difference between the port voltage and a reference voltage, and switching an operating mode of the DC / DC converter to a current source mode, a voltage source mode, or a lockout protection mode according to the voltage difference, wherein the reference voltage is a preset value; Determining a control outer loop according to the current operating mode, wherein the control outer loop is one of a current control outer loop and a voltage control outer loop, and calculating a difference between an electrical quantity corresponding to the port and a set target value as an 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 a dual-loop proportional-integral control is adopted to control the switching action of the DC / DC converter.

[0006] Furthermore, when the DC / DC converter operates in the current source mode: Setting the control outer loop of the DC / DC converter to a current control outer loop; Using the difference between the port current and the target current 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.

[0007] Furthermore, when the DC / DC converter operates in the voltage source mode: Setting the control outer loop of the DC / DC converter to a voltage control outer loop; Using the difference between the port voltage and the target voltage 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.

[0008] Furthermore, switching the operation mode of the DC / DC converter to a current source mode, a voltage source mode, or a lockout protection mode according to the voltage difference includes:

[0009] If the voltage difference is less than the first voltage deviation value and the duration exceeds a first set time, controlling the DC / DC converter to operate in the current source mode;

[0010] If the voltage difference is greater than the second voltage deviation value and less than the third voltage deviation value, and the duration exceeds a second set time, controlling the DC / DC converter to operate in the voltage source mode;

[0011] If the voltage difference is greater than the third voltage deviation value and lasts longer than a third set time, controlling the DC / DC converter to operate in the lockout protection mode;

[0012] The first voltage deviation value is smaller than the second voltage deviation value, the second voltage deviation value is smaller than the third voltage deviation value, and the first voltage deviation value, the second voltage deviation value, and the third voltage deviation value are all set values.

[0013] Furthermore, when the DC / DC converter operates in a voltage source mode, the sum or difference between the reference voltage and the second voltage deviation value is used as the target voltage.

[0014] Furthermore, if the port voltage is less than the reference voltage, the difference between the reference voltage and the second voltage deviation value is used as the target voltage; if the port voltage is greater than the reference voltage, the sum of the reference voltage and the second voltage deviation value is used as the target voltage.

[0015] Furthermore, one side of the DC / DC converter is connected to a DC bus, and the port voltage is a DC bus side voltage.

[0016] Furthermore, the four-switch bidirectional buck-boost converter includes four fully controlled switches and an inductor forming an H-bridge circuit structure, and capacitors are respectively connected in parallel to ports on both sides of the H-bridge circuit structure.

[0017] Beneficial effects

[0018] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art: the present invention collects 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 collected port voltage and the reference voltage, so that the DC / DC converter performs charge and discharge current control when the port voltage is stable, and automatically switches to voltage control when the port voltage fluctuates, thereby maintaining the port voltage stability; the present invention adopts a dual-loop proportional-integral control DC / DC converter and controls the outer loop to switch to a current control outer loop or a voltage control outer loop so that it operates in the current source mode or the voltage source mode respectively, without the need for complex circuit design, and can adaptively switch the operating mode according to the fluctuation range of the port voltage; the DC / DC converter is connected to the DC bus, and the method described in the present invention is used to control the DC / DC converter to perform charge and discharge current control when the DC bus voltage is stable, and automatically switch to voltage control when the DC bus fluctuates, which 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a circuit diagram of a DC / DC converter according to an embodiment of the present invention;

[0020] Figure 2 is a flow chart of an embodiment of the present invention;

[0021] Figure 3 It is a control block diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0022] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0023] An embodiment of the present invention relates to a method for adaptively switching a DC / DC converter control mode based on voltage margin, comprising:

[0024] Real-time acquisition of DC / DC converter port voltage;

[0025] The voltage difference between the collected port voltage and the reference voltage is calculated, and the operation mode of the DC / DC converter is switched to current source mode, voltage source mode or lockout protection mode according to the size of the voltage difference, where the reference voltage is a preset value.

[0026] More specifically, the DC / DC converter can adopt dual-loop proportional-integral control, and its control loop includes an outer control loop and an inner control loop. The inner control loop adopts a current control inner loop, and the outer control loop is switched to a current control outer loop or a voltage control outer loop to operate in current source mode or voltage source mode accordingly.

[0027] Users can connect one side of the DC / DC converter to the DC bus and the other side to the energy storage battery or DC power supply according to the on-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.

[0028] by Figure 1 This embodiment is further described by taking the four-switch bidirectional buck-boost circuit in FIG as an example. It should be noted that this embodiment is also applicable to other DC / DC converters including a buck circuit and a boost circuit, or multiplexed circuits thereof.

[0029] The DC / DC converter collects port voltage V, port current I, and inductor current data in real time .

[0030] The current source mode adopts dual-loop proportional integral control, including the current control outer loop and the current control inner loop. The preset target current The difference between the current sampling value I and the current sampling value I is used as the current control outer loop through proportional integral control. The output of the current control outer loop is proportional to the inductor current sampling value. The difference is controlled by proportional integral as the current control inner loop. The output of the current control inner loop is normalized to obtain the duty cycle d, which controls the switching action of the DC / DC converter.

[0031] The voltage source mode adopts proportional integral dual loop control, including voltage control outer loop and current control inner loop. The difference between the target voltage and the voltage sampling value V is used as the voltage control outer loop through proportional integral control. The output of the voltage control outer loop is proportional to the inductor current sampling value. The difference is controlled by proportional integral as the current control inner loop. The output of the current control inner loop is normalized to obtain the duty cycle d, which controls the switching action of the DC / DC converter.

[0032] Specific regulatory strategies such as Figure 2 As shown, set the reference voltage , the first voltage deviation value , the second voltage deviation value , the third voltage deviation value , first set duration , the second setting duration , the third setting duration .

[0033] When the voltage fluctuation range does not exceed , and lasts longer than , the DC / DC converter operates in current source mode, and the target current value is , the control outer loop switches to the current control outer loop; when the voltage fluctuation range exceeds But no more than , and lasts longer than , the DC / DC converter operates in voltage source mode, the control outer loop switches to voltage control outer loop, and the target voltage value is ; When the voltage fluctuation range exceeds But no more than , and lasts longer than , the DC / DC converter operates in voltage source mode, the control outer loop switches to voltage control outer loop, and the target voltage value is ; When the voltage fluctuation exceeds , and lasts longer than , DC / DC converter lockout protection.

[0034] A preferred embodiment of this embodiment 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 the DC bus, and switching between voltage source mode, current source mode and lockout protection is performed according to the fluctuation range of the DC bus voltage.

[0035] The operating modes of the DC / DC converter in different voltage ranges are shown in Table 1 below.

[0036] Table 1

[0037] When the voltage fluctuation range does not exceed , and lasts longer than , the DC / DC converter operates in current source mode, and the target current value is , the control outer loop switches to the current control outer loop; when the voltage fluctuation range exceeds But no more than , and lasts longer than , the DC / DC converter operates in voltage source mode, the control outer loop switches to voltage control outer loop, and the target voltage value is ; When the voltage fluctuation range exceeds But no more than , and lasts longer than , the DC / DC converter operates in voltage source mode, the control outer loop switches to voltage control outer loop, and the target voltage value is ; When the voltage fluctuation exceeds , and lasts longer than , DC / DC converter lockout protection.

[0038] in, is the DC bus voltage reference value, is the reference value of constant current charge and discharge of DC / DC converter, is the DC bus stable operation voltage threshold, The maximum voltage threshold allowed for equipment operation on the DC bus. The voltage threshold for safe operation of DC / DC converter ( ).

[0039] like Figure 3 As shown, the DC / DC converter collects the DC bus voltage V, current I, and inductor current data in real time. .

[0040] The current source mode adopts dual-loop proportional integral control, including the current control outer loop and the current control inner loop. The difference between the current sampling value I and the current sampling value I is used as the current control outer loop through proportional integral control. The output of the current control outer loop is proportional to the inductor current sampling value. The difference is controlled by proportional integral as the current control inner loop. The output of the current control inner loop is normalized to obtain the duty cycle d, which controls the switching action of the DC / DC converter.

[0041] The voltage source mode adopts proportional integral dual loop control, including voltage control outer loop and current control inner loop. The difference between the voltage sampling value V and the voltage sampling value V is used as the voltage control outer loop through proportional integral control. The output of the voltage control outer loop is proportional to the inductor current sampling value. The difference is controlled by proportional integral as the current control inner loop. The output of the current control inner loop is normalized to obtain the duty cycle d, which controls the switching action of the DC / DC converter.

Claims

1. A method for adaptively switching control modes 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: collecting the inductor current and port electrical quantities of the DC / DC converter in real time, wherein the port electrical quantities include port voltage and port current; Calculating a voltage difference between the port voltage and a reference voltage, and switching an operating mode of the DC / DC converter to a current source mode, a voltage source mode, or a lockout protection mode according to the voltage difference, wherein the reference voltage is a preset value; Determining a control outer loop according to the current operating mode, wherein the control outer loop is one of a current control outer loop and a voltage control outer loop, and calculating a difference between an electrical quantity corresponding to the port and a set target value as an 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 a dual-loop proportional-integral control is adopted to control the switching action of the DC / DC converter.

2. The method according to claim 1, characterized in that When the DC / DC converter operates in the current source mode: Setting the control outer loop of the DC / DC converter to a current control outer loop; Using the difference between the port current and the target current 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 operates in the voltage source mode: Setting the control outer loop of the DC / DC converter to a voltage control outer loop; Using the difference between the port voltage and the target voltage 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, wherein The step of switching the operation mode of the DC / DC converter to a current source mode, a voltage source mode, or a lockout protection mode according to the voltage difference comprises: If the voltage difference is less than the first voltage deviation value and the duration exceeds a first set time, controlling the DC / DC converter 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 a second set time, controlling the DC / DC converter to operate in the voltage source mode; If the voltage difference is greater than the third voltage deviation value and lasts longer than a third set time, controlling the DC / DC converter to operate in the lockout protection mode; The first voltage deviation value is smaller than the second voltage deviation value, the second voltage deviation value is smaller than the third voltage deviation value, and 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 a voltage source mode, the sum or difference between the reference voltage and the second voltage deviation value is used as the target voltage.

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

7. The method according to claim 1, characterized in that One side of the DC / DC converter is connected to a DC bus, and the port voltage is the DC bus side voltage.

8. 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, and capacitors are respectively connected in parallel to ports on both sides of the H-bridge circuit structure.

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