Flexible direct current converter valve circulation active control method and related device

Abstract

The invention discloses a flexible DC converter valve circulating current active control method and a related device, the circulating current of a flexible DC converter valve is controlled by a pre-designed peak value of a bridge arm current, a reference value of a circulating current controller does not need to be calculated in advance, and control can be accurately carried out through closed-loop control according to the pre-designed peak value of the bridge arm current; the added loop and calculation amount are small, engineering implementation is easy, and the problems that in an existing flexible direct-current converter valve bridge arm circulation control method, a reference value of a circulation controller is a pre-calculated value and cannot adapt to the scene that system parameters can deviate according to different operation working conditions, errors exist in a calculation result, and the reliability is poor are solved. And more computing resources are occupied.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of direct current transmission system, and in particular to a flexible direct current converter valve circulating current active control method and related device. BACKGROUND

[0002] In high voltage direct current engineering, the converter valve generally adopts the MMC (Modular Multilevel Converter) topology structure composed of full-bridge sub-modules and half-bridge sub-modules. When the MMC is in normal operation, the voltages of all sub-modules are required to be consistent for the safety of the sub-modules, and the corresponding sequencing unit in the MMC valve control sorts the sub-modules to keep the voltage stable, as shown in Figure 1 . Figure 1 The MMC topology structure is typical, which includes six bridge arms, each of which is composed of full-bridge sub-modules and half-bridge sub-modules in series, each sub-module is composed of switching devices and capacitors, and the charging and discharging directions of the capacitors can be controlled by different switching states to control the capacitor voltage.

[0003] There is circulating current in the flexible direct current converter valve bridge arm. The traditional circulating current control method is to extract the circulating current value to the dq axis and give a reference value of 0. According to the operation principle of the MMC, circulating current exists between the six bridge arms, and the circulating current value does not affect the power, voltage and current of the AC side output of the converter valve. Therefore, the existing research is to set the circulating current to a fixed amplitude and angle, and then realize different functions. However, the reference value of the existing flexible direct current converter valve bridge arm circulating current controller is pre-calculated, and the pre-calculated method has the defect that the system parameters will deviate according to different operating conditions, which will cause errors in the calculation results, and the occupied calculation resources are more. SUMMARY

[0004] The present application provides a flexible direct current converter valve circulating current active control method and related device, which is used to solve the technical problems in the existing flexible direct current converter valve bridge arm circulating current control method that the reference value of the circulating current controller is a pre-calculated value, which cannot adapt to the scene that the system parameters will deviate according to different operating conditions, the calculation results have errors, and the occupied calculation resources are more.

[0005] Therefore, the first aspect of the present application provides a flexible direct current converter valve circulating current active control method, comprising:

[0006] The three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible direct current converter valve are low-pass filtered respectively to obtain first bridge arm currents;

[0007] The first bridge arm currents and the bridge arm current reference values are input into a PI controller after a subtractor to obtain d-axis control reference values of the secondary circulating current;

[0008] Summing the three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter valve and taking 1 / 2 value, input into the abc / dq converter, the control angle of the abc / dq converter is obtained by processing the angle after voltage phase locking of the grid side and the angle after current phase locking of the grid side;

[0009] The d-axis component of the bridge arm circulating current output by the abc / dq converter and the d-axis control reference value of the secondary circulating current are input into a PI controller after passing through a subtractor, to obtain the d-axis control voltage of the secondary circulating current.

[0010] The q-axis component of the bridge arm circulating current output by the abc / dq converter and the q-axis control reference value of the secondary circulating current are input into a PI controller after passing through a subtractor, to obtain the q-axis control voltage of the secondary circulating current.

[0011] The d-axis control voltage of the secondary circulating current and the q-axis control voltage of the secondary circulating current are input into a dq / abc converter to obtain the three-phase control voltage of the secondary circulating current, and the control angle of the dq / abc converter is equal to the control angle of the abc / dq converter.

[0012] Optionally, the three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter valve are summed and 1 / 2 value is taken, and input into the abc / dq converter, and the following steps are further included:

[0013] The angle after voltage phase locking of the grid side and the angle after current phase locking of the grid side are subtracted;

[0014] If the subtraction result is greater than or equal to 0, the subtraction result is multiplied by a preset coefficient, and the result multiplied by the preset coefficient is subtracted from 2 times the angle after voltage phase locking of the grid side to obtain the control angle of the abc / dq converter;

[0015] If the subtraction result is less than 0, the subtraction result is added to 2 times the angle after voltage phase locking of the grid side, and then multiplied by the preset coefficient, and the result multiplied by the preset coefficient is subtracted from 2 times the angle after voltage phase locking of the grid side to obtain the control angle of the abc / dq converter.

[0016] Optionally, the bridge arm current reference value is:

[0017]

[0018] wherein, is the bridge arm current reference value, k is a coefficient, is the peak value of the current of the bridge arm at the moment.

[0019] Optionally, the preset coefficient is 2.

[0020] The second aspect of the present application provides a flexible DC converter valve circulating current active control device, comprising:

[0021] a low-pass filtering module configured to low-pass filter the three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter valve respectively to obtain first bridge arm currents;

[0022] a first calculation module configured to input the first bridge arm currents and a bridge arm current reference value into a PI controller after passing through a subtractor to obtain a d-axis control reference value of secondary circulating currents;

[0023] a second calculation module configured to sum the three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter valve and take a value of 1 / 2 to input into an abc / dq converter, a control angle of the abc / dq converter being obtained by processing a phase-locked angle of a grid-side voltage and a phase-locked angle of a grid-side current;

[0024] a third calculation module configured to input a d-axis component of bridge arm circulating currents output by the abc / dq converter and the d-axis control reference value of the secondary circulating currents into the PI controller after passing through the subtractor to obtain a d-axis control voltage of the secondary circulating currents;

[0025] a fourth calculation module configured to input a q-axis component of the bridge arm circulating currents output by the abc / dq converter and a q-axis control reference value of the secondary circulating currents into the PI controller after passing through the subtractor to obtain a q-axis control voltage of the secondary circulating currents;

[0026] a conversion module configured to input the d-axis control voltage of the secondary circulating currents and the q-axis control voltage of the secondary circulating currents into a dq / abc converter to obtain three-phase control voltages of the secondary circulating currents, a control angle of the dq / abc converter being equal to the control angle of the abc / dq converter.

[0027] Optionally, the method further comprises a coordinate transformation control angle calculation module, which is configured to:

[0028] subtract the phase-locked angle of the grid-side voltage from the phase-locked angle of the grid-side current;

[0029] if the subtraction result is greater than or equal to 0, multiply the subtraction result by a preset coefficient, subtract a result of multiplying the preset coefficient from twice the phase-locked angle of the grid-side voltage to obtain the control angle of the abc / dq converter;

[0030] if the subtraction result is less than 0, add 2 to the subtraction result, then multiply the result by the preset coefficient, and subtract a result of multiplying the preset coefficient from twice the phase-locked angle of the grid-side voltage to obtain the control angle of the abc / dq converter.

[0031] Optionally, the bridge arm current reference value is:

[0032]

[0033] wherein, is the bridge arm current reference value, k is a coefficient, is the current bridge arm current peak value.

[0034] Optionally, the preset coefficient is 2.

[0035] The third aspect of the present application provides a flexible DC converter valve circulating current active control device, the device comprises a processor and a memory:

[0036] The memory is used for storing program codes and transmitting the program codes to the processor;

[0037] The processor is used for executing the flexible DC converter valve circulating current active control method according to the instructions in the program codes.

[0038] The fourth aspect of the present application provides a computer readable storage medium, the computer readable storage medium is used for storing program codes, the program codes are used for executing the flexible DC converter valve circulating current active control method.

[0039] From the above technical solutions, the flexible DC converter valve circulating current active control method provided by the present application has the following advantages:

[0040] The flexible DC converter valve circulating current active control method provided by the present application does not need to calculate the reference value of the circulating current controller in advance, can control according to the peak value of the bridge arm current designed in advance through closed loop control, has less increased loop and calculation amount, is easy to realize in engineering, and solves the technical problems that the reference value of the circulating current controller in the existing flexible DC converter valve bridge arm circulating current control method is a precalculated value, cannot adapt to the scene that the system parameters will deviate according to different operating conditions, the calculation result has errors, and more calculation resources are occupied. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiment or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other related drawings according to these drawings without creating any creative labor.

[0042] Figure 1 is a typical MMC topological structure schematic diagram;

[0043] Figure 2 is a flowchart of a flexible DC converter valve circulating current active control method provided in an embodiment of the present application;

[0044] Figure 3A control block diagram of the flexible DC converter valve circulating current active control method provided in the embodiment of the present application;

[0045] Figure 4 A structure schematic diagram of the flexible DC converter valve circulating current active control device provided in the embodiment of the present application.

[0046] Figure 5 A structure schematic diagram of the flexible DC converter valve circulating current active control device provided in the embodiment of the present application. DETAILED DESCRIPTION

[0047] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0048] For the convenience of understanding, please refer to Figure 2 and Figure 3 The present application provides an embodiment of a flexible DC converter valve circulating current active control method, which comprises:

[0049] Step 101, the three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter valve are respectively low-pass filtered to obtain first bridge arm currents.

[0050] It should be noted that the three-phase upper bridge arm currents of the flexible DC converter valve are input to the low-pass filter, and the three-phase lower bridge arm currents of the flexible DC converter valve are input to the low-pass filter. In the rectification mode, the three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter valve take the minimum value, and in the inversion mode, the three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter valve take the maximum value. The low-pass filter outputs the first bridge arm currents .

[0051] Step 102, the first bridge arm currents and the bridge arm current reference values are input to the PI controller after passing through the subtractor to obtain the d-axis control reference value of the secondary circulating current.

[0052] It should be noted that the first bridge arm currents and the bridge arm current reference values are input to the PI controller after passing through the subtractor to obtain the d-axis control reference value of the secondary circulating current . The bridge arm current reference value is:

[0053] ​

[0054] wherein, is the bridge arm current reference value, k is a coefficient, is the current bridge arm current peak value. The bridge arm current peak value is related to the current active power, reactive power, valve side voltage and other information, which can be calculated quickly and in real time according to the prior art. The coefficient k is the expected proportion of the bridge arm current peak value. Through the method of circulating current injection, the bridge arm current can be reduced by about 10%~20%, therefore, the value range of the coefficient k is [0.8, 0.9].

[0055] Step 103, sum the three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter valve and take 1 / 2 value, input into the abc / dq converter, and the control angle of the abc / dq converter is obtained by processing the angle after the grid side voltage phase locking and the angle after the grid side current phase locking.

[0056] It should be noted that the three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter valve are summed and take 1 / 2 value, input into the abc / dq converter, to obtain the d-axis component of the bridge arm circulating current output by the abc / dq converter and the q-axis component of the bridge arm circulating current . The control angle of the traditional control loop of the abc / dq converter is obtained by phase locking the grid side voltage. In the embodiment of the present application, the control angle of the abc / dq converter is obtained by processing the angle after the grid side voltage phase locking and the angle after the grid side current phase locking . Specifically, please refer to Figure 3 , the specific obtaining process of the control angle of the abc / dq converter is as follows:

[0057] Subtract the angle after the grid side voltage phase locking from the angle after the grid side current phase locking ;

[0058] If the subtraction result is greater than or equal to 0, multiply the subtraction result by a preset coefficient, subtract the result multiplied by the preset coefficient from twice the angle after the grid side voltage phase locking , to obtain the control angle of the abc / dq converter ;

[0059] If the subtraction result is less than 0, add 2 to the subtraction result and then multiply the result by the preset coefficient, subtract the result multiplied by the preset coefficient from twice the angle after the grid side voltage phase locking , to obtain the control angle of the abc / dq converter .

[0060] The preset coefficient is selected as 2.

[0061] In step 104, the d-axis component of the bridge arm circulating current output by the abc / dq converter and the d-axis control reference value of the secondary circulating current are input into a PI controller through a subtractor to obtain the d-axis control voltage of the secondary circulating current.

[0062] It should be noted that the d-axis component of the bridge arm circulating current output by the abc / dq converter and the d-axis control reference value of the secondary circulating current are input into a PI controller through a subtractor to obtain the d-axis control voltage of the secondary circulating current output by the PI controller .

[0063] In step 105, the q-axis component of the bridge arm circulating current output by the abc / dq converter and the q-axis control reference value of the secondary circulating current are input into a PI controller through a subtractor to obtain the q-axis control voltage of the secondary circulating current.

[0064] It should be noted that the q-axis component of the bridge arm circulating current output by the abc / dq converter and the q-axis control reference value of the secondary circulating current are input into a PI controller through a subtractor to obtain the q-axis control voltage of the secondary circulating current . The q-axis control reference value of the secondary circulating current is 0.

[0065] In step 106, the d-axis control voltage of the secondary circulating current and the q-axis control voltage of the secondary circulating current are input into a dq / abc converter to obtain a three-phase control voltage of the secondary circulating current, and the control angle of the dq / abc converter is equal to the control angle of the abc / dq converter.

[0066] It should be noted that the d-axis control voltage of the secondary circulating current and the q-axis control voltage of the secondary circulating current are input into a dq / abc converter to obtain a three-phase control voltage of the secondary circulating current , and the control angle of the dq / abc converter is equal to the control angle of the abc / dq converter.

[0067] The flexible DC converter valve circulating active control method provided by the application does not need to calculate the reference value of the circulating controller in advance, can control the peak value of the bridge arm current designed in advance through closed-loop control, has small additional loop and calculation amount, is easy to implement in engineering, and solves the technical problems that the reference value of the circulating controller in the existing flexible DC converter valve bridge arm circulating control method is a pre-calculated value, cannot adapt to the scene where the system parameters deviate according to different operating conditions, the calculation result has errors, and a large amount of calculation resources are occupied.

[0068] For ease of understanding, please refer to Figure 4 An embodiment of a flexible DC converter valve circulating current active control device is provided in the present application, comprising:

[0069] A low-pass filtering module is configured to low-pass filter the three-phase upper bridge arm current and the three-phase lower bridge arm current of the flexible DC converter valve respectively to obtain a first bridge arm current;

[0070] A first calculation module is configured to input the first bridge arm current and a bridge arm current reference value into a PI controller after passing through a subtractor to obtain a d-axis control reference value of secondary circulating current;

[0071] A second calculation module is configured to sum the three-phase upper bridge arm current and the three-phase lower bridge arm current of the flexible DC converter valve and take 1 / 2 value to input into an abc / dq converter, and the control angle of the abc / dq converter is obtained by processing the angle after phase locking of the grid-side voltage and the angle after phase locking of the grid-side current;

[0072] A third calculation module is configured to input the d-axis component of the bridge arm circulating current output by the abc / dq converter and the d-axis control reference value of the secondary circulating current into a PI controller after passing through a subtractor to obtain a d-axis control voltage of the secondary circulating current;

[0073] A fourth calculation module is configured to input the q-axis component of the bridge arm circulating current output by the abc / dq converter and the q-axis control reference value of the secondary circulating current into a PI controller after passing through a subtractor to obtain a q-axis control voltage of the secondary circulating current;

[0074] A conversion module is configured to input the d-axis control voltage of the secondary circulating current and the q-axis control voltage of the secondary circulating current into a dq / abc converter to obtain a three-phase control voltage of the secondary circulating current, and the control angle of the dq / abc converter is equal to the control angle of the abc / dq converter.

[0075] In an embodiment, it further comprises a coordinate transformation control angle calculation module, which is configured to:

[0076] Subtract the angle after phase locking of the grid-side voltage from the angle after phase locking of the grid-side current;

[0077] If the subtraction result is greater than or equal to 0, multiply the subtraction result by a preset coefficient, subtract the result multiplied by the preset coefficient from 2 times the angle after phase locking of the grid-side voltage to obtain the control angle of the abc / dq converter;

[0078] If the subtraction result is less than 0, add 2 to the subtraction result, and then multiply the result by the preset coefficient, and subtract the result multiplied by the preset coefficient from 2 times the angle after phase locking of the grid-side voltage to obtain the control angle of the abc / dq converter.

[0079] In one embodiment, the bridge arm current reference value is:

[0080]

[0081] wherein, is the bridge arm current reference value, k is a coefficient, is the current bridge arm current peak value.

[0082] In one embodiment, the coefficient k is in the range of [0.8, 0.9].

[0083] In one embodiment, the q-axis control reference value of the secondary circulating current is 0.

[0084] For ease of understanding, please refer to Figure 5 An embodiment of a flexible DC converter valve circulating current active control device is provided in the present application, and the device comprises a processor and a memory:

[0085] The memory is used to store program code and transmit the program code to the processor;

[0086] The processor is used to execute any one of the embodiments of the flexible DC converter valve circulating current active control method according to the instructions in the program code.

[0087] The embodiments of the present application also provide a computer readable storage medium for storing program code, which is used to execute any one of the embodiments of the flexible DC converter valve circulating current active control method.

[0088] The flexible DC converter valve circulating current active control device, equipment and computer readable storage medium provided in the present application are all used to execute the flexible DC converter valve circulating current active control method provided in the present application, and the principles and the technical effects obtained are the same as those of the flexible DC converter valve circulating current active control method provided in the present application, which will not be described here.

[0089] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the above-described system, device and unit can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0090] The above-described embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalent replacements; 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 embodiments of the present application.

Claims

1. A method of active control of circulating currents in a flexible DC converter valve, characterized in that The method comprises the following steps: The three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter are low-pass filtered respectively to obtain first bridge arm currents; The first bridge arm currents and bridge arm current reference values are input into a PI controller through a subtractor to obtain d-axis control reference values of secondary circulating currents; The three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter are summed and halved to be input into an abc / dq converter, and a control angle of the abc / dq converter is obtained by processing a phase angle of a grid-side voltage after phase locking and a phase angle of a grid-side current after phase locking; The d-axis component of the bridge arm circulating current output by the abc / dq converter and the d-axis control reference value of the secondary circulating current are input into a PI controller through a subtractor to obtain a d-axis control voltage of the secondary circulating current; The q-axis component of the bridge arm circulating current output by the abc / dq converter and the q-axis control reference value of the secondary circulating current are input into a PI controller through a subtractor to obtain a q-axis control voltage of the secondary circulating current; The d-axis control voltage of the secondary circulating current and the q-axis control voltage of the secondary circulating current are input into a dq / abc converter to obtain three-phase control voltages of the secondary circulating current, and a control angle of the dq / abc converter is equal to the control angle of the abc / dq converter.

2. The method of claim 1, wherein, The three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter are summed and halved to be input into an abc / dq converter, and the method further comprises the following steps: The phase angle of the grid-side voltage after phase locking and the phase angle of the grid-side current after phase locking are subtracted; If the subtraction result is greater than or equal to 0, the subtraction result is multiplied by a preset coefficient, and the result of multiplying the preset coefficient is subtracted from 2 times the phase angle of the grid-side voltage after phase locking to obtain the control angle of the abc / dq converter; If the subtraction result is less than 0, then add 2 to the subtraction result After multiplying by the preset coefficient, the result of multiplying by the preset coefficient is subtracted from the angle locked with the 2 times of the grid voltage to obtain the control angle of the abc / dq converter.

3. The method of claim 1, wherein, The bridge arm current reference value is: wherein, is the bridge arm current reference value, k is a coefficient, is the current peak value of the bridge arm.

4. The method of claim 2, wherein, The preset coefficient is 2.

5. A flexible HVDC converter valve circulating current active control device, characterized by, The method comprises the following steps: A low-pass filtering module is configured to low-pass filter the three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter respectively to obtain first bridge arm currents; A first calculation module is configured to input the first bridge arm currents and bridge arm current reference values into a PI controller through a subtractor to obtain d-axis control reference values of secondary circulating currents; A second calculation module is configured to sum the three-phase upper bridge arm currents and the three-phase lower bridge arm currents of the flexible DC converter and halve the sum to be input into an abc / dq converter, and a control angle of the abc / dq converter is obtained by processing a phase angle of a grid-side voltage after phase locking and a phase angle of a grid-side current after phase locking; A third calculation module is configured to input the d-axis component of the bridge arm circulating current output by the abc / dq converter and the d-axis control reference value of the secondary circulating current into a PI controller through a subtractor to obtain a d-axis control voltage of the secondary circulating current; A fourth calculation module is configured to input the q-axis component of the bridge arm circulating current output by the abc / dq converter and the q-axis control reference value of the secondary circulating current into a PI controller through a subtractor to obtain a q-axis control voltage of the secondary circulating current; A conversion module is configured to input the d-axis control voltage of the secondary circulating current and the q-axis control voltage of the secondary circulating current into a dq / abc converter to obtain three-phase control voltages of the secondary circulating current, and a control angle of the dq / abc converter is equal to the control angle of the abc / dq converter.

6. The flexible HVDC valve circulating current active control device of claim 5, wherein, The application also comprises a coordinate transformation control angle calculation module, which is used for: Subtracting the phase-locked angle of the grid-side voltage from the phase-locked angle of the grid-side current; If the subtraction result is greater than or equal to 0, multiplying the subtraction result by a preset coefficient, subtracting the result of multiplying the preset coefficient from 2 times the phase-locked angle of the grid-side voltage to obtain the control angle of the abc / dq converter; If the subtraction result is less than 0, then add 2 to the subtraction result After multiplying by the preset coefficient, the result of multiplying by the preset coefficient is subtracted from the angle locked with the 2 times of the grid voltage to obtain the control angle of the abc / dq converter.

7. The flexible HVDC valve circulating current active control device of claim 6, wherein, The bridge arm current reference value is: wherein, is the bridge arm current reference value, k is a coefficient, is the current peak value of the bridge arm.

8. The flexible HVU ring current active control device of claim 2, wherein, The preset coefficient is 2.

9. A flexible HVDC converter valve circulating current active control device, characterized in that, The device comprises a processor and a memory: The memory is used for storing program codes and transmitting the program codes to the processor; The processor is used for executing the method according to the instructions in the program codes.

10. A computer-readable storage medium, characterized in that, The computer readable storage medium is used for storing program codes, which are used for executing the method.

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