A DC voltage measurement abnormality determination device, flexible DC system and control method

Abstract

The present invention discloses a DC voltage measurement anomaly discrimination device, a flexible DC system, and a control method, wherein the device includes: an electrical quantity acquisition module that obtains electrical quantity signals of the flexible DC system and sends digital signals obtained after digital-to-analog conversion of the electrical quantity signals to an algorithm control module, wherein the electrical quantity signals include: grid-side voltage, grid-side current, valve-side current, DC voltage, and the maximum voltage of the converter phase submodule; the algorithm control module receives the digital signals, performs a judgment operation on the DC voltage, and when the DC voltage value is abnormal, replaces the DC voltage with the maximum voltage of the converter phase submodule to perform closed-loop control of the inner loop current of the flexible DC system. By quickly judging the DC voltage abnormality identification signal when the DC voltage is abnormal, the DC voltage closed-loop control quantity DC voltage is quickly switched to the submodule voltage, and the DC voltage measurement anomaly discrimination device is simultaneously started to switch, thereby ensuring the normal and stable operation of the flexible DC system.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible direct current system detection, and in particular to a direct current voltage measurement abnormality determination device, a flexible direct current system and a control method. Background Art

[0002] The voltage source converter-high voltage direct current (VSC-HVDC) system based on voltage source converters has the following advantages: no need for reactive power compensation, no commutation failure problem, can power passive systems, can independently adjust active power and reactive power, has low harmonic levels, and is suitable for building multi-terminal DC systems. With the rapid development of clean energy generation technologies represented by wind power generation and solar power generation, VSC-HVDC has been widely used as a new transmission technology in current practical projects.

[0003] In domestic engineering applications, VSC-HVDC systems usually adopt a dual closed-loop control strategy of "outer loop power + inner loop current", in which the outer loop power closed-loop control can be divided into active power and reactive power closed-loop control. Currently, the flexible DC projects that have been put into operation in China include two-terminal long-distance power transmission, back-to-back networking, multi-terminal flexible DC power transmission, multi-terminal flexible DC grid, hybrid multi-terminal power transmission and other transmission methods. However, no matter which power transmission method is used, one end must adopt DC voltage closed control as active power closed-loop control to ensure the stability of the DC voltage of the entire flexible DC system. Abnormal DC voltage measurement directly determines the quality of the DC voltage closed-loop control link of the VSC-HVDC system, affecting the stability of the DC voltage of the entire flexible DC system. Therefore, the judgment and control method of DC voltage measurement abnormality is very important. For example Figure 1 The positive and negative DC voltage Ud_ pos , Ud_ neg Abnormal data collection directly affects the output results of the DC voltage closed-loop control, resulting in abnormal calculation of the inner-loop current reference value, and the flexible DC system may eventually be forced to shut down. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide a DC voltage measurement abnormality judgment device, a flexible DC system and a control method. By quickly judging the DC voltage abnormality identification signal when the DC voltage is abnormal, the DC voltage closed-loop control quantity DC voltage is quickly switched to the sub-module voltage, thereby ensuring the normal and stable operation of the flexible DC system and improving the stability and reliability of the flexible DC system.

[0005] To solve the above technical problems, a first aspect of an embodiment of the present invention provides a device for determining abnormality in DC voltage measurement, comprising: an electrical quantity acquisition module and an algorithm control module;

[0006] The electrical quantity acquisition module acquires electrical quantity signals of the flexible DC system and sends digital signals obtained by digital-to-analog conversion of the electrical quantity signals to the algorithm control module, wherein the electrical quantity signals include: grid-side voltage, grid-side current, valve-side current, DC voltage, and maximum voltage of the converter phase submodule;

[0007] The algorithm control module receives the digital signal, performs a judgment operation on the DC voltage, and replaces the DC voltage with the maximum voltage of the converter phase submodule when the DC voltage value is abnormal, so as to perform closed-loop control of the inner loop current of the flexible DC system.

[0008] Furthermore, the electrical quantity acquisition module includes:

[0009] a dielectric acquisition unit for acquiring the grid-side voltage, grid-side current, and valve-side current of the flexible DC system;

[0010] An optical medium acquisition unit, which collects the DC voltage of the flexible DC system and the average voltage of the converter phase submodule;

[0011] A digital-to-analog conversion unit receives the electrical quantity signals collected by the dielectric acquisition unit and the optical medium acquisition unit respectively, obtains the maximum voltage of the converter phase submodule based on the average voltage of the converter phase submodule, converts the electrical quantity signal into a digital signal and sends it to the algorithm control module.

[0012] Furthermore, the algorithm control module includes: an electrical quantity calculation unit communicating via a backplane bus, a DC voltage measurement abnormality determination unit, an outer power closed-loop control unit, and an inner current closed-loop control unit;

[0013] The electrical quantity calculation unit receives the digital signal and performs per-unit calculation on it, calculates the voltage amplitude and grid frequency based on the grid-side voltage, calculates the active power and reactive power based on the grid-side voltage and the grid-side current, and sends them to the DC voltage measurement abnormality determination unit, the outer power closed-loop control unit, and the inner current closed-loop control unit, and calculates the DC voltage based on the positive and negative DC voltages;

[0014] The DC voltage measurement abnormality determination unit performs a judgment operation on the DC voltage and sends an abnormality identification signal to the inner current closed-loop control module and the algorithm control device switching module when the DC voltage value is abnormal;

[0015] The outer power closed-loop control unit obtains the inner current closed-loop control reference value required by the inner current closed-loop control unit after selecting the active power category and the reactive power category;

[0016] The inner current closed-loop control unit obtains the d-axis component and q-axis component of the grid-side voltage through dq transformation; obtains the d-axis component and q-axis component of the valve-side current through dq transformation to perform inner current closed-loop control.

[0017] Furthermore, the DC voltage measurement abnormality judgment unit obtains and judges, based on the DC voltage amplitude, whether the calculated value of the mutation amount of the DC voltage amplitude, the absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase submodule, and the DC voltage measurement abnormality judgment enable state meet the first preset condition; if the first preset condition is met, the DC voltage measurement is judged to be abnormal and an abnormal identification signal is generated; if not, the DC voltage measurement is judged to be normal.

[0018] Furthermore, the algorithm control module also includes:

[0019] The algorithm control device switching unit is communicatively connected with the corresponding algorithm control device switching unit in the other flexible DC system DC voltage measurement abnormality determination device to transmit the abnormality identification signal.

[0020] Accordingly, a second aspect of an embodiment of the present invention provides a method for controlling a DC voltage measurement abnormality determination device, which is used to control any of the above-mentioned DC voltage measurement abnormality determination devices, and includes the following steps:

[0021] Obtain the DC voltage amplitude of the flexible DC system;

[0022] According to the DC voltage amplitude, obtaining a calculated value of a sudden change in the DC voltage amplitude and an absolute value of a difference between the DC voltage amplitude and a maximum voltage amplitude of a phase-splitting submodule of a converter;

[0023] Determine whether the calculated value of the sudden change amount, the absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase submodule, and the DC voltage measurement abnormality determination enable state meet a first preset condition;

[0024] If yes, it is determined that the DC voltage measurement is abnormal, and an abnormality identification signal is generated;

[0025] If not, it is determined that the DC voltage measurement is normal.

[0026] Furthermore, obtaining the calculated value of the sudden change amount of the DC voltage amplitude includes:

[0027] Performing mutation calculation on the DC voltage amplitude, wherein the mutation calculation value is the maximum value of the first difference and the second difference;

[0028] The first difference is the absolute value of the difference between the DC voltage amplitude of the current cycle and the DC voltage amplitude of the previous cycle, and the second difference is the absolute value of the difference between the DC voltage amplitude of the current cycle and the DC voltage amplitudes of the previous two cycles.

[0029] Furthermore, after determining that the DC voltage measurement is abnormal and generating an abnormality identification signal, the method further includes:

[0030] Determine whether the absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase submodule and the DC voltage measurement abnormality determination enable state meet a second preset condition;

[0031] If so, it is determined that the DC voltage amplitude has returned to normal, and the abnormality identification signal is reset;

[0032] If not, it is determined that the DC voltage amplitude is still abnormal, and the abnormal identification signal is maintained.

[0033] Accordingly, a third aspect of an embodiment of the present invention provides a flexible DC system, comprising any of the above-mentioned mutually switchable main DC voltage measurement abnormality determination device and hot standby DC voltage measurement abnormality determination device;

[0034] The main DC voltage measurement abnormality judgment device obtains an abnormal identification signal and sends the abnormal identification signal to the hot standby DC voltage measurement abnormality judgment device, the hot standby DC voltage measurement abnormality judgment device switches to the main state, and at the same time switches the main DC voltage measurement abnormality judgment device to the hot standby state.

[0035] Accordingly, a fourth aspect of an embodiment of the present invention provides a flexible DC system control method, which is used to control the flexible DC system, and includes the following steps:

[0036] When the abnormality identification device for main DC voltage measurement in the flexible DC system generates an abnormality identification signal, the DC voltage is replaced by the maximum voltage of the converter phase submodule;

[0037] Determining whether the communication between the active DC voltage measurement abnormality determination device and the hot standby DC voltage measurement abnormality determination device is normal;

[0038] If so, the main DC voltage measurement abnormality determination device and the hot standby DC voltage measurement abnormality determination device are switched, and the DC voltage in the hot standby DC voltage measurement abnormality determination device is used as the inner loop current closed-loop control current to continue normal operation;

[0039] If not, the operating state of the main DC voltage measurement abnormality determination device is maintained, and the maximum voltage of the converter phase submodule is used as the inner current closed-loop control current to continue normal operation.

[0040] The above technical solutions of the embodiments of the present invention have the following beneficial technical effects:

[0041] By quickly judging the DC voltage abnormality identification signal when the DC voltage is abnormal, the DC voltage closed-loop control quantity DC voltage is quickly switched to the sub-module voltage, and the DC voltage measurement abnormality judgment device is started to switch, the normal and stable operation of the flexible DC system is guaranteed, and the stability and reliability of the flexible DC system are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the logic structure of the dual closed-loop control strategy of the flexible DC system;

[0043] Figure 2 This is a schematic diagram of the principle of a device for determining abnormal DC voltage measurement provided by an embodiment of the present invention;

[0044] Figure 3 This is a structural block diagram of a DC voltage control variable switching algorithm provided by an embodiment of the present invention;

[0045] Figure 4 This is a structural block diagram of a DC voltage measurement abnormality discrimination algorithm provided by an embodiment of the present invention;

[0046] Figure 5 This is a structural block diagram of a DC voltage mutation detection algorithm provided by an embodiment of the present invention;

[0047] Figure 6 This is a logic diagram of a control method for a device for determining abnormal DC voltage measurement provided by an embodiment of the present invention;

[0048] Figure 7 It is a logic diagram of the flexible DC system control method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0049] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0050] Figure 2 The figure is a schematic diagram showing the principle of a device for distinguishing abnormal DC voltage measurement provided by an embodiment of the present invention.

[0051] Figure 3This is a structural block diagram of a DC voltage control variable switching algorithm provided by an embodiment of the present invention.

[0052] Please refer to Figure 2 and Figure 3 A first aspect of an embodiment of the present invention provides a device for determining abnormal DC voltage measurement, including: an electrical quantity acquisition module and an algorithm control module.

[0053] The electrical quantity acquisition module acquires the electrical quantity signals of the flexible DC system and sends the digital signals obtained after digital-to-analog conversion to the algorithm control module. The electrical quantity signals include: grid-side voltage, grid-side current, valve-side current, DC voltage and the maximum voltage of the converter phase sub-module.

[0054] The algorithm control module receives digital signals and performs judgment operations on the DC voltage. When the DC voltage value is abnormal, it replaces the DC voltage with the maximum voltage of the converter phase sub-module to perform closed-loop control of the inner loop current of the flexible DC system.

[0055] After receiving and detecting the abnormal DC voltage measurement signal, the above device uses the maximum voltage Usm_ max Replace the DC voltage Ud.

[0056] The above-mentioned device quickly determines the DC voltage abnormality identification signal when the DC voltage is abnormal, and quickly switches the DC voltage closed-loop control quantity DC voltage to the sub-module voltage, thereby ensuring the normal and stable operation of the flexible DC system and improving the stability and reliability of the flexible DC system.

[0057] Optionally, two identical sets of DC voltage measurement abnormality determination devices operate simultaneously, which are divided into a main DC voltage measurement abnormality determination device and a hot standby DC voltage measurement abnormality determination device.

[0058] Specifically, the electrical quantity acquisition module includes: a dielectric acquisition unit, an optical acquisition unit, and a digital-to-analog conversion unit. The dielectric acquisition unit acquires the grid-side voltage, grid-side current, and valve-side current of the flexible DC system; the optical acquisition unit acquires the DC voltage of the flexible DC system and the average voltage of the converter phase submodule; the digital-to-analog conversion unit receives the electrical quantity signals acquired by the dielectric acquisition unit and the optical acquisition unit, respectively, and obtains the maximum voltage of the converter phase submodule based on the average voltage of the converter phase submodule. It converts the electrical quantity signal into a digital signal and sends it to the algorithm control module. The electrical quantity acquisition module has both dielectric and optical acquisition ports, and simultaneously completes the acquisition and analog-to-digital conversion of electrical quantities from different acquisition media.

[0059] Specifically, the algorithm control module includes an electrical quantity calculation unit, a DC voltage measurement anomaly detection unit, an outer power closed-loop control unit, and an inner current closed-loop control unit, all communicating via the backplane bus. The algorithm control module primarily performs electrical quantity calculation, DC voltage measurement anomaly detection, outer power closed-loop control, inner current closed-loop control, and algorithm control device switching. Communication with external interfaces utilizes optical fiber.

[0060] The electrical quantity calculation unit receives the digital signal and performs normalized calculation on it, and calculates the voltage amplitude U according to the grid side voltage. ac and grid frequency F, calculate the active power P and reactive power Q through the grid-side voltage and grid-side current, and send them to the DC voltage measurement abnormality judgment unit, outer loop power closed-loop control unit and inner loop current closed-loop control unit through the PCIe backplane bus, and complete the phase-locked loop control function at the same time; through the positive and negative DC voltage Ud_ pos , Ud_ neg Calculate the DC voltage U d ; Through the converter submodule voltage Usm_ ap 、Usm_ bp 、Usm_ cp 、Usm_ an 、Usm_ bn 、Usm_ cn Calculate the maximum voltage Usm_ of the converter phase submodule max .

[0061] The DC voltage measurement anomaly determination unit performs a calculation on the DC voltage. If the DC voltage value is abnormal, it sends an abnormality identification signal to the inner current closed-loop control module and the algorithm control device switching module. The DC voltage measurement anomaly determination unit also performs a calculation on the electrical quantity to obtain a DC voltage measurement anomaly identification signal, which it then sends to the outer power closed-loop control unit and the algorithm control device switching unit.

[0062] The outer loop power closed loop control unit obtains the inner loop current closed loop control reference value required by the inner loop current closed loop control unit after the active power class and reactive power class are selected. The outer loop power closed loop control unit obtains the inner loop current reference value i required by the inner loop current closed loop control after the output of the outer loop power closed loop control PI controller is selected by the active power class and reactive power class. dref and i qref When receiving the abnormal DC voltage measurement signal, the maximum voltage Usm_ max Replacement DC voltage U d , the inner loop current closed loop controller d axis current reference value i is generated by the PI controller dref .

[0063] The inner current closed loop control unit obtains u through dq transformation of the grid side voltage sd and u sq ; Get i through dq transformation of valve side voltage d and i q , to perform inner current closed-loop control.

[0064] The DC voltage measurement abnormality judgment is performed by detecting that the DC voltage mutation is greater than △1, the absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase submodule is greater than △2, the absolute value of the difference between the DC voltage amplitude and the DC voltage amplitude of the flexible DC system obtained by the hot standby DC voltage measurement abnormality judgment device is greater than △2, and the DC voltage measurement abnormality judgment enabling state is input. When these conditions are met at the same time, a DC voltage measurement abnormality signal is generated and maintained by the RS trigger; further, by detecting that the absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase submodule is less than △3, the absolute value of the difference between the DC voltage amplitude and the DC voltage amplitude of the flexible DC system obtained by the hot standby DC voltage measurement abnormality judgment device is less than △3, and the DC voltage measurement abnormality judgment enabling state is exited, when any one of the three conditions is met, the DC voltage measurement abnormality signal maintained by the RS trigger is reset.

[0065] Specifically, △1, △2, and △3 are per-unit values based on the grid-side voltage. △1 is usually 0.05 pu, △2 is usually 0.18 pu, and △3 is usually 0.12 pu.

[0066] Detect DC voltage mutations by taking the larger of the absolute value of the difference between the current DC voltage amplitude and the amplitude of the previous cycle, and the absolute value of the difference between the current DC voltage amplitude and the amplitude of the previous two cycles, and determine whether it is greater than △1. If so, it is determined to be a voltage mutation; otherwise, it is determined to be no voltage mutation.

[0067] Figure 4 This is a structural block diagram of a DC voltage measurement abnormality discrimination algorithm provided by an embodiment of the present invention.

[0068] Figure 5 This is a structural block diagram of a DC voltage mutation detection algorithm provided by an embodiment of the present invention.

[0069] For further information, please refer to Figure 4 and Figure 5The DC voltage measurement abnormality judgment unit obtains and judges, based on the DC voltage amplitude, whether the calculated value of the sudden change of the DC voltage amplitude, the absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase submodule, the absolute value of the difference between the DC voltage amplitude and the DC voltage amplitude of the flexible DC system obtained by the hot standby DC voltage measurement abnormality judgment device, and the DC voltage measurement abnormality judgment enabling state meet the first preset condition. If the first preset condition is met, the DC voltage measurement is judged to be abnormal and an abnormal identification signal is generated. If not, the DC voltage measurement is judged to be normal.

[0070] The first precondition is that the following four conditions are met simultaneously:

[0071] 1) The calculated value of the sudden change of DC voltage amplitude is greater than △1;

[0072] 2) The absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase submodule is greater than △2;

[0073] 3) The absolute value of the difference between the DC voltage amplitude and the DC voltage amplitude of the flexible DC system obtained by the hot standby DC voltage measurement abnormality judgment device is greater than △2;

[0074] 4) The DC voltage measurement abnormality judgment enabling state is put into operation.

[0075] like Figure 5 As shown, the DC voltage amplitude mutation detection algorithm determines whether there is a mutation by comparing the absolute value of the difference between the current current amplitude and the amplitude of the previous cycle and the absolute value of the difference between the current current amplitude and the amplitude of the previous two cycles with △1 in the first preset condition.

[0076] Furthermore, the algorithm control module further includes an algorithm control device switching unit that is communicatively connected with corresponding algorithm control device switching units in other flexible DC system DC voltage measurement abnormality determination devices to transmit abnormality identification signals.

[0077] Figure 6 It is a logic diagram of a control method of a device for distinguishing abnormal DC voltage measurement provided by an embodiment of the present invention.

[0078] Accordingly, please refer to Figure 6 A second aspect of an embodiment of the present invention provides a method for controlling a DC voltage measurement abnormality determination device, which is used to control any of the above-mentioned DC voltage measurement abnormality determination devices, including the following steps:

[0079] S110: Obtain a DC voltage amplitude of the flexible DC system.

[0080] S120, based on the DC voltage amplitude, obtain the calculated value of the sudden change of the DC voltage amplitude, the absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase submodule, and the absolute value of the difference between the DC voltage amplitude and the DC voltage amplitude of the flexible DC system obtained by the hot standby DC voltage measurement abnormality judgment device.

[0081] S130, determine whether the calculated value of the mutation amount, the absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase sub-module, the absolute value of the difference between the DC voltage amplitude and the DC voltage amplitude of the flexible DC system obtained by the hot standby DC voltage measurement abnormality judgment device, and the DC voltage measurement abnormality judgment enable state meet the first preset condition.

[0082] S140: If yes, it is determined that the DC voltage measurement is abnormal, and an abnormality identification signal is generated.

[0083] S150: If not, it is determined that the DC voltage measurement is normal.

[0084] Furthermore, in step S120, obtaining the calculated value of the sudden change amount of the DC voltage amplitude specifically includes: performing sudden change amount calculation on the DC voltage amplitude, and the calculated value of the sudden change amount is the maximum value of the first difference and the second difference.

[0085] The first difference is the absolute value of the difference between the DC voltage amplitude of the current cycle and the DC voltage amplitude of the previous cycle, and the second difference is the absolute value of the difference between the DC voltage amplitude of the current cycle and the DC voltage amplitudes of the previous two cycles.

[0086] Furthermore, in step S140, after determining that the DC voltage measurement is abnormal and generating an abnormality identification signal, the method further includes:

[0087] S161, determine whether the absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase sub-module, the absolute value of the difference between the DC voltage amplitude and the DC voltage amplitude of the flexible DC system obtained by the hot standby DC voltage measurement abnormality judgment device, and the DC voltage measurement abnormality judgment enable state meet the second preset condition.

[0088] S162: If so, it is determined that the DC voltage amplitude has returned to normal, and the abnormality identification signal is reset.

[0089] S163: If not, it is determined that the DC voltage amplitude is still abnormal, and the abnormal identification signal is maintained.

[0090] The second preset condition is specifically to meet any of the following conditions:

[0091] 1) The absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase submodule is less than △3;

[0092] 2) The absolute value of the difference between the DC voltage amplitude and the DC voltage amplitude of the flexible DC system obtained by the hot standby DC voltage measurement abnormality judgment device is less than △3;

[0093] 3) Exit the DC voltage measurement abnormality judgment enable state.

[0094] Accordingly, a third aspect of an embodiment of the present invention provides a flexible DC system, comprising any of the above-mentioned switchable main DC voltage measurement abnormality determination device and hot standby DC voltage measurement abnormality determination device.

[0095] The main DC voltage measurement abnormality judgment device obtains the abnormal identification signal and sends the abnormal identification signal to the hot standby DC voltage measurement abnormality judgment device, the hot standby DC voltage measurement abnormality judgment device switches to the main state, and at the same time switches the main DC voltage measurement abnormality judgment device to the hot standby state.

[0096] The DC voltage measurement anomaly detection device is dual-configured. When both devices are operating normally, one is in primary mode and the other in hot standby mode. When the other device is not in hot standby mode, the two devices cannot switch, and the primary device operates independently.

[0097] In addition, when the flexible DC system includes a main DC voltage measurement abnormality judgment device and a hot standby DC voltage measurement abnormality judgment device that can be switched with each other, the judgment standard of the first preset condition further includes: whether the absolute value of the difference between the DC voltage amplitude and the DC voltage amplitude in another device is greater than △2 in the first preset condition; similarly, the judgment standard of the second preset condition further includes: whether the absolute value of the difference between the DC voltage amplitude and the DC voltage amplitude in another device is less than △3 in the second preset condition.

[0098] Figure 7 It is a logic diagram of the flexible DC system control method provided by an embodiment of the present invention.

[0099] Accordingly, please refer to Figure 7 A fourth aspect of an embodiment of the present invention provides a flexible DC system control method, which is used to control the flexible DC system, comprising the following steps:

[0100] S210: When the main DC voltage measurement abnormality determination device in the flexible DC system generates an abnormality identification signal, the DC voltage is replaced by the maximum voltage of the converter phase submodule.

[0101] S220 , determining whether the communication between the active DC voltage measurement abnormality determination device and the hot standby DC voltage measurement abnormality determination device is normal.

[0102] S230, if yes, then switch the main DC voltage measurement abnormality determination device and the hot standby DC voltage measurement abnormality determination device, and then use the DC voltage in the hot standby DC voltage measurement abnormality determination device as the inner loop current closed-loop control current to continue normal operation.

[0103] S240: If not, the operating state of the main DC voltage measurement abnormality determination device is maintained, and the maximum voltage of the converter phase submodule is used as the inner loop current closed-loop control current to continue normal operation.

[0104] The embodiment of the present invention aims to protect a DC voltage measurement anomaly judgment device, a flexible DC system and a control method, wherein the DC voltage measurement anomaly judgment device includes: an electrical quantity acquisition module and an algorithm control module; the electrical quantity acquisition module obtains the electrical quantity signal of the flexible DC system, and sends the digital signal obtained after the electrical quantity signal is converted from digital to analog to the algorithm control module, wherein the electrical quantity signal includes: grid-side voltage, grid-side current, valve-side current, DC voltage and the maximum voltage of the converter phase submodule; the algorithm control module receives the digital signal, performs a judgment operation on the DC voltage, and when the DC voltage value is abnormal, replaces the DC voltage with the maximum voltage of the converter phase submodule, and simultaneously starts the switching of the DC voltage measurement anomaly judgment device to perform closed-loop control of the inner loop current of the flexible DC system. The above technical solution has the following effects:

[0105] By quickly judging the DC voltage abnormality identification signal when the DC voltage is abnormal, the DC voltage closed-loop control quantity DC voltage is quickly switched to the sub-module voltage, and the DC voltage measurement abnormality judgment device is started to switch, the normal and stable operation of the flexible DC system is guaranteed, and the stability and reliability of the flexible DC system are improved.

[0106] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A device for determining abnormality in DC voltage measurement, characterized in that: include: Electrical quantity acquisition module and algorithm control module; The electrical quantity acquisition module acquires electrical quantity signals of the flexible DC system and sends digital signals obtained by digital-to-analog conversion of the electrical quantity signals to the algorithm control module, wherein the electrical quantity signals include: grid-side voltage, grid-side current, valve-side current, DC voltage, and maximum voltage of the converter phase submodule; The algorithm control module receives the digital signal, performs a judgment operation on the DC voltage, and replaces the DC voltage with the maximum voltage of the converter phase submodule when the DC voltage value is abnormal, so as to perform closed-loop control of the inner loop current of the flexible DC system; The algorithm control module includes: an electrical quantity calculation unit communicating via a backplane bus, a DC voltage measurement abnormality determination unit, an outer power closed-loop control unit, and an inner current closed-loop control unit; The electrical quantity calculation unit receives the digital signal and performs per-unit calculation on it, calculates the voltage amplitude and grid frequency based on the grid-side voltage, calculates the active power and reactive power based on the grid-side voltage and the grid-side current, and sends them to the DC voltage measurement abnormality determination unit, the outer power closed-loop control unit, and the inner current closed-loop control unit, and calculates the DC voltage based on the positive and negative DC voltages; The DC voltage measurement abnormality determination unit performs a judgment operation on the DC voltage and sends an abnormality identification signal to the inner current closed-loop control module and the algorithm control device switching module when the DC voltage value is abnormal; The outer power closed-loop control unit obtains the inner current closed-loop control reference value required by the inner current closed-loop control unit after selecting the active power category and the reactive power category; The inner current closed-loop control unit obtains the d-axis component and q-axis component of the grid-side voltage through dq transformation; obtains the d-axis component and q-axis component of the valve-side current through dq transformation to perform inner current closed-loop control.

2. The DC voltage measurement abnormality determination device according to claim 1, characterized in that: The electrical quantity acquisition module includes: a dielectric acquisition unit for collecting the grid-side voltage, grid-side current, and valve-side current of the flexible DC system; An optical medium acquisition unit, which collects the DC voltage of the flexible DC system and the average voltage of the converter phase submodule; A digital-to-analog conversion unit receives the electrical quantity signals collected by the dielectric acquisition unit and the optical medium acquisition unit respectively, obtains the maximum voltage of the converter phase submodule based on the average voltage of the converter phase submodule, converts the electrical quantity signal into a digital signal and sends it to the algorithm control module.

3. The DC voltage measurement abnormality determination device according to claim 1, characterized in that: The DC voltage measurement abnormality judgment unit obtains and judges, based on the DC voltage amplitude, whether the calculated value of the sudden change of the DC voltage amplitude, the absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase submodule, and the DC voltage measurement abnormality judgment enable state meet a first preset condition; if the first preset condition is met, the DC voltage measurement is judged to be abnormal and an abnormal identification signal is generated; if not, the DC voltage measurement is judged to be normal.

4. The DC voltage measurement abnormality determination device according to claim 1, characterized in that: The algorithm control module also includes: The algorithm control device switching unit is communicatively connected with the corresponding algorithm control device switching unit in the other flexible DC system DC voltage measurement abnormality determination device to transmit the abnormality identification signal.

5. A control method for a DC voltage measurement abnormality determination device, characterized in that: The device for controlling the DC voltage measurement abnormality determination device according to any one of claims 1 to 4 comprises the following steps: Obtain the DC voltage amplitude of the flexible DC system; According to the DC voltage amplitude, obtaining a calculated value of a sudden change in the DC voltage amplitude and an absolute value of a difference between the DC voltage amplitude and a maximum voltage amplitude of a phase-splitting submodule of a converter; Determine whether the calculated value of the sudden change amount, the absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase submodule, and the DC voltage measurement abnormality determination enable state meet a first preset condition; If yes, it is determined that the DC voltage measurement is abnormal, and an abnormality identification signal is generated; If not, it is determined that the DC voltage measurement is normal.

6. The control method of the DC voltage measurement abnormality determination device according to claim 5, characterized in that: The obtaining of the calculated value of the sudden change of the DC voltage amplitude includes: Performing mutation calculation on the DC voltage amplitude, wherein the mutation calculation value is the maximum value of the first difference and the second difference; The first difference is the absolute value of the difference between the DC voltage amplitude of the current cycle and the DC voltage amplitude of the previous cycle, and the second difference is the absolute value of the difference between the DC voltage amplitude of the current cycle and the DC voltage amplitudes of the previous two cycles.

7. The control method of the DC voltage measurement abnormality determination device according to claim 5, characterized in that: After determining that the DC voltage measurement is abnormal and generating an abnormality identification signal, the method further includes: Determine whether the absolute value of the difference between the DC voltage amplitude and the maximum voltage amplitude of the converter phase submodule and the DC voltage measurement abnormality determination enable state meet a second preset condition; If so, it is determined that the DC voltage amplitude has returned to normal, and the abnormality identification signal is reset; If not, it is determined that the DC voltage amplitude is still abnormal, and the abnormal identification signal is maintained.

8. A flexible DC system, characterized in that: It includes a DC voltage measurement abnormality discrimination device in a main state and a DC voltage measurement abnormality discrimination device in a hot standby state, wherein the DC voltage measurement abnormality discrimination device is the DC voltage measurement abnormality discrimination device according to any one of claims 1 to 4; The DC voltage measurement abnormality discrimination device in the master state obtains an abnormal identification signal and sends the abnormal identification signal to the DC voltage measurement abnormality discrimination device in the hot standby state, the DC voltage measurement abnormality discrimination device in the hot standby state is switched to the master state, and at the same time, the DC voltage measurement abnormality discrimination device in the master state is switched to the hot standby state.

9. A flexible DC system control method, characterized in that: It is used to control the flexible DC system according to claim 8, comprising the following steps: When the DC voltage measurement abnormality discrimination device in the active state of the flexible DC system generates an abnormal identification signal, the DC voltage is replaced by the maximum voltage of the converter phase submodule; Determining whether communication between the DC voltage measurement abnormality determination device in the active state and the DC voltage measurement abnormality determination device in the hot standby state is normal; If so, switching the DC voltage measurement abnormality determination device in the main state and the DC voltage measurement abnormality determination device in the hot standby state, and then using the DC voltage in the DC voltage measurement abnormality determination device in the hot standby state as the inner loop current closed-loop control current, and continuing normal operation; If not, the operation state of the DC voltage measurement abnormality determination device in the main state is maintained, and the maximum voltage of the converter phase submodule is used as the inner loop current closed-loop control current to continue normal operation.

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