Valve-side current measurement abnormality determination device, flexible DC system and control method

Abstract

The present invention discloses a valve-side current measurement abnormality discrimination device, a flexible direct current system, and a control method. The valve-side current measurement abnormality discrimination device includes: an electrical quantity acquisition module that obtains electrical quantity signals of the flexible direct current system and sends digital signals obtained after digital-to-analog conversion of the electrical quantity signals to an algorithm control module. The electrical quantity signals include: grid-side voltage, grid-side current, valve-side current, DC voltage, and converter current; the algorithm control module receives the digital signals, performs judgment operations on the valve-side current, and replaces the valve-side current with the converter current when the valve-side current value is abnormal, so as to perform closed-loop control of the inner loop current of the flexible direct current system. By quickly discriminating the valve-side current abnormality signal when the valve-side current of the flexible direct current system is abnormal, the inner loop current control quantity, the valve-side current, is quickly switched to the converter current, and the valve-side current measurement abnormality discrimination device is started to switch at the same time, thereby ensuring the normal and stable operation of the system and improving its stability and reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible direct current system detection, and in particular to a valve-side current 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 typically adopt a dual closed-loop control strategy of "outer loop power + inner loop current". The inner loop current closed control uses the converter transformer valve-side current as the closed-loop controller control variable. Abnormal valve-side current directly determines the quality of the VSC-HVDC system's inner loop closed-loop control link. Therefore, the identification and control methods of abnormal valve-side current measurement are very important.

[0004] VSC-HVDC systems usually adopt a dual closed-loop control strategy logic structure of "outer loop power + inner loop current", such as Figure 1 As shown. If the valve side current i va 、i vb 、i vc Abnormal data collection directly affects the output results of the inner current closed-loop control, resulting in abnormal calculation of the voltage reference values ​​of each bridge arm sub-module of the converter valve, and the flexible DC system may eventually be forced to shut down. Summary of the Invention

[0005] The purpose of the embodiments of the present invention is to provide a valve-side current measurement abnormality judgment device, a flexible DC system and a control method, which can quickly judge the valve-side current abnormality signal when the valve-side current in the flexible DC system is abnormal, quickly switch the inner-loop current control quantity valve-side current to the converter current, and simultaneously start the algorithm control module switching. Through the dual measures of inner-loop current control quantity switching and system switching, the flexible DC system can be guaranteed to operate normally and stably, thereby improving the stability and reliability of the flexible DC system.

[0006] To solve the above technical problems, a first aspect of an embodiment of the present invention provides a device for determining abnormal current measurement on the valve side of a flexible DC system, comprising: an electrical quantity acquisition module and an algorithm control module;

[0007] 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 converter current;

[0008] The algorithm control module receives the digital signal, performs a judgment operation on the valve-side current, and replaces the valve-side current with the converter current when the valve-side current value is abnormal, so as to perform closed-loop control of the inner loop current of the flexible DC system.

[0009] Furthermore, the electrical quantity acquisition module includes:

[0010] a dielectric acquisition unit for collecting the grid-side voltage, grid-side current, and valve-side current of the flexible DC system;

[0011] an optical medium acquisition unit for acquiring the DC voltage and converter current of the flexible DC system;

[0012] A digital-to-analog conversion unit receives the electrical quantity signals collected by the dielectric acquisition unit and the optical medium acquisition unit respectively, converts the electrical quantity signals into digital signals, and sends the digital signals to the algorithm control module.

[0013] Furthermore, the algorithm control module includes: an electrical quantity calculation unit communicating via a backplane bus, a valve-side current measurement abnormality determination unit, an outer power closed-loop control unit, and an inner current closed-loop control unit;

[0014] The electrical quantity calculation unit receives the digital signal and performs standardized calculation on it, calculates the voltage amplitude and grid frequency according to the grid-side voltage, calculates the active power and reactive power according to the grid-side voltage and the grid-side current, and sends them to the valve-side current measurement abnormality determination unit, the outer power closed-loop control unit, and the inner current closed-loop control unit;

[0015] The valve-side current measurement abnormality determination unit performs a judgment operation on the valve-side current, and sends an abnormality identification signal to the inner-loop current closed-loop control module and the algorithm control device switching module when the value of the valve-side current is abnormal;

[0016] 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;

[0017] After receiving the abnormal identification signal, the inner current closed-loop control unit replaces the valve-side current with the converter current to perform the inner current closed-loop control.

[0018] Furthermore, the valve-side current measurement abnormality judgment unit obtains and judges, based on the valve-side current amplitude, whether the calculated value of the mutation amount of the valve-side current amplitude, the absolute value of the difference between the valve-side current amplitude and the converter current amplitude, and the valve-side current measurement abnormality judgment enable state meet the first preset condition; if the first preset condition is met, the valve-side current measurement is judged to be abnormal and an abnormal identification signal is generated; if not, the valve-side current measurement is judged to be normal.

[0019] Furthermore, the algorithm control module also includes:

[0020] The algorithm control device switching unit is communicatively connected with the corresponding algorithm control device switching unit in the other flexible DC system valve-side current measurement abnormality determination device to transmit the abnormality identification signal.

[0021] Accordingly, a second aspect of an embodiment of the present invention provides a method for controlling a valve-side current measurement abnormality determination device, which is used to control any of the above-mentioned valve-side current measurement abnormality determination devices, comprising the following steps:

[0022] Obtain the valve-side current amplitude of the flexible DC system;

[0023] According to the valve-side current amplitude, obtaining a calculated value of a sudden change in the valve-side current amplitude and an absolute value of a difference between the valve-side current amplitude and a converter current amplitude;

[0024] Determining whether the calculated value of the mutation amount, the absolute value of the difference between the valve-side current amplitude and the converter current amplitude, and the valve-side current measurement abnormality determination enable state meet a first preset condition;

[0025] If yes, it is determined that the valve side current measurement is abnormal, and an abnormality identification signal is generated;

[0026] If not, it is determined that the valve side current measurement is normal.

[0027] Furthermore, obtaining the calculated value of the sudden change amount of the valve-side current amplitude includes:

[0028] Performing mutation calculation on the valve-side current amplitude, wherein the mutation calculation value is the maximum value of the first difference and the second difference;

[0029] Among them, the first difference is the absolute value of the difference between the valve side current amplitude of the current cycle and the valve side current amplitude of the previous cycle, and the second difference is the absolute value of the difference between the valve side current amplitude of the current cycle and the valve side current amplitude of the previous two cycles.

[0030] Furthermore, after determining that the valve-side current measurement is abnormal and generating an abnormality identification signal, the method further includes:

[0031] determining whether an absolute value of a difference between the valve-side current amplitude and the converter current amplitude and an enable state of the valve-side current measurement abnormality determination meet a second preset condition;

[0032] If so, it is determined that the valve-side current amplitude has returned to normal, and the abnormal identification signal is reset;

[0033] If not, it is determined that the valve-side current amplitude is still abnormal, and the abnormal identification signal is maintained.

[0034] 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 valve side current measurement abnormality determination device and hot standby valve side current measurement abnormality determination device;

[0035] The main valve side current measurement abnormality judgment device obtains an abnormal identification signal and sends the abnormal identification signal to the hot standby valve side current measurement abnormality judgment device, and the hot standby valve side current measurement abnormality judgment device switches to the main state, and at the same time switches the main valve side current measurement abnormality judgment device to the hot standby state.

[0036] Accordingly, a fourth aspect of an embodiment of the present invention provides a flexible DC system control method for controlling the flexible DC system, comprising the following steps:

[0037] When the abnormality identification device for measuring the main valve side current in the flexible DC system generates an abnormality identification signal, the valve side current is replaced by the converter current;

[0038] determining whether the communication between the main valve side current measurement abnormality determination device and the hot standby valve side current measurement abnormality determination device is normal;

[0039] If so, the main valve side current measurement abnormality determination device and the hot standby valve side current measurement abnormality determination device are switched, and the valve side current in the hot standby valve side current measurement abnormality determination device is used as the inner loop current closed-loop control current to continue normal operation;

[0040] If not, the operating state of the main valve side current measurement abnormality determination device is maintained, and the converter current is used as the inner loop current closed-loop control current to continue normal operation.

[0041] The above technical solutions of the embodiments of the present invention have the following beneficial technical effects:

[0042] By quickly identifying the abnormal valve side current signal when the valve side current of the flexible DC system is abnormal, the inner loop current control quantity valve side current is quickly switched to the converter current, and the valve side current measurement abnormality identification device is started to switch at the same time. Through the dual measures of inner loop current control quantity switching and system switching, the normal and stable operation of the flexible DC system can be guaranteed, thereby improving the stability and reliability of the flexible DC system. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of the logic structure of the dual closed-loop control strategy of the flexible DC system;

[0044] Figure 2 This is a schematic diagram of the principle of a device for determining abnormality in valve-side current measurement provided by an embodiment of the present invention;

[0045] Figure 3 This is a structural block diagram of an inner loop current control variable switching algorithm provided by an embodiment of the present invention;

[0046] Figure 4 This is a structural block diagram of a valve-side current measurement abnormality discrimination algorithm provided by an embodiment of the present invention;

[0047] Figure 5 This is a structural block diagram of a valve-side current mutation detection algorithm provided by an embodiment of the present invention;

[0048] Figure 6 This is a logic diagram of a control method for a device for determining abnormality in valve-side current measurement provided by an embodiment of the present invention;

[0049] Figure 7 It is a logic diagram of the flexible DC system control method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0050] 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.

[0051] Figure 2 It is a schematic diagram of the principle of the valve side current measurement abnormality judgment device provided by an embodiment of the present invention.

[0052] Figure 3 This is a structural block diagram of the inner loop current control variable switching algorithm provided by an embodiment of the present invention.

[0053] Please refer to Figure 2 and Figure 3According to a first aspect of an embodiment of the present invention, a device for determining abnormal valve-side current measurement in a flexible DC system is provided, comprising an electrical quantity acquisition module and an algorithm control module. The electrical quantity acquisition module acquires electrical quantity signals from the flexible DC system and sends digital signals obtained by 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 converter current. The algorithm control module receives the digital signals, performs a judgment operation on the valve-side current, and replaces the valve-side current with the converter current when the valve-side current value is abnormal, thereby performing closed-loop control of the inner current of the flexible DC system.

[0054] The above technical solution can quickly identify the abnormal valve side current signal when the valve side current of the flexible DC system is abnormal, and quickly switch the inner loop current control quantity valve side current to the converter current. By switching the inner loop current control quantity, the normal and stable operation of the flexible DC system can be guaranteed, thereby improving the stability and reliability of the flexible DC system.

[0055] Optionally, two identical sets of flexible DC system valve-side current measurement abnormality judgment devices operate simultaneously, namely, a main flexible DC system valve-side current measurement abnormality judgment device and a hot standby flexible DC system valve-side current measurement abnormality judgment device.

[0056] The electrical quantity acquisition module primarily performs functions such as electrical quantity signal acquisition and analog-to-digital conversion, and transmits the converted digital signals to the algorithm control module via optical fiber. Specifically, the electrical quantity acquisition module comprises a dielectric acquisition unit, an optical acquisition unit, and a digital-to-analog conversion unit. The dielectric acquisition unit collects the grid-side voltage, grid-side current, and valve-side current of the flexible DC system; the optical acquisition unit collects the DC voltage and converter current of the flexible DC system; and the digital-to-analog conversion unit receives the electrical quantity signals collected by the dielectric and optical acquisition units, converts them into digital signals, and transmits them to the algorithm control module.

[0057] The electrical quantity acquisition module has both dielectric and optical medium acquisition ports, and simultaneously completes the acquisition and analog-to-digital conversion of electrical quantities of different acquisition media.

[0058] The algorithm control module primarily performs electrical quantity calculations, valve-side current 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. Specifically, the algorithm control module includes an electrical quantity calculation unit (which communicates via the PCIe backplane bus), a valve-side current measurement anomaly detection unit, an outer power closed-loop control unit, and an inner current closed-loop control unit.

[0059] The electrical quantity calculation unit receives the digital signal and performs standardization calculation on it, and calculates the voltage amplitude U according to the grid side voltage. acand grid frequency F, calculate active power P and reactive power Q through grid side voltage and grid side current, and send them to valve side current measurement abnormality judgment unit, outer loop power closed loop control unit and inner loop current closed loop control unit; at the same time, complete the phase-locked loop control function; calculate DC voltage U through positive and negative DC voltage d .

[0060] The valve side current measurement abnormality judgment unit performs judgment operation on the valve side current, and sends an abnormal identification signal to the inner loop current closed-loop control module and the algorithm control device switching module when the value of the valve side current is abnormal.

[0061] Optionally, the valve-side current measurement abnormality determination unit communicates with a valve-side current measurement abnormality determination unit in another device using optical fiber to exchange valve-side current amplitude signals of the two systems.

[0062] After the outer power closed-loop control unit is selected by the active power class and the reactive power class, it obtains the inner current closed-loop control reference value i required by the inner current closed-loop control unit. dref and i qref .

[0063] After receiving the abnormal identification signal, 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, and converts the valve-side current i va ,i vb ,i vc Replaced by the converter current i ca ,i cb ,i cc , complete the dq transformation to get i d and i q , to perform inner current closed-loop control.

[0064] The valve side current measurement abnormality is judged by detecting that the valve side current mutation is greater than △1, the absolute value of the difference between the valve side current amplitude and the converter current amplitude is greater than △2, the absolute value of the difference between the valve side current amplitude and the hot standby flexible DC system valve side current amplitude is greater than △2, and the valve side current measurement abnormality judgment enabling state is enabled at the same time, a valve side current measurement abnormality signal is generated and maintained by the RS trigger; further by detecting that the absolute value of the difference between the valve side current amplitude and the converter current amplitude is less than △3, the absolute value of the difference between the valve side current amplitude and the hot standby flexible DC system valve side current amplitude is less than △3, or the valve side current measurement abnormality judgment enabling state is exited, when any one of the three conditions is met, the valve side current measurement abnormality signal maintained by the RS trigger is reset.

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

[0066] Detect the sudden change of the valve side current by taking the larger of 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, and judge whether it is greater than △1. If so, it is determined to be a sudden change of the current; otherwise, it is determined that the current is not a sudden change.

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

[0068] Figure 5 This is a structural block diagram of a valve-side current mutation detection algorithm provided by an embodiment of the present invention.

[0069] Further, please refer to Figure 4 and Figure 5 The valve-side current measurement abnormality judgment unit obtains and judges, based on the valve-side current amplitude, the calculated value of the sudden change of the valve-side current amplitude, the absolute value of the difference between the valve-side current amplitude and the converter current amplitude, the absolute value of the difference between the valve-side current amplitude and the hot standby flexible DC system valve-side current amplitude, and whether the valve-side current measurement abnormality judgment enabling state meets the first preset condition. If the first preset condition is met, the valve-side current measurement is judged to be abnormal and an abnormal identification signal is generated. If not, the valve-side current 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 the valve side current amplitude is greater than △1;

[0072] 2) The absolute value of the difference between the valve-side current amplitude and the converter current amplitude is greater than △2;

[0073] 3) The absolute value of the difference between the valve-side current amplitude and the hot standby flexible DC system valve-side current amplitude is greater than △2;

[0074] 4) The valve side current measurement abnormality judgment enabling state is put into operation.

[0075] like Figure 5 As shown, the valve side current 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 the first preset condition △1.

[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 valve-side current measurement abnormality determination devices to transmit abnormality identification signals.

[0077] The algorithm control device switching unit communicates with the algorithm control device switching module in another device using optical fiber to achieve device switching. Upon receiving a valve-side current measurement anomaly identification signal, the valve-side current measurement anomaly identification device in the primary state switches the system if the other device is in hot standby mode. If the other device is not in hot standby mode, the system does not switch, and the primary system continues to operate.

[0078] Figure 6 This is a logic diagram of the control method of the valve side current measurement abnormality judgment device provided by the embodiment of the present invention.

[0079] Accordingly, please refer to Figure 6 A second aspect of an embodiment of the present invention provides a method for controlling a valve-side current measurement abnormality determination device, which is used to control any of the above-mentioned valve-side current measurement abnormality determination devices, including the following steps:

[0080] S110: Obtain a valve-side current amplitude of the flexible DC system.

[0081] S120 , obtaining, based on the valve-side current amplitude, a calculated value of a sudden change in the valve-side current amplitude and an absolute value of a difference between the valve-side current amplitude and the converter current amplitude.

[0082] S130, determine whether the calculated value of the mutation amount, the absolute value of the difference between the valve-side current amplitude and the converter current amplitude, the absolute value of the difference between the valve-side current amplitude and the valve-side current amplitude of the hot standby flexible DC system, and the valve-side current measurement abnormality judgment enable state meet the first preset condition.

[0083] Specifically, the first precondition is that the following four conditions are met at the same time:

[0084] 1) The calculated value of the sudden change of the valve side current amplitude is greater than △1;

[0085] 2) The absolute value of the difference between the valve-side current amplitude and the converter current amplitude is greater than △2;

[0086] 3) The absolute value of the difference between the valve-side current amplitude and the hot standby flexible DC system valve-side current amplitude is greater than △2;

[0087] 4) The valve side current measurement abnormality judgment enabling state is put into operation.

[0088] S140: If yes, it is determined that the valve side current measurement is abnormal, and an abnormality identification signal is generated.

[0089] S150: If not, it is determined that the valve side current measurement is normal.

[0090] Furthermore, in step S130, a calculated value of the sudden change amount of the valve-side current amplitude is obtained, specifically:

[0091] Calculate the sudden change of the valve side current amplitude, and the calculated sudden change value is the maximum value of the first difference and the second difference;

[0092] Among them, the first difference is the absolute value of the difference between the valve side current amplitude of the current cycle and the valve side current amplitude of the previous cycle, and the second difference is the absolute value of the difference between the valve side current amplitude of the current cycle and the valve side current amplitudes of the previous two cycles.

[0093] Furthermore, after determining that the valve-side current measurement is abnormal and generating an abnormality identification signal in step S150, the method further includes:

[0094] S161, determine whether the absolute value of the difference between the valve-side current amplitude and the converter current amplitude, the absolute value of the difference between the valve-side current amplitude and the hot standby flexible DC system valve-side current amplitude, and the valve-side current measurement abnormality judgment enable state meet the second preset condition.

[0095] S162: If so, it is determined that the valve side current amplitude has returned to normal, and the abnormal identification signal is reset.

[0096] S163: If not, it is determined that the valve side current amplitude is still abnormal, and the abnormal identification signal is maintained.

[0097] The second preset condition is specifically to meet any of the following conditions:

[0098] 1) The absolute value of the difference between the valve-side current amplitude and the converter current amplitude is less than △3;

[0099] 2) The absolute value of the difference between the valve-side current amplitude and the hot standby flexible DC system valve-side current amplitude is less than △3;

[0100] 3) The valve side current measurement abnormality judgment enabling state is exited.

[0101] 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 valve side current measurement abnormality determination device and hot standby valve side current measurement abnormality determination device.

[0102] The main valve side current measurement abnormality judgment device obtains the abnormal identification signal and sends the abnormal identification signal to the hot standby valve side current measurement abnormality judgment device, the hot standby valve side current measurement abnormality judgment device switches to the main state, and at the same time switches the main valve side current measurement abnormality judgment device to the hot standby state.

[0103] The valve-side current measurement abnormality detection device can be configured in a dual configuration. When both devices are operating normally, one device is in primary mode and the other in hot standby mode. If the device that should be in hot standby mode is not in hot standby mode, the two devices cannot switch, and the system in primary mode will operate alone.

[0104] In addition, when the flexible DC system includes a main valve-side current measurement abnormality judgment device and a hot standby valve-side current measurement abnormality judgment device that can be switched with each other, the judgment criteria of the first preset condition further include: whether the absolute value of the difference between the threshold current amplitude and the valve-side current amplitude in another device is greater than △2 in the first preset condition; similarly, the judgment criteria of the second preset condition further include: whether the absolute value of the difference between the threshold current amplitude and the valve-side current amplitude in another device is less than △3 in the second preset condition.

[0105] Accordingly, a fourth aspect of an embodiment of the present invention provides a flexible DC system control method for controlling the flexible DC system, comprising the following steps:

[0106] S210: When the main valve-side current measurement abnormality determination device in the flexible DC system generates an abnormality identification signal, the valve-side current is replaced by the converter current.

[0107] S220 , determining whether the communication between the active valve side current measurement abnormality determination device and the hot standby valve side current measurement abnormality determination device is normal.

[0108] S230, if yes, switch the main valve side current measurement abnormality judgment device and the hot standby valve side current measurement abnormality judgment device, and then use the valve side current in the hot standby valve side current measurement abnormality judgment device as the inner loop current closed-loop control current to continue normal operation.

[0109] S240, if not, then maintain the operating state of the main valve side current measurement abnormality determination device, and use the converter current as the inner loop current closed-loop control current to continue normal operation.

[0110] The embodiment of the present invention aims to protect a valve-side current measurement abnormality judgment device, a flexible DC system and a control method, wherein the valve-side current measurement abnormality 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 converter current; the algorithm control module receives the digital signal, performs a judgment operation on the valve-side current, and replaces the valve-side current with the converter current when the valve-side current value is abnormal, and simultaneously starts the valve-side current measurement abnormality judgment device switching to perform closed-loop control of the inner-loop current of the flexible DC system. The above technical solution has the following effects:

[0111] By quickly identifying the abnormal valve side current signal when the valve side current of the flexible DC system is abnormal, the inner loop current control quantity valve side current is quickly switched to the converter current, and the valve side current measurement abnormality identification device is started to switch at the same time. Through the dual measures of inner loop current control quantity switching and system switching, the normal and stable operation of the flexible DC system can be guaranteed, thereby improving the stability and reliability of the flexible DC system.

[0112] 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 current measurement on a valve side, 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 converter current; The algorithm control module receives the digital signal, performs a judgment operation on the valve-side current, and replaces the valve-side current with the converter current when the value of the valve-side current is abnormal, so as to perform closed-loop control of the inner current of the flexible DC system; The algorithm control module includes: an electrical quantity calculation unit communicating via a backplane bus, a valve side current 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 standardized calculation on it, calculates the voltage amplitude and grid frequency according to the grid-side voltage, calculates the active power and reactive power according to the grid-side voltage and the grid-side current, and sends them to the valve-side current measurement abnormality determination unit, the outer power closed-loop control unit, and the inner current closed-loop control unit; The valve-side current measurement abnormality determination unit performs a judgment operation on the valve-side current, and sends an abnormality identification signal to the inner-loop current closed-loop control module and the algorithm control device switching module when the value of the valve-side current 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; After receiving the abnormal identification signal, the inner current closed-loop control unit replaces the valve-side current with the converter current to perform the inner current closed-loop control.

2. The valve side current measurement abnormality determination device according to claim 1, characterized in that: The electrical quantity acquisition module includes: a dielectric acquisition unit for acquiring the grid-side voltage, grid-side current, and valve-side current of the flexible DC system; an optical medium acquisition unit for acquiring the DC voltage and converter current of the flexible DC system; A digital-to-analog conversion unit receives the electrical quantity signals collected by the dielectric acquisition unit and the optical medium acquisition unit respectively, converts the electrical quantity signals into digital signals, and sends the digital signals to the algorithm control module.

3. The valve side current measurement abnormality determination device according to claim 1, characterized in that: The valve-side current measurement abnormality judgment unit obtains and judges whether the calculated value of the sudden change of the valve-side current amplitude, the absolute value of the difference between the valve-side current amplitude and the converter current amplitude, and the valve-side current measurement abnormality judgment enabling state meet the first preset condition based on the valve-side current amplitude. If the first preset condition is met, the valve-side current measurement is judged to be abnormal and an abnormal identification signal is generated. If not, the valve-side current measurement is judged to be normal.

4. The valve side current 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 valve-side current measurement abnormality determination device to transmit the abnormality identification signal.

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

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

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

8. A flexible DC system, characterized in that: The device comprises the valve side current measurement abnormality determination device according to any one of claims 1 to 4; The valve-side current measurement abnormality discrimination device in the main state obtains an abnormal identification signal and sends the abnormal identification signal to the valve-side current measurement abnormality discrimination device in the hot standby state. The valve-side current measurement abnormality discrimination device in the hot standby state is switched to the main state, and at the same time, the valve-side current measurement abnormality discrimination device in the main state is switched to the hot standby state.

9. A flexible DC system control method, characterized in that: The method for controlling the flexible DC system according to claim 8 comprises the following steps: When the valve-side current measurement abnormality discrimination device in the active state of the flexible DC system generates an abnormal identification signal, the valve-side current is replaced by the converter current; determining whether the communication between the valve-side current measurement abnormality determination device in the active state and the valve-side current measurement abnormality determination device in the hot standby state is normal; If so, the valve-side current measurement abnormality determination device in the active state and the valve-side current measurement abnormality determination device in the hot standby state are switched, and the valve-side current in the valve-side current measurement abnormality determination device in the hot standby state is used as the inner loop current closed-loop control current, and normal operation is continued; If not, the operation state of the valve-side current measurement abnormality determination device in the main state is maintained, and the converter current is used as the inner loop current closed-loop control current to continue normal operation.

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