CN115047333B - A passive unlocking test method and system for offshore platform converter valve wharf - Google Patents

Abstract

The invention relates to a passive unlocking test method and a passive unlocking test system for a converter valve wharf of an offshore platform, wherein the passive unlocking test method comprises the following steps: charging a sub-module capacitor of the offshore platform converter valve through a test power supply at a dock of the marine foundation, and disconnecting a wiring switch between the test power supply and the offshore platform converter valve after the charging is finished; issuing a converter valve short-time unlocking command based on an open-loop control strategy to enable the converter valve of the offshore platform to finish short-time unlocking operation by means of energy stored in a sub-module capacitor; and judging operation data of the offshore platform converter valve during short-time unlocking operation based on preset test criteria, and verifying the relevant performance of the flexible direct-current offshore platform. The invention utilizes the low-voltage and small-capacity test power supply of the marine base to realize friendly charging and safe unlocking of the high-voltage and large-power converter valve, so that the comprehensive verification of the basic function of the converter valve can be realized in advance before the offshore platform reaches the offshore station site, and the converter valve can be widely applied to the field debugging field of the flexible and straight system.

Description

A test method and system for passive unlocking of offshore platform converter valve wharf

technical field

The invention relates to the field of on-site debugging of an offshore wind power flexible direct current transmission system, in particular to a test method and system for passive unlocking of an offshore platform converter valve wharf used for an offshore wind power flexible direct current transmission system.

Background technique

Flexible DC transmission technology is the preferred technical solution for reliable grid connection of offshore wind power, and it is also the only large-scale offshore wind power grid connection solution with engineering practice experience. Different from the onshore flexible DC system, the offshore wind power flexible DC transmission system centrally arranges the electrical system, auxiliary system and safety system equipment of the offshore converter station on the offshore platform. The offshore platform is composed of foundation piles, jackets and upper modules. , and its construction and installation costs account for about 19% of the total project investment.

Due to the harsh natural environment at sea, limited installation and test conditions, and high transportation and maintenance costs, it is generally adopted to install all the equipment of the offshore platform on the wharf of the offshore engineering base and pass the test before transporting the offshore platform to the offshore site as a whole. plan in place. Considering that the cost of repairing the offshore platform after it arrives at the offshore site is immeasurable, the primary and secondary functions of the offshore converter station equipment should be fully verified during the test at the offshore base wharf, so as to detect major potential problems in advance and Timely rectification will lay a good foundation for the smooth development of subsequent commissioning after it arrives at the offshore station.

Among them, the converter valve is the key equipment for energy conversion in the offshore converter station, and the successful unlocking of the converter valve is a fundamental sign that the basic functions of the offshore converter station have been fully verified. However, the normal unlocking of the converter valve often has high requirements on the capacity of the connected power source. During the installation and test period of the offshore platform at the wharf of the offshore engineering base, the capacity of the temporary low-voltage test power source it can use is only MVA level, which is far below the capacity that can support the converter. The power supply capacity required for the valve to unlock normally. In order to fully verify the extreme control performance, valve control performance, pole control and valve control interface, and insulation performance of the offshore platform in advance, how to realize high-voltage, high-power The successful unlocking of the converter valve is a key problem to be solved, and this technology will also have broad application prospects.

Contents of the invention

In view of the above problems, the object of the present invention is to provide a passive unlocking test method and system for the converter valve wharf on an offshore platform, which can successfully unlock the converter valve by using the low-voltage, small-capacity test power supply at the wharf of the offshore engineering base, and at the same time The extreme control performance, valve control performance, extreme control and valve control interface, and insulation performance of the offshore platform of the offshore wind power flexible DC transmission system are fully verified.

To achieve the above object, the present invention takes the following technical solutions:

In a first aspect, the present invention provides a test method for passive unlocking of a converter valve wharf on an offshore platform, which includes the following steps:

Charge the sub-module capacitor of the offshore platform converter valve through the test power supply of the offshore base wharf, and disconnect the wiring switch between the test power supply and the offshore platform converter valve after charging is completed;

Based on the open-loop control strategy, a short-term unlocking command of the converter valve is issued, so that the converter valve on the offshore platform can complete the short-term unlocking operation by relying on the energy stored in the capacitor of the sub-module;

Based on the preset test criteria, the operation data of the converter valve on the offshore platform during the short-term unlocking operation period is discriminated, and the relevant performance of the offshore platform of the offshore wind power flexible DC transmission system is verified.

Further, the method for charging the sub-module capacitor of the offshore platform converter valve through the test power supply of the offshore base wharf includes:

Determine whether the charging circuit of the converter valve on the offshore platform is the AC side charging circuit or the DC side charging circuit;

In the stage of uncontrolled charging, control the AC side voltage or DC side voltage of the converter valve to rise from 0 to the rated value according to the preset first rate;

In the active charging phase, the sub-modules controlling the converter valves are cut off sequentially at a preset second rate, so that the capacitor voltage of each sub-module rises to a rated value at a preset third rate.

Further, the charging circuit on the AC side refers to: the test power supply of the marine engineering base wharf is connected to the AC side of the converter valve through the incoming line protection switch cabinet, the voltage regulating transformer, the station transformer and the connection transformer in sequence, and the AC line voltage is Single-arm sub-module charging.

Further, the DC side charging circuit refers to: the test power supply of the offshore engineering base wharf is connected to the DC side of the flexible DC converter valve through the incoming line protection switch cabinet, voltage regulating transformer, step-up transformer and voltage doubler rectifier in sequence, and the DC voltage is used to Charge the sub-modules of the upper and lower bridge arms of the same phase.

Further, the range of the preset first rate is 20%-30% U _N /minute, where U _N is a voltage rating.

Further, the preset second rate is 2-4 per second.

Further, the method of issuing a short-term unlocking command of the converter valve based on the open-loop control strategy, so that the converter valve on the offshore platform can complete the short-term unlocking operation by relying on the energy stored in the capacitor of the sub-module, includes:

The pole control system adopts an open-loop control strategy to send a preset voltage reference wave to the valve control system of the converter valve, and the valve control system conducts on and off control of the sub-module IGBT to track the voltage reference wave;

The extreme control system sends a blocking command to the converter valve, disconnects the corresponding isolating switch, and closes the grounding switch.

Further, the preset test criteria include:

a. The AC voltage waveform output by the converter valve is consistent with the preset voltage reference wave issued by the extreme control system;

b. The capacitor voltage of the sub-module of the converter valve is balanced, the power supply of the sub-module is normal, there is no fault information of the sub-module, and there is no black module;

c. There is no protection trip, no abnormal discharge, no arrester action, and no abnormality in the control system.

In the second aspect, the present invention provides a passive unlocking test system for a converter valve wharf on an offshore platform, including:

The charging module is used to charge the sub-module capacitor of the offshore platform converter valve through the test power supply of the offshore base wharf, and disconnect the wiring switch between the test power supply and the offshore platform converter valve after charging is completed;

The short-time unlocking module is used to issue a short-time unlocking command for the converter valve based on the open-loop control strategy, so that the offshore platform converter valve can complete the short-term unlocking operation by relying on the energy stored in the capacitor of the sub-module;

The test discrimination module is used to discriminate the operation data during the short-term unlocking operation of the offshore platform converter valve based on the preset test criteria, and to verify the relevant performance of the offshore wind power flexible DC transmission system offshore platform.

The present invention has the following advantages due to the adoption of the above technical scheme:

1. The invention realizes the friendly charging and safe unlocking of the high-voltage and high-power converter valve through the low-voltage and small-capacity test power supply of the offshore engineering base, so as to realize the basic The comprehensive verification of functions can effectively avoid the high repair cost of offshore converter platforms, and has great practical value and broad application prospects;

2. The present invention reasonably verifies the data during the short-term unlocking operation period of the converter valve on the offshore platform through the test criterion, and realizes the extreme control performance, valve control performance, extreme control and valve control interface of the converter valve on the offshore platform and insulation performance, etc. are fully verified;

Therefore, the present invention can be widely used in the field of on-site commissioning of offshore wind power transmission systems through flexible direct current.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiment. The drawings are only for the purpose of illustrating a preferred embodiment and are not to be considered as limiting the invention. Throughout the drawings, the same reference numerals are used to refer to the same parts. In the attached picture:

Fig. 1 is a flow chart of a test method for passive unlocking of a converter valve dock on an offshore platform provided by an embodiment of the present invention;

Fig. 2 is a schematic circuit diagram of charging the AC side of the converter valve on the offshore converter platform provided by the embodiment of the present invention through a low-voltage, small-capacity power supply;

Fig. 3 is a schematic circuit diagram of charging the DC side of the converter valve on the offshore converter platform provided by the embodiment of the present invention through a low-voltage, small-capacity power supply;

Fig. 4 is a schematic diagram of the open-loop control strategy adopted by the extreme control system during the passive unlocking process of the converter valve in the embodiment of the present invention;

Fig. 5 is the voltage reference waves U _refa , U _refb , U _refc issued by the pole control system and the AC voltage U _va , U _vb , U _vc output by the converter valve during the passive unlocking period of the converter valve in the embodiment of the present invention. comparison chart;

The reference signs in the figure are as follows:

1. Test power supply; 2. Protection switchgear; 3. Regulating transformer; 4. Station transformer; 5. Connecting transformer; 6. Converter valve; 7. Step-up transformer; 8. Voltage doubler rectifier.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the following will clearly and completely describe the technical solutions of the embodiments of the present invention in conjunction with the drawings of the embodiments of the present invention. Apparently, the described embodiments are some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention belong to the protection scope of the present invention.

It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

In some embodiments of the present invention, a test method for passive unlocking of a converter valve wharf on an offshore platform is provided. The low-voltage, small-capacity test power supply of the offshore base wharf is used to charge the converter valve on the AC side or the DC side, and at the same time By controlling the voltage regulator and limiting the active charging cut-off speed of the sub-module to avoid the charging power of the converter valve exceeding the limit; after the charging is completed, disconnect the test power inlet switch, and issue a short-term unlock command of the converter valve based on the open-loop control strategy. Make the converter valve rely on the energy stored in the sub-module capacitor to complete the short-term unlocking operation; finally, by judging the consistency between the output AC voltage waveform of the converter valve and the reference wave sent by the extreme control system, etc., the flexible DC transmission system of offshore wind power The extreme control performance, valve control performance, extreme control and valve control interface, and insulation performance of the offshore platform are fully verified.

Correspondingly, in some other embodiments of the present invention, a passive unlocking test system for a diverter valve dock on an offshore platform is also provided.

Example 1

As shown in Figure 1, this embodiment provides a test method for passive unlocking of a converter valve wharf on an offshore platform, which includes the following steps:

1) Charge the sub-module capacitor of the offshore platform converter valve through the low-voltage, small-capacity test power supply at the dock of the offshore engineering base, and disconnect the wiring switch between the test power supply and the offshore platform converter valve after charging is completed;

2) Based on the open-loop control strategy, a short-term unlocking command of the converter valve is issued, so that the converter valve can complete the short-term unlocking operation relying on the energy stored in the capacitor of the sub-module;

3) Based on the preset test criteria, the data collected during the short-term unlocking operation of the converter valve is discriminated, and the extreme control performance, valve control performance, pole control and valve control interface, and insulation performance of the flexible DC offshore platform are fully verified. .

Preferably, in the above step 1), the method of charging the sub-module capacitor of the offshore platform converter valve through the low-voltage, small-capacity test power supply of the offshore base wharf includes the following steps:

1.1) According to the actual situation, the charging circuit of the converter valve on the offshore platform is determined to be the charging circuit on the AC side or the charging circuit on the DC side, and the AC or The DC incoming switch is turned on.

As shown in Figure 2, when the charging circuit adopts the AC side charging circuit, the low-voltage and small-capacity test power supply of the offshore base wharf passes through the configured incoming line protection switch cabinet, voltage regulating transformer, station transformer and connection transformer in sequence. The AC side of the converter valve is connected to charge the single-leg sub-module of the converter valve with the AC line voltage.

As shown in Figure 3, when the charging circuit adopts the DC side charging circuit, the low-voltage and small-capacity test power supply of the offshore base wharf passes through the incoming line protection switch cabinet, voltage regulating transformer, step-up transformer, voltage doubler rectifier and commutator in sequence. The DC side of the valve is connected, so that the DC voltage is used to charge the sub-modules of the same-phase upper and lower bridge arms of the converter valve.

Specifically, in Figures 2 and 3, u _pa is the phase a voltage of the upper bridge arm of the converter valve, u _pb is the phase b voltage of the upper bridge arm of the converter valve, u _pc is the phase c voltage of the upper bridge arm of the converter valve, i _pa is the a-phase current of the upper bridge arm of the converter valve, i _pb is the b-phase current of the upper bridge arm of the converter valve, i _pc is the c-phase current of the upper bridge arm of the converter valve, I _dc is the system DC current, and i _va is the connection transformer Current of phase a on the valve side, i _vb is the current of phase b on the valve side of the connecting transformer, i _vc is the current of phase c on the valve side of the connecting transformer, u _ca is the voltage between phase a and phase c on the valve side of the connecting transformer, u _ab is the valve side b of the connecting transformer The voltage between phase a and phase a, u _bc is the voltage between phase c and phase b on the valve side of the connecting transformer, u _na is the voltage of phase a of the lower bridge arm of the converter valve, u _nb is the voltage of phase b of the lower bridge arm of the converter valve, and u _nc is the voltage of the converter The phase c voltage of the lower bridge arm of the converter valve, i _na is the a-phase current of the lower bridge arm of the converter valve, i _nb is the b-phase current of the lower bridge arm of the converter valve, i _nc is the c-phase current of the lower bridge arm of the converter valve, U _dc is the flexible DC inter-electrode voltage.

1.2) In the stage of uncontrolled charging, by controlling the voltage regulating transformer, the AC side voltage or DC side voltage of the converter valve starts from 0 to the rated value according to the preset first rate, so as to avoid the charging power exceeding the test power supply capacity and causing the incoming line protection Switchgear jumps open.

Wherein, the preset first rate is selected according to actual needs, and the preferred range is 20%-30% U _N /minute, where U _N is a voltage rating.

1.3) In the active charging stage, by controlling the sub-modules of the converter valve to be removed in turn at the preset second rate, the capacitor voltage of each sub-module rises to the rated value at the preset third rate, thereby avoiding the charging power exceeding the test power supply capacity As a result, the incoming line protection switchgear tripped.

Wherein, the preset second rate is selected according to actual needs, for example, it may be 2-4 per second.

1.4) After the charging process is completed, disconnect the AC or DC incoming line switch between the low-voltage, small-capacity test power supply and the offshore platform converter valve.

Preferably, in the above step 2), when the converter valve on the offshore platform is disconnected from the low-voltage, small-capacity test power supply of the offshore base wharf, a short-term unlock command is sent to the converter valve through the extreme control system to make the converter The flow valve relies on the energy stored in the capacitor of the sub-module to complete the short-term unlocking operation. The specific operation method is as follows:

2.1) The pole control system adopts an open-loop control strategy to send a preset voltage reference wave to the valve control system of the converter valve. The valve control system conducts on and off control of the IGBT in the converter valve sub-module to track the voltage reference Wave.

As shown in Figure 4, in the open-loop control strategy, U _vq is the equivalent q-axis component of the valve side voltage of the connected transformer, U _vd is the equivalent d-axis component of the valve side voltage of the connected transformer, and f is the system frequency; for U _vq and U After _vd performs coordinate system conversion, the voltage reference waves U _refa , U _refb , and U _refc sent from the extreme control system to the valve control system are obtained.

2.2) The extreme control system sends a blocking command to the converter valve, disconnects the corresponding isolation switch, closes the grounding switch, and the converter valve enters short-term unlocking.

Preferably, in the above step 3), the preset test criteria include:

a. The AC voltage waveform output by the converter valve is consistent with the voltage reference wave issued by the pole control system;

b. The capacitor voltage of the sub-module of the converter valve is balanced, the power supply of the sub-module is normal, there is no fault information of the sub-module, and there is no black module;

c. There is no protection trip, no abnormal discharge, no arrester action, and no abnormality in the control system.

Example 2

In order to further verify the effectiveness and feasibility of Embodiment 1, Embodiment 1 is further explained through this embodiment: a flexible DC converter valve with a DC voltage of ±400kV is built in the power system electromagnetic transient simulation software through low voltage, The simulation model of small-capacity power supply for DC side charging, set the test power supply capacity to 5MVA, limit the DC voltage rise rate to 3kV/s by controlling the voltage regulating transformer, and limit the removal speed of the converter valve sub-module to 1/500ms in the active charging stage. After the charging is completed, disconnect the test power supply, and issue a 500ms passive unlock command to the converter valve.

As shown in Figure 5, during the passive unlocking period of the converter valve, the voltage reference waves U _refa , U _refb , and U _refc issued by the pole control system are consistent with the waveforms of the AC voltages U _va , U _vb , and U _vc output by the converter valve. It shows that the pole control, valve control and their interface functions are good, and the insulation performance of the equipment has also been verified in this process.

This example shows that the test method for passive unlocking of the offshore platform converter valve wharf proposed by the present invention can use the low-voltage, small-capacity test power supply of the offshore base to realize friendly charging and safe unlocking of the high-voltage, high-power converter valve , in order to realize the comprehensive verification of the basic functions of the offshore converter platform before it goes to the offshore site, and effectively avoid the high repair cost of the offshore converter platform, which has great practical value and broad application prospects.

Example 3

The above-mentioned embodiment 1 provides a test method for passive unlocking of a converter valve wharf on an offshore platform. Correspondingly, this embodiment provides a test system for passive unlocking of a converter valve wharf on an offshore platform. The system provided in this embodiment can implement the test method for passive unlocking of the offshore platform converter valve wharf in Embodiment 1, and the system can be realized by software, hardware or a combination of software and hardware. For example, the system may include integrated or separate functional modules or functional units to execute corresponding steps in the methods of Embodiment 1. Since the system of this embodiment is basically similar to the method embodiment, the description process of this embodiment is relatively simple. For relevant information, please refer to the part of the description of Embodiment 1. The embodiment of the system provided by this embodiment is only illustrative .

This embodiment provides a passive unlocking test system for a converter valve dock on an offshore platform, including:

The charging module is used to charge the converter valve on the offshore platform through the low-voltage, small-capacity test power supply at the dock of the offshore engineering base, and disconnect the wiring switch of the test power supply after charging is completed;

The unlocking module is used to issue a short-term unlocking command of the converter valve based on the open-loop control strategy, so that the converter valve can complete the short-term unlocking operation by relying on the energy stored in the capacitor of the sub-module;

The test discrimination module is used to discriminate the data during the unlocking operation based on the preset test criteria, and fully verify the extreme control performance, valve control performance, pole control and valve control interface, and insulation performance of the flexible DC offshore platform.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; 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 various embodiments of the present invention.

Claims (4)

1. A passive unlocking test method for an offshore platform converter valve wharf is characterized by comprising the following steps:

charging a sub-module capacitor of the offshore platform converter valve through a test power supply at a dock of the marine foundation, and disconnecting a wiring switch between the test power supply and the offshore platform converter valve after the charging is finished;

the method for charging the sub-module capacitor of the converter valve of the offshore platform through the test power supply of the marine base wharf comprises the following steps:

determining a charging loop of the converter valve of the offshore platform as an alternating current side charging loop or a direct current side charging loop; wherein, the alternating current side charging circuit is as follows: a test power supply of the marine foundation wharf is connected with the alternating current side of the converter valve through an incoming line protection switch cabinet, a voltage regulating transformer, a station transformer and a connecting transformer in sequence, and the single-bridge-arm submodule is charged by using the alternating current line voltage; the direct current side charging loop is as follows: a test power supply of the marine foundation wharf is connected with the direct current side of the flexible direct current converter valve through an incoming line protection switch cabinet, a voltage regulating transformer, a boosting transformer and a voltage doubling rectifier in sequence, and the same-phase upper and lower bridge arm sub-modules are charged by using direct current voltage;

in the uncontrolled charging stage, controlling the voltage of the alternating current side or the voltage of the direct current side of the converter valve to rise to a rated value from 0 according to a preset first rate;

in the active charging stage, each submodule of the converter valve is controlled to be sequentially cut off at a preset second speed in a rotation mode, and the capacitor voltage of each submodule is increased to a rated value according to a preset third speed;

issuing a converter valve short-time unlocking command based on an open-loop control strategy to enable the offshore platform converter valve to finish short-time unlocking operation by means of energy stored in the sub-module capacitor;

the method for issuing the converter valve short-time unlocking command based on the open-loop control strategy to enable the offshore platform converter valve to finish short-time unlocking operation by means of energy stored in the sub-module capacitor comprises the following steps:

the pole control system adopts an open-loop control strategy, a preset voltage reference wave is issued to the converter valve control system, and the valve control system conducts on and off control on the submodule IGBT to track the voltage reference wave;

the pole control system sends a locking command to the converter valve, corresponding isolating switches are disconnected, and grounding switches are connected;

judging operation data of the offshore platform converter valve during short-time unlocking operation based on preset test criteria, and verifying relevant performance of an offshore platform of the open-sea wind power flexible direct current sending-out system;

the preset test criteria comprise:

a. the AC voltage waveform output by the converter valve is consistent with a preset voltage reference wave issued by a pole control system;

b. the voltage of the capacitor of the converter valve submodule is balanced, the submodule power supply can be normally obtained, no submodule fault information exists, and no black module exists;

c. no protection tripping, no abnormal discharge, no lightning arrester action and no abnormality of a control system.

2. The passive unlocking test method for the converter valve wharf of the offshore platform according to claim 1, characterized by comprising the following steps: the preset first rate is in a range of 20% -30% U_NMinute, U_NIs the voltage rating.

3. The passive unlocking test method for the converter valve wharf of the offshore platform according to claim 1, characterized by comprising the following steps: the preset second rate is 2-4/sec.

4. The utility model provides a passive unblock test system of offshore platform converter valve pier which characterized in that includes:

the charging module is used for charging the sub-module capacitor of the offshore platform converter valve through the test power supply at the dock of the marine foundation and disconnecting a wiring switch between the test power supply and the offshore platform converter valve after charging is finished; wherein, when the test power through marine base pier charges to the submodule piece electric capacity of offshore platform converter valve, include: determining a charging loop of the converter valve of the offshore platform as an alternating current side charging loop or a direct current side charging loop; wherein, the alternating current side charging circuit means: a test power supply of the marine foundation wharf is connected with the alternating current side of the converter valve through an incoming line protection switch cabinet, a voltage regulating transformer, a station transformer and a connecting transformer in sequence, and the single-bridge-arm submodule is charged by using the alternating current line voltage; the direct current side charging loop is as follows: a test power supply of the marine foundation wharf is connected with the direct current side of the flexible direct current converter valve through an incoming line protection switch cabinet, a voltage regulating transformer, a boosting transformer and a voltage doubling rectifier in sequence, and the same-phase upper and lower bridge arm sub-modules are charged by using direct current voltage; in the uncontrolled charging stage, controlling the voltage of the alternating current side or the voltage of the direct current side of the converter valve to rise to a rated value from 0 according to a preset first rate; in the active charging stage, controlling each submodule of the converter valve to be sequentially cut off at a preset second rate in turn, and enabling the capacitor voltage of each submodule to rise to a rated value according to a preset third rate;

the short-time unlocking module is used for issuing a converter valve short-time unlocking command based on an open-loop control strategy so that the offshore platform converter valve can finish short-time unlocking operation by means of energy stored in the sub-module capacitor; the method comprises the following steps:

the pole control system adopts an open-loop control strategy, a preset voltage reference wave is issued to the converter valve control system, and the valve control system conducts and turns off control on the submodule IGBT to track the voltage reference wave;

the pole control system sends a locking command to the converter valve, corresponding isolating switches are disconnected, and grounding switches are connected;

the test judging module is used for judging operation data of the offshore platform converter valve during short-time unlocking operation based on preset test criteria and verifying the relevant performance of the offshore platform of the open-sea wind power flexible direct current sending system;

the preset test criteria comprise:

a. the AC voltage waveform output by the converter valve is consistent with a preset voltage reference wave issued by the pole control system;

b. the voltage of the capacitor of the converter valve submodule is balanced, the submodule power supply can be normally obtained, no submodule fault information exists, and no black module exists;

c. no protection tripping, no abnormal discharge, no lightning arrester action and no abnormality of a control system.

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