Protection method of flexible direct current submodule, valve control device of converter valve and converter station

Abstract

The invention discloses a protection method of a flexible direct current submodule, a valve control device of a converter valve and a converter station, and relates to the technical field of testing, and the method comprises the steps: in the starting process of the converter valve, if there is a submodule which cannot communicate, controlling the converter valve to be locked; after the converter valve starts to operate, judging whether the sub-module breaks down or not according to the working parameters; if the sub-module has a fault which affects the operation of the converter valve, disconnecting the converter valve from the three-phase alternating current power grid and the direct current power grid; and when the sub-module has a fault influencing the sub-module, the sub-module is controlled to be locked. And if a communication fault determines that the sub-module has a risk during working, the converter valve is locked and is not allowed to work. When a fault affecting operation of the converter valve occurs, connection with a power grid is disconnected in time, so that fault processing is facilitated. And if the fault of the sub-module only affects the operation of the sub-module, the sub-module is disconnected, and the work of the converter valve is not affected. Different protection strategies are adopted for faults of the sub-modules, and the working stability and reliability of the converter valve are improved.

Description

Technical Field

[0001] The present invention relates to the field of testing technology, and in particular to a protection method for a flexible direct current submodule, a valve control device for a converter valve, and a converter station. Background Art

[0002] The converter station is composed of converter valves, circuit breakers and other related electrical equipment. In the converter station, the converter valve is the key equipment to complete the conversion between AC and DC. It converts the three-phase AC voltage in sequence to obtain the desired DC voltage and realizes the control of the DC end power. Multiple submodules constitute the converter valve. The submodule is the basic component unit of the converter valve. The failure of the submodule will directly affect the operation of the converter valve. Therefore, it is necessary to effectively protect the submodule to improve the reliability of the converter valve operation. Summary of the invention

[0003] The purpose of the present invention is to provide a protection method for a flexible direct current submodule, a valve control device for a converter valve and a converter station, which adopt different protection strategies for submodule failures and improve the working stability and reliability of the converter valve.

[0004] In order to solve the above technical problems, the present invention provides a protection method for a flexible direct current submodule, which is applied to a valve control device of a converter valve, wherein the converter valve also includes a three-phase bridge arm, which corresponds to the phase of the three-phase alternating current one by one, and the first end of the upper bridge arm of each phase is connected to the positive pole of the DC power grid, the second end of the upper bridge arm of each phase is connected to the first end of the lower bridge arm of the corresponding phase, and the common end of the connection is connected to the corresponding phase of the three-phase power grid, and the second end of the lower bridge arm of the corresponding phase is connected to the negative pole of the DC power grid, and the upper bridge arm and the lower bridge arm are both composed of a plurality of submodules connected in series, and each of the submodules is connected to the valve control device;

[0005] The protection method of the flexible direct submodule comprises:

[0006] During the start-up of the converter valve, if there is a submodule that cannot communicate, the converter valve is controlled to be prohibited from being unlocked;

[0007] After the converter valve starts to operate, the operating parameters of each submodule are collected, wherein the operating parameters include at least one of the voltage output by the submodule, the state detection signal and the communication state, and the state detection signal is the voltage across the control device and the power supply device in the submodule, the Vce voltage and the switching frequency of the IGBT in the submodule;

[0008] Determine whether each of the submodules fails according to the working parameters;

[0009] When a submodule fails and affects the operation of the converter valve, disconnecting the converter valve from the three-phase AC power grid and the DC power grid;

[0010] When a submodule has a fault that affects itself, the submodule having the fault that affects itself is controlled to be locked.

[0011] On the other hand, the converter valve further comprises a pole control device, and the pole control device is connected to the valve control device;

[0012] During the start-up of the converter valve, if there is a submodule that cannot communicate, the method further includes:

[0013] Generate a first protection signal and send it to the pole control device;

[0014] When receiving the unlocking prohibition signal generated by the pole control device based on the first protection signal, the step of controlling the converter valve to be locked is entered.

[0015] On the other hand, judging whether each of the submodules fails according to the working parameters includes:

[0016] For any submodule, when the voltage output by the submodule in the working parameters is not within a preset voltage range and / or the submodule state detection voltage and communication state in the working parameters are not within a preset range, it is determined that the submodule fails.

[0017] On the other hand, when a submodule fails and affects the operation of the converter valve, disconnecting the converter valve from the three-phase AC power grid and the DC power grid includes:

[0018] When the bypass switch of the submodule refuses to operate or the number of submodules with faults in the converter valve exceeds a preset number, it is determined that the submodule has a fault that affects the operation of the converter valve, and the connection between the converter valve and the three-phase AC power grid and the DC power grid is disconnected;

[0019] The first end of the bypass switch serves as the input end of the submodule, the second end of the bypass switch serves as the output end of the submodule, and the bypass switch is used to lock the submodule when it is turned on.

[0020] On the other hand, the converter valve further comprises a pole control device, and the pole control device is connected to the valve control device;

[0021] After a submodule fails and the failure affects the operation of the converter valve, the method further includes:

[0022] generating a second protection signal and sending it to the pole control device;

[0023] receiving a locking signal, a DC circuit breaker disconnection signal, an AC circuit breaker disconnection signal, and a pole isolation triggering command signal sent by the pole control device based on the second protection signal;

[0024] Disconnecting the connection between the converter valve and the three-phase AC power grid and the DC power grid includes:

[0025] The converter valve is locked based on the locking signal, the DC circuit breaker between the converter valve and the DC power grid is disconnected based on the DC circuit breaker disconnection signal, the AC circuit breaker between the converter valve and the three-phase AC power grid is disconnected based on the AC circuit breaker disconnection signal, and the converter valve is isolated based on the trigger pole isolation command signal.

[0026] On the other hand, when a submodule has a fault that affects itself, controlling the submodule having the fault that affects itself to be locked includes:

[0027] When a fault occurs in the submodule and the fault does not affect the operation of the converter valve, it is determined that a fault that affects the submodule itself occurs, and the submodule is controlled to be locked.

[0028] On the other hand, the converter valve further comprises a pole control device, and the pole control device is connected to the valve control device;

[0029] After a submodule has a fault that affects itself, the following also occur:

[0030] generating a third protection signal and sending it to the pole control device;

[0031] receiving a submodule bypass command signal sent by the pole control device based on the third protection signal;

[0032] Controlling the submodule that has a fault affecting itself to be locked, comprising:

[0033] The bypass switch in the control submodule is closed;

[0034] The first end of the bypass switch serves as the input end of the submodule, the second end of the bypass switch serves as the output end of the submodule, and the bypass switch is used to lock the submodule when it is turned on.

[0035] On the other hand, the submodule includes a primary device and a secondary device, the primary device includes a first controllable switch, a second controllable switch, a thyristor, a bypass switch, a capacitor and a voltage-equalizing resistor, the secondary device includes a control device and a power supply device, the first end of the bypass switch serves as the input end of the submodule, the second end of the bypass switch serves as the output end of the submodule, the thyristor is connected in parallel with the bypass switch, the control end of the first controllable switch, the control end of the second controllable switch and the control end of the bypass switch are all connected to the control device, the first end of the first controllable switch is respectively connected to the first end of the capacitor and the first end of the voltage-equalizing resistor, the second end of the first controllable switch is connected to the first end of the second controllable switch and the common end of the connection is connected to the first end of the bypass switch, the second section of the second controllable switch is respectively connected to the first end of the capacitor and the first end of the voltage-equalizing resistor, and the power supply device is connected to the power supply end of the control device;

[0036] During the process of starting the converter valve, if there is a submodule that cannot communicate, controlling the converter valve to prohibit unlocking includes:

[0037] During the start-up of the converter valve, if communication data of the control device in the submodule cannot be received, it is determined that the submodule has a communication failure, and the converter valve is controlled to be prohibited from being unlocked;

[0038] When a submodule has a fault that affects itself, controlling the submodule having the fault that affects itself to be locked includes:

[0039] When a fault occurs in the submodule that affects itself, the bypass switch of the submodule that has the fault is controlled to be closed.

[0040] In order to solve the above technical problems, the present invention further provides a valve control device for a converter valve, comprising:

[0041] Memory for storing computer programs;

[0042] The processor is used to implement the steps of the above-mentioned flexible direct current submodule protection method when executing the computer program.

[0043] In order to solve the above technical problems, the present invention further provides a converter station, comprising a converter valve, a DC circuit breaker and an AC circuit breaker;

[0044] The converter valve includes the valve control device and three-phase bridge arm of the converter valve, which correspond to the phases of the three-phase alternating current one by one. The first end of the upper bridge arm of each phase is connected to the positive pole of the DC power grid, the second end of the upper bridge arm of each phase is connected to the first end of the lower bridge arm of the corresponding phase, and the common end of the connections is connected to the corresponding phase of the three-phase power grid, and the second end of the lower bridge arm of the corresponding phase is connected to the negative pole of the DC power grid. The upper bridge arm and the lower bridge arm are both composed of a plurality of submodules connected in series, and each of the submodules is connected to the valve control device;

[0045] The DC circuit breaker is arranged between the converter valve and the DC power grid, and the AC circuit breaker is arranged between the three-phase AC power grid and the converter valve.

[0046] The present application provides a protection method for a flexible direct current submodule, a valve control device for a converter valve, and a converter station, which relate to the field of testing technology, including controlling the converter valve to be locked if there is a submodule that cannot communicate during the start-up of the converter valve; collecting the working parameters of the submodule after the converter valve starts to operate; judging whether the submodule has a fault according to the working parameters; disconnecting the connection between the converter valve and the three-phase AC power grid and the DC power grid if there is a fault in the submodule that affects the operation of the converter valve; and controlling itself to be locked if there is a fault in the submodule that affects itself. If the communication fault determines the risk of the submodule working, the converter valve is locked and does not allow it to work. When a fault that affects the operation of the converter valve occurs, the connection with the power grid is disconnected in time to facilitate fault handling. If the fault of the submodule only affects its own operation, the submodule is disconnected and does not affect the operation of the converter valve. Different protection strategies are adopted for the faults of the submodule to improve the working stability and reliability of the converter valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0048] Figure 1 A flow chart of a protection method for a flexible direct current submodule provided by the present invention;

[0049] Figure 2 A schematic diagram of the structure of a converter valve provided by the present invention;

[0050] Figure 3 A schematic diagram of the structure of a flexible direct submodule provided by the present invention;

[0051] Figure 4 A control logic diagram of a valve control device and a pole control device provided by the present invention;

[0052] Figure 5 A schematic structural diagram of a valve control device of a converter valve provided by the present invention. DETAILED DESCRIPTION

[0053] The core of the present invention is to provide a protection method for a flexible direct current submodule, a valve control device for a converter valve and a converter station, which adopt different protection strategies for submodule failures and improve the working stability and reliability of the converter valve.

[0054] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] The submodule is the basic component of the converter valve, and the converter valve and related electrical equipment such as the circuit breaker constitute the converter station, that is, the substation. In the substation, the converter valve is the key equipment to complete the conversion between AC and DC. It converts the three-phase AC voltage in sequence to obtain the desired DC voltage and realizes the control of the DC end power. The failure of the submodule will directly affect the operation of the converter valve. Therefore, it is necessary to effectively protect the submodule to improve the reliability of the converter valve operation.

[0056] Figure 1 A flow chart of a protection method for a flexible direct current submodule provided by the present invention, wherein the protection method for the flexible direct current submodule is applied to a valve control device of a converter valve. Figure 2 A schematic diagram of the structure of a converter valve provided by the present invention, wherein the converter valve further comprises a three-phase bridge arm corresponding to the phase of the three-phase alternating current one by one, wherein the first end of the upper bridge arm of each phase is connected to the positive pole of the DC power grid, the second end of the upper bridge arm of each phase is connected to the first end of the lower bridge arm of the corresponding phase and the common end of the connection is connected to the corresponding phase of the three-phase power grid, the second end of the lower bridge arm of the corresponding phase is connected to the negative pole of the DC power grid, the upper bridge arm and the lower bridge arm are both composed of a plurality of submodules connected in series, and each submodule is connected to the valve control device;

[0057] Figure 2 SM1, SM2 and SMn are all submodules, and Ud is the voltage of the DC grid. A commutation reactor is also provided in the converter valve to play a role in current limiting.

[0058] The protection method of the flexible direct current submodule includes:

[0059] S11: During the start-up of the converter valve, if there is a submodule that cannot communicate, the converter valve is controlled to be prohibited from being unlocked;

[0060] The first type of fault: submodule black module fault. A fault state in the unlocking stage of the converter valve. When the information of the submodule cannot be sent to the valve control system, the information of the submodule is unknown, which is called a black module. When a black module exists, the converter valve is prohibited from unlocking.

[0061] This is because if there is a submodule that cannot communicate before starting the converter valve, it will be impossible to control and manage the submodule, which may easily cause subsequent failures. Therefore, at this time, the converter valve is controlled to be prohibited from being unlocked.

[0062] S12: After the converter valve starts to operate, collect the working parameters of each submodule, the working parameters include at least one of the voltage output by the submodule, the state detection signal and the communication state, the state detection signal is the voltage across the control device and the power supply device in the submodule, the Vce voltage and the switching frequency of the IGBT in the submodule;

[0063] S13: judging whether each submodule has a fault according to the working parameters;

[0064] The working parameters of the submodule can characterize the working status of the submodule. If the voltage is abnormal, it may be that the submodule has a fault. The subsequent protection strategy needs to be determined according to the type of fault. The purpose is to control the converter valve to stop working if a fault occurs, which affects the stability of the converter valve. The existence of some faults does not affect the overall operation of the converter valve, so it is necessary to determine the protection strategy according to the type of fault to achieve more accurate protection of the converter valve. The Vce voltage is the voltage between the collector and emitter of the IGBT.

[0065] S14: When a submodule fails and affects the operation of the converter valve, disconnect the converter valve from the three-phase AC grid and the DC grid;

[0066] If the fault affects the converter valve, then the converter valve needs to be removed from the power grid. At this time, the converter valve is still energized and needs to be actively stopped. The switches connecting the power grid on both sides of the converter valve need to be disconnected through control commands to isolate the converter valve for easy fault handling.

[0067] S15: When a submodule has a fault that affects itself, the submodule having the fault that affects itself is controlled to be locked.

[0068] This type of fault is determined to be able to be handled by bypass and will not affect the operation. After it occurs, the submodule can be bypassed through the bypass switch. At this time, it can be understood that the faulty submodule is removed from the system and will not affect the operation of the converter valve.

[0069] The present application provides a protection method for a flexible direct current submodule, which relates to the field of testing technology, including: during the start-up of the converter valve, if there is a submodule that cannot communicate, the converter valve is controlled to be locked; after the converter valve starts to operate, the working parameters of the submodule are collected; whether the submodule fails according to the working parameters; if there is a submodule failure that affects the operation of the converter valve, the connection between the converter valve and the three-phase AC power grid and the DC power grid is disconnected; if there is a submodule failure that affects itself, the submodule is controlled to lock itself. If the communication failure determines the risk of the submodule working, the converter valve lock is not allowed to work. When a fault that affects the operation of the converter valve occurs, the connection with the power grid is disconnected in time to facilitate fault handling. If the fault of the submodule only affects its own operation, the submodule is disconnected and does not affect the operation of the converter valve. Different protection strategies are adopted for the faults of the submodule to improve the working stability and reliability of the converter valve.

[0070] Based on the above embodiments:

[0071] In some embodiments, the converter valve further includes a pole control device, and the pole control device is connected to the valve control device;

[0072] During the start-up of the converter valve, if there is a submodule that cannot communicate, the following steps are also included:

[0073] Generate a first protection signal and send it to the pole control device;

[0074] When receiving the unlocking prohibition signal generated by the pole control device based on the first protection signal, the step of controlling the converter valve to prohibit unlocking is entered.

[0075] The pole control device is the upper control layer of the valve control device. The tripping and fault signals of the valve control device are sent to the pole control device. According to the fault type, the pole control device outputs the tripping signal. When the first type of fault occurs in the flexible direct current submodule, the valve control device generates a first protection signal corresponding to the first type of fault and sends it to the pole control device. The pole control device generates a prohibit unlocking signal based on the first protection signal.

[0076] The pole control device controls the converter valve to prohibit unlocking based on the unlock prohibition signal. The black module is a submodule in the state position during the unlocking process, and the valve control system cannot control it. If it is unlocked at this time, there is a risk of overpressure in the submodule, and the operating conditions of the converter valve cannot be met. Unlocking is prohibited at this time to prevent the scope of the fault from expanding.

[0077] In some embodiments, determining whether each submodule fails according to the operating parameters includes:

[0078] For any submodule, when the voltage output by the submodule in the working parameters is not within the preset voltage range and / or the state detection voltage and communication state of the submodule in the working parameters are not within the preset current range, it is determined that the submodule has failed.

[0079] The fault of the submodule is reflected by the change of the voltage signal detected in the module. The voltage has a corresponding working range. If the voltage or current is not in the working range, then it can be determined that the submodule has a fault, but the specific impact of the fault requires further judgment. The same is true for the status detection voltage and communication status.

[0080] In some embodiments, when a submodule fails and affects the operation of the converter valve, disconnecting the converter valve from the three-phase AC power grid and the DC power grid includes:

[0081] When the bypass switch of the submodule refuses to operate or the number of submodules with faults in the converter valve exceeds a preset number, it is determined that a submodule has a fault that affects the operation of the converter valve, and the connection between the converter valve and the three-phase AC power grid and the DC power grid is disconnected;

[0082] The first end of the bypass switch serves as the input end of the submodule, the second end of the bypass switch serves as the output end of the submodule, and the bypass switch is used to lock the submodule when it is turned on.

[0083] When a second type of fault occurs in the flexible direct current submodule, the valve control device generates a second protection signal corresponding to the second type of fault and sends it to the pole control device. The second type of fault includes bypass switch refusal to operate fault and submodule fault over-redundancy.

[0084] Specifically, the converter valve is divided into 6 bridge arms, each of which is composed of hundreds of sub-modules connected in series, some of which are redundant configurations. If the number of faulty sub-modules does not exceed the redundant number, the system can continue to operate, and will trip if the number exceeds the redundant number.

[0085] In some embodiments, the converter valve further includes a pole control device, and the pole control device is connected to the valve control device;

[0086] After a submodule failure occurs that affects the operation of the converter valve, the following also applies:

[0087] generating a second protection signal and sending it to the pole control device;

[0088] receiving a blocking signal, a DC circuit breaker disconnection signal, an AC circuit breaker disconnection signal and a trigger pole isolation command signal sent by the pole control device based on the second protection signal;

[0089] Disconnect the converter valve from the three-phase AC grid and the DC grid, including:

[0090] The converter valve is locked based on the locking signal, the DC circuit breaker between the converter valve and the DC grid is disconnected based on the DC circuit breaker disconnection signal, the AC circuit breaker between the converter valve and the three-phase AC grid is disconnected based on the AC circuit breaker disconnection signal, and the converter valve is isolated based on the trigger pole isolation command signal.

[0091] The pole control device generates a blocking lock signal, a disconnecting DC circuit breaker signal, a disconnecting AC circuit breaker signal and a triggering pole isolation command signal based on the second protection signal;

[0092] The pole control device controls the converter valve to lock based on the lock signal, disconnects the DC circuit breaker based on the disconnect DC circuit breaker signal, disconnects the AC circuit breaker based on the disconnect AC circuit breaker signal, and performs pole isolation based on the pole isolation command. The purpose is to handle the black module during power outage. When the black module exists, the converter valve is still energized. To handle the black module, it is necessary to actively stop the converter valve, disconnect the switches on both sides of the converter valve through control commands, and isolate the converter valve to facilitate fault handling.

[0093] In some embodiments, when a submodule has a fault that affects itself, controlling the submodule that has the fault that affects itself to be locked includes:

[0094] When a submodule fails and the failure does not affect the operation of the converter valve, it is determined that a failure that affects the submodule itself occurs, and the submodule is controlled to be locked.

[0095] When a third type of fault occurs in the flexible direct current submodule, the valve control device generates a third protection signal corresponding to the third type of fault, and the third type of fault includes all submodule faults except the first type of fault and the second type of fault;

[0096] In some embodiments, the converter valve further includes a pole control device, and the pole control device is connected to the valve control device;

[0097] After a submodule has a fault that affects itself, the following also occur:

[0098] generating a third protection signal and sending it to the pole control device;

[0099] receiving a submodule bypass command signal sent by the pole control device based on the third protection signal;

[0100] Control the submodules that have faults that affect themselves to lock out, including:

[0101] The bypass switch in the control submodule is closed;

[0102] The first end of the bypass switch serves as the input end of the submodule, the second end of the bypass switch serves as the output end of the submodule, and the bypass switch is used to lock the submodule when it is turned on.

[0103] The valve control device controls the converter valve flexible direct current submodule to perform bypass operation based on the submodule bypass command signal. Except for the black module, during operation, the submodule faults can be divided into two categories according to the results: one is the tripping fault, i.e. the first type of fault, and the other is the third type of fault that can be handled by bypass and does not affect the operation. After this type of fault occurs, the submodule can be bypassed through the bypass switch. At this time, it can be understood that the faulty submodule is removed from the system and will not affect the operation of the converter valve.

[0104] Figure 3 A schematic diagram of the structure of a flexible direct submodule provided by the present invention;

[0105] In some embodiments, the submodule includes a primary device and a secondary device, the primary device includes a first controllable switch IGBT1, a second controllable switch IGBT2, a thyristor SCR, a bypass switch K, a capacitor C and a voltage-equalizing resistor R, the secondary device includes a control device and a power supply device, the first end of the bypass switch K serves as the input end of the submodule, the second end of the bypass switch K serves as the output end of the submodule, the thyristor SCR is connected in parallel with the bypass switch K, the control end of the first controllable switch IGBT1, the control end of the second controllable switch IGBT2 and the control end of the bypass switch K are all connected to the control device, the first end of the first controllable switch IGBT1 is respectively connected to the first end of the capacitor C and the first end of the voltage-equalizing resistor, the second end of the first controllable switch IGBT1 is connected to the first end of the second controllable switch IGBT2 and the common end of the connection is connected to the first end of the bypass switch K, the second section of the second controllable switch IGBT2 is respectively connected to the first end of the capacitor C and the first end of the voltage-equalizing resistor, and the power supply device is connected to the power supply end of the control device;

[0106] During the start-up of the converter valve, if there is a submodule that cannot communicate, the converter valve is controlled to be prohibited from unlocking, including:

[0107] During the start-up of the converter valve, if there is a submodule that cannot receive the communication data of the control device, the converter valve is controlled to be prohibited from being unlocked;

[0108] When a submodule has a fault that affects itself, the submodule that has the fault that affects itself is controlled to be locked, including:

[0109] When a submodule has a fault that affects itself, the bypass switch K of the submodule having the fault that affects itself is controlled to be closed.

[0110] Capacitor C stores voltage, IGBT1 and IGBT2 are turned on and off, thyristor SCR always protects IGBT1 and IGBT2 when a fault occurs, bypass switch K bypasses the submodule when a fault occurs, the control device detects and controls the submodule, and the power supply provides energy for the submodule.

[0111] When the bypass switch is closed, the submodule will not convert the AC power.

[0112] Figure 4 A control logic diagram of a valve control device and a pole control device provided by the present invention;

[0113] The valve control device includes an information processing module H1 and a command execution module H2.

[0114] The pole control device includes an information processing module H3.

[0115] The valve control device information processing module H1 has three output terminals, two of which are connected to the input terminals of the pole control device. The first output terminal inputs the first protection signal generated when a first type of fault occurs in the converter valve submodule into the pole control device. The first type of fault includes a submodule black module fault. The second output terminal inputs the second protection signal generated when a second type of fault occurs in the converter valve submodule into the pole control device. The second type of fault includes a submodule bypass switch refusal to operate fault.

[0116] The third output terminal of the valve control device information processing module H1 is connected to the command execution module H2. The third output terminal inputs the third protection signal generated when the third type of fault occurs in the converter valve submodule into the command execution module H2. The third type of fault includes all faults except the first type of fault and the second type of fault.

[0117] Figure 5 The present invention provides a schematic structural diagram of a valve control device for a converter valve, wherein the valve control device for the converter valve comprises:

[0118] A memory 51, used for storing computer programs;

[0119] The processor 52 is configured to implement the steps of the above-mentioned flexible direct current submodule protection method when executing a computer program.

[0120] For an introduction to the valve control device of the converter valve provided in the present application, please refer to the above-mentioned embodiment, which will not be described in detail here.

[0121] The present invention also provides a converter station, comprising a converter valve, a DC circuit breaker and an AC circuit breaker;

[0122] The converter valve includes the valve control device and three-phase bridge arm of the above-mentioned converter valve, which correspond to the phases of the three-phase alternating current one by one, the first end of the upper bridge arm of each phase is connected to the positive pole of the DC power grid, the second end of the upper bridge arm of each phase is connected to the first end of the lower bridge arm of the corresponding phase, and the common end of the connections is connected to the corresponding phase of the three-phase power grid, the second end of the lower bridge arm of the corresponding phase is connected to the negative pole of the DC power grid, the upper bridge arm and the lower bridge arm are composed of a plurality of submodules connected in series, and each submodule is connected to the valve control device;

[0123] The DC circuit breaker is arranged between the converter valve and the DC power grid, and the AC circuit breaker is arranged between the three-phase AC power grid and the converter valve.

[0124] For the introduction of the converter station provided in this application, please refer to the above embodiments, which will not be repeated here.

[0125] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0126] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0127] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A protection method for a flexible direct current submodule, characterized in that: A valve control device applied to a converter valve, wherein the converter valve further comprises a three-phase bridge arm corresponding to the phases of the three-phase alternating current, wherein the first end of the upper bridge arm of each phase is connected to the positive pole of the DC power grid, the second end of the upper bridge arm of each phase is connected to the first end of the lower bridge arm of the corresponding phase, and the common end of the connections is connected to the corresponding phase of the three-phase power grid, and the second end of the lower bridge arm of the corresponding phase is connected to the negative pole of the DC power grid, wherein the upper bridge arm and the lower bridge arm are both composed of a plurality of submodules connected in series, and each of the submodules is connected to the valve control device; The protection method of the flexible direct submodule comprises: During the start-up of the converter valve, if there is a submodule that cannot communicate, controlling the converter valve to prohibit unlocking; After the converter valve starts to operate, the operating parameters of each submodule are collected, wherein the operating parameters include at least one of the voltage output by the submodule, the state detection signal and the communication state, and the state detection signal is the voltage across the control device and the power supply device in the submodule, the Vce voltage and the switching frequency of the IGBT in the submodule; Determine whether each of the submodules fails according to the working parameters; When a submodule fails and affects the operation of the converter valve, disconnecting the converter valve from the three-phase AC power grid and the DC power grid; When a submodule has a fault that affects itself, the submodule having the fault that affects itself is controlled to be locked.

2. The protection method of the flexible direct current submodule according to claim 1, characterized in that: The converter valve further comprises a pole control device, and the pole control device is connected to the valve control device; During the start-up of the converter valve, if there is a submodule that cannot communicate, the method further includes: Generate a first protection signal and send it to the pole control device; When receiving the unlocking prohibition signal generated by the pole control device based on the first protection signal, the step of controlling the converter valve to prohibit unlocking is entered.

3. The protection method of the flexible direct current submodule according to claim 1, characterized in that: Determining whether each of the submodules fails according to the working parameters includes: For any submodule, when the voltage output by the submodule is not within a preset voltage range and / or the state detection voltage and communication state of the submodule are not within a preset current range, it is determined that the submodule fails.

4. The protection method of the flexible direct current submodule according to claim 1, characterized in that: When a submodule fails and affects the operation of the converter valve, disconnecting the converter valve from the three-phase AC power grid and the DC power grid includes: When the bypass switch of the submodule refuses to operate or the number of submodules with faults in the converter valve exceeds a preset number, it is determined that the submodule has a fault that affects the operation of the converter valve, and the connection between the converter valve and the three-phase AC power grid and the DC power grid is disconnected; The first end of the bypass switch serves as the input end of the submodule, the second end of the bypass switch serves as the output end of the submodule, and the bypass switch is used to lock the submodule when it is turned on.

5. The protection method of the flexible direct current submodule according to claim 1, characterized in that: The converter valve further comprises a pole control device, and the pole control device is connected to the valve control device; After a submodule fails and the operation of the converter valve is affected, the method further includes: generating a second protection signal and sending it to the pole control device; receiving a blocking signal, a DC circuit breaker disconnection signal, an AC circuit breaker disconnection signal, and a pole isolation triggering command signal sent by the pole control device based on the second protection signal; Disconnecting the connection between the converter valve and the three-phase AC power grid and the DC power grid includes: The converter valve is locked based on the locking signal, the DC circuit breaker between the converter valve and the DC power grid is disconnected based on the DC circuit breaker disconnection signal, the AC circuit breaker between the converter valve and the three-phase AC power grid is disconnected based on the AC circuit breaker disconnection signal, and the converter valve is isolated based on the trigger pole isolation command signal.

6. The protection method of the flexible direct current submodule according to claim 1, characterized in that: When a submodule has a fault that affects itself, controlling the submodule having the fault that affects itself to be locked includes: When a fault occurs in the submodule and the fault does not affect the operation of the converter valve, it is determined that a fault that affects the submodule itself occurs, and the submodule is controlled to be locked.

7. The protection method of the flexible direct current submodule according to claim 1, characterized in that: The converter valve further comprises a pole control device, and the pole control device is connected to the valve control device; After a submodule has a fault that affects itself, the following also occur: generating a third protection signal and sending it to the pole control device; receiving a submodule bypass command signal sent by the pole control device based on the third protection signal; Controlling the submodule that has a fault affecting itself to be locked, comprising: The bypass switch in the control submodule is closed; The first end of the bypass switch serves as the input end of the submodule, the second end of the bypass switch serves as the output end of the submodule, and the bypass switch is used to lock the submodule when it is turned on.

8. The method for protecting a flexible direct current submodule according to any one of claims 1 to 7, characterized in that: The submodule includes a primary device and a secondary device, wherein the primary device includes a first controllable switch, a second controllable switch, a thyristor, a bypass switch, a capacitor and a voltage-equalizing resistor, and the secondary device includes a control device and a power supply device. The first end of the bypass switch serves as the input end of the submodule, and the second end of the bypass switch serves as the output end of the submodule. The thyristor is connected in parallel with the bypass switch. The control end of the first controllable switch, the control end of the second controllable switch and the control end of the bypass switch are all connected to the control device. The first end of the first controllable switch is respectively connected to the first end of the capacitor and the first end of the voltage-equalizing resistor. The second end of the first controllable switch is connected to the first end of the second controllable switch and the common end of the connections is connected to the first end of the bypass switch. The second section of the second controllable switch is respectively connected to the first end of the capacitor and the first end of the voltage-equalizing resistor, and the power supply device is connected to the power supply end of the control device. During the process of starting the converter valve, if there is a submodule that cannot communicate, controlling the converter valve to prohibit unlocking includes: During the start-up process of the converter valve, if there is a submodule that cannot receive the communication data of the control device, the converter valve is controlled to be prohibited from being unlocked; When a submodule has a fault that affects itself, controlling the submodule having the fault that affects itself to be locked includes: When a fault occurs in the submodule that affects itself, the bypass switch of the submodule that has the fault is controlled to be closed.

9. A valve control device for a converter valve, characterized in that: include: Memory for storing computer programs; A processor, configured to implement the steps of the flexible direct current submodule protection method according to any one of claims 1 to 8 when executing the computer program.

10. A converter station, characterized in that: Including converter valves, DC circuit breakers and AC circuit breakers; The converter valve comprises the valve control device and three-phase bridge arm of the converter valve as claimed in claim 9, which correspond to the phases of the three-phase alternating current one by one, the first end of the upper bridge arm of each phase is connected to the positive pole of the DC power grid, the second end of the upper bridge arm of each phase is connected to the first end of the lower bridge arm of the corresponding phase, and the common end of the connection is connected to the corresponding phase of the three-phase power grid, and the second end of the lower bridge arm of the corresponding phase is connected to the negative pole of the DC power grid, the upper bridge arm and the lower bridge arm are both composed of a plurality of submodules connected in series, and each of the submodules is connected to the valve control device; The DC circuit breaker is arranged between the converter valve and the DC power grid, and the AC circuit breaker is arranged between the three-phase AC power grid and the converter valve.

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