Overcurrent protection device and method for converter valve bridge arm, converter system

Abstract

This invention discloses a converter valve bridge arm overcurrent protection device and method, and a converter system. The device includes a main protection module and a backup protection module. The main protection module is located in the polar control layer, and the backup protection module is located in the valve control layer. The main protection module and the backup protection module communicate via optical fiber. Each of the main protection module and the backup protection module performs converter valve bridge arm overcurrent detection according to different detection methods. When the main protection module determines that overcurrent protection needs to be triggered, it sends a protection action command to the backup protection module. After the backup protection module determines that overcurrent protection needs to be triggered or receives the protection action command sent by the main protection module, it controls the corresponding converter valve to enter a locked state. Using this invention, coordinated protection of converter valve bridge arm overcurrent by main protection and backup protection can be achieved, improving reliability while ensuring speed of action.

Description

Technical Field

[0001] This invention relates to the field of high voltage direct current transmission, specifically to a converter valve bridge arm overcurrent protection device and method, and a converter system. Background Technology

[0002] In high-voltage direct current (HVDC) and flexible direct current (VSC-HVDC) systems, overcurrent protection of the converter valve arms is a crucial element in ensuring the safe and stable operation of the system. The F3C (Full-Controllable Composite Converter) converter valve, as a novel topology, offers advantages such as high current capacity, flexible reactive power adjustment, and no commutation failure. However, the rapid changes in its arm current and complex operating conditions place higher demands on the protection system.

[0003] Currently, overcurrent protection for converter valves mainly relies on control and protection systems. Typical solutions include low-setpoint fast main protection and high-setpoint backup protection. Low-setpoint fast main protection is implemented by a host computer, offering advantages such as high speed and rapid suppression of fault currents to prevent overcurrent damage to components. However, it is susceptible to interference from switching transients and power grid harmonics, leading to malfunctions and unnecessary system lockouts. High-setpoint backup protection typically involves hardware overcurrent protection within the valve control system, but with higher settings, it serves only as a last resort. Its slow response may cause components to endure prolonged thermal stress under fault current, reducing their lifespan. Furthermore, if the backup protection settings are not coordinated with the main protection settings, competing actions may occur, leading to chaotic protection logic.

[0004] Some studies attempt to optimize protection strategies, such as adding filtering algorithms to reduce noise interference, but this introduces additional computational delays and affects response speed. Others employ dual-set main protection redundancy to improve reliability, but this is costly and still fails to resolve the setting coordination issue. Existing solutions have not effectively addressed the core contradiction of "primary protection being prone to maloperation and backup protection responding slowly." Summary of the Invention

[0005] This invention provides a converter valve bridge arm overcurrent protection device and method, and a converter system, to achieve coordinated protection of the main protection and backup protection for converter valve bridge arm overcurrent, thereby improving reliability while ensuring speed of operation.

[0006] On one hand, embodiments of the present invention provide an overcurrent protection device for a converter valve bridge arm, comprising: a main protection module and a backup protection module, wherein the main protection module is disposed in the pole control layer and the backup protection module is disposed in the valve control layer; the main protection module and the backup protection module communicate with each other via optical fiber;

[0007] The main protection module and the backup protection module each perform real-time overcurrent detection of the converter valve bridge arm according to different detection methods.

[0008] When the main protection module determines that overcurrent protection needs to be triggered, it sends a protection action command to the backup protection module.

[0009] After the backup protection module determines that overcurrent protection needs to be triggered or receives a protection action command sent by the main protection module, it controls the corresponding converter valve to enter the lockout state.

[0010] Optionally, the main protection module includes: a current acquisition unit, an instantaneous value detection unit, an integral detection unit, and a communication unit;

[0011] The current acquisition unit is used to acquire the current signal of each bridge arm in real time and obtain the instantaneous sample value;

[0012] The instantaneous value detection unit is used to send a trigger signal to the integral detection unit when the instantaneous sampled value is greater than a first set value;

[0013] The integral detection unit is used to integrate the current signal of the bridge arm within a certain time window when the trigger signal is received to obtain an integral value; when the integral value is greater than the integral threshold dynamically determined based on the instantaneous sample value, it is determined that overcurrent protection needs to be triggered.

[0014] The communication unit is used to send the protection action command to the backup protection module when the integral detection unit determines that overcurrent protection needs to be triggered.

[0015] Optionally, the current acquisition unit includes a current sensor.

[0016] Optionally, the backup protection module includes: an analog signal acquisition unit, an analog quantity detection unit, a digital quantity detection unit, a logic judgment unit, and a control unit;

[0017] The analog signal acquisition unit is used to acquire analog voltage signals based on the current of each bridge arm in real time.

[0018] The analog quantity detection unit is used to perform bridge arm overcurrent detection based on the analog voltage signal itself and output a first detection result;

[0019] The digital quantity detection unit is used to perform bridge arm overcurrent detection based on the digital sampling signal obtained by analog-to-digital conversion of the analog voltage signal, and output a second detection result.

[0020] The logic judgment unit is used to determine that overcurrent protection needs to be triggered when both the first detection result and the second detection result indicate an overcurrent fault.

[0021] The control unit is used to control the corresponding converter valve to enter the lockout state after the logic judgment unit determines that overcurrent protection needs to be triggered or receives a protection action command sent by the main protection module.

[0022] Optionally, the analog quantity detection unit includes a comparator, one input terminal of which receives the analog voltage signal, and the other input terminal of which receives a reference voltage. When the analog voltage signal is greater than the reference voltage, the comparator outputs a first detection result indicating an overcurrent fault.

[0023] Optionally, the digital quantity detection unit includes:

[0024] An analog-to-digital converter is used to convert the analog voltage signal into a digital signal and output a digital sampling signal.

[0025] The digital delay verification unit is used to compare the sampled value of the digital sampling signal with a set voltage threshold. If the sampled value of the digital sampling signal is greater than the voltage threshold and continues for a set delay time, it outputs a second detection result indicating an overcurrent fault.

[0026] Optionally, the analog-to-digital converter, the digital delay verification unit, and the logic judgment unit are integrated in the same FPGA.

[0027] Optionally, the device further includes a voltage source for providing the reference voltage.

[0028] Optionally, the reference voltage output by the voltage source is an adjustable voltage.

[0029] Optionally, the range of the first set value is 1.0-2.0 pu, and the range of the current value corresponding to the voltage threshold is 1.5-3.0 pu.

[0030] Optionally, the delay time is configured by software.

[0031] On the other hand, embodiments of the present invention also provide a method for overcurrent protection of a converter valve bridge arm, the method comprising:

[0032] Set up a primary protection service at the polarity control layer and a backup protection service at the valve control layer;

[0033] The main protection service and the backup protection service each perform real-time overcurrent detection of the converter valve bridge arm according to different detection methods.

[0034] When the primary protection service determines that overcurrent protection needs to be triggered, it sends a protection action command to the backup protection service via a fiber optic channel.

[0035] After the backup protection service determines that overcurrent protection needs to be triggered or receives a protection action command sent by the main protection service, it controls the corresponding converter valve to enter the lockout state.

[0036] Optionally, the main protection service for converter valve bridge arm overcurrent detection includes:

[0037] The current signals of each bridge arm are acquired in real time to obtain instantaneous sampled values;

[0038] If the instantaneous sampled value of any bridge arm is greater than the first set value, the current signal of the bridge arm is integrated within a certain time window to obtain the integral value.

[0039] If the integral value is greater than the integral threshold dynamically determined based on the current signal, it is determined that overcurrent protection needs to be triggered, and the protection action command is sent to the backup protection service.

[0040] Optionally, the method further includes: determining the integration threshold based on a lookup table and / or function calculation using the instantaneous sampled value.

[0041] Optionally, the backup protection service for converter valve bridge arm overcurrent detection includes:

[0042] Real-time acquisition of analog voltage signals based on the current of each bridge arm;

[0043] Simultaneously, analog quantity detection and digital quantity detection are performed on the analog voltage signal to obtain a first detection result for the corresponding analog quantity detection and a second detection result for the corresponding digital quantity detection.

[0044] If both the first and second detection results indicate an overcurrent fault, it is determined that overcurrent protection needs to be triggered.

[0045] Optionally, the analog quantity detection of the analog pressure signal includes:

[0046] Compare the analog voltage signal with a preset reference voltage;

[0047] If the analog voltage signal is greater than the reference voltage, a first detection result indicating an overcurrent fault is output.

[0048] Optionally, the digital detection of the analog voltage signal includes:

[0049] The analog voltage signal is converted from analog to digital to output a digital sampling signal;

[0050] If the sampled value of the digital sampling signal is greater than a set voltage threshold and remains so for a set delay time, a second detection result indicating an overcurrent fault is output. On the other hand, embodiments of the present invention also provide a converter system, the system including a converter valve and the aforementioned converter valve bridge arm overcurrent protection device.

[0051] The converter valve bridge arm overcurrent protection device and method provided in this invention embodiment sets up a main protection at the pole control layer and a backup protection at the valve control layer. The main protection and the backup protection communicate through an optical fiber channel. The main protection and the backup protection each perform converter valve overcurrent detection according to different detection methods. The main protection is responsible for rapid detection and preliminary judgment of overcurrent faults, ensuring rapid response; the backup protection, as a redundant backup of the main protection, can provide a second layer of protection when the main protection fails. The main protection and the backup protection can achieve division of labor and cooperation through signal interaction and logical control of main protection priority and autonomous backup protection. Utilizing the advantages of high speed and electromagnetic interference resistance of optical fiber communication, the main protection and the backup protection can achieve real-time signal interaction, ensuring the reliability of signal interaction and thus ensuring strict timing coordination between the two, avoiding competition or protection blind spots.

[0052] Furthermore, the main protection can employ a dual judgment and verification mechanism, such as a detection method that combines setting value judgment with short-time integral verification. Setting value judgment can capture various abnormal upward trends in the current on the bridge arm in the first instance, identifying the initially suspected fault event; the initially suspected fault event is simultaneously confirmed by the energy characteristics determined by short-time integral verification before the main protection issues a protection action command. This effectively avoids misjudgments caused by interference or current sampling errors due to single setting value judgment, ensuring the accuracy of the judgment result.

[0053] Furthermore, backup protection can also employ a dual verification mechanism, such as using analog signal detection and parallel digital delay verification. Analog signal detection performs overcurrent detection by directly sampling the analog voltage signal on the bridge arm, while digital delay verification performs analog-to-digital conversion on the analog voltage signal on the bridge arm. Only when both analog and digital detection confirm an overcurrent fault will the backup protection determine that overcurrent protection needs to be triggered. Analog signal detection ensures rapid response under extreme fault conditions, while digital signal detection avoids misjudgments caused by normal switching transients and brief interference pulses, guaranteeing the accuracy of the judgment results.

[0054] The converter system provided in this embodiment of the invention utilizes a converter valve bridge arm overcurrent protection device. Through the division of labor and cooperation between the main protection and backup protection, it achieves coordinated protection of the main protection and backup protection for overcurrent of the converter valve bridge arm in the converter system. This improves reliability while ensuring speed of operation and effectively guarantees the safe operation of the converter system.

[0055] The present invention adopts a two-level protection configuration of polar control layer main protection and valve control layer backup protection, which greatly simplifies the redundancy of the configuration level. Furthermore, the main protection is located in the polar control layer, which greatly reduces the signal transmission delay and can achieve microsecond-level protection response. It also effectively improves the reliability of converter arm overcurrent protection. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of a converter valve bridge arm overcurrent protection device provided in an embodiment of the present invention;

[0057] Figure 2 This is a schematic diagram of the main protection module in one embodiment of the present invention;

[0058] Figure 3 This is a schematic diagram of a backup protection module in one embodiment of the present invention;

[0059] Figure 4 This is a flowchart of an overcurrent protection method for a converter valve bridge arm provided in this invention. Detailed Implementation

[0060] To make the above-mentioned objectives, features and beneficial effects of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0061] In HVDC and VSC-HVDC systems, the polar control layer and valve control layer are core modules in the hierarchical control system, each undertaking different control functions. The polar control layer is responsible for strategy formulation, while the valve control layer is responsible for rapid response at the execution level. Typically, the polar control layer is responsible for the high-level control and operation management of the entire converter station. The polar control system usually consists of a high-performance industrial computer or PLC, running complex control algorithms. The valve control layer directly controls the triggering or shutting down of the converter valves. The valve control system is the execution unit of the polar control system, typically using high-speed, high-reliability dedicated hardware, such as FPGA (Field Programmable Gate Array), to control the converter valves. The control cycle of the polar control layer is typically in the millisecond range, handling dynamic processes within the system. The control cycle of the valve control layer is typically in the microsecond range, handling instantaneous events within the power grid frequency cycle.

[0062] To address the higher demands placed on protection systems by rapid changes in converter valve arm current and complex operating conditions, and considering the shortcomings of traditional overcurrent protection schemes, this invention provides a converter valve arm overcurrent protection device and method. A primary protection layer is configured at the pole control layer, and a backup protection layer is configured at the valve control layer. The primary and backup protections communicate via a fiber optic channel. Through independent detection and signal interaction between the primary and backup protections, rapid and reliable overcurrent protection for the converter valve arm is achieved.

[0063] like Figure 1 The diagram shown is a structural schematic of a converter valve bridge arm overcurrent protection device provided in an embodiment of the present invention.

[0064] In this example, the converter valve bridge arm overcurrent protection device 100 includes: a main protection module 10 and a backup protection module 20. The main protection module 10 is located in the pole control layer, and the backup protection module 20 is located in the valve control layer. The main protection module 10 and the backup protection module 20 communicate with each other through an optical fiber 30.

[0065] The main protection module 10 and the backup protection module 20 each perform real-time overcurrent detection of the converter valve bridge arm according to different detection methods, and interact through the optical fiber 30 to achieve timing coordination and avoid competition or protection blind spots.

[0066] Specifically, when the main protection module 10 determines that overcurrent protection needs to be triggered, it sends a protection action command to the backup protection module 20. After the backup protection module 20 determines that overcurrent protection needs to be triggered based on its own detection results or receives the protection action command sent by the main protection module 10, it controls the corresponding converter valve to enter the lockout state.

[0067] In some embodiments, the main protection module 10 can employ a dual judgment and verification mechanism, which can use a detection method of setting value judgment plus short-time integral verification. The setting value judgment refers to comparing the real-time acquired bridge arm current value with a set current threshold. The short-time integral verification refers to integrating the bridge arm current signal within a certain time window to obtain an integral value, which is then used for comparison and judgment. For details on the detection method of setting value judgment plus short-time integral verification, please refer to the following... Figure 2 The illustrated embodiments will be described in detail.

[0068] like Figure 2 The diagram shown is a structural schematic of the main protection module in an embodiment of the present invention.

[0069] Simultaneously refer to Figure 1 and Figure 2 , Figure 2 In the illustrated embodiment, the main protection module 10 includes: a current acquisition unit 101, an instantaneous value detection unit 102, an integration detection unit 103, and a communication unit 104. Wherein,

[0070] The current acquisition unit 101 is used to acquire the current signal of each bridge arm in real time and obtain the instantaneous sample value. For example, a high-precision current sensor, such as a Rogowski coil or a fiber optic current transformer, can be used in conjunction with a corresponding fiber optic transmission and conditioning circuit to acquire the current signal of each bridge arm in real time and obtain the corresponding instantaneous sample value.

[0071] Furthermore, digital filtering algorithms can be used to filter the acquired current signal to suppress high-frequency noise.

[0072] The instantaneous value detection unit 102 is used to send a trigger signal to the integral detection unit 103 when the instantaneous sampled value is greater than the first set value.

[0073] Accordingly, the integration detection unit 103 is used to integrate the current signal of the corresponding bridge arm within a certain time window when it receives the trigger signal sent by the instantaneous value detection unit 102, and obtain the integral value; when the integral value is greater than the integration threshold dynamically determined based on the current signal, it is determined that overcurrent protection needs to be triggered.

[0074] In some embodiments, such as Figure 2 As shown, each bridge arm can be equipped with one of the aforementioned current acquisition unit 101, instantaneous value detection unit 102 and integral detection unit 103, thereby realizing overcurrent detection for each bridge arm.

[0075] Accordingly, the communication unit 104 is used to send a protection action command to the backup protection module 20 when the integration detection unit 103 of any channel determines that overcurrent protection needs to be triggered.

[0076] The instantaneous value detection unit 102 is designed to capture any abnormal upward trend of the bridge arm current as soon as possible, and provide an initial trigger signal for the entire protection system. For this purpose, the first set value can be selected to be a relatively low value, such as 1.0-2.0 pu. In specific applications, it can be set to 1.5 pu.

[0077] Accordingly, the integration detection unit 103 integrates the current signal of the corresponding bridge arm within a certain time window (for example, the length of the time window can be set to 10-50μs) to obtain the integral value; when the integral value is greater than the integration threshold dynamically determined based on the instantaneous sample value, it is determined that overcurrent protection needs to be triggered.

[0078] Unlike conventional simple integrators, the integration detection unit 103 in this embodiment of the invention is a verification unit that works in conjunction with the instantaneous sampled value and is based on a fault energy accumulation model. Its working principle is as follows: the integrator is activated within a very short variable time window only when the instantaneous sampled value is greater than a first set value. The integrator calculates the integral of the square value of the current within this time window, that is, the short-circuit thermal accumulation energy.

[0079] The integration threshold also dynamically changes based on the instantaneous sampled value obtained from the current sampling. For example, when the instantaneous current sampled value just exceeds 1.5 pu, a higher integration energy threshold is required, which corresponds to a larger integration threshold. If the instantaneous current value surges to over 2.5 pu, the integration energy threshold decreases accordingly, allowing for a smaller integration threshold. This design better aligns with the physical model of power electronic devices under thermal stress at different overcurrent levels: under high current, energy accumulation in a very short time can cause damage, requiring faster protection. In practical implementation, the integration threshold corresponding to the instantaneous sampled value can be obtained, for example, through table lookup and / or function calculation.

[0080] The energy of high-frequency noise has a very small integral value within an extremely short time window, while the actual fault current contains a large number of low-frequency components, and its energy integral value accumulates rapidly and exceeds the dynamic threshold. This energy-based distinction is more effective than conventional simple filtering algorithms in identifying "high-frequency noise" from "the low-frequency components of the actual fault." It not only has significantly better noise immunity than traditional filtering schemes, but also matches the protection characteristics with the thermal damage physical model of the device, achieving intelligent, adaptive μs-level high-speed protection.

[0081] In this embodiment of the invention, the main protection module 10 can detect various abnormal upward trends in the current on the bridge arm in the first instance through setpoint judgment, and determine the initially suspected fault event. Only when the initially suspected fault event is confirmed by the energy characteristics determined by short-time integration will a protection action command be issued. This effectively avoids misjudgment caused by interference or current sampling errors due to single setpoint judgment, ensuring the accuracy of the judgment result. Furthermore, after determining that overcurrent protection needs to be triggered, the main protection module 10 immediately sends a protection action command to the backup protection module 20 via optical fiber 30, instructing the backup protection module 20 to control the corresponding converter valve to enter the lockout state. Compared to the scheme of setting the main protection in the host computer, setting the main protection module in the polar control layer can effectively reduce the transmission link delay of the protection action command, making the main protection more rapid, and shortening the time from the issuance of the protection action command to the lockout of the converter valve to the μs level.

[0082] Considering that the polar control layer typically needs to run complex system control algorithms, the newly added protection functions must avoid burdening or conflicting the existing system. Therefore, a modular design can be used to encapsulate the functions of the main protection module into independent logical units, decoupling them from the polar control main program, thus ensuring the independence and priority of the protection functions.

[0083] In some embodiments, the backup protection module 20 may also employ a dual judgment and verification mechanism, such as a detection method that uses analog quantity detection and parallel digital quantity delay verification.

[0084] like Figure 3 The diagram shown is a structural schematic of a backup protection module in an embodiment of the present invention.

[0085] Simultaneously refer to Figure 1 and Figure 3 , Figure 3 In the illustrated embodiment, the backup protection module 20 includes: an analog signal acquisition unit 201, an analog quantity detection unit 202, a digital quantity detection unit 203, a logic judgment unit 204, and a control unit 205. Wherein:

[0086] The analog signal acquisition unit 201 is used to acquire analog voltage signals based on the current of each bridge arm in real time. For example, the corresponding analog voltage signals can be obtained through Rogowski coils, integrators (usually active integrators), LED drivers, fiber optic transmission systems, and photodetectors.

[0087] It should be noted that the analog signal acquisition unit 201 and Figure 2 The current acquisition unit 101 in the main protection module 10 shown can reuse some components or circuits, especially on the high-voltage side, it can be fully reused.

[0088] The analog signal detection unit 202 is used to perform bridge arm overcurrent detection based on the analog voltage signal itself and output the first detection result.

[0089] The digital quantity detection unit 203 is used to perform bridge arm overcurrent detection based on the digital sampling signal obtained by analog-to-digital conversion of the analog voltage signal, and output a second detection result.

[0090] The logic judgment unit 204 is used to determine that overcurrent protection needs to be triggered when both the first detection result and the second detection result indicate an overcurrent fault; for example, this judgment logic can be implemented by an AND gate.

[0091] The control unit 205 is used to control the corresponding converter valve to enter the lockout state after the logic judgment unit 204 determines that overcurrent protection needs to be triggered or receives a protection action command sent by the main protection module 10.

[0092] The analog quantity detection unit 202 and the digital quantity detection unit 203 detect the analog voltage signal in parallel. The corresponding detection can be completed by hardware circuit. Since the digital quantity detection unit needs to perform analog-to-digital conversion on the analog voltage signal, the digital quantity detection unit 203 performs a delay verification on the detection result of the analog quantity detection unit 202, which can better ensure the accuracy of the final detection result.

[0093] In some embodiments, the analog signal detection unit 202 can be implemented using a hardware-based comparator. One input of the comparator receives the analog voltage signal, and the other input receives a reference voltage. When the analog voltage signal exceeds the reference voltage, it outputs a first detection result indicating an overcurrent fault. The reference voltage can be provided by an external voltage source, which can provide a fixed voltage or an adjustable voltage; this is not limited in this embodiment. The comparator compares the analog voltage signal with the reference voltage in real time. Once the instantaneous value of the analog voltage signal exceeds a hardware preset value (i.e., the reference voltage), the comparator output immediately flips within nanoseconds (typically <100ns), generating a preliminary overcurrent fault indication signal, i.e., the first detection result indicating an overcurrent fault. This process is entirely executed by hardware, requiring no software involvement or digital processing delay, ensuring the fastest response speed under extreme fault conditions.

[0094] In some embodiments, the digital quantity detection unit 203 may include an analog-to-digital converter (ADC) and a digital quantity delay verification unit. The ADC performs analog-to-digital conversion on the analog voltage signal, outputting a digital sampling signal with a sampling rate, for example, greater than or equal to 1 Msps, to ensure that detailed current characteristics are captured. The digital quantity delay verification unit compares the sampled value of the digital sampling signal with a set voltage threshold. If the sampled value of the digital sampling signal is greater than the voltage threshold and remains so for a set delay time, it outputs a second detection result indicating an overcurrent fault. The delay time can be configured via software, for example, to 200 μs. This delay detection avoids misjudgments caused by normal switching transients and brief interference pulses.

[0095] The aforementioned analog-to-digital converter and digital delay verification unit can be implemented using an FPGA. Furthermore, a microsecond-level short-window moving average filter or finite impulse response filter can be applied to the sampled values ​​of the digital sampling signal output by the analog-to-digital converter in the FPGA to further suppress possible spike noise and improve the stability of the digital sampling signal.

[0096] In some embodiments, the above-mentioned logic judgment unit 204 can also be implemented using an FPGA, and can be integrated with the analog-to-digital converter and the digital delay verification unit in the same FPGA.

[0097] For ease of description, the current value corresponding to the voltage threshold is referred to as the second set value. In specific applications, the second set value can be set to a value that is relatively higher than the first set value. For example, 1.5-3.0 pu, or in a specific application, it can be set to 2.0 pu.

[0098] The backup protection module 20 in this embodiment of the invention employs a detection method combining analog signal detection and parallel digital signal delay verification. Only when both analog and digital signal detection confirm an overcurrent fault will the backup protection module determine that overcurrent protection needs to be triggered. Analog signal detection ensures rapid response under extreme fault conditions, while digital signal detection avoids misjudgments caused by normal switching transients and brief interference pulses, guaranteeing the accuracy of the judgment result. The backup protection module 20 combines the speed of analog circuits with the accuracy and flexibility of digital circuits, ensuring reliability while pursuing high speed.

[0099] It should be noted that the various modules / units described in the converter valve bridge arm overcurrent protection device of this invention embodiment can be software modules / units, hardware modules / units, or a combination of both. For example, for various devices or products applied to or integrated into a chip, all of its modules / units can be implemented using hardware methods such as circuits, or at least some modules / units can be implemented using software programs that run on a processor integrated within the chip, while the remaining (if any) modules / units can be implemented using hardware methods such as circuits; for various devices or products applied to or integrated into a chip module, all of its modules / units can be implemented using hardware methods such as circuits, and different modules / units can be located in the same component (e.g., chip, circuit module, etc.) or different components of the chip module, or at least some modules / units can be implemented using hardware methods such as circuits. The implementation is achieved through a software program that runs on the processor integrated within the chip module. The remaining modules / units (if any) can be implemented using hardware methods such as circuits. For various devices and products applied to or integrated into terminal equipment, each of their modules / units can be implemented using hardware methods such as circuits. Different modules / units can be located in the same component (e.g., chip, circuit module, etc.) or different components within the terminal equipment. Alternatively, at least some modules / units can be implemented through a software program that runs on the processor integrated within the terminal equipment, while the remaining modules / units (if any) can be implemented using hardware methods such as circuits.

[0100] The converter valve bridge arm overcurrent protection device provided in this embodiment of the invention can be applied to converter stations with various topologies to achieve fast and reliable overcurrent protection for the converter valves configured in the converter station.

[0101] For example, a standard bipolar converter station consists of two poles, namely the positive pole and the negative pole. Each pole is equipped with a redundant control system (including pole control and valve control). Each pole control system controls all valve control systems corresponding to its pole. Each pole consists of a 12-pulse valve group (two 6-pulse converter valves connected in series). Each 6-pulse converter valve is controlled by a separate valve control system, so a pole will have two identical valve control systems.

[0102] Accordingly, in the above application scenarios, the main protection module in this embodiment of the invention is set on each pole control system, and the backup protection module is set on each valve control system. The main protection module performs overcurrent detection on all converter valve bridge arms corresponding to its pole. When it determines that overcurrent protection needs to be triggered, it sends a protection action command to the backup protection modules on all corresponding valve control systems. The backup protection modules on each valve control system perform overcurrent detection on each converter valve bridge arm in the corresponding valve group. After determining that overcurrent protection needs to be triggered or receiving the protection action command sent by the main protection module, they control the converter valve in the corresponding valve group to enter the lockout state.

[0103] For example, a back-to-back converter station (without DC lines) used to connect two AC power grids with different frequencies or operating asynchronously is typically equipped with one (redundant) pole control system and two valve control systems (one for each valve group).

[0104] Accordingly, in the above application scenario, the main protection module in this embodiment of the invention is set on the polar control system, and a backup protection module is set on each of the two valve control systems. The main protection module performs overcurrent detection on all converter valve bridge arms. When it determines that overcurrent protection needs to be triggered, it sends a protection action command to the backup protection modules on the two valve control systems. The backup protection modules on each valve control system perform overcurrent detection on each converter valve bridge arm in the corresponding valve group. After determining that overcurrent protection needs to be triggered or receiving the protection action command sent by the main protection module, they control the converter valve in the corresponding valve group to enter the lockout state.

[0105] For example, for VSC-HVDC, based on MMC (Modular Multilevel Converter), there is usually one (redundant configuration) pole control system to realize unified control of the entire station. The valve control system (usually called valve base controller) is usually configured according to bridge arm, that is, one valve base controller is configured for each of the two bridge arms above and below each phase.

[0106] Accordingly, in the above application scenario, the main protection module in this embodiment of the invention is set on the polar control system, and a backup protection module is set on each valve base controller. The main protection module performs overcurrent detection on all converter valve bridge arms. When it determines that overcurrent protection needs to be triggered, it sends a protection action command to the backup protection modules on all valve base controllers. The backup protection modules on each valve base controller perform overcurrent detection on each corresponding converter valve bridge arm. After determining that overcurrent protection needs to be triggered or receiving the protection action command sent by the main protection module, they control the corresponding converter valve to enter the lockout state.

[0107] Accordingly, this embodiment of the invention also provides a converter system, which includes converter valves and a converter valve arm overcurrent protection device according to any of the above embodiments. This converter system can be used in HVDC or VSC-HVD systems. Depending on the type and configuration of the converter station, the number and installation position of the main protection module and backup protection modules in the converter valve arm overcurrent protection device need to be adaptively adjusted so that the main protection module performs overcurrent detection on all converter valve arms. When it determines that overcurrent protection needs to be triggered, it sends a protection action command to all backup protection modules. Each backup protection module can perform overcurrent detection on one or a group of converter valve arms. Overcurrent detection can be performed on all converter valve arms of the converter station through one or more backup protection modules. After determining that overcurrent protection needs to be triggered or receiving a protection action command from the main protection module, each backup protection module controls the corresponding converter valve to enter a locked state.

[0108] Accordingly, embodiments of the present invention also provide a method for overcurrent protection of a converter valve bridge arm, such as... Figure 4 The diagram shown is a flowchart of this method.

[0109] Reference Figure 4 A primary protection service 41 is set in the polar control layer, and a backup protection service 42 is set in the valve control layer.

[0110] In step 401, the main protection service 41 performs real-time overcurrent detection on the converter valve bridge arm.

[0111] In step 402, the backup protection service 42 performs real-time overcurrent detection on the converter valve bridge arm.

[0112] The main protection service 41 and the backup protection service 42 each independently perform overcurrent detection of the converter valve bridge arm according to different detection methods.

[0113] In step 403, the primary protection service 41 determines that overcurrent protection needs to be triggered and sends a protection action command to the backup protection service 42 via the fiber optic channel.

[0114] In step 404, after the backup protection service 42 determines that overcurrent protection needs to be triggered or receives a protection action command sent by the main protection service 41, it controls the corresponding converter valve to enter the lockout state.

[0115] It should be noted that in this embodiment of the invention, the main protection service and the backup protection service not only perform overcurrent detection of the converter valve bridge arm independently and in parallel, but also work together through signal interaction and adopt a cooperative control strategy with the main protection service taking priority. After receiving the protection action command sent by the main protection service 41, the backup protection service will execute the protection action and control the corresponding converter valve to enter the lockout state, regardless of the current detection result.

[0116] In some embodiments, to ensure the accuracy of the detection results, the main protection service 41 can employ a dual judgment and verification mechanism. For example, in a non-limiting embodiment, a detection method combining fixed-value judgment and short-time integral verification can be used. Specifically, the current signals of each bridge arm can be acquired in real time to obtain instantaneous sampled values. If the instantaneous sampled value of any bridge arm is greater than a first set value, the current signal of that bridge arm is integrated within a certain time window to obtain an integral value. If the integral value is greater than an integral threshold dynamically determined based on the instantaneous sampled values, it is determined that overcurrent protection needs to be triggered, and a protection action command is sent to the backup protection service 42.

[0117] In some embodiments, to ensure the accuracy of the detection results, the backup protection service 42 can also employ a dual judgment and verification mechanism. For example, in a non-limiting embodiment, a detection method that performs analog quantity detection and digital quantity detection in parallel is used. Specifically, the analog voltage signal based on the current of each bridge arm is acquired in real time; simultaneously, the analog voltage signal is subjected to analog quantity detection and digital quantity detection to obtain a first detection result corresponding to the analog quantity detection and a second detection result corresponding to the digital quantity detection. If both the first detection result and the second detection result indicate an overcurrent fault, it is determined that overcurrent protection needs to be triggered.

[0118] Among them, the analog quantity detection can directly compare the analog voltage signal with the preset reference voltage. If the analog voltage signal is greater than the reference voltage, the first detection result indicating an overcurrent fault will be output.

[0119] Among them, the digital quantity detection can perform analog-to-digital conversion on the analog voltage signal and output a digital sampling signal; when the sampled value of the digital sampling signal is greater than the set voltage threshold and continues for a set delay time, a second detection result indicating an overcurrent fault is output.

[0120] All of the above parameters, such as time parameters (e.g., time window, delay time) and threshold parameters (first set value, voltage threshold), can be set by software. Moreover, appropriate parameters can be selected according to different application scenarios. For details, please refer to the description in the corresponding embodiment of the converter valve bridge arm overcurrent protection device of the present invention, which will not be repeated here.

[0121] The converter valve bridge arm overcurrent protection device and method provided in this invention adopts a two-level protection configuration of polarization layer main protection and valve control layer backup protection, which greatly simplifies the redundancy of the configuration levels and can provide better protection services for converter stations. This is mainly reflected in the following aspects:

[0122] (1) Reliability assurance: The dual detection mechanism reduces the probability of protection failure and false tripping rate, and the short-time integral algorithm has better noise resistance. The main protection adopts a dynamic integral criterion based on the fault energy model, which realizes the matching between the protection setting and the physical damage model of the device. This is an essential innovation that is different from the traditional fixed integral / time limit protection. At the same time, it has excellent noise resistance in terms of mechanism.

[0123] (2) Improved speed: The main protection directly sends the valve-controlled interlocking trigger pulse from the polarity control layer, reliably interlocking the converter valve, which can effectively reduce the transmission link delay and ensure that common faults are cleared within 100μs; the backup protection avoids delays under extreme operating conditions.

[0124] (3) Cost optimization: Valve control hardware resources can be reused, saving hardware resources and costs.

[0125] In this invention, unless otherwise explicitly specified and limited, ordinal numbers, such as "first," "second," etc., are used only to distinguish and describe related objects, and should not be construed as indicating or implying the relative importance or order between related objects. Furthermore, ordinal numbers do not represent the quantity of related objects.

[0126] In the several embodiments provided by this invention, it should be understood that the division and structure of the modules and units in the disclosed converter valve bridge arm overcurrent protection device are merely illustrative and can be implemented through other modified structures. This invention is not limited thereto.

[0127] In addition, the functional modules in the various embodiments of the present invention can be integrated into one processing unit, or they can be separate physical units, or two or more units can be integrated into one unit.

[0128] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A current limiting device for a bridge arm of a converter valve, characterized in that The application relates to a protection system for a high-voltage direct-current converter, comprising: a main protection module and a backup protection module, the main protection module is arranged at an extreme control layer, and the backup protection module is arranged at a valve control layer; the main protection module and the backup protection module communicate through optical fibers; the main protection module and the backup protection module each perform real-time overcurrent detection of a bridge arm of a converter valve according to different detection modes; when the main protection module determines that overcurrent protection needs to be triggered, the main protection module sends a protection action instruction to the backup protection module; when the backup protection module determines that overcurrent protection needs to be triggered or receives the protection action instruction sent by the main protection module, the backup protection module controls the corresponding converter valve to enter a locking state; the backup protection module comprises an analog signal acquisition unit, an analog quantity detection unit, a digital quantity detection unit, a logic judgment unit and a control unit; the analog signal acquisition unit is used for acquiring real-time analog voltage signals based on currents of each bridge arm; the analog quantity detection unit is used for performing bridge arm overcurrent detection based on the analog voltage signals and outputs a first detection result; the digital quantity detection unit is used for performing bridge arm overcurrent detection based on digital sampling signals obtained by analog-digital conversion of the analog voltage signals and outputs a second detection result; the logic judgment unit is used for determining that overcurrent protection needs to be triggered when the first detection result and the second detection result both indicate overcurrent faults; and the control unit is used for controlling the corresponding converter valve to enter a locking state when the logic judgment unit determines that overcurrent protection needs to be triggered or receives the protection action instruction sent by the main protection module.

2. The converter valve bridge arm overcurrent protection device according to claim 1, characterized in that, the main protection module comprises a current acquisition unit, an instantaneous value detection unit, an integral detection unit and a communication unit; the current acquisition unit is used for acquiring real-time current signals of each bridge arm and obtaining instantaneous sampling values; the instantaneous value detection unit is used for sending a trigger signal to the integral detection unit when the instantaneous sampling values are greater than a first set value; the integral detection unit is used for performing integral calculation on the current signals of the bridge arm within a certain time window to obtain an integral value when the trigger signal is received; and the integral detection unit determines that overcurrent protection needs to be triggered when the integral value is greater than an integral threshold value dynamically determined based on the instantaneous sampling values; the communication unit is used for sending the protection action instruction to the backup protection module when the integral detection unit determines that overcurrent protection needs to be triggered.

3. The converter valve bridge arm overcurrent protection device according to claim 2, characterized in that, The current acquisition unit comprises a current sensor.

4. The converter valve bridge arm overcurrent protection device of claim 1, wherein, The analog quantity detection unit comprises: a comparator, one input end of the comparator inputs the analog voltage signal, the other input end inputs a reference voltage, and the comparator outputs a first detection result indicating an overcurrent fault when the analog voltage signal is greater than the reference voltage.

5. The converter valve bridge arm overcurrent protection device according to claim 2, characterized in that, The digital quantity detection unit comprises: an analog-digital converter, which is used for performing analog-digital conversion on the analog voltage signal and outputs a digital sampling signal; a digital quantity delay verification unit, which is used for comparing a sampling value of the digital sampling signal with a set voltage threshold value, and outputs a second detection result indicating an overcurrent fault when the sampling value of the digital sampling signal is greater than the voltage threshold value and lasts for a set delay time.

6. The converter valve bridge arm overcurrent protection device according to claim 5, characterized in that, The analog-digital converter, the digital quantity delay verification unit and the logic judgment unit are integrated in the same FPGA.

7. The converter valve bridge arm overcurrent protection device according to claim 4, characterized in that, The device further comprises: a voltage source for providing the reference voltage.

8. The converter valve bridge arm overcurrent protection device according to claim 7, characterized in that, The reference voltage output by the voltage source is an adjustable voltage.

9. The converter valve bridge arm overcurrent protection device according to claim 5, characterized in that, The first set value ranges from 1.0 to 2.0 p.u., and the current value corresponding to the voltage threshold ranges from 1.5 to 3.0 p.u.

10. The converter valve bridge arm overcurrent protection device of claim 5, wherein, The delay time is configured by software.

11. A method of overcurrent protection of a bridge arm of a converter valve, characterized in that The method comprises: setting a main protection service at the pole control layer and a backup protection service at the valve control layer; The main protection service and the backup protection service each perform real-time overcurrent detection of the bridge arm of the converter valve in different detection modes; the backup protection service performing overcurrent detection of the bridge arm of the converter valve comprises: acquiring analog voltage signals based on the current of each bridge arm in real time; simultaneously performing analog quantity detection and digital quantity detection on the analog voltage signals to obtain a first detection result corresponding to the analog quantity detection and a second detection result corresponding to the digital quantity detection; in the case where the first detection result and the second detection result both indicate an overcurrent fault, it is determined that overcurrent protection needs to be triggered; when the main protection service determines that overcurrent protection needs to be triggered, sending a protection action instruction to the backup protection service through a fiber channel; after the backup protection service determines that overcurrent protection needs to be triggered or receives the protection action instruction sent by the main protection service, controlling the corresponding converter valve to enter a blocking state.

12. The method of claim 11, wherein, The main protection service performing overcurrent detection of the bridge arm of the converter valve comprises: acquiring the current signal of each bridge arm in real time to obtain an instantaneous sampling value; in the case where the instantaneous sampling value of any bridge arm is greater than a first set value, integrating the current signal of the bridge arm within a certain time window to obtain an integral value; if the integral value is greater than an integral threshold dynamically determined based on the current signal, it is determined that overcurrent protection needs to be triggered, and the protection action instruction is sent to the backup protection service.

13. The method of claim 12, wherein, The method further comprises: determining the integral threshold based on the instantaneous sampling value through table lookup and / or function calculation.

14. The method of claim 11, wherein, The analog quantity detection on the analog voltage signal comprises: comparing the analog voltage signal with a preset reference voltage; if the analog voltage signal is greater than the reference voltage, outputting a first detection result indicating an overcurrent fault.

15. The method of claim 14, wherein, The digital quantity detection on the analog voltage signal comprises: analog-digital conversion on the analog voltage signal to output a digital sampling signal; in the case where the sampling value of the digital sampling signal is greater than a set voltage threshold and lasts for a set delay time, outputting a second detection result indicating an overcurrent fault.

16. A commutation system characterized by, The system comprises a converter valve and a converter valve bridge arm overcurrent protection device as claimed in any one of claims 1 to 10.

Images