Method and device for judging state of high-voltage direct-current power transmission system and medium

Abstract

The invention discloses a method and device for judging the state of a high-voltage direct-current power transmission system and a medium, and the method and device have the following beneficial effects: in the process of judging the operation state of alternating-current field equipment in the step S1, the circuit quantity of a line is compared with a preset current threshold value; the operation state of the line is further judged according to the comparison result, and whether the line forms an actual energy circulation loop or not is monitored, namely, whether the line forms the actual energy circulation loop or not can be judged by adding the auxiliary judgment condition that whether the line is in the operation state or not; therefore, misjudgment of the last circuit breaker and the last circuit by the control system in the empty charging state is well avoided.

Description

Technical Field

[0001] This invention relates to the field of high voltage direct current (HVDC) transmission technology, specifically to a method, device, and medium for determining the state of a HVDC transmission system. Background Technology

[0002] The last circuit breaker and the last line are important control functions of the high voltage direct current transmission system. After the last AC circuit breaker or the last AC line connecting the converter to the AC system trips, the converter is shut down urgently. The judgment logic of the last circuit breaker and the last line uses the opening and closing signals of the AC circuit breaker at this site and the disconnect switches on both sides as the criteria for whether the AC and DC systems are connected.

[0003] However, in actual operation, it was found that if the station performs no-load charging on a certain AC line through an AC circuit breaker (i.e., no actual energy flow loop is formed at the station on the other side of the line), the final circuit breaker or the final line function is prone to misjudgment. Specifically, for example... Figure 1-2 As shown, the converter station is connected to AC station A via AC line A and to AC station B via AC line B. In the AC field of the converter station, only one AC line, A, is in operation, while another AC line, B, is being charged without power from the converter station side. Since the feeder circuit breakers of both lines are in the connected state, and the number of operating lines is only counted based on the connection status of the circuit breaker bay equipment, the converter control system (CCP) will determine that two AC lines are connected to the AC field. However, the AC line B, being in the uncharged state, does not form a closed loop and cannot transmit energy. In reality, the operating AC line A has become the "last line." Because the AC station control system (ACC) and the converter control system (CCP) cannot obtain the position status signal of the feeder circuit breaker of AC station B, they cannot correctly determine the line's status. Therefore, when the converter station charges the lines (e.g., ...), ... Figure 1 Or the feeder circuit breaker on the opposite side of the line trips (e.g.) Figure 2 When the status information of the circuit breaker bay equipment at the converter station cannot be obtained, the AC station control system (ACC) and the converter control system (CCP) of the converter station cannot correctly identify the last circuit breaker and the last line, resulting in failure to operate.

[0004] In summary, existing technologies do not assess the operating status of the circuit breaker and the last line in determining their status, which can easily lead to misjudgment of the last circuit breaker and the last line when they are in an unloaded charging state. Summary of the Invention

[0006] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a method, device, and medium for determining the state of a high-voltage direct current transmission system, which can solve the aforementioned technical problems.

[0007] (II) Technical Solution To solve the above-mentioned technical problems, the present invention provides the following first aspect of the technical solution: a method for determining the state of a high-voltage direct current transmission system, comprising the following steps: S1. Determine the operating status of AC field equipment: This includes comparing the circuit quantity with a preset current threshold, and further determining the operating status of the circuit based on the comparison result. S2. Determine the interconnection status of the busbars; S3. Using the judgment results of step S1 and step S2, determine whether a certain circuit breaker is the last circuit breaker or the circuit breaker connecting the last line.

[0008] Preferably, the circuit quantity of the line includes the load current value and the current change value of the line; the current threshold includes three thresholds: X, Y, and Z, where X is the load current threshold when the line is operating normally; Y is the current change rate threshold when the line changes from a stopped state to an operating state, and Y is greater than 0; Z is the current change rate threshold when the line changes from an operating state to a stopped state, and Z is less than 0.

[0009] Preferably, in step S1, when the load current value of the line is greater than X, it is determined that the line is in normal operating condition.

[0010] Preferably, step S1 further includes determining the operating status of the line based on the input and / or output values ​​of the SR trigger corresponding to the line.

[0011] Preferably, in step S1, when the load current value of the line is less than X, and the current mutation value is less than or equal to Y or greater than or equal to Z, and the output value Q of the SR trigger is 0, it is determined that the line is in an unloaded charging state.

[0012] Preferably, in step S1, when the load current value of the line is greater than X or the current mutation value is greater than Y, and the input value S of the SR trigger is 1, R is 0, and the output value Q is 1, it is determined that the line has changed from the no-charge state to the running state.

[0013] Preferably, in step S1, when the load current value of the line is less than X and the current mutation value is less than Z, and the input value S of the SR trigger is 0, R is 1, and the output value Q is 0, it is determined that the line has switched from the running state to the no-charge state.

[0014] Preferably, step S1 further includes determining the operating status of the circuit breaker.

[0015] To solve the above-mentioned technical problems, the present invention provides the following second aspect of the technical solution: a device, which is an electronic device, includes a memory and a processor coupled to each other, the processor being used to execute program instructions stored in the memory to implement the above-mentioned method for determining the state of the high voltage direct current transmission system.

[0016] To solve the above-mentioned technical problems, the present invention provides the following third aspect of the technical solution: a medium, which is a computer-readable storage medium, on which program instructions are stored, and when the program instructions are executed by a processor, the method for determining the state of the high-voltage direct current transmission system of the first aspect is implemented.

[0017] (III) Beneficial Effects Compared with the prior art, the present invention provides a method, device and medium for judging the state of a high voltage direct current transmission system, which has the following beneficial effects: In the process of judging the operating state of AC field equipment in step S1, the present invention compares the circuit quantity of the line with a preset current threshold, and further judges the operating state of the line based on the comparison result, thereby realizing the monitoring of whether the line forms an actual energy flow loop. That is, the present invention can judge whether the line forms an actual energy flow loop by adding the auxiliary judgment condition of whether the line is in the operating state, thereby better avoiding the misjudgment of the final circuit breaker and the final line by the control system under the no-charge state. Attached Figure Description

[0018] Figure 1 A schematic diagram illustrating the charging process for the lines at the converter station; Figure 2 This is a schematic diagram showing the tripping of the feeder circuit breaker on the opposite side of the line. Figure 3 Logic diagram for determining the operating status of AC circuit breakers; Figure 4 Logic diagram for determining the operating status of each feeder string; Figure 5 A statistical chart showing the number of operating statuses of each feeder string; Figure 6 Logic diagram for determining busbar disconnection; Figure 7 Logic diagram for protecting the circuit breaker from starting; Figure 8 Logic diagram for protecting and stopping the converter; Figure 9 This is the logic diagram for judging the last circuit breaker and the last line in this invention (taking the logic for judging the operating status of the AC line on the I bus side as an example). Figure 10 This is a schematic diagram of the electronic device of the present invention; Figure 11 This is a schematic diagram of the framework of the computer-readable storage medium of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides a method for determining the state of a high-voltage direct current transmission system, comprising the following steps: S1. Determine the operating status of AC field equipment: This includes comparing the circuit quantity with a preset current threshold, and further determining the operating status of the circuit based on the comparison result.

[0021] High-voltage direct current (HVDC) transmission systems are power engineering systems that use direct current (DC) for high-power, long-distance power transmission. They are primarily used for submarine cable transmission, asynchronous grid interconnection, and clean energy grid connection. This system rectifies alternating current (AC) into direct current (DC) for transmission through converter stations. A HVDC system includes converters, circuit breakers, AC lines, and busbars. The final circuit breaker and the final line are crucial control functions of a HVDC system. After the last AC circuit breaker or the last AC line connecting the converter to the AC system trips, an emergency shutdown of the converter is performed. This invention can be applied to determining the status of the final circuit breaker and / or the final line when the AC line is in an unloaded / charged state.

[0022] In addition, specifically, step S1 above also includes judging the operating status of the circuit breaker.

[0023] S2. Determine the interconnection status of the busbars.

[0024] S3. Using the judgment results of step S1 and step S2, determine whether a certain circuit breaker is the last circuit breaker or the circuit breaker connecting the last line.

[0025] The steps described above in this invention will now be described in detail.

[0026] In high-voltage direct current (HVDC) transmission systems, the AC field typically employs a 3 / 2, double-bus connection, where the double buses consist of Bus I and Bus II. The final circuit breaker and final line protection functions are implemented collaboratively by the AC station control system (ACC) and the converter control system (CCP). The ACC is responsible for collecting the position signals of the AC circuit breakers and their respective disconnectors (i.e., isolating switches), determining whether the AC circuit breaker bay is in operation, and sending this information to the CCP. The CCP, on the other hand, performs logical checks on the final circuit breaker and final line (e.g., whether the converter or line is connected to Bus I or Bus II, whether the two buses are interconnected, the number of AC lines connected to the converter, etc.), and sends the results to the ACC. Simultaneously, the ACC prohibits manual disconnection of the final circuit breaker and the corresponding AC circuit breaker for the final line. After the final circuit breaker or final line logic operation, the CCP's output lockout of the converter is activated.

[0027] For 3 / 2 double busbar connection, it is generally specified that the A circuit breaker bay is closer to the I busbar, the B tie circuit breaker bay is in the middle, and the C circuit breaker bay is closer to the II busbar.

[0028] Specifically, the above step S1 uses the following method to determine the operating status of the circuit breaker: (1) When all three phases of the circuit breaker A on the I bus side and its two sides disconnectors are in the closed position, the AC circuit breaker is in the operating state, and the A circuit breaker bay connection signal A_CB_CONNECTED is 1, that is, when A_CB_CONNECTED is 1, it is determined that the circuit breaker is in the operating state; when any phase of the circuit breaker and its two sides disconnectors is in the open position, the A circuit breaker bay disconnection signal A_CB_DISCONNECTED is 1, such as Figure 3 As shown. The same applies to the tie circuit breaker (B_CB_CONNECTED) and the II bus side circuit breaker (C_CB_CONNECTED). (2) If the line or converter is located on the I bus side feeder, when A_CB_CONNECTED is 1, it is determined that the line or converter is connected to the I bus. When both B_CB_CONNECTED and C_CB_CONNECTED are 1, it is determined that the line or converter is connected to the II bus. The same applies to the II bus side feeder. Figure 4 As shown. (3) By judging the operating status of the circuit breaker bay equipment, identify whether the line or converter is connected to bus I or bus II, and perform quantity statistics, such as Figure 5 As shown.

[0029] like Figure 9As shown, in step S1 of the present invention, when determining the operating state of the AC field device, that is, in the last circuit breaker and the last line judgment logic, a judgment on the operating state of the line is newly added, that is, an auxiliary discrimination condition of whether the line is in the operating state is newly added. The line operating state logic is realized by judging the line current quantity. Specifically, the line current quantity includes the load current value and the current mutation value (i.e., the load current mutation) of the line; the above current thresholds include three thresholds X, Y, and Z. Among them, X is the load current threshold when the AC line (referred to as the line for short) is operating normally; Y is the current change rate threshold when the line changes from a stopped state to an operating state, Y is the current rising rate, and Y>0; Z is the current change rate threshold when the line changes from an operating state to a stopped state, Z is the current falling rate, and Z<0. Specifically, in the above step S1, the line current quantity is compared with the preset current threshold, and the operating state of the line is judged according to the input value and / or output value of the SR flip-flop corresponding to the line; the judgment of the operating state of the line is specifically as follows (1)-(4).

[0030] (1) In the above step S1, when the load current value of the line is greater than X, and the input values of the SR flip-flop are S = 0, R = 0, and the output value Q = 1, it is judged that the line is in the normal operating state; at this time, the judgment logic of the last circuit breaker and the last line is the same as the original working principle. By judging the operating state of the AC circuit breaker, it is identified that the line or the converter is connected to bus I or bus II. Specifically, see the judgment of the operating state of the circuit breaker in step S1 above. That is to say, when the line is operating with load normally (current>X), at this time, according to the original logic, the line / converter connected to bus I or bus II is identified through the AC circuit breaker state, and the auxiliary criterion of the line operating state does not interfere with the core judgment of the last circuit breaker and the last line.

[0031] (2) In the above step S1, when the load current value of the line is less than X, and the current mutation value is less than or equal to Y or the current mutation value is greater than or equal to Z, and the output value Q of the SR flip-flop is 0, it is judged that the line is in the no-load charging state; that is, when the following three conditions are met at the same time, it is judged that the line is in the no-load charging state: First, the load current value <X; Second, the current mutation value ≤Y or the current mutation value ≥Z; Third, the output value Q of the SR flip-flop = 0. That is to say, when the converter station charges the line and the line is in the no-load charging state, that is, the load current value of the line is less than X and the current mutation value is not greater than Y or not less than Z, at this time, the output of the SR flip-flop is the original value 0, and the logic judges that the line is not connected to bus I and bus II, avoiding misjudging "connected to the bus" during no-load charging.

[0032] (3) In the above step S1, when the load current value of the line is greater than X, or the current mutation value is greater than Y, and the input value S of the SR flip-flop is 1, R is 0, and the output value Q is 1, it is determined that the line changes from the no-load charging state to the operating state; that is, when the following two conditions are met simultaneously, it is determined that the line changes from the no-load charging state to the operating state: First, the load current value > X or the current mutation value > Y; Second, S = 1, R = 0, and Q = 1. That is to say, when the feeder circuit breaker of the opposite station line is closed and the line changes from the no-load charging state to the operating state, the load current value of the line will be greater than X or the current mutation value will be greater than Y, the input value S of the SR flip-flop is 1, R is 0, and the output value Q is 1. The judgment logic judges the bus connection mode on the premise that the line is actually in the operating state, that is, by judging the operating state of the AC circuit breaker, it is identified that the line or the converter is connected to Bus I or Bus II. See the above step S1 for the judgment of the operating state of the circuit breaker for details.

[0033] (4) In the above step S1, when the load current value of the line is less than X and the current mutation value is less than Z, and the input value S of the SR flip-flop is 0, R is 1, and the output value Q is 0, it is determined that the line changes from the operating state to the no-load charging state; that is, when the following three conditions are met simultaneously, it is determined that the line changes from the operating state to the no-load charging state: First, the load current value < X; Second, the current mutation value < Z; Third, S = 0, R = 1, and Q = 0. That is to say, when the line is in the operating state (both circuit breakers on both sides are in operation and in the normal energy transmission state), the circuit breaker of the opposite station trips, and the line is in the no-load charging state. The load current value of the line is less than X and the current mutation value is less than Z. At this time, the input value S of the SR flip-flop is 0, R is 1, and the output value Q is 0. The logic judges that the line is not connected to Bus I or Bus II, that is, it is determined that the line is disconnected from the bus to avoid misjudging "still judged as connected without energy flow".

[0034] It can be understood that the above X is the core boundary for dividing "operating with load" and "no-load charging / stopped operation". Only when the current exceeds X, it is defaulted that there is actual energy flow in the line; and the above Y is used to capture the mutation process of "no-load charging → operating". Even if the current does not exceed X, as long as the rising rate is fast enough (exceeds Y), it is also determined as actual operation; in addition, the above Z is used to capture the mutation process of "operating → no-load charging". When the current decline rate meets the standard (less than Z), it is determined that the energy flow is lost. Through the above newly added auxiliary criterion for the line, the present invention can judge whether the line forms an actual energy flow loop, and avoid misjudging the last circuit breaker and the last line by the control system under the no-load charging state.

[0035] The load current value of the above-mentioned line can be obtained by using equipment such as current transformers; while the current mutation value can be obtained by collecting the instantaneous or effective value of the line current at a fixed sampling frequency to obtain continuous current time series data. The current mutation value can then be obtained by dividing the current difference between two adjacent sampling periods by the sampling time interval. In addition, the aforementioned SR flip-flop, also called an SR latch, is a basic unit for constructing complex sequential circuits. Its core function is to store 1 bit of binary information. It is generally composed of two NOR gates or NAND gates cross-coupled, with two input terminals (S terminal for set, R terminal for reset) and two complementary output terminals (Q and Q-not). Its working logic is clear: when S is a valid signal, the output terminal Q is set to 1; when R is a valid signal, Q is set to 0; when both S and R are invalid signals, the original output state is maintained. In power-related scenarios, SR flip-flops are often used to implement functions such as signal latching and state maintenance. For example, they can lock the detection signal of current surge to prevent signal fluctuations from causing false triggering of protection actions. When the line current meets the set conditions, such as the load current value exceeding the threshold X, or the current surge value exceeding the threshold Y (such as the current surge scenario of no-load charging to operation), a signal is input to the set terminal (S terminal) of the SR flip-flop, and the output terminal (Q) of the SR flip-flop... The reset terminal (R terminal) of the SR trigger will change to 1, locking the line in an effective operating state, thus confirming that the line has formed an actual energy flow loop. If the load current value of the line is continuously lower than the threshold X, and there is no current surge that meets the requirements, or if the line is faulty, the circuit breaker trips, or other situations cause current interruption, the reset terminal (R terminal) of the SR trigger will receive a signal, and the output terminal (Q terminal) of the SR trigger will become 0, releasing the line from the effective operating state. The SR trigger can be set in the converter control system (CCP) as a logic function module, specifically integrated into the programmable logic controller (PLC) of the CCP or the program of a dedicated control chip. The current transformer mentioned above can specifically use models such as LZZBJ9 available on the market. The acquisition of the load current value, current surge value, and other data, as well as the SR trigger, are all existing technologies and will not be elaborated on here. Preferably, the values ​​of X, Y, and Z can be referred to Table 1 below. In addition, other values ​​can be set according to requirements, without too many restrictions.

[0036] Table 1. Suggested Values ​​for X, Y, and Z

[0037] Specifically, step S2 above determines the interconnection status of the busbars using the following method: When all circuit breaker bays in the first string of the AC field 3 / 2 connection are in operation, the first string connection (CONN_NUM_ACC1) is 1; if CONN_NUM_ACC1~8 are all 0, meaning each string is not interconnected, the quantity statistics value CONN_NUM_ALL is 0, at this time it is determined that the AC busbars are operating in a split manner, and the TWO_BUS_DISCON signal is 1. Figure 6 As shown. It can be understood that the parameters CONN_NUM_ACC1~8 correspond to the interconnection status flags of the eight complete strings in a 3 / 2 wiring configuration. In a 3 / 2 wiring configuration, each string uses three circuit breakers to connect two busbars. The circuit breaker in the middle of the string is the interconnection circuit breaker, which enables power exchange and loop power supply between the two busbars. When all circuit breaker intervals in a string (such as the first string) are running, it means that the busbar circuit breakers and interconnection circuit breakers in the string are all normally closed, and the two busbars form a valid connection through this string, so the corresponding CONN_NUM_ACC is 1. Conversely, when CONN_NUM_ACC of a string is 0, it indicates that the interconnection function of that string has failed, possibly due to the tripping of a key circuit breaker or the opening of a disconnecting switch, causing the string to be unable to achieve interconnection between the two busbars. CONN_NUM_ALL is a summary statistical parameter of the connection status of 8 strings. CONN_NUM_ACC1~8 are all 0 only when all strings are disconnected (CONN_NUM_ACC1~8 are all 0). This is the core prerequisite for bus splitting, indicating that there are no strings connecting the two buses. The TWO_BUS_DISCON signal is the status feedback signal for AC bus splitting operation. When the condition that all strings are disconnected is met, the signal is set to 1 to inform the control system that the bus is in a splitting state, so as to trigger subsequent protection or control strategies. In normal operation of the 3 / 2 wiring, the circuit breakers of all strings are usually in operation. The two sets of buses form a multi-ring power supply structure through multiple strings. This structure can ensure power supply reliability. For example, when a single string fails, the other strings can continue to maintain the connection between the two buses. When CONN_NUM_ACC1~8 are all 0, it is equivalent to the connection path of all strings being cut off. The originally connected I and II buses are divided into two independent power supply units, that is, bus splitting operation.

[0038] Specifically, step S3 uses the judgment results of step S1 and step S2 to determine whether a circuit breaker has become the last circuit breaker or the circuit breaker connected to the last line. This step S3 corresponds to the last circuit breaker and last line protection logic: when the AC station control system ACC determines that a certain circuit breaker bay has become the last circuit breaker or the circuit breaker connected to the last line, manual disconnection of that circuit breaker is prohibited. Figure 7As shown, the specific judgment method of step S3 and the corresponding final circuit breaker or final line protection logic judgment criteria are as follows: (1) When the two buses are not interconnected, that is, when TWO_BUS_DISCON is 1: if it is judged that the number of converters connected to bus I is greater than 0 and the number of AC lines connected to bus I is equal to 1, or if it is judged that the number of converters connected to bus II is greater than 0 and the number of AC lines connected to bus II is equal to 1, then the AC line connected to bus I or bus II is the final line, and the final line protection prohibits the circuit breaker connected to the final line from being manually tripped. (2) When the two buses are interconnected, that is, when TWO_BUS_DISCON is 0: if it is judged that the number of converters connected to the two buses is greater than 0 and the number of AC lines connected to the two buses is equal to 1, then the AC line connected to the two buses is the final line, and the final line protection prohibits the circuit breaker connected to the final line from being manually tripped. (3) When the two busbars are not interconnected, i.e., TWO_BUS_DISCON is 1, and a certain operating converter is located on the feeder of bus I: if it is determined that the circuit breaker on bus I is not in operation, then the tie circuit breaker or the circuit breaker on bus II is the last circuit breaker. Therefore, the protection of the last circuit breaker prohibits the tie circuit breaker or the circuit breaker on bus II from being manually opened; or if it is determined that the tie circuit breaker or the circuit breaker on bus II is not in operation, then the circuit breaker on bus I is the last circuit breaker. Therefore, the protection of the last circuit breaker prohibits the circuit breaker on bus I from being manually opened. (4) When the two busbars are not interconnected (TWO_BUS_DISCON is 1) and a certain operating converter is located on the feeder of the II busbar: if it is determined that the II busbar circuit breaker is not in operation, then the tie circuit breaker or the I busbar circuit breaker is the last circuit breaker. Therefore, the last circuit breaker protection prohibits the tie circuit breaker or the I busbar circuit breaker from being manually opened; or if it is determined that the tie circuit breaker or the I busbar circuit breaker is not in operation, then the II busbar circuit breaker is the last circuit breaker. Therefore, the last circuit breaker protection prohibits the II busbar circuit breaker from being manually opened. (5) When the two busbars are interconnected (TWO_BUS_DISCON is 0) and a certain operating converter is located on the feeder of the I busbar: if it is determined that the tie circuit breaker or the II busbar circuit breaker is not in operation, then the I busbar circuit breaker is the last circuit breaker. Therefore, the last circuit breaker protection prohibits the I busbar circuit breaker from being manually opened. (6) When the double bus interconnection is TWO_BUS_DISCON is 0 and a certain operating converter is located on the II bus side feeder: if it is determined that the tie circuit breaker or the I bus side circuit breaker is not in operation, the II bus side circuit breaker is the last circuit breaker. Therefore, the last circuit breaker protection prohibits the II bus side circuit breaker from being manually tripped.

[0039] Preferably, the present invention further includes controlling the output actions of the final circuit breaker and the final line protection using the judgment results of step S1 and step S2: the final circuit breaker and final line protection functions in the converter control system CCP are configured for a single converter. If it is determined that a certain operating converter is not connected to any line through the busbar, then the converter performs an emergency shutdown, such as... Figure 8 As shown, the specific method for determining whether a certain operating converter is not connected to any line via a bus is as follows: (1) When the two buses are not interconnected, that is, when TWO_BUS_DISCON is 1: the operating converter is connected to bus I and the number of AC lines connected to bus I is 0, or the operating converter is connected to bus II and the number of AC lines connected to bus II is 0. (2) When the two buses are interconnected, that is, when TWO_BUS_DISCON is 0: the operating converter is connected to bus I or bus II and the number of AC lines connected to bus I or bus II is 0.

[0040] like Figure 10 As shown, the present invention also provides an electronic device 1, which includes a memory 11 and a processor 12 coupled to each other. The processor 12 is used to execute program instructions stored in the memory 11 to implement the above-described method for determining the state of any of the high-voltage direct current transmission systems. In a specific implementation scenario, the electronic device 1 may include, but is not limited to, a microcomputer or a server. In addition, the electronic device 1 may also include mobile devices such as laptops and tablets, which are not limited here.

[0041] Specifically, the processor 12 is used to control itself and the memory 11 to implement the method for determining the state of any of the aforementioned high-voltage direct current transmission systems. The processor 12 can also be called a CPU (Central Processing Unit). The processor 12 may be an integrated circuit chip with signal processing capabilities. The processor 12 can also be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. The general-purpose processor can be a microprocessor or any conventional processor. Furthermore, the processor 12 can be implemented using integrated circuit chips.

[0042] In addition, such as Figure 11As shown, the present invention also provides a medium, which is a computer-readable storage medium 2, on which program instructions 21 are stored. When the program instructions 21 are executed by a processor, they implement the method for determining the state of any of the above-mentioned high-voltage direct current transmission systems. The storage medium 2 may include various media capable of storing program instructions, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0043] Compared with the prior art, the present invention provides a method, device and medium for judging the status of a high-voltage direct current transmission system, which has the following beneficial effects: In the process of judging the operating status of AC field equipment in step S1, the present invention compares the circuit quantity of the line with a preset current threshold, and further judges the operating status of the line based on the comparison result. That is, in the logic of the converter control system for judging the number of AC lines connected to the bus, an auxiliary judgment condition for judging the operating status of the line is added, so as to monitor whether the line forms an actual energy flow loop. The line operating status logic is realized by judging the line current quantity, including the load current value and the load current change, which can avoid misjudging the operating status of AC lines when the load is low. Moreover, the above-mentioned auxiliary judgment condition is complementary to the original judgment logic of the last circuit breaker and the last line: it does not change the judgment rules when operating under normal load, but intervenes to correct during the switch between no-load / operation status, and has strong compatibility. This invention adds auxiliary criteria for line parameters. When the last line appears in the AC field of the converter station, closing the circuit breaker of another line to charge the line allows the control system to correctly identify that the uncharged line has not formed an actual energy loop, maintaining the original last line judgment result. When only two lines remain in the AC field of the converter station, if the circuit breaker of the site opposite one of the lines trips, the control system can correctly identify that the AC line is in an uncharged state and the other line has become the last line, activating the last line and last circuit breaker protection functions. This improves the correctness of the last line and last circuit breaker judgment logic, thus better realizing the last line and last circuit breaker protection functions.

[0044] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method of judging a state of a high voltage direct current power transmission system, characterized by, Includes the following steps: S1. Determine the operating status of AC field equipment: This includes comparing the circuit quantity with a preset current threshold, and further determining the operating status of the circuit based on the comparison result. S2. Determine the interconnection status of the busbars; S3. Using the judgment results of step S1 and step S2, determine whether a certain circuit breaker is the last circuit breaker or the circuit breaker connecting the last line.

2. The method of judging the state of a high-voltage direct-current power transmission system according to claim 1, characterized by: The circuit quantities of the line include the load current value and the current change value of the line; the current thresholds include three thresholds: X, Y, and Z, where X is the load current threshold when the line is operating normally; Y is the current change rate threshold when the line changes from a stopped state to an operating state, and Y is greater than 0; Z is the current change rate threshold when the line changes from an operating state to a stopped state, and Z is less than 0.

3. The method of judging the state of a high-voltage direct-current power transmission system according to claim 2, characterized by: In step S1, when the load current value of the line is greater than X, it is determined that the line is in normal operating condition.

4. The method for determining the state of a high-voltage direct current transmission system according to claim 2, characterized in that: In step S1, the operating status of the line is determined based on the input and / or output values ​​of the SR trigger corresponding to the line.

5. The method for determining the state of a high-voltage direct current transmission system according to claim 4, characterized in that: In step S1, when the load current value of the line is less than X, and the current surge value is less than or equal to Y or greater than or equal to Z, and the output value Q of the SR trigger is 0, it is determined that the line is in an unloaded charging state.

6. The method for determining the state of a high-voltage direct current transmission system according to claim 4, characterized in that: In step S1, when the load current value of the line is greater than X or the current mutation value is greater than Y, and the input value S of the SR trigger is 1, R is 0, and the output value Q is 1, it is determined that the line has switched from the no-charge state to the running state.

7. The method for determining the state of a high-voltage direct current transmission system according to claim 4, characterized in that: In step S1, when the load current value of the line is less than X and the current mutation value is less than Z, and the input value S of the SR trigger is 0, R is 1, and the output value Q is 0, it is determined that the line has switched from the running state to the no-charge state.

8. The method for determining the state of a high-voltage direct current transmission system according to claim 1, characterized in that: Step S1 also includes determining the operating status of the circuit breaker.

9. A device, said device being an electronic device, characterized in that: The system includes a memory and a processor that are coupled to each other, the processor being used to execute program instructions stored in the memory to implement the method for determining the state of the high-voltage direct current transmission system according to any one of claims 1 to 8.

10. A medium, said medium being a computer-readable storage medium having program instructions stored thereon, characterized in that: When the program instructions are executed by the processor, they implement the method for determining the state of the high-voltage direct current transmission system as described in any one of claims 1 to 8.

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