Converter blocking control method and device for extra-high voltage converter station
In ultra-high voltage direct current transmission projects with dual converters located separately, different converter blocking strategies are adopted according to the location and type of fault to clear the fault current and isolate the fault point. This solves the problem that conventional strategies are not applicable and enables the continuous operation of non-faulty converters and improves system stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XJ GRP CORP
- Filing Date
- 2022-11-11
- Publication Date
- 2026-06-19
AI Technical Summary
In conventional UHVDC transmission projects, the protection action blocking strategy is not applicable to UHV projects with dual converters located separately, which leads to the inability of non-faulty converters to continue operating, resulting in severe power loss in the system and poor grid stability.
Different converter blocking strategies are adopted. Based on the location and type of fault, the fault current is cleared by controlling the grounding electrode circuit and switch status of the high-end converter station, a new grounding electrode circuit is established and the fault point is isolated to ensure that the non-faulty converters continue to operate.
While isolating faults, we can ensure that non-faulty converters continue to operate to the greatest extent possible, reduce system power transmission losses, reduce grid impact, and improve the stability of DC transmission.
Smart Images
Figure CN115693620B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of DC transmission protection technology, specifically relating to a converter interlocking control method and device for an ultra-high voltage converter station. Background Technology
[0002] When there are two power supply points at the sending end or two power receiving points at the receiving end of an ultra-high voltage direct current transmission project, and they are far apart, a scheme of constructing dual converters at separate sites and configuring grounding electrodes for each converter station can be adopted.
[0003] In conventional UHVDC transmission projects, the blocking strategy for protection actions is relatively simple:
[0004] 1) When the protection actions of the pole bus area, neutral bus area, DC filter area and bipolar neutral bus area are blocked, pole blocking and pole isolation are directly executed;
[0005] 2) When the differential protection of the converter in the converter area is blocked, the pole blocking is executed first, and the non-faulty converter is restarted after isolating the faulty converter.
[0006] 3) When other protection actions in the converter zone, except for the converter differential protection, are blocked, the converter is directly blocked and the converter is isolated.
[0007] The structure of UHV projects with dual converters built at separate sites is complex. The high-end and low-end converter stations are built at separate sites and each is equipped with a grounding electrode. The blocking strategy used in conventional UHVDC transmission projects when protection actions are blocked is no longer applicable. On the one hand, both the high-end and low-end converter stations have complete pole bus areas, neutral bus areas, DC filter areas, and bipolar neutral bus areas. Under the premise of ensuring fault isolation, the non-faulty converters should be able to continue to operate to the greatest extent possible. Pole blocking and pole isolation cannot be simply implemented. On the other hand, when a fault in the converter area causes the protection action to be blocked, the fault isolation can be completed by switching the grounding electrode, thereby ensuring the normal operation of the other converter. Summary of the Invention
[0008] The purpose of this invention is to provide a converter interlocking control method and device for ultra-high voltage converter stations, in order to solve the problem that the interlocking strategy used in conventional ultra-high voltage DC transmission projects is no longer applicable to ultra-high voltage projects with dual converters located separately.
[0009] To solve the above-mentioned technical problems, the present invention provides a converter interlocking control method for an ultra-high voltage converter station, which adopts at least one of the following schemes for interlocking control of the ultra-high voltage converter station;
[0010] Option 1: If all protection actions of the low-end converter station are blocked, and the grounding electrode circuit of the high-end converter station is in the isolation state of circuit breaker open and disconnector closed, then first control the high-end converter to clear the fault current by phase shifting, then control the high-end converter station to establish a new grounding electrode circuit and isolate the fault point, and then control the high-end converter to release the phase shifting.
[0011] Option 2: If all protection actions of the low-end converter station are blocked, and a disconnector in the grounding electrode circuit of the high-end converter station is in the open position, then first execute the electrode blocking to clear the fault current, then control the high-end converter station to establish a new grounding electrode circuit to isolate the fault point, and finally restart the non-faulty converter.
[0012] Option 3: If any protection in the converter area of the low-end converter station, except for the converter differential protection, is blocked, the faulty converter is blocked first and switched to isolation state. Then, the high-end converter station is controlled to establish a new grounding electrode circuit and isolate the fault point.
[0013] Option 4: If the protection of the DC filter area of the high-end converter station is blocked, first execute the polar blocking to clear the current flowing through the DC filter, then switch the DC filter to isolation state to isolate the fault point, and finally restart the low-end converter.
[0014] Its beneficial effects are as follows: When dual converters are in operation, in the face of a situation where a fault causes the converter protection or pole protection to be blocked, the present invention adopts different converter blocking strategies according to the different fault locations and fault types. Under the premise of isolating the fault, it can ensure that the non-faulty converters can continue to operate to the greatest extent, reduce the loss of system transmission power, reduce the impact on the power grid when the system is blocked, and improve the stability of DC transmission.
[0015] Furthermore, in Schemes 1, 2, and 3, the means to control the high-end converter station to establish a new grounding electrode circuit and isolate the fault point are as follows: close the circuit breaker and disconnect switch on the neutral line of the high-end converter station to switch the high-end converter station grounding electrode circuit to the connected state and establish a new grounding electrode circuit; disconnect the high-speed parallel switch on the low-end converter station side and the neutral bus switch of the low-end converter station on the high-low end busbar to disconnect the low-end grounding electrode circuit and isolate the fault point.
[0016] Its beneficial effects are as follows: by first closing the circuit breakers and disconnectors such as the neutral bus switch of the high-end converter station, and then disconnecting the high-speed parallel switch on the low-end converter station side of the low-end busbar and the neutral bus switch of the low-end converter station, it is ensured that at least one grounding electrode circuit is in a connected state, thus ensuring the normal operation of the system.
[0017] Furthermore, the various protection actions described in Scheme 1 and Scheme 2 include converter differential protection in the converter area, pole bus area protection, neutral bus area protection, and DC filter area protection.
[0018] Its beneficial effects are: equipped with various protections, it can ensure the safe and stable operation of the system.
[0019] To address the aforementioned technical problems, the present invention also provides a converter interlocking control device for an ultra-high voltage converter station, comprising a processor and a memory, wherein the processor is used to execute program instructions stored in the memory to implement the following method:
[0020] The converter is locked out using at least one of the following schemes:
[0021] Option 1: If all protection actions of the low-end converter station are blocked, and the grounding electrode circuit of the high-end converter station is in the isolation state of circuit breaker open and disconnector closed, then first control the high-end converter to clear the fault current by phase shifting, then control the high-end converter station to establish a new grounding electrode circuit and isolate the fault point, and then control the high-end converter to release the phase shifting.
[0022] Option 2: If all protection actions of the low-end converter station are blocked, and a disconnector in the grounding electrode circuit of the high-end converter station is in the open position, then first execute the electrode blocking to clear the fault current, then control the high-end converter station to establish a new grounding electrode circuit to isolate the fault point, and finally restart the non-faulty converter.
[0023] Option 3: If any protection in the converter area of the low-end converter station, except for the converter differential protection, is blocked, the faulty converter is blocked first and switched to isolation state. Then, the high-end converter station is controlled to establish a new grounding electrode circuit and isolate the fault point.
[0024] Option 4: If the protection of the DC filter area of the high-end converter station is blocked, first execute the polar blocking to clear the current flowing through the DC filter, then switch the DC filter to isolation state to isolate the fault point, and finally restart the low-end converter.
[0025] Its beneficial effects are as follows: When dual converters are in operation, in the face of a situation where a fault causes the converter protection or pole protection to be blocked, the present invention adopts different converter blocking strategies according to the different fault locations and fault types. Under the premise of isolating the fault, it can ensure that the non-faulty converters can continue to operate to the greatest extent, reduce the loss of system transmission power, reduce the impact on the power grid when the system is blocked, and improve the stability of DC transmission.
[0026] Furthermore, in Schemes 1, 2, and 3, the means to control the high-end converter station to establish a new grounding electrode circuit and isolate the fault point are as follows: close the circuit breaker and disconnect switch on the neutral line of the high-end converter station to switch the high-end converter station grounding electrode circuit to the connected state and establish a new grounding electrode circuit; disconnect the high-speed parallel switch on the low-end converter station side and the neutral bus switch of the low-end converter station on the high-low end busbar to disconnect the low-end grounding electrode circuit and isolate the fault point.
[0027] Its beneficial effects are as follows: by first closing the circuit breakers and disconnectors such as the neutral bus switch of the high-end converter station, and then disconnecting the high-speed parallel switch on the low-end converter station side of the low-end busbar and the neutral bus switch of the low-end converter station, it is ensured that at least one grounding electrode circuit is in a connected state, thus ensuring the normal operation of the system.
[0028] Furthermore, the various protection actions described in Scheme 1 and Scheme 2 include converter differential protection in the converter area, pole bus area protection, neutral bus area protection, and DC filter area protection.
[0029] Its beneficial effects are: equipped with various protections, it can ensure the safe and stable operation of the system. Attached Figure Description
[0030] Figure 1 This is a topology diagram of an ultra-high voltage direct current transmission project with dual converters and separate locations, which is the subject of this invention.
[0031] Figure 2 This is a schematic diagram of the locking strategy 1 of the present invention;
[0032] Figure 3 This is a schematic diagram of the locking strategy 2 of the present invention;
[0033] Figure 4 This is a schematic diagram of the locking strategy 3 of the present invention;
[0034] Figure 5 This is a schematic diagram of the locking strategy 4 of the present invention. Detailed Implementation
[0035] This invention provides a converter interlocking strategy for the construction of UHV converter stations with separate high-end and low-end converter sites. This strategy employs different interlocking strategies when a fault occurs in different areas of the high-end and low-end converter stations, resulting in protection action interlocking.
[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, not all embodiments. Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of this invention.
[0037] Method Implementation Examples:
[0038] This invention provides a converter interlocking control method for ultra-high voltage converter stations, addressing issues such as... Figure 1 The UHVDC transmission project topology shown is used in a dual-converter operation, and the following four blocking strategies can be employed:
[0039] 1) Strategy 1: When the differential protection, pole bus area protection, neutral bus area protection, and DC filter area protection of the low-end converter station are blocked, if the grounding electrode circuit of the high-end converter station is in the standard state where all disconnectors are closed, the strategy of "low-end converter blocking, high-end converter forced phase shift—grounding electrode switching—high-end converter release of forced phase shift" is executed. The high-end converter station grounding electrode circuit is in the standard isolation state where the circuit breaker is open and all disconnectors are closed, allowing the circuit breaker to be closed and switched to the connected state in a short time. When the low-end converter station is blocked by a fault, the high-end converter station quickly establishes a new grounding electrode circuit and isolates the fault point through phase shifting. For example... Figure 2 As shown, the following locking strategy is specifically implemented:
[0040] (a) The low-end converter is locked out, and the high-end converter is forced to shift phase to clear the fault current;
[0041] (b) Combine the high-end converter station NBS, change the grounding electrode to the connected state, and establish a new grounding electrode loop;
[0042] (c) Disconnect MBTS and NBS of low-end converter station, disconnect low-end grounding electrode circuit and isolate fault point;
[0043] (d) The forced phase shift of the high-end converter is released, and the high-end converter resumes normal operation.
[0044] Among them, NBS is a neutral bus switch, which is configured on the neutral line of both high-end and low-end converter stations; MBTS is a high-speed parallel switch on the low-end converter station side of the high-end and low-end busbars.
[0045] 2) Strategy 2: When the differential protection, pole bus area protection, neutral bus area protection, and DC filter area protection of the converter zone in the low-end converter station are blocked, if a disconnector in the grounding electrode circuit of the high-end converter station is in the open position, the strategy of "pole blocking - grounding electrode switching - automatic restart of non-faulty converter" is executed. In addition to the circuit breaker, a disconnector in the grounding electrode circuit of the high-end converter station is also in the open position, requiring a certain amount of time to switch to the connected state. When the low-end converter station is blocked due to a fault, pole blocking is executed first. After the high-end converter station establishes a new grounding electrode circuit and isolates the fault point, the non-faulty converter is restarted. For example... Figure 3 As shown, the following locking strategy is specifically implemented:
[0046] (a) Execute pole blocking to disconnect both high- and low-end converters and clear fault current;
[0047] (b) Combine the high-end converter station NBS, change the grounding electrode to the connected state, and establish a new grounding electrode loop;
[0048] (c) Disconnect MBTS and NBS of low-end converter station, disconnect low-end grounding electrode circuit and isolate fault point;
[0049] (d) Perform a restart sequence control for non-faulty converters to restore the high-end converters to normal operation.
[0050] 3) Strategy 3: When any protection system in the converter zone of the low-end converter station, except for the converter differential protection, is blocked, the "low-end converter blocking, isolation—grounding electrode switching" strategy is executed. When any protection system in the converter zone of the low-end converter station, except for the converter differential protection, is blocked, it indicates that a non-grounding fault has occurred in the converter protection area. After the faulty converter is blocked, the fault point can be directly isolated through converter isolation. For example... Figure 4 As shown, the following locking strategy is specifically implemented:
[0051] (a) Block the low-end converter and switch it to isolation mode to isolate the fault point;
[0052] (b) Combine the high-end converter station NBS, change the grounding electrode to the connected state, and establish a new grounding electrode loop;
[0053] (c) Disconnect MBTS and NBS of low-end converter station, disconnect low-end grounding electrode circuit and isolate fault point.
[0054] 4) Strategy 4: When the DC filter area protection of the high-end converter station is blocked, the strategy of "polar blocking - high-end DC filter isolation - automatic restart of non-faulty converters" is executed. If only the high-end converters are blocked when the DC filter area protection of the high-end converter station is blocked, the current from the low-end converters will still flow through the high and low voltage sides of the DC filter. Therefore, if... Figure 5 As shown, the following locking strategy is specifically implemented:
[0055] (a) Execute pole blocking to disconnect both high-side and low-side converters and clear the current flowing through the DC filter;
[0056] (b) Switch the DC filter to isolation mode to isolate the fault point;
[0057] (c) Execute the non-faulty converter restart sequence control to restore the low-end converter to normal operation.
[0058] In summary, this invention is activated during dual-converter operation. If a fault causes converter protection or pole protection to trip, different converter tripping strategies are adopted based on the fault location (including the converter area, pole bus area, neutral bus area, busbar area, DC filter area, and bipolar neutral bus area of the high-end converter station, and the converter area, pole bus area, neutral bus area, DC filter area, and bipolar neutral bus area of the low-end converter station) and the fault type (including grounding faults and other types of faults). This invention proposes a converter tripping strategy for UHV converter stations with dual converters located at separate sites. When faults occur in different areas of the high-end and low-end converter stations, causing protection tripping, different tripping strategies are considered. This approach maximizes the continued operation of non-faulty converters while isolating the fault, reducing system power loss, mitigating the impact of system tripping on the power grid, and improving the stability of the DC transmission system.
[0059] Device Example:
[0060] An embodiment of a converter interlocking control device for an ultra-high voltage converter station according to the present invention includes a memory, a processor, and an internal bus. The processor and the memory communicate and interact with each other via the internal bus. The memory includes at least one software function module stored in the memory. The processor executes various functional applications and data processing by running the software programs and modules stored in the memory, thereby implementing the converter interlocking control method for an ultra-high voltage converter station described in the method embodiment of the present invention.
[0061] The processor can be a microprocessor (MCU), a programmable logic device (FPGA), or other processing devices. The memory can be any type of memory that stores information using electrical energy, such as RAM and ROM; it can also be any type of memory that stores information using magnetic energy, such as hard disks, floppy disks, magnetic tapes, magnetic core memory, bubble memory, and USB flash drives; it can also be any type of memory that stores information using optical methods, such as CDs and DVDs; and of course, it can also be other types of memory, such as quantum memory and graphene memory.
[0062] Specific implementation methods have been given above, but the present invention is not limited to the described implementation methods. The basic idea of the present invention lies in the above basic scheme. For those skilled in the art, designing various modified models, formulas, and parameters based on the teachings of the present invention does not require creative effort. Changes, modifications, substitutions, and variations made to the implementation methods without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.
Claims
1. A method of inverter blocking control of an extra-high voltage converter station, characterized in that, When both high- and low-end converters built at separate locations are in operation: If the various protection actions of the low-end converter station are blocked, and the grounding electrode circuit of the high-end converter station is in the isolation state of circuit breaker open and disconnector closed, then the high-end converter is first controlled to clear the fault current by phase shifting, then the high-end converter station is controlled to establish a new grounding electrode circuit and isolate the fault point, and then the high-end converter is controlled to release the phase shifting. If all protection actions of the low-end converter station are blocked, and a disconnector in the grounding electrode circuit of the high-end converter station is in the open position, the electrode blocking is executed first to clear the fault current, then the high-end converter station is controlled to establish a new grounding electrode circuit and isolate the fault point, and finally the non-faulty converter is restarted. If any protection in the converter area of the low-end converter station, except for the converter differential protection, is blocked, the faulty converter is blocked first and switched to isolation state, and then the high-end converter station is controlled to establish a new grounding electrode circuit and isolate the fault point. If the protection of the DC filter area of the high-end converter station is blocked, the pole blocking is first executed to clear the current flowing through the DC filter, then the DC filter is switched to isolation state to isolate the fault point, and finally the low-end converter is restarted. The means to control the high-end converter station to establish a new grounding electrode circuit and isolate the fault point are as follows: close the circuit breaker and disconnect switch on the neutral line of the high-end converter station to switch the high-end converter station grounding electrode circuit to the connected state and establish a new grounding electrode circuit; disconnect the high-speed parallel switch on the low-end converter station side and the neutral bus switch of the low-end converter station on the high-low end bus to disconnect the low-end grounding electrode circuit and isolate the fault point.
2. The converter interlocking control method for an ultra-high voltage converter station according to claim 1, characterized in that, The various protection actions include converter differential protection in the converter area, pole bus area protection, neutral bus area protection, and DC filter area protection.
3. A converter interlocking control device for an ultra-high voltage converter station, characterized in that, It includes a processor and memory, with the processor used to execute program instructions stored in memory to implement the following methods: When both the high-end and low-end converters built at separate sites are in operation: if all protection actions of the low-end converter station are blocked, and the grounding electrode circuit of the high-end converter station is in the isolation state of circuit breaker open and disconnector closed, then the high-end converter is first controlled to clear the fault current by phase shifting, then the high-end converter is controlled to establish a new grounding electrode circuit and isolate the fault point, and then the high-end converter is controlled to release the phase shifting. If all protection actions of the low-end converter station are blocked, and a disconnector in the grounding electrode circuit of the high-end converter station is in the open position, the electrode blocking is executed first to clear the fault current, then the high-end converter station is controlled to establish a new grounding electrode circuit and isolate the fault point, and finally the non-faulty converter is restarted. If any protection in the converter area of the low-end converter station, except for the converter differential protection, is blocked, the faulty converter is blocked first and switched to isolation state, and then the high-end converter station is controlled to establish a new grounding electrode circuit and isolate the fault point. If the protection of the DC filter area of the high-end converter station is blocked, the pole blocking is first executed to clear the current flowing through the DC filter, then the DC filter is switched to isolation state to isolate the fault point, and finally the low-end converter is restarted. The means to control the high-end converter station to establish a new grounding electrode circuit and isolate the fault point are as follows: close the circuit breaker and disconnect switch on the neutral line of the high-end converter station to switch the high-end converter station grounding electrode circuit to the connected state and establish a new grounding electrode circuit; disconnect the high-speed parallel switch on the low-end converter station side and the neutral bus switch of the low-end converter station on the high-low end bus to disconnect the low-end grounding electrode circuit and isolate the fault point.
4. The converter interlocking control device for an ultra-high voltage converter station according to claim 3, characterized in that, The various protection actions include converter differential protection in the converter area, pole bus area protection, neutral bus area protection, and DC filter area protection.