Multi-station and direct-current power transmission system joint frequency control method and related device

Abstract

The invention discloses a multi-station and direct-current power transmission system joint frequency control method and a related device, whether frequency control is performed by primary frequency modulation and secondary frequency modulation of stations is determined based on alternating-current frequency and communication states of the stations, and under the condition of normal communication, the primary frequency modulation function of the stations is shielded, so that the communication efficiency of the stations is improved. And issuing an active power adjustment value and a power adjustment rate, then determining whether to end frequency control based on whether the AC frequency is in a control dead zone, and in the case of abnormal communication, giving the frequency control right to primary frequency modulation and secondary frequency modulation of the station for frequency control. The problems that in an existing power generation control system integrating wind power, photovoltaic, energy storage and pumped storage power stations, joint coordination frequency control between each station and a direct-current power transmission system is not considered, and great inconvenience is brought to operation and maintenance of a wind and light storage flexible direct-current looped network joint power generation system; and the system operation is difficult to meet the ever-increasing refinement requirement.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular, to a joint frequency control method and related devices for multiple power stations and a DC transmission system. Background Art

[0002] The variable speed technology implementation methods of variable speed pumped storage units are divided into two types: stepped speed regulation and continuous speed regulation. Stepped speed regulation includes pole-changing speed regulation and double-rotor double-stator speed regulation. Continuous speed regulation includes stator-side variable frequency speed regulation and variable frequency AC excitation speed regulation. The motor part of the variable frequency AC excitation speed regulation uses a doubly-fed motor, and the AC excitation frequency conversion is realized through a back-to-back power electronic converter.

[0003] The overall structure of a doubly-fed variable speed pumped storage unit is as Figure 1 shown. The pump-turbine serves as a prime mover or load, providing or consuming power. The stator of the doubly-fed motor is the same as that of a traditional salient-pole synchronous motor, and the rotor has a symmetrically distributed three-phase winding, which is connected to the power grid through a converter and a transformer to exchange power with the power grid. The amplitude, frequency, and phase of the voltage or current output by the converter are controlled by an AC excitation regulator.

[0004] New energy represented by photovoltaic and wind power has become an important direction for energy development due to its pollution-free and renewable characteristics and no greenhouse gas emissions. With the emergence of large-scale wind power and photovoltaic power generation bases, the proportion of new energy at the DC sending end is continuously expanding and will become the main power source. In the power generation control systems integrating wind power, photovoltaics, energy storage, and pumped storage power stations, the joint coordinated frequency control between each power station and the DC transmission system is not considered, which brings great inconvenience to the operation and maintenance of the wind-solar-storage-soft DC ring network combined power generation system, and it is also difficult for the system operation to meet the increasing refined requirements. Summary of the Invention

[0005] The present invention provides a joint frequency control method and related devices for multiple power stations and a DC transmission system, which are used to solve the technical problem that in the existing power generation control systems integrating wind power, photovoltaics, energy storage, and pumped storage power stations, the joint coordinated frequency control between each power station and the DC transmission system is not considered, which brings great inconvenience to the operation and maintenance of the wind-solar-storage-soft DC ring network combined power generation system, and it is also difficult for the system operation to meet the increasing refined requirements.

[0006] In view of this, the first aspect of the present invention provides a joint frequency control method for multiple power stations and a DC transmission system, including the following steps:

[0007] S1. Real-time monitor whether the AC frequency exceeds a preset range through a multi-power station and DC frequency control coordination system. If so, execute step S2;

[0008] S2. Determine the communication status between the DC frequency control coordination system and each power station. For power stations with normal communication, execute step S3; for power stations with abnormal communication, jump to step S7;

[0009] S3. Shield the preset time of the primary frequency regulation function of each power station, and according to the power adjustment speed of each power station, issue the first active power adjustment value and the first power adjustment rate through the DC frequency control coordination system;

[0010] S4. After the first preset time, detect whether the AC frequency is adjusted to the control dead zone. If so, the combined frequency control ends; if not, execute step S5;

[0011] S5. According to the current degree of AC frequency deviation and the adjustment capabilities of the units at each power station, issue the second active power adjustment value and the second power adjustment rate through the DC frequency control coordination system;

[0012] S6. After the second preset time, detect whether the AC frequency is adjusted to the control dead zone. If so, the combined frequency control ends; if not, execute step S7;

[0013] S7. Hand over the frequency control right to the primary frequency regulation and secondary frequency regulation of the power station;

[0014] S8. Based on the primary frequency regulation of the power station, adjust the active power of the power station according to the preset correlation fixed value;

[0015] S9. After the third preset time, detect whether the AC frequency exceeds the adjustment range of the primary frequency regulation. If so, switch the AC frequency control to the secondary frequency regulation and execute step S10; if not, the combined frequency control ends;

[0016] S10. After the fourth preset time, detect whether the AC frequency is adjusted to the control dead zone. If so, the combined frequency control ends; if not, perform power increase or power reduction or load shedding through the security and stability control switching device.

[0017] Optionally, the preset range is 49.95 Hz to 50.05 Hz, and the control dead zone is 49.95 Hz to 50.05 Hz.

[0018] Optionally, the strategy for issuing the active power adjustment value is:

[0019] According to the power that each power station can increase, it is preferentially allocated to DC units, new energy power station units, and variable-speed pumped-storage units according to coefficients, and finally allocated to conventional pumped-storage units;

[0020] The increased power issued to the DC unit is:

[0021]

[0022] Among them, is the increased power sent to the DC unit, P is the active power deficit, is the total increased power, is the increased power that the DC unit can provide;

[0023] The increased power sent to the units of the new energy power station is:

[0024]

[0025] Among them, is the increased power sent to the units of the new energy power station, is the increased power that the units of the new energy power station can provide;

[0026] The increased power sent to the variable-speed pumped storage units is:

[0027]

[0028] Among them, is the increased power sent to the variable-speed pumped storage units, is the increased power that the variable-speed pumped storage units can provide;

[0029] The increased power sent to the conventional pumped storage units is:

[0030]

[0031] Among them, is the increased power sent to the conventional pumped storage units, is the increased power that the conventional pumped storage units can provide.

[0032] Optionally, the preset time is 1 s.

[0033] Optionally, the first preset time, the second preset time, and the third preset time are all 0.5 s.

[0034] The second aspect of the present invention provides a multi-power station and DC power transmission system joint frequency control device, including the following modules:

[0035] An AC frequency monitoring module, configured to monitor in real time whether the AC frequency exceeds a preset range through the multi-power station and DC frequency control coordination system. If so, jump to the communication judgment module;

[0036] A communication judgment module, configured to judge the communication status between the DC frequency control coordination system and each power station. For the power stations with normal communication, jump to the first adjustment module, and for the power stations with abnormal communication, jump to the frequency control main body adjustment module;

[0037] The first adjustment module is used to mask the preset time of the primary frequency regulation function of each power station. According to the power regulation speed of each power station, the first active power adjustment value and the first power adjustment rate are sent down through the DC frequency control coordination system;

[0038] The first judgment module is used to detect whether the AC frequency is adjusted to the control dead zone after the first preset time. If so, the combined frequency control ends. If not, it jumps to the secondary adjustment module;

[0039] The secondary adjustment module is used to send down the second active power adjustment value and the second power adjustment rate through the DC frequency control coordination system according to the current AC frequency deviation degree and the adjustment ability of each power station's unit;

[0040] The second judgment module is used to detect whether the AC frequency is adjusted to the control dead zone after the second preset time. If so, the combined frequency control ends. If not, it jumps to the main body adjustment module of frequency control;

[0041] The main body adjustment module of frequency control is used to hand over the frequency control right to the primary frequency regulation and secondary frequency regulation of the power station;

[0042] The power station power adjustment module is used to adjust the active power of the power station based on the primary frequency regulation of the power station according to the preset correlation fixed value;

[0043] The third judgment module is used to detect whether the AC frequency exceeds the adjustment range of the primary frequency regulation after the third preset time. If so, the AC frequency control is switched to the secondary frequency regulation, and it jumps to the fourth judgment module. If not, the combined frequency control ends;

[0044] The fourth judgment module is used to detect whether the AC frequency is adjusted to the control dead zone after the fourth preset time. If so, the combined frequency control ends. If not, power increase or power reduction or load shedding is carried out through the safety and stability control switching device.

[0045] Optionally, the preset range is 49.95Hz to 50.05Hz, and the control dead zone is 49.95Hz to 50.05Hz.

[0046] Optionally, the strategy for sending down the active power adjustment value is:

[0047] According to the power that each power station can increase, it is preferentially allocated to the DC units, new energy power station units and variable-speed pumped storage units according to the coefficient, and finally allocated to the conventional pumped storage units;

[0048] The increased power sent down to the DC unit is:

[0049]

[0050] Wherein, is the increased power sent to the DC unit, and P is the active power deficit. is the total increased power. is the increased power that the DC unit can provide.

[0051] The increased power sent to the units of the new energy power station is:

[0052]

[0053] Among them, is the increased power sent to the units of the new energy power station, is the increased power that the units of the new energy power station can provide.

[0054] The increased power sent to the variable-speed pumped-storage units is:

[0055]

[0056] Among them, is the increased power sent to the variable-speed pumped-storage units, is the increased power that the variable-speed pumped-storage units can provide.

[0057] The increased power sent to the conventional pumped-storage units is:

[0058]

[0059] Among them, is the increased power sent to the conventional pumped-storage units, is the increased power that the conventional pumped-storage units can provide.

[0060] Optionally, the preset time is 1 s.

[0061] Optionally, the first preset time, the second preset time, and the third preset time are all 0.5 s.

[0062] The third aspect of the present invention provides a multi-station and HVDC system combined frequency control device, and the device includes a processor and a memory:

[0063] The memory is used to store program codes and transmit the program codes to the processor;

[0064] The processor is used to execute any one of the multi-station and HVDC system combined frequency control methods described in the first aspect according to the instructions in the program codes.

[0065] The fourth aspect of the present invention provides a computer-readable storage medium, and the computer-readable storage medium is used to store program codes, and the program codes are used to execute any one of the multi-station and HVDC system combined frequency control methods described in the first aspect.

[0066] As can be seen from the above technical solutions, the multi-station and HVDC transmission system combined frequency control method provided by the present invention has the following advantages:

[0067] The multi-station and HVDC transmission system combined frequency control method provided by the present invention determines whether to perform frequency control by the primary frequency regulation and secondary frequency regulation of the station based on the AC frequency sum and the communication status of each station. When the communication is normal, the primary frequency regulation function of the station is shielded, the active power adjustment value and the power adjustment rate are issued, and then it is determined whether to end the frequency control based on whether the AC frequency is within the control dead zone. When the communication is abnormal, the frequency control right is handed over to the primary frequency regulation and secondary frequency regulation of the station to perform frequency control, realizing the combined frequency control of multiple stations and the HVDC transmission system, and solving the technical problem that in the existing power generation control systems integrating wind power, photovoltaic power, energy storage, and pumped storage power stations, the combined coordinated frequency control between each station and the HVDC transmission system is not considered, which brings great inconvenience to the operation and maintenance of the wind-solar-storage flexible DC loop network combined power generation system, and it is also difficult for the system operation to meet the increasing refined requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for describing the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0069] Figure 1 It is a schematic diagram of the overall structure of a variable-speed pumped storage unit;

[0070] Figure 2 It is a schematic flow chart of a multi-station and HVDC transmission system combined frequency control method provided in an embodiment of the present invention;

[0071] Figure 3 It is a schematic diagram of the structure of a multi-station and HVDC transmission system combined frequency control device provided in an embodiment of the present invention;

[0072] Figure 4 It is a schematic diagram of the structure of a multi-station and HVDC transmission system combined frequency control device provided in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0073] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0074] For ease of understanding, please refer to Figure 2 , an embodiment of a joint frequency control method for multiple power stations and a DC transmission system provided by the present invention includes:

[0075] Step S1: The multiple power stations and the DC frequency control coordination system continuously monitor whether the AC frequency exceeds a preset range. If so, step S2 is executed.

[0076] It should be noted that a DC transmission project mainly consists of converter stations (rectifier stations and inverter stations), DC lines, power filters on the AC side and DC side, reactive power compensation devices, converter transformers, DC reactors, as well as protection and control devices, etc. The alternating current generated by a power plant is converted into direct current by a rectifier and transmitted to the receiving end, and then the direct current is converted into alternating current by an inverter and sent to the receiving-end AC power grid. The multiple power stations in the embodiments of the present invention include pumped-storage power stations (including conventional pumped-storage and variable-speed pumped-storage) and intensive new energy bases (including energy storage, wind turbines, and photovoltaic). The DC frequency control coordination system can issue commands to the power stations and the DC transmission system to control their DC power adjustment amounts and adjustment rates.

[0077] In the embodiments of the present invention, the preset range is 49.95 Hz to 50.05 Hz.

[0078] Step S2: Determine the communication status between the DC frequency control coordination system and each power station. For power stations with normal communication, step S3 is executed. For power stations with abnormal communication, jump to step S7.

[0079] It should be noted that when the multiple power stations and the DC frequency control coordination system monitor that the AC frequency exceeds the preset range, it is necessary to determine whether the communication between the DC frequency control coordination system and each power station is normal. If the communication of a single power station is abnormal, the coefficient of this power station participating in frequency control is excluded (i.e., set to zero), and it is defaulted that the frequency control right of the power station with communication failure is handed over to the power station.

[0080] Step S3: Shield the preset time of the primary frequency regulation function of each power station, and issue the first active power adjustment value and the first power adjustment rate through the DC frequency control coordination system according to the power adjustment speed of each power station.

[0081] It should be noted that for the stations with normal communication, the preset time for shielding the primary frequency regulation function of the station is set, and the preset time value is 1 s. Then, the DC frequency control coordination system issues the first active power adjustment value and the first power adjustment rate according to the power adjustment speed of the station.

[0082] Step S4: After the first preset time, detect whether the AC frequency is adjusted to the control dead zone. If so, the combined frequency control ends; if not, execute Step S5.

[0083] It should be noted that the value of the first preset time is 0.5 s. After the first preset time, detect whether the AC frequency is adjusted to the control dead zone, and the control dead zone is 49.95 Hz to 50.05 Hz. If the AC frequency is within the control dead zone, the frequency control ends. If the AC frequency does not fall into the control dead zone, jump to Step S5 to continue the frequency control.

[0084] Step S5: According to the current AC frequency deviation degree and the adjustment capabilities of the units at each station, the DC frequency control coordination system issues the second active power adjustment value and the second power adjustment rate.

[0085] It should be noted that for example, currently the AC side frequency is 49.8 Hz and the frequency deviation is -0.2 Hz. Through real-time adjustment data, the active power shortage P corresponding to the frequency deviation of -0.2 Hz is 2000 MW. According to the power that can be increased by each station and distributed according to coefficients, it is preferentially distributed to DC units, new energy station units, and variable-speed pumped storage units, and finally to conventional pumped storage units. The power capacity that can be increased by each station is: the power that can be increased by the DC unit = 1800 MW, the power that can be increased by the new energy station unit = 800 MW, the power that can be increased by the variable-speed pumped storage unit = 300 MW, the power that can be increased by the conventional pumped storage unit = 200 MW.

[0086] The increased power issued to the DC unit is:

[0087]

[0088] Wherein, is the increased power issued to the DC unit, P is the active power shortage, is the total increased power, is the power that can be increased by the DC unit;

[0089] The increased power issued to the new energy station unit is:

[0090]

[0091] Among them, is the increased power sent to the units of the new energy power station, P is the active power deficit, is the total increased power, is the increased power that can be provided by the units of the new energy power station;

[0092] The increased power sent to the variable-speed pumped storage units is:

[0093]

[0094] Among them, is the increased power sent to the variable-speed pumped storage units, P is the active power deficit, is the total increased power, is the increased power that can be provided by the variable-speed pumped storage units;

[0095] The increased power sent to the conventional pumped storage units is:

[0096]

[0097] Among them, is the increased power sent to the conventional pumped storage units, P is the active power deficit, is the total increased power, is the increased power that can be provided by the conventional pumped storage units.

[0098] The distribution coefficient of the total increased power is a coefficient comprehensively considered by the agreed priority and the optimal capacity. In the embodiments of the present invention, .

[0099] The algorithms of the first active power adjustment and the second active power adjustment are the same.

[0100] The increased rate sent to the DC units is 9999 MW / min.

[0101] The increased rate sent to the units of the new energy power station is 9999 MW / min.

[0102] The increased rate sent to the variable-speed pumped storage units is 9999 MW / min.

[0103] The increased rate sent to the conventional pumped storage units is 100 MW / min.

[0104] The first power adjustment rate and the second power adjustment rate sent are the same.

[0105] Step S6, after the second preset time, detect whether the AC frequency is adjusted to the control dead zone. If so, the combined frequency control ends. If not, execute step S7.

[0106] Step S7: Hand over the frequency control right to the primary frequency modulation and secondary frequency modulation of the substation yard.

[0107] It should be noted that after two frequency adjustments, if the AC frequency still cannot be adjusted to the control dead zone, the AC frequency control right will be returned to the primary frequency modulation and secondary frequency modulation of the substation yard.

[0108] Step S8: Based on the primary frequency modulation of the substation yard, adjust the active power of the substation yard according to the preset associated fixed value.

[0109] Step S9: After the third preset time, detect whether the AC frequency exceeds the adjustment range of the primary frequency modulation. If so, switch the AC frequency control to the secondary frequency modulation and execute Step S10. If not, the combined frequency control ends.

[0110] It should be noted that the third preset time is 0.5 s.

[0111] Step S10: After the fourth preset time, detect whether the AC frequency is adjusted to the control dead zone. If so, the combined frequency control ends. If not, perform power increase or power reduction or load shedding through the security and stability control switching device.

[0112] It should be noted that the fourth preset time is 0.5 s. The control strategy of the security and stability control switching device is a prior art and will not be elaborated in the present invention.

[0113] The combined frequency control method for multiple substations and a DC power transmission system provided by the present invention determines whether to perform frequency control by the primary frequency modulation and secondary frequency modulation of the substation yard based on the AC frequency and the communication status with each substation yard. When the communication is normal, the primary frequency modulation function of the substation yard is blocked, the active power adjustment value and the power adjustment rate are issued, and then it is determined whether to end the frequency control based on whether the AC frequency is within the control dead zone. When the communication is abnormal, the frequency control right is handed over to the primary frequency modulation and secondary frequency modulation of the substation yard to perform frequency control, realizing the combined frequency control of multiple substations and a DC power transmission system, and solving the technical problem that in the existing power generation control systems integrating wind power, photovoltaic power, energy storage, and pumped-storage power stations, the combined coordinated frequency control between each substation yard and the DC power transmission system is not considered, which brings great inconvenience to the operation and maintenance of the wind-solar-storage-flexible DC loop network combined power generation system, and it is difficult for the system operation to meet the increasing refined requirements.

[0114] For easy understanding, please refer to Figure 3 , and an embodiment of a combined frequency control device for multiple substations and a DC power transmission system is provided in the present invention, including the following modules:

[0115] AC frequency monitoring module, configured to monitor in real time through multiple substations and a DC frequency control coordination system whether the AC frequency exceeds a preset range. If so, jump to the communication judgment module;

[0116] A communication judgment module, configured to judge the communication status between the DC frequency control coordination system and each station. For stations with normal communication, it jumps to the first adjustment module; for stations with abnormal communication, it jumps to the frequency control main body adjustment module.

[0117] The first adjustment module is configured to shield the primary frequency modulation function preset time of each station, and according to the power adjustment speed of each station, send the first active power adjustment value and the first power adjustment rate through the DC frequency control coordination system.

[0118] The first judgment module is configured to detect whether the AC frequency is adjusted to the control dead zone after a first preset time. If so, the combined frequency control ends; if not, it jumps to the second adjustment module.

[0119] The second adjustment module is configured to send the second active power adjustment value and the second power adjustment rate through the DC frequency control coordination system according to the current AC frequency deviation degree and the adjustment capabilities of the units at each station.

[0120] The second judgment module is configured to detect whether the AC frequency is adjusted to the control dead zone after a second preset time. If so, the combined frequency control ends; if not, it jumps to the frequency control main body adjustment module.

[0121] The frequency control main body adjustment module is configured to hand over the frequency control right to the primary frequency modulation and secondary frequency modulation of the station.

[0122] The station power adjustment module is configured to adjust the active power of the station based on the primary frequency modulation of the station according to a preset associated fixed value.

[0123] The third judgment module is configured to detect whether the AC frequency exceeds the adjustment range of the primary frequency modulation after a third preset time. If so, it switches the AC frequency control to the secondary frequency modulation and jumps to the fourth judgment module; if not, the combined frequency control ends.

[0124] The fourth judgment module is configured to detect whether the AC frequency is adjusted to the control dead zone after a fourth preset time. If so, the combined frequency control ends; if not, it performs power increase or power reduction or load shedding through the security and stability control switching device.

[0125] In one embodiment, the preset range is exceeded for 49.95 Hz to 50.05 Hz, and the control dead zone is 49.95 Hz to 50.05 Hz.

[0126] In one embodiment, the strategy for sending the active power adjustment value is as follows:

[0127] According to the power that can be increased at each station, it is preferentially allocated to DC units, new energy station units, and variable-speed pumped storage units according to a coefficient, and finally allocated to conventional pumped storage units;

[0128] The increased power sent to the DC unit is:

[0129]

[0130] Among them, is the increased power sent to the DC unit, P is the active power deficit, is the total increased power, is the power that the DC unit can increase;

[0131] The increased power sent to the new energy station unit is:

[0132]

[0133] Among them, is the increased power sent to the new energy station unit, is the power that the new energy station unit can increase;

[0134] The increased power sent to the variable-speed pumped storage unit is:

[0135]

[0136] Among them, is the increased power sent to the variable-speed pumped storage unit, is the power that the variable-speed pumped storage unit can increase;

[0137] The increased power sent to the conventional pumped storage unit is:

[0138]

[0139] Among them, is the increased power sent to the conventional pumped storage unit, is the power that the conventional pumped storage unit can increase.

[0140] In one embodiment, the preset time is 1 s.

[0141] In one embodiment, the first preset time, the second preset time, and the third preset time are all 0.5 s.

[0142] For ease of understanding, please refer to Figure 4 , an embodiment of a multi-station and DC power transmission system joint frequency control device is also provided in the present invention. The device includes a processor and a memory:

[0143] The memory is used to store program code and transfer the program code to the processor;

[0144] The processor is used to execute any one of the implementation manners in the foregoing embodiments of the multi-station and HVDC system combined frequency control method according to the instructions in the program code.

[0145] An embodiment of a computer-readable storage medium is further provided in the present invention. The computer-readable storage medium is used to store program code, and the program code is used to execute any one of the implementation manners in the foregoing embodiments of the multi-station and HVDC system combined frequency control method.

[0146] An embodiment of a computer program product including instructions is further provided in the present invention. When it runs on a computer, it causes the computer to execute any one of the implementation manners in the foregoing embodiments of the multi-station and HVDC system combined frequency control method.

[0147] The multi-station and HVDC system combined frequency control device, equipment, computer-readable storage medium, and computer program product including instructions provided in the present invention are all used to execute the multi-station and HVDC system combined frequency control method provided in the present invention. Their principles and achieved technical effects are the same as those of the multi-station and HVDC system combined frequency control method provided in the present invention, and will not be described in detail here.

[0148] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the systems, devices, and units described above can refer to the corresponding processes in the foregoing method embodiments, and will not be described in detail here.

[0149] The terms "first", "second", "third", "fourth", etc. in the specification of the present invention and the above drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order different from those illustrated or described here. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0150] It should be understood that in the present invention, "at least one (item)" means one or more, and "a plurality" means two or more. "And / or" is used to describe the relationship between associated objects, indicating that there can be three relationships. For example, "A and / or B" can mean: only A exists, only B exists, and both A and B exist at the same time. Here, A and B can be singular or plural. The character " / " generally indicates an "or" relationship between the associated objects before and after. "At least one (item) of the following" or a similar expression means any combination of these items, including any combination of a single item or multiple items. For example, at least one (item) of a, b, or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0151] In several embodiments provided by the present invention, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there can be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections between each other can be through some interfaces. The indirect couplings or communication connections of devices or units can be in electrical, mechanical, or other forms.

[0152] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0153] In addition, in each embodiment of the present invention, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above integrated units can be implemented in the form of hardware or in the form of software functional units.

[0154] When the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The foregoing storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories (English full name: Read-Only Memory, English abbreviation: ROM), random access memories (English full name: Random Access Memory, English abbreviation: RAM), magnetic disks, or optical discs.

[0155] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of various embodiments of the present invention.

Claims

1. A combined frequency control method for multiple power stations and a DC power transmission system, characterized in that, It includes the following steps: S1. Use the multi-station and DC frequency control coordination system to monitor in real time whether the AC frequency exceeds the preset range. If so, execute step S2; S2. Judge the communication status between the DC frequency control coordination system and each station. For stations with normal communication, execute step S3. For stations with abnormal communication, jump to step S7; S3. Shield the preset time of the primary frequency regulation function of each station. According to the power regulation speed of each station, issue the first active power adjustment value and the first power adjustment rate through the DC frequency control coordination system; S4. After the first preset time, detect whether the AC frequency is adjusted to the control dead zone. If so, the combined frequency control ends. If not, execute step S5; S5. According to the current degree of AC frequency deviation and the regulation ability of each station's unit, issue the second active power adjustment value and the second power adjustment rate through the DC frequency control coordination system; S6. After the second preset time, detect whether the AC frequency is adjusted to the control dead zone. If so, the combined frequency control ends. If not, execute step S7; S7. Hand over the frequency control right to the primary frequency regulation and secondary frequency regulation of the station; S8. Based on the primary frequency regulation of the station, adjust the active power of the station according to the preset correlation fixed value; S9. After the third preset time, detect whether the AC frequency exceeds the adjustment range of the primary frequency regulation. If so, switch the AC frequency control to the secondary frequency regulation and execute step S10. If not, the combined frequency control ends; S10. After the fourth preset time, detect whether the AC frequency is adjusted to the control dead zone. If so, the combined frequency control ends. If not, perform power increase or power reduction or load shedding through the security and stability control switching device.

2. The combined frequency control method for multi-station and HVDC transmission system according to claim 1, wherein The preset range is 49.95Hz to 50.05Hz, and the control dead zone is 49.95Hz to 50.05Hz.

3. The combined frequency control method for multiple substations and HVDC transmission system according to claim 1, wherein The strategy for issuing the active power adjustment value is: According to the power that each station can increase, it is preferentially allocated to the DC units, new energy station units, and variable-speed pumped storage units according to the coefficient, and finally allocated to the conventional pumped storage units; The increased power issued to the DC units is: Among them, is the increased power sent to the DC unit, P is the active power deficit, is the total increased power, is the increased power that the DC unit can provide; The increased power issued to the new energy station units is: Among them, is the increased power sent to the new energy power station units, is the increased power that the new energy power station units can achieve; The increased power issued to the variable-speed pumped storage units is: Among them, is the increased power sent to the variable-speed pumped-storage unit, is the increased power that the variable-speed pumped-storage unit can achieve; The increased power issued to the conventional pumped storage units is: Among them, is the increased power sent to the conventional pumped-storage unit, is the power that the conventional pumped-storage unit can increase.

4. The combined frequency control method for multiple substations and HVDC transmission system according to claim 1, characterized in that, The preset time is 1s.

5. The combined frequency control method for multi-station and HVDC transmission system according to claim 1, wherein The first preset time, the second preset time, and the third preset time are all 0.5s.

6. A combined frequency control device for multiple power stations and HVDC transmission system, characterized in that It includes the following modules: AC frequency monitoring module, which is used to use the multi-station and DC frequency control coordination system to monitor in real time whether the AC frequency exceeds the preset range. If so, jump to the communication judgment module; Communication judgment module, which is used to judge the communication status between the DC frequency control coordination system and each station. For stations with normal communication, jump to the first adjustment module. For stations with abnormal communication, jump to the frequency control main body adjustment module; First adjustment module, which is used to shield the preset time of the primary frequency regulation function of each station. According to the power regulation speed of each station, issue the first active power adjustment value and the first power adjustment rate through the DC frequency control coordination system; The first judgment module is used to detect whether the AC frequency is adjusted to the control dead zone after the first preset time. If so, the combined frequency control ends. If not, it jumps to the secondary adjustment module; The secondary adjustment module is used to issue the second active power adjustment value and the second power adjustment rate through the DC frequency control coordination system according to the current AC frequency deviation degree and the adjustment capabilities of the units at each substation; The second judgment module is used to detect whether the AC frequency is adjusted to the control dead zone after the second preset time. If so, the combined frequency control ends. If not, it jumps to the main body adjustment module of frequency control; The main body adjustment module of frequency control is used to hand over the frequency control right to the primary frequency modulation and secondary frequency modulation of the substation; The substation power adjustment module is used to adjust the active power of the substation based on the primary frequency modulation of the substation according to the preset associated fixed value; The third judgment module is used to detect whether the AC frequency exceeds the adjustment range of the primary frequency modulation after the third preset time. If so, it switches the AC frequency control to the secondary frequency modulation and jumps to the fourth judgment module. If not, the combined frequency control ends; The fourth judgment module is used to detect whether the AC frequency is adjusted to the control dead zone after the fourth preset time. If so, the combined frequency control ends. If not, it performs power increase or power reduction or load shedding through the safety and stability control switching device.

7. The combined frequency control device for multiple substations and HVDC transmission system according to claim 6, wherein The preset range is exceeded at 49.95Hz - 50.05Hz, and the control dead zone is 49.95Hz - 50.05Hz.

8. The combined frequency control device for multi-station and HVDC transmission system according to claim 6, characterized in that The strategy for issuing the active power adjustment value is as follows: According to the power that can be increased by each substation, it is preferentially allocated to the DC units, new energy substation units, and variable-speed pumped storage units according to coefficients, and finally allocated to the conventional pumped storage units; The increased power issued to the DC units is: Among them, is the increased power sent to the DC unit, P is the active power deficit, is the total increased power, is the increased power that the DC unit can provide; The increased power issued to the new energy substation units is: Among them, is the increased power sent to the new energy power station units, is the power that the new energy power station units can increase; The increased power issued to the variable-speed pumped storage units is: Among them, is the increased power sent to the variable-speed pumped-storage unit, is the increased power that the variable-speed pumped-storage unit can achieve; The increased power issued to the conventional pumped storage units is: Among them, is the increased power sent to the conventional pumped-storage unit, is the increased power that the conventional pumped-storage unit can achieve.

9. A combined frequency control device for multiple power stations and a DC power transmission system, characterized in that The device includes a processor and a memory: The memory is used to store the program code and transmit the program code to the processor; The processor is used to execute the multi-substation and DC power transmission system combined frequency control method according to any one of claims 1 - 5 based on the instructions in the program code.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store the program code, and the program code is used to execute the multi-substation and DC power transmission system combined frequency control method according to any one of claims 1 - 5.

Images