CN111277002A - Flexible excitation power unit parallel topology structure and control method thereof - Google Patents
Flexible excitation power unit parallel topology structure and control method thereof Download PDFInfo
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- CN111277002A CN111277002A CN202010195910.5A CN202010195910A CN111277002A CN 111277002 A CN111277002 A CN 111277002A CN 202010195910 A CN202010195910 A CN 202010195910A CN 111277002 A CN111277002 A CN 111277002A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/125—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
- H02M3/135—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
- H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
- H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/75—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
- H02M7/757—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
- H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
- H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/75—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
- H02M7/77—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means arranged for operation in parallel
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
- H02P9/10—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load
- H02P9/105—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load for increasing the stability
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0038—Circuits or arrangements for suppressing, e.g. by masking incorrect turn-on or turn-off signals, e.g. due to current spikes in current mode control
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
- H02M1/325—Means for protecting converters other than automatic disconnection with means for allowing continuous operation despite a fault, i.e. fault tolerant converters
Abstract
The invention discloses a parallel topology structure of a flexible excitation power unit and a control method thereof. The flexible excitation power unit parallel topology structure comprises a plurality of groups of flexible excitation power units which are connected in parallel, wherein each group of flexible excitation power units comprises a two-stage circuit of a front-stage bidirectional alternating current-direct current converter and a rear-stage bidirectional direct current-direct current converter, and the front-stage bidirectional alternating current-direct current converter and the rear-stage bidirectional direct current-direct current converter are connected through an intermediate direct current capacitor circuit; the input sides of the multiple groups of flexible excitation power units are respectively provided with an alternating current side filter reactor and an alternating current breaker which are connected in series, then are connected in parallel and are connected with the three-phase alternating current low-voltage side of the excitation transformer, and the three-phase alternating current high-voltage side of the excitation transformer is connected with the generator end. The parallel topology structure and the control method thereof can effectively inhibit the circulation problem among the flexible excitation power units while solving the problem of large current output of the flexible excitation system, and improve the fault-tolerant operation capability of the flexible excitation fault.
Description
Technical Field
The invention belongs to the field of generator excitation systems, and particularly relates to a parallel topology structure of a flexible excitation power unit and a control method thereof.
Background
In recent years, the ultra-high voltage alternating current and direct current transmission technology is widely applied in China, and the global energy internet strategy is rapidly promoted. In addition, in order to meet the electricity demand of rapid development of economic society and the requirements of clean emission and environmental protection, a large number of new energy machines such as wind power, photovoltaic and the like are sequentially connected into the power grid by each large power grid. The large-scale integration of renewable energy sources such as wind power, photovoltaic and the like with high proportion brings brand-new opportunities for optimizing energy structures and relieving environmental problems, but simultaneously provides a severe challenge for the operation and control of a power grid. The electric power electronic power system has increased operation risk and deficient control means in the electromagnetic/electromechanical hybrid fields of ultralow frequency power oscillation, subsynchronous oscillation, millisecond-level reactive voltage support and the like. The solution of these problems and the improvement of the equipment performance are high in cost and difficulty in taking measures in one system. If the excitation control system of the large synchronous generator and the control strategy thereof are improved, the effect is more remarkable, and the cost is greatly reduced.
At present, a conventional generator excitation system is realized based on a thyristor rectification mode of a half-control device, the control speed is low, and the device can be controlled to be switched on and not be controlled to be switched off. Therefore, the conventional excitation system can only indirectly realize the control of the excitation current, the generator terminal voltage and the reactive power of the generator by controlling the amplitude of the direct-current voltage output by rectification, and the excitation system can not realize the reverse action on the stator side while consuming a large amount of the reactive power of the generator set. Meanwhile, the excitation loop of the generator set is a large inductor, and a large rotor time constant exists physically, so that the control response speed of excitation control on the actual electrical characteristics of the generator set is severely limited. Therefore, generator excitation systems, which are critical supports for the system, have difficulty adapting to the operational requirements of the power electronics grid due to their control speed and control dimension limitations. The performance of core equipment, which relates to power grid stability control, of a generator excitation system needs to be improved from the bottom layer through innovative research of a basic power electronic topological structure and a control technology.
When the AC-DC and DC-DC power conversion circuit based on the IGBT element is applied to the field of low voltage and large current of an excitation system, the problem of weak current output capability of a single power unit exists, but the problems of engineering application such as circulation, current equalization, fault tolerance and the like exist in the case of parallel connection of multiple power units.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects in the prior art and provide a flexible excitation power unit parallel topology structure and a control method thereof, so as to realize the large current output application of a flexible excitation system, reduce the problem of circulation among power units and improve the fault-tolerant operation capability of the flexible excitation system.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a flexible excitation power unit parallel topology structure comprises a plurality of groups of flexible excitation power units which are connected in parallel, wherein each group of flexible excitation power units comprises a two-stage circuit of a front-stage bidirectional alternating current-direct current (AC-DC) converter and a rear-stage bidirectional direct current-direct current (DC-DC) converter, and the front-stage bidirectional alternating current-direct current converter and the rear-stage bidirectional direct current-direct current converter are connected through an intermediate direct current capacitor loop;
the three-phase alternating current input side of the preceding-stage bidirectional alternating current-direct current converter is the input side of the flexible excitation power unit; the direct current output side of the rear-stage bidirectional direct current-direct current converter is the output side of the flexible excitation power unit; the input sides of the multiple groups of flexible excitation power units are respectively provided with an alternating current side filter reactor and an alternating current breaker which are connected in series, then are connected in parallel and are connected with the three-phase alternating current low-voltage side of the excitation transformer, and the three-phase alternating current high-voltage side of the excitation transformer is connected with the generator end; and the output sides of the multiple groups of flexible excitation power units are respectively provided with a direct current side filter reactor and a direct current breaker which are connected in series, then are connected in parallel and are connected with the excitation winding of the generator.
Furthermore, the preceding-stage bidirectional alternating current-direct current converter adopts a three-level voltage source type converter; the rear-stage bidirectional DC-DC converter adopts a five-level H-bridge DC converter; the intermediate direct current capacitor loop comprises two groups of front and rear intermediate direct current capacitor units which are connected in parallel;
the direct current output side of the three-level voltage source type current converter is connected with the front-stage middle direct current capacitor unit through a positive electrode, a neutral point and a negative electrode; the direct-current input side of the five-level H-bridge direct-current converter is connected with the rear-stage intermediate direct-current capacitor unit through a positive electrode, a neutral point and a negative electrode;
the middle direct current capacitor unit comprises two groups of upper bridge direct current capacitor groups and lower bridge direct current capacitor groups which are mutually connected in series, the positive electrode of each upper bridge direct current capacitor group is the positive electrode of the middle direct current capacitor unit, the negative electrode of each upper bridge direct current capacitor group is connected with the positive electrode of each lower bridge direct current capacitor group to form a neutral point of the middle direct current capacitor unit, and the negative electrode of each lower bridge direct current capacitor group is the negative electrode of the middle direct current capacitor unit; the front-stage middle direct current capacitor unit and the rear-stage middle direct current capacitor unit are connected only through the positive electrode and the negative electrode.
Furthermore, the intermediate direct current capacitor loop also comprises an overvoltage protection loop, and overvoltage of the intermediate direct current capacitor loop under system fault is restrained.
Furthermore, the overvoltage protection circuit comprises an overvoltage monitoring and pulse triggering circuit, a silicon controlled loop and a nonlinear resistor; the silicon controlled rectifier circuit is connected with the nonlinear resistor in series and then is connected between the positive electrode and the negative electrode of the intermediate direct current capacitor circuit; and the overvoltage monitoring and pulse triggering circuit sends triggering pulses to the silicon controlled loop after monitoring the overvoltage, and the overvoltage suppression is realized by accessing a nonlinear resistor in the middle direct current capacitor loop.
The other technical scheme adopted by the invention is as follows: according to the control method of the parallel topological structure of the flexible excitation power units, a carrier flexible synchronous control strategy with double-path redundancy and seamless switching is adopted, parallel circulation currents output by a plurality of groups of flexible excitation power units in parallel are restrained, and the problem of circulation currents among the power units is reduced.
Further, the carrier flexible synchronization control strategy includes:
the two flexible excitation regulators respectively issue two synchronous commands to a plurality of groups of parallel flexible excitation power units in a master-slave mode through communication, and the master mode is defaulted to be effective; after receiving the synchronization order, synchronously resetting the analog carrier generator of the flexible excitation power unit to start counting; the actual carrier generators of all the flexible excitation power units approach the simulation carrier generators synchronously to the same time point step by step to be cleared and counted; the flexible synchronization of the actual carrier wave generator is achieved through the synchronization of the simulation carrier wave generator;
when the master mode synchronization command is abnormal, the slave mode synchronization command is switched to the receiving slave mode synchronization command to continue running, and seamless connection of carrier synchronization is guaranteed.
The invention adopts another technical scheme as follows: according to the control method of the parallel topology structure of the flexible excitation power unit, fault ride-through is achieved by adopting a three-level fault-tolerant control strategy, and fault-tolerant operation capability of the flexible excitation power unit is improved.
Further, the three-level fault-tolerant control strategy includes:
when the flexible excitation power unit stops operating due to a fault, an overvoltage protection circuit is adopted as a first-stage protection circuit to control the intermediate direct-current capacitor circuit not to generate overvoltage; secondly, monitoring the voltage of the intermediate direct current capacitor loop, restarting the flexible excitation power unit controller under the condition of ensuring that the intermediate direct current capacitor loop is within a normal operation range, and trying to recover normal operation control; and finally, if the restart recovery control fails or the voltage of the intermediate direct current capacitor loop is abnormal, tripping off the alternating current side circuit breaker and the direct current circuit breaker of the flexible excitation power unit.
The invention has the following beneficial effects: the flexible excitation power unit parallel topology structure can break through the current output bottleneck problem of the flexible excitation system by connecting a plurality of groups of flexible excitation power units in parallel, and realizes the large current output application of the flexible excitation system; meanwhile, by means of measures such as neutral point isolation, a circuit breaker, synchronous carrier control and three-level fault-tolerant control, the circulating current problem among the flexible excitation power units can be effectively restrained, and the fault-tolerant operation capability of the flexible excitation fault is improved.
Drawings
Fig. 1 is a diagram of a parallel topology of a flexible excitation power unit in embodiment 1 of the present invention;
fig. 2 is a topology structure diagram of a flexible excitation power parallel unit including an independent overvoltage protection circuit in embodiment 2 of the present invention;
fig. 3 is a diagram of a parallel topology of a flexible excitation power unit including a shared overvoltage protection circuit in embodiment 3 of the present invention;
fig. 4 is a flowchart of a carrier synchronization control strategy of a parallel topology of flexible excitation power units in embodiment 4 of the present invention.
Fig. 5 is a flowchart of a three-level fault tolerance control strategy of a parallel topology of flexible excitation power units in embodiment 5 of the present invention.
Detailed Description
The invention will be further described with reference to the following examples and the accompanying drawings, but the scope of the invention is not limited to the following examples. Any modification and variation made within the spirit of the present invention and the scope of the claims fall within the scope of the present invention.
Example 1
The parallel topology structure of the flexible excitation power unit proposed by the embodiment is shown in fig. 1, and includes a plurality of groups of flexible excitation power units connected in parallel, each group of flexible excitation power units includes a two-stage circuit including a front-stage bidirectional alternating current-direct current (AC-DC) converter and a rear-stage bidirectional direct current-direct current (DC-DC) converter, and the front-stage AC-DC converter and the rear-stage DC-DC converter are connected through an intermediate DC capacitor loop.
The three-phase alternating current input side of the preceding-stage AC-DC converter is the input side of the flexible excitation power unit; the direct current output side of the rear-stage DC-DC converter is the output side of the flexible excitation power unit; the input sides of the multiple groups of flexible excitation power units are respectively provided with an alternating current side filter reactor and an alternating current breaker which are connected in series, then are connected in parallel and are connected with the three-phase alternating current low-voltage side of the excitation transformer, and the three-phase alternating current high-voltage side of the excitation transformer is connected with the generator end; the output sides of the multiple groups of flexible excitation power units are respectively provided with a direct current side filter reactor and a direct current breaker which are connected in series, then are connected in parallel and are connected with the excitation winding of the generator.
The intermediate direct current capacitor loop comprises two groups of front and rear intermediate direct current capacitor units which are connected in parallel; the intermediate direct current capacitor unit comprises two groups of upper bridge direct current capacitor groups and lower bridge direct current capacitor groups which are mutually connected in series, the positive electrode of each upper bridge direct current capacitor group is the positive electrode of the intermediate direct current capacitor unit, the negative electrode of each upper bridge direct current capacitor group is connected with the positive electrode of each lower bridge direct current capacitor group to form a neutral point of a preceding stage direct current capacitor loop, and the negative electrode of each lower bridge direct current capacitor group is the negative electrode of the intermediate direct current capacitor unit; the front-stage middle direct current capacitor unit and the rear-stage middle direct current capacitor unit are connected only through the positive electrode and the negative electrode.
The front-stage bidirectional AC-DC converter adopts a three-level voltage source type converter; the rear-stage bidirectional DC-DC converter adopts a five-level H-bridge direct current converter; the direct current output side of the three-level voltage source type current converter is connected with the front-stage middle direct current capacitor unit through a positive electrode, a neutral point and a negative electrode; and the direct-current input side of the five-level H-bridge direct-current converter is connected with the rear-stage intermediate direct-current capacitor unit through a positive electrode, a neutral point and a negative electrode.
Example 2
Fig. 2 shows a topology structure diagram of a flexible excitation power parallel unit including an independent overvoltage protection circuit according to the present embodiment. In addition to the parallel topology structure of the flexible excitation power units described in embodiment 1, each group of the flexible excitation power parallel units is independently configured with a corresponding overvoltage protection circuit, which includes an independent overvoltage monitoring and pulse triggering circuit, an independent thyristor circuit, and an independent nonlinear resistor. The thyristor loop consists of a single thyristor, and is connected with the anode and the cathode of the middle direct current capacitor loop after being connected with the nonlinear resistor in series; and the overvoltage monitoring and pulse triggering circuit sends triggering pulses to the silicon controlled loop after monitoring the overvoltage, so that the nonlinear resistor is connected to the positive electrode and the negative electrode of the intermediate direct current capacitor loop to realize overvoltage suppression.
Example 3
Fig. 3 shows a topology structure diagram of a flexible excitation power parallel unit including an independent overvoltage protection circuit according to the present embodiment. In addition to the parallel topology of the flexible excitation power units described in embodiment 1, each group of flexible excitation power units shares the same overvoltage protection circuit, which includes an integrated overvoltage monitoring and pulse triggering circuit, thyristors and non-linear resistors, in a number corresponding to that of each group of flexible excitation power units. The anodes of the thyristors are connected in parallel with the nonlinear resistors, the other poles of the nonlinear resistors are connected with the anodes of the intermediate direct-current capacitor loops of the flexible excitation power units, and the cathodes of the thyristors are connected with the cathodes of the intermediate direct-current capacitor loops of the corresponding flexible excitation power units respectively; the integrated overvoltage monitoring and pulse triggering circuit has the function of monitoring the voltage of the direct current capacitor circuit in the middle of each group of flexible excitation power units, and can send triggering pulses to the thyristors of the corresponding power units, so that the nonlinear resistors can be connected to the positive and negative electrodes of the direct current capacitor circuit in the middle of the corresponding flexible excitation power units to realize overvoltage suppression.
Example 4
The control method of the parallel topology structure of the flexible excitation power unit, which is provided by the embodiment, adopts a two-way redundant and seamless switching carrier synchronization control strategy as shown in fig. 4, and the specific implementation method is as follows: the two flexible excitation regulators respectively issue two synchronous commands to a plurality of groups of parallel flexible excitation power units in a master-slave mode through communication, and the master mode is defaulted to be effective; after receiving the synchronization order, synchronously resetting the analog carrier generator of the flexible excitation power unit to start counting; the actual carrier generators of all the power units approach the simulation carrier generators step by step to the same time point and then are cleared to start counting; the flexible synchronization of the actual carrier wave generator is achieved through the synchronization of the simulation carrier wave generator. When the master mode synchronization command is abnormal, the slave mode synchronization command is switched to the receiving slave mode synchronization command to continue running, and seamless connection of carrier synchronization is guaranteed.
Example 5
The control method of the parallel topology of the flexible excitation power unit according to the embodiment adopts a three-level fault tolerance control strategy as shown in fig. 5. Based on the embodiments 1 and 2, or the embodiments 1 and 3, the implementation method of the three-level fault-tolerant control strategy is as follows: in the first stage, when a certain flexible excitation power unit in parallel operation stops operating due to a fault, an overvoltage protection circuit is used as first-stage protection to control an intermediate direct-current capacitor circuit not to generate overvoltage; the second stage is used for monitoring the voltage of the intermediate direct current capacitor loop and ensuring that the intermediate direct current capacitor loop tries to restart the flexible excitation power unit controller under the condition within the normal operation range so as to recover the normal operation control of the fault flexible excitation power unit; and in the third stage, if the restart recovery control fails or the voltage of the intermediate direct current capacitor loop is abnormal, the alternating current side circuit breaker and the direct current circuit breaker of the flexible excitation power unit are tripped, so that the isolated fault power unit is convenient for online maintenance and repair.
The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the protection scope of the present invention.
Claims (8)
1. A flexible excitation power unit parallel topology structure is characterized by comprising a plurality of groups of flexible excitation power units which are connected in parallel, wherein each group of flexible excitation power units comprises a two-stage circuit of a front-stage bidirectional alternating current-direct current converter and a rear-stage bidirectional direct current-direct current converter, and the front-stage bidirectional alternating current-direct current converter and the rear-stage bidirectional direct current-direct current converter are connected through an intermediate direct current capacitor loop;
the three-phase alternating current input side of the preceding-stage bidirectional alternating current-direct current converter is the input side of the flexible excitation power unit; the direct current output side of the rear-stage bidirectional direct current-direct current converter is the output side of the flexible excitation power unit; the input sides of the multiple groups of flexible excitation power units are respectively provided with an alternating current side filter reactor and an alternating current breaker which are connected in series, then are connected in parallel and are connected with the three-phase alternating current low-voltage side of the excitation transformer, and the three-phase alternating current high-voltage side of the excitation transformer is connected with the generator end; and the output sides of the multiple groups of flexible excitation power units are respectively provided with a direct current side filter reactor and a direct current breaker which are connected in series, then are connected in parallel and are connected with the excitation winding of the generator.
2. The parallel topology of flexible excitation power units as claimed in claim 1, wherein said pre-stage bidirectional ac-dc converter is a three-level voltage source converter; the rear-stage bidirectional DC-DC converter adopts a five-level H-bridge DC converter; the intermediate direct current capacitor loop comprises two groups of front and rear intermediate direct current capacitor units which are connected in parallel;
the direct current output side of the three-level voltage source type current converter is connected with the front-stage middle direct current capacitor unit through a positive electrode, a neutral point and a negative electrode; the direct-current input side of the five-level H-bridge direct-current converter is connected with the rear-stage intermediate direct-current capacitor unit through a positive electrode, a neutral point and a negative electrode;
the middle direct current capacitor unit comprises two groups of upper bridge direct current capacitor groups and lower bridge direct current capacitor groups which are mutually connected in series, the positive electrode of each upper bridge direct current capacitor group is the positive electrode of the middle direct current capacitor unit, the negative electrode of each upper bridge direct current capacitor group is connected with the positive electrode of each lower bridge direct current capacitor group to form a neutral point of the middle direct current capacitor unit, and the negative electrode of each lower bridge direct current capacitor group is the negative electrode of the middle direct current capacitor unit; the front-stage middle direct current capacitor unit and the rear-stage middle direct current capacitor unit are connected only through the positive electrode and the negative electrode.
3. The parallel topology of flexible excitation power units as claimed in claim 1 or 2, wherein said intermediate dc capacitive loop further comprises an overvoltage protection loop for suppressing overvoltage of the intermediate dc capacitive loop in case of system failure.
4. The parallel topology of flexible excitation power units as claimed in claim 3, wherein said overvoltage protection circuit comprises an overvoltage monitoring and pulse triggering circuit, a thyristor circuit and a non-linear resistor; the silicon controlled rectifier circuit is connected with the nonlinear resistor in series and then is connected between the positive electrode and the negative electrode of the intermediate direct current capacitor circuit; and the overvoltage monitoring and pulse triggering circuit sends triggering pulses to the silicon controlled loop after monitoring the overvoltage, and the overvoltage suppression is realized by accessing a nonlinear resistor in the middle direct current capacitor loop.
5. The method for controlling the parallel topology of the flexible excitation power units as claimed in any one of claims 1 to 4, wherein a dual-path redundant and seamless switched carrier flexible synchronous control strategy is adopted to suppress parallel loop currents output by a plurality of groups of flexible excitation power units in parallel.
6. The control method according to claim 5, wherein the carrier-based flexible synchronization control strategy comprises:
the two flexible excitation regulators respectively issue two synchronous commands to a plurality of groups of parallel flexible excitation power units in a master-slave mode through communication, and the master mode is defaulted to be effective; after receiving the synchronization order, synchronously resetting the analog carrier generator of the flexible excitation power unit to start counting; the actual carrier generators of all the flexible excitation power units approach the simulation carrier generators synchronously to the same time point step by step to be cleared and counted; the flexible synchronization of the actual carrier wave generator is achieved through the synchronization of the simulation carrier wave generator;
when the master mode synchronization command is abnormal, the slave mode synchronization command is switched to the receiving slave mode synchronization command to continue running, and seamless connection of carrier synchronization is guaranteed.
7. The method for controlling the parallel topology of the flexible excitation power unit as recited in any one of claims 1 to 4, wherein a three-level fault-tolerant control strategy is adopted to implement fault ride-through.
8. The control method of claim 7, wherein the three-level fault-tolerant control strategy comprises:
when the flexible excitation power unit stops operating due to a fault, an overvoltage protection circuit is adopted as a first-stage protection circuit to control the intermediate direct-current capacitor circuit not to generate overvoltage; secondly, monitoring the voltage of the intermediate direct current capacitor loop, restarting the flexible excitation power unit controller under the condition of ensuring that the intermediate direct current capacitor loop is within a normal operation range, and trying to recover normal operation control; and finally, if the restart recovery control fails or the voltage of the intermediate direct current capacitor loop is abnormal, tripping off the alternating current side circuit breaker and the direct current circuit breaker of the flexible excitation power unit.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010195910.5A CN111277002B (en) | 2020-03-19 | 2020-03-19 | Flexible excitation power unit parallel topology structure and control method thereof |
| PCT/CN2021/078062 WO2021170074A1 (en) | 2020-02-26 | 2021-02-26 | Flexible excitation system and control method therefor |
| US17/896,714 US20220407316A1 (en) | 2020-02-26 | 2022-08-26 | Flexible excitation system and control method therefor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010195910.5A CN111277002B (en) | 2020-03-19 | 2020-03-19 | Flexible excitation power unit parallel topology structure and control method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111277002A true CN111277002A (en) | 2020-06-12 |
| CN111277002B CN111277002B (en) | 2022-03-11 |
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| CN112952784A (en) * | 2021-02-24 | 2021-06-11 | 国网浙江省电力有限公司电力科学研究院 | Excitation becomes overload limiter suitable for flexible excitation system |
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| CN111277002B (en) | 2022-03-11 |
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