WO2021170074A1 - 一种柔性励磁***及其控制方法 - Google Patents

一种柔性励磁***及其控制方法 Download PDF

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Publication number
WO2021170074A1
WO2021170074A1 PCT/CN2021/078062 CN2021078062W WO2021170074A1 WO 2021170074 A1 WO2021170074 A1 WO 2021170074A1 CN 2021078062 W CN2021078062 W CN 2021078062W WO 2021170074 A1 WO2021170074 A1 WO 2021170074A1
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Prior art keywords
excitation
flexible
voltage
transformer
overload
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PCT/CN2021/078062
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English (en)
French (fr)
Inventor
张建承
熊鸿韬
华文
杨滢
楼伯良
吴跨宇
黄晓明
孙维真
陆承宇
Original Assignee
国网浙江省电力有限公司电力科学研究院
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Priority claimed from CN202010119155.2A external-priority patent/CN111277000B/zh
Priority claimed from CN202010195910.5A external-priority patent/CN111277002B/zh
Priority claimed from CN202110210127.6A external-priority patent/CN112952784B/zh
Application filed by 国网浙江省电力有限公司电力科学研究院 filed Critical 国网浙江省电力有限公司电力科学研究院
Publication of WO2021170074A1 publication Critical patent/WO2021170074A1/zh
Priority to US17/896,714 priority Critical patent/US20220407316A1/en

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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
    • 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
    • H02P9/14—Arrangements for controlling electric generators for the purpose of obtaining a desired output by variation of field
    • H02P9/38—Self-excitation by current derived from rectification of both output voltage and output current of generator
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/06—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors
    • H02H7/065—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors against excitation faults
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
    • 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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/007—Plural converter units in cascade
    • 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
    • H02M3/145—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 triode or transistor type requiring continuous application of a control signal
    • H02M3/155—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 triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • 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
    • H02M3/145—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 triode or transistor type requiring continuous application of a control signal
    • H02M3/155—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 triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—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 triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—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 triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • 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
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • 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
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
    • 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
    • H02M7/79—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 triode or transistor type requiring continuous application of a control signal
    • H02M7/81—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 triode or transistor type requiring continuous application of a control signal arranged for operation in parallel
    • 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
    • H02P9/107—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 limiting effects of overloads
    • 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
    • H02P9/14—Arrangements for controlling electric generators for the purpose of obtaining a desired output by variation of field
    • H02P9/26—Arrangements for controlling electric generators for the purpose of obtaining a desired output by variation of field using discharge tubes or semiconductor devices
    • H02P9/30—Arrangements for controlling electric generators for the purpose of obtaining a desired output by variation of field using discharge tubes or semiconductor devices using semiconductor devices
    • H02P9/305—Arrangements for controlling electric generators for the purpose of obtaining a desired output by variation of field using discharge tubes or semiconductor devices using semiconductor devices controlling voltage

Definitions

  • the invention belongs to the field of generator excitation systems, in particular to a flexible excitation system and a control method thereof.
  • the conventional generator excitation system is implemented based on the semi-control device thyristor rectification method. Only the device can be controlled to turn on and cannot be controlled to turn off. As a result, the conventional excitation system can only control the generator excitation voltage through phase-controlled step-down rectification. When it falls, the top value strong excitation output capacity of the generator set is limited, which is not conducive to the voltage stability control of the high-proportion new energy grid.
  • the flexible excitation system uses fully-controlled power electronic devices IGBT, innovative topology and control methods, from the bottom to achieve the essential improvement of the generator excitation system, which involves the performance of the core equipment for grid stability control.
  • the technical problem to be solved by the present invention is to overcome the above-mentioned defects in the prior art and provide a flexible excitation system and its control method to realize the large current output application of the flexible excitation system, exert high-strength excitation multiples, and improve the performance of the flexible excitation system. Fault-tolerant operation capability.
  • the first aspect of the embodiments of the present invention provides a flexible excitation system, including multiple sets of parallel flexible excitation power units, de-excitation loop units, and flexible excitation control units;
  • the flexible excitation power unit includes a front-stage bidirectional AC-DC converter and a rear-stage bidirectional DC-DC converter two-stage circuit, the front-stage bidirectional AC-DC converter and the rear-stage bidirectional DC-DC converter
  • the three-phase AC input side of the front-stage bidirectional AC-DC converter is the input side of the flexible excitation power unit;
  • the DC output side of the back-stage bidirectional 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 each equipped with a series-connected AC-side filter reactor and an AC circuit breaker and then connected in parallel with the three-phase AC low-voltage side of the excitation transformer.
  • the three-phase AC high voltage side of the transformer is connected to the generator end;
  • the output sides of the multiple groups of flexible excitation power units are each configured with a DC side filter reactor and a DC circuit breaker connected in series and then output in parallel;
  • the de-excitation circuit unit is composed of a de-excitation switch and a de-excitation resistance circuit;
  • the de-excitation resistance circuit is composed of a non-linear de-excitation resistance and a diode connected in series, and is connected across the positive and negative ends of the generator excitation winding,
  • the anode of the diode is connected to the negative pole of the excitation winding of the generator, the negative pole of the diode is connected to one end of the nonlinear demagnetization resistor, and the other end of the nonlinear demagnetization resistor is connected to the positive pole of the excitation winding of the generator ;
  • the parallel output positive poles of the multiple sets of flexible excitation power units are connected to the positive pole of the generator excitation winding through the de-excitation switch; the parallel output negative poles of the multiple sets of flexible excitation power units are connected to the negative pole of the generator excitation winding or After connecting the de-excitation switch in series, it is connected to the negative pole of the excitation winding of the generator;
  • the flexible excitation control unit is used to coordinately control the AC circuit breaker and the DC circuit breaker of the flexible excitation power unit and the de-excitation switch, so as to realize the fault-tolerant operation control of the internal fault of the flexible excitation power unit;
  • the flexible excitation control unit is also used to dynamically control the top value voltage by using the fast response control capability of the flexible excitation system to improve the strong excitation output capability of the excitation system when the terminal voltage drops;
  • the flexible excitation control unit is also used to limit the excitation variable operation state within the allowable overload operation range of the equipment.
  • a second aspect of the embodiments of the present invention provides a control method of a flexible excitation system, which is applied to the flexible excitation system described in the first aspect.
  • the flexible excitation control unit includes an excitation variable overload limiter, and the excitation Variable overload limiter includes excitation transformer overload signal detection circuit, excitation transformer overload state judgment circuit and excitation transformer overload action circuit;
  • the flexible excitation control unit limits the operation state of the excitation change to the allowable overload operation range of the equipment, and the specific steps include:
  • the excitation transformer overload signal detection circuit is used to detect the signal of the load operating state of the excitation transformer, and transmit the signal to the excitation transformer overload state judgment circuit;
  • the excitation transformer overload state judgment circuit uses the detected signal to calculate and judge whether the excitation transformer exceeds the allowable overload operation state of the equipment, obtain the excitation transformer overload limit action signal, and transmit the excitation transformer overload limit action signal to Excitation transformer overload action circuit;
  • the excitation transformer overload action circuit receives the excitation transformer overload limit action signal, it limits the operation state of the excitation transformer within the allowable overload operation range of the equipment by controlling the control process variables of the flexible excitation system.
  • the excitation transformer overload signal detection circuit obtains the excitation transformer temperature through a temperature measuring device; the excitation transformer overload state judgment circuit obtains the excitation transformer overload by comparing the temperature of the excitation transformer with the overheat setting value of the excitation transformer Limit the action signal.
  • the excitation transformer overload signal detection circuit obtains the excitation transformer current through a current measuring device; the excitation transformer overload state judgment circuit calculates the accumulated heat of the excitation transformer winding through the excitation transformer current, and the excitation transformer winding is overloaded. The heating value is compared to obtain the excitation transformer overload limit action signal.
  • the excitation transformer overload action loop acts to reduce the current limit of the input link of the front-stage two-way AC-DC converter, which is limited according to the following formula:
  • the stated current limit conservative coefficient of limiting action ⁇ rated current of the secondary side of the excitation transformer.
  • the third aspect of the embodiments of the present invention provides a control method of a flexible excitation system, which is applied to the flexible excitation system described in the first aspect, and the flexible excitation control unit cooperatively controls the AC circuit breaker,
  • the DC circuit breaker and de-excitation switch specifically include the following steps:
  • the flexible excitation control unit When it is detected that any one of the flexible excitation power units is abnormally blocked by the power device pulse, and there are still other branch flexible excitation power units operating normally at this time, the flexible excitation control unit immediately controls to jump off the flexible excitation power unit AC side circuit breaker and DC side circuit breaker;
  • the flexible excitation control unit When it is detected that any one of the flexible excitation power units is abnormally blocked by the power device pulse and there is no other branch flexible excitation power unit operating normally, the flexible excitation control unit immediately controls to jump off the de-excitation switch and the flexible excitation power unit. AC side circuit breaker and DC side circuit breaker of the excitation power unit.
  • the fourth aspect of the embodiments of the present invention provides a control method of a flexible excitation system, which is applied to the flexible excitation system described in the first aspect.
  • the flexible excitation control unit uses the flexible excitation system to respond quickly
  • the control capability dynamically controls the top value voltage, which specifically includes the following steps: the middle DC voltage of the middle DC capacitor circuit is the top value voltage of the flexible excitation system, which is called the middle DC voltage of the flexible excitation system;
  • the intermediate DC voltage of the flexible excitation system is controlled according to the two operating intervals of the generator terminal voltage, which are the regular operating interval where the generator terminal voltage is higher than the regular inflection point voltage, and the generator terminal voltage.
  • Emergency operation interval where the terminal voltage is lower than the conventional inflection point voltage;
  • the intermediate DC voltage of the flexible excitation system adopts an emergency two-stage control strategy to control according to the change of the generator terminal voltage.
  • the conventional two-stage control strategy includes:
  • the regular linear boost interval refers to the range of the generator terminal voltage from zero to the regular inflection point voltage
  • the regular constant voltage interval refers to The terminal voltage of the generator is in the range above the normal inflection point voltage
  • the intermediate DC voltage of the flexible excitation system is controlled by the fixed conventional boost ratio setting value relative to the secondary line voltage of the excitation transformer, that is, the intermediate DC voltage is equal to the secondary line voltage of the excitation transformer multiplied by the conventional boost ratio.
  • the intermediate DC voltage of the flexible excitation system is controlled according to the conventional fixed intermediate DC voltage setting value.
  • the relationship between the conventional inflection point voltage, the conventional step-up ratio, and the conventional fixed intermediate DC voltage is as follows:
  • the emergency two-stage control strategy includes:
  • the emergency linear boost interval refers to the range of the generator terminal voltage from zero to the emergency inflection point voltage
  • the emergency constant voltage interval refers to The range of generator terminal voltage from emergency knee voltage to normal knee voltage
  • the intermediate DC voltage of the flexible excitation system is controlled by a fixed emergency boost ratio set value relative to the excitation transformer secondary line voltage, that is, the intermediate DC voltage is equal to the excitation transformer secondary line voltage multiplied by the emergency boost ratio ;
  • the intermediate DC voltage of the flexible excitation system is controlled according to the fixed emergency DC voltage setting value.
  • the relationship between the emergency inflection point voltage of the generator terminal voltage and the emergency boost ratio setting value and the emergency fixed intermediate DC voltage setting value is as follows:
  • the terminal voltage needs to be restored to the normal operation section and exceeds the set control dead zone before the intermediate DC voltage of the flexible excitation system can be restored to the conventional fixed
  • the DC voltage setting value is controlled.
  • the present invention has the following beneficial effects: 1)
  • the flexible excitation system proposed by the present invention breaks through the current output bottleneck problem of the IGBT device by connecting multiple groups of power units in parallel, and realizes the large current output application of the flexible excitation system.
  • the AC and DC dual-side parallel topology combined with the coordinated control of the circuit breaker and the de-excitation switch, is easy to realize the N-1 redundant fault-tolerant control of the excitation system and improve the reliability of the operation of the device.
  • the dynamic top value voltage control method proposed by the present invention based on the flexible excitation system makes full use of the rapid response control capability of the flexible excitation system, and flexibly adjusts the intermediate DC voltage according to the demand, so as to improve the strength of the self-shunt excitation system when the system voltage fails. Excitation output capability greatly improves the transient stability control capability of the power system.
  • the excitation transformer overload limiter of the flexible excitation system proposed by the present invention can fully utilize the high-strength excitation capacity of the flexible excitation system, and at the same time, improve the shortcomings of the existing excitation limit control, effectively protect the excitation transformer, and ensure the reliability of the overall operation of the flexible excitation system sex.
  • Fig. 1 is a topological structure diagram of a flexible excitation system in a specific embodiment of the present invention
  • Fig. 3 is a control logic block diagram of a flexible excitation system control method in a specific embodiment of the present invention.
  • Fig. 4 is a control effect diagram of a flexible excitation system control method in a specific embodiment of the present invention.
  • the flexible excitation system proposed in this embodiment is shown in FIG. 1, and includes multiple sets of parallel flexible excitation power units, de-excitation circuit units, and flexible excitation control units;
  • the flexible excitation power unit includes a front-stage bidirectional AC-DC converter and a rear-stage bidirectional DC-DC converter two-stage circuit, the front-stage bidirectional AC-DC converter and the rear-stage bidirectional DC-DC converter
  • the three-phase AC input side of the front-stage bidirectional AC-DC converter is the input side of the flexible excitation power unit;
  • the DC output side of the back-stage bidirectional 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 each equipped with a series-connected AC-side filter reactor and an AC circuit breaker and then connected in parallel with the three-phase AC low-voltage side of the excitation transformer.
  • the three-phase AC high voltage side of the transformer is connected to the generator end;
  • the output sides of the multiple groups of flexible excitation power units are each configured with a DC side filter reactor and a DC circuit breaker connected in series and then output in parallel;
  • the de-excitation circuit unit is composed of a de-excitation switch and a de-excitation resistance circuit; the de-excitation resistance circuit is composed of a non-linear de-exc
  • the positive pole is connected to the negative pole of the excitation winding of the generator, the negative pole of the diode is connected to one end of the non-linear de-excitation resistance, and the other end of the non-linear de-excitation resistance is connected to the positive pole of the excitation winding of the generator;
  • the parallel output positive poles of multiple groups of flexible excitation power units are de-excited
  • the switch is connected to the positive pole of the generator excitation winding; the parallel output negative poles of multiple groups of flexible excitation power units can be directly connected to the negative pole of the generator excitation winding, or the de-excitation switch can be connected in series with the negative pole of the generator excitation winding.
  • the flexible excitation control unit is used to coordinately control the AC circuit breaker and the DC circuit breaker of the flexible excitation power unit and the de-excitation switch, so as to realize the fault-tolerant operation control of the internal fault of the flexible excitation power unit;
  • the flexible excitation control unit is also used to dynamically control the top value voltage by using the fast response control capability of the flexible excitation system to improve the strong excitation output capability of the excitation system when the terminal voltage drops;
  • the flexible excitation control unit is also used to limit the excitation variable operation state within the allowable overload operation range of the equipment.
  • the flexible excitation control unit in the flexible excitation system of this embodiment may be a processor, a single-chip microcomputer or other data processing chips.
  • the flexible excitation system proposed in this embodiment breaks through the current output bottleneck problem of the IGBT device by connecting multiple groups of power units in parallel, and realizes the large current output application of the flexible excitation system.
  • the AC and DC dual-side parallel topology combined with the coordinated control of the circuit breaker and the de-excitation switch, is easy to realize the N-1 redundant fault-tolerant control of the excitation system and improve the reliability of the operation of the device.
  • the flexible excitation system control method proposed in this embodiment is applied to the flexible excitation system described in Embodiment 1.
  • the flexible excitation control unit limits the excitation variable operation state within the allowable overload operation range of the equipment, and the specific steps include:
  • the excitation transformer overload signal detection circuit is used to detect the signal of the load operating state of the excitation transformer, and transmit the signal to the excitation transformer overload state judgment circuit;
  • the excitation transformer overload state judgment circuit uses the detected signal to calculate and judge whether the excitation transformer exceeds the allowable overload operation state of the equipment, obtain the excitation transformer overload limit action signal, and transmit the excitation transformer overload limit action signal to Excitation transformer overload action circuit;
  • the excitation transformer overload action circuit receives the excitation transformer overload limit action signal, it limits the operation state of the excitation transformer within the allowable overload operation range of the equipment by controlling the control process variables of the flexible excitation system.
  • the flexible excitation control unit includes an excitation transformer overload limiter, which limits the excitation transformer current within the allowable overload operation range of the equipment.
  • the control block diagram is shown in FIG. 2.
  • the excitation transformer overload limiter is composed of an excitation transformer overload signal detection circuit, an excitation transformer overload state judgment circuit and an excitation transformer overload action circuit;
  • the excitation transformer overload signal detection circuit obtains the excitation transformer current through a current measuring device; the excitation transformer overload state judgment circuit calculates the accumulated heat of the excitation transformer winding through the excitation transformer current, and compares it with the overload heat setting value of the excitation transformer winding. Excitation transformer overload limit action signal.
  • Excitation voltage output limit Conservative coefficient of restricted action ⁇ measured standard unit value of terminal voltage ⁇ rated voltage of secondary side of excitation transformer ⁇ rated current of secondary side of excitation transformer ⁇ measured value of excitation current.
  • the conservative coefficient of restricted action can be set from 0.8 to 0.9.
  • the excitation transformer overload limiter of the flexible excitation system proposed in this embodiment can fully utilize the high-strength excitation capacity of the flexible excitation system, and at the same time, improve the shortcomings of the existing excitation limit control, effectively protect the excitation transformer, and ensure the reliability of the overall operation of the flexible excitation system sex.
  • the flexible excitation control unit limits the excitation variable operation state within the allowable overload operation range of the equipment, and the specific steps include:
  • the excitation transformer overload signal detection circuit is used to detect the signal of the load operating state of the excitation transformer, and transmit the signal to the excitation transformer overload state judgment circuit;
  • the excitation transformer overload state judgment circuit uses the detected signal to calculate and judge whether the excitation transformer exceeds the allowable overload operation state of the equipment, obtain the excitation transformer overload limit action signal, and transmit the excitation transformer overload limit action signal to Excitation transformer overload action circuit;
  • the excitation transformer overload action circuit receives the excitation transformer overload limit action signal, it limits the operation state of the excitation transformer within the allowable overload operation range of the equipment by controlling the control process variables of the flexible excitation system.
  • the overall control block diagram of the excitation transformer overload limiter is the same as that of the second embodiment, as shown in Figure 2.
  • the excitation transformer overload limiter is composed of an excitation transformer overload signal detection circuit, an excitation transformer overload state judgment circuit and an excitation transformer overload action circuit;
  • the excitation transformer overload signal detection circuit obtains the excitation transformer temperature through a temperature measuring device; the excitation transformer overload state judgment circuit obtains the excitation transformer overload limit action signal by comparing the excitation transformer temperature and the temperature overheat setting value of the excitation transformer.
  • the excitation transformer overload limiter of the flexible excitation system proposed in this embodiment can fully utilize the high-strength excitation capacity of the flexible excitation system, and at the same time, improve the shortcomings of the existing excitation limit control, effectively protect the excitation transformer, and ensure the reliability of the overall operation of the flexible excitation system sex.
  • the flexible excitation control unit limits the excitation variable operation state within the allowable overload operation range of the equipment, and the specific steps include:
  • the excitation transformer overload signal detection circuit is used to detect the signal of the load operating state of the excitation transformer, and transmit the signal to the excitation transformer overload state judgment circuit;
  • the excitation transformer overload state judgment circuit uses the detected signal to calculate and judge whether the excitation transformer exceeds the allowable overload operation state of the equipment, obtain the excitation transformer overload limit action signal, and transmit the excitation transformer overload limit action signal to Excitation transformer overload action circuit;
  • the excitation transformer overload action circuit receives the excitation transformer overload limit action signal, it limits the operation state of the excitation transformer within the allowable overload operation range of the equipment by controlling the control process variables of the flexible excitation system.
  • the flexible excitation control unit includes an excitation transformer overload limiter, which limits the excitation transformer current within the allowable overload operation range of the equipment.
  • the control block diagram is shown in FIG. 2.
  • the excitation transformer overload limiter is composed of an excitation transformer overload signal detection circuit, an excitation transformer overload state judgment circuit and an excitation transformer overload action circuit;
  • the excitation transformer overload signal detection circuit obtains the excitation transformer temperature through a temperature measuring device; the excitation transformer overload state judgment circuit obtains the excitation transformer overload limit action signal by comparing the excitation transformer temperature and the temperature overheat setting value of the excitation transformer.
  • Excitation voltage output limit Conservative coefficient of restricted action ⁇ measured standard unit value of terminal voltage ⁇ rated voltage of secondary side of excitation transformer ⁇ rated current of secondary side of excitation transformer ⁇ measured value of excitation current.
  • the conservative coefficient of restricted action can be set from 0.8 to 0.9.
  • the excitation transformer overload limiter of the flexible excitation system proposed in this embodiment can fully utilize the high-strength excitation capacity of the flexible excitation system, and at the same time, improve the shortcomings of the existing excitation limit control, effectively protect the excitation transformer, and ensure the reliability of the overall operation of the flexible excitation system sex.
  • the flexible excitation control unit limits the excitation variable operation state within the allowable overload operation range of the equipment, and the specific steps include:
  • the excitation transformer overload signal detection circuit is used to detect the signal of the load operating state of the excitation transformer, and transmit the signal to the excitation transformer overload state judgment circuit;
  • the excitation transformer overload state judgment circuit uses the detected signal to calculate and judge whether the excitation transformer exceeds the allowable overload operation state of the equipment, obtain the excitation transformer overload limit action signal, and transmit the excitation transformer overload limit action signal to Excitation transformer overload action circuit;
  • the excitation transformer overload action circuit receives the excitation transformer overload limit action signal, it limits the operation state of the excitation transformer within the allowable overload operation range of the equipment by controlling the control process variables of the flexible excitation system.
  • the flexible excitation control unit includes an excitation transformer overload limiter, which controls the excitation transformer current limit within the allowable overload operation range of the equipment.
  • the overall control block diagram of the excitation transformer overload limiter is the same as that of the second embodiment, as shown in Figure 2.
  • the excitation transformer overload limiter is composed of an excitation transformer overload signal detection circuit, an excitation transformer overload state judgment circuit and an excitation transformer overload action circuit;
  • the excitation transformer overload signal detection circuit obtains the excitation transformer current through a current measuring device; the excitation transformer overload state judgment circuit calculates the accumulated heat of the excitation transformer winding through the excitation transformer current, and compares it with the overload heat setting value of the excitation transformer winding. Excitation transformer overload limit action signal.
  • the excitation transformer overload limiter of the flexible excitation system proposed in this embodiment can fully utilize the high-strength excitation capacity of the flexible excitation system, and at the same time, improve the shortcomings of the existing excitation limit control, effectively protect the excitation transformer, and ensure the reliability of the overall operation of the flexible excitation system sex.
  • the flexible excitation system control method proposed in this embodiment is applied to the flexible excitation system described in Embodiment 1.
  • the flexible excitation control unit realizes the fault-tolerant operation control of the internal fault of the flexible excitation power unit by cooperatively controlling the AC circuit breaker, the DC circuit breaker and the de-excitation switch of the flexible excitation power unit, which specifically includes the following steps:
  • the flexible excitation control unit When it is detected that any flexible excitation power unit has abnormally blocked power device pulses, and there are still other branch flexible excitation power units operating normally at this time, the flexible excitation control unit immediately controls to jump off the AC side of the flexible excitation power unit Circuit breaker and DC side circuit breaker;
  • the flexible excitation control unit When it is detected that any flexible excitation power unit is abnormally blocked by the power device pulse, and there is no other branch flexible excitation power unit operating normally, the flexible excitation control unit immediately controls the de-excitation switch and passes the millisecond-level flexible excitation power AC side circuit breaker and DC side circuit breaker of the unit.
  • the flexible excitation system control method proposed in this embodiment is applied to the flexible excitation system described in Embodiment 1.
  • the flexible excitation system control method proposed in this embodiment realizes the dynamic top voltage control of the flexible excitation system by controlling the intermediate DC voltage of the intermediate DC capacitor circuit.
  • the control logic block diagram is shown in Figure 3.
  • the excitation transformer secondary side line voltage The rated value is twice the rated value of the excitation voltage.
  • the intermediate DC voltage of the intermediate DC capacitor circuit is the top voltage of the flexible excitation system, which is called the intermediate DC voltage of the flexible excitation system.
  • the flexible excitation control unit uses the flexible excitation system to quickly respond to the control ability to dynamically control the top value voltage, which may specifically include steps S1 and S2:
  • the regular linear boost interval refers to the range of the generator terminal voltage from zero to the regular inflection point voltage
  • the regular constant voltage interval It refers to the range where the terminal voltage of the generator is above the conventional inflection point voltage.
  • the conventional inflection point voltage is designed to be 0.8pu of the rated value of the terminal voltage.
  • the intermediate DC voltage of the flexible excitation system is controlled according to the set value of the fixed conventional boost ratio relative to the secondary line voltage of the excitation transformer, that is, the intermediate DC voltage is equal to the secondary line voltage of the excitation transformer multiplied by the conventional boost.
  • the conventional boost ratio coefficient is set to 2.5; in the conventional constant voltage interval, the intermediate DC voltage of the flexible excitation system is controlled according to the conventional fixed intermediate DC voltage setting value.
  • the intermediate DC voltage setting value is fixed The value is 4pu of the rated value of the excitation voltage;
  • the intermediate DC voltage control method of the flexible excitation system proposed by the present invention performs voltage control according to the two operating intervals of the generator terminal voltage, including the generator terminal voltage higher than the conventional inflection point voltage. Normal operation interval, emergency operation interval where the generator terminal voltage is lower than the normal inflection point voltage.
  • the intermediate DC voltage of the flexible excitation system adopts an emergency two-stage control strategy for voltage control according to the generator terminal voltage. The details are as follows:
  • the emergency linear boost interval refers to the range of the generator terminal voltage from zero to the emergency inflection point voltage
  • the emergency constant voltage interval It refers to the range of the generator terminal voltage from the emergency knee voltage to the normal knee voltage.
  • the emergency knee voltage is designed to be 0.6 pu of the terminal voltage rating
  • the intermediate DC voltage of the flexible excitation system is controlled by a fixed emergency boost ratio set value relative to the secondary line voltage of the excitation transformer, that is, the intermediate DC voltage is equal to the secondary line voltage of the excitation transformer multiplied by the emergency boost.
  • the emergency boost ratio coefficient is 5.0; in the emergency constant voltage interval, the intermediate DC voltage of the flexible excitation system is controlled according to the fixed emergency DC voltage setting value.
  • the emergency DC voltage setting value is taken The value is 6pu of the rated value of the excitation voltage.
  • the relationship between the emergency inflection point voltage of the generator terminal voltage and the emergency step-up ratio setting value and the emergency fixed intermediate DC voltage setting value is as follows:
  • the terminal voltage needs to be restored to the normal operation section and exceeds the set control dead zone.
  • the control dead zone is set to 0.1 pu, and the intermediate DC voltage of the flexible excitation system It is restored to control according to the conventional fixed DC voltage setting value, and the control effect is shown in the DEF curve in Figure 3.
  • the dynamic top value voltage control method proposed based on the flexible excitation system makes full use of the rapid response control ability of the flexible excitation system, and flexibly adjusts the intermediate DC voltage according to the demand, so as to improve the strong excitation of the self-shunt excitation system when the system voltage fails.
  • the output capability greatly improves the transient stability control capability of the power system.
  • the flexible excitation control unit in the flexible excitation system of the above-mentioned embodiments 2 to 7 may be a control device, which includes a processor and a memory.
  • the flexible excitation control unit includes an excitation transformer
  • the excitation transformer overload limiter includes the excitation transformer overload signal detection circuit, the excitation transformer overload state judgment circuit, and the excitation transformer overload action circuit are all program modules stored in the memory; processing; The device is used to execute the above program modules stored in the memory.

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Abstract

一种柔性励磁***及其控制方法，柔性励磁***由多组并联的柔性励磁功率单元、灭磁回路单元以及柔性励磁控制单元组成，柔性励磁***控制方法包括：通过协同控制柔性励磁功率单元的交流断路器和直流断路器以及灭磁开关，实现柔性励磁功率单元内部故障的容错运行控制；利用柔性励磁***快速响应控制能力，在机端电压跌落时动态控制顶值电压，提升自并励励磁***强励输出能力；针对柔性励磁强励运行时可能出现的励磁变过负荷问题，提出一种柔性励磁***励磁变过负荷限制器，将励磁变运行状态限制在设备允许的过负荷运行范围内。

Description

一种柔性励磁***及其控制方法 技术领域
本发明属于发电机励磁***领域，具体地说是一种柔性励磁***及其控制方法。
背景技术
近年来，随着新能源的大规模发展、能源转型革命的不断深化、以及“3060”碳排放目标的提出，电力***中电源结构和电网结构正经历巨大变革，电网面临高比例清洁能源、高比例电力电子装置的“双高”发展挑战，安全稳定运行压力大增，新形势下电力***应对极端风险的弹性调节能力亟待提升。在常规发电机组被新能源大量替代后，电网稳定支撑能力下降，电网运行风险增加、控制手段匮乏。上述问题的解决，若在一次***采取措施成本高，难度大，如能通过改进大型同步发电机励磁控制***及其控制策略实现，效果将会更加显著，同时成本也大幅度降低。
目前，常规发电机励磁***是基于半控器件晶闸管整流的方式实现，仅可以控制器件开通无法控制关断，导致常规励磁***仅可通过相控降压整流来控制发电机励磁电压，当电网电压跌落时，发电机组的顶值强励输出能力有限，不利于高比例新能源电网的电压稳定控制。柔性励磁***通过应用全控电力电子器件IGBT，创新拓扑结构和控制方法，从底层实现对发电机励磁***这一涉及电网稳定控制核心设备性能的本质提升。
但基于IGBT元件的AC-DC和DC-DC功率变换回路组成的柔性励磁***应用于发电励磁***时，存在单功率装置电流输出能力弱、强励电压控制算法不完善、可靠性控制算法不完善等缺点，已有技术尚不满足发电机及励磁***高性能和高可靠性的运行要求。
发明内容
本发明所要解决的技术问题是克服上述现有技术存在的缺陷，提供一种柔性励磁***及其控制方法，以实现柔性励磁***的大电流输出应用，发挥高强励倍数，同时提升柔性励磁***的故障容错运行能力。
为达到上述目的，本发明采用的技术方案如下：
本发明实施例的第一方面提供了一种柔性励磁***，包括多组并联的柔性励磁功率单元、灭磁回路单元以及柔性励磁控制单元；
所述柔性励磁功率单元包含一个前级双向交流-直流换流器和一个后级双向直流-直流换流器两级电路，前级双向交流-直流换流器与后级双向直流-直流换流器经中间直流电 容回路相连；所述前级双向交流-直流换流器的三相交流输入侧为柔性励磁功率单元的输入侧；所述后级双向直流-直流换流器的直流输出侧为柔性励磁功率单元的输出侧；所述多组柔性励磁功率单元的输入侧各自均配置串联的交流侧滤波电抗器和交流断路器后再并联，并与励磁变压器的三相交流低压侧相连，励磁变压器的三相交流高压侧与发电机机端相连；所述多组柔性励磁功率单元的输出侧各自均配置串联的直流侧滤波电抗器和直流断路器后再并联输出；
所述灭磁回路单元由灭磁开关和灭磁电阻回路组成；灭磁电阻回路由非线性灭磁电阻和串联的二极管构成，并跨接在所述发电机励磁绕组的正负极两端，所述二极管的正极与所述发电机励磁绕组负极相连，所述二极管负极与所述非线性灭磁电阻的一端相连，所述非线性灭磁电阻的另一端与所述发电机励磁绕组正极相连；
所述多组柔性励磁功率单元的并联输出正极经过所述灭磁开关与所述发电机励磁绕组正极相连；所述多组柔性励磁功率单元的并联输出负极与所述发电机励磁绕组负极相连或串联所述灭磁开关后再与所述发电机励磁绕组负极相连；
所述柔性励磁控制单元，用于协同控制柔性励磁功率单元的交流断路器和直流断路器以及所述灭磁开关，实现柔性励磁功率单元内部故障的容错运行控制；
所述柔性励磁控制单元，还用于在机端电压跌落时，利用柔性励磁***快速响应控制能力动态控制顶值电压，提升励磁***强励输出能力；
所述柔性励磁控制单元，还用于将励磁变运行状态限制在设备允许的过负荷运行范围内。
本发明实施例的第二方面提供了一种柔性励磁***的控制方法，应用于第一方面所述的柔性励磁***，所述柔性励磁控制单元包含励磁变过负荷限制器，该所述的励磁变过负荷限制器包括励磁变过负荷信号检测回路、励磁变过负荷状态判断回路和励磁变过负荷动作回路；
所述柔性励磁控制单元将励磁变运行状态限制在设备允许的过负荷运行范围内，具体步骤包括：
所述励磁变过负荷信号检测回路用于检测励磁变压器负荷运行状态的信号，并将信号传送给励磁变过负荷状态判断回路；
所述励磁变过负荷状态判断回路利用检测得到的信号对励磁变是否超过设备允许的过负荷运行状态进行计算判断，得到励磁变过负荷限制动作信号，并将励磁变过负荷限制动作信号传送给励磁变过负荷动作回路；
所述励磁变过负荷动作回路在收到励磁变过负荷限制动作信号后，通过控制柔性励磁***的控制过程变量，将励磁变压器运行状态限制在设备允许的过负荷运行范围内。
在一个实施示例中，所述励磁变过负荷信号检测回路通过温度测量装置得到励磁变压器温度；所述励磁变过负荷状态判断回路通过比较励磁变压器温度和励磁变压器温度过热定值得到励磁变过负荷限制动作信号。
在一个实施示例中，所述励磁变过负荷信号检测回路通过电流测量装置获得励磁变压器电流；所述励磁变过负荷状态判断回路通过励磁变压器电流计算励磁变绕组积累热量，与励磁变绕组过负荷热量定值比较得到励磁变过负荷限制动作信号。
在一个实施示例中，当励磁变过负荷限制动作信号发生时，励磁变过负荷动作回路动作于减小后级双向直流-直流换流器的励磁电压输出限幅，并按如下公式实时调整：所述的励磁电压输出限幅＝限制动作保守系数×机端电压实测标幺值×励磁变二次侧额定电压×励磁变二次侧额定电流÷励磁电流实测值。
在一个实施示例中，当励磁变过负荷限制动作信号发生时，励磁变过负荷动作回路动作于减小前级双向交流-直流换流器输入环节的电流限幅，按如下公式进行限制：所述的电流限幅＝限制动作保守系数×励磁变二次侧额定电流。
本发明实施例的第三方面提供了一种柔性励磁***的控制方法，应用于第一方面所述的柔性励磁***，所述柔性励磁控制单元协同控制所述柔性励磁功率单元的交流断路器、直流断路器和灭磁开关，具体包括以下步骤：
当检测到任一所述柔性励磁功率单元发生功率器件脉冲异常闭锁，且此时仍有其它支路柔性励磁功率单元正常运行时，所述柔性励磁控制单元立即控制跳开所述柔性励磁功率单元的交流侧断路器和直流侧断路器；
当检测到任一所述柔性励磁功率单元发生功率器件脉冲异常闭锁，且没有其它支路柔性励磁功率单元正常运行时，所述柔性励磁控制单元立即控制跳开所述灭磁开关、所述柔性励磁功率单元的交流侧断路器和直流侧断路器。
本发明实施例的第四方面提供了一种柔性励磁***的控制方法，应用于第一方面所述的柔性励磁***，在机端电压跌落时，所述柔性励磁控制单元利用柔性励磁***快速响应控制能力动态控制顶值电压，具体包括以下步骤：中间直流电容回路的中间直流电压为柔性励磁***的顶值电压，称为柔性励磁***中间直流电压；
S1，在同步发电机空载起励到并网过程，或者并网解列后的逆变灭磁过程，或者任意工况下同步发电机收到跳灭磁开关令后的灭磁过程，柔性励磁***中间直流电压根据机端 电压的变化采取常规两段式控制策略进行控制；
S2，在同步发电机并网后，柔性励磁***中间直流电压按发电机机端电压的两种运行区间进行控制，分别是发电机机端电压高于常规拐点电压的常规运行区间、发电机机端电压低于常规拐点电压的紧急运行区间；
A1)当发电机机端电压在常规运行区间时，柔性励磁***中间直流电压按常规固定直流电压设定值进行控制；
A2)当发电机机端电压在紧急运行区间时，柔性励磁***中间直流电压根据机端电压的变化采取紧急两段式控制策略进行控制。
在一个实施示例中，所述常规两段式控制策略，其具体内容包括：
根据机端电压的不同分为常规线性升压区间和常规恒定电压区间：所述常规线性升压区间是指发电机机端电压从零到常规拐点电压的范围，所述常规恒定电压区间是指发电机机端电压在常规拐点电压以上的范围；
在常规线性升压区间，柔性励磁***中间直流电压相对励磁变二次线电压按固定的常规升压比设定值进行控制，即中间直流电压等于励磁变二次线电压乘以常规升压比；在常规恒定电压区间，柔性励磁***中间直流电压按常规固定中间直流电压设定值进行控制。
在一个实施示例中，所述的常规拐点电压与常规升压比以及常规固定中间直流电压的关系如下：
Figure PCTCN2021078062-appb-000001
在一个实施示例中，所述紧急两段式控制策略，其具体内容包括：
根据机端电压的不同分为紧急线性升压区间和紧急恒定电压区间：所述紧急线性升压区间是指发电机机端电压从零到紧急拐点电压的范围，所述紧急恒定电压区间是指发电机机端电压从紧急拐点电压到正常拐点电压的范围；
在紧急线性升压区间，柔性励磁***中间直流电压相对励磁变二次线电压按固定的紧急升压比设定值进行控制，即中间直流电压等于励磁变二次线电压乘以紧急升压比；在紧急恒定电压区间，柔性励磁***中间直流电压按固定的紧急直流电压设定值进行控制。
在一个实施示例中，所述的发电机机端电压的紧急拐点电压与紧急升压比设定值以及紧急固定中间直流电压设定值的关系如下：
Figure PCTCN2021078062-appb-000002
在一个实施示例中，当发电机在并网状态进入紧急运行区间后，机端电压需恢复至常 规运行区间内且超过设定的控制死区，柔性励磁***中间直流电压才能恢复为按常规固定直流电压设定值进行控制。
本发明具有以下有益效果：1)本发明提出的柔性励磁***通过并联多组功率单元，突破IGBT装置的电流输出瓶颈问题，实现柔性励磁***的大电流输出应用。同时，采用交直流双侧并联的拓扑，结合断路器和灭磁开关的协调控制，易于实现励磁***的N-1冗余容错控制，提升装置运行可靠性。2)本发明基于柔性励磁***提出的动态顶值电压控制方法充分利用柔性励磁***快速响应控制能力，根据需求灵活调整中间直流电压，以提升了自并励励磁***在***电压故障跌落时的强励输出能力，大幅提升电力***的暂态稳定控制能力。3)本发明提出的柔性励磁***励磁变过负荷限制器能在充分发挥柔性励磁***高强励能力的同时，完善现有励磁限制控制的不足，有效保护励磁变，保证柔性励磁***整体运行的可靠性。
附图说明
图1是本发明具体实施方式中柔性励磁***的拓扑结构图；
图2为本发明具体实施方式中柔性励磁***的励磁变过负荷限制器的控制框图；
图3是本发明具体实施方式中柔性励磁***控制方法的控制逻辑框图；
图4为本发明具体实施方式中柔性励磁***控制方法的控制效果图。
具体实施方式
下面结合实施例和说明书附图来对本发明进行进一步说明，但本发明的保护范围不限于下述实施例。在本发明的精神和权利要求的保护范围内，对本发明作出的任何修改和变更，都落入本发明的保护范围。
实施例1
本实施方式所提出的柔性励磁***如图1所示，包括多组并联的柔性励磁功率单元、灭磁回路单元以及柔性励磁控制单元；
所述柔性励磁功率单元包含一个前级双向交流-直流换流器和一个后级双向直流-直流换流器两级电路，前级双向交流-直流换流器与后级双向直流-直流换流器经中间直流电容回路相连；所述前级双向交流-直流换流器的三相交流输入侧为柔性励磁功率单元的输入侧；所述后级双向直流-直流换流器的直流输出侧为柔性励磁功率单元的输出侧；所述多组柔性励磁功率单元的输入侧各自均配置串联的交流侧滤波电抗器和交流断路器后再并联，并与励磁变压器的三相交流低压侧相连，励磁变压器的三相交流高压侧与发电机机 端相连；所述多组柔性励磁功率单元的输出侧各自均配置串联的直流侧滤波电抗器和直流断路器后再并联输出；
所述灭磁回路单元由灭磁开关和灭磁电阻回路组成；灭磁电阻回路由非线性灭磁电阻和串联的二极管构成，并跨接在发电机励磁绕组的正负极两端，二极管的正极与发电机励磁绕组负极相连，二极管负极与非线性灭磁电阻的一端相连，非线性灭磁电阻的另一端与发电机励磁绕组正极相连；多组柔性励磁功率单元的并联输出正极经过灭磁开关与发电机励磁绕组正极相连；多组柔性励磁功率单元的并联输出负极可直接与发电机励磁绕组负极相连，也可串联灭磁开关再与发电机励磁绕组负极相连。
所述柔性励磁控制单元，用于协同控制柔性励磁功率单元的交流断路器和直流断路器以及所述灭磁开关，实现柔性励磁功率单元内部故障的容错运行控制；
所述柔性励磁控制单元，还用于在机端电压跌落时，利用柔性励磁***快速响应控制能力动态控制顶值电压，提升励磁***强励输出能力；
所述柔性励磁控制单元，还用于将励磁变运行状态限制在设备允许的过负荷运行范围内。
在另一种优选的实施例中，本实施例的柔性励磁***中的柔性励磁控制单元可为处理器、单片机或其它数据处理芯片。
本实施例提出的柔性励磁***通过并联多组功率单元，突破IGBT装置的电流输出瓶颈问题，实现柔性励磁***的大电流输出应用。同时，采用交直流双侧并联的拓扑，结合断路器和灭磁开关的协调控制，易于实现励磁***的N-1冗余容错控制，提升装置运行可靠性。
实施例2
本实施方式所提出的一种柔性励磁***控制方法，应用于实施例1中所述的柔性励磁***。
本实施方式所提出的柔性励磁***控制方法，所述柔性励磁控制单元将励磁变运行状态限制在设备允许的过负荷运行范围内，具体步骤包括：
所述励磁变过负荷信号检测回路用于检测励磁变压器负荷运行状态的信号，并将信号传送给励磁变过负荷状态判断回路；
所述励磁变过负荷状态判断回路利用检测得到的信号对励磁变是否超过设备允许的过负荷运行状态进行计算判断，得到励磁变过负荷限制动作信号，并将励磁变过负荷限制动作信号传送给励磁变过负荷动作回路；
所述励磁变过负荷动作回路在收到励磁变过负荷限制动作信号后，通过控制柔性励磁***的控制过程变量，将励磁变压器运行状态限制在设备允许的过负荷运行范围内。
所述柔性励磁控制单元包含励磁变过负荷限制器，将励磁变电流限制控制在设备允许的过负荷运行范围内，控制框图如图2所示。
所述的励磁变过负荷限制器由励磁变过负荷信号检测回路、励磁变过负荷状态判断回路和励磁变过负荷动作回路构成；
所述励磁变过负荷信号检测回路通过电流测量装置获得励磁变压器电流；所述励磁变过负荷状态判断回路再通过励磁变压器电流计算励磁变绕组积累热量，与励磁变绕组过负荷热量定值比较得到励磁变过负荷限制动作信号。
当励磁变过负荷限制动作信号发生时，励磁变过负荷动作回路动作于减小后级双向直流-直流换流器的励磁电压输出限幅，并按如下公式实时调整：励磁电压输出限幅＝限制动作保守系数×机端电压实测标幺值×励磁变二次侧额定电压×励磁变二次侧额定电流÷励磁电流实测值，其中限制动作保守系数可按0.8至0.9整定。
本实施例提出的柔性励磁***的励磁变过负荷限制器能在充分发挥柔性励磁***高强励能力的同时，完善现有励磁限制控制的不足，有效保护励磁变，保证柔性励磁***整体运行的可靠性。
实施例3
实施方式所提出的一种柔性励磁***控制方法，应用于实施例1中所述的柔性励磁***。
本实施方式所提出的柔性励磁***控制方法，所述柔性励磁控制单元将励磁变运行状态限制在设备允许的过负荷运行范围内，具体步骤包括：
所述励磁变过负荷信号检测回路用于检测励磁变压器负荷运行状态的信号，并将信号传送给励磁变过负荷状态判断回路；
所述励磁变过负荷状态判断回路利用检测得到的信号对励磁变是否超过设备允许的过负荷运行状态进行计算判断，得到励磁变过负荷限制动作信号，并将励磁变过负荷限制动作信号传送给励磁变过负荷动作回路；
所述励磁变过负荷动作回路在收到励磁变过负荷限制动作信号后，通过控制柔性励磁***的控制过程变量，将励磁变压器运行状态限制在设备允许的过负荷运行范围内。
励磁变过负荷限制器总体控制框图与实施例2相同，如图2所示。所述的励磁变过负荷限制器由励磁变过负荷信号检测回路、励磁变过负荷状态判断回路和励磁变过负荷动作 回路构成；
所述励磁变过负荷信号检测回路通过温度测量装置得到励磁变压器温度；所述励磁变过负荷状态判断回路通过比较励磁变压器温度和励磁变压器温度过热定值得到励磁变过负荷限制动作信号。
当励磁变过负荷限制动作信号发生时，励磁变过负荷动作回路也可动作于减小前级双向交流-直流换流器输入环节的电流限幅，按如下公式进行限制：三相交流输入电流限幅＝限制动作保守系数×励磁变二次侧额定电流，其中限制动作保守系数可按0.8至0.9整定。
本实施例提出的柔性励磁***的励磁变过负荷限制器能在充分发挥柔性励磁***高强励能力的同时，完善现有励磁限制控制的不足，有效保护励磁变，保证柔性励磁***整体运行的可靠性。
实施例4
实施方式所提出的一种柔性励磁***控制方法，应用于实施例1中所述的柔性励磁***。
本实施方式所提出的柔性励磁***控制方法，所述柔性励磁控制单元将励磁变运行状态限制在设备允许的过负荷运行范围内，具体步骤包括：
所述励磁变过负荷信号检测回路用于检测励磁变压器负荷运行状态的信号，并将信号传送给励磁变过负荷状态判断回路；
所述励磁变过负荷状态判断回路利用检测得到的信号对励磁变是否超过设备允许的过负荷运行状态进行计算判断，得到励磁变过负荷限制动作信号，并将励磁变过负荷限制动作信号传送给励磁变过负荷动作回路；
所述励磁变过负荷动作回路在收到励磁变过负荷限制动作信号后，通过控制柔性励磁***的控制过程变量，将励磁变压器运行状态限制在设备允许的过负荷运行范围内。
所述柔性励磁控制单元包含励磁变过负荷限制器，将励磁变电流限制控制在设备允许的过负荷运行范围内，控制框图如图2所示。
所述的励磁变过负荷限制器由励磁变过负荷信号检测回路、励磁变过负荷状态判断回路和励磁变过负荷动作回路构成；
所述励磁变过负荷信号检测回路通过温度测量装置得到励磁变压器温度；所述励磁变过负荷状态判断回路通过比较励磁变压器温度和励磁变压器温度过热定值得到励磁变过负荷限制动作信号。
当励磁变过负荷限制动作信号发生时，励磁变过负荷动作回路动作于减小后级双向直 流-直流换流器的励磁电压输出限幅，并按如下公式实时调整：励磁电压输出限幅＝限制动作保守系数×机端电压实测标幺值×励磁变二次侧额定电压×励磁变二次侧额定电流÷励磁电流实测值，其中限制动作保守系数可按0.8至0.9整定。
本实施例提出的柔性励磁***的励磁变过负荷限制器能在充分发挥柔性励磁***高强励能力的同时，完善现有励磁限制控制的不足，有效保护励磁变，保证柔性励磁***整体运行的可靠性。
实施例5
实施方式所提出的一种柔性励磁***控制方法，应用于实施例1中所述的柔性励磁***。
本实施方式所提出的柔性励磁***控制方法，所述柔性励磁控制单元将励磁变运行状态限制在设备允许的过负荷运行范围内，具体步骤包括：
所述励磁变过负荷信号检测回路用于检测励磁变压器负荷运行状态的信号，并将信号传送给励磁变过负荷状态判断回路；
所述励磁变过负荷状态判断回路利用检测得到的信号对励磁变是否超过设备允许的过负荷运行状态进行计算判断，得到励磁变过负荷限制动作信号，并将励磁变过负荷限制动作信号传送给励磁变过负荷动作回路；
所述励磁变过负荷动作回路在收到励磁变过负荷限制动作信号后，通过控制柔性励磁***的控制过程变量，将励磁变压器运行状态限制在设备允许的过负荷运行范围内。
所述柔性励磁控制单元包含励磁变过负荷限制器，将励磁变电流限制控制在设备允许的过负荷运行范围内。励磁变过负荷限制器总体控制框图与实施例2相同，如图2所示。所述的励磁变过负荷限制器由励磁变过负荷信号检测回路、励磁变过负荷状态判断回路和励磁变过负荷动作回路构成；
所述励磁变过负荷信号检测回路通过电流测量装置获得励磁变压器电流；所述励磁变过负荷状态判断回路再通过励磁变压器电流计算励磁变绕组积累热量，与励磁变绕组过负荷热量定值比较得到励磁变过负荷限制动作信号。
当励磁变过负荷限制动作信号发生时，励磁变过负荷动作回路也可动作于减小前级双向交流-直流换流器输入环节的电流限幅，按如下公式进行限制：三相交流输入电流限幅＝限制动作保守系数×励磁变二次侧额定电流，其中限制动作保守系数可按0.8至0.9整定。
本实施例提出的柔性励磁***的励磁变过负荷限制器能在充分发挥柔性励磁***高强励能力的同时，完善现有励磁限制控制的不足，有效保护励磁变，保证柔性励磁***整 体运行的可靠性。
实施例6
本实施方式所提出的一种柔性励磁***控制方法，应用于实施例1中所述的柔性励磁***。
柔性励磁控制单元通过协同控制柔性励磁功率单元的交流断路器、直流断路器和灭磁开关，实现柔性励磁功率单元内部故障的容错运行控制，具体包括以下步骤：
1)当检测到任一柔性励磁功率单元发生功率器件脉冲异常闭锁，且此时仍有其它支路柔性励磁功率单元正常运行时，柔性励磁控制单元立即控制跳开该柔性励磁功率单元的交流侧断路器和直流侧断路器；
2)当检测到任一柔性励磁功率单元发生功率器件脉冲异常闭锁，且没有其它支路柔性励磁功率单元正常运行时，柔性励磁控制单元立即控制跳开灭磁开关，并经毫秒级柔性励磁功率单元的交流侧断路器和直流侧断路器。
实施例7
本实施方式所提出的一种柔性励磁***控制方法，应用于实施例1中所述的柔性励磁***。
本实施方式所提出的柔性励磁***控制方法通过控制中间直流电容回路的中间直流电压，实现柔性励磁***动态顶值电压控制，控制逻辑框图如图3所示，本例中励磁变二次侧线电压额定值为励磁电压额定值的2倍。中间直流电容回路的中间直流电压为柔性励磁***的顶值电压，称为柔性励磁***中间直流电压。
柔性励磁控制单元利用柔性励磁***快速响应控制能力动态控制顶值电压，具体可包括步骤S1和步骤S2：
S1，针对同步发电机空载起励到并网过程，或者并网解列后的逆变灭磁过程，或者任意工况下同步发电机收到跳灭磁开关令后的灭磁过程，本发明提出的柔性励磁***中间直流电压控制方法将根据机端电压的不同采取常规两段式控制策略进行电压控制，具体内容如下：
首先，根据机端电压的不同分为常规线性升压区间和常规恒定电压区间：所述常规线性升压区间是指发电机机端电压从零到常规拐点电压的范围，所述常规恒定电压区间是指发电机机端电压在常规拐点电压以上的范围，本例中常规拐点电压设计为机端电压额定值的0.8pu。
其次，在常规线性升压区间，柔性励磁***中间直流电压相对励磁变二次线电压按固 定的常规升压比设定值进行控制，即中间直流电压等于励磁变二次线电压乘以常规升压比，本例中常规升压比系数取值为2.5；在常规恒定电压区间，柔性励磁***中间直流电压按常规固定中间直流电压设定值进行控制，本例中固定中间直流电压设定值取值为励磁电压额定值的4pu；
其中，所述的常规拐点电压与常规升压比以及常规固定中间直流电压的关系如下：
Figure PCTCN2021078062-appb-000003
即：0.8pu×2pu(励磁电压额定值)×2.5＝4pu(励磁电压额定值)。
该部分的控制效果如图4中OAB曲线所示。
S2，针对同步发电机并网后，本发明提出的柔性励磁***中间直流电压控制方法分别按发电机机端电压的二种运行区间进行电压控制，包括发电机机端电压高于常规拐点电压的常规运行区间、发电机机端电压低于常规拐点电压的紧急运行区间。
1)当发电机机端电压在常规运行区间时，柔性励磁***中间直流电压按常规固定直流电压设定值进行控制，控制效果如图3中AFB曲线所示。
2)当发电机机端电压在紧急运行区间时，柔性励磁***中间直流电压根据机端电压的不同采取紧急两段式控制策略进行电压控制，具体如下：
首先，根据机端电压的不同分为紧急线性升压区间和紧急恒定电压区间：所述紧急线性升压区间是指发电机机端电压从零到紧急拐点电压的范围，所述紧急恒定电压区间是指发电机机端电压从紧急拐点电压到正常拐点电压的范围，本例中紧急拐点电压设计为机端电压额定值的0.6pu；
其次，在紧急线性升压区间，柔性励磁***中间直流电压相对励磁变二次线电压按固定的紧急升压比设定值进行控制，即中间直流电压等于励磁变二次线电压乘以紧急升压比，本例中紧急升压比系数取值为5.0；在紧急恒定电压区间，柔性励磁***中间直流电压按固定的紧急直流电压设定值进行控制，本例中紧急直流电压设定值取值为励磁电压额定值的6pu。
其中，所述的发电机机端电压的紧急拐点电压与紧急升压比设定值以及紧急固定中间直流电压设定值的关系如下：
Figure PCTCN2021078062-appb-000004
即：0.6pu×2pu(励磁电压额定值)×5.0＝6pu(励磁电压额定值)，
该部分控制效果如图4中ADCO曲线所示。
当发电机在并网状态进入紧急运行区间后，机端电压需恢复至常规运行区间内且超过设定的控制死区，本例中控制死区设置为0.1pu，柔性励磁***中间直流电压才能恢复为按常规固定直流电压设定值进行控制，控制效果如图3中DEF曲线所示。
本实施例基于柔性励磁***提出的动态顶值电压控制方法充分利用柔性励磁***快速响应控制能力，根据需求灵活调整中间直流电压，以提升了自并励励磁***在***电压故障跌落时的强励输出能力，大幅提升电力***的暂态稳定控制能力。
在另一种优选的实施例中，上述实施例2至7的柔性励磁***中的柔性励磁控制单元可为控制装置，该控制装置包括处理器，以及存储器，当柔性励磁控制单元包含励磁变过负荷限制器时，该所述的励磁变过负荷限制器包括的励磁变过负荷信号检测回路、励磁变过负荷状态判断回路和励磁变过负荷动作回路均为存储在存储器中的程序模块；处理器用于执行存储在存储器中的以上程序模块。

Claims (13)

  1. 一种柔性励磁***，其特征在于，包括多组并联的柔性励磁功率单元、灭磁回路单元以及柔性励磁控制单元；
    所述柔性励磁功率单元包含一个前级双向交流-直流换流器和一个后级双向直流-直流换流器两级电路，前级双向交流-直流换流器与后级双向直流-直流换流器经中间直流电容回路相连；所述前级双向交流-直流换流器的三相交流输入侧为柔性励磁功率单元的输入侧；所述后级双向直流-直流换流器的直流输出侧为柔性励磁功率单元的输出侧；所述多组柔性励磁功率单元的输入侧各自均配置串联的交流侧滤波电抗器和交流断路器后再并联，并与励磁变压器的三相交流低压侧相连，励磁变压器的三相交流高压侧与发电机机端相连；所述多组柔性励磁功率单元的输出侧各自均配置串联的直流侧滤波电抗器和直流断路器后再并联输出；
    所述灭磁回路单元由灭磁开关和灭磁电阻回路组成；灭磁电阻回路由非线性灭磁电阻和串联的二极管构成，并跨接在所述发电机励磁绕组的正负极两端，所述二极管的正极与所述发电机励磁绕组负极相连，所述二极管负极与所述非线性灭磁电阻的一端相连，所述非线性灭磁电阻的另一端与所述发电机励磁绕组正极相连；
    所述多组柔性励磁功率单元的并联输出正极经过所述灭磁开关与所述发电机励磁绕组正极相连；所述多组柔性励磁功率单元的并联输出负极与所述发电机励磁绕组负极相连或串联所述灭磁开关后再与所述发电机励磁绕组负极相连；
    所述柔性励磁控制单元，用于协同控制所述柔性励磁功率单元的交流断路器和直流断路器以及所述灭磁开关，实现柔性励磁功率单元内部故障的容错运行控制；
    所述柔性励磁控制单元，还用于在机端电压跌落时，利用柔性励磁***快速响应控制能力动态控制顶值电压，提升励磁***强励输出能力；
    所述柔性励磁控制单元，还用于将励磁变运行状态限制在设备允许的过负荷运行范围内。
  2. 一种柔性励磁***的控制方法，其特征在于，应用于如权利要求1所述的柔性励磁***，所述柔性励磁控制单元包含励磁变过负荷限制器，所述励磁变过负荷限制器包括励磁变过负荷信号检测回路、励磁变过负荷状态判断回路和励磁变过负荷动作回路；
    所述柔性励磁控制单元将励磁变运行状态限制在设备允许的过负荷运行范围内，具体步骤包括：
    所述励磁变过负荷信号检测回路用于检测励磁变压器负荷运行状态的信号，并将信号传送给励磁变过负荷状态判断回路；
    所述励磁变过负荷状态判断回路利用检测得到的信号对励磁变是否超过设备允许的过负荷运行状态进行计算判断，得到励磁变过负荷限制动作信号，并将励磁变过负荷限制动作信号传送给励磁变过负荷动作回路；
    所述励磁变过负荷动作回路在收到励磁变过负荷限制动作信号后，通过控制柔性励磁***的控制过程变量，将励磁变压器运行状态限制在设备允许的过负荷运行范围内。
  3. 如权利要求2所述的柔性励磁***的控制方法，其特征在于，所述励磁变过负荷信号检测回路通过温度测量装置得到励磁变压器温度；所述励磁变过负荷状态判断回路通过比较励磁变压器温度和励磁变压器温度过热定值得到励磁变过负荷限制动作信号。
  4. 如权利要求2所述的柔性励磁***的控制方法，其特征在于，所述励磁变过负荷信号检测回路通过电流测量装置获得励磁变压器电流；所述励磁变过负荷状态判断回路通过励磁变压器电流计算励磁变绕组积累热量，与励磁变绕组过负荷热量定值比较得到励磁变过负荷限制动作信号。
  5. 如权利要求2至4任一项所述的柔性励磁***的控制方法，其特征在于，当励磁变过负荷限制动作信号发生时，励磁变过负荷动作回路动作于减小后级双向直流-直流换流器的励磁电压输出限幅，并按如下公式实时调整：所述的励磁电压输出限幅＝限制动作保守系数×机端电压实测标幺值×励磁变二次侧额定电压×励磁变二次侧额定电流÷励磁电流实测值。
  6. 如权利要求2至4任一项所述的柔性励磁***的控制方法，其特征在于，当励磁变过负荷限制动作信号发生时，励磁变过负荷动作回路动作于减小前级双向交流-直流换流器输入环节的电流限幅，并按如下公式进行限制：所述的电流限幅＝限制动作保守系数×励磁变二次侧额定电流。
  7. 一种柔性励磁***的控制方法，其特征在于，应用于如权利要求1所述的柔性励磁***，所述柔性励磁控制单元协同控制所述柔性励磁功率单元的交流断路器、直流断路器和所述灭磁开关，具体包括以下步骤：
    当检测到任一所述柔性励磁功率单元发生功率器件脉冲异常闭锁，且此时仍有其它支路柔性励磁功率单元正常运行时，所述柔性励磁控制单元立即控制跳开所述柔性励磁功率单元的交流侧断路器和直流侧断路器；
    当检测到任一所述柔性励磁功率单元发生功率器件脉冲异常闭锁，且没有其它支路柔 性励磁功率单元正常运行时，所述柔性励磁控制单元立即控制跳开所述灭磁开关、所述柔性励磁功率单元的交流侧断路器和直流侧断路器。
  8. 一种柔性励磁***的控制方法，其特征在于，应用于如权利要求1所述的柔性励磁***，在机端电压跌落时，所述柔性励磁控制单元利用柔性励磁***快速响应控制能力动态控制顶值电压，具体包括以下步骤：中间直流电容回路的中间直流电压为柔性励磁***的顶值电压，称为柔性励磁***中间直流电压；
    S1，在同步发电机空载起励到并网过程，或者并网解列后的逆变灭磁过程，或者任意工况下同步发电机收到跳灭磁开关令后的灭磁过程，柔性励磁***中间直流电压根据机端电压的变化采取常规两段式控制策略进行控制；
    S2，在同步发电机并网后，柔性励磁***中间直流电压按发电机机端电压的两种运行区间进行控制，分别是发电机机端电压高于常规拐点电压的常规运行区间、发电机机端电压低于常规拐点电压的紧急运行区间；
    A1)当发电机机端电压在常规运行区间时，柔性励磁***中间直流电压按常规固定直流电压设定值进行控制；
    A2)当发电机机端电压在紧急运行区间时，柔性励磁***中间直流电压根据机端电压的变化采取紧急两段式控制策略进行控制。
  9. 如权利要求8所述的柔性励磁***的控制方法，其特征在于，所述常规两段式控制策略，其具体内容包括：
    根据机端电压的不同分为常规线性升压区间和常规恒定电压区间：所述常规线性升压区间是指发电机机端电压从零到常规拐点电压的范围，所述常规恒定电压区间是指发电机机端电压在常规拐点电压以上的范围；
    在常规线性升压区间，柔性励磁***中间直流电压相对励磁变二次线电压按固定的常规升压比设定值进行控制，即中间直流电压等于励磁变二次线电压乘以常规升压比；在常规恒定电压区间，柔性励磁***中间直流电压按常规固定中间直流电压设定值进行控制。
  10. 如权利要求8所述的柔性励磁***的控制方法，其特征在于，所述的常规拐点电压与常规升压比以及常规固定中间直流电压的关系如下：
    Figure PCTCN2021078062-appb-100001
  11. 如权利要求8所述的柔性励磁***的控制方法，其特征在于，所述紧急两段式控制策略，其具体内容包括：
    根据机端电压的不同分为紧急线性升压区间和紧急恒定电压区间：所述紧急线性升压 区间是指发电机机端电压从零到紧急拐点电压的范围，所述紧急恒定电压区间是指发电机机端电压从紧急拐点电压到正常拐点电压的范围；
    在紧急线性升压区间，柔性励磁***中间直流电压相对励磁变二次线电压按固定的紧急升压比设定值进行控制，即中间直流电压等于励磁变二次线电压乘以紧急升压比；在紧急恒定电压区间，柔性励磁***中间直流电压按固定的紧急直流电压设定值进行控制。
  12. 如权利要求11所述的柔性励磁***的控制方法，其特征在于，所述的发电机机端电压的紧急拐点电压与紧急升压比设定值以及紧急固定中间直流电压设定值的关系如下：
    Figure PCTCN2021078062-appb-100002
  13. 根据权利要求8所述的柔性励磁***的控制方法，其特征在于，当发电机在并网状态进入紧急运行区间后，机端电压需恢复至常规运行区间内且超过设定的控制死区，柔性励磁***中间直流电压才能恢复为按常规固定直流电压设定值进行控制。
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