WO2022156681A1 - 用于柔性直流输电系统孤岛运行的控制方法及控制系统 - Google Patents

用于柔性直流输电系统孤岛运行的控制方法及控制系统 Download PDF

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WO2022156681A1
WO2022156681A1 PCT/CN2022/072571 CN2022072571W WO2022156681A1 WO 2022156681 A1 WO2022156681 A1 WO 2022156681A1 CN 2022072571 W CN2022072571 W CN 2022072571W WO 2022156681 A1 WO2022156681 A1 WO 2022156681A1
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WIPO (PCT)
Prior art keywords
control
current
voltage
loop
island
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PCT/CN2022/072571
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English (en)
French (fr)
Inventor
李钢
卢宇
田杰
董云龙
李海英
王柯
殷子寒
肖诗蕾
Original Assignee
南京南瑞继保电气有限公司
南京南瑞继保工程技术有限公司
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Priority claimed from CN202110071233.0A external-priority patent/CN114825419B/zh
Priority claimed from CN202110071232.6A external-priority patent/CN114825367A/zh
Application filed by 南京南瑞继保电气有限公司, 南京南瑞继保工程技术有限公司 filed Critical 南京南瑞继保电气有限公司
Priority to MX2023007693A priority Critical patent/MX2023007693A/es
Priority to EP22742160.9A priority patent/EP4283816A1/en
Publication of WO2022156681A1 publication Critical patent/WO2022156681A1/zh

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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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/388—Islanding, i.e. disconnection of local power supply from the network
    • 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
    • H02J2003/365—Reducing harmonics or oscillations in HVDC
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Definitions

  • the present application relates to the technical field of flexible direct current transmission in power systems, and in particular, to a control method, a control system and an electronic device for island operation of a flexible direct current transmission system.
  • Flexible DC transmission is an optional option for large-scale wind power transmission due to its flexible control mode. DC transmission does not generate reactive power and occupies less sea area. When there is no AC power supply in the AC power grid area connected to the flexible DC converter station or is connected to a new energy system, the flexible DC converter station needs to provide a stable AC voltage for passive systems or new energy in an island control mode.
  • the island control mode adopts open-loop control to directly output a constant AC voltage to avoid oscillation during startup. Since the open-loop control has no feedback link and cannot suppress the interference, when the AC system fails and needs to limit the current, the control mode should be changed to the closed-loop control mode. Tripping of converter station due to fault overcurrent.
  • the closed-loop control integrator may be saturated. During the switching process, the integrator has a desaturation process. System is unstable.
  • the double closed-loop control scheme can effectively suppress the fault current, but the introduction of the inner loop current control will bring about medium and high frequency oscillation.
  • the patent CN201610938897 discloses the double closed loop control method and The article "Summary of Oscillation Phenomenon Analysis and Control Method of Flexible HVDC Transmission System” describes the analysis of medium and high frequency oscillation phenomenon; if open-loop control is used, such as the papers “Research on Black Start Control Capability of Flexible HVDC Transmission System” and "MMC Flexible HVDC Transmission System”
  • the open-loop control mode proposed in "Direct Voltage Control of Passive Network Power Supply", but the open-loop control mode leads to uncontrollable current and tripping, which is not conducive to new energy transmission.
  • the present application proposes a control method for islanding operation of a flexible DC transmission system.
  • the AC system fails, it is converted into a double closed-loop control mode to limit the fault current and suppress interference;
  • the station control system adaptively selects the adaptive island control method with the inner loop current control mode or without the inner loop current control mode according to the operation state of the HVDC flexible transmission system.
  • a control method for island operation of a flexible DC power transmission system wherein the flexible DC power transmission system is connected to an AC system, the flexible DC power transmission system includes an inverter, and the control method includes:
  • the converter starts and operates in a steady state in an open-loop control mode in a start-up state
  • the converter When a fault of the AC system is detected, the converter is converted from the open-loop control mode to a double-closed-loop control mode to limit the fault current and suppress interference;
  • the adaptive islanding control approach includes:
  • the three-phase voltage and three-phase current on the AC side of the HVDC flexible transmission system are collected and converted into the voltage signal under the dq axis and the current signal under the dq axis through the abc/dq coordinate system;
  • the adaptive control mode is selected by selecting the control mode.
  • Island control arm reference wave
  • the selecting a control mode includes selecting an islanding control mode with inner loop current control, or selecting an islanding control mode without inner loop current control.
  • the selection of the islanding control mode with inner loop current control or the selection of the islanding control mode without inner loop current control includes in the startup unlocking and no-load state, when the system power P ⁇ Pset1 or the current peak value is satisfied I peak ⁇ Iset1 or When , choose to operate the island control mode without inner loop current control; otherwise, it will automatically switch to the island mode with inner loop current, wherein, the P set1 ⁇ 0.1pu, I set1 ⁇ 0.1pu.
  • the selecting the islanding control mode with the inner loop current control, or the selecting the islanding control mode without the inner loop current control further includes being in the control mode with the inner loop current control module, when the grid is detected When the side voltage harmonic content Us_h>Us_hset or the current harmonic content I_h>Iv_hset, it will automatically switch to the island control mode without the inner loop current control module, wherein Us_hset ⁇ 0.01pu, Iv_hset ⁇ 0.01pu.
  • the selecting the islanding control mode with the inner loop current control or the islanding control mode without the inner loop current control further includes being under the control of the current control module without the inner loop, when the grid side zero is detected
  • the sequence voltage U 0 >U 0 _set or the grid-side current Is>Is_set or the bridge arm current I b >I b _set it will automatically switch to the in-band current control module, where the U 0 _set ⁇ 0.05pu, Is_set ⁇ 1.15pu, Ib_set ⁇ 1.15pu .
  • the double closed-loop control approach includes:
  • Outer loop control input the AC voltage and frequency of the grid side of the converter, and output the reference value of the active current of the inner loop and the reference value of the reactive current of the inner loop through the proportional integral controller;
  • Inner loop control receives the reference value of the inner loop active current and the reference value of the inner loop reactive current from the control output of the outer loop, and quickly tracks the reference value of the inner loop active current and the reference value of the inner loop reactive current to realize the replacement Direct control of the AC side current waveform and phase of the current transformer.
  • the double closed-loop control method further includes: a current limiting link to control the fault current of the AC system not to exceed the limit.
  • an initial value is assigned to the input of the integrator controlled by the outer loop.
  • the detecting of the AC system failure, the monitoring manner includes:
  • the system changes from open-loop control to double-closed-loop control;
  • the system changes from open-loop control to double closed-loop control;
  • the system changes from open-loop control to double closed-loop control;
  • the system changes from open-loop control to double closed-loop control.
  • the system voltage preset low value Us_setL ⁇ 1pu the system voltage preset high value Us_setH ⁇ 1pu
  • the DC voltage preset low value UDC_setL ⁇ 1pu the DC voltage preset high value UDC_setH ⁇ 1pu
  • the AC valve side Zero-sequence voltage threshold U0_set ⁇ 0pu grid-side current threshold Is_set ⁇ 1pu, bridge arm current threshold Ib_set ⁇ 1pu, active power threshold P_set ⁇ 1pu, system frequency preset low value f_setL ⁇ 50Hz, system frequency preset high value f_setH>50Hz
  • pu is the unit of per-unit value
  • the per-unit value is the relative value of the actual value and the rated value.
  • the flexible direct current transmission system operates with or without load when operating in an island.
  • a control system for island operation of a flexible direct current transmission system comprising: a collection and conversion unit configured to pass the collected three-phase voltage and three-phase current on the AC side of the flexible direct current transmission system through a The abc/dq coordinate system is converted into the voltage signal under the dq axis and the current signal under the dq axis; the adaptive island control unit is used to set the reference value according to the received voltage, the frequency setting reference value, the voltage signal under the dq axis and the The current signal, the three-phase voltage signal and the three-phase current signal on the AC side of the flexible DC power transmission system pass through the adaptive island control unit to generate an adaptive island control bridge arm reference wave.
  • the adaptive islanding control unit includes an islanding control module with inner loop current control for generating a dq axis closed-loop voltage reference wave; an islanding control module without inner loop current control for generating dq Shaft open-loop voltage reference wave; frequency phase control module for generating synchronous phase signal for the conversion of abc/dq coordinate system of the acquisition conversion unit and dq/abc coordinate system conversion of the reference wave generation module; adaptive island control selection module , used to select the island control module with inner loop current control or the island control module without inner loop current control; the reference wave generation module is used to receive the synchronous phase signal of the frequency phase control module and convert the dq/abc coordinate system, And generate six bridge arm reference waves.
  • the islanding control module with inner loop current control includes converting the received voltage setting reference value, the dq-axis lower voltage signal and the dq-axis lower current signal into a dq-axis closed-loop voltage reference wave output signal.
  • the islanding control module without inner loop current control includes converting the voltage setting reference value and the dq-axis lower voltage signal into an output signal of a dq-axis open-loop voltage reference wave.
  • the adaptive islanding control selection module includes a three-phase voltage signal and a three-phase current signal on the AC side of the flexible DC transmission system, the dq-axis closed-loop voltage reference wave, the dq-axis open-loop The voltage reference wave is converted into an output signal that adapts to the input reference wave voltage.
  • voltage outer loop controllers and current loop controllers in both the islanding control module with inner loop current control and the islanding control module without inner loop current control include PI controllers and/or or PR controller.
  • an electronic device comprising: one or more processors; a storage device for storing one or more programs; when the one or more programs are executed by the one or more processors, the One or more processors implement the control method as above.
  • the islanded open-loop mode operation avoids high-frequency oscillation caused by connecting transformers or short no-load lines, and the system is switched from open-loop mode to double-closed-loop control mode in the event of a fault, effectively suppressing fault overcurrent .
  • the collected three-phase voltage and three-phase current on the AC side of the flexible direct current transmission system are converted into the voltage signal under the dq axis and the dq axis through the abc/dq coordinate system through the acquisition and conversion unit.
  • Lower current signal automatically switch to current control without inner loop through the adaptive island control unit, because there is no negative resistance caused by delays such as sampling control, the system can be stabilized, and the negative resistance component introduced by closed-loop control can be avoided.
  • the problem of medium and high frequency oscillation provides a more optimal solution for large-scale new energy access.
  • FIG. 1 shows a schematic diagram of a flexible DC power transmission system according to an exemplary embodiment of the present application.
  • FIG. 2 shows a schematic flowchart of a control method for island operation of a flexible direct current transmission system according to an exemplary embodiment of the present application.
  • FIG. 3 shows a schematic flowchart of an open-loop control manner according to an exemplary embodiment of the present application.
  • FIG. 4 shows a schematic diagram of a double closed-loop control manner according to the first exemplary embodiment of the present application.
  • FIG. 5 shows a schematic diagram of a double closed-loop control manner according to the second exemplary embodiment of the present application.
  • FIG. 6 is a schematic diagram illustrating the composition of a flexible DC power transmission system connected to a new energy source or a passive system according to another exemplary embodiment of the present application.
  • FIG. 7 shows a flowchart of an adaptive islanding control method according to an exemplary embodiment of the present application.
  • FIG. 8 shows a schematic diagram of a control system for island operation of a flexible direct current transmission system according to an embodiment of the present application.
  • FIG. 9 shows a schematic structural diagram of an adaptive control unit according to an embodiment of the present application.
  • FIG. 10 shows a block diagram of an electronic device for islanding operation control of a flexible direct current transmission system according to an embodiment of the present application.
  • Example embodiments will now be described more fully with reference to the accompanying drawings.
  • Example embodiments can be embodied in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art.
  • the same reference numerals in the drawings denote the same or similar parts, and thus their repeated descriptions will be omitted.
  • FIG. 1 shows a schematic diagram of a flexible DC power transmission system according to an exemplary embodiment of the present application.
  • the flexible DC power transmission system includes an AC system, an inverter, a connection transformer 3 , a new energy source 1 and a DC field device 4 .
  • the primary side of the connection transformer 3 is connected to the new energy source 1 through the incoming switch 2, the secondary side of the connection transformer 3 is connected to the converter and the DC field equipment 4, and the converter and the DC field equipment 4 are connected to the pair through the DC line 5.
  • the converter and DC field equipment 6 of the station and the converter of the opposite station and the DC field equipment 6 are connected to the AC grid or power source 9 through the connection transformer 7 of the opposite station and the primary side switch 8 of the opposite station.
  • FIG. 2 shows a schematic flowchart of a control method for island operation of a flexible direct current transmission system according to an exemplary embodiment of the present application.
  • the flexible DC transmission system When the flexible DC transmission system operates in an island, it can run with or without load.
  • the flexible DC transmission system After the flexible DC transmission system is unlocked in the island mode, it is started in an open-loop control mode.
  • the open-loop control mode is adopted when the island of the flexible DC transmission system is started.
  • the voltage reference wave starts from 0kV and rises to the rated voltage UN kV at a rate of kV/s.
  • the flexible DC transmission system maintains the open-loop control operation. Provide stable voltage amplitude and frequency for new energy systems or passive AC systems.
  • This startup method avoids large disturbances and shocks during island startup, suppresses high-frequency components and distortions of output voltage and current, and maintains stable operation of the system.
  • the converter when the flexible direct current transmission system is operating in an island, in a non-fault state, the converter is operated in an open-loop control mode in a steady state or in an adaptive island control mode.
  • the open-loop control method is the same as the control method in the startup process, and will not be repeated here; the adaptive islanding control method will be introduced in detail below.
  • AC system fault is detected, and the detection methods include voltage criterion, current criterion, power criterion and frequency criterion.
  • the system changes from open-loop control to double closed-loop control.
  • the preset low value of system voltage U s_setL ⁇ 1pu the preset high value of system voltage U s_setH ⁇ 1pu
  • the preset low value of DC voltage U DC_setL ⁇ 1pu the preset high value of DC voltage U DC_setH ⁇ 1pu
  • the sequence voltage threshold U 0_set ⁇ 0pu pu is the unit of per unit value, and the per unit value here is the relative value of the actual value and the rated value.
  • the system changes from open-loop control to double closed-loop control.
  • the grid-side current threshold I s_set ⁇ 1pu, and the bridge arm current threshold I b_set ⁇ 1pu are included in the grid-side current threshold I s_set ⁇ 1pu.
  • the system changes from open-loop control to double closed-loop control.
  • the active power threshold P _set ⁇ 1pu the active power threshold P _set ⁇ 1pu.
  • the double closed-loop control mode includes outer-loop control and inner-loop control, as shown in Figure 4.
  • the outer loop control input the inverter grid side AC voltage U d and the preset inverter grid side AC voltage d-axis component U d * , the difference is input to the proportional-integral controller PI, through the proportional-integral controller, the inner loop is output. Active current reference value. Input the inverter grid side AC voltage U q and the preset inverter grid side AC voltage q axis component U q * , the difference is input to the proportional integral controller PI, and through the proportional integral controller, the inner loop reactive current reference value is output .
  • the inner loop control receive the reference value of the inner loop active current and the reference value of the inner loop reactive current from the outer loop control, and quickly track the reference value of the inner loop active current, the reference value of the inner loop reactive current and the preset frequency reference value f ref * , to achieve direct control of the AC side current waveform and phase of the converter.
  • the outer loop controls the output voltage amplitude and frequency
  • the inner loop controls the current
  • hit A it is open-loop control mode
  • hit B it is double closed-loop control mode
  • the double closed-loop control mode further includes a current limiting link Idmax, which controls the fault current of the AC system to not exceed the limit, as shown in FIG. 5 .
  • the current limiting link is set between the channels controlled by the outer loop and the inner loop to avoid tripping of the flexible DC transmission system due to overcurrent in the event of a fault.
  • the islanded open-loop operation can avoid high-frequency oscillation caused by connecting transformers or short no-load lines; when a fault occurs, the system changes from open-loop to double-closed-loop control, effectively suppressing fault overcurrent.
  • the control switching process by assigning the initial value to the input of the integrator controlled by the outer loop, the control failure and the instability of the system caused by the desaturation process of the integrator controlled by the closed loop control are avoided.
  • FIG. 6 is a schematic diagram illustrating the composition of a flexible DC power transmission system (eg, a flexible DC power transmission converter station) connected to a new energy source or a passive system according to another exemplary embodiment of the present application.
  • a flexible DC power transmission system eg, a flexible DC power transmission converter station
  • a new energy system 1000 for connecting a flexible DC power transmission converter station to an offshore wind power usually includes an AC booster station 1001 and an offshore flexible DC power transmission converter station 2001 (hereinafter referred to as the Offshore converter station) and onshore converter station 3001.
  • the electric energy generated by the offshore wind farm is boosted by the AC booster station 1001 and connected to the offshore converter station 2001 .
  • the DC power is output through the offshore converter station 2001 and connected to the onshore converter station 3001 through the submarine cable 4000, thereby realizing the transmission of wind farm power from the sea to the onshore AC grid 5000.
  • the offshore converter station 2001 generally includes: an AC bus 2100, a station transformer 2200, a connecting transformer 2300, a valve-side bus 2400, a valve-side switch (not shown), a converter valve and a DC field device 2600, and Corresponding measuring or control equipment.
  • the converter valve and DC field equipment 2600 generally includes a converter valve, a bridge arm reactor, a DC field equipment, and the like.
  • the wind power generated by the offshore wind farm is boosted and then connected to the AC bus 2100 of the offshore converter station 2001 .
  • the AC bus 2100 is connected to the valve side bus 2400 through two sets of parallel connection transformers 2300 .
  • the valve side bus 2400 is connected to the AC side of the converter valve and the DC field device 2600 .
  • the offshore converter station 2001 supplies power to other equipment of the offshore converter station through the high-voltage station electrical transformer 2200.
  • the offshore converter station generates a stable AC voltage through island control for grid connection of new offshore wind power.
  • FIG. 7 shows a flowchart of an adaptive islanding control method according to an exemplary embodiment of the present application.
  • the collected three-phase voltages and three-phase currents on the AC side of the HVDC transmission system are converted into dq-axis voltage signals and dq-axis current signals through the abc/dq coordinate system.
  • control mode is selected according to the received voltage setting reference value, the frequency setting reference value, the voltage signal and the current signal under the dq axis, the three-phase voltage signal and the three-phase current signal on the AC side of the flexible DC transmission system, Generate an adaptive island control bridge arm reference wave.
  • selecting a control mode includes selecting an islanding control mode with inner loop current control, or selecting an islanding control mode without inner loop current control.
  • the specific switching process of the two modes will be described in detail with reference to FIG. 9 .
  • FIG. 8 shows a schematic diagram of a control system for island operation of a flexible direct current transmission system according to an embodiment of the present application.
  • the adaptive islanding control method for a flexible DC transmission converter station includes:
  • the three-phase voltage and three-phase current of the AC side of the flexible DC transmission system are collected and converted into a voltage signal under the dq axis and a current signal under the dq axis through the abc/dq coordinate system.
  • the adaptive control mode is selected by selecting the control mode.
  • Island control arm reference wave
  • selecting a control mode includes selecting an islanding control mode with inner loop current control, or selecting an islanding control mode without inner loop current control.
  • the specific selection of the embodiment of the control mode as described above will be described later with reference to FIG. 9 .
  • the specific structure of the control system will be described below with reference to FIG. 8 .
  • an adaptive island control system 2000 for a flexible HVDC converter station includes a collection conversion unit 100 and an adaptive island control unit 200 .
  • the acquisition and conversion unit 100 is configured to convert the acquired three-phase voltage and three-phase current on the AC side of the flexible direct current transmission system into a dq-axis voltage signal and a dq-axis current signal through the abc/dq coordinate system.
  • the adaptive islanding control unit 200 is used to set the reference value according to the received voltage, the voltage signal and current signal under the dq axis, the three-phase voltage signal and the three-phase current signal reflecting the flexible direct running state, and pass through the adaptive islanding control unit to generate the self-adaptive islanding control unit.
  • the acquisition and conversion unit 100 includes a first input terminal 101 , a second input terminal 102 , a third input terminal 103 , a first output terminal 111 , and a second output terminal 112 .
  • the first input terminal 101 is used for receiving the three-phase voltage signal on the AC side of the flexible DC transmission system.
  • the second input terminal 102 is used for receiving the three-phase current signal on the AC side of the flexible DC power transmission system.
  • the third input terminal 103 is used for receiving the synchronized phase angle signal.
  • the first output terminal 111 is used for outputting a voltage signal reflecting the flexible DC operating state.
  • the second output terminal 112 is used for outputting a current signal reflecting the operating state of the flexible DC.
  • the adaptive islanding control unit 102 includes a first input 201, a second input 202, a third input 203, a fourth input 204, a fifth input 211, a sixth input 212, a first output A terminal 261 , a second output terminal 262 , a third output terminal 263 , a fourth output terminal 264 , a fifth output terminal 265 , a sixth output terminal 266 , and a seventh output terminal 267 .
  • the first input terminal 201 is used for receiving a voltage setting reference value.
  • the second input terminal 202 is used for receiving the frequency setting reference value to generate the synchronized phase angle signal to the third input terminal of the acquisition conversion unit and to generate a reference wave by itself.
  • the third input terminal 203 is used for receiving a voltage signal reflecting the operating state of the flexible DC.
  • the fourth input terminal 204 is used for receiving a current signal reflecting the operating state of the flexible DC.
  • the fifth input terminal 211 is used for receiving the dq-axis lower voltage signal.
  • the sixth input terminal 212 is used for receiving the current signal under the dq axis.
  • the first output terminal 261, the second output terminal 262, the third output terminal 263, the fourth output terminal 264, the fifth output terminal 265, and the sixth output terminal 266 respectively output the three-phase upper bridge arm and the three-phase upper bridge arm of the adaptive islanding control unit. Phase lower arm reference wave.
  • the seventh output terminal 267 is used for outputting the synchronized phase angle signal.
  • the first output terminal 111 of the acquisition conversion unit is connected to the fifth input terminal 211 of the adaptive island control unit, and the second output terminal 112 of the acquisition conversion unit is connected to the sixth input terminal of the adaptive island control unit 212.
  • the seventh output terminal 267 of the adaptive islanding control unit is connected to the third input terminal 103 of the acquisition and conversion unit.
  • the acquisition and conversion unit 100 is configured to convert the collected three-phase voltage and three-phase current on the AC side of the flexible DC to a voltage Udq and a current Idq under the dq axis through abc/dq according to the received position angle signal.
  • the three-phase current reaches the acquisition and conversion unit 100 through the first input terminal 101 and the second input terminal 102 of the acquisition and conversion unit respectively; phase angle signal.
  • the first output terminal 101 and the second output terminal 102 of the acquisition conversion unit 100 can be combined into one output terminal and sent to the adaptive islanding control unit 200.
  • the first output terminal of the adaptive islanding control unit 200 The five input terminals 211 and the sixth input terminal 212 can be combined into one input terminal to receive the signal output by the acquisition and conversion unit 100 .
  • the third input terminal 203 and the fourth input terminal 204 of the adaptive islanding control unit 200 can also be combined into the fifth input terminal 211 and the sixth input terminal 212, omitting the third input terminal 203 and the fourth input terminal 204,
  • the three-phase voltage signal and the three-phase current signal are output by the first output terminal 101 and the second output terminal 102 of the acquisition unit 100 and directly sent to the fifth input terminal 211 and the sixth input terminal 212 of the adaptive islanding control unit 200 .
  • the adaptive islanding control unit 200 is used to set the reference value according to the received voltage
  • the voltage Udq and current Idq under the and dq axis are controlled by adaptive islanding according to the three-phase voltage and current reflecting the flexible direct running state, and the reference wave of the bridge arm of adaptive islanding control is generated.
  • the adaptive islanding control unit 200 generates the phase angle signal ⁇ according to the received frequency setting reference value f_ref to the acquisition and conversion unit 100 and generates a reference wave for use by itself.
  • the voltage setting reference value of The frequency setting reference value f_ref, the dq-axis voltage Udq and the dq-axis current Idq are sent to the adaptive control unit through the first input terminal 201 , the second input terminal 202 , the fifth input terminal 211 and the sixth input terminal 212
  • the islanding control unit 200; the three-phase voltage and three-phase current signals reflecting the flexible DC operating state are sent to the adaptive islanding control 200 through the third input end 203 and the fourth input end 204 of the adaptive control unit, respectively.
  • An output terminal 261, a second output terminal 262, a third output terminal 263, a fourth output terminal 264, a fifth output terminal 265, and a sixth output terminal 266 respectively output the flexible DC three-phase upper arm and the three-phase lower arm reference
  • the wave is transmitted to the flexible DC valve control system (not shown in the figure), and the seventh output terminal 267 of the island control unit outputs the phase angle signal ⁇ to the third input terminal 103 of the acquisition conversion unit.
  • FIG. 9 shows a schematic structural diagram of an adaptive islanding control unit 200 according to an embodiment of the present application.
  • the adaptive islanding control unit 200 includes an islanding control module 210 with inner loop current control, an islanding control module 220 without inner loop current control, and a frequency phase control module 230 , an adaptive island control selection module 240 , and a reference wave generation module 250 .
  • the islanding control module 210 with inner loop current control is used to generate the dq axis closed loop voltage reference wave.
  • the islanding control module 220 without inner loop current control is used to generate the dq axis open loop voltage reference wave.
  • the frequency-phase control module 230 is used for generating a synchronization phase signal for the conversion of the abc/dq coordinate system of the acquisition conversion unit and the conversion of the dq/abc coordinate system of the reference wave generation module.
  • the adaptive island control selection module 240 is used to select an island control module with inner loop current control or an island control module without inner loop current control.
  • the reference wave generation module 250 is configured to receive the synchronization phase signal of the frequency phase control module, convert the dq/abc coordinate system, and generate six bridge arm reference waves.
  • the islanding control module 210 with inner loop current control includes a first input terminal 213 , a second input terminal 214 , a third output terminal 215 and a first output terminal 217 .
  • the first input terminal 213 is used for receiving a voltage setting reference value.
  • the second input terminal 214 is used for receiving the dq-axis lower voltage signal.
  • the third input terminal 215 is used for receiving the current signal under the dq axis.
  • the first output terminal 217 is used for outputting the dq-axis closed-loop voltage reference wave.
  • the islanding control module 220 without inner loop current control includes a first input terminal 221, a second input terminal 222, and a first output terminal 226.
  • the first input terminal 221 is used for receiving a voltage setting reference value.
  • the second input terminal 222 is used for receiving the voltage signal under the dq axis.
  • the first output terminal 226 is used for outputting the dq-axis open-loop voltage reference wave.
  • the adaptive islanding control selection module includes a first input terminal 241 , a second input terminal 242 , a third input terminal 243 , a fourth input terminal 244 and a first output terminal 246 .
  • the first input terminal 241 is used for receiving a voltage signal reflecting the operating state of the flexible DC.
  • the second input terminal 242 is used for receiving a current signal reflecting the operating state of the flexible DC.
  • the third input terminal 243 is used for receiving the dq-axis closed-loop voltage reference wave.
  • the fourth input terminal 244 is used for receiving the dq-axis open-loop voltage reference wave.
  • the first output terminal 246 is used for outputting the adaptive input reference wave voltage.
  • the first output terminal 217 of the islanding control module 210 with inner loop current control is connected to the third input terminal 243 of the adaptive islanding control selection module 240; the first output terminal 226 of the islanding control module 220 without inner loop current control is connected The fourth input terminal 244 of the adaptive island control selection module 240 is connected; the output terminal 232 of the frequency phase control module 230 is connected to the second input terminal 252 of the reference wave generation module; the first output terminal 246 of the adaptive island control selection module 240 is connected to The first input terminal 251 of the reference wave generation module.
  • the islanding control module 210 with inner loop current control is used to set the reference value according to the received voltage and dq axis voltage Udq through the outer loop voltage controller to generate the current reference wave Idq_ref, the current reference wave Idq_ref and the dq axis current Idq pass through the inner loop current controller to generate the dq axis closed loop voltage reference wave Udq_ref_cl with current closed loop control and send it to the adaptive
  • the third input terminal 243 of the island control selection module wherein the voltage is set as a reference value
  • the dq-axis voltage Udq and the dq-axis current Idq are sent to the first input terminal 213 , the second input terminal 214 and the third input terminal 215 of the islanding control module with inner loop current control.
  • the islanding control module 220 without inner loop current control is used to set the reference value according to the received voltage and the dq-axis voltage Udq through the outer-loop voltage control to generate a dq-axis open-loop voltage reference wave Udq_ref_op without current closed-loop control, which is sent to the fourth input terminal 244 of the adaptive islanding control selection module 240; the voltage setting reference value and the dq axis voltage Udq are sent to the first input terminal 221 and the second input terminal 222 of the islanding control module without inner loop current control.
  • the frequency and phase control module 230 is configured to generate a synchronization phase signal according to the received frequency setting reference value f_ref for use by the acquisition conversion module abc/dq conversion and the reference wave generation module dq/abc conversion.
  • the frequency setting reference value f_ref is connected to the first input terminal 231 of the frequency phase control module.
  • the first output terminal 232 of the frequency and phase control module is connected to the third input terminal 252 of the reference wave generation module.
  • the adaptive island control selection module 240 is used to adaptively select the dq-axis closed-loop voltage reference wave Udq_ref_cl with current closed-loop control or the dq-axis open-loop voltage reference wave Udq_ref_op without current closed-loop control according to the flexible DC operation state, and the flexible DC operation state is determined by The three-phase voltage and three-phase current or the three-phase voltage and three-phase current integrated quantity are used for self-adaptive judgment and selection.
  • the flexible DC operating state is connected to the first input terminal 241 and the second input terminal 242 of the adaptive islanding control selection module by three-phase voltage and three-phase current.
  • the dq-axis closed-loop voltage reference wave Udq_ref_cl with current closed-loop control or the dq-axis open-loop voltage reference wave Udq_ref_op without current closed-loop control is respectively sent to the third input terminal 243 and the fourth input terminal 244 of the adaptive islanding control selection module.
  • the adaptive input reference wave selected after the adaptive judgment according to the flexible straight running state is sent to the output terminal 246 of the adaptive island control selection module.
  • the reference wave generation module 250 is used to convert the dq voltage reference wave and the synchronous phase signal of the frequency phase control according to the dq voltage reference wave output by the adaptive island control selection module to the abc coordinate through dq/abc, and then generate the six bridge arm references required for valve control. Wave.
  • the output dq-axis reference voltage of the adaptive island control selection module is sent to the first input terminal 251 of the reference wave generation module, and the generated six bridge arm reference waves are respectively sent to the first output terminal 254 to the sixth output of the reference wave generation module. end 259.
  • the selection criteria for the dq-axis closed-loop voltage reference wave Udq_ref_cl with current closed-loop control or the dq-axis open-loop voltage reference wave Udq_ref_op without current closed-loop control are as follows:
  • the command value, Udq_ref_cl, Udq_ref_op, represents the positive sequence component and the negative sequence component, a total of four components.
  • the input terminals 251 and 252 of the reference wave generation module 250 respectively receive the dq-axis adaptive input reference wave and the synchronous phase angle signal
  • the three-phase voltage Ux_ref(a, b, c is generated for positive and negative sequence superposition)
  • the voltage outer loop control and current loop controller in the island control module with inner loop current control and the island control module without inner loop current control can be a PI controller or a PR controller.
  • FIG. 10 shows a block diagram of an electronic device for islanding operation control of a flexible direct current transmission system according to an embodiment of the present application.
  • electronic device 400 takes the form of a general-purpose computing device.
  • Components of the electronic device 400 may include, but are not limited to, at least one processing unit 410, at least one storage unit 420, a bus 430 connecting different system components (including the storage unit 420 and the processing unit 410), a display unit 440, and the like.
  • the storage unit stores program codes, and the program codes can be executed by the processing unit 410, so that the processing unit 410 executes the control methods described in this specification according to various exemplary embodiments of the present application.
  • the bus 430 may be representative of one or more of several types of bus structures, including a memory cell bus or memory cell controller, a peripheral bus, a graphics acceleration port, a processing unit, or a local area using any of a variety of bus structures. bus.
  • the electronic device 400 may also communicate with one or more external devices 500 (eg, keyboards, pointing devices, Bluetooth devices, etc.), with one or more devices that enable a user to interact with the electronic device 400, and/or with Any device (eg, router, modem, etc.) that enables the electronic device 400 to communicate with one or more other computing devices. Such communication may occur through input/output (I/O) interface 450 . Also, the electronic device 400 may communicate with one or more networks (eg, a local area network (LAN), a wide area network (WAN), and/or a public network such as the Internet) through a network adapter 460 . Network adapter 460 may communicate with other modules of electronic device 400 through bus 430 . It should be understood that, although not shown, other hardware and/or software modules may be used in conjunction with electronic device 400, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives and data backup storage systems.
  • the self-adaptive island control mode of the island operation of the flexible HVDC transmission system of the present application enables the control system of the flexible HVDC converter station connected to the new energy source to adaptively select to adopt the inner loop current control mode or the non-inner loop current control mode according to the operation state of the flexible HVDC transmission system.
  • the adaptive islanding control method of loop current control mode can stabilize the system by automatically switching to no inner loop current control, because there is no negative resistance caused by delays such as sampling control, and avoid the negative resistance component introduced by closed-loop control. Therefore, the risk of medium and high frequency oscillation is avoided, and the fault current is controllable in the fault state.

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Abstract

本申请提供一种用于柔性直流输电系统孤岛运行的控制方法，该控制方法包括：柔性直流输电系统孤岛运行时，在启动状态以开环控制方式实现所述换流器启动和稳态运行；当检测到交流系统故障时，换流器由开环控制方式转为双闭环控制方式来限制故障电流抑制干扰；在非故障状态，以自适应孤岛控制方式运行；或，在非故障状态，以开环控制方式实现换流器稳态运行。在交流系统故障时，转为双闭环控制方式来限制故障电流抑制干扰；在孤岛运行时，通过自动切换到不带内环电流控制，因不存在采样控制等延时造成的负阻，能够使系统稳定，避免了因闭环控制引入负阻分量造成的中高频振荡问题，为大规模新能源接入提供更优选方案。

Description

用于柔性直流输电系统孤岛运行的控制方法及控制系统 技术领域
本申请涉及电力系统柔性直流输电技术领域，具体而言，涉及一种用于柔性直流输电系统孤岛运行的控制方法、控制系统及电子设备。
背景技术
为了解决碳排放增加而导致的全球变暖的问题，新能源发电作为一种绿色能源，越来越受到各国政府重视及青睐。风力发电、光伏发电等作为绿色能源越来越受到各国重视，世界各主要国家正在大规模开展包括风电、光伏发电的新能源。大规模光伏和风电资源一般远离负荷中心，离负荷中心较近的大规模海上风电资源需要经过电缆传输，如何实现大规模新能源高效高质量地接入电网是目前新能源并网的难点。海
上风电虽然离负荷中心近，但因为采用电缆，当风电场距离岸边超过60km，采用传统的交流输出方式使得功率损耗、海域占地、无功补偿等难度逐渐增加，使交流接入优势降低。柔性直流传输于其灵活的控制模式，直流传输不产生无功功率、少海域占地成为大规模风电传输的可选选项。当柔性直流换流站接入的交流电网区域内无交流电源或者接入新能源系统时，柔性直流换流站需要以孤岛控制模式为无源系统或者新能源提供稳定的交流电压。
考虑到柔性直流换流站以孤岛模式启动时容易引起高频振荡，启动时孤岛控制模式采用开环控制直接输出恒定交流电压来避免振荡。由于开环控制没有反馈环节无法抑制干扰，当交流系统发生故障需要限流时，控制方式宜转为闭环控制模式，通过在控制器中设置限流环节控制故障电流不越限，可避免柔直换流站由于故障过流引起的跳闸。目前，开环和闭环相结合的控制存在着切换后引起系统不稳定的问题，闭环控制积分器可能存在饱和的情况，切换过程中积分器有一个退饱和的过程，这个过程中闭环控制失效导致系统不稳定。
柔性直流输电系统以孤岛模式稳定运行时，采用双闭环控制方案能够有效抑制故障电流，但因内环电流控制的引入将带来中高频振荡，具体地，例如，专利CN201610938897公开双闭环控制方法和文章《柔性直流输电系统振荡现象分析与控制方法综述》描述了中高频振荡现象分析；如采用开环控制，如论文《柔性直流输电系统的黑启动控制能力研究》和《MMC 型柔性直流输电系统无源网络供电的直接电压控制》提出的开环控制模式，但开环控制模式导致电流不可控从而跳闸，不利于新能源传输。
在所述背景技术部分公开的上述信息仅用于加强对本申请的背景的理解，因此它可以包括不构成对本领域普通技术人员已知的现有技术的信息。
发明内容
本申请提出一种用于柔性直流输电系统孤岛运行的控制方法，在交流系统故障时，转为双闭环控制方式来限制故障电流抑制干扰；在孤岛运行时，使得连接新能源的柔直换流站控制系统根据柔性直流输电系统运行状态，自适应地选择采用带内环电流控制模式或者不带内环电流控制模式的自适应孤岛控制方法，通过自动切换到不带内环电流控制，因不存在采样控制等延时造成的负阻，能够使系统稳定，避免了因闭环控制引入负阻分量造成的中高频振荡问题，从而避免中高频振荡风险，也实现了故障状态下故障电流可控。
根据本申请的一方面，提供一种用于柔性直流输电系统孤岛运行的控制方法，所述柔性直流输电系统连接交流系统，所述柔性直流输电系统包括换流器，所述控制方法包括：
所述柔性直流输电系统孤岛运行时，在启动状态以开环控制方式实现所述换流器启动和稳态运行；
当检测到所述交流系统故障时，所述换流器由所述开环控制方式转为双闭环控制方式来限制故障电流抑制干扰；
在非故障状态，以自适应孤岛控制方式运行；或
在非故障状态，以开环控制方式实现所述换流器稳态运行。
根据示例实施例，所述自适应孤岛控制方式包括：
采集柔性直流输电系统交流侧的三相电压和三相电流经过abc/dq坐标系转换为dq轴下电压信号和dq轴下电流信号；
根据接收到电压设定参考值、频率设定参考值、所述dq轴下电压信号和电流信号、柔性直流输电系统交流侧的三相电压信号和三相电流信号通过选择控制模式，产生自适应孤岛控制桥臂参考波。
根据示例实施例，所述选择控制模式，包括选择带内环电流控制的孤岛控制模式，或者选择不带内环电流控制的孤岛控制模式。
根据实施例，所述选择带内环电流控制的孤岛控制模式，或者选择不带内环电流控制的孤岛控制模式，包括在启动解锁和空载状态下，当满足系统功率P<Pset1或者电流峰值I peak<Iset1或 者
Figure PCTCN2022072571-appb-000001
时，选择运行不带内环电流控制的孤岛控制模式；否则将自动切换到采用带内环电流的孤岛模式，其中，所述P set1≤0.1pu，I set1≤0.1pu。
根据示例实施例，所述选择带内环电流控制的孤岛控制模式，或者选择不带内环电流控制的孤岛控制模式，还包括已处于带内环电流控制模块的控制模式下，当检测到网侧电压谐波含量Us_h>Us_hset或者电流谐波含量I_h>Iv_hset时，则自动切换到不带内环电流控制模块的孤岛控制模式，其中，所述Us_hset≥0.01pu，Iv_hset≥0.01pu。
根据示例实施例，所述选择带内环电流控制的孤岛控制模式，或者不带内环电流控制的孤岛控制模式，还包括已处于不带内环电流控制模块控制下，当检测到网侧零序电压U 0>U 0_set或网侧电流Is>Is_set或桥臂电流I b>I b_set时，则自动切换到带内环电流控制控制模块，其中，所述U 0_set≥0.05pu，Is_set≥1.15pu，I b_set≥1.15pu。
根据示例实施例，所述双闭环控制方式包括：
外环控制，输入换流器网侧交流电压和频率，经过比例积分控制器，输出内环有功电流参考值和内环无功电流参考值；
内环控制，接收来自所述外环控制输出的内环有功电流参考值、内环无功电流参考值，并快速跟踪所述内环有功电流参考值、内环无功电流参考值，实现换流器的交流侧电流波形和相位的直接控制。
根据示例实施例，所述双闭环控制方式还包括：限流环节，控制所述交流系统的故障电流不越限。
根据示例实施例，所述由所述开环控制方式转为双闭环控制方式时，给外环控制的积分器的输入赋初值。
根据示例实施例，所述检测到所述交流系统故障，监测方式包括：
根据电压判据，当系统电压Us<系统电压预设低值Us_setL或Us>系统电压预设高值Us_setH，或当直流电压UDC<直流电压预设低值UDC_setL或UDC>直流电压预设高值UDC_setH，或当交流阀侧零序电压U0>交流阀侧零序电压阈值U0_set时，系统由开环控制方式转为双闭环控制；
根据电流判据，当网侧电流Is>网侧电流阈值Is_set或桥臂电流Ib>桥臂电流阈值Ib_set时，系统由开环控制方式转为双闭环控制；
根据功率判据，当有功功率P<有功功率阈值P_set.时，系统由开环控制方式转为双闭环控制；
根据频率判据，当系统频率f<系统频率预设低值f_setL或f>系统频率预设高值f_setH时，系统由开环控制方式转为双闭环控制。
根据示例实施例，所述系统电压预设低值Us_setL≤1pu，系统电压预设高值Us_setH≥1pu； 直流电压预设低值UDC_setL≤1pu，直流电压预设高值UDC_setH≥1pu；交流阀侧零序电压阈值U0_set≥0pu，网侧电流阈值Is_set≥1pu，桥臂电流阈值Ib_set≥1pu，有功功率阈值P_set≤1pu，系统频率预设低值f_setL<50Hz，系统频率预设高值f_setH>50Hz，其中，pu为标幺值单位，所述标幺值为实际值与额定值的相对值。
根据示例实施例，所述柔性直流输电系统孤岛运行时，带负载运行或不带负载运行。
根据本申请的另一方面，提供一种用于柔性直流输电系孤岛运行的控制系统，包括：采集转换单元，用于将采集到的柔性直流输电系统交流侧的三相电压和三相电流经过abc/dq坐标系转换为dq轴下电压信号和dq轴下电流信号；自适应孤岛控制单元，用于根据接收到电压设定参考值、频率设定参考值、所述dq轴下电压信号和电流信号、所述柔性直流输电系统交流侧的三相电压信号和三相电流信号经过所述自适应孤岛控制单元，产生自适应孤岛控制桥臂参考波。
根据示例实施例，所述的自适应孤岛控制单元，包括带内环电流控制的孤岛控制模块，用于产生dq轴闭环电压参考波；不带内环电流控制的孤岛控制模块，用于产生dq轴开环电压参考波；频率相位控制模块，用于产生同步相位信号供所述采集转换单元的abc/dq坐标系转换及参考波生成模块dq/abc坐标系转换使用；自适应孤岛控制选择模块，用于选择带内环电流控制的孤岛控制模块或者不带内环电流控制的孤岛控制模块；参考波生成模块，用于接收所述频率相位控制模块的同步相位信号转换dq/abc坐标系，以及产生六个桥臂参考波。
根据示例实施例，所述带内环电流控制的孤岛控制模块，包括将接收所述电压设定参考值、所述dq轴下电压信号和所述dq轴下电流信号转化成dq轴闭环电压参考波的输出信号。
根据示例实施例，所述不带内环电流控制的孤岛控制模块，包括将所述电压设定参考值和所述dq轴下电压信号转化为dq轴开环电压参考波的输出信号。
根据示例实施例，所述自适应孤岛控制选择模块，包括将所述柔性直流输电系统交流侧的三相电压信号和三相电流信号、所述dq轴闭环电压参考波、所述dq轴开环电压参考波转化成自适应输入参考波电压的输出信号。
根据示例实施例，所述带内环电流控制的孤岛控制模块和所述不带内环电流控制的孤岛控制模块两者中的电压外环控制器和电流环控制器，包括PI控制器和/或PR控制器。
根据本申请的一方面，提出一种电子设备，包括：一个或多个处理器；存储装置，用于存储一个或多个程序；当一个或多个程序被一个或多个处理器执行，使得一个或多个处理器实现如上文的控制方法。
根据本申请的技术方案，在启动阶段，孤岛开环方式运行避免连接变压器或短的空载线路引起的高频振荡，故障时系统由开环方式转为双闭环控制方式，有效抑制故障 过流。
根据本申请的技术方案，在正常运行阶段，通过采集转换单元将采集到的柔性直流输电系统交流侧的三相电压和三相电流经过abc/dq坐标系转换为dq轴下电压信号和dq轴下电流信号；通过自适应孤岛控制单元实现自动切换到不带内环电流控制，因不存在采样控制等延时造成的负阻，能够使系统稳定，避免了因闭环控制引入负阻分量造成的中高频振荡问题，为大规模新能源接入提供更优选方案。
应当理解的是，以上的一般描述和后文的细节描述仅是示例性的，并不能限制本申请。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，还可以根据这些附图获得其他的附图，而并不超出本申请要求保护的范围。
图1示出根据本申请示例实施例的一种柔性直流输电系统示意图。
图2示出根据本申请示例实施例的柔性直流输电系统孤岛运行的控制方法流程示意图。
图3示出根据本申请示例实施例的开环控制方式流程示意图。
图4示出根据本申请第一示例实施例的双闭环控制方式示意图。
图5示出根据本申请第二示例实施例的双闭环控制方式示意图。
图6示出根据本申请另一示例实施例的柔性直流输电系统连接新能源或者无源系统组成示意图。
图7示出根据本申请示例实施例的自适应孤岛控制方式流程图。
图8示出根据本申请实施例的一种柔性直流输电系统孤岛运行的控制系统示意图。
图9示出根据本申请实施例的自适应控制单元的结构示意图。
图10示出根据本申请实施例的一种用于柔性直流输电系统孤岛运行控制的电子设备框图。
具体实施方式
现在将参考附图更全面地描述示例实施例。然而，示例实施例能够以多种形式实施，且不应被理解为限于在此阐述的实施例；相反，提供这些实施例使得本申请将全面和完整，并将示例实施例的构思全面地传达给本领域的技术人员。在图中相同的附图标记表示相同或类似的部分，因而将省略对它们的重复描述。
所描述的特征、结构或特性可以以任何合适的方式结合在一个或更多实施例中。在下面的描述中，提供许多具体细节从而给出对本公开的实施例的充分理解。然而，本领域技术人 员将意识到，可以实践本公开的技术方案而没有这些特定细节中的一个或更多，或者可以采用其它的方式、组元、材料、装置等。在这些情况下，将不详细示出或描述公知结构、方法、装置、实现步骤、材料或者操作。
此外，术语“包括”和“具有”以及它们任何变形，意图在于覆盖不排他的包含。例如包含了一系列步骤或单元的过程、方法、系统、产品或设备没有限定于已列出的步骤或单元，而是可选地还包括没有列出的步骤或单元，或可选地还包括对于这些过程、方法、产品或设备固有的其他步骤或单元。
本申请的说明书和权利要求书及上述附图中的术语“第一”、“第二”等是用于区别不同对象，而不是用于描述特定顺序。此外，术语“包括”和“具有”以及它们任何变形，意图在于覆盖不排他的包含。
图1示出根据本申请示例实施例的一种柔性直流输电系统示意图。
如图1所示，柔性直流输电系统包括交流系统、换流器、联接变压器3、新能源1和直流场设备4。联接变压器3的一次侧通过进线开关2接入新能源1，联接变压器3的二次侧接入换流器及直流场设备4，换流器及直流场设备4通过直流线路5接入对站的换流器及直流场设备6，对站的换流器及直流场设备6通过对站的联接变压器7经对站的一次侧开关8实现与交流电电网或电源9连接。
图2示出根据本申请示例实施例的柔性直流输电系统孤岛运行的控制方法流程示意图。
在S10中，柔性直流输电系统孤岛运行时，在启动状,态换流器以开环控制方式实现启动和稳态运行。
柔性直流输电系统孤岛运行时，带负载运行或不带负载运行。
柔性直流输电系统以孤岛模式解锁后，采用开环控制方式启动，如图3所示，预设换流器网侧交流电压d轴分量U d *、预设换流器网侧交流电压d轴分量U q *、和预设频率参考值f ref *作为开环控制器的输入，经过开环控制器的PI调节后输出恒定的换流器交流电压参考波，vd＝U d *，vq＝0，实现换流器的交流侧电流波形和相位的控制。
柔性直流输电系统孤岛启动时采用开环控制模式，电压参考波从0kV开始，以kV/s速率上升至额定电压U NkV，建立稳定的交流电压后，柔性直流输电系统保持开环控制运行，为新能源系统或无源交流系统提供稳定的电压幅值和频率。
这样的启动方式，避免孤岛启动时的大扰动、大冲击，抑制输出电压和电流的 高频分量及畸变，保持系统的稳定运行。
在S20中，柔性直流输电系统孤岛运行时，在非故障状态,以开环控制方式实现所述换流器稳态运行或者以自适应孤岛控制方式运行。其中，开环控制方式与启动过程中的控制方式相同，此处不再赘述；自适应孤岛控制方式将在下文中详细介绍。
在S30中，当检测到柔性直流输电系统的交流系统故障时，换流器由开环控制方式转为双闭环控制方式来限制故障电流抑制干扰。
检测到交流系统故障，检测方式包括电压判据、电流判据、功率判据和频率判据。
根据电压判据，当系统电压U s<系统电压预设低值U s_setL或U s>系统电压预设高值U s_setH，或当直流电压U DC<直流电压预设低值U DC_setL或U DC>直流电压预设高值U DC_setH，或当交流阀侧零序电压U 0>交流阀侧零序电压阈值U 0_set时，系统由开环控制方式转为双闭环控制。
其中，系统电压预设低值U s_setL≤1pu，系统电压预设高值U s_setH≥1pu；直流电压预设低值U DC_setL≤1pu，直流电压预设高值U DC_setH≥1pu；交流阀侧零序电压阈值U 0_set≥0pu。其中，其中，pu为标幺值单位，此处的标幺值为实际值与额定值的相对值。
根据电流判据，当网侧电流I s>网侧电流阈值I s_set或桥臂电流I b>桥臂电流阈值I b_set时，系统由开环控制方式转为双闭环控制。
其中，网侧电流阈值I s_set≥1pu，桥臂电流阈值I b_set≥1pu。
根据功率判据，当有功功率P<有功功率阈值P _set.时，系统由开环控制方式转为双闭环控制。
其中，有功功率阈值P _set≤1pu。
根据频率判据，当系统频率f<系统频率预设低值f _setL或f>系统频率预设高值f _setH时，系统由开环控制方式转为双闭环控制。
系统频率预设低值f _setL<50Hz，系统频率预设高值f _setH>50Hz。
双闭环控制方式包括外环控制和内环控制，如图4所示。
外环控制中，输入换流器网侧交流电压U d和预设换流器网侧交流电压d轴分量U d *，差值输入比例积分控制器PI，经过比例积分控制器，输出内环有功电流参考值。输入换流器网侧交流电压U q和预设换流器网侧交流电压q轴分量U q *，差值输入比例积分控制器PI，经过比例积分控制器，输出内环无功电流参考值。
内环控制中，接收来自外环控制的内环有功电流参考值、内环无功电流参考值，并快速跟踪内环有功电流参考值、内环无功电流参考值以及预设频率参考值f ref *，实现换流器的交流侧电流波形和相位的直接控制。
双闭环控制方式中，外环控制输出电压幅值和频率，内环控制电流。
其中，控制模式选择中，打到A，就是开环控制模式，打到B，就是双闭环控制模式。
可选地，为满足故障状态下电流不越限的需求，双闭环控制方式还包括限流环节Idmax，控制交流系统的故障电流不越限，如图5所示。限流环节设置在外环控制与内环控制的通道间，避免故障时柔性直流输电系统由于过流导致的跳闸。
可选地，由开环控制方式转为双闭环控制方式时，给外环控制的积分器的输入赋初值，初值为故障前正常运行时积分器积分值的-2倍到2倍，但并不以此为限，使积分器立刻退出饱和状态。以避免由于闭环控制的积分器退饱和过程导致的控制失效以及系统失稳的情况。
孤岛开环方式运行能够避免连接变压器或短的空载线路引起的高频振荡；故障时系统由开环方式转为双闭环控制方式，有效抑制故障过流。控制切换过程中，通过给外环控制的积分器的输入赋初值，避免了闭环控制的积分器退饱和过程导致的控制失效以及系统失稳的情况。
图6示出根据本申请另一示例实施例的柔性直流输电系统(例如，柔性直流输电换流站)连接新能源或者无源系统组成示意图。
以连接大型风电场为例，如图6所示，根据实施例，柔性直流输电换流站连接海上风电新能源系统1000通常包括交流升压站1001、海上柔性直流输电换流站2001(以下简称海上换流站)和陆上换流站3001。海上风电场产生的电能经过交流升压站1001升压接入海上换流站2001。经过海上换流站2001输出直流电，并经过海缆4000接入陆上换流站3001，从而实现风电场功率由海上向陆上交流电网5000的传输。
继续参见图6，海上换流站2001通常包括：交流母线2100、站用变压器2200、联接变压器2300、阀侧母线2400、阀侧开关(图中未示)、换流阀及直流场设备2600以及相应的测量或控制设备。换流阀及直流场设备2600通常包括换流阀、桥臂电抗器、直流场设备等。
根据实施例，在输电过程中，海上风电场产生的风电能经过升压后接入海上换流站2001的交流母线2100。交流母线2100通过两组并联的联接变压器2300接入阀侧母线2400。阀侧母线2400与换流阀及直流场设备2600的交流侧连接。海上换流站2001通过高压站用电变压 器2200为海上换流站的其他设备供电。整个控制过程中，海上换流站通过孤岛控制产生稳定的交流电压供海上风电新能源并网。
图7示出根据本申请示例实施例的自适应孤岛控制方式流程图。
参见图7，根据实施例，在S101，采集柔性直流输电系统交流侧的三相电压和三相电流经过abc/dq坐标系转换为dq轴下电压信号和dq轴下电流信号。
在S103，根据接收到电压设定参考值、频率设定参考值、所述dq轴下电压信号和电流信号、柔性直流输电系统交流侧的三相电压信号和三相电流信号通过选择控制模式，产生自适应孤岛控制桥臂参考波。
根据实施例，选择控制模式，包括选择带内环电流控制的孤岛控制模式，或者选择不带内环电流控制的孤岛控制模式，两种模式具体的切换过程将结合图9进行详细描述。
图8示出根据本申请实施例的一种柔性直流输电系统孤岛运行的控制系统示意图。
如图7和图8所示，根据示例实施例，本申请提供的用于柔性直流输电换流站的自适应孤岛控制方法包括：
在S101采集柔性直流输电系统交流侧的三相电压和三相电流经过abc/dq坐标系转换为dq轴下电压信号和dq轴下电流信号。
在S103根据接收到电压设定参考值、频率设定参考值值、dq轴下电压信号和电流信号、反映柔直运行状态的三相电压信号和三相电流信号通过选择控制模式，产生自适应孤岛控制桥臂参考波。
根据实施例，选择控制模式，包括选择带内环电流控制的孤岛控制模式，或者选择不带内环电流控制的孤岛控制模式。具体选择如前述控制模式的实施例，将在后面结合图9说明。下面将结合图8说明控制系统的具体结构。
参见图8用于柔性直流输电换流站的自适应孤岛控制系统2000包括采集转换单元100和自适应孤岛控制单元200。
采集转换单元100用于将采集到的柔性直流输电系统交流侧的三相电压和三相电流经过abc/dq坐标系转换为dq轴下电压信号和dq轴下电流信号。
自适应孤岛控制单元200用于根据接收到电压设定参考值、dq轴下电压信号和电流信号、反映柔直运行状态的三相电压信号和三相电流信号经过自适应孤岛控制单元，产生自适应孤岛控制桥臂参考波。
根据实施例，采集转换单元100包括第一输入端101、第二输入端102、第三输入端103、第一输出端111、第二输出端112。
第一输入端101用于接收柔性直流输电系统交流侧的三相电压信号。
第二输入端102用于接收柔性直流输电系统交流侧的三相电流信号。
第三输入端103用于接收同步的相位角信号。
第一输出端111用于输出反映柔性直流运行状态的电压信号。
第二输出端112用于输出反映柔性直流运行状态的电流信号。
根据实施例，自适应孤岛控制单元102包括第一输入端201、第二输入端202、第三输入端203、第四输入端204、第五输入端211、第六输入端212、第一输出端261、第二输出端262、第三输出端263、第四输出端264、第五输出端265、第六输出端266、第七输出端267。
第一输入端201用于接收电压设定参考值。
第二输入端202用于将接收到频率设定参考值产生同步的相位角信号给的采集转换单元第三输入端及自身产生参考波。
第三输入端203用于接收反映柔性直流运行状态的电压信号。
第四输入端204用于接收反映柔性直流运行状态的电流信号。
第五输入端211用于接收dq轴下电压信号。
第六输入端212用于接收dq轴下电流信号。
第一输出端261、第二输出端262、第三输出端263、第四输出端264、第五输出端265、第六输出端266分别输出自适应孤岛控制单元的三相上桥臂和三相下桥臂参考波。
第七输出端267用于输出同步的相位角信号。
根据实施例，参照图2，采集转换单元的第一输出端111连接自适应孤岛控制单元的第五输入端211，采集转换单元的第二输出端112连接自适应孤岛控制单元的第六输入端212，自适应孤岛控制单元第七输出端267连接采集转换单元的第三输入端103。
采集转换单元100用于根据接收的位角信号将采集到的柔性直流交流侧三相电压和三相电流经过abc/dq转换为dq轴下电压Udq和电流Idq，柔直交流侧三相电压、三相电流分别经过采集转换单元的第一输入端101、第二输入端102到达采集转换单元100；采集转换单元100第三输入端103采集自适应孤岛控制单元200的第七输出端267送入的相位角信号。
根据实施例，可选地，采集转换单元100的第一输出端101和第二输出端102能够合并成一个输出端送到自适应孤岛控制单元200，相应地，自适应孤岛控制单元200的第五输入端211和第六输入212端能够合并为一个输入端接收采集转换单元100输出的信号。
可选地，自适应孤岛控制单元200的第三输入端203和第四输入端204也能够合并到第五输入端211和第六输入端212，省去第三203和第四输入端204，由采集单元100的第一输出端101和第二输出端102输出三相电压信号和三相电流信号直接发送到自适应孤岛控制单元200的第五输入端 211和第六输入端212。
自适应孤岛控制单元200用于根据接收到电压设定参考值
Figure PCTCN2022072571-appb-000002
和dq轴下电压Udq和电流Idq根据反映柔直运行状态的三相电压和电流经过自适应孤岛控制，产生自适应孤岛控制桥臂参考波。自适应孤岛控制单元200根据接收到频率设定参考值f_ref产生相位角信号θ给的采集转换单元100和自身产生参考波使用。的电压设定参考值
Figure PCTCN2022072571-appb-000003
频率设定参考值f_ref、dq轴电压Udq和dq轴电流Idq分别经自适应控制单元的第一输入端201、第二输入端202、第五输入端211和第六输入端212送达自适应孤岛控制单元200；反映柔性直流运行状态的三相电压和三相电流信号分别经自适应控制单元的第三输入端203和第四输入端204送达自适应孤岛控制200，孤岛控制单元的第一输出端261、第二输出端262、第三输出端263、第四输出端264、第五输出端265、第六输出端266分别输出柔性直流三相上桥臂和三相下桥臂参考波传送到柔性直流阀控系统(图未示出)，孤岛控制单元的第七输出端267输出相位角信号θ到采集转换单元第三输入端103。
图9示出根据本申请实施例的自适应孤岛控制单元200的结构示意图。
如图9所示，根据示例实施例，本申请提供的自适应孤岛控制单元200包括带内环电流控制的孤岛控制模块210、不带内环电流控制的孤岛控制模块220、频率相位控制模块230、自适应孤岛控制选择模块240、参考波生成模块250。
带内环电流控制的孤岛控制模块210用于产生dq轴闭环电压参考波。
不带内环电流控制的孤岛控制模块220用于产生dq轴开环电压参考波。
频率相位控制模块230用于产生同步相位信号供采集转换单元的abc/dq坐标系转换及参考波生成模块dq/abc坐标系转换使用。
自适应孤岛控制选择模块240用于选择带内环电流控制的孤岛控制模块或者不带内环电流控制的孤岛控制模块。
参考波生成模块250用于接收频率相位控制模块的同步相位信号转换dq/abc坐标系，以及产生六个桥臂参考波。
根据实施例，带内环电流控制的孤岛控制模块210包括第一输入端213、第二输入端214、第三输出端215和第一输出端217。
第一输入端213用于接收电压设定参考值。
第二输入端214用于接收dq轴下电压信号。
第三输入端215用于接收dq轴下电流信号。
第一输出端217用于输出dq轴闭环电压参考波。
根据实施例，不带内环电流控制的孤岛控制模块220包括第一输入端221、第二输入端222和 第一输出端226。
第一输入端221，用于接收电压设定参考值。
第二输入端222，用于接收dq轴下电压信号。
第一输出端226，用于输出dq轴开环电压参考波。
根据实施例，自适应孤岛控制选择模块包括第一输入端241、第二输入端242、第三输入端243、第四输入端244和第一输出端246。
第一输入端241用于接收反映柔性直流运行状态的电压信号。
第二输入端242用于接收反映柔性直流运行状态的电流信号。
第三输入端243用于接收dq轴闭环电压参考波。
第四输入端244用于接收dq轴开环电压参考波。
第一输出端246用于输出自适应输入参考波电压。
根据实施例，带内环电流控制的孤岛控制模块210第一输出端217连接自适应孤岛控制选择模块240的第三输入端243；不带内环电流控制的孤岛控制模块220第一输出端226连接自适应孤岛控制选择模块240的第四输入端244；频率相位控制模块230的输出端232连接参考波生成模块的第二输入端252；自适应孤岛控制选择模块240的第一输出端246连接参考波生成模块的第一输入端251。
根据实施例，带内环电流控制的孤岛控制模块210用于根据接收到电压设定参考值
Figure PCTCN2022072571-appb-000004
和dq轴电压Udq经过外环电压控制器产生电流参考波Idq_ref，电流参考波Idq_ref在与dq轴电流Idq经过内环电流控制器产生带电流闭环控制的dq轴闭环电压参考波Udq_ref_cl送入自适应孤岛控制选择模块的第三输入端243；其中电压设定参考值
Figure PCTCN2022072571-appb-000005
dq轴电压Udq和dq轴电流Idq送入带内环电流控制的孤岛控制模块的第一输入端213、第二输入端214和第三输入端215。
根据实施例，不带内环电流控制的孤岛控制模块220用于根据接收到电压设定参考值
Figure PCTCN2022072571-appb-000006
和dq轴电压Udq经过外环电压控制产生不带电流闭环控制的dq轴开环电压参考波Udq_ref_op送入自适应孤岛控制选择模块240的第四输入端244；其中电压设定参考值
Figure PCTCN2022072571-appb-000007
和dq轴电压Udq送入不带内环电流控制的孤岛控制模块的第一输入端221和第二输入端222。
频率相位控制模块230用于根据接收到频率设定参考值f_ref产生同步相位信号供采集转换模块abc/dq转换和参考波生成模块dq/abc转换使用。频率设定参考值f_ref接入频率相位控制模块第一输入端231。频率相位控制模块第一输出端232接入参考波生成模块第三输入端252。
自适应孤岛控制选择模块240用于根据柔直运行状态自适应选择带电流闭环控制的dq轴闭环电 压参考波Udq_ref_cl或不带电流闭环控制的dq轴开环电压参考波Udq_ref_op，柔性直流运行状态由三相电压和三相电流或者三相电压与三相电流综合量进行自适应判断选择。柔性直流运行状态由三相电压和三相电流接入自适应孤岛控制选择模块的第一输入端241和第二输入端242。带电流闭环控制的dq轴闭环电压参考波Udq_ref_cl或不带电流闭环控制的dq轴开环电压参考波Udq_ref_op分别送入到自适应孤岛控制选择模块的第三输入端243和第四输入端244。根据柔直运行状态自适应判断后选择的自适应输入参考波送到自适应孤岛控制选择模块的输出端246。
参考波生成模块250用于根据自适应孤岛控制选择模块输出的dq电压参考波和频率相位控制的同步相位信号，经dq/abc转换到abc坐标下然后生成阀控所需要的六个桥臂参考波。自适应孤岛控制选择模块的输出dq轴参考电压送入参考波生成模块的第一输入端251，生成的六个桥臂参考波分别送达参考波生成模块的第一输出端254到第六输出端259。
反映柔直运行状态的三相电压Ux(x＝a,b,c)可以是柔直连接的交流电压，三相电流Ix(x＝a,b,c)可以是交流电流、阀侧电流或桥臂电流，运行状态也可以是交流电压和电流相乘得到系统功率P，P＝3Ux*Ix，根据三相电压、三相电流或者有功功率自适应判断柔直运行状态自适应选择模块选择带电流闭环控制的dq轴闭环电压参考波Udq_ref_cl或不带电流闭环控制的dq轴开环电压参考波Udq_ref_op的选择判据如下：
根据实施例，在柔性直流启动解锁和空载状态下，当满足系统功率P<Pset1或者电流峰值Ipeak<Iset1或者
Figure PCTCN2022072571-appb-000008
时，选择运行不带内环电流控制的孤岛控制模块220，否则将自动切换到采用带内环电流的孤岛模块210，另Pset1≤0.1pu，Iset1≤0.1pu。
已处于带内环电流控制模块210的控制下，当检测到柔直系统电压谐波含量Us_h>Us_hset或者电流谐波含量I_h>Iv_hset,自动切换到不带内环电流控制模块的孤岛控制系统，Us_hset≥0.01pu，Iv_hset≥0.01pu。
已处于不带内环电流控制模块控制下，当检测到网侧电流零序电压U0>U0_set或网侧电流Is>Is_set或桥臂电流Ib>Ib_set时，自动切换到带内环电流控制控制模块，U0_set≥0.05pu，Is_set≥1.15pu，Ib_set≥1.15pu。
上述的dq轴电压Udq、dq轴电流Idq、
Figure PCTCN2022072571-appb-000009
指令值、Udq_ref_cl、Udq_ref_op、代表正序分量和负序分量共四个分量。
参考波生成模块250的输入端251和252分别接收到dq轴自适应输入参考波和同步相位角信号后，经dq/abc转换后为正负序叠加产生三相电压Ux_ref(a,b,c),然后经过信号转换Vxu_ref＝Udc/2-Ux_ref(x＝a,b,c)和Vx_dref＝Udc/2-Ux_ref分别产生六个桥臂参考波,式中Udc为直流电压设定参考值。
的带内环电流控制的孤岛控制模块和不带内环电流控制的孤岛控制模块中的电压外环控制与电流环控制器，可以是PI控制器，也可以是PR控制器。
图10示出示出根据本申请实施例的一种用于柔性直流输电系统孤岛运行控制的电子设备框图。
如图10所示，电子设备400以通用计算设备的形式表现。电子设备400的组件可以包括但不限于：至少一个处理单元410、至少一个存储单元420、连接不同系统组件(包括存储单元420和处理单元410)的总线430、显示单元440等。
其中，存储单元存储有程序代码，程序代码可以被处理单元410执行，使得处理单元410执行本说明书描述的根据本申请各种示例性实施方式的控制方法。
总线430可以为表示几类总线结构中的一种或多种，包括存储单元总线或者存储单元控制器、外围总线、图形加速端口、处理单元或者使用多种总线结构中的任意总线结构的局域总线。
电子设备400也可以与一个或多个外部设备500(例如键盘、指向设备、蓝牙设备等)通信，还可与一个或者多个使得用户能与该电子设备400交互的设备通信，和/或与使得该电子设备400能与一个或多个其它计算设备进行通信的任何设备(例如路由器、调制解调器等等)通信。这种通信可以通过输入/输出(I/O)接口450进行。并且，电子设备400还可以通过网络适配器460与一个或者多个网络(例如局域网(LAN)，广域网(WAN)和/或公共网络，例如因特网)通信。网络适配器460可以通过总线430与电子设备400的其它模块通信。应当明白，尽管图中未示出，可以结合电子设备400使用其它硬件和/或软件模块，包括但不限于：微代码、设备驱动器、冗余处理单元、外部磁盘驱动阵列、RAID系统、磁带驱动器以及数据备份存储系统等。
本申请柔性直流输电系统孤岛运行的自适应孤岛控制方式，使得连接新能源的柔直换流站控制系统根据柔性直流输电系统运行状态，自适应地选择采用带内环电流控制模式或者不带内环电流控制模式的自适应孤岛控制方法，通过自动切换到不带内环电流控制，因不存在采样控制等延时造成的负阻，能够使系统稳定，避免了因闭环控制引入负阻分量造成的中高频振荡问题，从而避免中高频振荡风险，也实现了故障状态下故障电流可控。
以上对本申请实施例进行了详细介绍，本文中应用了具体个例对本申请的原理及实施方式进行了阐述，以上实施例的说明仅用于帮助理解本申请的方法及其核心思想。同时，本领域技术人员依据本申请的思想，基于本申请的具体实施方式及应用范围上做出的改变或变形之处，都属于本申请保护的范围。综上所述，本说明书内容不应理解为对本申请的限制。

Claims (20)

  1. 一种用于柔性直流输电系统孤岛运行的控制方法，所述柔性直流输电系统连接交流系统，所述柔性直流输电系统包括换流器，其特征在于，包括：
    所述柔性直流输电系统孤岛运行时，在启动状态以开环控制方式实现所述换流器启动和稳态运行；
    当检测到所述交流系统故障时，所述换流器由所述开环控制方式转为双闭环控制方式来限制故障电流抑制干扰；
    在非故障状态，以自适应孤岛控制方式运行；或
    在非故障状态，以开环控制方式实现所述换流器稳态运行。
  2. 根据权利要求1所述的控制方法，其特征在于，所述自适应孤岛控制方式包括：
    采集所述柔性直流输电系统交流侧的三相电压和三相电流经过abc/dq坐标系转换为dq轴下电压信号和dq轴下电流信号；
    根据接收到电压设定参考值、频率设定参考值、所述dq轴下电压信号和电流信号、所述柔性直流输电系统交流侧的三相电压信号和三相电流信号通过选择控制模式，产生自适应孤岛控制桥臂参考波。
  3. 根据权利要求2所述的控制方法，其特征在于，所述选择控制模式，包括：
    选择带内环电流控制的孤岛控制模式，或者选择不带内环电流控制的孤岛控制模式。
  4. 根据权利要求3所述的控制方法，其特征在于，所述选择带内环电流控制的孤岛控制模式，或者选择不带内环电流控制的孤岛控制模式，包括：
    在启动解锁和空载状态下，当满足系统功率P<Pset1或者电流峰值I peak<Iset1或者
    Figure PCTCN2022072571-appb-100001
    时，选择运行不带内环电流控制的孤岛控制模式；
    否则将自动切换到采用带内环电流的孤岛模式，
    其中，所述P set1≤0.1pu，I set1≤0.1pu。
  5. 根据权利要求3所述的控制方法，其特征在于，所述选择带内环电流控制的孤岛控制模式， 或者选择不带内环电流控制的孤岛控制模式，还包括：
    已处于带内环电流控制模块的控制模式下，当检测到网侧电压谐波含量Us_h>Us_hset或者电流谐波含量I_h>Iv_hset时，则自动切换到不带内环电流控制模块的孤岛控制模式，
    其中，所述Us_hset≥0.01pu，Iv_hset≥0.01pu。
  6. 根据权利要求3所述的控制方法，其特征在于，所述选择带内环电流控制的孤岛控制模式，或者不带内环电流控制的孤岛控制模式，还包括：
    已处于不带内环电流控制模块控制下，当检测到网侧零序电压U 0>U 0_set或网侧电流Is>Is_set或桥臂电流I b>I b_set时，则自动切换到带内环电流控制控制模块，
    其中，所述U 0_set≥0.05pu，Is_set≥1.15pu，I b_set≥1.15pu。
  7. 根据权利要求1所述的控制方法，其中，所述开环控制模式包括：
    预设换流器网侧交流电压和预设频率参考值作为开环控制器的输入，经过所述开环控制器的调节后输出恒定的换流器交流电压参考波，实现所述换流器的交流侧电流波形和相位的控制。
  8. 根据权利要求1所述的控制方法，其中，所述双闭环控制方式包括：
    外环控制，输入换流器网侧交流电压和频率，经过比例积分控制器，输出内环有功电流参考值和内环无功电流参考值；
    内环控制，接收来自所述外环控制输出的内环有功电流参考值、内环无功电流参考值，并快速跟踪所述内环有功电流参考值、内环无功电流参考值，实现换流器的交流侧电流波形和相位的直接控制。
  9. 根据权利要求1所述的控制方法，其中，所述双闭环控制方式还包括：
    限流环节，控制所述交流系统的故障电流不越限。
  10. 根据权利要求1所述的控制方法，其中，所述由所述开环控制方式转为双闭环控制方式时，给外环控制的积分器的输入赋初值。
  11. 根据权利要求1所述的控制方法，其中，所述检测到所述交流系统故障，监测方式包括：
    根据电压判据，当系统电压Us<系统电压预设低值Us_setL或Us>系统电压预设高值Us_setH， 或当直流电压UDC<直流电压预设低值UDC_setL或UDC>直流电压预设高值UDC_setH，或当交流阀侧零序电压U0>交流阀侧零序电压阈值U0_set时，系统由开环控制方式转为双闭环控制；
    根据电流判据，当网侧电流Is>网侧电流阈值Is_set或桥臂电流Ib>桥臂电流阈值Ib_set时，系统由开环控制方式转为双闭环控制；
    根据功率判据，当有功功率P<有功功率阈值P_set.时，系统由开环控制方式转为双闭环控制；
    根据频率判据，当系统频率f<系统频率预设低值f_setL或f>系统频率预设高值f_setH时，系统由开环控制方式转为双闭环控制。
  12. 根据权利要求11所述的控制方法，其中，所述系统电压预设低值Us_setL≤1pu，系统电压预设高值Us_setH≥1pu；直流电压预设低值UDC_setL≤1pu，直流电压预设高值UDC_setH≥1pu；交流阀侧零序电压阈值U0_set≥0pu，网侧电流阈值Is_set≥1pu，桥臂电流阈值Ib_set≥1pu，有功功率阈值P_set≤1pu，系统频率预设低值f_setL<50Hz，系统频率预设高值f_setH>50Hz，其中，pu为标幺值单位，所述标幺值为实际值与额定值的相对值。
  13. 根据权利要求1所述的控制方法，其中，所述柔性直流输电系统孤岛运行时，带负载运行或不带负载运行。
  14. 一种用于柔性直流输电系孤岛运行的控制系统，其特征在于，包括：
    采集转换单元，用于将采集到的所述柔性直流输电系统交流侧的三相电压和三相电流经过abc/dq坐标系转换为dq轴下电压信号和dq轴下电流信号；
    自适应孤岛控制单元，用于根据接收到电压设定参考值、频率设定参考值、所述dq轴下电压信号和电流信号、所述所述柔性直流输电系统交流侧的三相电压信号和三相电流信号经过所述自适应孤岛控制单元，产生自适应孤岛控制桥臂参考波。
  15. 根据权利要求14所述的控制系统，其特征在于，所述的自适应孤岛控制单元，包括：
    带内环电流控制的孤岛控制模块，用于产生dq轴闭环电压参考波；
    不带内环电流控制的孤岛控制模块，用于产生dq轴开环电压参考波；
    频率相位控制模块，用于产生同步相位信号供所述采集转换单元的abc/dq坐标系转换及参考波生成模块dq/abc坐标系转换使用；
    自适应孤岛控制选择模块，用于选择带内环电流控制的孤岛控制模块或者不带内环电流控制的 孤岛控制模块；
    参考波生成模块，用于接收所述频率相位控制模块的同步相位信号转换dq/abc坐标系，以及产生六个桥臂参考波。
  16. 根据权利要求15所述的控制系统，其特征在于，所述带内环电流控制的孤岛控制模块，包括：
    将接收所述电压设定参考值、所述dq轴下电压信号和所述dq轴下电流信号转化成dq轴闭环电压参考波的输出信号。
  17. 根据权利要求15所述的控制系统，其特征在于，所述不带内环电流控制的孤岛控制模块，包括：
    将所述电压设定参考值和所述dq轴下电压信号转化为dq轴开环电压参考波的输出信号。
  18. 根据权利要求15至17中任一所述的控制系统，其特征在于，所述自适应孤岛控制选择模块，包括：
    将所述柔性直流输电系统交流侧的三相电压信号和三相电流信号、所述dq轴闭环电压参考波、所述dq轴开环电压参考波转化成自适应输入参考波电压的输出信号。
  19. 根据权利要求15所述的控制系统，其特征在于，所述带内环电流控制的孤岛控制模块和所述不带内环电流控制的孤岛控制模块两者中的电压外环控制器和电流环控制器，包括PI控制器和/或PR控制器。
  20. 一种电子设备，其特征在于，包括：
    一个或多个处理器；
    存储装置，用于存储一个或多个程序；
    当所述一个或多个程序被所述一个或多个处理器执行，使得一个或多个处理器实现根据权利要求1-13中任一所述的控制方法。
PCT/CN2022/072571 2021-01-19 2022-01-18 用于柔性直流输电系统孤岛运行的控制方法及控制系统 WO2022156681A1 (zh)

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