CN114069704A - Grid-connected operation control method of medium-voltage power supply quality comprehensive improving device - Google Patents

Grid-connected operation control method of medium-voltage power supply quality comprehensive improving device Download PDF

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CN114069704A
CN114069704A CN202111395326.5A CN202111395326A CN114069704A CN 114069704 A CN114069704 A CN 114069704A CN 202111395326 A CN202111395326 A CN 202111395326A CN 114069704 A CN114069704 A CN 114069704A
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converter
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axis component
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CN114069704B (en
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韩鸣宇
左文平
周猛
黄斌
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Grameer Technology Wuhan Co ltd
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381Dispersed generators
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18Arrangements for adjusting, eliminating or compensating reactive power in networks
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30Reactive power compensation

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  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)
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Abstract

The invention belongs to the technical field of power transmission and distribution of a power system, and provides a grid-connected operation control method of a medium-voltage power supply quality comprehensive lifting device, which comprises three control loops of power, frequency and voltage. The invention realizes independent, rapid and effective control of the amplitude and the phase angle of the load voltage in the device, can realize comprehensive treatment of various power quality events, and meets the requirement of high power supply reliability of highly sensitive users on the load side.

Description

Grid-connected operation control method of medium-voltage power supply quality comprehensive improving device
Technical Field
The invention belongs to the technical field of power transmission and distribution of a power system, and particularly relates to a grid-connected operation control method of a medium-voltage power supply quality comprehensive improving device.
Background
Highly sensitive users, typically represented by microelectronics, biomedicine, precision manufacturing, data centers and the like, have the characteristics of high economic output value, strong demonstration effect and the like, and are important forces for serving national economic development. However, the electric equipment of the highly sensitive users also puts higher requirements on the quality of electric energy and the reliability of power supply, and the transient problem of the quality of electric energy can cause huge economic loss and serious social influence. Meanwhile, the rapid increase of high and new technology manufacturers in China also makes the development of power supply quality improvement technology and industrial requirements show the trend of single, dispersed, low-voltage to comprehensive, centralized and medium-high voltage evolution, the centralized and comprehensive improvement requirements of high-sensitive users on the power supply quality become stronger day by day, and the market scale is gradually enlarged. Therefore, the research and development significance of key technologies for the medium-voltage high-capacity power supply quality comprehensive improvement device is significant, and the key technologies become a hot problem concerned by the industry.
Although some mature technologies capable of improving the quality of electric energy on the power grid side exist in the market, such as an Active Power Filter (APF), a Static Var Compensator (SVC), a Static Var Generator (SVG) and a dynamic voltage compensator (DVR), wherein the APF is used for inhibiting power grid harmonics, the SVC and the SVG are used for compensating power grid reactive power, the drop and flicker of the power grid voltage are reduced, and the DVR is used for compensating the power grid voltage sag. The functions of the devices are single, so that multiple devices need to be put into the device simultaneously if comprehensive and effective treatment of multiple power quality problems is to be realized, which not only increases the cost of equipment, but also solves the problems of complex control strategy, weakened operation effect and the like caused by coupling among different devices.
In order to effectively solve the defects of the multiple device combined management scheme, a technical route for ensuring high-quality power supply at a load side in view of the power quality problem at a power grid side is widely concerned and researched. Based on a topological structure and a static converter of a diesel dynamic rotating uninterruptible power supply, an impedance isolation type UPS is provided in the document 'A new UPS topology for multi-megawatt medium voltage power protection' by an ABB company by Nick Elliott and Robert Turner, and higher working performance and efficiency are realized. However, the step-up transformer in the impedance isolation type UPS topology makes the occupied area of the equipment larger, and the larger value of the running current in the low-voltage side converter of the equipment also puts higher requirements on the design of the filter circuit and the controller. In addition, the impedance isolation type UPS of ABB achieves high voltage and large capacity by connecting the battery clusters in series and parallel, which makes troubleshooting of the equipment difficult and makes expansion of the capacity difficult.
A novel medium-voltage power supply quality comprehensive improvement device is provided in a patent of a medium-voltage power supply quality comprehensive regulation system (publication number CN112531711A), and the converter is directly hung on a medium-voltage power supply system by adopting a power unit cascade module mode, so that the defect of an impedance isolation type UPS of ABB company is effectively overcome, and the comprehensive effective treatment of various power quality events of a power grid is realized. Although the patent proposes the basic topology of the medium-voltage power supply quality comprehensive improving device, the research and the explanation of the control method of the power quality regulation when the device is in grid-connected operation are not carried out.
Disclosure of Invention
The invention aims to overcome the defects of the technology and provide a grid-connected operation control method of a medium-voltage power supply quality comprehensive improving device.
The object of the invention is achieved by the following technical measures.
A grid-connected operation control method of a medium-voltage power supply quality comprehensive lifting device comprises the following steps:
(1) and (3) power control:
(1-1) acquiring active power P injected into power grid in medium-voltage power supply quality comprehensive lifting deviceGThe load absorbs active power PLAnd the converter absorbs the active power instruction value PbatIn which P isbatThe charging power control device is used for controlling the charging power of an energy storage system in the medium-voltage power supply quality comprehensive lifting device;
(1-2) absorbing the active power P by the loadLAbsorbing active power instruction value P with converterbatAdding the obtained power to obtain the total absorption active power P of the load and the converterT
(1-3) injecting active power P into the power gridGWith the total absorbed active power P of the load and the converterTObtaining an actual active power difference value delta P by difference;
(1-4) inputting the actual active power difference value delta P into a controller A to obtain a phase angle difference theoretical reference value delta of the power grid voltage and the load voltageref1Theoretical reference value delta of phase angle difference between grid voltage and load voltageref1Obtaining a phase angle difference reference value delta between the power grid voltage and the load voltage through an amplitude limiting linkref(ii) a Wherein the controller A is a proportional controller, a proportional-integral-derivative controller, a proportional resonant controller, a dead-beat controller or a hysteresis controller;
(2) frequency control:
(2-1) acquiring the actual value delta of the phase angle difference between the grid voltage and the load voltage and the grid voltage angular frequency w in the medium-voltage power supply quality comprehensive improving deviceG
(2-2) phase angle difference reference value delta of grid voltage and load voltage output by power control looprefObtaining a phase angle difference actual difference value delta by subtracting the actual phase angle difference value delta of the power grid voltage and the load voltage;
(2-3) inputting the actual phase angle difference value delta into the controller B to obtain the angular frequency deviation reference value delta w of the load voltage and the power grid voltagerefWherein, the controller B is a proportional controller, a proportional-integral-derivative controller, a proportional resonant controller, a dead-beat controller or a hysteresis controller;
(2-4) deviation of angular frequency of load voltage from grid voltage by reference value Δ wrefWith the grid voltage angular frequency wGAfter addition, a load voltage angle is obtained through an angular frequency amplitude limiting linkFrequency reference value wrefThen w isrefInputting the reference value to an integral controller to obtain a load voltage phase angle reference value thetaref
(3) Voltage control:
(3-1) double-ring control of a voltage outer ring and a current inner ring is adopted, and load three-phase voltage U in the device is adopted in real timeLAnd the converter outputs three-phase current IC
(3-2) applying three-phase voltage U to the load respectivelyLThe converter outputs three-phase current ICPerforming park transformation, wherein the park transformation converts the rotation angle into the reference value theta of the phase angle of the load voltagerefTo obtain the three-phase voltage U of the loadLD-axis component U ofLdAnd q-axis component ULqThe converter outputs three-phase current ICD-axis component I ofCdAnd q-axis component ICq
(3-3) reference value U of d-axis component of three-phase voltage of loadLdrefThree-phase voltage U with loadLD-axis component U ofLdThe difference is input into a controller C to obtain a converter output three-phase current d-axis component reference value I generated by a voltage outer ringCdref1Wherein, the controller C is a proportional controller, a proportional-integral-derivative controller, a proportional resonant controller, a dead-beat controller or a hysteresis controller;
(3-4) reference value U of q-axis component of three-phase voltage of loadLqrefThree-phase voltage U with loadLQ-axis component U ofLqThe difference is input into a controller D to obtain a converter output three-phase current q-axis component reference value I generated by a voltage outer ringCqref1Wherein, the controller D is a proportional controller, a proportional-integral-derivative controller, a proportional resonant controller, a dead-beat controller or a hysteresis controller;
(3-5) outputting the reference value I of the three-phase current d-axis component by the converter generated by the voltage outer loopCdref1D-axis component I of feed-forward current of converterCdref2D-axis component I of grid voltage compensation currentCdref3Adding to obtain a theoretical reference value I of d-axis components of three-phase current output by the converterCdref4
(3-6) outputting the reference value I of the three-phase current q-axis component by the converter generated by the voltage outer loopCqref1Feed-forward current q-axis component I of converterCqref2Q-axis component I of grid voltage compensating currentCqref3Adding to obtain a theoretical reference value I of q-axis components of three-phase current output by the converterCqref4
(3-7) outputting the theoretical reference value I of the three-phase current d-axis and q-axis components by the converterCdref4And ICqref4Adding the three phases of the threeCdrefAnd ICqref
(3-8) outputting a three-phase current d-axis component reference value I by the converterCdrefAnd the converter outputs three-phase current ICD-axis component I ofCdThe difference is input into a controller E to obtain the output three-phase voltage U of the d-axis current tracking converterCD-axis component reference value UCdref1Wherein, the controller E is a proportional controller, a proportional-integral-derivative controller, a proportional resonant controller, a dead-beat controller or a hysteresis controller;
(3-9) outputting the reference value I of the three-phase current q-axis component by the converterCqrefAnd the converter outputs three-phase current ICQ-axis component I ofCqThe difference is input into a controller F to obtain the output three-phase voltage U of the q-axis current tracking converterCQ-axis component reference value U ofCqref1Wherein, the controller F is a proportional controller, a proportional-integral-derivative controller, a proportional resonant controller, a dead-beat controller or a hysteresis controller;
(3-10) applying three-phase voltage U to the loadLD-axis component U ofLdD-axis current tracking converter output three-phase voltage UCD-axis component reference value UCdref1The converter outputs a three-phase current q-axis component ICqD-axis voltage feed forward value of-wLICqAdding to obtain the output three-phase voltage U of the converterCD-axis component theoretical reference value UCdref2
(3-11) applying a load of threePhase voltage ULQ-axis component U ofLqOutput three-phase voltage U of q-axis current tracking converterCQ-axis component reference value U ofCqref1D-axis component I of three-phase current output by current transformerCdQ-axis voltage feed forward value wLICdAdding to obtain the output three-phase voltage U of the converterCQ-axis component theoretical reference value UCqref2
(3-12) outputting three-phase voltage U by the converterCD-axis and q-axis component theoretical reference value UCdref2And UCqref2The three-phase voltage U output by the converter is obtained after being input into the voltage amplitude limiting controllerCReference value U of d-axis and q-axis componentsCdrefAnd UCqref
(3-13) outputting three-phase voltage U to the converterCReference value U of d-axis and q-axis componentsCdrefAnd UCqrefObtaining the output three-phase voltage U of the converter by inverse Pack transformationCReference voltage U in abc static coordinate systemCa、UCbAnd UCc
In the technical scheme, the total absorption active power P of the load and the converter in the power controlTObtaining a Low-Pass filtering value P of the total absorbed active power of the load and the converter through a Low Pass Filter (LPF)LPFThen active power P is injected into the power gridGLow-pass filtering value P of active power absorbed by load and converterLPFAnd obtaining the actual difference value delta P of the active power by carrying out difference.
In the above technical solution, the phase angle difference limiting step in the power control includes an upper limit δmaxTo the lower limit deltaminUpper limit of δmaxTo the lower limit deltaminAll are obtained by phase angle difference limiters, wherein the phase angle difference upper limit deltamaxTaking the value deltamax1Upper phase angle difference limit delta defined by power transmissionmax2Of smaller value of deltamax1Equal to the actual phase angle difference delta plus 20 degrees, and the lower limit delta of the phase angle differenceminTaking the value deltamin1Lower phase angle difference limit delta from power transmission limitmin2Larger value of between, deltamin1Equal to the actual phase angle difference delta minus 20 degrees.
In the technical schemeIn the method, the angular frequency limiting link in the frequency control comprises an upper limit wmaxAnd a lower limit wminUpper limit of wmaxLimited upper limit w taking the value of instantaneous value of angular frequency wmax1With a defined upper limit w of the mean value within a fixed test time windowmax2Smaller value therebetween, lower limit wminLimited lower limit w taking the value of instantaneous value of angular frequency wmin1With a defined lower limit w of the mean value within a fixed test time windowmin2The larger value in between.
In the above technical solution, the reference value U of the d-axis component of the three-phase voltage of the load in the voltage controlLdrefThe voltage control circuit can follow the voltage amplitude of the power grid under the condition of meeting the power quality requirement of a load end, and the reference value U of the q-axis component of the three-phase voltage of the load in the voltage control circuitLqrefThe value is zero.
In the above technical solution, the converter feed-forward current d-axis component I in the voltage controlCdref2D-axis component I equal to three-phase current output by actual converterCdProportional coefficient KFFdThe product of (a), a converter feed-forward current q-axis component I in the voltage control loopCqref2Q-axis component I equal to three-phase current output by actual converterCqProportional coefficient KFFqThe product of (a).
In the above technical solution, the grid voltage compensation current d-axis component I in the voltage controlCdref3Equal to the rated effective value U of the network voltageGNWith the actual effective value U of the network voltageGIs multiplied by the scaling factor KGdA grid voltage compensation current q-axis component I in the voltage control loopCqref3Equal to the rated effective value U of the network voltageGNWith the actual effective value U of the network voltageGIs multiplied by the scaling factor KGq
In the above technical solution, the current limiting element in the voltage control includes an upper limit ICmaxWith a lower limit of ICminUpper limit ofCmaxWith a lower limit of ICminAre opposite numbers of each other, the absolute value being equal to IClim,IClimThe value is determined by the maximum allowable current of the converter.
In the above technical solution, the voltage limiting element in the voltage control includes an upper limit UCmaxAnd lower limit UCminUpper limit of UCmaxThe value is determined by the maximum allowable output voltage of the converter, and the lower limit UCminThe numerical value is not lower than zero, and can be adjusted according to the operation requirement of the device.
In general, by adopting the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
(1) the grid-connected operation control method of the medium-voltage power supply quality comprehensive improving device comprises three control loops of power, frequency and voltage, so that the independent, quick and effective control of the amplitude and the phase angle of the load voltage in the device is realized, the active power injected into a power grid can well track the active power of the load, and the requirement of adjusting the quality of the electric energy of the grid-connected operation of the device is met.
(2) The grid-connected operation control method of the medium-voltage power supply quality comprehensive improving device fully considers the influence of power grid voltage and power quality events and load sudden changes on the operation control effect of the device, a low-pass filter is added in a frequency control loop, and a current transformer feed-forward current and power grid voltage compensation current control variable are added in a voltage control loop, so that the rapid and effective processing of various disturbance working conditions during grid-connected operation of the device is realized, and the power supply reliability of a high-sensitivity user on the load side is enhanced.
Drawings
FIG. 1 is a schematic view of a typical topology of a medium voltage power supply quality comprehensive improving device proposed in the "medium voltage power supply quality comprehensive regulating system" patent (publication No. CN112531711A), wherein the device works in a switch CB when the device is in a grid-connected operation power quality regulating mode2And CB3Closed, CB1Disconnecting;
FIG. 2 is a block diagram of a power control strategy in the grid-connected operation control method of the apparatus of the present invention;
FIG. 3 is a block diagram of a power control strategy after a Low Pass Filter (LPF) is added to the grid-connected operation control method of the device of the present invention;
FIG. 4 is a block diagram of a frequency control strategy in the grid-connected operation control method of the apparatus of the present invention;
FIG. 5 is a block diagram of a voltage control strategy in the grid-connected operation control method of the apparatus of the present invention;
FIG. 6 shows simulation results of sudden load power conditions according to an embodiment of the present invention;
FIG. 7 shows simulation results of the voltage sag condition of the power grid according to the embodiment of the present invention;
FIG. 8 is a simulation result of grid voltage fluctuation and flicker conditions according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides a grid-connected operation control method suitable for a medium-voltage power supply quality comprehensive improving device, which comprises three control loops of power, frequency and voltage and realizes independent, rapid and effective control of the amplitude and phase angle of load voltage in the device.
Fig. 1 shows a typical topology diagram of the medium voltage power supply quality comprehensive improving device proposed in the patent of "a medium voltage power supply quality comprehensive regulating system" (publication number CN112531711A), and the switch CB is used in normal operation2And CB3Closed, CB1And when the device is disconnected, the device works in a grid-connected operation power quality adjusting mode, and the system realizes that the power quality of the power grid meets the requirements when a power quality event occurs and the load suddenly changes through quickly controlling the converter.
Fig. 2, fig. 4, and fig. 5 respectively show a power control strategy block diagram, a frequency control strategy block diagram, and a voltage control strategy block diagram in the device grid-connected operation control method, and fig. 3 shows a power control strategy block diagram after a Low Pass Filter (LPF) is added. Based on the cooperative operation of three control loops of power, frequency and voltage, the device can realize the comprehensive treatment of various power quality events, meet the requirements of high-sensitivity users on the power supply quality on the load side, and elaborate the power, frequency and voltage control loops in detail.
Power grid injection active power P in real-time acquisition device in power control loopGThe load absorbs active power PLAnd the converter absorbs the active power instruction value Pbat(wherein P isbatThe device is used for controlling the charging power of the energy storage system in the medium-voltage power supply quality comprehensive improving device and realizing the charging and discharging of the energy storage system of the device), and when the energy stored by the energy storage system of the device is in an allowable range during normal operation, the converter absorbs an active power instruction value PbatTypically zero. According to the alternating current power transmission theory, the active power P is injected into the power gridGSatisfy the requirement of
Figure BDA0003370072030000101
Thus, the grid injects active power PGIf the load is required to be quickly tracked and the active power P is absorbedLThe fluctuation of the grid voltage and the load voltage needs to be changed frequently to meet the requirement of power output response speed, so that the frequency deviation characteristic of the load side is degraded. To avoid this drawback, the load and the converter can be made to absorb the active power P in totalTObtaining a Low-Pass filtering value P of the total absorbed active power of the load and the converter through a Low Pass Filter (LPF)LPFThen active power P is injected into the power gridGLow-pass filtering value P of active power absorbed by load and converterLPFObtaining the actual difference value delta P of the active power by taking the difference, and absorbing the active power P by the loadLIs absorbed by the current transformer. Then inputting the actual active power difference value delta P into a proportional-integral controller to obtain a phase angle difference theoretical reference value delta of the power grid voltage and the load voltageref1Theoretical reference value delta of phase angle difference between grid voltage and load voltageref1Obtaining a phase angle difference reference value delta of the power grid voltage and the load voltage after a phase angle difference amplitude limiting linkref. The phase angle difference amplitude limiting link comprises an upper limit deltamaxTo the lower limit deltaminUpper limit of δmaxTo the lower limit deltaminAll are obtained by phase angle difference limiters, wherein the phase angle difference upper limit deltamaxTaking the value deltamax1Upper phase angle difference limit delta defined by power transmissionmax2Of smaller value of deltamax1Equal to the actual phase angle difference delta plus 20 degrees, and the lower limit delta of the phase angle differenceminTaking the value deltamin1Lower phase angle difference limit delta from power transmission limitmin2Larger value of between, deltamin1Equal to the actual phase angle difference delta minus 20 degrees.
Real-time acquisition device phase angle difference actual value delta of grid voltage and load voltage and grid voltage angular frequency w in frequency control loopGThen the phase angle difference reference value delta of the grid voltage and the load voltagerefAnd the actual phase angle difference delta output by the power control loop is subtracted from the actual phase angle difference delta of the power grid voltage and the load voltage to obtain an actual phase angle difference delta, and then the actual phase angle difference delta is input into a proportional-integral controller to obtain a reference value delta w of the angular frequency deviation between the load voltage and the power grid voltagerefThen the load voltage is deviated from the angular frequency reference value delta w of the power grid voltagerefWith the grid voltage angular frequency wGAfter addition, a corner frequency amplitude limiting link is carried out to obtain a load voltage corner frequency reference value wrefThen the reference value theta of the phase angle of the load voltage is obtained by inputting the reference value into an integral controllerref. The angular frequency amplitude limiting element includes an upper limit wmaxAnd a lower limit wminUpper limit of wmaxLimited upper limit w taking the value of instantaneous value of angular frequency wmax1With a defined upper limit w of the mean value within a fixed test time windowmax2Smaller value therebetween, lower limit wminLimited lower limit w taking the value of instantaneous value of angular frequency wmin1With a defined lower limit w of the mean value within a fixed test time windowmin2The larger value in between.
The voltage control loop adopts double-loop control of a voltage outer loop and a current inner loop and adopts the three-phase voltage U loaded in the device in real timeLAnd the converter outputs three-phase current ICThen respectively applying three-phase voltage U to the loadLThe converter outputs three-phase current ICUsing a park transformation (dq transformation, rotation angle being the phase angle reference theta of the load voltageref) Obtain the three-phase voltage U of the loadLD-axis component U ofLdAnd q-axis component ULqThe converter outputs three-phase current ICD-axis component I ofCdAnd q-axis component ICq. The park transformation formula is as follows:
Figure BDA0003370072030000121
d-axis component reference value U of load three-phase voltageLdrefUnder the condition of meeting the power quality requirement of a load end, the reference value U of the q-axis component of the three-phase voltage of the load can follow the voltage amplitude of the power gridLqrefThe value is typically zero. Then d-axis reference value U of three-phase voltage of loadLdrefThree-phase voltage U with loadLD-axis component U ofLdAfter the difference is made, the difference is input to a proportional-integral controller to obtain a reference value I of a d-axis component of the output three-phase current of the converter generated by a voltage outer ringCdref1Then, the reference value U of the three-phase voltage q axis of the load is comparedLqrefThree-phase voltage U with loadLQ-axis component U ofLqAfter difference is made, the difference is input to a proportional-integral controller to obtain a converter output three-phase current q-axis component reference value I generated by a voltage outer ringCqref1
When the load suddenly changes or the voltage of the power grid fluctuates, the output current (power) of the converter can be changed rapidly, and if the control is not additionally carried out, the load voltage in the device can fluctuate greatly, so that the requirement of a high-sensitivity user on the power supply quality is difficult to meet. Therefore, in combination with the instantaneous power theory, a feed-forward current branch of the converter is added in front of the current inner loop controller, and the d-axis component I of the three-phase current output by the actual converterCdProportional coefficient KFFdMultiplying to obtain d-axis component I of feed-forward current of the converterCdref2(ICdref2=KFFd*ICd) The q-axis component I of the three-phase current output by the actual converterCqProportional coefficient KFFqMultiplying to obtain a feedforward current q-axis component I of the converterCqref2(ICqref2=KFFq*ICq)。
When the voltage of the power grid suddenly drops or rises, the output current (power) of the converter can be greatly changed. When the voltage of the power grid suddenly drops, the converter outputs active power and reactive power which are increased. Electric networkWhen the voltage rises suddenly, the active power and the reactive power output by the converter are both reduced and may become negative values. Without additional control, the load voltage in the device may fluctuate greatly, which makes it difficult to meet the requirements of highly sensitive users on the quality of power supply. Therefore, in combination with the instantaneous power theory, a power grid voltage compensation current branch is added in front of the current inner loop controller, and the power grid voltage is rated to have an effective value UGNWith the actual effective value U of the network voltageGDifference value of (D) and proportionality coefficient KGdMultiplying to obtain d-axis component I of grid voltage compensation currentCdref3(ICdref3=(UGN-UG)*KGd) Rated effective value U of the network voltageGNWith the actual effective value U of the network voltageGDifference value of (D) and proportionality coefficient KGqMultiplying to obtain the q-axis component I of the grid voltage compensating currentCqref3(ICqref3=(UGN-UG)*KGq)。
Then, the reference value I of the d-axis component of the three-phase current output by the converter generated by the voltage outer ringCdref1D-axis component I of feed-forward current of converterCdref2D-axis component I of grid voltage compensation currentCdref3Adding to obtain a theoretical reference value I of d-axis components of three-phase current output by the converterCdref4Then, the converter output three-phase current q-axis component reference value I generated by the voltage outer loop is usedCqref1Feed-forward current q-axis component I of converterCqref2Q-axis component I of grid voltage compensating currentCqref3Adding to obtain a theoretical reference value I of q-axis components of three-phase current output by the converterCqref4Then outputting a theoretical reference value I of the three-phase current d-axis and q-axis components output by the converterCdref4And ICqref4Adding the three phases of the threeCdrefAnd ICqrefThe current limiting link includes an upper limit ICmaxWith a lower limit of ICmin. Upper limit of ICmaxWith a lower limit of ICminAre opposite numbers of each other, the absolute value being equal to IClim,IClimThe value is determined by the maximum allowable current of the converter.
Then outputting a three-phase current d-axis component reference value I by the converterCdrefAnd the converter outputs three-phase current ICD-axis component I ofCdThe difference is input to a proportional-integral controller to obtain the output three-phase voltage U of the d-axis current tracking converterCD-axis component reference value UCdref1Then outputting a reference value I of the q-axis component of the three-phase current to the converterCqrefAnd the converter outputs three-phase current ICQ-axis component I ofCqAfter difference is made, the difference is input into a proportional-integral controller to obtain the output three-phase voltage U of the q-axis current tracking converterCQ-axis component reference value U ofCqref1Then load the three-phase voltage ULD-axis component U ofLdD-axis current tracking converter output three-phase voltage UCD-axis component reference value UCdref1The converter outputs a three-phase current q-axis component ICqD-axis voltage feed forward value of-wLICqAdding to obtain the output three-phase voltage U of the converterCD-axis component theoretical reference value UCdref2Then load the three-phase voltage ULQ-axis component U ofLqOutput three-phase voltage U of q-axis current tracking converterCQ-axis component reference value U ofCqref1D-axis component I of three-phase current output by current transformerCdQ-axis voltage feed forward value wLICdAdding to obtain the output three-phase voltage U of the converterCQ-axis component theoretical reference value UCqref2Then the three-phase voltage U is output by the converterCD-axis and q-axis component theoretical reference value UCdref2And UCqref2The three-phase voltage U output by the converter is obtained after being input into the voltage amplitude limiting controllerCReference value U of d-axis and q-axis componentsCdrefAnd UCqrefThe voltage limiting link includes an upper limit UCmaxAnd lower limit UCmin. Upper limit UCmaxThe value is determined by the maximum allowable output voltage of the converter, and the lower limit UCminThe numerical value is not lower than zero, and can be adjusted according to the operation requirement of the device.
Then three-phase voltage U is output to the converterCReference value U of d-axis and q-axis componentsCdrefAnd UCqrefObtaining the output three-phase voltage U of the converter by carrying out park inverse transformationCReference voltage U in abc static coordinate systemCa、UCbAnd UCc. Park' PikeThe inverse transformation formula is as follows:
Figure BDA0003370072030000151
example one
In the embodiment, a simulation model of the medium-voltage power supply quality comprehensive lifting device is built by adopting software PSCAD/EMTDC, a simulation model diagram can refer to FIG. 1, and the grid-connected operation power quality regulation control method provided by the invention is added in a system operation control strategy. The technical feasibility and the effectiveness of the invention are verified by simulating and simulating several typical power quality events and testing the power quality of the load voltage in the device. The key parameters of the simulation model are shown in table 1.
Parameter name Value of parameter
Rated capacity of the device 1MVA
Rated line voltage of device 10kV
Rated active power of load 0.8MW
Rated reactive power of load 0.6Mvar
Electric network side isolation reactor L1 96mH
Load side grid-connected reactor L2 12.8mH
Number of cascaded H-bridges of each phase unit of converter 12
Rated DC voltage of H-bridge module 800V
H-bridge module DC capacitor 3000uF
Rated DC voltage of battery module 250V
Simulation working condition 1: sudden change of load power
The load power is changed from zero mutation to active power of 0.8MW and reactive power of 0.6Mvar at 1s, and the active power P is injected into the power grid in the deviceGLoad active power PLThe converter outputs active power PCLoad voltage ULacAnd load voltage power quality (load line voltage effective value U)LRMSThe measurement results of the harmonic content THD of the load line voltage, the frequency f of the load line voltage and the degree of unbalance UBF of the three phases of the load line voltage) are shown in fig. 6. It can be seen that when the load power is changed from zero to rated power, the device can effectively maintain the voltage stability of the load end and meet the power supply quality requirement of the load side. The effective value of the load line voltage amplitude is 9.9kV-10.1kV, the fluctuation rate is lower than 1%, the total harmonic distortion rate is lower than 1%, the frequency is 49.9Hz-50.1Hz, and the three-phase unbalance is lower than 1%. The electric energy quality indexes of the load voltage all reach the requirements of a 10kV alternating current system above the national standard, and the device can effectively cope with the working condition of load power sudden change.
Simulation working condition 2: network voltage sag
The amplitude of the three-phase voltage of the power grid is temporarily reduced to 0.1pu and 0.5pu respectively when the amplitude is 0.8s and 1.2s, the duration time of the voltage temporary reduction is 0.2s, and the voltage U of the power grid in the device is UGacLoad voltage ULacAnd load voltage power quality (load line voltage effective value U)LRMSThe harmonic content THD of the load line voltage, the frequency f of the load line voltage and the degree of unbalance UBF of the three phases of the load line voltage) are shown in fig. 7. It can be seen that when the voltage sag of the power grid is 0.1pu or 0.5pu, the device can effectively maintain the voltage at the load end to be stable, and meet the power supply quality requirement of the load side. Wherein, the effective value of the load line voltage amplitude is between 9.8kV and 10.3kV, the fluctuation rate is lower than 3 percent, the total harmonic distortion rate is lower than 2 percent, the frequency is between 49.6Hz and 50.4Hz, and the three-phase unbalance is lower than 1 percent. The electric energy quality indexes of the load voltage all reach the requirements of a 10kV alternating current system above the national standard, and the device is verified to be capable of effectively coping with the voltage sag working condition of a power grid.
Simulation working condition 3: network voltage fluctuation and flicker
The voltage of the power grid starts to fluctuate and flicker within 1s, the voltage amplitude is changed alternately within 0.1s between 0.9pu and 1.1pu, and the voltage of the power grid returns to normal within 1.2 s. Network voltage U in the deviceGacLoad voltage ULacAnd load voltage power quality (load line voltage effective value U)LRMSThe harmonic content THD of the load line voltage, the frequency f of the load line voltage and the degree of unbalance UBF of the three phases of the load line voltage) are shown in fig. 8. It can be seen that the device can effectively maintain the voltage stability of the load end during the voltage fluctuation and flicker of the power grid, and meet the power supply quality requirement of the load side. Wherein, the effective value of the load line voltage amplitude is basically maintained at 9.8kV to 10.2kV, the fluctuation rate is lower than 2 percent, the total harmonic distortion rate is lower than 1 percent, the frequency is between 49.9Hz and 50.1Hz, and the three-phase unbalance is lower than 0.5 percent. The electric energy quality index of load voltage all satisfies the national standard requirement, and the device can effectively deal with the unbalanced three-phase operating mode of grid voltage.
The invention provides a grid-connected operation power quality regulation control method of a medium-voltage power supply quality comprehensive lifting device, which comprises three control loops of power, frequency and voltage, wherein the power control loop obtains a reference value of a phase angle difference between grid voltage and load voltage according to active power injected into a grid and active power absorbed by a load, the frequency control loop obtains a reference value of load voltage angular frequency and phase angle according to an actual value and a reference value of the phase angle difference between the grid voltage and the load voltage, the voltage control loop adopts a double closed loop control strategy of a voltage outer loop and a current inner loop, and a feed-forward current of a converter and a compensation current of the grid voltage are introduced in front of the current inner loop to deal with disturbance when the load power and the grid voltage have large changes. By adopting three control loops of power, frequency and voltage, the invention realizes independent, rapid and effective control of the amplitude and phase angle of the load voltage in the device, can realize comprehensive treatment of various power quality events, and meets the requirement of high power supply reliability of highly sensitive users on the load side.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (8)

1. A grid-connected operation control method of a medium-voltage power supply quality comprehensive lifting device is characterized by comprising the following steps:
(1) and (3) power control:
(1-1) acquiring active power P injected into power grid in medium-voltage power supply quality comprehensive lifting deviceGThe load absorbs active power PLAnd the converter absorbs the active power instruction value PbatIn which P isbatThe charging power control device is used for controlling the charging power of an energy storage system in the medium-voltage power supply quality comprehensive lifting device;
(1-2) absorbing the active power P by the loadLAbsorbing active power instruction value P with converterbatAdding the obtained power to obtain the total absorption active power P of the load and the converterT
(1-3) injecting active power P into the power gridGWith the total absorbed active power P of the load and the converterTObtaining an actual active power difference value delta P by difference;
(1-4) inputting the actual active power difference value delta P into a controller A to obtain a phase angle difference theoretical reference value delta of the power grid voltage and the load voltageref1Theoretical reference value delta of phase angle difference between grid voltage and load voltageref1Obtaining a phase angle difference reference value delta between the power grid voltage and the load voltage through an amplitude limiting linkref(ii) a Wherein the controller A is a proportional controller, a proportional-integral-derivative controller, a proportional resonant controller, a dead-beat controller or a hysteresis controller;
(2) frequency control:
(2-1) acquiring the actual value delta of the phase angle difference between the grid voltage and the load voltage and the grid voltage angular frequency w in the medium-voltage power supply quality comprehensive improving deviceG
(2-2) phase angle difference reference value delta of grid voltage and load voltage output by power control looprefObtaining a phase angle difference actual difference value delta by subtracting the actual phase angle difference value delta of the power grid voltage and the load voltage;
(2-3) inputting the actual phase angle difference value delta into the controller B to obtain the angular frequency deviation reference value delta w of the load voltage and the power grid voltagerefWherein, the controller B is a proportional controller, a proportional-integral-derivative controller, a proportional resonant controller, a dead-beat controller or a hysteresis controller;
(2-4) deviation of angular frequency of load voltage from grid voltage by reference value Δ wrefWith the grid voltage angular frequency wGAfter addition, a corner frequency amplitude limiting link is carried out to obtain a load voltage corner frequency reference value wrefThen w isrefInputting the reference value to an integral controller to obtain a load voltage phase angle reference value thetaref
(3) Voltage control:
(3-1) double-ring control of a voltage outer ring and a current inner ring is adopted, and load three-phase voltage U in the device is adopted in real timeLAnd the converter outputs three-phase current IC
(3-2) applying three-phase voltage U to the load respectivelyLThe converter outputs three-phase current ICMaking a park transformationTransforming the rotation angle to a load voltage phase angle reference value thetarefTo obtain the three-phase voltage U of the loadLD-axis component U ofLdAnd q-axis component ULqThe converter outputs three-phase current ICD-axis component I ofCdAnd q-axis component ICq
(3-3) reference value U of d-axis component of three-phase voltage of loadLdrefThree-phase voltage U with loadLD-axis component U ofLdThe difference is input into a controller C to obtain a converter output three-phase current d-axis component reference value I generated by a voltage outer ringCdref1Wherein, the controller C is a proportional controller, a proportional-integral-derivative controller, a proportional resonant controller, a dead-beat controller or a hysteresis controller;
(3-4) reference value U of q-axis component of three-phase voltage of loadLqrefThree-phase voltage U with loadLQ-axis component U ofLqThe difference is input into a controller D to obtain a converter output three-phase current q-axis component reference value I generated by a voltage outer ringCqref1Wherein, the controller D is a proportional controller, a proportional-integral-derivative controller, a proportional resonant controller, a dead-beat controller or a hysteresis controller;
(3-5) outputting the reference value I of the three-phase current d-axis component by the converter generated by the voltage outer loopCdref1D-axis component I of feed-forward current of converterCdref2D-axis component I of grid voltage compensation currentCdref3Adding to obtain a theoretical reference value I of d-axis components of three-phase current output by the converterCdref4
(3-6) outputting the reference value I of the three-phase current q-axis component by the converter generated by the voltage outer loopCqref1Feed-forward current q-axis component I of converterCqref2Q-axis component I of grid voltage compensating currentCqref3Adding to obtain a theoretical reference value I of q-axis components of three-phase current output by the converterCqref4
(3-7) outputting the theoretical reference value I of the three-phase current d-axis and q-axis components by the converterCdref4And ICqref4Adding the three-phase current and the three-phase current, inputting the three-phase current to a current amplitude limiting controller to obtain the output three-phase current d andreference value of q-axis component ICdrefAnd ICqref
(3-8) outputting a three-phase current d-axis component reference value I by the converterCdrefAnd the converter outputs three-phase current ICD-axis component I ofCdThe difference is input into a controller E to obtain the output three-phase voltage U of the d-axis current tracking converterCD-axis component reference value UCdref1Wherein, the controller E is a proportional controller, a proportional-integral-derivative controller, a proportional resonant controller, a dead-beat controller or a hysteresis controller;
(3-9) outputting the reference value I of the three-phase current q-axis component by the converterCqrefAnd the converter outputs three-phase current ICQ-axis component I ofCqThe difference is input into a controller F to obtain the output three-phase voltage U of the q-axis current tracking converterCQ-axis component reference value U ofCqref1Wherein, the controller F is a proportional controller, a proportional-integral-derivative controller, a proportional resonant controller, a dead-beat controller or a hysteresis controller;
(3-10) applying three-phase voltage U to the loadLD-axis component U ofLdD-axis current tracking converter output three-phase voltage UCD-axis component reference value UCdref1The converter outputs a three-phase current q-axis component ICqD-axis voltage feed forward value of-wLICqAdding to obtain the output three-phase voltage U of the converterCD-axis component theoretical reference value UCdref2
(3-11) applying a three-phase voltage U to the loadLQ-axis component U ofLqOutput three-phase voltage U of q-axis current tracking converterCQ-axis component reference value U ofCqref1D-axis component I of three-phase current output by current transformerCdQ-axis voltage feed forward value wLICdAdding to obtain the output three-phase voltage U of the converterCQ-axis component theoretical reference value UCqref2
(3-12) outputting three-phase voltage U by the converterCD-axis and q-axis component theoretical reference value UCdref2And UCqref2The current transformer is obtained after the current transformer is input into a voltage amplitude limiting controllerOutput three-phase voltage UCReference value U of d-axis and q-axis componentsCdrefAnd UCqref
(3-13) outputting three-phase voltage U to the converterCReference value U of d-axis and q-axis componentsCdrefAnd UCqrefObtaining the output three-phase voltage U of the converter by inverse Pack transformationCReference voltage U in abc static coordinate systemCa、UCbAnd UCc
2. The grid-connected operation control method of the medium-voltage power supply quality comprehensive improving device according to claim 1, characterized in that: the phase angle difference amplitude limiting link in the power control comprises an upper limit deltamaxTo the lower limit deltaminUpper limit of δmaxTo the lower limit deltaminAll are obtained by phase angle difference limiters, wherein the phase angle difference upper limit deltamaxTaking the value deltamax1Upper phase angle difference limit delta defined by power transmissionmax2Of smaller value of deltamax1Equal to the actual phase angle difference delta plus 20 degrees, and the lower limit delta of the phase angle differenceminTaking the value deltamin1Lower phase angle difference limit delta from power transmission limitmin2Larger value of between, deltamin1Equal to the actual phase angle difference delta minus 20 degrees.
3. The grid-connected operation control method of the medium-voltage power supply quality comprehensive improving device according to claim 1, characterized in that: the angular frequency amplitude limiting link in the frequency control comprises an upper limit wmaxAnd a lower limit wminUpper limit of wmaxLimited upper limit w taking the value of instantaneous value of angular frequency wmax1With a defined upper limit w of the mean value within a fixed test time windowmax2Smaller value therebetween, lower limit wminLimited lower limit w taking the value of instantaneous value of angular frequency wmin1With a defined lower limit w of the mean value within a fixed test time windowmin2The larger value in between.
4. The grid-connected operation control method of the medium-voltage power supply quality comprehensive improving device according to claim 1, characterized in that: d-axis component reference of load three-phase voltage in voltage controlValue ULdrefThe voltage control circuit can follow the voltage amplitude of the power grid under the condition of meeting the power quality requirement of a load end, and the reference value U of the q-axis component of the three-phase voltage of the load in the voltage control circuitLqrefThe value is zero.
5. The grid-connected operation control method of the medium-voltage power supply quality comprehensive improving device according to claim 1, characterized in that: the d-axis component I of the feed-forward current of the converter in the voltage controlCdref2D-axis component I equal to three-phase current output by actual converterCdProportional coefficient KFFdThe product of (a), a converter feed-forward current q-axis component I in the voltage control loopCqref2Q-axis component I equal to three-phase current output by actual converterCqProportional coefficient KFFqThe product of (a).
6. The grid-connected operation control method of the medium-voltage power supply quality comprehensive improving device according to claim 1, characterized in that: the d-axis component I of the grid voltage compensation current in the voltage controlCdref3Equal to the rated effective value U of the network voltageGNWith the actual effective value U of the network voltageGIs multiplied by the scaling factor KGdA grid voltage compensation current q-axis component I in the voltage control loopCqref3Equal to the rated effective value U of the network voltageGNWith the actual effective value U of the network voltageGIs multiplied by the scaling factor KGq
7. The grid-connected operation control method of the medium-voltage power supply quality comprehensive improving device according to claim 1, characterized in that: the current amplitude limiting link in the voltage control comprises an upper limit ICmaxWith a lower limit of ICminUpper limit ofCmaxWith a lower limit of ICminAre opposite numbers of each other, the absolute value being equal to IClim,IClimThe value is determined by the maximum allowable current of the converter.
8. The grid-connected operation control method of the medium-voltage power supply quality comprehensive improving device according to claim 1, which is characterized in thatCharacterized in that: the voltage amplitude limiting link in the voltage control comprises an upper limit UCmaxAnd lower limit UCminUpper limit of UCmaxThe value is determined by the maximum allowable output voltage of the converter, and the lower limit UCminThe numerical value is not lower than zero, and can be adjusted according to the operation requirement of the device.
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