CN104836455A - Power distribution network power electronic transformer and control method thereof - Google Patents
Power distribution network power electronic transformer and control method thereof Download PDFInfo
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- CN104836455A CN104836455A CN201510202631.6A CN201510202631A CN104836455A CN 104836455 A CN104836455 A CN 104836455A CN 201510202631 A CN201510202631 A CN 201510202631A CN 104836455 A CN104836455 A CN 104836455A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
- H02M7/2195—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration the switches being synchronously commutated at the same frequency of the AC input voltage
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
The invention provides a power distribution network power electronic transformer and a control method thereof. The power distribution network power electronic transformer comprises an input stage, an isolation transformation stage and an output stage; the output stage is provided with a super capacitor; the output stage is of a voltage source type four-leg inverting topologic structure; the positive pole of the super capacitor is connected with the middle point of the fourth leg; and the negative pole of the super capacitor is connected with the negative end of a bus-bar. According to the power distribution network power electronic transformer provided by the invention, the fourth leg which is adopted as a neutral line in the interior of the transformer is adopted as a charging and discharging interface of a super capacitor energy storage system, and therefore, the power distribution network power electronic transformer can be seamlessly connected with the super capacitor, and response speed is high, and an additional power conversion circuit and control system are not required, and flexible energy storage can be realized. The power distribution network power electronic transformer has short-time uninterruptible power supply ability and extremely high power fluctuation bearing ability, and can realize stable operation under load abrupt rise.
Description
Technical field
The present invention relates to field of power electronics, be specifically related to a kind of power distribution network electric power electric transformer and control method thereof.
Background technology
In recent years, Technics of Power Electronic Conversion technical development is rapid, its up-to-date utilization---electric power electric transformer (Power Electronic Transformer in electric power system, PET), combine high frequency transformer, the voltage transformation in electric power system and energy transferring can be realized, obtained the burning hot research of Chinese scholars.PET is applied to the real-time control that power distribution network outstanding feature is AC voltage magnitude and phase place, can realize the flexible of transformer primary secondary voltage, electric current and power, therefore possesses the potentiality solving many new problems in electric power system, has a extensive future.
But, power distribution network electric power electric transformer (Distribution Power ElectronicTransformer, DPET) runs on electrical network end, and running environment is complicated, high side voltage is unstable, and the voltage degree of depth caused by fault is fallen and happened occasionally with short supply interruption situation.Configuration in the line possesses the power electronic equipment of super capacitor (Super Capacitor, SC) energy storage, and carrying out voltage compensation when supply voltage falls, is a kind of widely used measure.Be typically chosen in extra increase SC energy-storage system on DPET low-voltage direct bus in prior art, although can compensation effect be reached like this, such a process increases extra DC/DC power conversion circuit, add system cost, and make compensation response speed slack-off.
Summary of the invention
For defect of the prior art, the invention provides a kind of power distribution network electric power electric transformer and control method thereof, additionally on DPET low-voltage direct bus increase SC energy-storage system and the system cost that causes increases and compensates the slack-off problem of response speed to solve in prior art.
For solving the problem, the invention provides following scheme:
First aspect, the invention provides a kind of power distribution network electric power electric transformer, comprises input stage, isolated variable level and output stage, described output stage is provided with super capacitor;
Described output stage adopts voltage-source type four bridge legs inversion topological, and the positive pole of described super capacitor is connected to four bridge legs mid point, and negative pole connects DC bus negative terminal.
Wherein, described power distribution network electric power electric transformer carries out discharge and recharge by brachium pontis power device to described super capacitor.
Wherein, described input stage adopts the many level topologys of cascaded H-bridges, and the HM chain link module-cascade that each brachium pontis is n by quantity forms, and HM chain link module main circuit is H bridge construction, three brachium pontis are connected to form by Y type, are the direct current of the suspension of 3n by high pressure industrial frequency AC formation number.
Wherein, each unit of described isolated variable level adopts two initiatively bridge topology DAB, and total unit number is 3n, and each DAB side is connected with HM chain link, and opposite side composes in parallel DC bus.
Wherein, described super capacitor is in series with inductance, to reduce current ripple.
Second aspect, present invention also offers a kind of power distribution network electric power electric transformer control method, and wherein, described power distribution network electric power electric transformer comprises input stage, isolated variable level and output stage, and described output stage is provided with super capacitor;
Described output stage adopts voltage-source type four bridge legs inversion topological, and the positive pole of described super capacitor is connected to four bridge legs mid point, and negative pole connects DC bus negative terminal;
Described control method comprises:
The current-mode control that described four bridge legs adopts instruction stackable, center line electric current and super capacitor charging and discharging currents carry out complex controll, and wherein the instruction of four bridge legs Current Control is
particularly, when super capacitor discharges, control objectives, for keeping DC bus-bar voltage constant, obtains Current Control instruction
equal discharging current
when super capacitor charges, control objectives, for keeping super capacitor terminal voltage constant, obtains Current Control instruction
equal charging current instruction
wherein, current in middle wire control command is added by three-phase current and obtains, i
n=i
a+ i
b+ i
c, control four bridge legs output current-i
n, with in bucking-out system due to three-phase imbalance produce current in middle wire.
Wherein, described input stage adopts the many level topologys of cascaded H-bridges, and the HM chain link module-cascade that each brachium pontis is n by quantity forms, and HM chain link module main circuit is H bridge construction, three brachium pontis are connected to form by Y type, are the direct current of the suspension of 3n by high pressure industrial frequency AC formation number.
The each brachium pontis of described input stage three-phase is symmetrical, and each phase control strategy is identical; Wherein each phase control strategy adopts and controls based on the voltage of synchronous rotary d-q coordinate system, current double closed-loop, shifts to CPS-SPWM modulation strategy in conjunction with carrier wave.
Wherein, each unit of described isolated variable level adopts two initiatively bridge topology DAB, and total unit number is 3n, and each DAB side is connected with HM chain link, and opposite side composes in parallel DC bus.
Described isolated variable level is the DAB transmitted in both directions energy of 3n by quantity, jointly realize DC bus-bar voltage constant, wherein for single DAB, the drive singal of two active bridges is the complementary trigger impulse that duty ratio is 50%, and two corresponding switching tube conductings of bridge exist a phase shift angle
when
for on the occasion of time, power forward flow, when
during for negative value, power reverse flow; In each DAB, add equal power control, the difference of the power and instruction power that each DAB is different can produce different phase shifting angle variablees
to adjust the flow of power that phase shifting angle balances each DAB.
Wherein, first three brachium pontis of the voltage-source type four-leg inverter that described output stage adopts and four bridge legs are independent control section, and wherein first three brachium pontis controls the positive sequence of output voltage and negative sequence component, ensure that three-phase exports constant voltage constant frequency.
Wherein, described super capacitor is in series with inductance, to reduce current ripple.
As shown from the above technical solution, power distribution network electric power electric transformer of the present invention, utilize the inner four bridge legs serving as center line to serve as the discharge and recharge interface of super capacitor energy-storage system simultaneously, seamless link super capacitor, fast response time, without the need to additionally increasing power conversion circuit and control system, realize flexible energy storage.
The control method of power distribution network electric power electric transformer provided by the invention does not affect the control of four bridge legs center line electric current, possesses uninterrupted power supply ability in short-term, and possesses the power fluctuation ability to bear of superelevation, can realize the stable operation under throwing-on.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
Fig. 1 is the electrical block diagram of the power distribution network electric power electric transformer that one embodiment of the invention provides;
Fig. 2 is the control strategy schematic diagram of four bridge legs in one embodiment of the invention; ;
Fig. 3 is input stage control strategy schematic diagram in one embodiment of the invention;
Fig. 4 is that in one embodiment of the invention, two initiatively bridge DAB shifts to control strategy schematic diagram;
Fig. 5 is output stage VSI control strategy schematic diagram in one embodiment of the invention.
Embodiment
For making the object of the embodiment of the present invention, technical scheme and advantage clearly, below in conjunction with the accompanying drawing in the embodiment of the present invention, clear, complete description is carried out to the technical scheme in the embodiment of the present invention, obviously, described embodiment is the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.
Fig. 1 shows the electrical block diagram of the power distribution network electric power electric transformer that one embodiment of the invention provides, the power distribution network electric power electric transformer that the present embodiment provides is a kind of power distribution network electric power electric transformer interactive flexibly with super capacitor (Super Capacitor basedDistribution Power Electronic Transformer is called for short SCDPET).The four bridge legs that the SCDPET that the present embodiment provides utilizes DPET inside to serve as center line serves as the discharge and recharge interface of super capacitor energy-storage system simultaneously, and seamless link super capacitor, without the need to additionally increasing power conversion circuit and control system, realizes flexible energy storage.As shown in Figure 1, the SCDPET that the present embodiment provides comprises: input stage, isolated variable level and output stage, described output stage is provided with super capacitor, and namely output stage is integrated with super capacitor energy-storage system, as shown in Figure 1.
Described output stage adopts voltage-source type four bridge legs inversion topological, and the positive pole of described super capacitor is connected to four bridge legs mid point, and negative pole connects DC bus negative terminal.
Wherein, described power distribution network electric power electric transformer carries out discharge and recharge by brachium pontis power device to described super capacitor.
Wherein, described input stage adopts the many level of cascaded H-bridges (Cascade H-bridgeMulti-level, CHM) topology, the HM chain link module-cascade that each brachium pontis is n by quantity forms, HM chain link module main circuit is H bridge construction, 3 brachium pontis are connected to form by Y type, are the direct current of the suspension of 3n by high pressure industrial frequency AC formation number, and cascaded multilevel structure makes input stage power device can be applied to high-power with less voltage stress and switching frequency.
Wherein, each unit of described isolated variable level adopts two initiatively bridge topology (Dual ActiveBridge, DAB), controls energy in bidirectional flow; Total unit number is 3n, and each DAB side is connected with HM chain link, and opposite side composes in parallel DC bus.
In a preferred embodiment of the invention, described super capacitor is in series with inductance, and series inductance L reduces current ripples.
Described output stage adopts voltage-source type four bridge legs inversion (4-leg Voltage SourceInverter, VSI) topology, can directly control by center line electric current, and have and control flexibly, without the need to large DC-link electric capacity and the high advantage of direct voltage utilance, be suitable for power distribution network application.The positive pole of super capacitor connects four bridge legs mid point, negative pole connects DC bus negative terminal (alternatively, series inductance L reduces current ripples), by controlling brachium pontis power device, discharge and recharge being carried out to super capacitor, realizing and super capacitor and DC bus energy interactions.
The SCDPET that the embodiment of the present invention provides, utilize the inner four bridge legs serving as center line to serve as the discharge and recharge interface of super capacitor energy-storage system, seamless link super capacitor, fast response time simultaneously, without the need to additionally increasing power conversion circuit and control system, realize flexible energy storage.The power distribution network electric power electric transformer that the embodiment of the present invention provides does not affect the control of four bridge legs center line electric current, possesses uninterrupted power supply ability in short-term, and possesses the power fluctuation ability to bear of superelevation, can realize the stable operation under throwing-on.
One embodiment of the invention provides a kind of control method of power distribution network electric power electric transformer, wherein, described power distribution network electric power electric transformer is a kind of power distribution network electric power electric transformer interactive flexibly with super capacitor (Super Capacitor based Distribution PowerElectronic Transformer is called for short SCDPET).Described SCDPET comprises input stage, isolated variable level and output stage, and described output stage is provided with super capacitor;
Described output stage adopts voltage-source type four bridge legs inversion topological, and the positive pole of described super capacitor is connected to four bridge legs mid point, and negative pole connects DC bus negative terminal;
The control method of described SCDPET comprises:
The current-mode control that described four bridge legs adopts instruction stackable, center line electric current and super capacitor charging and discharging currents carry out complex controll, and wherein the instruction of four bridge legs Current Control is
particularly, when super capacitor discharges, control objectives, for keeping DC bus-bar voltage constant, obtains Current Control instruction
equal discharging current
when super capacitor charges, control objectives, for keeping super capacitor terminal voltage constant, obtains Current Control instruction
equal charging current instruction
wherein, current in middle wire control command is added by three-phase current and obtains, i
n=i
a+ i
b+ i
c, control four bridge legs output current-i
n, with in bucking-out system due to three-phase imbalance produce current in middle wire.
SCDPET operates in electrical network end, high-pressure side due to the failure and other reasons voltage degree of depth fall, even short supply interruption, the situation of low-pressure side load big ups and downs happens occasionally, and these situations can regard power vacancy in short-term as from power perspective.Therefore SCDPET relies on the stored energy of DC bus capacitor to be difficult to maintain outlet side voltage, now coordinates the high-power discharge and recharge of super capacitor short-term, carries out energy interactions, then can make SCDPET even running with DC bus capacitor, keeps stable and exports.
Wherein, super capacitor mainly operates in three kinds of states:
(1) when super capacitor energy-storage is sufficient and SCDPET normally runs, without the need to energy interactions, maintain super capacitor terminal voltage by four bridge legs constant, be energy storage state, keep for subsequent use.
(2) when emergent power vacancy, DC bus-bar voltage there will be falls sign, now, super capacitor energy flows into DC bus through four bridge legs, supplement the power needed for load, reach the object of stable DC busbar voltage, super capacitor works in discharge condition.
(3) when power system restoration is normal, it is constant that two active bridge DAB maintains DC bus-bar voltage, and four bridge legs controls super capacitor and works in normal direct current charged state.Be charged to desired value once super-capacitor voltage, revert to energy storage state.
Super capacitor persistent loop between three kinds of states runs, and is controlled flexibly, guarantee power supply fast by four bridge legs.
While super capacitor discharge and recharge, can not affect current in middle wire and control, so the current-mode control that four bridge legs adopts instruction stackable, center line electric current and super capacitor charging and discharging currents complex controll, four bridge legs control strategy as shown in Figure 2.Switch is super capacitor control model selector switch, and during electric discharge, control objectives, for keeping DC bus-bar voltage constant, obtains Current Control instruction
equal discharging current
during charging, control objectives, for keeping super capacitor terminal voltage constant, obtains Current Control instruction
equal charging current instruction
current in middle wire control command is added by three-phase current and obtains, i
n=i
a+ i
b+ i
c, control four bridge legs output current-i
n, then in bucking-out system due to three-phase imbalance produce current in middle wire.The four bridge legs Current Control instruction finally obtained is
current tracking adopts the proportional integral (PI) being simple and easy to realize to control.
In one embodiment of the invention, described input stage adopts the many level topologys of cascaded H-bridges, the HM chain link module-cascade that each brachium pontis is n by quantity forms, HM chain link module main circuit is H bridge construction, three brachium pontis are connected to form by Y type, are the direct current of the suspension of 3n by high pressure industrial frequency AC formation number.
The each brachium pontis of described input stage three-phase is symmetrical, and each phase control strategy is identical; Wherein each phase control strategy as shown in Figure 3, adopts and control based on the voltage of synchronous rotary d-q coordinate system, current double closed-loop, shift to CPS-SPWM modulation strategy in conjunction with carrier wave.U
sd, u
sqfor line voltage U
srotational component under d-q coordinate system, the phase signal θ that phase-locked link PLL exports is for providing the reference phase needed for voltage vector oriented control and modulation.Outer shroud voltage control is according to measured capacitance voltage u
d1, u
d2and u
dnreference value U is equaled etc. the direct current total voltage of stable brachium pontis electric capacity
dref,
for the meritorious reference current instruction obtained, specify idle reference current
be zero.Inner ring current controller realizes the direct control of CHM rectifier ac-side current waveform, makes output current i
squick track reference electric current, is presented as active current i under d-q coordinate system
sd, reactive current i
sqfollow the tracks of their reference instruction
v
dref, v
qreffor d, q component of the modulating wave that inner ring Current Control obtains.Pressure and Control regulate and make each HM module capacitance voltage equal, and the adjustment component Δ d obtained is added to modulating wave d component at different levels.2 π/the N that stagger mutually of the triangular carrier of each HM module, between inside modules brachium pontis, triangular carrier staggers π, thus realizes CPS-SPWM modulation, obtains the output waveform of many level.
In one embodiment of the invention, each unit of described isolated variable level adopts two initiatively bridge topology (Dual Active Bridge, DAB), controls energy in bidirectional flow; Total unit number is 3n, and each DAB side is connected with HM chain link, and opposite side composes in parallel DC bus.
Isolated variable level is the DAB transmitted in both directions energy of 3n by quantity, jointly realizes DC bus-bar voltage constant.Being for the drive singal of single DAB, DAB two active bridge the complementary trigger impulse that duty ratio is 50%, there is a phase shift angle in two corresponding switching tube conductings of bridge.When
for on the occasion of time, power forward flow, when
during for negative value, power reverse flow.
Owing to may there is imbalance between the voltage of high voltage direct current side, and the parameter of each DAB is incomplete same, so the flow of power between each DAB can be caused during stable state unbalanced, device voltage current stress may be caused in extreme circumstances excessive.Therefore in each DAB, add equal power control, the difference of the power and instruction power that each DAB is different can produce different phase shift angle regulated quantitys
thus adjustment phase shifting angle balances the flow of power of each DAB.
DAB phase shifting angle controls as shown in Figure 4,
for DC bus-bar voltage reference value, P
*, i
*for the power instruction that obtained by pi regulator and current-order, control to shift to angle
superpose the phase shift angle regulated quantity that power adjustment obtains again
obtain 50% duty ratio, phase
square wave.
In one embodiment of the invention, first three brachium pontis of voltage-source type four-leg inverter of adopting of described output stage and four bridge legs are independent control section.For distribution, expect that the output of SCDPET is not by the impact of high-voltage fence, do not affect by load big ups and downs and imbalance, this just requires that first three brachium pontis of VSI controls the positive sequence of output voltage and negative sequence component, ensures that three-phase exports constant voltage constant frequency.And four bridge legs controls current in middle wire, eliminate residual voltage distortion; And control super capacitor discharge and recharge, supplemental capacity vacancy.Wherein first three brachium pontis and four bridge legs are two independently control sections.
The control strategy of three-phase brachium pontis as shown in Figure 5, utilizes outer voltage to realize the constant control of output voltage, and utilize current inner loop to realize the quick tracking of output current, wherein voltage and current closed loop all have employed uneoupled control.U
a ref, u
b ref, u
c refrepresent the reference signal that three-phase voltage exports, u
od *, u
oq *voltage reference signal under expression dq axle, u
od, u
oqrepresent output voltage actual value, after outer voltage uneoupled control, obtain the output current reference value i under dq axle
d *, i
q *, i
d, i
qrepresent output current actual value, after current inner loop uneoupled control, obtain the voltage modulation signal u under dq axle
d, u
q, after coordinate transform, obtain three-phase voltage modulation signal u
a *, u
b *, u
c *, then export through PWM rear drive VSI.
Particularly, described super capacitor is in series with inductance, to reduce current ripple.
In sum, high-voltage alternating is become 3N the direct current suspended by HM chain link module by SCDPET control inputs level CHM rectifier, and direct voltage at different levels is constant and equal, and ensures the power factor (PF) of high-voltage alternating side; The former side of isolation level DAB carries out DC/AC conversion, is high-frequency ac by HVDC Modulation, and through high frequency transformer coupling, pair side carries out AC/DC conversion, and high-frequency ac is reduced to direct current; Direct current is carried out inversion by output stage, realizes constant voltage constant frequency and exports; Four bridge legs regulates current in middle wire, controls super capacitor discharge and recharge simultaneously.
The power distribution network electric power electric transformer (i.e. SCDPET) that the present embodiment provides, utilizing four bridge legs to serve as the discharge and recharge interface of super capacitor energy-storage system simultaneously, without the need to additionally increasing power conversion circuit and control system, reducing system cost.
The power distribution network electric power electric transformer that the present embodiment provides, possesses uninterrupted power supply ability in short-term, and possesses the power fluctuation ability to bear of superelevation, can realize the stable operation under throwing-on
The power distribution network electric power electric transformer that the present embodiment provides, seamless link super capacitor, fast response time, achieves flexible energy storage.
The power distribution network electric power electric transformer control method that the present embodiment provides, at the electric current complex controll that four bridge legs adopts instruction stackable, while super capacitor discharge and recharge, does not affect current in middle wire and controls.
Above embodiment only for illustration of technical scheme of the present invention, is not intended to limit; Although with reference to previous embodiment to invention has been detailed description, those of ordinary skill in the art is to be understood that: it still can be modified to the technical scheme described in foregoing embodiments, or carries out equivalent replacement to wherein portion of techniques feature; And these amendments or replacement, do not make the essence of appropriate technical solution depart from the spirit and scope of various embodiments of the present invention technical scheme.
Claims (10)
1. a power distribution network electric power electric transformer, is characterized in that, comprises input stage, isolated variable level and output stage, described output stage is provided with super capacitor;
Described output stage adopts voltage-source type four bridge legs inversion topological, and the positive pole of described super capacitor is connected to four bridge legs mid point, and negative pole connects DC bus negative terminal.
2. power distribution network electric power electric transformer according to claim 1, is characterized in that, described power distribution network electric power electric transformer carries out discharge and recharge by brachium pontis power device to described super capacitor.
3. power distribution network electric power electric transformer according to claim 1, it is characterized in that, described input stage adopts the many level topologys of cascaded H-bridges, the HM chain link module-cascade that each brachium pontis is n by quantity forms, HM chain link module main circuit is H bridge construction, three brachium pontis are connected to form by Y type, are the direct current of the suspension of 3n by high pressure industrial frequency AC formation number.
4. power distribution network electric power electric transformer according to claim 3, is characterized in that, each unit of described isolated variable level adopts two initiatively bridge topology DAB, and total unit number is 3n, and each DAB side is connected with HM chain link, and opposite side composes in parallel DC bus.
5., according to the arbitrary described power distribution network electric power electric transformer of claim 1-4, it is characterized in that, described super capacitor is in series with inductance, to reduce current ripple.
6. a power distribution network electric power electric transformer control method, is characterized in that,
Described power distribution network electric power electric transformer comprises input stage, isolated variable level and output stage, and described output stage is provided with super capacitor;
Described output stage adopts voltage-source type four bridge legs inversion topological, and the positive pole of described super capacitor is connected to four bridge legs mid point, and negative pole connects DC bus negative terminal;
Described control method comprises:
The current-mode control that described four bridge legs adopts instruction stackable, center line electric current and super capacitor charging and discharging currents carry out complex controll, and wherein the instruction of four bridge legs Current Control is
particularly, when super capacitor discharges, control objectives, for keeping DC bus-bar voltage constant, obtains Current Control instruction
equal discharging current
when super capacitor charges, control objectives, for keeping super capacitor terminal voltage constant, obtains Current Control instruction
equal charging current instruction
wherein, current in middle wire control command is added by three-phase current and obtains, i
n=i
a+ i
b+ i
c, control four bridge legs output current-i
n, with in bucking-out system due to three-phase imbalance produce current in middle wire.
7. power distribution network electric power electric transformer control method according to claim 6, it is characterized in that, described input stage adopts the many level topologys of cascaded H-bridges, the HM chain link module-cascade that each brachium pontis is n by quantity forms, HM chain link module main circuit is H bridge construction, three brachium pontis are connected to form by Y type, are the direct current of the suspension of 3n by high pressure industrial frequency AC formation number;
The each brachium pontis of described input stage three-phase is symmetrical, and each phase control strategy is identical; Wherein each phase control strategy adopts and controls based on the voltage of synchronous rotary d-q coordinate system, current double closed-loop, shifts to CPS-SPWM modulation strategy in conjunction with carrier wave.
8. power distribution network electric power electric transformer control method according to claim 7, it is characterized in that, each unit of described isolated variable level adopts two initiatively bridge topology DAB, and total unit number is 3n, each DAB side is connected with HM chain link, and opposite side composes in parallel DC bus;
Described isolated variable level is the DAB transmitted in both directions energy of 3n by quantity, jointly realize DC bus-bar voltage constant, wherein for single DAB, the drive singal of two active bridges is the complementary trigger impulse that duty ratio is 50%, and two corresponding switching tube conductings of bridge exist a phase shift angle
when
for on the occasion of time, power forward flow, when
during for negative value, power reverse flow; In each DAB, add equal power control, the difference of the power and instruction power that each DAB is different can produce different phase shift angle regulated quantitys
to adjust the flow of power that phase shifting angle balances each DAB.
9. power distribution network electric power electric transformer control method according to claim 8, it is characterized in that, first three brachium pontis of the voltage-source type four-leg inverter that described output stage adopts and four bridge legs are independent control section, wherein first three brachium pontis controls the positive sequence of output voltage and negative sequence component, ensures that three-phase exports constant voltage constant frequency.
10., according to the arbitrary described power distribution network electric power electric transformer control method of claim 6-9, it is characterized in that, described super capacitor is in series with inductance, to reduce current ripple.
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