CN105846466A - DAB converter-based multiterminal input photovoltaic grid connected system power balance control strategy - Google Patents

DAB converter-based multiterminal input photovoltaic grid connected system power balance control strategy Download PDF

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Publication number
CN105846466A
CN105846466A CN201610321839.4A CN201610321839A CN105846466A CN 105846466 A CN105846466 A CN 105846466A CN 201610321839 A CN201610321839 A CN 201610321839A CN 105846466 A CN105846466 A CN 105846466A
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voltage
current
controller
changer
grid connected
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CN105846466B (en
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严干贵
贾祺
段双明
钟诚
李泳霖
吴薇
张津豪
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Northeast Electric Power University
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Northeast Dianli University
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    • H02J3/383—
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Electrical Variables (AREA)
  • Supply And Distribution Of Alternating Current (AREA)
  • Photovoltaic Devices (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a DAB converter-based multiterminal input photovoltaic grid connected system power balance control strategy which is characterized by comprising the following steps: voltage of all high voltage direct current ends in a multiterminal input photovoltaic grid connected system is measured, a direct current voltage average value of the high voltage ends is obtained, a photovoltaic grid connected current is measured and is subjected to Part transformation operation, and therefore a grid connected current d axis component; an object of tracking the direct current voltage average value is set, a reference value of the direct current voltage average value is given, and a reference value of the grid connected current d axis component is obtained; a reference value of a grid connected current q axis component is set as 0, modulation quantities of all DC/AC units in all multi-level DC/AC convertors connected in cascade are calculated, the modulation quantities of all the DC/AC units are corrected via direct current voltage compensation and zero sequence voltage injection, direct current voltage balance and grid connected current balance of all high voltage ends in the system can be realized, the and therefore system power balance can be achieved.

Description

Multiterminal based on DAB changer input photovoltaic parallel in system power-balance controls Strategy
Technical field
The present invention relates to photovoltaic networking generator operation control field, be that a kind of multiterminal based on DAB changer input grid-connected system System power-balance control strategy.
Background technology
In large-scale photovoltaic grid-connected system, in order to reduce the power requirement of each power module, need multiple inverter parallels. When multiple inverter parallel, due to the existence of LCL filter, can cause grid-connected current that resonance occurs under some characteristic frequency, Make grid-connected current that serious distortion occur, affect photovoltaic generation performance.Further, along with the increase of shunt chopper number, single Individual inverter dynamic responding speed is slack-off, and output impedance reduces, and the stability of system reduces the most accordingly.
From the circuit topological structure of photovoltaic generation two-stage type grid-connected system, voltage boosting dc chopper circuit is generally used to realize light The maximum power tracing of volt generator unit.But, DC chopper circuit input and output pulsation of current is big, is easily generated electromagnetic interference, It is not provided that electrical isolation, is unfavorable for the safe operation of photovoltaic generating system.
Therefore, study a kind of multiterminal based on DAB changer input photovoltaic system structure, this system mainly by multiple photovoltaic arrays, Multiple DAB changers, cascade connection multi-level DC/AC changer is constituted, and the low-voltage direct end of each DAB changer connects photovoltaic Array, HVDC end connects cascade connection multi-level DC/AC changer.The use of DAB changer brings the good of electrical isolation Place, it is ensured that the safe operation of each photovoltaic array.Circuit structure also reduces and uses LCL filter, it is to avoid LCL filters The coupled resonance problem that device brings.But, large-scale photovoltaic array is divided into by this system several fritter photovoltaic arrays, when respectively During fritter photovoltaic array illuminance difference, each high-pressure side DC voltage in this system and grid-connected current can be affected.For solving system Voltage and current equilibrium problem in system, needs to add balance control strategy.
Summary of the invention
The technical problem to be solved is, overcomes the deficiencies in the prior art, it is provided that a kind of scientific and reasonable, the suitability is strong, Multiterminal based on the DAB changer input photovoltaic parallel in system power-balance control strategy that effect is good, solves each photovoltaic array illumination When degree is different, mutually in each DC terminal voltage balance control and alternate current balance type controls, thus improve multiterminal input photovoltaic The grid-connected system quality of power supply, and ensure the safe operation of each photovoltaic array.
Solve its technical problem employed technical scheme comprise that, a kind of multiterminal based on DAB changer input photovoltaic parallel in system power Balance control strategy, is characterized in that, it comprises the following steps:
(1) each HVDC terminal voltage U in multiterminal input photovoltaic parallel in system is measureddcai, Udcbi, Udcci, ask for high-pressure side DC voltage average value Udcavg；Measure grid-connected electric current isa, isb, isc, process through Park Transformation and obtain having of d axle component Merit electric current id, reactive current i of q axle componentq；
(2) to follow the trail of DC voltage average value as target, reference value U of a given DC voltage average valuedcref, by direct current Average voltage and UdcrefVoltage difference be input in PI controller, the time-domain expression through PI controller calculates one D axle watt current reference instruction idref, it is considered to multiterminal input photovoltaic parallel in system unity power factor runs, if the idle reference of q axle Current-order iqrefBeing 0, the time-domain expression of PI controller is idref=Kp(Udcref-Udcavg)+Ki∫(Udcref-Udcavg)dt；
(3) watt current i that will obtain in step (1)d, reactive current iqRespectively with the watt current reference in step (2) Instruction idref, idle reference current instruction iqrefDiffering from, and difference inputs PI controller, the time domain through PI controller is expressed Formula calculates d axle cascade connection multi-level DC/AC changer output voltage Ud, q axle cascade connection multi-level DC/AC changer output electricity Pressure Uq, and then obtain modulation voltage v of each DC/AC unit in each phase cascade connection multi-level DC/AC changerai、vbi、vci, i=1, 2 ... the time-domain expression of n, PI controller is Ud=Kp(idref-id)+Ki∫(idref-id) dt, Uq=Kp(iqref-iq)+Ki∫(iqref-iq)dt；
(4) each HVDC terminal voltage U will measured in step (1)dcai, Udcbi, UdcciWith UdcavgError signal warp Cross after proportional controller vai、vbi、vciCompensate according to side-play amount, obtain new modulation voltage vai1、vbi1、vci1, it is ensured that each During photovoltaic array output difference, each DAB high-pressure side dc-voltage balance；
(5) on the basis of step (4), each modulation voltage in each phase cascade connection multi-level DC/AC changer is modified, introduces Zero-sequence component, obtains modulation voltage vai2、vbi2、vci2, three phase power is redistributed, it is ensured that the symmetry of three-phase grid electric current, Realize current balance type control.
Multiterminal based on the DAB changer input photovoltaic parallel in system power-balance control strategy of the present invention, it is possible to pass through unidirectional current Pressure compensates the voltage balance control in realizing mutually, realizes alternate current balance type by injected zero-sequence voltage and controls, thus Realize the power-balance of system, ensure the safe operation of each photovoltaic array simultaneously.Have scientific and reasonable, practical, effect The advantage such as good.
Accompanying drawing explanation
Fig. 1 is a kind of based on DAB changer the multiterminal input photovoltaic system structural representation that the present invention proposes；
Fig. 2 is the control strategy schematic diagram that the voltage and current equilibrium problem in solution system uses；
DC voltage waveform schematic diagram when Fig. 3 is not use DC voltage to compensate；
Dc-voltage balance waveform diagram when Fig. 4 is to use DC voltage to compensate；
Fig. 5 is to use injected zero-sequence voltage three-phase grid current balance type waveform diagram.
Detailed description of the invention
Below with drawings and Examples, the multiterminal based on DAB changer of the present invention are inputted photovoltaic parallel in system power-balance Control strategy is described in detail.
See figures.1.and.2, multiterminal based on the DAB changer input photovoltaic parallel in system power-balance control strategy of the present invention, Comprise the following steps:
A kind of multiterminal based on DAB changer input photovoltaic parallel in system power-balance control strategy, comprises the following steps:
(1) each HVDC terminal voltage U in multiterminal input photovoltaic parallel in system is measureddcai, Udcbi, Udcci, ask for high-pressure side DC voltage average value Udcavg；Measure grid-connected electric current isa, isb, isc, process through Park Transformation and obtain having of d axle component Merit electric current id, reactive current i of q axle componentq；
(2) to follow the trail of DC voltage average value as target, reference value U of a given DC voltage average valuedcref, by direct current Average voltage and UdcrefVoltage difference be input in PI controller, the time-domain expression through PI controller calculates one D axle watt current reference instruction idref, it is considered to multiterminal input photovoltaic parallel in system unity power factor runs, if the idle reference of q axle Current-order iqrefBeing 0, the time-domain expression of PI controller is idref=Kp(Udcref-Udcavg)+Ki∫(Udcref-Udcavg)dt；
(3) watt current i that will obtain in step (1)d, reactive current iqRespectively with the watt current reference in step (2) Instruction idref, idle reference current instruction iqrefDiffering from, and difference inputs PI controller, the time domain through PI controller is expressed Formula calculates d axle cascade connection multi-level DC/AC changer output voltage Ud, q axle cascade connection multi-level DC/AC changer output electricity Pressure Uq, and then obtain modulation voltage v of each DC/AC unit in each phase cascade connection multi-level DC/AC changerai、vbi、vci, i=1, 2 ... the time-domain expression of n, PI controller is Ud=Kp(idref-id)+Ki∫(idref-id) dt, Uq=Kp(iqref-iq)+Ki∫(iqref-iq)dt；
(4) each HVDC terminal voltage U will measured in step (1)dcai, Udcbi, UdcciWith UdcavgError signal warp Cross after proportional controller vai、vbi、vciCompensate according to side-play amount, obtain new modulation voltage vai1、vbi1、vci1, it is ensured that each During photovoltaic array output difference, each DAB high-pressure side dc-voltage balance；
(5) on the basis of step (4), each modulation voltage in each phase cascade connection multi-level DC/AC changer is modified, introduces Zero-sequence component, obtains modulation voltage vai2、vbi2、vci2, three phase power is redistributed, it is ensured that the symmetry of three-phase grid electric current, Realize current balance type control.
With reference to Fig. 3-Fig. 5, for the multiterminal grid-connected structure of input that the present invention proposes, when each photovoltaic battle array in a phase The illuminance of row there are differences, when not using DC voltage to compensate, and each DC terminal voltage operating wave of many level DC/AC changer Shape is as shown in Figure 3.Due to AC multiple DC/AC changer cascade, each cascade module is equal at AC series current. Therefore, when the output difference of each photovoltaic array, each DAB high-pressure side DC voltage can be caused uneven.When using unidirectional current When pressure compensates, each DC terminal voltage work wave of many level DC/AC changer is as shown in Figure 4.Many level DC/AC converts The each DC terminal voltage of device keeps balance, is basically stable at 400V.When output difference between phase and phase, use residual voltage Injection method, it is ensured that each phase grid-connected current symmetrical operation.
The present embodiment demonstrates the effectiveness of multiterminal based on DAB changer input photovoltaic parallel in system power-balance control strategy With feasibility.
Embodiments of the invention are only used for that the present invention is further illustrated, not exhaustive, are not intended that and protect claim The restriction of scope, the enlightenment that those skilled in the art obtain according to embodiments of the present invention, would occur to without creative work Other replacement being substantially equal to, all in scope.

Claims (1)

1. multiterminal based on a DAB changer input photovoltaic parallel in system power-balance control strategy, is characterized in that, its bag Include following steps:
(1) each HVDC terminal voltage U in multiterminal input photovoltaic parallel in system is measureddcai, Udcbi, Udcci, ask for high-pressure side DC voltage average value Udcavg；Measure grid-connected electric current isa, isb, isc, process through Park Transformation and obtain having of d axle component Merit electric current id, reactive current i of q axle componentq；
(2) to follow the trail of DC voltage average value as target, reference value U of a given DC voltage average valuedcref, by direct current Average voltage and UdcrefThe difference of voltage be input in PI controller, the time-domain expression through PI controller calculates one Individual d axle watt current reference instruction idref, it is considered to multiterminal input photovoltaic parallel in system unity power factor runs, if the idle ginseng of q axle Examine current-order iqrefBeing 0, the time-domain expression of PI controller is idref=Kp(Udcref-Udcavg)+Ki∫(Udcref-Udcavg)dt；
(3) watt current i that will obtain in step (1)d, reactive current iqRespectively with the watt current reference in step (2) Instruction idref, idle reference current instruction iqrefDiffering from, and difference inputs PI controller, the time domain through PI controller is expressed Formula calculates d axle cascade connection multi-level DC/AC changer output voltage Ud, q axle cascade connection multi-level DC/AC changer output electricity Pressure Uq, and then obtain modulation voltage v of each DC/AC unit in each phase cascade connection multi-level DC/AC changerai、vbi、vci, i=1, 2 ... the time-domain expression of n, PI controller is Ud=Kp(idref-id)+Ki∫(idref-id) dt, Uq=Kp(iqref-iq)+Ki∫(iqref-iq)dt；
(4) each HVDC terminal voltage U will measured in step (1)dcai, Udcbi, UdcciWith UdcavgError signal warp Cross after proportional controller vai、vbi、vciCompensate according to side-play amount, obtain new modulation voltage vai1、vbi1、vci1, it is ensured that each During photovoltaic array output difference, each DAB high-pressure side dc-voltage balance；
(5) on the basis of step (4), each modulation voltage in each phase cascade connection multi-level DC/AC changer is modified, introduces Zero-sequence component, obtains modulation voltage vai2、vbi2、vci2, three phase power is redistributed, it is ensured that the symmetry of three-phase grid electric current, Realize current balance type control.
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CN106230030A (en) * 2016-09-14 2016-12-14 东北电力大学 Multiterminal input photovoltaic parallel in system power control strategy based on PQ decoupling
CN112803409A (en) * 2021-03-23 2021-05-14 广东电网有限责任公司广州供电局 AC-DC hybrid power grid closed-loop power conversion system based on modular converter

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CN104158212A (en) * 2014-08-06 2014-11-19 电子科技大学 Topological structure of multi-level photovoltaic power generation system and control method of topological structure
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106230030A (en) * 2016-09-14 2016-12-14 东北电力大学 Multiterminal input photovoltaic parallel in system power control strategy based on PQ decoupling
CN106230030B (en) * 2016-09-14 2019-11-22 东北电力大学 Multiterminal based on PQ decoupling input photovoltaic parallel in system power control strategy
CN112803409A (en) * 2021-03-23 2021-05-14 广东电网有限责任公司广州供电局 AC-DC hybrid power grid closed-loop power conversion system based on modular converter

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