CN113488984B - Secondary control method and controller for guaranteeing stable operation of direct-current micro-grid - Google Patents

Secondary control method and controller for guaranteeing stable operation of direct-current micro-grid Download PDF

Info

Publication number
CN113488984B
CN113488984B CN202110837323.6A CN202110837323A CN113488984B CN 113488984 B CN113488984 B CN 113488984B CN 202110837323 A CN202110837323 A CN 202110837323A CN 113488984 B CN113488984 B CN 113488984B
Authority
CN
China
Prior art keywords
current
controller
voltage
error
direct
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN202110837323.6A
Other languages
Chinese (zh)
Other versions
CN113488984A (en
Inventor
王燕舞
张宇
刘骁康
肖江文
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Huazhong University of Science and Technology
Original Assignee
Huazhong University of Science and Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Huazhong University of Science and Technology filed Critical Huazhong University of Science and Technology
Priority to CN202110837323.6A priority Critical patent/CN113488984B/en
Publication of CN113488984A publication Critical patent/CN113488984A/en
Application granted granted Critical
Publication of CN113488984B publication Critical patent/CN113488984B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H02J1/102—Parallel operation of dc sources being switching converters
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P80/00—Climate change mitigation technologies for sector-wide applications
    • Y02P80/10—Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier
    • Y02P80/14—District level solutions, i.e. local energy networks

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a secondary control method and a controller for ensuring stable operation of a direct-current micro-grid, and belongs to the field of regulation and control of multi-power-supply-end direct-current micro-grids. The method comprises the following steps: acquiring the rated voltage of a direct current micro-grid bus, the output voltage and the output current of each direct current converter, and calculating the unit current of the direct current micro-grid during stable operation; calculating a voltage error and a current error; calculating a comprehensive error; calculating the intermediate state of the controller; and integrating the intermediate state to obtain a secondary control signal, and outputting the secondary control signal to the droop controller. According to the invention, only the current and voltage signals output by the local converter need to be acquired, and the information of the neighbor node and the bus voltage value are not needed, so that the communication burden is greatly reduced; and the convergence time of the current and the voltage in the microgrid is only regulated by a single parameter and can be preset, so that the convergence time can be flexibly adjusted by regulating the control parameter.

Description

Secondary control method and controller for guaranteeing stable operation of direct-current micro-grid
Technical Field
The invention belongs to the field of regulation and control of a multi-power-supply-end direct-current micro-grid, and particularly relates to a secondary control method and a controller for guaranteeing stable operation of a direct-current micro-grid.
Background
With the popularization of distributed power generation devices and energy storage equipment, micro-grids gradually enter people's lives. The direct-current microgrid is suitable for various application scenes due to the advantages of small power conversion loss, no need of considering reactive power and voltage phase control problems and the like, so that the design of a control method for ensuring the stable operation of the direct-current microgrid is very important. Droop control is generally applied to the control problem of a microgrid as a distributed efficient control strategy, but has the defects of bus voltage deviation and insufficient current sharing precision. Therefore, on the basis of droop control, secondary control is introduced to compensate droop control errors, and power of a micro-grid power supply end is reasonably distributed through tertiary control planning. The realization of voltage regulation and current sharing of a microgrid based on secondary control is a current research hotspot, but how to ensure the convenience of implementation of a controller and the rapidity of system convergence is a difficult problem. Therefore, a secondary controller which does not need to acquire neighbor node information and bus voltage and can ensure rapid convergence of the system is designed, and the secondary controller is particularly important for stable operation of the micro-grid.
Patent CN112713581A discloses a distributed fixed-time voltage regulation and current equalization method and system for a dc microgrid, which has the main ideas: obtaining an intermediate state based on interaction of secondary control signals of a local converter and a neighbor converter by establishing a sparse communication network between the converters; designing a state estimation input based on the sign function of the intermediate state and the fractional exponential power thereof; integrating the state estimation input to obtain an internal state; obtaining an updated secondary control signal based on the interaction of the internal states of the local converter and the neighbor converter; adding the updated secondary control signal to the droop control to obtain an updated voltage reference value; obtaining an updated output voltage through the internal control, thereby obtaining an updated bus voltage; until the bus voltage is stable, each converter outputs current sharing at the same time, bus voltage information is not needed, and the system can realize stability in a fixed time irrelevant to the initial state of the system. However, it has the following drawbacks: the implementation of the controller needs to obtain the information of the neighbor nodes, so that the communication load is increased, and the energy in the aspect of communication is consumed; and the convergence time is limited by the physical network of the system, and the adjustment is not flexible.
Disclosure of Invention
Aiming at the defects and improvement requirements of the prior art, the invention provides a secondary control method and a controller for ensuring the stable operation of a direct-current micro-grid, aiming at realizing the regulation of the bus voltage and the accurate proportion of the output current of a converter in a preset time by a system without acquiring the bus voltage and the information of neighbor nodes, and effectively ensuring the convenience of implementing secondary control and the rapidity of system convergence.
To achieve the above object, according to a first aspect of the present invention, there is provided a two-stage control method for ensuring stable operation of a dc microgrid, a plurality of dc converters being connected in parallel to a microgrid bus, the method comprising:
s1, obtaining rated voltage V of direct current micro-grid bus*Output voltage and output current V of each DC converteriAnd IiAnd calculating the unit current of the direct current micro-grid during stable operation
Figure BDA0003177613350000021
S2, calculating voltage error
Figure BDA0003177613350000022
And current error
Figure BDA0003177613350000023
S3, calculating the comprehensive error
Figure BDA0003177613350000024
S4, calculating the intermediate state of the controller
Figure BDA0003177613350000025
S5, for the intermediate state deltai(t) integrating to obtain a secondary control signal ui(t) outputting to the corresponding droop controller;
where i is 1, …, N is the number of dc converters, diIs the current-sharing coefficient, v, of the DC converter>0 is a constant, epsilon is the convergence time upper bound of the output current and voltage of the converter in the micro-grid, sigma is the convergence time adjustment coefficient, epsilon>0 and 0<σ<1 is a secondary control parameter, #i(0)＝ψi0，ψi0In order to be the initial error of the system,
Figure BDA0003177613350000026
sign (·) is a sign function.
Preferably, the first and second electrodes are formed of a metal,
Figure BDA0003177613350000031
the calculation formula of (a) is as follows:
Figure BDA0003177613350000032
wherein iLIs the total load current in the direct-current microgrid,
Figure BDA0003177613350000033
is the sum of the current sharing coefficients of the DC converter.
Preferably, IL＝V*R, R is the total load resistance of the microgrid, ILAnd d are both provided by a three stage controller.
To achieve the above object, according to a second aspect of the present invention, there is provided a secondary controller for ensuring stable operation of a dc microgrid, comprising: a computer-readable storage medium and a processor;
the computer-readable storage medium is used for storing executable instructions;
the processor is configured to read an executable instruction stored in the computer-readable storage medium, and execute the secondary control method for guaranteeing the stable operation of the dc micro-grid according to the first aspect.
To achieve the above object, according to a third aspect of the present invention, there is provided a dc converter controller for ensuring stable operation of a dc microgrid, the dc converter controller comprising from front to back: a three stage controller, a two stage controller as described in the second aspect, a droop controller, a dual closed loop PI controller and a PWM generator.
Preferably, the droop coefficient of the droop controller satisfies mi＝v/di。
Preferably, the secondary control signal u is updated by means of a converteriAnd (t) until the voltage error and the current error converge to 0.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
(1) compared with the existing two-stage control method, the method only needs to collect the output current and voltage signals of the local converter when acquiring the comprehensive error, and does not need the information of the neighbor node and the bus voltage value, thereby greatly lightening the communication burden.
(2) Compared with the existing secondary controller which is designed based on a fixed time dynamic average consistency method, the secondary controller is designed based on a preset time control method, and the convergence time of the current and the voltage in the microgrid is only regulated by a single parameter and can be preset, so that the convergence time can be flexibly adjusted by regulating the control parameter.
Drawings
FIG. 1 is a diagram of the ith DC/DC converter connected to a DC bus and its hierarchical control architecture;
fig. 2 is a diagram of a two-stage control structure of the preset time according to 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.
Step 1: aiming at the multi-power-supply-end direct-current microgrid, a control model is established, and a control target is provided.
The schematic diagram of the control structure of the direct current microgrid is shown in fig. 1. The plurality of direct current converters are connected with the micro-grid bus in parallel, and the physical characteristics are as follows: distributed power generation equipment supply voltage Vs，ViAnd IiRespectively, the output voltage and the output current of the ith DC/DC converter. Reference voltage V transmitted to double closed loop PI controller by droop controli refAn interface is provided for regulating the entire dc microgrid. The reference voltage is designed as follows:
Vi ref(t)＝V*-miIi(t)+ui(t)
wherein, V*Is rated voltage of a direct current micro-grid bus, miFor the droop control coefficient to be determined in step 2, uiAnd (t) is a secondary control signal. Because the double closed loop PI controller can make the output voltage of the converter track to the reference value thereof quickly, namely: vi(t)＝Vi ref(t), the ith converter output voltage is expressed as follows:
Vi(t)＝V*-miIi(t)+ui(t)
for such a multi-supply-end direct-current microgrid, the control target thereof comprises two parts: 1) regulating and controlling the output voltage of the converter to be maintained at a rated value of the bus voltage; 2) the output current of the N converters is guaranteed to be distributed in proportion, namely:
Figure BDA0003177613350000051
wherein i is 1, …, N, di、djAre the scaling coefficients of the i and j inverter output currents.
Step 2: and establishing a comprehensive error according to the current error and the voltage error.
Defining unit current according to converter output current and its proportionality coefficient
Figure BDA0003177613350000052
According to the above definition and the control target of the microgrid, the voltage error and the current error are established as follows:
Figure BDA0003177613350000053
wherein
Figure BDA0003177613350000054
For the system steady state unit current, it will be determined in step 3.
Figure BDA0003177613350000055
And
Figure BDA0003177613350000056
the voltage error and the current error of the ith converter are respectively. According to
Figure BDA0003177613350000057
And
Figure BDA0003177613350000058
defining composite error
Figure BDA0003177613350000059
Wherein v is>0 is a constant, and v ═ midiDetermining the droop coefficient mi. Therefore, the definition of the comprehensive error does not need the information of the neighbor node and the bus voltage, and only needs to collect the local voltage ViAnd current IiA signal. According to the above-mentioned comprehensive error psiiIf is defined asi＝0,
Figure BDA00031776133500000510
Namely, the method comprises the following steps:
Figure BDA00031776133500000511
and is
Figure BDA00031776133500000512
If it is psii＝0,
Figure BDA00031776133500000513
The microgrid achieves the control targets of voltage regulation and current sharing.
And step 3: and designing a secondary control strategy of the preset time to obtain the preset time convergence of the comprehensive error.
As shown in fig. 2, the pre-timing secondary controller uses sign functions sign (), k (), and the total error ψiAnd an integration link. Two-stage control signal ui(t) is represented by the following formula:
Figure BDA00031776133500000514
wherein epsilon>0 and 0<σ<1 is a secondary control parameter, #i0Is a systematic initial error, and
Figure BDA00031776133500000515
the specific operation steps are as follows:
(1) obtaining V according to the operation state of the micro-grid*And with
Figure BDA00031776133500000516
Wherein the content of the first and second substances,
Figure BDA00031776133500000517
is solved as follows:
Figure BDA0003177613350000061
wherein, IL＝V*the/R is the total load current in the direct-current micro-grid, the R is the total load resistance of the micro-grid,
Figure BDA0003177613350000062
is the sum of the proportionality coefficients of the output currents of the converters, ILAnd d are both provided by three-level control signals;
(2) collecting output voltage V of local converteriAnd an output current IiSignal, binding V*And
Figure BDA0003177613350000063
calculating a voltage error
Figure BDA0003177613350000064
Error with current
Figure BDA0003177613350000065
According to
Figure BDA0003177613350000066
And
Figure BDA0003177613350000067
calculating the composite error psii；
(3) Will synthesize the error psiiSubstituting into the expression of the secondary controller with preset time to obtain the intermediate state deltai(t)；
(4) To intermediate state deltai(t) integration to obtain a secondary control signal ui(t)；
(5) Updating secondary control signal u using a converteri(t) repeating steps (1) - (4) until the voltage error is reached
Figure BDA0003177613350000068
Error with current
Figure BDA0003177613350000069
Converge to 0.
The designed secondary controller can realize the convergence of the voltage error and the current error within the preset time T, namely
Figure BDA00031776133500000610
And 4, step 4: and analyzing the accurate ratio of the bus voltage regulation and the converter output current in the preset time of the direct-current micro-grid.
Due to the fact that
Figure BDA00031776133500000611
The target of preset time pressure regulation can be realized:
Figure BDA00031776133500000612
due to the fact that
Figure BDA00031776133500000613
The current sharing target in preset time can be realized:
Figure BDA00031776133500000614
the upper bound T of the convergence time of the converter output voltage and current is ═ epsilon, where epsilon is a controller parameter and can be preset.
The invention designs the comprehensive error based on the current error and the voltage error, the design of the error only needs to collect the local current and voltage information, but does not need the current and bus voltage information of the neighbor node, and the communication burden is reduced. By using a preset time secondary control strategy, the convergence time upper bound T of the current and the voltage of the microgrid is equal to epsilon, and the convergence time can be flexibly regulated and controlled by adjusting a single parameter epsilon. The secondary control strategy of the preset time effectively ensures the convenience of secondary control implementation and the rapidity of system convergence, and provides guarantee for the stable operation of the direct-current micro-grid.
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 (5)

1. A secondary control method for ensuring stable operation of a direct current micro-grid is characterized in that a plurality of direct current converters are connected with a micro-grid bus in parallel, and the method comprises the following steps:
s1, acquiring rated voltage V of bus of direct-current microgrid*Output voltage and output current V of each DC converteriAnd IiAnd calculating the unit current of the direct current micro-grid during stable operation
Figure FDA0003573134980000011
The calculation formula is as follows:
Figure FDA0003573134980000012
wherein, ILIs the total load current in the direct-current microgrid,
Figure FDA0003573134980000013
is the sum of the current sharing coefficients of the DC converter;
s2, calculating voltage error
Figure FDA0003573134980000014
And current error
Figure FDA0003573134980000015
S3, calculating the comprehensive error
Figure FDA0003573134980000016
S4, calculating the intermediate state of the controller
Figure FDA0003573134980000017
S5, for the intermediate state deltai(t) integrating to obtain a secondary control signal ui(t) outputting to the corresponding droop controller;
s6, updating the secondary control signal ui(t) until the voltage error and the current error converge to 0;
where i 1.. ang, N is the number of dc converters, diIs a current-sharing coefficient of the DC converter, v is more than 0 and is a constant, epsilon is the upper bound of the convergence time of the output current and voltage of the converter in the micro-grid, sigma is a convergence time regulating coefficient, epsilon is more than 0 and less than 1 are two-stage control parameters, psii(0)＝ψi0，ψi0In order to be the initial error of the system,
Figure FDA0003573134980000018
sign (·) is a sign function.
2. The method of claim 1, wherein I isL＝V*R, R is the total load resistance of the microgrid, ILAnd d are both provided by a three-level controller.
3. The utility model provides a guarantee direct current little electric wire netting steady operation's secondary controller which characterized in that includes: a computer-readable storage medium and a processor;
the computer-readable storage medium is used for storing executable instructions;
the processor is used for reading the executable instructions stored in the computer-readable storage medium and executing the secondary control method for guaranteeing the stable operation of the direct current micro-grid according to claim 1 or 2.
4. A controller for a dc converter for ensuring stable operation of a dc microgrid, the controller comprising from front to back: a three level controller, a two level controller as claimed in claim 3, a droop controller, a dual closed loop PI controller and a PWM generator.
5. The controller of a dc converter of claim 4, wherein the droop coefficient of the droop controller satisfies mi＝v/di。
CN202110837323.6A 2021-07-23 2021-07-23 Secondary control method and controller for guaranteeing stable operation of direct-current micro-grid Active CN113488984B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202110837323.6A CN113488984B (en) 2021-07-23 2021-07-23 Secondary control method and controller for guaranteeing stable operation of direct-current micro-grid

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202110837323.6A CN113488984B (en) 2021-07-23 2021-07-23 Secondary control method and controller for guaranteeing stable operation of direct-current micro-grid

Publications (2)

Publication Number Publication Date
CN113488984A CN113488984A (en) 2021-10-08
CN113488984B true CN113488984B (en) 2022-05-17

Family

ID=77943327

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110837323.6A Active CN113488984B (en) 2021-07-23 2021-07-23 Secondary control method and controller for guaranteeing stable operation of direct-current micro-grid

Country Status (1)

Country Link
CN (1) CN113488984B (en)

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102015109967A1 (en) * 2015-06-22 2016-12-22 Gip Ag Device and method for bidirectionally connecting two power grids
CN108493465B (en) * 2018-04-08 2020-12-08 华中科技大学 Mixed energy control system and control method of solid oxide fuel cell
US11462911B2 (en) * 2019-04-09 2022-10-04 Smart Wires Inc. Detection and mitigation of DC injection on the power grid system
CN112713581B (en) * 2020-12-17 2022-08-05 华中科技大学 Distributed fixed-time voltage regulation and current equalization method and system for direct-current micro-grid

Also Published As

Publication number Publication date
CN113488984A (en) 2021-10-08

Similar Documents

Publication Publication Date Title
CN110011296B (en) Direct-current micro-grid distributed droop control method based on active disturbance rejection control technology
Papadimitriou et al. Review of hierarchical control in DC microgrids
Li et al. An improved coordination control for a novel hybrid AC/DC microgrid architecture with combined energy storage system
CN106961101B (en) One kind having multistage generatrix voltage compensation direct-current micro-grid modified multi slope droop control method
CN110707680B (en) Direct-current micro-grid power accurate distribution and bus voltage deviation optimization control method
CN110365004B (en) Power distribution control method for direct-current micro-grid
CN110867848B (en) Energy management prediction control method for direct-current micro-grid community
Hossain et al. Real-time distributed coordination of power electronic converters in a DC shipboard distribution system
CN112436501B (en) Improved balance control method for multiple energy storage units of direct-current micro-grid
CN116915048A (en) Loop controller, system, method and storage medium for three-level DC-DC converter
CN110556816B (en) Composite droop control method and system suitable for direct-current micro-grid
CN111525702A (en) Distributed prediction cubic control method for direct-current micro-grid cluster
CN112713581B (en) Distributed fixed-time voltage regulation and current equalization method and system for direct-current micro-grid
Mohamed et al. Droop control design to minimize losses in DC microgrid for more electric aircraft
CN109639153B (en) Model prediction control method of Quasi-Z source indirect matrix converter
He et al. A two-layer dynamic voltage regulation strategy for DC distribution networks with distributed energy storages
CN113488984B (en) Secondary control method and controller for guaranteeing stable operation of direct-current micro-grid
Riar et al. Energy management of a microgrid: Compensating for the difference between the real and predicted output power of photovoltaics
CN115085557A (en) Multi-module direct current converter power balancing method based on model predictive control
Dai et al. Direct power based control strategy for DAB DC-DC converter with cooperative triple phase shifted modulation
CN112953290A (en) Robust control method for parallel inverter system in island microgrid
Mahmoudian et al. Adaptive power-sharing strategy in hybrid AC/DC microgrid for enhancing voltage and frequency regulation
Cheng et al. Distributed control for multiple hybrid energy storage systems using consensus algorithm in direct current power supply system
CN107196541A (en) Power conversion system is pressed in the three-phase applied for closed loop
Sondhi et al. Primary control in DC microgrids: A review

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant