CN110544960A - distributed control method for improving reactive power sharing capability of island microgrid - Google Patents
distributed control method for improving reactive power sharing capability of island microgrid Download PDFInfo
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- CN110544960A CN110544960A CN201910898112.6A CN201910898112A CN110544960A CN 110544960 A CN110544960 A CN 110544960A CN 201910898112 A CN201910898112 A CN 201910898112A CN 110544960 A CN110544960 A CN 110544960A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
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- 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
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
Abstract
The invention provides a distributed control method for improving reactive power sharing capacity of an island microgrid, which comprises the following steps: establishing an island microgrid model simulation and control framework thereof based on a droop control principle; in a normal operation scene, a distributed consistency control method is adopted to carry out consistency iteration on reactive power sent by each distributed unit after the island micro-grid stably operates, the operation result of a control algorithm is input into the control of each distributed power inverter, and the reactive power sent by each distributed power inverter is modified, so that the output reactive power of all the inverters reaches the same value. The reactive power sharing of the distributed power supply is realized, so that the voltage quality is improved, and the loss caused by reactive power circulation is restrained; and then, after the reactive power sharing stable output of the micro-grid is achieved, the system load is increased, the control strategy is started again, the disturbance resistance of the control strategy is verified, the reactive power output of each distributed power supply is controlled, and the reactive power sharing of the distributed power supplies is achieved again.
Description
Technical Field
The invention belongs to the field of micro-grid operation control, and particularly relates to a distributed control method for improving reactive power sharing capability of an island micro-grid.
Background
The distributed power generation has the specific advantages of less pollution, local consumption and the like, can effectively solve the problem of non-renewable energy consumption in the power generation process of the power grid, and is one of the important directions of the future power grid development. The micro-grid can effectively manage and realize flexible control of the distributed power supply. The micro-grid can be connected with the large grid for operation and can also be separated from the large grid for independent operation, so that the reliability of the micro-grid operation is greatly improved. But simultaneously, the problems of reactive power sharing of the distributed power supply and the like exist in the operation process.
The microgrid typically employs droop control to effect control of the operation of the distributed power sources in the system. However, droop control also has some defects in terms of reactive power sharing, because the feeder lines of the distributed power supplies are different in length due to natural factors and differences of geographic positions of the connected distributed power supplies, and the feeder line impedances of the distributed power supplies are different. Under the condition that respective impedances of distributed power supplies controlled by droop are inconsistent, reactive power sharing is difficult to achieve, so that some distributed power supplies are overloaded, reactive voltages at all parts of the system are unbalanced, reactive circulating current occurs, and stable operation of the system is influenced. Therefore, the accurate uniform distribution of reactive power is realized, and the key problem of stable operation of the island alternating current micro-grid is to inhibit reactive circulation.
Disclosure of Invention
in order to solve the problem of operation control of an island microgrid, the invention provides a distributed control method for improving reactive power sharing capability of the island microgrid.
In order to achieve the purpose, the invention adopts the following technical scheme:
A distributed control method for improving reactive power sharing capacity of an island microgrid comprises the following steps:
Step 1, establishing an island microgrid control framework
Establishing an island microgrid comprising a distributed power supply, an inverter and corresponding loads thereof, wherein a basic control framework of the island microgrid adopts droop control, and corresponding control parameters are set, so that the microgrid can stably operate in different scenes;
Step 2, controlling the consistency of the reactive power of the distributed power supply
Under the normal operation scene of the microgrid, selecting a time point of stable operation to perform reactive power sharing control on the microgrid, performing distributed communication on each distributed power supply, inputting a reactive power measured value output by each distributed power supply inverter at the time point into a distributed consistency algorithm, inputting a reactive power corrected value obtained by the consistency algorithm into droop control of each distributed power supply inverter, correcting reactive power output, and finally achieving the target of reactive power sharing;
Step 3, controlling the secondary consistency of the distributed power supply under the load disturbance
after the normal operation of the microgrid reaches the reactive power equal-sharing stable operation, increasing the reactive load of the system to cause the load disturbance of the microgrid; because the impedance of each distributed power supply circuit is different, the reactive power output deviation is caused;
And acquiring reactive power output data of each distributed power supply after the system is stabilized, performing distributed consistent iteration on each reactive power data to obtain a reactive power correction value of each distributed power supply under load disturbance, inputting the reactive power output correction value into reactive power control of each distributed power supply to correct the reactive power output, and finally enabling each distributed power supply to be subjected to reactive power sharing again.
Further, in the step 1, the reactive power control improvement is performed on the conventional droop control, as shown in the following formula:
In the formula, fi and Ui are the frequency and voltage amplitude of the ith distributed power supply, f0 is a system frequency reference value, U0 is a voltage reference value, dp and dq are an active frequency droop coefficient and a reactive voltage droop coefficient respectively, Pi and Qi are active and reactive measured values of the ith distributed power supply, and Δ Qi is a reactive compensation value of each ith distributed power supply.
Further, the distributed consistency algorithm in step 2 is:
Wherein ki and kj are the number of communications with the ith and jth communication units; λ is a convergence factor, and the magnitude of λ can determine the speed of system convergence under the same topology, 0< λ < 1. Qi, Qj are the measured values of the ith and jth distributed power supplies, and Δ Qi is the corrected value of the consistency algorithm.
Advantageous effects
1. According to the island microgrid distributed control method, an island microgrid distributed control model is established, a double-layer reactive power control model of a distributed power supply is established, the requirement on system stability is met through primary control, and the reliability of a control strategy is increased through distributed secondary control;
2. the invention provides a distributed control method for improving the reactive power sharing capability of an island microgrid.
Drawings
FIG. 1 is a flow chart of island-oriented microgrid reactive power sharing control according to the invention;
FIG. 2 is a diagram of a pscad simulation system of an island microgrid in an embodiment of the invention;
FIG. 3 is a reactive power curve of an island microgrid during normal operation;
Fig. 4 shows a reactive power curve when reactive load of an island microgrid is increased.
Detailed Description
The present invention will now be described in detail with reference to embodiments. It is to be understood that the following examples are illustrative only, not limiting, and are not intended to limit the scope of the invention.
the first embodiment is as follows:
fig. 1 is a flow chart of islanding-oriented microgrid reactive power sharing control according to the present invention; the embodiment of the distributed control method for improving the reactive power sharing capability of the island microgrid comprises the following steps:
1. control framework for establishing island microgrid
An island micro-grid comprising a distributed power supply, an inverter and corresponding loads is established, a basic control framework of the island micro-grid adopts droop control, and corresponding control parameters are set, so that the micro-grid can stably operate in different scenes. Meanwhile, the traditional droop control is improved in reactive power control, and the reactive power control method is as follows:
in the formula, fi and Ui are the frequency and voltage amplitude of the ith distributed power supply, f0 is a system frequency reference value, U0 is a voltage reference value, dp and dq are an active frequency droop coefficient and a reactive voltage droop coefficient respectively, Pi and Qi are active and reactive measured values of the ith distributed power supply, and Δ Qi is a reactive compensation value of each ith distributed power supply.
2. distributed power supply reactive power consistency control
Under the normal operation scene of the microgrid, selecting a time point of stable operation to perform reactive power sharing control on the microgrid, performing distributed communication on each distributed power supply, inputting a reactive power measured value output by each distributed power supply inverter at the time point into a distributed consistency algorithm, inputting a reactive power corrected value obtained by the consistency algorithm into droop control of each distributed power supply inverter, correcting reactive power output, and finally achieving the target of reactive power sharing. The distributed consistency algorithm is as follows:
wherein ki and kj are the number of communications with the ith and jth communication units; λ is a convergence factor, and the magnitude of λ can determine the speed of system convergence under the same topology, 0< λ < 1. Qi, Qj are the measured values of the ith and jth distributed power supplies, and Δ Qi is the corrected value of the consistency algorithm.
3. Secondary consistency control of distributed power supply under load disturbance
After the normal operation of the micro-grid reaches the reactive power equal-sharing stable operation, the reactive load of the system is increased, so that the micro-grid is disturbed by the load. Reactive power deviation will be caused due to different impedances of the distributed power lines. And acquiring reactive power output data of each distributed power supply after the system is stabilized, performing distributed consistent iteration on each reactive power data to obtain a reactive power correction value of each distributed power supply under load disturbance, inputting the reactive power output correction value into reactive power control of each distributed power supply to correct the reactive power output, and finally enabling each distributed power supply to be subjected to reactive power sharing again.
Example two
the embodiment of the distributed control method for improving the reactive power sharing capability of the island microgrid comprises the following steps:
1. control framework for establishing island microgrid
The built island micro-grid simulation system has the advantages that the rated voltage of the distributed power supply is 220V, the frequency is 50Hz, stable operation of the system can be maintained by adopting droop control, the rated frequency and the voltage are output, and different line impedances are set for the distributed power supplies. As shown in fig. 2, an island microgrid simulation model is established in pscad, the system includes 3 distributed power sources, and each distributed power source in the microgrid adopts droop control.
2. Distributed power supply reactive power consistency control
The established micro-grid simulation model is operated, a control starting time point is selected after stable output (the control is started when 4s is selected in the embodiment), reactive power output by each distributed power supply at the moment is collected, the collected reactive data are iterated by using a distributed consistency algorithm, the iteration result is input into secondary control of droop control to correct reactive power output of the distributed power supplies, 0.1s is set for each iteration, a pscad simulation diagram is shown in fig. 3, and after 5s, each distributed power supply of the micro-grid realizes reactive power sharing.
3. Secondary consistency control of distributed power supply under load disturbance
when t is 6s based on 2, the load of the microgrid increases, the output of each distributed power supply increases, and reactive deviation occurs again due to different distributed power supply line impedances. After the system is stabilized, reactive data of each distributed power supply after load disturbance is collected for 7s, consistency iteration is carried out through a distributed consistency algorithm, the algorithm iteration result is a corresponding reactive correction value, the reactive correction value is input into distributed power supply secondary control, reactive output of each distributed power supply is corrected, a pscad simulation graph is shown in fig. 4, and after 8s, each distributed power supply achieves reactive sharing again. The disturbance resistance of the control strategy is realized.
Claims (3)
1. a distributed control method for improving reactive power sharing capacity of an island microgrid is characterized by comprising the following steps:
Step 1, establishing an island microgrid control framework
Establishing an island microgrid comprising a distributed power supply, an inverter and corresponding loads thereof, wherein a basic control framework of the island microgrid adopts droop control, and corresponding control parameters are set, so that the microgrid can stably operate in different scenes;
step 2, controlling the consistency of the reactive power of the distributed power supply
under the normal operation scene of the microgrid, selecting a time point of stable operation to perform reactive power sharing control on the microgrid, performing distributed communication on each distributed power supply, inputting a reactive power measured value output by each distributed power supply inverter at the time point into a distributed consistency algorithm, inputting a reactive power corrected value obtained by the consistency algorithm into droop control of each distributed power supply inverter, correcting reactive power output, and finally achieving the target of reactive power sharing;
step 3, controlling the secondary consistency of the distributed power supply under the load disturbance
After the normal operation of the microgrid reaches the reactive power equal-sharing stable operation, increasing the reactive load of the system to cause the load disturbance of the microgrid; because the impedance of each distributed power supply circuit is different, the reactive power output deviation is caused;
and acquiring reactive power output data of each distributed power supply after the system is stabilized, performing distributed consistent iteration on each reactive power data to obtain a reactive power correction value of each distributed power supply under load disturbance, inputting the reactive power output correction value into reactive power control of each distributed power supply to correct the reactive power output, and finally enabling each distributed power supply to be subjected to reactive power sharing again.
2. The distributed control method for improving the reactive power sharing capability of an island microgrid according to claim 1, characterized in that in the step 1, a reactive power control improvement is performed on a traditional droop control, as shown in the following formula:
in the formula, fi and Ui are the frequency and voltage amplitude of the ith distributed power supply, f0 is a system frequency reference value, U0 is a voltage reference value, dp and dq are an active frequency droop coefficient and a reactive voltage droop coefficient respectively, Pi and Qi are active and reactive measured values of the ith distributed power supply, and Δ Qi is a reactive compensation value of each ith distributed power supply.
3. The distributed control method for improving the reactive power sharing capability of the island microgrid of claim 1,
The distributed consistency algorithm in the step 2 is as follows:
Wherein ki and kj are the number of communications with the ith and jth communication units; λ is a convergence factor, and the magnitude of λ can determine the speed of system convergence under the same topology, 0< λ < 1. Qi, Qj are the measured values of the ith and jth distributed power supplies, and Δ Qi is the corrected value of the consistency algorithm.
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