CN112186816A - Method for improving dynamic performance of photovoltaic microgrid by using novel droop reactive compensation control - Google Patents
Method for improving dynamic performance of photovoltaic microgrid by using novel droop reactive compensation control Download PDFInfo
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- CN112186816A CN112186816A CN202011017207.1A CN202011017207A CN112186816A CN 112186816 A CN112186816 A CN 112186816A CN 202011017207 A CN202011017207 A CN 202011017207A CN 112186816 A CN112186816 A CN 112186816A
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- droop
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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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- 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
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
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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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
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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
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- Control Of Electrical Variables (AREA)
Abstract
The invention discloses a method for improving dynamic performance of a photovoltaic microgrid by utilizing novel droop reactive compensation control, which comprises the following steps: establishing an active equation and a reactive equation output by a single photovoltaic power supply point inverter; the active equation and the reactive equation output by a single photovoltaic power supply point inverter are simplified; according to the active and reactive simplified equation output by the single photovoltaic power supply point inverter, simulating the droop external characteristic of the synchronous generator to establish a droop reactive compensation control equation; improving the droop reactive compensation coefficient, and automatically adjusting the droop coefficient according to the pressure difference to obtain a novel droop reactive compensation coefficient; the novel droop reactive compensation coefficient is applied to the droop reactive compensation control equation, and the purpose of improving the dynamic performance of droop reactive compensation control of the photovoltaic micro-grid is achieved. The invention modifies the fixed droop coefficient into a novel dynamic droop coefficient which is automatically adjusted according to the voltage deviation, reduces the reactive compensation range and reduces the influence on the system.
Description
Technical Field
The invention relates to a method for improving dynamic performance of a photovoltaic microgrid by utilizing novel droop reactive compensation control, which is used for reducing the reactive compensation adjusting range of a photovoltaic microgrid grid-connected inverter, further reducing voltage deviation, improving dynamic performance and power supply reliability of the photovoltaic microgrid and improving the utilization rate of each power supply point in the photovoltaic microgrid.
Background
In an ac microgrid system formed by photovoltaic, an inverter is connected to a large power grid through a common connection point, and droop control is generally adopted to maintain power balance and voltage stability of a photovoltaic power supply point, wherein the voltage stability is realized through reactive compensation. In a photovoltaic microgrid practical system, the electric equipment is disconnected due to the fact that voltage is adjusted too much.
Disclosure of Invention
The invention aims to provide a method for improving the dynamic performance of a photovoltaic microgrid by utilizing novel droop reactive compensation control, aiming at the problem of large voltage range caused by overlarge reactive increase and decrease range in the traditional droop reactive power regulation process. According to the method, a photovoltaic micro-grid power mathematical expression is established by establishing a photovoltaic power supply point Thevenin equivalent model. In order to realize reactive compensation control of the grid-connected inverter, droop reactive compensation control equations are established by simulating droop external characteristics of the synchronous generator. The invention modifies the fixed droop coefficient into a novel dynamic droop coefficient which is automatically adjusted according to the voltage deviation, reduces the reactive compensation range and reduces the influence on the system.
The invention is realized by adopting the following technical scheme:
a method for improving dynamic performance of a photovoltaic microgrid by utilizing novel droop reactive compensation control comprises the following steps:
1) establishing an active equation and a reactive equation output by a single photovoltaic power supply point inverter;
2) simplifying the active equation and the reactive equation output by the single photovoltaic power point inverter in the step 1);
3) according to the active and reactive simplified equations output by the single photovoltaic power point inverter in the step 2), simulating the droop external characteristic of the synchronous generator to establish a droop reactive compensation control equation;
4) improving the droop reactive compensation coefficient in the step 3), and automatically adjusting the droop coefficient according to the pressure difference to obtain a novel droop reactive compensation coefficient;
5) and (4) applying the novel droop reactive compensation coefficient obtained in the step 4) to a droop reactive compensation control equation to achieve the purpose of improving the droop reactive compensation control dynamic performance of the photovoltaic micro-grid.
The further improvement of the invention is that in the step 1), the inverter output active and reactive equations of a single photovoltaic power supply point are established as follows:
wherein: piOutputting active power for the photovoltaic inverter; qiOutputting reactive power for the photovoltaic inverter; u shapeiOutputting a voltage for the photovoltaic inverter; u shape0Is the voltage across the load impedance;iworking angle is used; zi＝Ri+JXiIs the line equivalent impedance; riIs a line resistance; xiIs a line inductive reactance.
The further improvement of the invention is that the specific implementation method of the step 2) is as follows: simplifying the active equation and the reactive equation output by the single photovoltaic power point inverter in the step 1):
this is because in the photovoltaic microgrid, the impedance of the photovoltaic power equivalent transmission line is resistive, that is, Ri＞＞Xi，Ri≈Zi，XiAbout 0, power anglei→0。
The further improvement of the invention is that the specific implementation method of the step 3) is as follows: according to the simplified equation of active power and reactive power output by the single photovoltaic power point inverter in the step 2),simulating the droop external characteristic of the synchronous generator to establish a droop reactive compensation control equation: u shapei＝U0-nQiWherein: u shapeiIs the amplitude of the output voltage of the controlled inverter; u shape0Is a no-load output voltage amplitude reference value; n is the reactive power droop coefficient; qiIs the reactive power of the load distribution.
The further improvement of the invention is that the specific implementation method of the step 4) is as follows: improving the droop reactive compensation coefficient in the step 3), and obtaining a novel droop reactive compensation coefficient according to the pressure difference automatic adjustment droop coefficient:
wherein: n isiThe droop reactive compensation coefficient is a novel droop reactive compensation coefficient; u shapemax、UminThe upper limit and the lower limit of the threshold value of the voltage amplitude are set; the others are defined as above formula; when U-U0If the voltage is adjusted to be positive, the molecular coefficient is selected to be Umax-U0(ii) a When U-U0Less than or equal to 0, namely when the regulated voltage is negative, selecting Umin-U0(ii) a When facing U1→U2The linear droop reactive compensation control reactive adjustment amount is delta Q1。
The further improvement of the invention is that the concrete implementation method of the step 5) is as follows: applying the novel droop reactive compensation coefficient in the step 4) to a droop reactive compensation control equation, and establishing the novel droop reactive compensation control equation: u shapei＝U0-niQiAnd the purpose of improving the droop reactive compensation control dynamic performance of the photovoltaic micro-grid is achieved.
Compared with the prior art, the invention has at least the following beneficial technical effects:
according to the photovoltaic microgrid droop reactive compensation control method, the fixed droop coefficient is replaced by the novel dynamic droop coefficient, the droop coefficient is automatically adjusted according to the voltage deviation, the reactive compensation range is reduced, the voltage adjustment amount can be reduced through simulation verification, the voltage adjustment can be maintained within a set small offset range, the steady state voltage deviation is eliminated, and the utilization rate of each power supply point in the photovoltaic microgrid is improved.
Drawings
Fig. 1 is a photovoltaic microgrid topology diagram;
fig. 2 is a micro-grid thevenin equivalent circuit diagram with double photovoltaic power supply points;
FIG. 3 is a schematic diagram of reactive compensation for linear droop;
FIG. 4 is a graph comparing droop control curves;
fig. 5 is a control block diagram of a photovoltaic microgrid employing novel droop control;
FIG. 6 is a simulated waveform of reactive power distribution for system reactive power increase using conventional droop reactive power compensation control;
fig. 7 shows reactive power distribution simulation waveforms for system reactive power increase and control by adopting novel droop reactive power compensation.
Detailed Description
The technical solution of the present invention is further described in detail by the accompanying drawings.
As shown in fig. 1, in a photovoltaic microgrid topology having two photovoltaic power supply points (simplified): the photovoltaic power supply point is a photovoltaic array; rn+jXnIs the equivalent line impedance; the inverter is connected to the large grid and the load via a Point of Common Coupling (PCC).
As shown in fig. 2, in the equivalent circuit diagram of the photovoltaic microgrid thevenin including two photovoltaic power supply points: u shape1∠1、U2∠2Outputting voltage for the grid-connected inverters of the photovoltaic power supply point 1 and the photovoltaic power supply point 2; p1、P2、Q1、Q2Outputting active power and reactive power for the grid-connected inverters of the photovoltaic power supply point 1 and the photovoltaic power supply point 2; u shape0The angle 0 is the load impedance terminal voltage; zloadIs the load equivalent impedance.
The single photovoltaic power point inverter output P, Q is:
in the photovoltaic microgrid, the impedance of an equivalent power transmission line of a photovoltaic power supply point is resistive (R)i＞＞Xi，Ri≈Zi，XiAbout 0, power anglei→ 0), the above equation can be simplified to:
as shown in fig. 3, the linear droop control is a differential regulation, and as can be known from equation (2), the active power output of the single photovoltaic power supply point inverter of the photovoltaic microgrid is related to the power angle, and the reactive power output is related to the voltage. In order to realize reactive compensation control of the grid-connected inverter, droop reactive compensation control is realized by simulating droop external characteristics of the synchronous generator, and a control equation is as follows:
Ui＝U0-nQi (3)
in the formula: u shapeiIs the amplitude of the output voltage of the controlled inverter; u shape0Is a no-load output voltage amplitude reference value; n is the reactive power droop coefficient; qiIs the reactive power of the load distribution.
As shown in fig. 4, in the linear droop reactive compensation control, the droop coefficient k is a fixed value, and the reactive compensation and the voltage regulation are in a linear relationship, in an actual system of the photovoltaic microgrid, some electrical devices are sensitive to voltage fluctuation, and when the voltage is regulated in a large range, the problem of equipment disconnection is easily caused. The invention provides a novel droop control scheme, wherein a droop coefficient is automatically adjusted to reduce a reactive compensation range, and can be expressed as follows:
in the formula: n isiThe droop reactive compensation coefficient is a novel droop reactive compensation coefficient; u shapemax、UminThe upper limit and the lower limit of the threshold value of the voltage amplitude are set; the others are as defined above. When U-U0> 0, i.e. the regulating voltage is positiveMolecular coefficient of choice Umax-U0(ii) a When U-U0Less than or equal to 0, namely when the regulated voltage is negative, selecting Umin-U0。
When facing U1→U2The linear droop reactive compensation control reactive adjustment amount is delta Q1. By adopting the novel droop reactive compensation control provided by the text, the droop coefficient n of the reactive compensationiThe reactive power regulating quantity is delta Q when the difference value between the current voltage and the target voltage changes and changes in real time2(ΔQ2＜ΔQ1) And the reactive compensation range is reduced, and the influence on the system is less.
As shown in fig. 5, in order to verify the effectiveness of the novel droop reactive compensation control scheme of the present invention. A photovoltaic microgrid simulation model containing two photovoltaic power supply points is built under Matlab/Simulink, the dynamic reactive compensation droop coefficient provided by the invention is introduced into droop control of a photovoltaic microgrid grid-connected inverter, and simulation parameters are as shown in the following table.
TABLE 1 photovoltaic microgrid line parameters
As shown in fig. 6, when the PCC is subjected to a load increasing condition at 0.6s, the voltage of the bus is reduced from 10kV to 8.3kV after 0.07s, the steady-state voltage deviation is large and the voltage fluctuation is obvious, and the minimum voltage is reduced to 6.7kV, which is very likely to cause some electrical devices to stop operating due to undervoltage protection.
As shown in fig. 7, under the same reactive power increasing condition of 0.6s, the voltage of the bus is restored from 10kV to 9.9kV through 0.04s, the steady-state voltage deviation is small, the voltage fluctuation is small, and the fluctuation is reduced to 8.8kV at the minimum, because the voltage regulation amount is reduced by the novel droop control, the voltage regulation can be maintained in the set small offset range, the steady-state voltage deviation is eliminated, and the utilization rate of each power supply point in the photovoltaic microgrid is improved.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.
Claims (6)
1. A method for improving dynamic performance of a photovoltaic microgrid by utilizing novel droop reactive compensation control is characterized by comprising the following steps:
1) establishing an active equation and a reactive equation output by a single photovoltaic power supply point inverter;
2) simplifying the active equation and the reactive equation output by the single photovoltaic power point inverter in the step 1);
3) according to the active and reactive simplified equations output by the single photovoltaic power point inverter in the step 2), simulating the droop external characteristic of the synchronous generator to establish a droop reactive compensation control equation;
4) improving the droop reactive compensation coefficient in the step 3), and automatically adjusting the droop coefficient according to the pressure difference to obtain a novel droop reactive compensation coefficient;
5) and (4) applying the novel droop reactive compensation coefficient obtained in the step 4) to a droop reactive compensation control equation to achieve the purpose of improving the droop reactive compensation control dynamic performance of the photovoltaic micro-grid.
2. The method for improving the dynamic performance of the photovoltaic microgrid by using the novel droop reactive compensation control as claimed in claim 1, wherein in step 1), the inverter output active and reactive equations of a single photovoltaic power supply point are established as follows:
wherein: piOutputting active power for the photovoltaic inverter; qiOutputting reactive power for the photovoltaic inverter; u shapeiOutputting a voltage for the photovoltaic inverter; u shape0Is the voltage across the load impedance;iworking angle is used; zi＝Ri+JXiIs the line equivalent impedance; riIs a line resistance; xiIs a line inductive reactance.
3. The method for improving the dynamic performance of the photovoltaic microgrid by using the novel droop reactive compensation control as claimed in claim 2, wherein the specific implementation method of the step 2) is as follows: simplifying the active equation and the reactive equation output by the single photovoltaic power point inverter in the step 1):
this is because in the photovoltaic microgrid, the impedance of the photovoltaic power equivalent transmission line is resistive, that is, Ri＞＞Xi，Ri≈Zi，XiAbout 0, power anglei→0。
4. The method for improving the dynamic performance of the photovoltaic microgrid by using the novel droop reactive compensation control as claimed in claim 3, wherein the specific implementation method of the step 3) is as follows: according to the active and reactive simplified equation output by the single photovoltaic power point inverter in the step 2), simulating the droop external characteristic of the synchronous generator to establish a droop reactive compensation control equation: u shapei＝U0-nQiWherein: u shapeiIs the amplitude of the output voltage of the controlled inverter; u shape0Is a no-load output voltage amplitude reference value; n is the reactive power droop coefficient; qiIs the reactive power of the load distribution.
5. The method for improving the dynamic performance of the photovoltaic microgrid by using the novel droop reactive compensation control as claimed in claim 4, wherein the specific implementation method of the step 4) is as follows: improving the droop reactive compensation coefficient in the step 3), and obtaining a novel droop reactive compensation coefficient according to the pressure difference automatic adjustment droop coefficient:
wherein: n isiThe droop reactive compensation coefficient is a novel droop reactive compensation coefficient; u shapemax、UminThe upper limit and the lower limit of the threshold value of the voltage amplitude are set; the others are defined as above formula; when U-U0If the voltage is adjusted to be positive, the molecular coefficient is selected to be Umax-U0(ii) a When U-U0Less than or equal to 0, namely when the regulated voltage is negative, selecting Umin-U0(ii) a When facing U1→U2The linear droop reactive compensation control reactive adjustment amount is delta Q1。
6. The method for improving the dynamic performance of the photovoltaic microgrid by using the novel droop reactive compensation control as claimed in claim 5, wherein the specific implementation method of the step 5) is as follows: applying the novel droop reactive compensation coefficient in the step 4) to a droop reactive compensation control equation, and establishing the novel droop reactive compensation control equation: u shapei＝U0-niQiAnd the purpose of improving the droop reactive compensation control dynamic performance of the photovoltaic micro-grid is achieved.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113725923A (en) * | 2021-10-08 | 2021-11-30 | 湖南工业大学 | Photovoltaic micro-grid system active power sharing control method based on self-adaptive droop |
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| WO2006126003A1 (en) * | 2005-05-25 | 2006-11-30 | Cummins Generator Technologies Limited | Control system |
| CN103501021A (en) * | 2013-10-28 | 2014-01-08 | 南京工程学院 | Inverter droop control method capable of achieving secondary frequency modulation and pressure regulation |
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2020
- 2020-09-24 CN CN202011017207.1A patent/CN112186816A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006126003A1 (en) * | 2005-05-25 | 2006-11-30 | Cummins Generator Technologies Limited | Control system |
| CN103501021A (en) * | 2013-10-28 | 2014-01-08 | 南京工程学院 | Inverter droop control method capable of achieving secondary frequency modulation and pressure regulation |
Non-Patent Citations (1)
| Title |
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| 谢楠等: "应用抗扰动观测器的微网改进下垂无功补偿技术", 《电力系统及其自动化学报》 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113725923A (en) * | 2021-10-08 | 2021-11-30 | 湖南工业大学 | Photovoltaic micro-grid system active power sharing control method based on self-adaptive droop |
| CN113725923B (en) * | 2021-10-08 | 2023-05-26 | 湖南工业大学 | Active power equipartition control method for photovoltaic micro-grid system based on self-adaptive sagging |
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Application publication date: 20210105 |