CN108988392B - Power distribution network self-adaptive low-voltage anti-island method based on back-to-back converter - Google Patents
Power distribution network self-adaptive low-voltage anti-island method based on back-to-back converter Download PDFInfo
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- CN108988392B CN108988392B CN201810939549.5A CN201810939549A CN108988392B CN 108988392 B CN108988392 B CN 108988392B CN 201810939549 A CN201810939549 A CN 201810939549A CN 108988392 B CN108988392 B CN 108988392B
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- 238000000034 method Methods 0.000 title claims abstract description 15
- 230000004224 protection Effects 0.000 claims abstract description 12
- 238000010248 power generation Methods 0.000 claims abstract description 10
- 230000001939 inductive effect Effects 0.000 claims description 2
- 230000035945 sensitivity Effects 0.000 abstract description 4
- 238000011160 research Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 230000001976 improved effect Effects 0.000 description 2
- 230000001960 triggered effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
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Classifications
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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
- H02J3/381—Dispersed generators
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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
-
- 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
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
The invention discloses a self-adaptive low-voltage anti-island method of a power distribution network based on a back-to-back converter. The control loop comprises a disturbance load impedance configuration module, a disturbance load impedance expected load calculation module, a back-to-back converter output voltage amplitude control module and a back-to-back converter output voltage phase control module. By using the anti-islanding method disclosed by the invention, after the anti-islanding reliability requirement, the anti-islanding sensitivity requirement and the distributed power generation capacity are changed, the equivalent impedance value of the disturbance load unit can be adaptively adjusted, so that the action requirement of the protection device is met, and the distributed power generation unit is effectively cut off after the anti-islanding is put into operation.
Description
Technical Field
The invention relates to a self-adaptive low-voltage anti-islanding method of a power distribution network based on a back-to-back converter, in particular to a risk identification method of influence of a distributed energy access power distribution network based on a brittleness theory on the voltage of the power distribution network, and belongs to the technical field of energy.
Background
With the increasing prominence of environmental problems caused by traditional fossil energy, new energy sources mainly comprising solar energy and wind energy are intensively studied and widely utilized. The distributed new energy grid-connected power generation can effectively solve the environmental problem, but a large amount of new energy is connected to cause the reduction of the power quality of a power grid, so that the voltage fluctuation, the power supply reliability reduction and other results are caused.
For the above reasons, it is necessary to study the effect of distributed energy on the voltage of the distribution network after it has been accessed. The students at home and abroad have also studied the aspects of voltage reliability, electric energy quality, power grid planning and the like of the distribution network accessed by the distributed energy sources. Although the effect of distributed energy access on the voltage of a power distribution network is very intensive, the following two aspects of the current research still need to be further studied:
1. The current research only combines the influence of the distributed energy access on the voltage of the power distribution network, provides a plurality of evaluation indexes for the power distribution network containing the distributed energy from the aspects of safety, reliability, stability, economy and the like, and does not formulate a quantitative index of actual risk;
2. The current research is aimed at voltage fluctuation generated by each independent node after the distributed energy is accessed, and chain reaction fluctuation of other nodes of the system, which is generated by voltage fluctuation of one node in the power distribution network, is not researched, so that actual running conditions can not be comprehensively reflected.
Disclosure of Invention
In order to solve the technical problems of the background technology, the invention aims to provide a risk identification method for the influence of a distributed energy access power distribution network on the voltage of the power distribution network based on a brittleness theory, and overcomes the defects that the current research lacks risk quantification indexes and does not consider the chain reaction of the power distribution network.
The invention adopts the following technical scheme for solving the technical problems:
The invention provides a self-adaptive low-voltage anti-islanding method of a power distribution network based on a back-to-back converter, which is used for carrying out low-voltage anti-islanding protection of the power distribution network through a disturbance load unit and a control loop, wherein the disturbance load unit consists of the back-to-back converter and an initial disturbance resistor; the control loop comprises a disturbance load impedance configuration module, a disturbance load impedance expected load calculation module, a back-to-back converter output voltage amplitude control module and a back-to-back converter output voltage phase control module, wherein the disturbance load impedance Z d-eq ' is required to be configured by the disturbance load unit is calculated by the disturbance load impedance configuration module, the active power value P ref and the reactive power value Q ref corresponding to Z d-eq ' are calculated by the disturbance load impedance expected load calculation module according to Z d-eq ', the modulation amplitude of the back-to-back converter output voltage is calculated by the back-to-back converter output voltage amplitude control module according to P ref and the real-time active power of the disturbance load unit, and the modulation phase of the back-to-back converter output voltage is calculated by the back-to-back converter output voltage phase control module according to Q ref and the real-time current of the disturbance load unit.
As a further technical solution of the present invention, the disturbance load impedance configuration module configures the disturbance load impedance Z d-eq' according to the following configuration formula:
Wherein, the disturbance load resistance value of the required configuration Disturbance load inductance value/>, of desired configurationDisturbance load capacitance value/>, of required configurationU n is the rated voltage of a bus, P inv is the distributed power generation capacity, U L is a set undervoltage threshold, U 0 and f 0 are the bus voltage and the output frequency of a photovoltaic system during island operation respectively, Q L is the local load inductive reactive power magnitude, f H is a set overfrequency threshold, Q C is the local load capacitive reactive power magnitude, and f L is a set underfrequency threshold.
As a further technical scheme of the invention, the disturbance load impedance expected load calculation module calculates an active power value P ref and a reactive power value Q ref corresponding to Z d-eq' according to the following formula:
wherein, Is the impedance angle of Z d-eq'.
As a further technical scheme of the invention, the control method of the back-to-back converter output voltage amplitude control module comprises the following steps: the difference value obtained by subtracting P ref from the real-time active power P input of the disturbance load unit is input into a PI controller, the output of the PI controller is multiplied by a PI post gain k to obtain an absolute value, and the result obtained after the absolute value is multiplied by half of the direct-current side voltage V DC of the back-to-back converter to obtain the modulation amplitude of the output voltage of the back-to-back converter.
As a further technical scheme of the invention, the control method of the back-to-back converter output voltage phase control module comprises the following steps: 1) The output of the PI controller is sent into a sign function sign, and the obtained result is multiplied by PI/2 and then subtracted by PI/2; 2) P ref and Q ref are sent to an impedance angle calculation unit to calculate the impedance angle of the disturbance load unit required configuration3) The real-time current I 0 of the disturbance load unit is sent into a phase-locked loop to obtain the real-time phase of I 0; and accumulating the results of 1), 2) and 3) to obtain the modulation phase of the output voltage of the back-to-back converter.
Compared with the prior art, the technical scheme provided by the invention has the following technical effects: according to the invention, the back-to-back converter is used for connecting an initial disturbance resistor in series to form a disturbance load unit, and the disturbance load unit participates in a low-voltage anti-island of the power distribution network. After the reliability requirement of the anti-island is improved, the equivalent impedance of the disturbance load unit can be changed from pure resistance to resistance or resistance-capacitance, so that under-voltage protection and over/under-frequency protection are triggered simultaneously after the anti-island is put into operation. After the sensitivity requirements (undervoltage threshold and over/under frequency threshold) or the distributed power generation capacity of the anti-islanding device are changed, the equivalent impedance value of the disturbance load unit can be adjusted in a self-adaptive mode, so that the action requirements of the protection device are met, and the distributed power generation unit is effectively cut off after the anti-islanding device is put into operation. Based on the knowledge, the method has positive effect on improving the self-adaptive capacity of the low-voltage anti-island of the power distribution network.
Drawings
Fig. 1 is a schematic diagram of the distribution network system of the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only for explaining the present invention and are not to be construed as limiting the present invention.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The technical scheme of the invention is further described in detail below with reference to the accompanying drawings:
As shown in fig. 1, in the self-adaptive low-voltage anti-island method of the power distribution network based on the back-to-back converter, the back-to-back converter and an initial disturbance resistor R d-ini are combined into a disturbance load unit (one end of R d-ini is connected with the output of the back-to-back converter, and the other end is grounded), so that the low-voltage anti-island protection of the power distribution network is performed. After the reliability requirement of the anti-island is improved, the equivalent impedance of the disturbance load unit can be changed from pure resistance to resistance or resistance-capacitance, so that under-voltage protection and over/under-frequency protection are triggered simultaneously after the anti-island is put into operation. After the sensitivity requirements (undervoltage threshold and over/under frequency threshold) or the distributed power generation capacity of the anti-islanding device are changed, the equivalent impedance value of the disturbance load unit can be adjusted in a self-adaptive mode, so that the action requirements of the protection device are met, and the distributed power generation unit is effectively cut off after the anti-islanding device is put into operation.
The control loop of the disturbance load unit comprises a disturbance load impedance configuration module, a disturbance load impedance expected load calculation module, a back-to-back converter output voltage amplitude control module and a back-to-back converter output voltage phase control module.
Specifically, the inputs to the disturbance load impedance configuration module include anti-islanding sensitivity requirements (i.e., undervoltage, over/under frequency thresholds), anti-islanding reliability requirements (i.e., single protection or multiple protections), distributed generation capacity; the output is a disturbance load impedance Z d-eq' of the desired configuration.
The specific configuration formula of the disturbance load impedance configuration module is as follows:
Wherein R d is the disturbance load resistance of the required configuration; u n is the rated voltage of the bus; p inv is the distributed power generation capacity; u L is a set under-voltage threshold; l d is a disturbance load inductance value of a required configuration; u 0 and f 0 are respectively the bus voltage and the output frequency of the photovoltaic system when the island operates; q L is the local load-sensitive reactive power; f H is a set overfrequency threshold; c d is the disturbance load capacitance resistance value of the required configuration; q C is the in-situ load capacitive reactive size; f L is a set undershoot threshold.
Specifically, the input of the disturbance load impedance expected load calculation module is a disturbance load impedance Z d-eq' of a required configuration; the output is the active power value P ref and the reactive power value Q ref corresponding to Z d-eq'.
The specific calculation formula of the disturbance load impedance expected load calculation module is as follows:
wherein, Is the impedance angle of Z d-eq'.
Specifically, the back-to-back converter output voltage amplitude control module inputs real-time active power P of P ref and the disturbance load unit; the output is the modulation amplitude of the back-to-back converter output voltage V 0. The back-to-back converter output voltage amplitude control module comprises a subtracter, a PI controller, a PI rear gain module, an absolute value taking module and a multiplier.
The specific flow of the back-to-back converter output voltage amplitude control module is as follows:
1) Subtracting P ref from P, and sending the difference to a PI controller;
2) The output of the PI controller is multiplied by a PI post gain k and then takes an absolute value;
3) And multiplying the result obtained after the absolute value is taken by half of the DC side voltage V DC of the back-to-back converter to obtain the modulation amplitude of the output voltage V 0 of the back-to-back converter.
Specifically, the input of the back-to-back converter output voltage phase control module is P ref、Qref, the output of a PI controller in the back-to-back converter output voltage amplitude control module and the real-time current I 0 of the disturbance load unit; the output is the modulation phase of the back-to-back converter output voltage V 0. The back-to-back converter output voltage phase control module comprises a sign function module, a multiplier, a subtracter, an adder, an impedance angle calculation module and a phase-locked loop.
The specific flow of the back-to-back converter output voltage phase control module is as follows:
1) The output quantity of a PI controller in the back-to-back converter output voltage amplitude control module is fed into a sign function sign, and the obtained result is multiplied by PI/2 and then subtracted by PI/2;
2) P ref and Q ref are sent to an impedance angle calculation unit to obtain an impedance angle of the configuration required by the disturbance load unit, and the specific formula is as follows:
3) I 0 is fed into a phase-locked loop to obtain the real-time phase of I 0.
4) Accumulating the results of 1) 2) 3) to obtain the modulation phase of the back-to-back converter output voltage V 0.
The foregoing is merely illustrative of the embodiments of the present invention, and the scope of the present invention is not limited thereto, and any person skilled in the art will appreciate that modifications and substitutions are within the scope of the present invention, and the scope of the present invention is defined by the appended claims.
Claims (1)
1. The self-adaptive low-voltage anti-islanding method for the power distribution network based on the back-to-back converter is characterized by comprising the steps of carrying out low-voltage anti-islanding protection on the power distribution network through a disturbance load unit and a control loop, wherein the disturbance load unit consists of the back-to-back converter and an initial disturbance resistor; the control loop comprises a disturbance load impedance configuration module, a disturbance load impedance expected load calculation module, a back-to-back converter output voltage amplitude control module and a back-to-back converter output voltage phase control module, wherein the disturbance load impedance Z d-eq ' is required to be configured for a disturbance load unit by the disturbance load impedance configuration module, the disturbance load impedance expected load calculation module calculates an active power value P ref and a reactive power value Q ref corresponding to Z d-eq ' according to Z d-eq ', the back-to-back converter output voltage amplitude control module calculates a modulation amplitude of the back-to-back converter output voltage according to P ref and the disturbance load unit real-time active power, and the back-to-back converter output voltage phase control module calculates a modulation phase of the back-to-back converter output voltage according to Q ref and the disturbance load unit real-time current;
The perturbation load impedance configuration module configures the perturbation load impedance Z d-eq' according to the following configuration formula:
Wherein, the disturbance load resistance value of the required configuration Disturbance load inductance value of required configurationDisturbance load capacitance value/>, of required configurationU n is the rated voltage of a bus, P inv is the distributed power generation capacity, U L is a set undervoltage threshold, U 0 and f 0 are the bus voltage and the output frequency of a photovoltaic system during island operation respectively, Q L is the local load inductive reactive power magnitude, f H is a set overfrequency threshold, Q C is the local load capacitive reactive power magnitude, and f L is a set underfrequency threshold;
The disturbance load impedance expected load calculation module calculates an active power value P ref and a reactive power value Q ref corresponding to Z d-eq' according to the following formula:
wherein, An impedance angle of Z d-eq';
The control method of the back-to-back converter output voltage amplitude control module comprises the following steps: the difference value obtained by subtracting P ref from the real-time active power Poutput of the disturbance load unit is input into a PI controller, the output of the PI controller is multiplied by a PI post gain k to obtain an absolute value, and the result obtained after the absolute value is multiplied by half of the direct-current side voltage V DC of the back-to-back converter to obtain the modulation amplitude of the output voltage of the back-to-back converter;
The control method of the back-to-back converter output voltage phase control module comprises the following steps: 1) The output of the PI controller is sent into a sign function sign, and the obtained result is multiplied by PI/2 and then subtracted by PI/2; 2) P ref and Q ref are sent to an impedance angle calculation unit to calculate the impedance angle of the disturbance load unit required configuration 3) The real-time current I 0 of the disturbance load unit is sent into a phase-locked loop to obtain the real-time phase of I 0; and accumulating the results of 1), 2) and 3) to obtain the modulation phase of the output voltage of the back-to-back converter.
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| CN110957741A (en) * | 2019-12-30 | 2020-04-03 | 南京师范大学 | Reactive response control system for demand side back-to-back converter |
| CN117805541B (en) * | 2024-02-29 | 2024-05-03 | 西安千帆翼数字能源技术有限公司 | Island detection method, protection method and related device of energy storage converter |
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| CN104682356A (en) * | 2015-02-10 | 2015-06-03 | 南京能迪电气技术有限公司 | Adaptive variable load anti-islanding method for distributed type photovoltaic power supply |
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| US8310105B2 (en) * | 2011-08-30 | 2012-11-13 | Renewable Power Conversion, Inc. | Centralized islanding protection for distributed renewable energy generators |
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| CN101741101A (en) * | 2010-01-22 | 2010-06-16 | 南京航空航天大学 | Method for realizing network access current of unity power factor of grid-connected inverter and internal anti-islanding |
| JP2013090396A (en) * | 2011-10-14 | 2013-05-13 | Meidensha Corp | Electric power conversion device |
| CN103138268A (en) * | 2013-02-25 | 2013-06-05 | 国家电网公司 | Low-voltage anti-island device of distributed photovoltaic power generation systems |
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