CN102496956B - Mode switching method for switching grid-connected mode to island mode of microgrid - Google Patents
Mode switching method for switching grid-connected mode to island mode of microgrid Download PDFInfo
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- CN102496956B CN102496956B CN201110382239.6A CN201110382239A CN102496956B CN 102496956 B CN102496956 B CN 102496956B CN 201110382239 A CN201110382239 A CN 201110382239A CN 102496956 B CN102496956 B CN 102496956B
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Abstract
The invention provides a mode switching method for switching a grid-connected mode to an island mode for a microgrid. The method comprises the following steps: disconnecting the grid-connected switch; disconnecting all load switches for connecting loads in the microgrid into buses of the microgrid; selecting an energy storage power supply with the most abundant electric quantity as a main distributed power supply; starting a main distributed power supply and enabling the main distributed power supply to operate in a constant-voltage constant-frequency mode; when the bus voltage of the microgrid is greater than or equal to a preset voltage, closing a load switch of the microgrid to throw in a load in the microgrid; and putting the photovoltaic distributed power supply and the fan distributed power supply into operation and enabling the photovoltaic distributed power supply and the fan distributed power supply to work in a control mode that the active power and the reactive power output by the power supplies are equal to the reference power. According to the technical scheme, the switching from the grid-connected mode to the island mode can be performed, the power supply inside the microgrid is guaranteed, the influence on the microgrid can be reduced, and the service life of equipment inside the microgrid is guaranteed.
Description
Technical field
The pattern that the present invention relates to microgrid is switched, and specifically, relates to and microgrid is switched to the mode switching method of island mode from grid-connected pattern.
Background technology
Along with petering out of conventional energy resource, and day by day serious environmental pollution, within the scope of regenerative resource and distributed generation technology world in recent years, obtained increasing attention and development.At present, distributed power generation generally refer to generated output at the thousands of watts of miniaturizations to 50 megawatts, modularization, distributing, to be arranged near user be the small power generation system that is connected to distribution system of customer power supply.Current existing research and practice shows, by distributed power generation energy supplying system with micro power network (MicroGrid, be referred to as microgrid below) form access large electrical network and be incorporated into the power networks, support each other with large electrical network, be the effective means of performance distributed power generation energy supplying system usefulness.
As one of important composition form of distributed power generation; microgrid normally collects by distributed power source (DG), energy storage device, energy converter, relevant load, supervisory control system, protection system, power transmitting device etc. the small-sized electric system of being transported to forming, and is one and can realizes the autonomous system that oneself controls, protects and manage.Because, microgrid both can be by power distribution network and the parallel running of large-scale power net, form the combined operation system of a large-scale power grid and small grids, also can be independently for locality load provides electricity needs, its flexibly operational mode greatly improved the power supply reliability of load side; Meanwhile, microgrid accesses large electrical network by single-point, can reduce a large amount of small-power distributed power sources and access the impact on large electrical network after large electrical network.In addition, microgrid by disperse, the power supply that combines of dissimilar small power generation source (distributed power source), can make the higher utilization ratio of Miniature Power Unit acquisition.Under large electrical network normal condition, microgrid needs operation steady in a long-term; And when large electrical network is interfered, microgrid must depart from large electrical network fast, enter and be held in islet operation state, auto-parallel operation again after large electric network fault is got rid of.Above-mentioned functions is summarized as: peak load shifting, power are level and smooth, pattern switching etc.Realizing the required control strategy of these functions, is the difficult point of microgrid, and various countries research team is just continually developing more excellent control method and hardware forms.
In recent years, the development of wind power generation, solar photovoltaic technology, makes renewable energy power generation obtain increasing utilization, the technology that renewable energy power generation is combined with microgrid form, be the boundless technology of application prospect, become the frontier of electric power system research.Because microgrid is a kind of novel power grid, its system complex degree is much higher than General Electric Network, and this has caused the control strategy of microgrid General Electric Network relative to the complexity of control method also greatly to promote.
It is one of function best embodying microgrid value that pattern is switched, and can be summarized as three kinds of behaviors under different operating modes: (1), when large electrical network normal power supply, microgrid is with grid-connected mode operation; (2) when large electrical network occurs that interference causes powering, microgrid need to be switched to island mode from grid-connected pattern; (3) after large electric network fault is got rid of, service restoration, microgrid need to be switched to grid-connected pattern from island mode.
Pattern handoff technique has experienced operation manually to the evolution of machine automatic operation, focuses on the opportunity that How to choose pattern is switched, and the engagement process of each equipment while switching.
At present, existing micro-grid system is simply comprised of the distributed power source of single kind, load, power transmitting device etc. conventionally.Distributed power source is the power supply type of traditional energy normally, for example, take the energy type energy storage device that lead-acid batteries, lithium battery group be representative, also the combustion machine of configurable certain capacity.
Fig. 1 shows microgrid topological structure of the prior art.In the micro-grid system shown in Fig. 1, microgrid distributed power source is often combustion machine/energy-storage system, access bus BUS1, and microgrid load also accesses this bus BUS1.BUS1 is low-voltage alternating-current bus, and voltage, between 220V～35KV, is connected with BUS2 by transformer.BUS2 is high voltage AC bus, can be considered large electrical network, and voltage is between 10KV～220KV.Circuit breaker shown in PCC is the tie point between microgrid and large electrical network.
When large electrical network normal power supply, microgrid distributed power source stops generating, and PCC is in closure state, and microgrid is loaded completely by large mains supply; When large electric network fault, PCC is in off-state, and microgrid distributed power source starts generating, is the power supply of microgrid load.This technology is switched this control object mainly for realizing the pattern of microgrid.Conventionally control logic is implemented in the controller of current transformer of microgrid distributed power source.
But there is shortcoming as described below in the pattern switching that existing microgrid switches to island mode from grid-connected pattern: (1) can only adapt to the micro-grid system simple structure, and impulse current during control is high; (2), while being the distributed power generation type such as wind power generation, photovoltaic generation in micro-grid system, prior art cannot adapt to the coordination of regenerative resource and energy storage and control; (3) poor with the conformability of large electrical network, there is the possibility that affects large electric network protection, automation equipment.
Summary of the invention
When break down in microgrid outside, according to technical scheme of the present invention, can carry out the grid-connected island mode that turns and switch, ensure the power supply of microgrid inside, and in operating process, the impact reducing microgrid as much as possible, ensures the microgrid internal unit life-span.
According to an exemplary embodiment of the present, provide a kind of for microgrid when there is external fault, from grid-connected pattern, be switched to the mode switching method of island mode, described method comprises: disconnect grid-connected switch; Disconnect for the load in microgrid being accessed to all on-load switches of the bus of microgrid; Selecting the most abundant accumulation power supply of electric weight is main distributed power source; Start main distributed power source and this main distributed power source is moved in the mode of constant voltage constant frequency rate; When the busbar voltage of microgrid is more than or equal to predetermined voltage, the on-load switch of closed microgrid is to drop into the load in microgrid; Drop into photovoltaic distributed power source and make described photovoltaic distributed power source be operated in the active power of power supply output and the control model that reactive power equals reference power; Drop into blower fan distributed power source and make described blower fan distributed power source be operated in the active power of power supply output and the control model that reactive power equals reference power.
According to a further aspect in the invention, described method also can comprise: when external fault occurs, isolate all distributed power sources that moving in microgrid according to the electric connecting mode of the bus of the distributed power source in microgrid and microgrid simultaneously.
According to a further aspect in the invention, when distributed power source accesses the bus of microgrid with AC system access way, can select the circuit breaker disconnecting to isolate this distributed power source; When distributed power source accesses the bus of microgrid with direct current system access way, the power electronic device in strobe pulse blocking-up current transformer is to isolate this distributed power source.
According to a further aspect in the invention, described distributed power source is can carry out the element of energy output in microgrid, can comprise blower fan distributed power source, photovoltaic distributed power source and various accumulation power supply.
According to a further aspect in the invention, after having isolated all distributed power sources that moving in microgrid, by the result feedback of isolation to master control system, and the mode of secession switching when occurring isolating unsuccessfully.
According to a further aspect in the invention, after having isolated all distributed power sources that moving in microgrid, while confirming that backup auto-activating device moves successfully, can from grid-connected pattern, be switched to the pattern switching termination of island mode, distributed power source is accessed to large electrical network successively.
According to a further aspect in the invention, after confirming backup auto-activating device baulk, can continue to carry out the pattern switching that grid-connected pattern is switched to island mode.
According to a further aspect in the invention, if grid-connected switch does not successfully disconnect while disconnecting grid-connected switch, described in while disconnecting described on-load switch, on-load switch does not successfully disconnect, or the busbar voltage of microgrid is less than described predetermined voltage, can stops the pattern that grid-connected pattern is switched to island mode and switch.
According to a further aspect in the invention, the pattern handoff procedure from grid-connected pattern to island mode, carve and be designed with delay strategy to guarantee impulse current minimum and the impact of the circulation between the element minimum of transient state.
Accompanying drawing explanation
Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail.
Fig. 1 shows microgrid topological structure of the prior art.
Fig. 2 shows the control flow chart that is switched to according to an exemplary embodiment of the present invention island mode from grid-connected pattern.
Embodiment
Fig. 2 shows the control flow chart that is switched to according to an exemplary embodiment of the present invention island mode from grid-connected pattern.According to an exemplary embodiment of the present, utilize the electric disturbance situation of supply line, low-voltage bus bar, the external fault of microgrid is detected in real time, when external fault occurs, prepare to carry out pattern switching.Now, isolate at once all distributed power sources moving in microgrid simultaneously, wait for relaying protection system, automated security control system, spare power automatic switching system action that large electrical network configures.Here, the distributed power source (DG) that needs according to an exemplary embodiment of the present invention isolation is the element that can carry out energy output in microgrid, be not limited in the distributed power source of single kind, but comprise the combination of wind power generation power supply, photovoltaic generation power supply and various accumulation power supplies.The method of isolation is depending on the electric connecting mode of the bus of distributed power source and microgrid: when distributed power source accesses the bus of microgrid with AC system access way, can select the circuit breaker disconnecting; When distributed power source accesses the bus of microgrid with direct current system access way, can block the power electronic device in current transformer by strobe pulse.The result of isolation will feed back to master control system, when occurring isolating unsuccessfully, must switch by the mode of secession.
After confirming that backup auto-activating device moves successfully, pattern is switched termination, and distributed power source accesses large electrical network successively.After confirming backup auto-activating device baulk, continue to carry out the pattern switching that grid-connected pattern is switched to island mode.Below, with reference to Fig. 2, describe the pattern handover operation that is switched to island mode from grid-connected pattern in detail.
At step S210, disconnect grid-connected switch.
At step S220, judge whether grid-connected switch disconnects.If disconnected grid-connected switch, carry out step S230; Otherwise, carry out step S310, the equipment that termination pattern switches and safety isolation has moved.
At step S230, disconnect for the load in microgrid being accessed to all on-load switches of microgrid bus.
At step S240, judge whether to have disconnected all on-load switches.If disconnected all on-load switches, carry out step S250; Otherwise, carry out step S310.
At step S250, selecting the most abundant accumulation power supply of electric weight is main distributed power source, and judges whether this main distributed power source can work.If can work, carry out step S260; Otherwise, carry out step S310.Wherein, according to the state-of-charge of main distributed power source, whether be greater than predetermined threshold and determine whether main distributed power source can work.For example (but being not limited to), described predetermined threshold can be 80%.If the state-of-charge of main distributed power source is more than or equal to predetermined threshold, this main distributed power source can work to set up voltage and the frequency of microgrid; If the state-of-charge of main distributed power source is less than predetermined threshold, definite this main distributed power source cannot be worked.
At step S260, start main distributed power source and control its mode with constant voltage constant frequency rate and move.
At step S270, judge whether the busbar voltage of microgrid is greater than predetermined voltage U1 to judge whether microgrid busbar voltage is recovered.When judging the recovery of microgrid busbar voltage, carry out step S280; Otherwise, carry out step S310.
At step S280, the on-load switch of closed microgrid, to drop into the load in microgrid.
At step S290, drop into photovoltaic distributed power source and make it be operated in the PQ control model that equals respectively its reference power from active power and the reactive power of the output of photovoltaic distributed power source.
At step S300, drop into blower fan distributed power source and make it be operated in the PQ control model that equals respectively its reference power from active power and the reactive power of the output of blower fan distributed power source.
In addition, it should be noted that the whole pattern handoff procedure from grid-connected pattern to island mode, be designed with suitable delay strategy minimum to guarantee impulse current minimum and the impact of the circulation between element of transient state.
According to another exemplary embodiment of the present invention, when large electric network fault being detected, stop at once inner all equipment that comprise distributed power source and various loads that moving of microgrid, disconnect grid-connected switch, large electrical network to be confirmed cannot continue, after power supply, from step S250, to start operation.
In addition, when judging large electrical network and can also continue to power, need stage by stage closed grid-connected switch, drop into microgrid load and drop into distributed power source.
According to an exemplary embodiment of the present, because the pattern that is designed with is switched Initiated Mechanism, itself and backup auto-activating device coordinate, and improve backup auto-activating device motional success rate, improve to a greater extent microgrid power supply reliability.At microgrid equipment room, coordinate to control, and in addition suitable order and time delay, thereby reduced impulse current each other, and circulation impact.In addition, the most applicable energy type energy-storage travelling wave tube of bearing main power source of intelligent selection, for setting up more stable microgrid voltage and frequency.In addition, according to exemplary embodiment of the present invention, be provided with pattern handover security termination mechanism, when there is fortuitous event, can protect equipment.
Claims (9)
- For microgrid when there is external fault, from grid-connected pattern, be switched to a mode switching method for island mode, described method comprises:Disconnect grid-connected switch;Disconnect for the load in microgrid being accessed to all on-load switches of the bus of microgrid;Selecting the most abundant accumulation power supply of electric weight is main distributed power source;Start main distributed power source and this main distributed power source is moved in the mode of constant voltage constant frequency rate;When the busbar voltage of microgrid is more than or equal to predetermined voltage, the on-load switch of closed microgrid is to drop into the load in microgrid;Drop into photovoltaic distributed power source and make described photovoltaic distributed power source be operated in the active power of power supply output and the control model that reactive power equals reference power;Drop into blower fan distributed power source and make described blower fan distributed power source be operated in the active power of power supply output and the control model that reactive power equals reference power.
- 2. the method for claim 1, also comprises:When external fault occurs, according to the electric connecting mode of the bus of the distributed power source in microgrid and microgrid, isolate all distributed power sources that moving in microgrid simultaneously.
- 3. method as claimed in claim 2, wherein, when distributed power source accesses the bus of microgrid with AC system access way, selects the circuit breaker disconnecting to isolate this distributed power source; When distributed power source accesses the bus of microgrid with direct current system access way, the power electronic device in strobe pulse blocking-up current transformer is to isolate this distributed power source.
- 4. method as claimed in claim 3, wherein, described distributed power source is can carry out the element of energy output in microgrid, comprises blower fan distributed power source, photovoltaic distributed power source and various accumulation power supply.
- 5. method as claimed in claim 4, wherein, after having isolated all distributed power sources that moving in microgrid, by the result feedback of isolation to master control system, and the mode of secession switching when occurring isolating unsuccessfully.
- 6. method as claimed in claim 5, wherein, after having isolated all distributed power sources that moving in microgrid, while confirming that backup auto-activating device moves successfully, the pattern that is switched to island mode from grid-connected pattern is switched termination, and distributed power source is accessed to large electrical network successively.
- 7. method as claimed in claim 5, wherein, after confirming backup auto-activating device baulk, continues to carry out the pattern switching that grid-connected pattern is switched to island mode.
- 8. the method for claim 1, wherein, if grid-connected switch does not successfully disconnect while disconnecting grid-connected switch, described in while disconnecting described on-load switch, on-load switch does not successfully disconnect, or the busbar voltage of microgrid is less than described predetermined voltage, stops the pattern that grid-connected pattern is switched to island mode and switch.
- 9. the method for claim 1, wherein the pattern handoff procedure from grid-connected pattern to island mode, be designed with delay strategy minimum to guarantee impulse current minimum and the impact of the circulation between element of transient state.
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| CN103595052B (en) * | 2013-10-25 | 2015-07-01 | 国家电网公司 | Method for stably controlling switchover from micro-grid connection into island state |
| CN103840487B (en) * | 2014-04-01 | 2016-01-20 | 阳光电源股份有限公司 | Black-start method, EMS and common ac bus are from net type light storage microgrid |
| CN110021963B (en) * | 2019-05-29 | 2023-06-23 | 唐山冀东石油机械有限责任公司 | Method for smooth switching control of micro-grid combined in off-grid dual mode |
| CN110212577A (en) * | 2019-06-17 | 2019-09-06 | 南通国轩新能源科技有限公司 | A kind of energy resource system self-balancing control method |
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| CN201654170U (en) * | 2010-04-29 | 2010-11-24 | 浙江省电力试验研究院 | Comprehensive micro net experimental system |
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Effective date of registration: 20160121 Address after: 100176 Beijing economic and Technological Development Zone, Beijing, Kangding street, No. 19, No. Patentee after: Beijing Goldwind Science & Creation Windpower Equipment Co., Ltd Patentee after: State Grid Xinyuan Zhangjiakou Scenery Storage Demonstration Power Plant Co., Ltd. Address before: 100176 Beijing economic and Technological Development Zone, Beijing, Kangding street, No. 19, No. Patentee before: Beijing Goldwind Science & Creation Windpower Equipment Co., Ltd |