CN103683330B - A kind of micro-grid system off-network is to grid-connected changing method and system - Google Patents
A kind of micro-grid system off-network is to grid-connected changing method and system Download PDFInfo
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Abstract
The invention discloses a kind of micro-grid system off-network to grid-connected changing method and system, including: the magnitude of voltage of grid side, frequency values and the phase value that the first voltage acquisition module collection connects；The phase value of the microgrid side that the second voltage acquisition module collection connects；PCS regulates and controls the voltage of described microgrid side according to described grid side magnitude of voltage, regulates and controls the frequency of described microgrid side according to described grid side frequency values；PCS compares the absolute value of grid side and the phase contrast of microgrid side；If it is determined that to absolute value more than threshold value, then control the phase place of described microgrid side according to the first advanced or delayed respective angles of range of accommodation value；If it is determined that be not more than threshold value to absolute value, then control the phase place of described microgrid side according to the second advanced or delayed respective angles of range of accommodation value；Meeting the requirements until determining described absolute value, micro-grid system being switched to grid-connected。Compared with prior art, this switching mode can realize off-network and takes over seamlessly to grid-connected。
Description
Technical field
The present invention relates to electric power switching control field, particularly relate to a kind of micro-grid system off-network to grid-connected changing method and system。
Background technology
In intelligent network, micro-grid system is connected with electrical network by switching equipment。Switching equipment includes synchronous device and PCS device。
In running, after electrical network goes wrong, micro-grid system needs to be switched to microgrid by the supply of electric power of load equipment from electrical network in time, provides electric power by the power supply of microgrid for load equipment, and microgrid is now off-network state。When after the power recovery of electrical network, it is necessary to the electric power of micro-grid system converts to electrical network to be provided。This process is and network process。
Existing schematic network structure shown in Figure 1, current off-network includes to grid-connected handoff procedure:
Signal of telecommunication difference between the synchronous device detection grid side and the microgrid side that are connected with grid side, microgrid side, difference according to the signal of telecommunication, PCS constantly regulates the frequency of voltage of microgrid side, amplitude etc. according to the difference of the signal of telecommunication, until after consistent between both sides, the supply of electric power of microgrid side being transformed into grid side。
This handoff procedure, owing to the time regulated is longer, causes that switching time is long, electrical part is impacted。
Summary of the invention
In view of this, the invention reside in a kind of micro-grid system off-network of offer to grid-connected changing method and system, with the problem solving length switching time in above-mentioned handoff procedure。
For solving the problems referred to above, the present invention provides a kind of micro-grid system off-network to grid-connected changing method, including:
The magnitude of voltage of grid side, frequency values and the phase value that first voltage acquisition module collection connects；The phase value of the microgrid side that the second voltage acquisition module collection connects；
PCS regulates and controls the voltage of described microgrid side according to described grid side magnitude of voltage, regulates and controls the frequency of described microgrid side according to described grid side frequency values；
PCS compares the absolute value of grid side and the phase contrast of microgrid side；
If it is determined that to absolute value more than threshold value, then control the phase place of described microgrid side according to the first advanced or delayed respective angles of range of accommodation value；
If it is determined that be not more than threshold value to absolute value, then control the phase place of described microgrid side according to the second advanced or delayed respective angles of range of accommodation value；
Meeting the requirements until determining described absolute value, micro-grid system being switched to grid-connected。
Also include before described regulation and control:
Described second voltage acquisition module gathers magnitude of voltage and the frequency values of described microgrid side；
The more described grid side of described PCS and the difference of magnitude of voltage of described microgrid side, frequency values difference whether more than threshold value, if it is greater, then perform described regulation and control step；Otherwise micro-voltage on line side, frequency are not regulated and controled。
Described threshold value is 0.5235；Described first range of accommodation value is between 0.1～0.2, and described second range of accommodation value is between 0.01～0.02。
Determine described absolute value to meet the requirements, micro-grid system be switched to grid-connected process and include:
Judge that described absolute value is less than 0.087, then PCS sends control signal to PCC switch, and PCC switch closes described electrical network and described microgrid。
The number of times of each phase voltage dead electricity ratio of the grid side that described PCS gathers according to described first voltage acquisition module, triggers described PCC and switches off。
The present invention also provides for a kind of micro-grid system off-network to grid-connected switched system, including:
Voltage acquisition unit, for the magnitude of voltage of grid side connected by the first voltage acquisition module collection, frequency values and phase value, by the phase value of the microgrid side that the second voltage acquisition module collection connects；
Regulation and control unit, for being regulated and controled the voltage of described microgrid side by PCS according to described grid side magnitude of voltage, regulate and control the frequency of described microgrid side according to described grid side frequency values；
Comparing unit, for comparing the absolute value of grid side and the phase contrast of microgrid side by PCS；
First trigger element, for if it is determined that the absolute value obtained to described comparing unit is more than threshold value, then controlling the phase place of described microgrid side according to the first advanced or delayed respective angles of range of accommodation value；
Second trigger element, for if it is determined that the absolute value obtained to described comparing unit is not more than threshold value, then controlling the phase place of described microgrid side according to the second advanced or delayed respective angles of range of accommodation value；
Switch unit, determines described absolute value for described first trigger element and the second trigger element and meets the requirements, be switched to by micro-grid system grid-connected。
The method and system of the present invention, owing to according to the voltage of grid side and the voltage of frequency direct regulation and control microgrid side and frequency, by the phase place more progressively regulating microgrid side of phase place, the time with adjustment is short, and switching time is fast, impacts little to electrical part。
Accompanying drawing explanation
Fig. 1 is the schematic network structure of prior art；
Fig. 2 be prior art control algolithm block diagram；
Fig. 3 is schematic network structure in the present embodiment；
Fig. 4 is the structural representation of voltage acquisition module in the present embodiment；
Fig. 5 is the structural representation of intelligence PCS energy accumulation current converter in the present embodiment；
Fig. 6 is the flow chart of off-network process in the present embodiment；
Fig. 7 is grid-connected to off-grid control algolithm flow chart in the present embodiment；
Fig. 8 is that the present embodiment is grid-connected to off-grid control algolithm block diagram；
Fig. 9 is the grid-connected analogous diagram to off-network switching of the present embodiment；
Figure 10 is the present embodiment off-network to grid-connected handoff procedure；
Figure 11 is the present embodiment off-network to grid-connected control algolithm flow chart；
Detailed description of the invention
For knowing the scheme in the explanation present invention, preferred embodiment is given below and is described with reference to the accompanying drawings。
The structure of the micro-grid system in embodiments of the invention, referring to Fig. 3, including: intelligence PCS energy accumulation current converter, PCC switchs between civil power bulk power grid and micro-capacitance sensor, and voltage acquisition module V1 and voltage acquisition module V2 is connected between civil power bulk power grid, micro-capacitance sensor and intelligence PCS energy accumulation current converter。
Microgrid intelligence PCS energy accumulation current converter detects bulk power grid line voltage in real time by voltage acquisition module V1, calculates bulk power grid voltage magnitude Ugrid phase place in real timeWith frequency fgrid。Detect microgrid line voltage in real time by voltage acquisition module V2, calculate microgrid voltage magnitude Uminigrid, phase place in real timeWith frequency fminigrid。
Intelligence PCS energy accumulation current converter is according to the Data Control PCC switch gathered。
Wherein, voltage acquisition module adopts hardware configuration as shown in Figure 4 to realize, referring to Fig. 4, voltage acquisition module V1 is the same with voltage acquisition module V2 internal structure, voltage acquisition module V1 is made up of a resistance R1 and a voltage sensor 1, and voltage acquisition module V2 is made up of a resistance R2 and a voltage sensor 2。
Referring to Fig. 5, intelligence PCS energy accumulation current converter adopts structure as shown in Figure 5 to realize, including intelligence PCS energy accumulation current converter central processing unit and three phase rectifier/inverter circuit module, wherein intelligence PCS energy accumulation current converter central processing unit includes data acquisition module, network voltage detection controller, phase difference detection controller, PCC switch controller, battery management system。
The method of the present invention realizes the grid-connected and off-network process between microgrid and electrical network by the micro-grid system of above-mentioned Fig. 3,4,5。
Off-network process is described first below, referring to Fig. 6, including:
S61: the first voltage acquisition module gathers each phase voltage value of the grid side of its connection；Voltage acquisition module V1 in voltage acquisition module and Fig. 3；
S62:PCS determines the current voltage value dead electricity ratio relative to standard value of every phase voltage, adds up the described dead electricity ratio number of times summation lower than predetermined value of each phase voltage；
S63:PCS judges that the numerical value of described summation is more than threshold value, then perform VF switching, and the PCC simultaneously triggered between described electrical network and the microgrid of its connection switches off。
The method of embodiments of the invention, by calculating PWM output duty cycle directly to the mode determining modulating wave。Can grid-connected in off-network handoff procedure, it is ensured that intelligence PCS energy accumulation current converter quickly sets up microgrid reference voltage amplitude and frequency when VF controls, it is ensured that micro-grid system distributed power source normal operation。
Below by this process of concrete example in detail,
Flow chart shown in Figure 7, grid-connected to off-grid flow chart, comprise the following steps:
First voltage acquisition module gathers each phase voltage value of the grid side of its connection；
PCS determines the current voltage value dead electricity ratio relative to standard value of every phase voltage, adds up the described dead electricity ratio number of times summation lower than predetermined value of each phase voltage；
PCS judges that the numerical value of described summation is more than threshold value, then perform VF switching, and the PCC simultaneously triggered between described electrical network and the microgrid of its connection switches off。
Described dead electricity ratio is the difference of current voltage value and described standard value, and the ratio of this difference and described standard value is as described dead electricity ratio；
Preferably: described predetermined value is between 12%～18%, described number of times is between 4～8。
Preferably: described predetermined value is 15%, described number of times is 5。Specific operation process is:
The line voltage of the S11: the first voltage acquisition module V1 Real-time Collection bulk power grid, now count value N=0；
S12: calculate effective voltage value UA, UB, the UC of bulk power grid in real time；
S13: comparison procedure, sees that whether UA, UB, UC any one voltage magnitude is lower than 15%, if any one phase voltage amplitude of UA, UB, UC falls 15%, now count value N carries out N++ calculating。
S14: if N > 5, then intelligence PCS energy accumulation current converter carries out grid-connected to off-network switching control, starts VF and controls, and output PCC switchs separating brake control signal simultaneously, it is achieved grid-connected control to off-grid seamless switching。If N < 5, then intelligence PCS energy accumulation current converter does not carry out grid-connected to off-network switching, keeps being incorporated into the power networks。If the voltage magnitude of UA, UB, UC three-phase is all without falling 15%, then restart detection。
Grid-connected to off-network switching, predetermined value threshold value arranges the too low sensitivity that can improve system, but can reduce the stability of system；Predetermined value threshold value arranges too high meeting and mentions the stability of system, but can reduce the dynamic response of system。
In experimentation, when arranging threshold value and being less than 12%, micro-grid system is to detection
Electrical network three-phase voltage UA, UB or UC Parameters variation is very sensitive, at line voltage because the other reasonses such as load increase, capacitance apparatus startup cause that line voltage transience is recovered after declining, now can cause micro-grid system the frequently switching of off-network switch, the load electricity consumption caused occurs abnormal, the fault-toleranr technique of reduction system, reduces micro-grid system stability。
In lab process, when arrange threshold value higher than be 18% time, although micro-grid system
Stability increases, but can cause system parameter variations sensitive not, causes that system can not detect the change of line voltage in time, causes that each equipment inverter of micro-grid system breaks down, and micro-grid system breaks down exception。
Therefore, through experimental data and comprehensive analysis, predetermined value is set to 15%, it is possible to meet the micro-grid system sensitivity to Parameters variation, Parameters variation can be made dynamic response simultaneously, meanwhile, also can guarantee that micro-grid system can stability requirement。
Referring to Fig. 8, for grid-connected to off-grid control algolithm block diagram in the present embodiment, pass through above-described embodiment, grid-connected to off-network switching control by calculating PWM output duty cycle directly to the mode determining modulating wave, can grid-connected in off-network handoff procedure, ensure that intelligence PCS energy accumulation current converter quickly sets up microgrid reference voltage amplitude and frequency when VF controls, it is ensured that micro-grid system distributed power source normal operation。Referring to Fig. 9, the grid-connected analogous diagram to off-network switching of the present embodiment, pass through emulation experiment, it can be seen that in the switching of zero crossing, rush of current is only small, it is possible to realize grid-connected taking over seamlessly to off-grid。
Above embodiment describes in detail grid-connected to off-grid handoff procedure, by the examples below illustrate off-network to grid-connected handoff procedure, referring to Figure 10, micro-grid system off-network to grid-connected handoff procedure, including:
The magnitude of voltage of grid side, frequency values and the phase value that S101: the first voltage acquisition module collection connects；The phase value of the microgrid side that the second voltage acquisition module collection connects；
S102:PCS regulates and controls the voltage of described microgrid side according to described grid side magnitude of voltage, regulates and controls the frequency of described microgrid side according to described grid side frequency values；
S103:PCS compares the absolute value of grid side and the phase contrast of microgrid side；
S104: if it is determined that to absolute value more than threshold value, then control the phase place of described microgrid side according to the first advanced or delayed respective angles of range of accommodation value；
S105: if it is determined that be not more than threshold value to absolute value, then control the phase place of described microgrid side according to the second advanced or delayed respective angles of range of accommodation value；
S106: meeting the requirements until determining described absolute value, micro-grid system being switched to grid-connected。
After above-mentioned regulating step, it is achieved off-network takes over seamlessly to grid-connected。Below by concrete example in detail said process。Participate in Figure 11, including:
It is switched to and during net state in off-network state, it is necessary to assure microgrid ac bus and bulk power grid ac bus amplitude, phase and frequency are consistent。Patent of the present invention realizes quickly regulating microgrid grid phase, amplitude, frequency adjustment, it is achieved micro-grid system is from off-network state to the switching of also net state。
Described off-network also included before grid-connected switching: described second voltage acquisition module V2 gathers magnitude of voltage and the frequency values of described microgrid side；The more described grid side of described PCS and the difference of magnitude of voltage of described microgrid side, frequency values difference whether less than threshold value, if it is less, perform off-network to grid-connected operation。Particularly as follows: be in off-network running status at micro-grid system, microgrid intelligence PCS energy accumulation current converter is in V/F voltage source control model。Microgrid intelligence PCS energy accumulation current converter can pass through voltage acquisition module V2 and detect microgrid voltage magnitude Uminigrid, phase place in real timeWith frequency fminigrid；If bulk power grid is from dead electricity to restoring electricity, intelligence PCS energy accumulation current converter detects the amplitude Ugrid phase place of bulk power grid by voltage acquisition module V1With frequency fgrid。
Owing to amplitude error and the frequency error of intelligence PCS energy accumulation current converter control output microgrid grid voltage amplitude and frequency and bulk power grid are less, micro-grid system voltage and FREQUENCY CONTROL can be made directly, first by the microgrid intelligence PCS energy accumulation current converter V/F voltage reference value Uref=Ugrid controlled, micro-grid system voltage magnitude Uminigrid=Ugrid is controlled；Then by the microgrid intelligence PCS energy accumulation current converter V/F voltage reference value fref=fgrid controlled, micro-grid system electric voltage frequency fminigrid=fgrid is controlled；Owing to intelligence PCS energy accumulation current converter control output microgrid electric network voltage phase is bigger with the phase error of bulk power grid, it is necessary to the phase place of micro-grid system is adjusted。
Preferably, described threshold value is 0.5235, and described first range of accommodation value is, between 0.1～0.2；Described second tune value range is between 0.01～0.02。
Off-network also includes to grid-connected handoff procedure, it is judged that described absolute value meets the requirements, and micro-grid system is switched to grid-connected process and includes: judge that described absolute value is less than 0.087, then send control signal to PCC switch, and PCC switch closes described electrical network and described microgrid。Particularly as follows: first calculate micro-grid system and bulk power grid phase contrastIfMore than 0, then it represents that the delayed bulk power grid of micro-grid system, intelligence PCS energy accumulation current converter will reduceValue；IfLess than 0, then it represents that the advanced bulk power grid of micro-grid system, intelligence PCS energy accumulation current converter will increaseValue。Due toError amount is likely to relatively big, directly changesValue is likely to result in the impact of electric current。IfIt is 30 degree more than 0.5235(angle), corresponding micro-grid systemIfIt is 30 degree less than 0.5235(angle), corresponding micro-grid systemGeneral γ1Span (0.1～0.2), general γ2Span (0.01～0.02)], if nowIt is 5 degree less than 0.087(angle), then do not carry out phase adjusted, then intelligence PCS energy accumulation current converter output PCC switchs energization control signal, it is achieved micro-grid system is from off-network to cutting-in control。
In off-network to grid-connected switching, lower than in threshold range, step-size in search arranges the too high degree of accuracy that can reduce system, but can improve the response speed of system；Step-size in search arranges the too low response speed that can reduce system, but can improve the degree of accuracy of system。
In experimentation, when phase contrast is more than threshold value 0.5235(corresponding angle 30 degree) time, adopt step-size in search γ1Span (0.1～0.2) (corresponding angle 5.7 °～11.4 °)。When phase contrast is more than 30 degree, it is ensured that the rapid response speed of system。If γ1When value is less than 0.1, phase contrast reduces speed and reduces, and corresponding microgrid is followed the tracks of bulk power grid phase velocity and reduced, thus reducing the corresponding speed of micro-grid system；If γ1When value is more than 0.2, phase contrast reduces speed and improves, and corresponding microgrid is followed the tracks of bulk power grid phase velocity and improved, thus reducing the response speed of micro-grid system, but tracking accuracy reduces, it is easy to beyond threshold range, cause the concussion of system。When phase contrast is less than 30 degree, it is therefore an objective to ensure systematic tracking accuracy, if γ2When value is more than 0.02, phase contrast reduces speed and improves, and corresponding microgrid is followed the tracks of bulk power grid phase velocity and improved, thus improving the corresponding speed of micro-grid system but being reduction of tracking accuracy；If γ2When value is less than 0.01, phase contrast reduces speed and reduces, and corresponding microgrid is followed the tracks of bulk power grid phase velocity and reduced, but improves the precision that system is followed the tracks of, it is ensured that the stable operation of system。
Therefore, through experimental data and comprehensive analysis, predetermined value threshold value is set to 0.5235, when more than 0.5235, γ1Span (0.1～0.2), γ2Span (0.01～0.02), it is possible to meet the micro-grid system sensitivity to Parameters variation, can make dynamic response to Parameters variation simultaneously, meanwhile, also can guarantee that micro-grid system can stability requirement。
The number of times of each phase voltage mistake value ratio of the grid side that described PCS gathers according to described first voltage acquisition module, triggers described PCC and switches off。
The present invention also provides for a kind of micro-grid system off-network to grid-connected switched system, including:
Voltage acquisition unit, for the magnitude of voltage of grid side connected by the first voltage acquisition module collection, frequency values and phase value, by the phase value of the microgrid side that the second voltage acquisition module collection connects；
Regulation and control unit, for being regulated and controled the voltage of described microgrid side by PCS according to described grid side magnitude of voltage, regulate and control the frequency of described microgrid side according to described grid side frequency values；
Comparing unit, for comparing the absolute value of grid side and the phase contrast of microgrid side by PCS；
First trigger element, for if it is determined that the absolute value obtained to described comparing unit is more than threshold value, then controlling the phase place of described microgrid side according to the first advanced or delayed respective angles of range of accommodation value；
Second trigger element, for if it is determined that the absolute value obtained to described comparing unit is not more than threshold value, then controlling the phase place of described microgrid side according to the second advanced or delayed respective angles of range of accommodation value；
Switch unit, determines described absolute value for described first trigger element and the second trigger element and meets the requirements, be switched to by micro-grid system grid-connected。
For the method and system set forth in each embodiment of the present invention, all within the spirit and principles in the present invention, any amendment of making, equivalent replacement, improvement etc., should be included within protection scope of the present invention。
Claims (6)
1. a micro-grid system off-network is to grid-connected changing method, it is characterised in that including:
The magnitude of voltage of grid side, frequency values and the phase value that first voltage acquisition module collection connects；The phase value of the microgrid side that the second voltage acquisition module collection connects；
PCS regulates and controls the voltage of described microgrid side according to described grid side magnitude of voltage, regulates and controls the frequency of described microgrid side according to described grid side frequency values；
PCS compares the phase contrast of grid side and microgrid side, and obtains the absolute value of phase contrast；
If it is determined that to absolute value more than threshold value, then control the phase place of described microgrid side according to the first advanced or delayed respective angles of range of accommodation value；
If it is determined that be not more than threshold value to absolute value, then control the phase place of described microgrid side according to the second advanced or delayed respective angles of range of accommodation value；
Meeting the requirements until determining described absolute value, micro-grid system being switched to grid-connected。
2. method according to claim 1, it is characterised in that also include before described regulation and control:
Described second voltage acquisition module gathers magnitude of voltage and the frequency values of described microgrid side；
The more described grid side of described PCS and the difference of magnitude of voltage of described microgrid side, frequency values difference whether more than threshold value, if it is greater, then perform described regulation and control step；Otherwise micro-voltage on line side, frequency are not regulated and controled。
3. method according to claim 1, it is characterised in that described threshold value is 0.5235；Described first range of accommodation value is between 0.1～0.2, and described second range of accommodation value is between 0.01～0.02。
4. method according to claim 1, it is characterised in that determine described absolute value and meet the requirements, is switched to micro-grid system grid-connected process and includes:
Judge that described absolute value is less than 0.087, then PCS sends control signal to PCC switch, and PCC switch closes described electrical network and described microgrid。
5. method according to claim 4, it is characterised in that the number of times of each phase voltage dead electricity ratio of the grid side that described PCS gathers according to described first voltage acquisition module, triggers described PCC and switches off。
6. a micro-grid system off-network is to grid-connected switched system, it is characterised in that including:
Voltage acquisition unit, for the magnitude of voltage of grid side connected by the first voltage acquisition module collection, frequency values and phase value, by the phase value of the microgrid side that the second voltage acquisition module collection connects；
Regulation and control unit, for being regulated and controled the voltage of described microgrid side by PCS according to described grid side magnitude of voltage, regulate and control the frequency of described microgrid side according to described grid side frequency values；
Comparing unit, for being compared the phase contrast of grid side and microgrid side by PCS, and obtains the absolute value of phase contrast；
First trigger element, for if it is determined that the absolute value obtained to described comparing unit is more than threshold value, then controlling the phase place of described microgrid side according to the first advanced or delayed respective angles of range of accommodation value；
Second trigger element, for if it is determined that the absolute value obtained to described comparing unit is not more than threshold value, then controlling the phase place of described microgrid side according to the second advanced or delayed respective angles of range of accommodation value；
Switch unit, determines described absolute value for described first trigger element and the second trigger element and meets the requirements, be switched to by micro-grid system grid-connected。
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| CN105162169B (en) * | 2015-08-31 | 2018-02-16 | 许继集团有限公司 | A kind of micro-capacitance sensor simultaneous interconnecting method based on phase Step wise approximation |
| CN107039992B (en) * | 2017-03-23 | 2020-02-21 | 许继电气股份有限公司 | Starting control method and system of MMC (modular multilevel converter) converter based on droop control |
| CN110224439B (en) * | 2019-07-08 | 2021-08-17 | 国网湖南省电力有限公司 | Grid-connected-island mode switching method for energy storage grid-connected inverter |
| CN110794195B (en) * | 2019-11-18 | 2022-05-24 | 北京煜邦电力技术股份有限公司 | Three-phase synchronous sampling method and device and storage medium |
| CN111443260A (en) * | 2020-04-24 | 2020-07-24 | 国网山西省电力公司吕梁供电公司 | Power grid phase difference detection method and system |
| CN115776130B (en) * | 2022-12-29 | 2024-02-02 | 北京索英电气技术股份有限公司 | Off-grid switching method, energy storage converter, energy storage system and power system |
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| US8427219B1 (en) * | 2011-12-05 | 2013-04-23 | Skymedi Corporation | Clock generator and a method of generating a clock signal |
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| US8427219B1 (en) * | 2011-12-05 | 2013-04-23 | Skymedi Corporation | Clock generator and a method of generating a clock signal |
| CN102403735A (en) * | 2011-12-19 | 2012-04-04 | 天津市电力公司 | Method and system for switching microgrid between island mode and grid connected mode |
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