CN108023366B - Method for preventing overvoltage of neutral point of main transformer for high-permeability photovoltaic - Google Patents
Method for preventing overvoltage of neutral point of main transformer for high-permeability photovoltaic Download PDFInfo
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- CN108023366B CN108023366B CN201810071835.4A CN201810071835A CN108023366B CN 108023366 B CN108023366 B CN 108023366B CN 201810071835 A CN201810071835 A CN 201810071835A CN 108023366 B CN108023366 B CN 108023366B
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- 230000007935 neutral effect Effects 0.000 title claims abstract description 35
- 238000000034 method Methods 0.000 title claims abstract description 19
- 239000003990 capacitor Substances 0.000 claims abstract description 29
- 238000004146 energy storage Methods 0.000 claims abstract description 25
- 230000035699 permeability Effects 0.000 claims abstract description 12
- 238000012544 monitoring process Methods 0.000 claims abstract description 4
- 210000004027 cell Anatomy 0.000 claims description 15
- 210000000352 storage cell Anatomy 0.000 claims description 6
- 238000013459 approach Methods 0.000 claims description 4
- 238000007667 floating Methods 0.000 claims description 3
- 238000010586 diagram Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 238000010248 power generation Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
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- H02J3/383—
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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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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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
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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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
- Y02E70/00—Other energy conversion or management systems reducing GHG emissions
- Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin
Abstract
The invention discloses a method for preventing overvoltage of a main transformer neutral point of a high-permeability photovoltaic, which comprises the following steps: s1: the photovoltaic cell access point is connected with a 10kV bus to obtain the operation of a regional main transformerLine mode, total load P in areaLoadΣAnd a current photovoltaic permeability γ; transformer neutral point voltage sensor real-time monitoring main transformer neutral point voltage Ufh(0)And the neutral point voltage U of the main transformer is converted intofh(0)Transmitting the data to a control system, and acquiring the state of charge (SOC) of the energy storage battery and the super capacitor module in the system; s2: judge Ufh(0)Whether or not 0 holds: if U is presentfh(0)If 0 is true, the SOC is determined again<0.5, if yes, switching the system to a state 1, otherwise, switching the system to a state 0; if U is presentfh(0)If 0 is not true, the process proceeds to step S3; s3: judge Ufh(0)Whether a step from 0 occurs: if a step occurs, the system is switched to state 2, and then immediately proceeds to step S4; s4: judge Ufh(0)Whether < 1.15pu holds: if so, switching the system to state 3; otherwise, the system is switched to state 4. The problem of neutral point overvoltage is solved.
Description
Technical Field
The invention relates to a power electronic control technology, in particular to a method for preventing overvoltage of a main transformer neutral point of high-permeability photovoltaic.
Background
In recent years, with the massive access of distributed photovoltaic power sources on the medium/low voltage side of a power distribution network, the permeability of the photovoltaic power sources is increased day by day, and the traditional unidirectional radiation-shaped power distribution network structure is gradually changed into a power distribution network structure with tidal current flowing in two directions. The influence of high-permeability photovoltaic on the operation mode of a traditional power distribution network is increasing day by day, for example, overvoltage of a neutral point of a main transformer which is not in grounded operation is caused, and even the phenomenon of insulation breakdown of the neutral point occurs. For ungrounded systems, when a single-phase ground fault occurs in the transmission line, the transformer neutral point will rise to the phase voltage. Most main transformers are now based on this phase voltage as an insulation level and protected against main transformer neutral overvoltages by adding lightning arresters or rod-rod clearance fit protection. However, such a method does not solve the real situation that the medium/low voltage side contains a large amount of photovoltaic to cause main transformer overvoltage from the root. With the development of photovoltaic power generation technology and the popularization of related poverty alleviation policies, if the overvoltage phenomenon of a main transformer neutral point is not solved fundamentally, the photovoltaic permeability is limited to be further improved, and the influence which cannot be estimated is also brought to the whole power distribution network.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a method for preventing overvoltage of a neutral point of a main transformer for high-permeability photovoltaic, which solves the problem of overvoltage of the neutral point of the main transformer from the control perspective of a photovoltaic power supply.
The technical scheme is as follows: the invention discloses a method for preventing overvoltage of a main transformer neutral point of a high-permeability photovoltaic, which comprises the following steps of:
s1: the photovoltaic cell access point is connected with a 10kV bus to obtain the operation mode of a main transformer in the region and the total load P in the regionLoadΣAnd a current photovoltaic permeability γ; transformer neutral point voltage sensor real-time monitoring main transformer neutral point voltage Ufh(0)And the neutral point voltage U of the main transformer is converted intofh(0)Transmitting the data to a control system, and acquiring the state of charge (SOC) of the energy storage battery and the super capacitor module in the system; according to Ufh(0)The system is divided into 5 operation states of state 0, state 1, state 2, state 3 and state 4, which are respectively:
state 0: in the state, the SOC of the energy storage battery and the SOC of the super capacitor module is greater than 0.5, and the neutral point of the main transformer has no overvoltage or the overvoltage is recovered to be normal;
state 1: in the state, the SOC of the energy storage battery and the SOC of the super capacitor module are less than 0.5, and the neutral point of the main transformer has no overvoltage or the overvoltage is recovered to be normal; if the overvoltage is recovered to be normal, a second direct current converter between the energy storage battery and the direct current bus is locked, a third direct current converter between the super capacitor module and the direct current bus is locked, the photovoltaic battery passes through the first direct current converter, and all power generated by the photovoltaic battery is input into a power grid through the photovoltaic inverter;
state 2: in the state, the photovoltaic cell keeps maximum power tracking control, the second direct current converter connected with the energy storage cell is locked temporarily, the super capacitor module is converged into a direct current bus through the third direct current converter, and the third direct current converter is controlled to enable the super capacitor module to enter charging control;
state 3: the photovoltaic cell gradually reduces the photovoltaic permeability through the first direct current converter, the direct current bus and the grid-connected inverter, and the photovoltaic cell respectively carries out stage charging on the energy storage cell and the super capacitor module through the first direct current converter, the direct current bus, the second direct current converter and the third direct current converter with the residual power; the photovoltaic permeability is the ratio of the output power of the photovoltaic cell to the sum of the load power;
and 4: locking the photovoltaic inverter, simultaneously enabling part of the power generated by the photovoltaic battery to pass through the first direct current converter, the direct current bus, the second direct current converter and the third direct current converter, respectively carrying out stage charging on the energy storage battery and the super capacitor module until the SOC approaches to 1, and directly entering a floating charging working mode if the SOC of the energy storage battery and the super capacitor module approaches to 1;
s2: judge Ufh(0)Whether or not 0 holds: if U is presentfh(0)If 0 is true, the SOC is determined again<0.5, if yes, switching the system to a state 1, otherwise, switching the system to a state 0; if U is presentfh(0)If 0 is not true, the process proceeds to step S3;
s3: judge Ufh(0)Whether a step from 0 occurs: if a step occurs, the system is switched to state 2, and then immediately proceeds to step S4;
s4: judge Ufh(0)Whether < 1.15pu holds: if so, switching the system to state 3; otherwise, the system is switched to state 4.
Has the advantages that: the invention discloses a method for preventing overvoltage of a main transformer neutral point for high-permeability photovoltaic, which has the following beneficial effects compared with the prior art:
1) along with different overvoltage degrees, the control effect is smoother;
2) transient overvoltage caused by operation and ground fault is effectively reduced by utilizing the rapid charge-discharge characteristic of the super capacitor;
3) the overvoltage problem of the neutral point of the main transformer can be quickly reflected, and the surplus photovoltaic power supply power can be stored, so that great social and economic benefits are achieved when the photovoltaic power supply runs for a long time;
4) the influence of high-permeability photovoltaic on the main transformer of the power distribution network is considered, and a control scheme is provided for further improving the permeability of distributed photovoltaic power generation.
Drawings
FIG. 1 is a schematic diagram of a circuit involved in a method according to an embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating the principle of the method according to the embodiment of the present invention.
Detailed Description
The specific embodiment discloses a method for preventing overvoltage of a main transformer neutral point of a high-permeability photovoltaic, which comprises the following steps:
s1: the photovoltaic cell access point is connected with a 10kV bus to obtain the operation mode of a main transformer in the region and the total load P in the regionLoadΣAnd a current photovoltaic permeability γ; transformer neutral point voltage sensor real-time monitoring main transformer neutral point voltage Ufh(0)And the neutral point voltage U of the main transformer is converted intofh(0)And transmitting the data to a control system, and acquiring the state of charge SOC of the energy storage battery and the super capacitor module in the system, wherein the SOC is generally between 0 and 1. According to Ufh(0)The system is divided into 5 operation states of state 0, state 1, state 2, state 3 and state 4, which are respectively:
state 0: under the state, the SOC of the energy storage battery and the SOC of the super capacitor module are greater than 0.5, and the neutral point of the main transformer is not over-voltage or the over-voltage is recovered to be normal.
State 1: in the state, the SOC of the energy storage battery and the SOC of the super capacitor module are less than 0.5, and the neutral point of the main transformer has no overvoltage or the overvoltage is recovered to be normal; and if the overvoltage is recovered to be normal, locking a second direct current converter between the energy storage battery and the direct current bus, locking a third direct current converter between the super capacitor module and the direct current bus, and inputting all power generated by the photovoltaic battery into a power grid through the photovoltaic inverter by the photovoltaic battery through the first direct current converter.
State 2: in the state, the photovoltaic cell keeps maximum power tracking control, the second direct current converter connected with the energy storage cell is locked temporarily, the super capacitor module is converged into a direct current bus through the third direct current converter, and the third direct current converter is controlled to enable the super capacitor module to enter charging control.
State 3: photovoltaic electricityThe pool is connected with a first DC converter, a DC bus and a grid-connected inverter according to the gamma of-1.33Ufh(0)+2.53 the photovoltaic permeability is reduced step by step until the photovoltaic cell is at 100% load power, i.e. PLoadΣOutputting constant power of a power grid, and allowing the photovoltaic cell to pass through a first direct current converter, a direct current bus, a second direct current converter and a third direct current converter to respectively charge the energy storage cell and the super capacitor module in a staged manner; and the photovoltaic permeability is the ratio of the output power of the photovoltaic cell to the sum of the load power.
And 4: and locking the photovoltaic inverter, simultaneously, enabling part of the power generated by the photovoltaic battery to pass through the first direct current converter, the direct current bus, the second direct current converter and the third direct current converter, respectively carrying out stage charging on the energy storage battery and the super capacitor module until the SOC is close to 1, and directly entering a floating charging working mode if the SOC of the energy storage battery and the super capacitor module is close to 1.
S2: judge Ufh(0)Whether or not 0 holds: if U is presentfh(0)If 0 is true, the SOC is determined again<0.5, if yes, switching the system to a state 1, otherwise, switching the system to a state 0; if U is presentfh(0)If 0 is not true, the process proceeds to step S3.
S3: judge Ufh(0)Whether a step from 0 occurs: if a step occurs, the system is switched to state 2 and then immediately proceeds to step S4.
S4: judge Ufh(0)Whether < 1.15pu holds: if so, switching the system to state 3; otherwise, the system is switched to state 4.
Fig. 1 is a schematic diagram of a circuit involved in the method, and fig. 2 is a schematic diagram of the principle of the method.
Claims (1)
1. A method for preventing overvoltage of a main transformer neutral point of high-permeability photovoltaic is characterized by comprising the following steps: the method comprises the following steps:
s1: the photovoltaic cell access point is connected with a 10kV bus to obtain the operation mode of a main transformer in the region and the total load P in the regionLoadΣAnd current photovoltaic permeabilityGamma; transformer neutral point voltage sensor real-time monitoring main transformer neutral point voltage Ufh(0)And the neutral point voltage U of the main transformer is converted intofh(0)Transmitting the data to a control system, and acquiring the state of charge (SOC) of the energy storage battery and the super capacitor module in the system; according to Ufh(0)The system is divided into 5 operation states of state 0, state 1, state 2, state 3 and state 4, which are respectively:
state 0: in the state, the SOC of the energy storage battery and the SOC of the super capacitor module is greater than 0.5, and the neutral point of the main transformer has no overvoltage or the overvoltage is recovered to be normal;
state 1: in the state, the SOC of the energy storage battery and the SOC of the super capacitor module are less than 0.5, and the neutral point of the main transformer has no overvoltage or the overvoltage is recovered to be normal; if the overvoltage is recovered to be normal, a second direct current converter between the energy storage battery and the direct current bus is locked, a third direct current converter between the super capacitor module and the direct current bus is locked, the photovoltaic battery passes through the first direct current converter, and all power generated by the photovoltaic battery is input into a power grid through the photovoltaic inverter;
state 2: in the state, the photovoltaic cell keeps maximum power tracking control, the second direct current converter connected with the energy storage cell is locked temporarily, the super capacitor module is converged into a direct current bus through the third direct current converter, and the third direct current converter is controlled to enable the super capacitor module to enter charging control;
state 3: the photovoltaic cell gradually reduces the photovoltaic permeability through the first direct current converter, the direct current bus and the grid-connected inverter, and the photovoltaic cell respectively carries out stage charging on the energy storage cell and the super capacitor module through the first direct current converter, the direct current bus, the second direct current converter and the third direct current converter with the residual power; the photovoltaic permeability is the ratio of the output power of the photovoltaic cell to the sum of the load power;
and 4: locking the photovoltaic inverter, simultaneously enabling part of the power generated by the photovoltaic battery to pass through the first direct current converter, the direct current bus, the second direct current converter and the third direct current converter, respectively carrying out stage charging on the energy storage battery and the super capacitor module until the SOC approaches to 1, and directly entering a floating charging working mode if the SOC of the energy storage battery and the super capacitor module approaches to 1;
s2: judge Ufh(0)Whether or not 0 holds: if U is presentfh(0)If 0 is true, the SOC is determined again<0.5, if yes, switching the system to a state 1, otherwise, switching the system to a state 0; if U is presentfh(0)If 0 is not true, the process proceeds to step S3;
s3: judge Ufh(0)Whether a step from 0 occurs: if a step occurs, the system is switched to state 2, and then immediately proceeds to step S4;
s4: judge Ufh(0)Whether < 1.15pu holds: if so, switching the system to state 3; otherwise, the system is switched to state 4.
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Effective date of registration: 20240108 Address after: 224100 North side of Binhe Road and east side of Kangping Road in Dazhong Industrial Park, Dafeng District, Yancheng City, Jiangsu Province Patentee after: Jiangsu Yifeng Intelligent Power Co.,Ltd. Address before: No. 1 Hongjing Avenue, Jiangning Science Park, Nanjing City, Jiangsu Province, 210000 Patentee before: NANJING INSTITUTE OF TECHNOLOGY |