CN103887805B - The asymmetrical voltage control method of small current neutral grounding system - Google Patents
The asymmetrical voltage control method of small current neutral grounding system Download PDFInfo
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- CN103887805B CN103887805B CN201410006023.3A CN201410006023A CN103887805B CN 103887805 B CN103887805 B CN 103887805B CN 201410006023 A CN201410006023 A CN 201410006023A CN 103887805 B CN103887805 B CN 103887805B
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- phase place
- asymmetrical voltage
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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
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
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Abstract
Isolated neutral or the asymmetrical voltage control method through grounding through arc electric power system, can control to the asymmetrical voltage caused due to circuit triphase parameter imbalance and level off to zero.The method, according to the restriction relation between system asymmetrical voltage with the power frequency zero-sequence current injected by any phase in system neutral or three-phase, when system parameters is known, directly can be calculated Injection Current and control asymmetrical voltage to zero; When system parameters is unknown, from the Injection Current of any amplitude and phase place, first changes Injection Current phase place, then change Injection Current amplitude, asymmetrical voltage can be made to level off to zero.The change of the method energy adaptable line argument structure, can control the asymmetrical voltage of small current neutral grounding system flexibly, effectively, maintains electrical network three-phase voltage balance, conscientiously improves fail safe and the economy of operation of power networks.
Description
Technical field
The invention belongs to Three-phase Power Systems voltage balancing control field, relate to a kind of asymmetrical voltage control method of small current neutral grounding system.
The invention particularly relates to a kind of utilize active compensation technical controlling small current neutral grounding system asymmetrical voltage level off to zero control method.
Background technology
China's medium voltage distribution network extensively adopts small current neutral grounding mode, i.e. isolated neutral mode and neutral by arc extinction coil grounding mode.Due to the impact of overhead transmission line manufacturing process, practice of construction and the transposition factor such as not good, the three-phase ground capacitance of general electrical network is unequal mutually.In addition, the mode that electrical network adopts non-three phase to power sometimes is that single-phase load is powered, and this also can cause the three-phase ground capacitance of power distribution network asymmetric.For the medium voltage distribution network adopting small current neutral grounding mode, its neutral point can produce the voltage to earth of certain numerical value.In compensated distribution network, the inductance of arc suppression coil and the three-phase ground capacitance of electrical network form voltage resonance loop, also can aggravate neutral point voltage, the equilibrium relation of possible heavy damage three-phase voltage.
Though this imbalance of three-phase voltage caused by residual voltage can not affect the normal power supply of user, but numerous harm can be caused to equipment such as power circuit, transformer, instrument transformer, lightning arresters, light then make efficiency and the hydraulic performance decline of electric equipment, heavy then make the useful life of electric equipment shorten or cause damage accident, reduce safety, the economic performance of operation of power networks, must be limited.
Regulation in " overvoltage protection of alternating-current electric device and insulation coordination " (DL T620-1997), under normal operating conditions, the long-time electric voltage displacement of neutral point must not exceed 15% of system nominal phase voltage to compensated distribution network.Traditionally, the method for restriction system asymmetrical voltage is mainly Conductor transposition, access coupling capacitor and tuning and suitable its ratio of damping of increase of arc suppression coil etc.But these methods due to exist difficulty of construction large, equipment investment and can not the different shortcoming such as change of adaptable line parameter and structure need be increased, effectively can not limit asymmetrical voltage.At present, this field still lack flexibly, effective asymmetrical voltage control method.
Based on the active compensation technology of active electric power electronic device and pulse modulation technology, carry out control system residual voltage by injecting zero-sequence current to power distribution network.This technology is existing application in the single phase ground fault extinguishing arc of neutral non-effective grounding power distribution network, and it can compensate for failed point residual flow, improves blow-out probability, and after blow-out, controls the resume speed of fault point voltage, prevent arc reignition.Its superior residual voltage control performance is seek new asymmetrical voltage control principle to provide thinking.
Summary of the invention
The technical problem that the present invention solves is: the asymmetrical voltage control technology of small current neutral grounding system.When small current neutral grounding system makes neutral point there is larger voltage (i.e. asymmetrical voltage) due to reasons such as Conductor transposition are insufficient, non-three phase is powered, flexibly, effectively can eliminate system asymmetrical voltage, maintain system three-phase voltage balance.
The technical scheme that technical solution problem of the present invention is taked is: by system neutral or three-phase any one in opposite directions system inject the controlled power frequency zero-sequence current of an amplitude, phase place, control system asymmetrical voltage levels off to zero, maintains system three-phase voltage balance.Process is:
1., when the system of detecting exists asymmetrical voltage, inject initial Injection Current to system immediately
(amplitude is I
1, phase place is
).The system of selection of initial Injection Current:
This initial Injection Current
can be the electric current of any amplitude and phase place, also can by being manually preset as a certain fixing electric current.In addition, the final injection power current of the method for the invention is can be derived from according to theory
for:
In formula,
for the asymmetrical voltage of system during non-Injection Current, C
a, C
b, C
cfor system three-phase ground capacitance.Therefore, for having the system measuring three-phase ground capacitance condition, also can using this calculated value as initial Injection Current
recycling subsequent step eliminates the error caused the aspects such as measurement, calculating, to reduce Injection Current regulation time.
2. fixing Injection Current amplitude is I
1change current phase, determine to make system asymmetrical voltage reach the phase place of Local Minimum
A. establish counter j=1, (amplitude is I to record initial Injection Current
1, phase place is
) time system asymmetrical voltage U
01;
B. establish counter j=2, keep Injection Current amplitude I
1constant, in phase place
basis (is set to a fixed step size
) increase Injection Current phase place and be
record the system asymmetrical voltage U of its correspondence
02if, U
02< U
01, then record phase place change direction coefficient k=0 and proceed to steps d;
C. keep counter j=2, keep Injection Current amplitude I
1constant, in phase place
with step-length on basis
reduce Injection Current phase place
record the system asymmetrical voltage U of its correspondence
02if, U
02> U
01then proceed to step e, otherwise record current phase place change direction coefficient k=1;
D. counter j adds 1, according to phase place change direction, according to phase step
continue to change phase place
the system asymmetrical voltage U that record is corresponding
0jif, U
0j< U
0 (j-1)then return steps d;
E. the phase place making system asymmetrical voltage minimum is determined
for:
3. fixing Injection Current phase place
change current amplitude, determine to make system asymmetrical voltage arrive minimum current amplitude I
f:
A. establish counter j=1, record amplitude is I
1, phase place is
system asymmetrical voltage U corresponding to Injection Current
01;
B. establish counter j=2, keep Injection Current phase place
constant, at amplitude I
1basis increases Injection Current amplitude for I with a fixed step size (being set to Δ I)
2=I
1+ Δ I, records the system asymmetrical voltage U of its correspondence
02if, U
02< U
01, then record amplitude change direction coefficient k=0 and proceed to steps d;
C. keep counter j=2, keep Injection Current phase place
constant, at amplitude I
1basis reduces Injection Current amplitude I with step delta I
2=I
1-Δ I, records the system asymmetrical voltage U of its correspondence
02if, U
02> U
01then proceed to step e, otherwise record current amplitude change direction coefficient k=1;
D. counter j adds 1, according to amplitude change direction, continues to change amplitude I according to amplitude step delta I
j=I
(j-1)+ (-1)
kΔ I, the system asymmetrical voltage U that record is corresponding
0jif, U
0j< U
0 (j-1)then return steps d;
E. the amplitude I making system asymmetrical voltage minimum is determined
ffor: I
f=I
(j-1).
4. continue to system Injection Current
(amplitude is I
f, phase place is
), control asymmetrical voltage and level off to 0.If the amplitude of asymmetrical voltage changes, then by Injection Current this moment
as initial Injection Current
proceed to step 2.
Compared with prior art the invention has the beneficial effects as follows:
The asymmetric medium voltage distribution network imbalance of three-phase voltage caused of circuit triphase parameter can shorten the useful life of electric equipment, easily causes security incident, must be limited.And the existing method of restriction system asymmetrical voltage is owing to existing various shortcoming, asymmetrical voltage can not be controlled flexibly, effectively: (1) rationally replaces, but large to operating electrical network transposition difficulty, and distribution line unusual fluctuation rate is high, DeGrain; (2) make the suitable off-resonance point of arc suppression coil compensation device run, or suitably increase its ratio of damping, reduce the aggravation effect of the right title voltage of arc suppression coil, but limited efficiency, fundamentally can not eliminate asymmetrical voltage; (3) increase special coupling capacitor, make three-phase ground capacitance equal, but need equipment investment be increased, and when line construction, parameter change, can not change immediately thereupon, the uneven degree of three-phase voltage may be increased the weight of.
The small current neutral grounding system asymmetrical voltage control principle that the present invention proposes, progressively adjusts phase place and the amplitude of Injection Current according to the restriction relation of Injection Current and asymmetrical voltage, control asymmetrical voltage levels off to zero.The method of the invention can overcome the various errors occurred in actual motion, accuracy and stability high, and the change of energy adaptable line parameter, structure, when the asymmetric situation of electrical network changes, only Injection Current need be readjusted, just the three-phase equilibrium state of electrical network be can maintain, the economy of electrical network, security performance and the quality of power supply conscientiously can be improved.
Accompanying drawing explanation
Accompanying drawing 1 be resonant earthed system in the asymmetric situation of a certain specific three-phase ground capacitance, the phase place of different amplitude Injection Current and the restriction relation (, in the asymmetric situation of different three-phase ground capacitance, its variation tendency is identical for system) of neutral point voltage;
Accompanying drawing 2 be resonant earthed system in the asymmetric situation of a certain specific three-phase ground capacitance, the amplitude of out of phase Injection Current and the restriction relation (, in the asymmetric situation of different three-phase ground capacitance, its variation tendency is identical for system) of neutral point voltage;
Accompanying drawing 3 for utilize the method for the invention control neutral point voltage level off to 0 oscillogram;
Accompanying drawing 4 is active power compensator system block diagram.
Embodiment
The embodiment of the method for the invention is:
(1) active power compensator
Active full compensate control apparatus is made up of (as shown in Figure 4) a few parts such as data acquisition system, commutation inversion power supply, filter circuit, place in circuit, control units.Data acquisition system is responsible for gathering the every parameters of electric power system needed for controlling, and as asymmetrical voltage, three-phase ground capacitance etc., and gives control unit as feedback quantity; Control unit calculates required Injection Current according to algorithm, and exports applicable PWM voltage wave by the conducting of active electric power electronic device in drive circuit control inverter circuit; The high fdrequency component in filtering PWM ripple is responsible for by filter circuit, and the voltage after filtering provides required Injection Current by suitable place in circuit for system, realizes the control of right title voltage.Active power compensator can or connect afterwards connecting system neutral point in parallel with arc suppression coil, also any one can be in parallel or to connect access from three-phase.
(2) acquisition of neutral point voltage
The three-phase that neutral point voltage is connected to by system neutral or zero sequential potential transformer (TV) directly obtain.
(3) initial Injection Current
selection
Initial Injection Current
can be the electric current of any amplitude and phase place, also can by being manually preset as a certain fixing electric current.In addition, the final injection power current of the method for the invention is can be derived from according to theory
for:
In formula,
for the asymmetrical voltage of system during non-Injection Current, C
a, C
b, C
cfor system three-phase ground capacitance.In actual motion, when this electric current can utilize non-Injection Current, measured asymmetrical voltage and three-phase ground capacitance value calculate, but due to the error of the aspects such as measurement, calculating, this calculated value can exist certain error.Therefore, for having the system measuring three-phase ground capacitance condition, can using this calculated value as initial Injection Current
recycling the method for the invention adjustment Injection Current, significantly can reduce the adjusting range of Injection Current like this, reduce adjustment required time.
(4) measurement of system three-phase ground capacitance value
Gained Injection Current will be calculated as initial Injection Current if select, then need to record system three-phase ground capacitance value, general employing signal injection method: inject alien frequencies signal to system neutral by microcomputer measuring and controlling device, receive the feedback signal from electrical network simultaneously, according to corresponding equivalent circuit and algorithm, calculate the three-phase ground capacitance value of electrical network.The decanting point of current signal injection method can be selected in TV secondary side open delta place, or stands with the neutral point of change, Shunt Capacitor Unit ground connection.
(5) control system asymmetrical voltage levels off to zero, maintains three-phase voltage balance
From initial Injection Current
start, first fixing Injection Current amplitude is I
1change current phase, determine to make system asymmetrical voltage reach the phase place of Local Minimum
fix Injection Current phase place again
change current amplitude, determine to make system asymmetrical voltage arrive minimum current amplitude I
f; Continue to system Injection Current
(amplitude is I
f, phase place is
), control asymmetrical voltage and level off to 0, if the amplitude of asymmetrical voltage changes, then by Injection Current this moment
as initial Injection Current
readjust Injection Current.
The above is only preferred embodiment of the present invention, and be not restriction the present invention being made to other form, any those skilled in the art may utilize the technology contents of above-mentioned announcement to be changed or be modified as the Equivalent embodiments of equivalent variations.But everyly do not depart from technical solution of the present invention content, any simple modification, equivalent variations and the remodeling done above embodiment according to technical spirit of the present invention, still belong to the protection range of technical solution of the present invention.
Claims (2)
1. small current neutral grounding system asymmetrical voltage control method, by injecting the power frequency zero-sequence current of certain amplitude, phase place to system neutral, control system asymmetrical voltage levels off to zero, maintains system three-phase voltage balance, it is characterized in that:
(1) from the initial Injection Current of any amplitude and phase place
start,
amplitude be expressed as I
1, phase place is expressed as
first fixing Injection Current amplitude is I
1change current phase, determine to make system asymmetrical voltage reach the phase place of Local Minimum
implementation procedure is:
A. establish counter j=1, record initial Injection Current
time system asymmetrical voltage U
01, wherein
amplitude be I
1, phase place is
B. establish counter j=2, keep Injection Current amplitude I
1constant, in phase place
with a fixed step size on basis
increasing Injection Current phase place is
record the system asymmetrical voltage U of its correspondence
02if, U
02< U
01, then record phase place change direction coefficient k=0 and proceed to steps d;
C. keep counter j=2, keep Injection Current amplitude I
1constant, in phase place
with step-length on basis
reduce Injection Current phase place
record the system asymmetrical voltage U of its correspondence
02if, U
02> U
01then proceed to step e, otherwise record current phase place change direction coefficient k=1;
D. counter j adds 1, according to phase place change direction, according to phase step
continue to change phase place
the system asymmetrical voltage U that record is corresponding
0jif, U
0j< U
0 (j-1)then return steps d;
E. the phase place making system asymmetrical voltage minimum is determined
for:
;
(2) fixing Injection Current phase place is again
change current amplitude, determine the current amplitude I making system asymmetrical voltage reach minimum
f, implementation procedure is:
A. establish counter j=1, record amplitude is I
1, phase place is
system asymmetrical voltage U corresponding to Injection Current
01;
B. establish counter j=2, keep Injection Current phase place
constant, at amplitude I
1basis increases Injection Current amplitude for I with certain step delta I
2=I
1+ Δ I, records the system asymmetrical voltage U of its correspondence
02if, U
02< U
01, then record amplitude change direction coefficient k=0 and proceed to steps d;
C. keep counter j=2, keep Injection Current phase place
constant, at amplitude I
1basis reduces Injection Current amplitude I with step delta I
2=I
1-Δ I, records the system asymmetrical voltage U of its correspondence
02if, U
02> U
01then proceed to step e, otherwise record current amplitude change direction coefficient k=1;
D. counter j adds 1, according to amplitude change direction, continues to change amplitude I according to amplitude step delta I
j=I
(j-1)+ (-1)
kΔ I, the system asymmetrical voltage U that record is corresponding
0jif, U
0j< U
0 (j-1)then return steps d;
E. the amplitude I making system asymmetrical voltage minimum is determined
ffor: I
f=I
(j-1).
2. method according to claim 1, is characterized in that:
The system asymmetrical voltage of making is tending towards the final injection power frequency zero-sequence current of 0
for:
In formula,
for the asymmetrical voltage of system during non-Injection Current, C
a, C
b, C
cfor system three-phase ground capacitance.
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| CN201410006023.3A CN103887805B (en) | 2014-01-07 | 2014-01-07 | The asymmetrical voltage control method of small current neutral grounding system |
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| CN201410006023.3A CN103887805B (en) | 2014-01-07 | 2014-01-07 | The asymmetrical voltage control method of small current neutral grounding system |
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| CN103887805B true CN103887805B (en) | 2015-12-02 |
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Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104092228B (en) * | 2014-06-30 | 2016-04-20 | 中国石油大学(华东) | Asymmetrical voltage 2 active control methods of system with non effectively earth ed neutral |
| CN104167749B (en) * | 2014-07-24 | 2016-05-11 | 广东电网有限责任公司电力科学研究院 | A kind of power distribution network three-phase imbalance voltage inhibition method |
| CN104836219B (en) * | 2015-01-20 | 2018-04-06 | 中国矿业大学 | A kind of arc suppression coil tuning new method of variable step |
| CN105974173B (en) * | 2015-09-15 | 2019-03-26 | 长沙理工大学 | A kind of electric current detecting method of single-phase inversion type earthing or grounding means |
| CN106356833A (en) * | 2016-10-12 | 2017-01-25 | 广东电网有限责任公司电力科学研究院 | Power distribution network-based control method for grounding failure suppression device |
| CN107276082B (en) * | 2017-07-05 | 2020-10-02 | 长沙理工大学 | Active voltage reduction safe operation method for ground fault phase of non-effective grounding system |
| CN107508296B (en) * | 2017-07-26 | 2020-03-17 | 国网山东省电力公司莱芜供电公司 | System and method for reducing adjustment time for controlling asymmetric voltage |
| CN111141991B (en) * | 2018-11-05 | 2021-12-24 | 李景禄 | Method suitable for improving high-resistance grounding fault handling capacity of asymmetric power grid |
| CN110323766B (en) * | 2019-07-19 | 2023-05-09 | 云南电网有限责任公司电力科学研究院 | Three-phase voltage unbalance treatment method for low-voltage distribution network |
| CN111525441B (en) * | 2020-04-30 | 2021-08-03 | 国网湖南省电力有限公司 | Uninterrupted operation method for operation point |
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| CN201038754Y (en) * | 2007-03-16 | 2008-03-19 | 长沙理工大学 | Distribution network neutral point earthing resistance measuring and control device |
| CN102255326A (en) * | 2011-07-04 | 2011-11-23 | 胡继炜 | Method and system for balancing active power loads |
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