CN208226874U - The dry power supply of the dual-purpose three level low frequency of list/three-phase - Google Patents
The dry power supply of the dual-purpose three level low frequency of list/three-phase Download PDFInfo
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- CN208226874U CN208226874U CN201820678764.XU CN201820678764U CN208226874U CN 208226874 U CN208226874 U CN 208226874U CN 201820678764 U CN201820678764 U CN 201820678764U CN 208226874 U CN208226874 U CN 208226874U
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Abstract
The utility model discloses a kind of dry power supplys of the dual-purpose three level low frequency of list/three-phase, including heating power supply, the input terminal of heating power supply to be connected with main control unit, and the output end of heating power supply is connected with single-phase transformer or three-phase transformer；Heating power supply is in parallel again after first being connected respectively with four sub-control units by four current source modules, and each current source module is in parallel by four NPC tri-level circuits, and single NPC tri-level circuit switches its output single-phase of switch control or three phase modes by list/three-phase；The current-order and interleaved operation clock signal that main control unit generates respectively enter inside each current source module, then the output of driving signal control electric current and voltage is generated by the corresponding sub-control unit of each current source module.The utility model heating efficiency is high, applied widely, is able to achieve list/three-phase output, large-scale power transformer can be dried.
Description
Technical field
The utility model relates to the dry power technique fields of low frequency, more specifically to a kind of dual-purpose three electricity of list/three-phase
The dry power supply of flat low frequency.
Background technique
During transformer field is installed, transformer dampness is prevented to be very important a ring.In recent years, transformer
Voltage class and the ascendant trend of individual capacity are fairly obvious, in order to can satisfy the transformer of voltage levels and large capacity
The requirement of insulation torrefaction is safely operated, and is prolonged its service life as far as possible, and the desiccant dehumidification technology of transformer is a key
The problem of property.
The moisture of typical transformer is mainly collected in insulating board and transformer oil at present, and the two parts are
The main insulating materials of transformer, therefore their water content is of great significance to the safe operation of transformer.When
When water content in insulating materials is excessively high, the insulation resistance that will lead to transformer is reduced, and dielectric loss increases, and the breakdown of medium is strong
Degree also increases with insulation system water content and sharply declines, this can seriously affect the safe operation of transformer, can also when serious
Cause discharge breakdown accident.
In transformer, when manufacture when the internal moisture and operation of transformer other than the moisture of outside intrusion, fortune
The insulation ag(e)ing of oilpaper causes its own that can also generate moisture when row, these moisture participate in again in turn after being absorbed by dielectric
Cellulose degradation ageing process.If water content is bigger, the cracking reaction of cellulose is stronger, so that the degree of polymerization of paper declines
Must be faster, this can accelerate the deterioration of the reduction of insulation system dielectric strength and transformer properties, directly or indirectly shadow
Ring the service life for arriving transformer.Therefore it is generally believed that the water content in transformer interior insulation paper is that influence transformer uses the longevity
One of factor of life can significantly aggravate the aging of transformer when water content is excessively high.
Due to above, the desiccant dehumidification technology of transformer has caused various aspects to include the wide of transformer maintenance department
General concern.Currently, the Transformer on Site installation in China is still dried in vacuo dehumidifying technology using conventional method.This
Heater around kind of drying mode vacuum tank be using air as heat-carrying agent, at atmosheric pressure, by transformer body or around
Gradually heat to 105 DEG C or so, then by hot conduction is passed to inside to group by item heat.Change for capacity only increases heat
Oily circulation time, the pumpdown time and it is quiet put the time, the in-situ processing time is long and inefficiency.And it is very low in environment temperature
In the case of, it is limited by oil filter heating efficiency, transformer oil can only be heated to lower temperature in hot-oil circulation.In this feelings
Under condition, even if extending the hot-oil circulation time, it is also difficult to the drying effect reached.
In view of the above problems, a kind of three level low frequencies baking is proposed in the Chinese patent that publication No. is CN 203690095U
Dry power supply, the program heat Working transformer using three-level inverter module, from inside by transformer body insulating
It is heated to specified temperature, achievees the effect that dry transformer.But the patent is completed dry only with 1 three-level inverter module
Dry power supply, the problems such as will appear underpower, current ripples when handling large oil immersed transformer.And it is most of at present super, special
The main transformer of high voltage substation is all single-phase transformer, and the program can only realize that three-phase exports, be unable to satisfy super, extra-high voltage transformer
The requirement of field drying.But if the design of power supply is dried only for large-scale single-phase transformer, and it will cause the scope of application
The problem of narrow, wasting of resources.
Accordingly, it is desirable to provide a kind of dry power supply of the dual-purpose three level low frequency of list/three-phase, may be implemented single-phase output and three-phase
Two kinds of output modes are exported, can be used in the field drying of large-scale power transformer.
Utility model content
The technical problem to be solved by the present invention is to provide a kind of dry power supply of the dual-purpose three level low frequency of list/three-phase.
The technical scheme adopted by the utility model to solve the technical problem is as follows: constructing a kind of dual-purpose three level of list/three-phase
Low frequency dries power supply, including heating power supply, the input terminal of the heating power supply are connected with main control unit, the heating power supply
Output end is connected with single-phase transformer or three-phase transformer；The heating power supply by four current source modules first respectively with four points
Parallel connection again after unit is connected is controlled, each current source module is by four NPC (Neutral Point Clamped, neutral point pincers
Position) tri-level circuit parallel connection, individually the NPC tri-level circuit switches its output single-phase of switch control or three by list/three-phase
Facies model；A series of frequencies that the main control unit generates are identical and phase difference divides for the driving signal and current-order of 1/2 π
It Jin Ru not divide inside control unit, then generate the output of driving signal control electric current and voltage, NPC tri- by respective sub-control equipment
Each switching device IGBT in level circuit works according to sequential manner.
In the above scheme, the single NPC tri-level circuit includes three-phase tri-level circuit, the three-phase tri-level electricity
The input terminal on road is connected with the output end of the first uncontrollable rectifier bridge, and the input terminal of the three-phase tri-level circuit is not controlled with second also
The output end of rectifier bridge is connected, and the output end of the three-phase tri-level circuit is accessed after being connected with list/three-phase switching switch and loaded
Transformer；The first uncontrollable rectifier bridge is connected in series with the second uncontrollable rectifier bridge, the input terminal of the first uncontrollable rectifier bridge with
The output end of isolating transformer is connected, and the input terminal of the isolating transformer is connected with 380V voltage, second uncontrollable rectifier
The input terminal of bridge is connected with 380V voltage.
In the above scheme, the first uncontrollable rectifier bridge, the second uncontrollable rectifier bridge are made of 6 diodes, wherein
Diode is uncontrollable diode.
In the above scheme, the single NPC tri-level circuit passes through Sine Pulse Width Modulation (Sine Pulse
Width Modulation) control the conducting and shutdown of its switching device IGBT.
In the above scheme, the main control unit is by TM320F28335 chip, outside AD, liquid crystal interface, communication, electricity
Source, current-order module composition.
Implement the dry power supply of the dual-purpose three level low frequency of the utility model list/three-phase, has the advantages that
1, the utility model can switch list/three phase modes of its output of switch control by list/three-phase, can be to each electricity
The single-phase/three-phase transformer of pressure grade is dried, applied widely, solves large capacity single and mutually dries power supply cost height, makes
It is relatively narrow with range, the problem of be easy to causeing the wasting of resources.
2, the utility model uses the control method of crisscross parallel, and each current source module clock is independent mutually, and frequency is complete
Exactly the same, the ripple of system output current is that each current source module output current ripple is offset to the full extent, while defeated
Ripple frequency also rises to N times of single module out, greatly improves the output electric current and power of dry power supply, solves large capacity
Required heating power big problem when transformer dry.
3, each current source module clock is orderly staggered in the utility model, and switching frequency is identical, then system output electricity
The ripple of stream cuts down each current source module output current ripple to greatest extent, not only can guarantee each mould
The precision of steady current of block, and the coupled interference between modules is avoided, it is also equal there is no being generated because of IGBT otherness
Flow problem.
4, heat is from the inside that Working transformer insulate generation, therefore heating efficiency to the utility model when heating
It is very high, time-consuming is short, effect on moisture extraction is significant, and when live winding electrified heating, heating power, which can pass through, adjusts primary side institute
Voltage swing is powered up to be adjusted to meet temperature needs.
In conclusion the utility model heating efficiency is high, and it is applied widely, it is able to achieve list/three-phase output, it can be to large-scale electricity
Power transformer is dried；And the utility model uses the control method of crisscross parallel, and it is existing to solve large-scale power transformer
The problems such as dry power in field is insufficient, current ripples.
Detailed description of the invention
Below in conjunction with accompanying drawings and embodiments, the utility model is described in further detail, in attached drawing:
Fig. 1 is the structural schematic diagram of the dry power supply of the dual-purpose three level low frequency of the utility model list/three-phase；
Fig. 2 is the power supply ripple control effect figure that the utility model uses interleaved operation control model；
Fig. 3 is the structural schematic diagram of single NPC tri-level circuit；
Fig. 4 is the equivalent circuit diagram of a single NPC tri-level circuit wherein phase；
Fig. 5 is the SPWM control figure of single NPC tri-level circuit；
Fig. 6 is field drying process (single-phase) equivalent circuit diagram.
In figure: three-phase tri-level circuit 1, the first uncontrollable rectifier bridge 2, the second uncontrollable rectifier bridge 3, list/three-phase switching switch
4, isolating transformer 5.
Specific embodiment
For a clearer understanding of the technical features, objectives and effects of the utility model, now control attached drawing is detailed
Illustrate specific embodiment of the present utility model.
As shown in Figure 1, the utility model provides a kind of dry power supply of the dual-purpose three level low frequency of list/three-phase, including heating electricity
The input terminal in source, heating power supply is connected with main control unit, the output end of heating power supply and load (single-phase transformer or three phase transformations
Depressor) it is connected.Heating power supply is connected by current source module 1 with sub-control unit 1, current source module 2 is connected with sub-control unit 2, electricity
Stream parallel connection again after source module 3 is connected with sub-control unit 3, current source module 4 is connected with sub-control unit 4.Each current source module by
The NPC tri-level circuit of four 125A is in parallel, and the output electric current of each current source module can achieve 500A, it is known that, this is practical
Novel in parallel using 4 500A current source modules, out-put supply can reach 2000A.Main control unit is by TM320F28335 core
Piece, outside AD, liquid crystal interface, communication, power supply, current-order module composition.
4 current source modules use the control method of interleaved operation, it may be assumed that when equipment work, current-order module is generated
A series of frequencies are identical and phase difference is that the driving signal of 1/2 π (2 π/4) and current-order respectively enter inside point control unit,
The output of driving signal control electric current and voltage, each derailing switch in NPC tri-level circuit are generated by respective sub-control equipment again
Part IGBT works according to sequential manner, and driving signal frequency is consistent, and phase angle mutually staggers and alternate conduction.This interleaved operation
Control method has the advantages that inhibit output current ripple, reduce output filter capacity and expand system power output, power supply
Ripple control effect picture is as shown in Fig. 2, be analyzed from principle, and each current source module clock is independent mutually in the utility model,
Frequency is identical, the utility model output electric current ripple be each current source module output current ripple to the full extent
It offsets, while output ripple frequency also rises to N times of single current source module.
As shown in figure 3, single NPC tri-level circuit utilizes ac-dc-ac transform principle comprising three-phase tri-level circuit
1, the input terminal of three-phase tri-level circuit 1 is connected with the output end of the first uncontrollable rectifier bridge 2, the input of three-phase tri-level circuit 1
End is also connected with the output end of the second uncontrollable rectifier bridge 3, and output end and the list/three-phase of three-phase tri-level circuit 1 switch 4 phase of switch
Load transformer is accessed after even.First uncontrollable rectifier bridge 2 is connected in series with the second uncontrollable rectifier bridge 3, the first uncontrollable rectifier bridge 2 it is defeated
Enter end to be connected with the output end of isolating transformer 5, the input terminal of isolating transformer 5 is connected with 380V voltage, the second uncontrollable rectifier
The input terminal of bridge 3 is connected with 380V voltage.First uncontrollable rectifier bridge, the second uncontrollable rectifier bridge are made of 6 diodes, wherein
Diode is uncontrollable diode.
Single NPC tri-level circuit switches its output single-phase of switch control or three phase modes by list/three-phase: as list/tri-
When mutually switching switch 4 disconnects, the output of three-phase tri-level circuit 1 is three phase low frequency voltage, for three-phase transformer to be dried；
When list/three-phase switching switch 4 is closed, the output of three-phase tri-level circuit 1 is single-phase low-frequency voltage, be used for single-phase transformer into
Row drying.
Single NPC tri-level circuit is considered as the group of the single-phase tri-level circuit of three 120 ° of output voltage phase mutual deviations
It closes, has the characteristics that output power, switching loss are small, harmonic content is few.Fig. 4 is a single NPC tri-level circuit wherein phase
Equivalent circuit.Assuming that capacitance voltage has been in equilibrium state, the working principle of Fig. 4 is mainly as follows:
(1) work as T1、T2Conducting, T3、T4When shutdown, if ignoring tube voltage drop, the output end voltage of the phase is U=Ud/2；
At this moment there are two types of situations, first is that if load current is to flow to load end from inverter, capacitor C1By being responsible for T1、
T2Electric discharge；Second situation is load current from load end inflow inverter, then electric current flows through and supervisor T1、T2Afterflow in parallel
Diode D1、D2To capacitor C1It charges.
(2) work as T2、T3Conducting, T1、T4When shutdown, if ignoring tube voltage drop, the output end voltage of the phase is U=0；This
When again there are two types of situation, the first situation is that load current from inverter flows to load end, then electric current flows through catching diode D5、
It is responsible for T2To capacitor C1It charges；Second situation is load current from load end inflow inverter, then electric current flows through supervisor
T3, again pass through catching diode D6, to capacitor C2It charges.
(3) work as T3、T4Conducting, T1、T2When shutdown, if ignoring tube voltage drop, the output end voltage of the phase is U=-Ud/2；
At this moment again there are two types of situation, the first situation is that load current from inverter flows to load end, and at this moment electric current flows through and supervisor T3、
T4Sustained diode in parallel3、D4To capacitor C2Charging, second situation are that load current from load end flows to inverter, this
When capacitor C2By being responsible for T3、T4Externally electric discharge.
Above-mentioned working principle table 1 is showed are as follows:
The relationship of 1 converter of table output and each switch state
| T1 | T2 | T3 | T4 | Ua | Switch state Sx |
| ON | ON | OFF | OFF | Ud/2 | p |
| OFF | ON | ON | OFF | 0 | o |
| OFF | OFF | ON | ON | -Ud/2 | n |
At this moment, if defining three switch state variable Sa、Sb、Sc, indicate the output state of each phase bridge arm respectively, at this moment
The output phase voltage of each phase can indicate are as follows:
(1) S in formula is the switch function of x phase, value are as follows:
If therefore three kinds of level can be exported from every phase that above analysis can be seen that NPC three-level inverter,
If so three is superimposed, so that it may export 33=27 kinds of level combinations, 27 kinds of level combinations states respectively correspond 27 kinds not
Same converter switches state.
Single NPC tri-level circuit controls the conducting and shutdown of its switching device IGBT by Sine Pulse Width Modulation.
Fig. 5 is the SPWM control figure of single NPC tri-level circuit.Because the positive half-wave of modulating wave and negative half-wave have symmetry,
It is analyzed by taking positive half-wave as an example.UtriFor the peak-to-peak value of triangular carrier, UmFor the instantaneous value of cosine-modulation wave, according to triangle
The theory of Carrier-based PWM modulation, will generate being switched on or off for corresponding each switching tube with the point of intersection of modulating wave in triangular carrier
Signal, switch state are discontinuous.
Formula (2) can simplify in the positive half-wave of modulating wave are as follows:
To uxIn switch periods TsInside average, such as formula (4):
And the switch periods average value of switch function S:
In formula (5), D is a switch periods TsInterior duty ratio.
As can be seen from Figure 5:
Formula (4), formula (5) are substituted into formula (6), can be obtained:
The modulating wave U it can be seen from formula (7)mWith tri-level circuit output voltage UxBetween transmission function are as follows:
It can make similar derivation due to symmetry in modulating wave negative half-cycle.Same available transmitting letter as above
Number.As can be seen that when single NPC tri-level circuit is modulated using SPWM, when carrier frequency is very high, single tri- level of NPC electricity
Road is considered as the proportional component that a proportionality coefficient is K.
The practical application mode of the utility model at the scene is illustrated below.The utility model drying process at the scene
In (single-phase) equivalent circuit diagram as shown in fig. 6, by NPC tri-level circuit be equivalent to voltage effective value be UxAlternating-current voltage source,
Transformer is reduced to equivalent circuit when short circuit.At the scene in transformer winding electrification desiccant dehumidification, NPC tri-level circuit is made
It connects for power supply in transformer primary side, secondary circuit short-circuit, primary, secondary winding is made to flow through electric current, generated heat using winding and iron core
Mode Working transformer is heated, from inside by Working transformer body insulation be heated to specified temperature, using
Vacuumize take away body insulation in moisture to achieve the effect that dry transformer.
If load transformer be it is single-phase, transformer is connected to single-phase output, by current-order module issue driving signal
It respectively enteing inside point control unit, control unit controls list/three-phase switching switch 4 and is closed, while three-phase tri-level circuit 1
The low-frequency voltage phase of each phase output is consistent, and output is low frequency single-phase voltage at this time, can be used for heating single-phase transformer.
If load transformer is three-phase, it is connected with the output of A, B, C three-phase, driving signal is issued by current-order module
It respectively enteing inside point control unit, control unit controls list/three-phase switching switch 4 and disconnects, while three-phase tri-level circuit 1
The low-frequency voltage phase difference of each phase output is 120 °, and output is low frequency three-phase voltage at this time, can be used for heating three-phase transformer.
In Fig. 6, RkWith XkThe respectively short-circuit resistance and short-circuit reactance of transformer, electric current i are short circuit current at this time,
It can obtain:
Formula (8) are substituted into formula (9),
Load loss P when the heat Q of for transformer dehumidifying at this time is transformer short-circuitkIt is produced by heating time t
Raw heat, load loss PkIt may be expressed as:
By heat Q caused by time t are as follows:
Formula (12) gives the heat generated when transformer being dried using NPC tri-level circuit and SPWM is controlled
When modulating wave UmRelationship, provide foundation for the real-time control of the utility model.
The embodiments of the present invention are described above in conjunction with attached drawing, but the utility model is not limited to
The specific embodiment stated, the above mentioned embodiment is only schematical, rather than restrictive, this field it is common
Technical staff is not departing from the utility model aims and scope of the claimed protection situation under the enlightenment of the utility model
Under, many forms can be also made, these are belonged within the protection of the utility model.
Claims (5)
1. a kind of dry power supply of the dual-purpose three level low frequency of list/three-phase, which is characterized in that including heating power supply, the heating power supply
Input terminal be connected with main control unit, the output end of the heating power supply is connected with single-phase transformer or three-phase transformer；Institute
State in parallel again after heating power supply is first connected with four sub-control units respectively by four current source modules, each current source module
In parallel by four NPC tri-level circuits, the single NPC tri-level circuit is single by its output of list/three-phase switching switch control
Phase or three phase modes；A series of frequencies that the main control unit generates are identical and driving signal and electric current that phase difference is 1/2 π
Instruction respectively enter inside point control unit, then by respective sub-control equipment generate driving signal control electric current and voltage it is defeated
Out, each switching device IGBT in NPC tri-level circuit works according to sequential manner.
2. the dry power supply of the dual-purpose three level low frequency of list/three-phase according to claim 1, which is characterized in that the single NPC
Tri-level circuit includes three-phase tri-level circuit, the output of the input terminal of the three-phase tri-level circuit and the first uncontrollable rectifier bridge
End is connected, and the input terminal of the three-phase tri-level circuit is also connected with the output end of the second uncontrollable rectifier bridge, three electricity of three-phase
The output end on ordinary telegram road accesses load transformer after being connected with list/three-phase switching switch；The first uncontrollable rectifier bridge and second
Uncontrollable rectifier bridge is connected in series, and the input terminal of the first uncontrollable rectifier bridge is connected with the output end of isolating transformer, the isolation
The input terminal of transformer is connected with 380V voltage, and the input terminal of the second uncontrollable rectifier bridge is connected with 380V voltage.
3. the dry power supply of the dual-purpose three level low frequency of list/three-phase according to claim 2, which is characterized in that described first is not
Control rectifier bridge, the second uncontrollable rectifier bridge are made of 6 diodes, and wherein diode is uncontrollable diode.
4. the dry power supply of the dual-purpose three level low frequency of list/three-phase according to claim 2, which is characterized in that the single NPC
Tri-level circuit controls the conducting and shutdown of its switching device IGBT by Sine Pulse Width Modulation.
5. the dry power supply of the dual-purpose three level low frequency of list/three-phase according to claim 1, which is characterized in that the main control
Unit is made of TM320F28335 chip, outside AD, liquid crystal interface, communication, power supply, current-order module.
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| CN201820678764.XU CN208226874U (en) | 2018-05-08 | 2018-05-08 | The dry power supply of the dual-purpose three level low frequency of list/three-phase |
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| CN201820678764.XU CN208226874U (en) | 2018-05-08 | 2018-05-08 | The dry power supply of the dual-purpose three level low frequency of list/three-phase |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108418440A (en) * | 2018-05-08 | 2018-08-17 | 国网电力科学研究院武汉南瑞有限责任公司 | The dual-purpose three level low frequency of list/three-phase dries power supply |
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2018
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108418440A (en) * | 2018-05-08 | 2018-08-17 | 国网电力科学研究院武汉南瑞有限责任公司 | The dual-purpose three level low frequency of list/three-phase dries power supply |
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