CN110112743A - A kind of isolated form variable-frequency transformer and its starting control and expansion method - Google Patents
A kind of isolated form variable-frequency transformer and its starting control and expansion method Download PDFInfo
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- CN110112743A CN110112743A CN201910270897.2A CN201910270897A CN110112743A CN 110112743 A CN110112743 A CN 110112743A CN 201910270897 A CN201910270897 A CN 201910270897A CN 110112743 A CN110112743 A CN 110112743A
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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
- H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
- H02J3/08—Synchronising of networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/22—Current control, e.g. using a current control loop
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/34—Arrangements for starting
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/20—Arrangements for starting
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- Control Of Ac Motors In General (AREA)
- Control Of Eletrric Generators (AREA)
- Motor And Converter Starters (AREA)
Abstract
The present invention relates to a kind of isolated form variable-frequency transformer and its starting control and expansion methods, the transformer includes synchronous motor and wound rotor asynchronous machine, it is connected between synchronous motor and wound rotor asynchronous machine by shaft coupling unit, the secondary side of the transformer is directly led out by the stator winding of synchronous motor, its primary side is directly led out by the stator winding of wound rotor asynchronous machine, it is also connected between the stator winding of wound rotor asynchronous machine and its rotor windings and is provided with back-to-back converter, the rotor windings of wound rotor asynchronous machine, which are also connected with, is provided with start unit, start unit and back-to-back converter with detect and control unit and connect.Compared with prior art, the present invention, which has, can be achieved secondary side variable voltage variable frequency, it can the frequency reference value according to needed for the flexible configuration of application, secondary side variable frequency range is wider, primary side, pair are in electromagnetic isolation and pair not by power electronics harmonic pollution, overload capacity is relatively strong, it can be achieved that the advantages that band of synchronous motor carries starting.
Description
Technical field
The present invention relates to transformer technology field, more particularly, to a kind of isolated form variable-frequency transformer and its starting control and
Expansion method.
Background technique
There are mainly two types of schemes for converter technique between existing AC energy, the first is constituted by by power electronic devices
Converter plant, the electric energy of commonly required transformation needs all through converter plant, i.e., the power of converter plant be equal to convert it is electric
The power of energy；Second scheme is variable-frequency transformer, using wire-wound asynchronous motor three-phase rotor windings and threephase stator around
Group respectively constitutes the primary and secondary side of variable-frequency transformer, and using the rotor of speed-changing driving device driving wire-wound asynchronous motor.
Two schemes are compared, and the total power variable-frequency solutions control freedom degree highest being made of power electronic devices may be implemented very wide
Variable frequency range；Existing variable-frequency transformer scheme is mainly used for connecting the close Asynchronous Communication power supply of two frequencies, passes through speed change
Driving device controls the power flowcontrol between revolving speed two Asynchronous Communication power supplys of realization.The present invention and above-mentioned variable-frequency transformer essence
On belong to rotary transformer, therefore the implementation that above-mentioned variable-frequency transformer is and the present invention is most similar.
Major defect existing for existing variable-frequency transformer is: 1. frequency conversion a reference values are fixed.When one side frequency determines substantially,
Another side frequency is only capable of changing on the basis of the frequency.It is assumed that primary side frequency is f, then secondary side frequency can only float up and down in f；
2. variable frequency range is relatively narrow.Its suitable rotary speed working range is not suitable for primary side and pair near 0 speed (revolutional slip close to 1)
The widely different situation of side frequency.This is because when primary and secondary side frequency difference is very big, the slip of wire-wound asynchronous motor
Rate absolute value is smaller, and the slip power that rotor windings flow through is smaller, and most of power needs (usually to adopt by speed-changing driving device
With power electronic devices constitute converter plant) mechanical output provide, cause the capacity requirement of speed-changing driving device to increase；3.
There are electromagnetic coupling between existing variable-frequency transformer primary and secondary side, the disturbance on any one side can generate direct shadow to another side
It rings.
Summary of the invention
It is an object of the present invention to overcome the above-mentioned drawbacks of the prior art and provide a kind of isolated form frequency conversions to become
Depressor and its starting control and expansion method, the isolated form variable-frequency transformer, frequency reference value can be according to variable-frequency transformer
Parameter flexible configuration, variable frequency range be wider, primary side/pair side electromagnetic isolation.It functionally sees, existing variable-frequency transformer is mainly answered
It is to contact Asynchronous Communication power grid similar in two frequencies, and main application scenarios of the invention are frequency controls with scene, i.e., one
End is power grid, and the other end is alternating current generator.
The purpose of the present invention can be achieved through the following technical solutions:
A kind of isolated form variable-frequency transformer, the transformer include synchronous motor and wound rotor asynchronous machine, the synchronization
It is connected between motor and the wound rotor asynchronous machine by shaft coupling unit, the secondary side of the transformer is by the synchronous motor
Stator winding directly lead out, primary side is directly led out by the stator winding of the wound rotor asynchronous machine, the coiling turn
It is also connected between the stator winding of sub- asynchronous machine and its rotor windings and is provided with back-to-back converter, it is described wound-rotor asynchronous
The rotor windings of motor, which are also connected with, is provided with start unit, the start unit and the back-to-back converter with detection and
Control unit connection can be continuously adjusted with frequency in secondary side generation voltage by control and have exchanging for constant voltage and frequency ratio characteristic
Voltage, the back-to-back converter include machine-side converter and grid side converter, and the back-to-back converter passes through the pusher side
Converter is connected with the rotor windings of the wound rotor asynchronous machine, by the grid side converter through configuration may be selected
Transformer be connected with the stator winding of the wound rotor asynchronous machine.
Further, the start unit includes breaker, three-phase rectification bridge, fixed resistance and variable resistance, described solid
Determine resistance and the variable resistance is connected in parallel in the DC terminal of the three-phase rectification bridge, the exchange end of the three-phase rectification bridge
Be connected to the rotor windings of the wound rotor asynchronous machine by the breaker, the variable resistance include full control switch and
Fixed value resistance, the fixed value resistance and the full control switch are connected in series, and the three-phase rectification bridge is made of multiple diodes.
Further, the synchronous motor uses permanent magnet synchronous motor or electric excitation synchronous motor, when the synchronous motor
When for electric excitation synchronous motor, the DC bus bridging of the back-to-back converter is connected with synchro generator excitation unit.
Further, the ac frequency a reference value of the transformer secondary, its calculation formula is:
f0=pSGf1/(pWRIMngb)
In formula, f0For ac frequency a reference value, f1For primary side ac frequency, pSGFor the number of pole-pairs of synchronous motor, ngb
For shaft coupling unit gear ratio, pWRIMFor the number of pole-pairs of wound rotor asynchronous machine.
Further, wound rotor asynchronous machine revolving speed is controlled by back-to-back converter working normally in the range of speeds
Variation can obtain voltage on the secondary side of isolated form variable-frequency transformer and frequency is continuously adjustable and with constant voltage and frequency ratio characteristic
Alternating voltage, the wherein calculation formula of the secondary side frequency of the transformer are as follows:
In formula, f is secondary side frequency, ωWRIMFor wound rotor asynchronous machine revolving speed.
Further, the adjustable extent of the secondary side frequency of the transformer are as follows:
(1-smax)f0< f < (1+smax)f0
smax=UVSC/(kr/sUs)
In formula, UVSCFor the maximum a.c. voltage virtual value that back-to-back converter AC port can be provided, kr/sFor coiling
The ratio between rotor asynchronous motor rotor windings the number of turns and stator winding circle, UsIt is even handed over by wound rotor asynchronous machine stator winding
The voltage in galvanic electricity source.
The present invention also provides a kind of starting control method using the isolated form variable-frequency transformer, starting controls
Method by the start unit realize predetermined acceleration starting, by isolated form from stationary state accelerate to work normally revolving speed after
It switches to and is controlled by the back-to-back converter, comprising the following steps:
Step 1: by the grid side converter in the back-to-back converter through power grid vector controlled to DC bus electricity
Appearance is pre-charged and is stablized makes the machine-side converter in the back-to-back converter be in blocking in its rated value；
Step 2: the revolving speed for detecting and controlling wound rotor asynchronous machine described in unit real-time detection simultaneously judges whether
Less than revolving speed is worked normally, if being judged as YES, keeps the circuit breaker closing in the start unit to merge and remain described back-to-back
The blocking of machine-side converter in current transformer；
Step 3: if being judged as NO, switching the full control in the variable resistance in the start unit in an off state same
When release the blocking of machine-side converter in the back-to-back converter and the arrow using the wound rotor asynchronous machine
Amount control disconnects the breaker in the start unit after so that it is worked normally a period of time, so far isolated form variable-frequency transformer opens
It is dynamic to complete.
Preferably, the step 2 specifically includes: the revolving speed for the wound rotor asynchronous machine that will test passes through low pass
It filters out and takes differential after noise and the acceleration reference value of the revolving speed after differential and the wound rotor asynchronous machine will be taken to pass through
Error the full control switch in the variable resistance in the start unit is obtained compared with triangular carrier after pi regulator
Pulse-width signal.
The present invention also provides the expansion method using the isolated form variable-frequency transformer, which includes will be more
The primary and secondary side for covering isolated form variable-frequency transformer is in parallel respectively or using distributing means for power supply that the more wound rotors are different
It walks after the power on the mechanical rotating shaft of motor collects to drag a synchronous motor.
The corresponding control method for coordinating of the expansion method are as follows: select a set of isolated form variable-frequency transformer as main transformer frequency
Transformer, remaining each set as from variable-frequency transformer, adopt by the d axis of the machine-side converter vector controlled of the main transformer frequency power transformer
With der Geschwindigkeitkreis-torque ring-electric current loop three close-loop control, the reference value of der GeschwindigkeitkreisAccording to secondary side ac frequency reference value
f*Setting, it may be assumed that
The d axis of the machine-side converter vector controlled from variable-frequency transformer uses torque closed loop-bicyclic control of current closed-loop
System, torque instruction are allocated according to setting principle, it may be assumed that the general power P that Duo Taocong variable-frequency transformer is shared should meet
Pe∑*(m-1)/m≤P<Pe∑, wherein m is the total tricks of isolated form variable-frequency transformer, Pe∑To cover the transmitting of isolated form variable-frequency transformer more
General power.
Compared with prior art, the invention has the following advantages that
(1) energy in bidirectional flow can be achieved, it can the frequency reference value according to needed for the flexible configuration of application and frequency conversion model
It encloses, is based on above-mentioned constant voltage and frequency ratio feature, the main application of isolated form variable-frequency transformer is to drag separate unit or more by secondary side
Alternating current generator realizes the open loop constant voltage constant frequency control of separate unit or more alternating current generators, is suitable for ventilation blower, changes the speed adjusting performances such as spinning
Multiple motor variable frequency and speed regulating occasion of less demanding.
(2) wider variable frequency range can be achieved, and required back-to-back converter capacity is only Smax*Pn, wherein PnFor every
Rated capacity (the S of release variable-frequency transformermaxTypical value be 0.3~0.5)
(3) predetermined acceleration starting may be implemented in the start unit disclosed in, not only limits detent torque, startup power
And starting current, and the alternating voltage that frequency slowly rises can be established on the secondary side of isolated form variable-frequency transformer, therefore
Secondary side can realize that the band of synchronous motor carries starting.
(4) primary side of transformer of the present invention, secondary side electromagnetic isolation have stronger overload capacity, and secondary side is not by electric power
Electronics harmonic pollution.
Detailed description of the invention
Fig. 1 is the isolated form variable-frequency transformer structural schematic diagram using permanent magnet synchronous motor；
Fig. 2 is the isolated form side frequency transformer device structure schematic diagram using electric excitation synchronous motor；
Fig. 3 is the flow diagram of the starting control of isolated form variable-frequency transformer；
Fig. 4 is the parallel extended connection schematic diagram of more set isolated form variable-frequency transformers；
Fig. 5 is the dilatation connection schematic diagram using distributing means for power supply；
Fig. 6 is the phase of the isolated form variable-frequency transformer in present invention emulation when two load synchronous motors are zero load
Closing Parameters variation schematic diagram, wherein Fig. 6-a is rotation speed change schematic diagram, and Fig. 6-b is secondary side frequency and voltage change schematic diagram,
The variation schematic diagram of Fig. 6-c pair side load motor revolving speed, Fig. 6-d are the variation schematic diagram of secondary side three-phase voltage；
Fig. 7 is the correlation of the isolated form variable-frequency transformer in the present invention when two load synchronous motors have load torque
Parameters variation schematic diagram, wherein Fig. 7-a is rotation speed change schematic diagram, and Fig. 7-b is secondary side frequency and voltage change schematic diagram, figure
The variation schematic diagram of 7-c pair side load motor revolving speed, Fig. 7-d are the variation schematic diagram of secondary side three-phase voltage.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiment is a part of the embodiments of the present invention, rather than whole embodiments.Based on this hair
Embodiment in bright, those of ordinary skill in the art's every other reality obtained without making creative work
Example is applied, all should belong to the scope of protection of the invention.
Embodiment
The embodiment of the present invention includes the composition of isolated form variable-frequency transformer, starting method and expansion methods.
First part: isolated form variable-frequency transformer
Isolated form variable-frequency transformer with lower component by being constituted: a 1. wound rotor asynchronous machine；2. a synchronous motor,
It can be permanent magnet synchronous motor or electric excitation synchronous motor, further include synchro generator excitation list when using electric excitation synchronous motor
Member；3. shaft coupling unit includes shaft coupling and optional gearbox；4. back-to-back converter becomes comprising grid side converter and pusher side
Parallel operation；5. detecting and controlling unit；6. transformer, it is therefore an objective to the voltage class of back-to-back voltage converter is reduced, it can root
It chooses whether to be equipped with according to needs；7. start unit includes breaker T1, be made of diode three-phase uncontrollable rectifier bridge, fixation
Resistance and controllable resistor.Wherein fixed resistance R1Using the biggish resistance of resistance value, it is therefore an objective to make wound rotor during startup
The rotor windings of asynchronous machine keep access；Controllable resistor by controlling switch T entirely2With the lesser resistance R of resistance value2It is composed in series, can lead to
Cross control T2Adjust detent torque.
Using permanent magnet synchronous motor isolated form variable-frequency transformer as shown in Figure 1, using the isolation of electric excitation synchronous motor
Type variable-frequency transformer is as shown in Figure 2.The synchro generator excitation unit that Fig. 2 is provided is connected across the DC bus of back-to-back converter, is
A kind of topological mode of recommendation.
The primary side of isolated form variable-frequency transformer is connected with the stator winding of wound rotor asynchronous machine, wound-rotor asynchronous electricity
The rotor windings of machine are connected across primary side through back-to-back converter and optional transformer, and primary side is usually connect with power grid；Isolated form
It is drawn by the stator winding of synchronous motor on the secondary side of variable-frequency transformer.Start unit is connected to the rotor of wound rotor asynchronous machine
Winding, for starting variable-frequency transformer.Shaft coupling unit is used to connect the shaft of synchronous motor and wound rotor asynchronous machine, speed change
Gear-box is the selectable unit (SU) of shaft coupling unit, the frequency reference of the secondary side alternating current of design that can be more flexible using change gear box
Value.It detects and controls unit and applies control for start unit and back-to-back converter.
It is assumed that the number of pole-pairs of wound rotor asynchronous machine is p in isolated form variable-frequency transformerWRIM, the number of pole-pairs of synchronous motor
For pSG, change gear box gear ratio 1:ngb(the case where not using change gear box is with ngb=1 indicates).In back-to-back converter
Control action under, the revolving speed of wound rotor asynchronous machine can be in a certain revolutional slip range | s | < SmaxInterior consecutive variations,
Middle smax=UVSC/(kr/sUs), UVSCFor the maximum a.c. voltage virtual value that back-to-back converter AC port can be provided, kr/s
For the ratio between wound rotor asynchronous machine rotor windings the number of turns and stator winding circle, UsFor wound rotor asynchronous machine stator winding
The voltage of connected AC power source.
The important technological parameters on isolated form variable-frequency transformer pair side are as follows:
The normal work range of speeds of wound rotor asynchronous machine is [ω in isolated form variable-frequency transformer1, ω2], wherein
ω1=(1-smax)2πf1/pWRIM, ω2=(1+smax)2πf1/pWRIM, unit rad/s.
The ac frequency a reference value f on isolated form variable-frequency transformer pair side0(unit Hz),
f0=pSGf1/(pWRIMngb)
The ac frequency on isolated form variable-frequency transformer pair side can be in frequency reference value f0Up and down adjustment.
The adjustable extent of isolated form variable-frequency transformer pair side frequency are as follows:
(1-smax)f0< f < (1+smax)f0
Isolated form variable-frequency transformer pair side frequency f and wound rotor asynchronous machine rotational speed omegaWRIMBetween relationship:
In the range of speeds ω of wound rotor asynchronous machine1To ω2Between any rotational speed omegaWRIMUnder, isolated form frequency conversion becomes
The frequency on depressor pair side isOpen circuit phase voltage is ωWRIMψ/ngb, for permanent magnet synchronous motor, ψ is permanent magnet
Linkage coefficient, unit V*s/rad；For electric excitation synchronous motor, ψ is exciting current ifAct on rotor windings generation
Linkage coefficient.As it can be seen that isolated form variable-frequency transformer can realize the variable voltage variable frequency of secondary side alternating current, and frequency and voltage are with constant
Ratio, that is, have the characteristics that constant voltage and frequency ratio.
Second part: the control method of isolated form variable-frequency transformer
The function of detecting and controlling unit is control isolated form variable-frequency transformer.Detection limit includes but is not limited to wound rotor
Rotational Speed of Asynchronous Motor, wound rotor asynchronous machine stator three-phase voltage, wound rotor asynchronous machine rotor three-phase electric current, net side become
Parallel operation three-phase current.The control of isolated form variable-frequency transformer includes starting control and normal operation control.
(1) starting control
Before entering normal operating conditions, isolated form variable-frequency transformer needs to accelerate to what it was worked normally from stationary state
Rotational speed omegaset, ωsetValue range are as follows: (1-smax)2πf1/pWRIM< ωset2 π f of <1/pWRIM.A kind of starting method is as follows:
Step 1: the grid side converter back-to-back in voltage converter is first under the vector controlled of grid voltage orientation
It first completes the precharge of dc-link capacitance and controls its voltage stabilization in rated value, machine-side converter is in blocking；
Step 2: detecting and controlling the rotational speed omega of unit real-time detection wound rotor asynchronous machineWRIMIf revolving speed is lower than
ωsetThen keep T1It is closed and maintains the blocking of machine-side converter.The acceleration reference value of wound rotor asynchronous machine is setFull control switch T in controllable resistor2It is controlled according to Fig. 3.Specifically, working as ωWRIMLess than ωsetWhen, the revolving speed that detects
ωWRIMDifferential is taken after low-pass filtering filters out noise, withError after pi regulator compared with the triangular carrier
To full control switch T2Pulsewidth modulation (PWM) signal；
Step 3: working as ωWRIMGreater than ωsetWhen, make to control switch T entirely by pattern switching2It is in an off state；Pusher side simultaneously
Converter unlocking state and the vector controlled for using wound rotor asynchronous machine stator voltage vector oriented, the d axis of vector controlled
Comprising der Geschwindigkeitkreis, torque ring and electric current loop three close-loop control, wherein der Geschwindigkeitkreis reference value is taken as ωset；The q axis of vector controlled includes
Idle ring and electric current loop, idle reference value are taken as 0.Machine-side converter postpones a period of time (such as after putting into normal operating conditions
50ms) disconnect T1, so far isolated form variable-frequency transformer start completion.
It should be pointed out that the core concept of above-mentioned start-up course is that controllable resistor is used to realize that predetermined acceleration (can be with
It is the acceleration of variation) starting, it switches to after isolated form variable-frequency transformer is accelerated to its rated speed range by becoming back-to-back
Device control is flowed, scope of the invention is still fallen within based on general improve that the thought is made.
(2) control is operated normally
It operates normally in control, T1It remains off.Wound rotor asynchronous machine stator electricity can be used in machine-side converter
The vector controlled of orientation is pressed, the control of d axis includes der Geschwindigkeitkreis, torque ring and electric current loop, wherein wound rotor asynchronous machine revolving speed
Ring reference value is in ω1To ω2Between setting continuously adjusting for secondary side ac frequency and voltage can be achieved；The control of q axis is comprising idle
Ring and electric current loop, idle reference value can be arranged according to power factor.The vector control of grid voltage orientation can be used in grid side converter
System, the control of d axis include DC bus-bar voltage ring, current loop control, and the control of q axis includes idle ring, electric current loop, idle reference
Value can be arranged according to power factor.For the isolated form variable-frequency transformer using electric excitation synchronous motor, synchro generator excitation list
Member can use secondary voltage closed-loop control.Above-mentioned machine-side converter, the vector controlled of grid side converter and synchro generator excitation
The control of unit can use for reference the prior art.
Part III: the parallel extended method of isolated form variable-frequency transformer
Single off-capacity for covering isolated form variable-frequency transformer is caused to meet using need if being limited by design of electrical motor manufacture level
When asking, need to carry out it dilatation, and need between more set isolated form variable-frequency transformers using coordinated control.There are two types of dilatation sides
Method: first method, by the parallel connection respectively of their primary and secondary side, is shown in Fig. 4 using complete isolated form variable-frequency transformer is covered more；
Second method carries out the power on more wound rotor asynchronous machine mechanical rotating shafts to collect rear dragging by distributing means for power supply
A large synchronous machine is moved, sees Fig. 5.Two kinds of parallel extended methods are one in the coordinated control in starting control and normal operation
It causes, specific as follows:
It is assumed that a shared m set isolated form variable-frequency transformer is in parallel, select wherein a set of as main transformer frequency power transformer, remaining is respectively
Set is used as from variable-frequency transformer.In starting control, can only it be completed by the start unit of certain a set of isolated form variable-frequency transformer
Starting, starting can also be completed jointly by the start unit for more covering isolated form variable-frequency transformer (can enhance the band in start-up course to carry
Ability).The isolated form variable-frequency transformer of set more than when operating normally uses principal and subordinate's coordinated control, and wherein main transformer frequency power transformer pusher side becomes
The d axis of parallel operation vector controlled uses " der Geschwindigkeitkreis-torque ring-electric current loop " three close-loop control, the reference value of der GeschwindigkeitkreisAccording to
Secondary side ac frequency reference value f* setting,From the d of variable-frequency transformer machine-side converter vector controlled
Axis uses " torque (power) closed loop-current closed-loop " double -loop control, and torque (power) instruction is divided according to certain algorithm
Match.The overall principle of distribution is to detect the general power P of more set isolated form variable-frequency transformer transmittinge∑, shared from variable-frequency transformer
General power P should meet Pe∑*(m-1)/m≤P<Pe∑, it is proposed that it is taken as P=Pe∑*(m-1)/m.Each set from variable-frequency transformer it
Between value and power reference can using divide equally, can also certain specified is a set of reach rated power after dump power will be distributed
Give down it is a set of, and and so on.The q axis of machine-side converter vector controlled control and grid side converter vector controlled and single set every
The control of release variable-frequency transformer is identical.
The specific simulating, verifying of the embodiment of the present invention is as follows:
The present invention has carried out electromagnetic transient simulation verifying in PSCAD software, and wound rotor is different in isolated form variable-frequency transformer
Walk capacity motor 20MW, permanent magnet synchronous motor capacity 20MW, rated frequency 25Hz, voltage rating 10kV, R in start unit1For
3000 ohm, R2It is 30 ohm, ω is setsetFor 0.9pu, setting starting loop is 0.05pu/s.Isolated form is become in emulation
Frequency power transformer primary side connects industrial frequency AC power grid, and secondary side drags two load synchronous motors, loads the specified appearance of synchronous motor
Measure 2MW, voltage rating 10kV.
Two load synchronous motors are zero load in first group of emulation, start-up course such as Fig. 6-a, Fig. 6-b, Fig. 6-c and
Shown in Fig. 6-d；
Second group of emulation, First load synchronous motor load torque 0.2pu, second synchronous motor load torque
0.3pu, start-up course is as shown in Fig. 7-a, Fig. 7-b, Fig. 7-c and Fig. 7-d；
There are two groups of simulation results it is found that designed isolated form variable-frequency transformer function is correct, secondary side has constant voltage and frequency ratio
Predetermined acceleration starting may be implemented in characteristic, and secondary side can be dragged with the synchronous motor starting carried.
The present invention has carried out preferred consideration from the angle for saving Converter Capacity, uses in isolated form variable-frequency transformer
Wound rotor asynchronous machine and the control of Partial Power current transformer.If the wound rotor asynchronous machine in isolated form variable-frequency transformer replaces
It is changed to other kinds of motor and the corresponding current transformer control of cooperation, still falls within the scope of invention.
Energy in bidirectional flow may be implemented in isolated form variable-frequency transformer, in addition to dragging alternating current on secondary side described in emulation case
Outside motivation, in secondary side access alternating current generator also possibility purposes of the invention.
The above description is merely a specific embodiment, but scope of protection of the present invention is not limited thereto, any
Those familiar with the art in the technical scope disclosed by the present invention, can readily occur in various equivalent modifications or replace
It changes, these modifications or substitutions should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with right
It is required that protection scope subject to.
Claims (10)
1. a kind of isolated form variable-frequency transformer, which is characterized in that the transformer includes synchronous motor and wound rotor asynchronous machine,
It is connected between the synchronous motor and the wound rotor asynchronous machine by shaft coupling unit, the secondary side of the transformer is by described
The stator winding of synchronous motor is directly led out, and primary side is directly led out by the stator winding of the wound rotor asynchronous machine, institute
It states to be also connected between the stator winding of wound rotor asynchronous machine and its rotor windings and is provided with back-to-back converter, the coiling
The rotor windings of rotor asynchronous motor, which are also connected with, is provided with start unit, and the start unit and the back-to-back converter are equal
It is connect with unit is detected and controlled, the back-to-back converter includes machine-side converter and grid side converter, the back-to-back change
Stream device is connected by the machine-side converter with the rotor windings of the wound rotor asynchronous machine, is become by the net side
Parallel operation is connected through the transformer of configuration may be selected with the stator winding of the wound rotor asynchronous machine.
2. a kind of isolated form variable-frequency transformer according to claim 1, which is characterized in that the start unit includes open circuit
Device, three-phase rectification bridge, fixed resistance and variable resistance, the fixed resistance and the variable resistance are connected in parallel in described three
The exchange end of the DC terminal of commutating phase bridge, the three-phase rectification bridge is connected to the wound-rotor asynchronous electricity by the breaker
The rotor windings of machine, the variable resistance include full control switch and fixed value resistance, the fixed value resistance and the full control switch series
Connection connection, the three-phase rectification bridge are made of multiple diodes.
3. a kind of isolated form variable-frequency transformer according to claim 1, which is characterized in that the synchronous motor uses permanent magnetism
Synchronous motor or electric excitation synchronous motor, when the synchronous motor is electric excitation synchronous motor, the back-to-back converter
DC bus bridging is connected with synchro generator excitation unit.
4. a kind of isolated form variable-frequency transformer according to claim 1, which is characterized in that the alternating current of the transformer secondary
Frequency reference value, its calculation formula is:
f0=pSGf1/(pWRIMngb)
In formula, f0For ac frequency a reference value, f1For primary side ac frequency, pSGFor the number of pole-pairs of synchronous motor, ngbFor connection
Axle unit gear ratio, pWRIMFor the number of pole-pairs of wound rotor asynchronous machine.
5. a kind of isolated form variable-frequency transformer according to claim 1, which is characterized in that the secondary side frequency of the transformer
Adjustable extent are as follows:
(1-smax)f0< f < (1+smax)f0
smax=UVSC/(kr/sUs)
In formula, UVSCFor the maximum a.c. voltage virtual value that back-to-back converter AC port can be provided, kr/sFor wound rotor
The ratio between asynchronous machine rotor umber of turn and stator winding circle, UsBy wound rotor asynchronous machine stator winding even alternating current
The voltage in source.
6. a kind of isolated form variable-frequency transformer according to claim 1, which is characterized in that controlled by back-to-back converter
Wound rotor asynchronous machine revolving speed changes in the normal work range of speeds, can obtain on the secondary side of isolated form variable-frequency transformer
Voltage and frequency are continuously adjusted and the alternating voltage with constant voltage and frequency ratio characteristic, the wherein calculating of the secondary side frequency of the transformer
Formula are as follows:
In formula, f is secondary side frequency, ωWRIMFor wound rotor asynchronous machine revolving speed.
7. a kind of starting control method using the isolated form variable-frequency transformer as described in any one of claim 1~6,
It is characterized in that, which realizes that predetermined acceleration starts by the start unit, by isolated form from stationary state
It accelerates to after working normally revolving speed to switch to and be controlled by the back-to-back converter, comprising the following steps:
Step 1: by the grid side converter in the back-to-back converter through power grid vector controlled to dc-link capacitance into
Line precharge is simultaneously stablized in its rated value, and the machine-side converter in the back-to-back converter is made to be in blocking；
Step 2: the revolving speed for detecting and controlling wound rotor asynchronous machine described in unit real-time detection simultaneously judges whether to be less than
Revolving speed is worked normally, if being judged as YES, keeps the circuit breaker closing in the start unit to merge and maintains the back-to-back unsteady flow
The blocking of machine-side converter in device；
Step 3: if being judged as NO, so that the full control in the variable resistance in the start unit is switched in an off state while solving
Blocking except the machine-side converter in the back-to-back converter and the vector control using the wound rotor asynchronous machine
System disconnects the breaker in the start unit after so that it is worked normally a period of time, so far isolated form variable-frequency transformer has started
At.
8. a kind of starting control method of isolated form variable-frequency transformer according to claim 7, which is characterized in that the step
Rapid 2 specifically include: the revolving speed for the wound rotor asynchronous machine that will test takes differential after low-pass filtering filters out noise
And by take the acceleration reference value of the revolving speed after differential and the wound rotor asynchronous machine through error after pi regulator
The pulse-width signal of the full control switch in the variable resistance in the start unit is obtained compared with triangular carrier.
9. a kind of expansion method using the isolated form variable-frequency transformer as described in any one of claim 1~6, feature
It is, which includes by the primary and secondary side difference parallel connection of more set isolated form variable-frequency transformers or utilizing power distribution dress
It sets after collecting the power on the mechanical rotating shaft of the more wound rotor asynchronous machines to drag a synchronous motor.
10. a kind of expansion method of isolated form variable-frequency transformer according to claim 9, which is characterized in that the dilatation side
The corresponding control method for coordinating of method are as follows: select a set of isolated form variable-frequency transformer as main transformer frequency power transformer, remaining each set
Der Geschwindigkeitkreis-torque is used as from the d axis of variable-frequency transformer, the machine-side converter vector controlled of the main transformer frequency power transformer
Ring-electric current loop three close-loop control, the reference value of der GeschwindigkeitkreisAccording to secondary side ac frequency reference value f*Setting, it may be assumed that
The d axis of the machine-side converter vector controlled from variable-frequency transformer uses torque closed loop-current closed-loop double -loop control,
Torque instruction is allocated according to setting principle, it may be assumed that the general power P that Duo Taocong variable-frequency transformer is shared should meet Pe∑*(m-
1)/m≤P<Pe∑, wherein m is the total tricks of isolated form variable-frequency transformer, Pe∑For the total work for more covering the transmitting of isolated form variable-frequency transformer
Rate.
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