CN104601083B - Asynchronous machine negative phase-sequence suppressor and implementation method under the conditions of a kind of Voltage unbalance - Google Patents
Asynchronous machine negative phase-sequence suppressor and implementation method under the conditions of a kind of Voltage unbalance Download PDFInfo
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Abstract
The present invention relates to the asynchronous machine negative phase-sequence suppressor and implementation method under the conditions of a kind of Voltage unbalance, the three-phase of the positive-negative sequence measure voltage & of negative phase-sequence suppressor is respectively corresponded to be connected with the three of asynchronous machine generator terminal；Negative phase-sequence inhibits the input side of waveform generation module to access power grid by pressure regulator；The power supply module of negative phase-sequence suppressor is connect with power grid.Technical solution provided by the invention passes through set end voltage positive and negative sequence component when collecting motor operation in real time and degree of unbalancedness；It is handled by Microcomputer Calculation, issues corresponding control instruction to negative phase-sequence suppressor, generate for inhibiting the voltage waveform of asynchronous machine negative sequence component, to reduce negative sequence component to the adverse effect of asynchronous machine.In addition, if detecting that set end voltage degree of unbalancedness and the single-phase maximum current of stator beyond safety margins range of operation, then issue alarm signal, cut off asynchronous machine power supply, it is ensured that asynchronous machine safe operation.
Description
Technical field
The present invention relates to a kind of negative phase-sequence suppressor and its implementation, under the conditions of in particular to a kind of Voltage unbalance
Asynchronous machine negative phase-sequence suppressor and implementation method.
Background technique
Caused by unbalanced source voltage is mainly unevenly distributed by single-phase load three-phase in power grid, deposited in power supply system at this time
In certain negative sequence component, and negative phase-sequence is very harmful to electric system, threatens the safety and economical operation of electric system.Negative phase-sequence electricity
Stream can all bring biggish harm to the operation of power generation, transmission of electricity, power transformation, distribution and electrical equipment, be mainly reflected in:
1) increase synchronous generator added losses and rotor heating, and cause extraneous vibration；
2) make the relay protection malfunction in electric system with negative sequence component starting, when negative-sequence current effect
Between it is longer when, conventional distance protection will be transferred to blocking, exit the quick acting section of distance protection in a period of time
Operation；
3) negative-sequence current causes three-phase current unbalance, to make have a phase current maximum in power transformer three-phase current
And the nominal output of transformer is limited, its effective rate of utilization is reduced, is increased and local mistake in addition, also causing stray transformer flux
Heat；
4) when Voltage unbalance, it is too high or too low necessarily to will appear certain phase voltage, therefore can lead to single-phase electric devices mistake
Voltage or under-voltage operation, if three phase electric equipment, such as most typical threephase asynchronous, it may appear that fan-out capability drop
The adverse effects such as low, loss increases, fever is serious and vibrates, cause waste of energy, also influence the safety fortune of electrical equipment
Row, or even cause industry park plan interruption and heavy economic losses.
As the motor of the various device drives devices such as blower, pump, compressor, lathe, transmission belt, it is widely used in smelting
Multiple industries such as gold, petrochemical industry, chemical industry, coal, building materials, public utility and field are the maximum current consuming apparatus of electricity consumption.According to system
Meter, in China, the consumed electric energy of motor accounts for 60% or more of whole society's total electricity consumption.And asynchronous motor is low due to its price
The characteristics of honest and clean and superior performance, is used widely in industrial every field.If there are three-phase voltage injustice in network voltage
Weigh phenomenon, will lead to the adverse effect such as energy consumption increase, temperature rise aggravation, service life reduction, can jeopardize motor safety under serious conditions
Operation, influences normally to produce.
Summary of the invention
In view of the deficiencies of the prior art, the object of the present invention is to provide the asynchronous machine under the conditions of a kind of Voltage unbalance is negative
Sequence suppressor and implementation method, technical solution provided by the invention pass through acquisition asynchronous machine winding three-phase voltage, electric current, and fast
Positive and negative sequence voltage and electric current is calculated in speed, calculates voltage unbalance factor.Then power electronic technique is utilized, generation is used for
The voltage waveform that can be cancelled out each other with negative sequence component achievees the purpose that inhibit negative sequence component in power grid, to eliminate voltage not
Adverse effect of the negative sequence component to asynchronous machine when balance.
The purpose of the present invention is adopt the following technical solutions realization:
The present invention also provides the asynchronous machine negative phase-sequence suppressors under the conditions of a kind of Voltage unbalance, it is improved in that
The negative phase-sequence suppressor includes that positive-negative sequence measure voltage & and negative phase-sequence interconnected inhibit waveform generation module；It is described
The three-phase of positive-negative sequence measure voltage & is respectively corresponded to be connected with the three of asynchronous machine generator terminal；The negative phase-sequence inhibits waveform
The outlet side of generation module accesses asynchronous machine power input by parallel；The positive-negative sequence measure voltage & and negative
Sequence inhibits the comparing element connection in waveform generation module；The power supply of the negative phase-sequence suppressor is provided by power grid.
Further, the positive-negative sequence measure voltage & includes the first control module, for controlling asynchronous machine
The closure and opening of power supply switch K；
The positive-negative sequence measure voltage & calculates asynchronous machine generator terminal three using coordinate transform and least square method
The positive-negative sequence component amplitude and phase of phase voltage；
It includes sequentially connected commutation inversion module, comparing element and the second control that the negative phase-sequence, which inhibits waveform generation module,
Module；The commutation inversion module includes rectification link, filtering link and inversion link；In the rectification link, filtering link
Capacitor and inversion link it is in parallel；
The negative phase-sequence inhibits waveform generation module according to the negative sequence voltage amplitude and phase detected, and utilizes commutation inversion
Module generates three-phase negative/positive and inhibits voltage waveform.
Further, the rectification link is made of the cascade submodule of three-phase；Every phase is parallel with Diode series branch
Road；
The filtering link includes reactor and capacitor；The both ends of the reactor respectively with one end of capacitor and inverse
Become one end connection of a phase in link；
The inversion link is made of three-phase diode series arm；The Diode series branch routes concatenated diode
Composition.
Further, the power supply includes: to be obtained using electric network source and super capacitor energy storage device.
Further, the protection act mechanism of the negative phase-sequence suppressor are as follows: when asynchronous machine power supply imbalance of three-phase voltage
When degree is between 0~5%, negative phase-sequence suppressor is worked normally, and produces three for inhibiting negative sequence component in asynchronous machine power supply
Phase voltage waveform；When asynchronous machine power supply non-equilibrium among three phase voltages are greater than 5% and stator maximum monophase current Imax>INWhen, the
One control module then issues warning signal, and cuts off asynchronous machine power supply switch K, I simultaneouslymax=max { IA、IB、IC,
Middle IA、IB、ICRespectively asynchronous machine stator three-phase current virtual value；If Imax≤INWhen, then negative phase-sequence suppressor works normally, after
Continuous monitoring asynchronous machine power supply non-equilibrium among three phase voltages and the single-phase maximum current value of stator.
The present invention also provides a kind of implementation methods of the asynchronous machine negative phase-sequence suppressor under the conditions of Voltage unbalance, improve
Place is that the method includes the following steps:
1. obtaining asynchronous machine positive-negative sequence voltage magnitude and phase, voltage unbalance factor and the single-phase maximum current of stator；
2. negative phase-sequence suppressor produces the three-phase voltage waveform for inhibiting asynchronous machine negative sequence component.
Further, the step 1. in, positive-negative sequence measure voltage & acquires asynchronous machine generator terminal three-phase in real time
Winding voltage amplitude and phase, and using the detection algorithm based on multiple least square acquire winding voltage negative sequence component amplitude and
Phase calculates voltage unbalance factor, obtains the single-phase maximum current of asynchronous machine stator.
Further, in the power system, asynchronous machine generator terminal without the unbalanced threephase voltage of zero-sequence component be expressed as with
Lower discrete form:
In formula, ω indicates power supply angular frequency；Um +、Um -Indicate the amplitude of the positive and negative order components of voltage；Indicate voltage just
The initial phase angle of negative sequence component；Δ T indicates the sampling interval；K indicates sampled instantaneous value；εa(k)、εb(k)、εc(k) it indicates to make an uproar at random
Any combination of sound and higher hamonic wave；Component of the supply voltage under α β coordinate system are as follows:
Complex voltage vector is obtained according to above formula (2):
In formula, first item and Section 2 respectively indicate the positive and negative sequence phasor of supply voltage, and Section 3 indicates random noise and height
Composite phasor of the subharmonic after coordinate transform；
Assuming that supply frequency is it is known that above formula (3) is expressed as:
In formula:
Subscript d and q represent the variable under synchronous rotating frame, the three-phase imbalance voltage transformation that formula (4) are indicated
At matrix form:
U (k)=hTθ+η(k) (6)；
In formula:
Least-squares algorithm, Optional Value function are answered using the recursion with forgetting factor are as follows:
In formula, λ is forgetting factor, λ ∈ (0,1]；Subscript " * " and " T " respectively indicate the conjugation and transposition of complex matrix.It asks
The θ that cost function must be made to minimize, uses the least square method of recursion with forgetting factor shown in formula (9):
Initial parameter is taken as:
In formula, π0For initial error covariance constant, π0>0；I is unit matrix；Positive sequence dq axis component and negative phase-sequence dq axis point
The relationship for measuring the two is as follows:
It prevents evaluated error covariance matrix P (k) from going to zero using evaluated error covariance resetting technique: determining threshold first
Value, when evaluated error covariance matrix P (k) is reset to initial value π0I；When each supply voltage mutates, positive and negative sequence voltage
Current detection module all has initial capability for correcting；
It determines to reset the moment using the method that stagnant ring compares, hysteresis band is determined by the harmonic wave and noise contained in voltage；
The positive-negative sequence detection module is defined using IEC voltage unbalance factor, and calculation formula is as follows:
In formula: UN- negative sequence voltage vector form,
UP- positive sequence voltage vector form,
A-coefficient,
Ua、Ub、Uc- asynchronous machine stator winding three-phase voltage vector form.
Further, the step 2. in, negative phase-sequence inhibit waveform generation module by computer control commutation inversion module,
Negative phase-sequence suppressor is set to produce the three-phase voltage waveform for inhibiting asynchronous machine negative sequence component；Include the following steps:
1) commutation inversion module input side supplies three phase mains through pressure regulator by power grid, adjusts three-phase input electricity according to demand
Pressure value；
2) voltage waveform is inhibited by the three-phase of commutation inversion module output, after voltage magnitude and phase-detection, output suppression
Waveform voltage amplitude U processed–And phase
3) by comparing element to U–、With Um–、It is compared, and exports negative sequence voltage amplitude error euAnd phase is missed
Difference
4) by negative sequence voltage amplitude error euAnd phase errorBe delivered to the second control module, the second control module according to
Error amount issue control command, adjust commutation inversion module in power electronic devices open and the turn-off time, it is then again defeated
Revised three-phase voltage negative phase-sequence inhibits waveform out, so as to circulate back and forth enabling generated negative phase-sequence that waveform to be inhibited to offset different
The negative sequence component in motor stator winding is walked, the added losses being induced by it is reduced, is safely operated asynchronous machine.
Compared with the immediate prior art, the excellent effect that technical solution provided by the invention has is:
1, the asynchronous machine negative phase-sequence suppressor and implementation method under the conditions of Voltage unbalance provided by the invention, mainly passes through
Asynchronous machine winding three-phase voltage, electric current are acquired, and positive and negative sequence voltage and electric current is quickly calculated, calculates voltage injustice
Weighing apparatus degree.Then power electronic technique is utilized, voltage amplitude, phase are automatically adjusted, is produced for offsetting asynchronous machine electricity
The three-phase voltage waveform of negative sequence component in source achievees the purpose that inhibit negative sequence component in power grid, to eliminate Voltage unbalance
When negative sequence component to the adverse effect of asynchronous machine, reach reduction energy consumption of electrical machinery, extend motor service life, maintenance motor safety
The purpose of operation has important practical usage to China's propulsion energy-saving emission reduction plan.
2, the negative phase-sequence suppressor can real-time accurate measurements negative sequence voltage amplitude, phase into asynchronous electric electromechanical source online
Position, and voltage unbalance factor is calculated, obtain stator maximum single-phase electricity flow valuve.
3, the negative phase-sequence suppressor is reduced to a certain extent using supercapacitor group as backup power source to power grid electric energy matter
The influence of amount.
4, in addition, being met to the limit value requirement of voltage unbalance factor in present invention combination motor trade national standard
Protection demand within the scope of this, so that asynchronous machine highly effective and safe under the conditions of Voltage unbalance is run.
Detailed description of the invention
Fig. 1 be negative phase-sequence suppressor provided by the invention and its with asynchronous machine attachment structure schematic diagram；
Fig. 2 is that negative phase-sequence provided by the invention inhibits waveform generation process schematic diagram；
Fig. 3 is negative phase-sequence suppressor movement mechanism schematic diagram provided by the invention；
Three-phase imbalance voltage, current waveform figure when Fig. 4 is not using negative phase-sequence suppressor of the present invention, wherein (a) is three
Phase unbalance voltage waveform diagram；Wherein (b) is three phase unbalance current waveform diagram；
Fig. 5 is using three-phase voltage, the current waveform figure after negative phase-sequence suppressor in the present invention；Wherein (a) is using this hair
Three-phase imbalance voltage oscillogram after bright middle negative phase-sequence suppressor；Wherein (b) is using three after negative phase-sequence suppressor in the present invention
Phase out-of-balance current waveform diagram.
Specific embodiment
Specific embodiments of the present invention will be described in further detail with reference to the accompanying drawing.
The present invention passes through set end voltage positive and negative sequence component when collecting motor operation in real time and degree of unbalancedness；By micro-
Machine calculation processing issues corresponding control instruction to negative phase-sequence suppressor, generates the voltage wave for inhibiting asynchronous machine negative sequence component
Shape, to reduce negative sequence component to the adverse effect of asynchronous machine.In addition, if detecting set end voltage degree of unbalancedness and stator
Single-phase maximum current exceeds safety margins range of operation, then issues alarm signal, cuts off asynchronous machine power supply, it is ensured that motor safety
Operation.
There is negative phase-sequence suppressor provided by the invention positive-negative sequence measure voltage & and negative phase-sequence waveform to be inhibited to generate mould
Block, wherein positive-negative sequence voltage and current module mainly calculates asynchronous machine generator terminal three-phase using coordinate transform and least-squares algorithm
The positive-negative sequence component amplitude and phase of voltage, and negative phase-sequence inhibit waveform generation module then according to the negative sequence voltage amplitude that detects with
Phase, and produce three-phase negative/positive using rectification, filtering and inversion link and inhibit voltage waveform.Negative phase-sequence suppressor and asynchronous machine
Connection structure diagram is as shown in Figure 1.The three-phase of positive-negative sequence measure voltage & respectively corresponds the three-phase with asynchronous machine generator terminal
Connection；The negative phase-sequence inhibits the input side of waveform generation module to access power grid by pressure regulator；The positive-negative sequence voltage and current inspection
It surveys module and inhibits the comparing element in waveform generation module to connect with negative phase-sequence；The power supply of the negative phase-sequence suppressor is mentioned by power grid
For.
The positive-negative sequence measure voltage & includes the first control module, is opened for controlling asynchronous machine power supply
Close the closure and opening of K；The negative phase-sequence inhibit waveform generation module include sequentially connected commutation inversion module, comparing element and
Second control module；The commutation inversion module includes rectification link, filtering link and inversion link；The rectification link, filter
Capacitor and inversion link in wave link is in parallel；
The rectification link is made of the cascade submodule of three-phase；Every phase is parallel with Diode series branch；The filter
Wave link includes reactor and supercapacitor group；The both ends of the reactor respectively with one end of supercapacitor group and inversion
One end connection of a phase in link；The inversion link is made of three-phase diode series arm；The Diode series branch
It is made of concatenated diode.
The present invention also provides a kind of implementation methods of the asynchronous machine negative phase-sequence suppressor under the conditions of Voltage unbalance, including under
State step:
1. obtaining the positive and negative sequence voltage of asynchronous machine, voltage unbalance factor and the single-phase maximum current of stator；
In negative phase-sequence suppressor and its on the basis of with asynchronous machine connection structure diagram, selection acquires three-phase in asynchronous machine generator terminal
Winding voltage, electric current include amplitude and phase, then utilize a kind of detection algorithm based on multiple least square, which can be with
In the case where containing higher hamonic wave and random noise, quickly and accurately detect the amplitudes of the positive and negative order components of set end voltage with
Phase angle.
In the power system, only consider three-phase three-line system, be that there is no zero-sequence components, it is possible to by zero sequence point
Amount is ignored.The unbalanced threephase voltage of no zero-sequence component can be expressed as following discrete form:
In formula, ω indicates power supply angular frequency；Um +、Um -Indicate the amplitude of the positive and negative order components of voltage；Indicate voltage just
The initial phase angle of negative sequence component；Δ T indicates the sampling interval；K indicates sampled instantaneous value；εa(k)、εb(k)、εc(k) it indicates to make an uproar at random
Any combination of sound and higher hamonic wave.Component of the supply voltage under α β coordinate system are as follows:
It can get a complex voltage vector according to above formula
In formula, first item and Section 2 respectively indicate the positive and negative sequence phasor of supply voltage, and Section 3 indicates random noise and height
Composite phasor of the subharmonic after coordinate transform.
Assuming that supply frequency is it is known that formula (3) is expressed as
In formula
Subscript d and q represent the variable under synchronous rotating frame, the three-phase imbalance voltage transformation that formula (4) are indicated
At matrix form:
U (k)=hTθ+η(k) (6)；
In formula:
If wushu (6) regards observational equation, h asTθ is the complex voltage estimated, is known plural form
Row phasor is parameter phasor to be estimated.In practical applications, it is necessary to obtain complex voltage by observing, and observation information
In often contain higher hamonic wave and noise.So what is observed can only contain noisy complex voltage U (k).In order to be joined
Several estimated values can answer least-squares algorithm, Optional Value function using the recursion with forgetting factor are as follows:
In formula, λ is forgetting factor, λ ∈ (0,1]；Subscript " * " and " T " respectively indicate the conjugation an of complex matrix and turn
It sets.In order to acquire the θ for minimizing cost function, the least square method of recursion with forgetting factor shown in formula (9) is used.
In time-varying system, in order to continuous corrected parameter, it is necessary to prevent evaluated error covariance matrix P (k) from decaying to
Zero, more λ of the renewal process of P (k) as seen from the above equation-1One.As 0 < λ < 1, effectively P (k) can be prevented to go to zero.λ is got over
Small, influence of the legacy data to estimated value is with regard to smaller, so that the ability for tracking time-varying parameter is stronger, but stable state accuracy can be corresponding
It reduces, estimated value is easy by noise jamming error to be increased.λ is bigger, and the confidence level of legacy data is also bigger, detection accuracy with
Raising, there is certain robustness to noise, but dynamic response is slack-off.In practical application, need in dynamic response and steady
Compromise in terms of state precision two and considers.Recursive algorithm is to work, it is necessary to initial parameter value be arranged.Common practice is exactly directly will
Initial parameter is taken as:
In formula, π0For initial error covariance constant, π0>0；I is unit matrix.The estimated value of θ can be acquired by iteration,
Namely amplitude and the initial phase angle of the positive and negative order components of network voltage, but positive sequence dq axis component and negative phase-sequence dq axis component be more often sometimes
With.It can mutually be derived by the relational expression of the two.The relationship of the two is as follows:
After changing recursive algorithm convergence for the first time, estimation parameter is intended to true value, at this moment, evaluated error covariance matrix
Element value in P (k) can become very little.If supply voltage mutates again, correction term will lose original amendment energy
Power to make recursive algorithm convergence slowly, or even dissipates.In order to accelerate the tracking velocity of algorithm, make it have continuous
Evaluated error covariance resetting technique is employed herein in capability for correcting.Basic principle is exactly to prevent evaluated error covariance matrix P
(k) it goes to zero.Specific practice an are as follows: threshold value is determined first, when evaluated error covariance matrix P (k) is reset to initial value π0I.In this way, algorithm all has initial capability for correcting when supply voltage mutates every time.
The present invention determines to reset the moment using the method that stagnant ring compares, and hysteresis band is by the harmonic wave that contains in voltage and makes an uproar
Sound determines.Such as the width of stagnant ring can be selected as fundamental voltage amplitude if it is the 10% of fundametal compoment by the content of interference noise
30%, the frequent recovery of covariance matrix can be prevented in this way.eH、eLThe threshold value with set covariance matrix is respectively resetted, when
Evaluated error is greater than eHWhen, then covariance matrix is reset to initial value, until evaluated error is less than eLWhen, just stop resetting, draw
The purpose for entering stagnant ring is ensuring that the stable operation of filter.This method can be in the premise containing higher hamonic wave and random noise
Under, rapidly and accurately detect the amplitude and phase angle of the positive and negative order components of asynchronous machine generator terminal supply voltage.
Positive-negative sequence detection module of the present invention defines (VUF-Voltage Unbalance using IEC voltage unbalance factor
Factor), calculation formula is as follows:
In formula: UN- negative sequence voltage vector form,
UP- positive sequence voltage vector form,
A-coefficient,
Ua、Ub、Uc- asynchronous machine stator winding three-phase voltage vector form.
2. negative phase-sequence suppressor produces the three-phase voltage waveform for inhibiting asynchronous machine negative sequence component.
Under the Voltage unbalance state known to motor theory, occurs negative sequence field inside asynchronous machine, its rotation side
To with rotor direction of rotation on the contrary, the relative rotation speed of itself and rotor is (2-s) n1, n1For synchronous speed, when due to actual motion
Slip s very little, therefore (2-s) ≈ 2.To suppress or eliminate the influence of the negative sequence component, need that an amplitude is same, rotation
The opposite to that magnetic field in direction offsets therewith, and the effect of negative phase-sequence suppressor is that the three-phase voltage wave for producing the function
Shape, it is as shown in Figure 2 that negative phase-sequence inhibits waveform to generate process.
Negative phase-sequence inhibits waveform generation module working principle as described below:
1) commutation inversion module input side supplies three phase mains through pressure regulator by power grid, can adjust three-phase input according to demand
Voltage value；
2) voltage waveform is inhibited by the three-phase of commutation inversion module output, after voltage magnitude and phase-detection, output suppression
Waveform voltage amplitude U processed–And phase
3) by comparing element to U–、With Um–、It is compared, then exports negative sequence voltage amplitude error euAnd phase
Error
4) by negative sequence voltage amplitude error euAnd phase errorBe delivered to the second control module, the second control module according to
Error amount issue control command, adjust commutation inversion module in power electronic devices open and the turn-off time, it is then again defeated
Revised three-phase voltage negative phase-sequence inhibits waveform out, so as to circulate back and forth enabling generated negative phase-sequence to inhibit waveform as far as possible
The negative sequence component in asynchronous machine stator winding is balanced out, the added losses being induced by it is reduced, transports motor safely and efficiently
Row.
Negative phase-sequence suppressor power supply module proposed by the invention is directly powered by power grid through three-phase regulator, herein mistake
Cheng Zhong, while can will be adjusted for supercapacitor group shown in Fig. 2 progress quick charge when grid power quality is poor
Depressor output voltage is adjusted to zero, switchs to be that negative phase-sequence inhibits waveform generation module to power using supercapacitor group, thus reduce negative
Influence of the power electronic devices to grid power quality in sequence suppressor.It is finally reached i.e. inhibition asynchronous machine set end voltage negative phase-sequence
The purpose of component, while reducing the influence in the negative phase-sequence suppressor course of work to grid power quality to a certain extent.
The present invention is referring in GB 22713-2008 " influence of the unbalance voltage to three-phase cage induction motor performance "
" it is recommended that asynchronous machine run when voltage unbalance factor be no more than 5% ", by negative phase-sequence suppressor response control system to voltage not
The movement upper limit of the degree of balance is set as 5%, and protection act mechanism and range can be applied to the voltage unbalance factor model no more than 5%
It encloses, anticipation can be made to operating status automatically, when beyond the safe operation limit, issue early warning and drive protection act, it is ensured that
Motor safe operation；Specifically: when asynchronous machine power supply non-equilibrium among three phase voltages are between 0~5%, negative phase-sequence suppressor is just
Often work, produces the three-phase voltage waveform for inhibiting negative sequence component in asynchronous machine power supply；When voltage unbalance factor is greater than
5% and stator maximum monophase current Imax>INWhen, the first control module then issues warning signal, and cuts off asynchronous machine confession simultaneously
Electric power switch K, it is ensured that man-machine safety, Imax=max { IA、IB、IC, wherein IA、IB、ICRespectively stator three-phase current is effective
Value, in addition, if Imax≤INWhen, then negative phase-sequence suppressor works normally, and continues monitoring voltage degree of unbalancedness and the single-phase maximum electricity of stator
Flow valuve, the first control module of negative phase-sequence suppressor is so as to circulate back and forth to guarantee that asynchronous machine can be in Voltage unbalance situation
Lower safe operation.It is as shown in Figure 3 that negative phase-sequence suppressor acts mechanism.
Embodiment
For one, laboratory 5.5kW squirrel cage asynchronous motor, negative phase-sequence suppressor proposed by the invention is pressed down
Compliance test result processed, asynchronous machine install additional before and after negative phase-sequence suppressor three-phase voltage, practical measurement of current waveform respectively as Fig. 4 (a) and (b) with
And shown in Fig. 5 (a) and (b).In Fig. 4 (a) non-equilibrium among three phase voltages be 2.14%, (b) in three-phase current unbalance degree be
15.55%；And non-equilibrium among three phase voltages are close to 0% in Fig. 5 (a), (b) in three-phase current unbalance degree be 0.91%, from
In as can be seen that the inhibitory effect of negative phase-sequence suppressor proposed by the invention is more obvious.
Finally it should be noted that: the above embodiments are merely illustrative of the technical scheme of the present invention and are not intended to be limiting thereof, to the greatest extent
Invention is explained in detail referring to above-described embodiment for pipe, and those of ordinary skill in the art still can be to this hair
Bright specific embodiment is modified or replaced equivalently, these without departing from spirit and scope of the invention any modification or
Equivalent replacement, within the scope of the claims of the invention pending application.
Claims (2)
1. the asynchronous machine negative phase-sequence suppressor under the conditions of a kind of Voltage unbalance, which is characterized in that the negative phase-sequence suppressor includes
Positive-negative sequence measure voltage & and negative phase-sequence interconnected inhibit waveform generation module；The positive-negative sequence measure voltage & current
The three-phase of module is respectively corresponded to be connected with the three of asynchronous machine generator terminal；The negative phase-sequence inhibits the outlet side of waveform generation module logical
Cross access asynchronous machine power input in parallel；The positive-negative sequence measure voltage & and negative phase-sequence inhibit waveform generation module
In comparing element connection；The power supply of the negative phase-sequence suppressor uses electric network source and super capacitor energy storage device；
The positive-negative sequence measure voltage & includes the closure and opening for controlling asynchronous machine power supply switch K
First control module；
The positive-negative sequence measure voltage & calculates asynchronous machine generator terminal three-phase electricity using coordinate transform and least square method
The positive-negative sequence component amplitude and phase of pressure；
It includes sequentially connected commutation inversion module, comparing element and the second control mould that the negative phase-sequence, which inhibits waveform generation module,
Block；The commutation inversion module includes rectification link, filtering link and inversion link；In the rectification link, filtering link
Capacitor and inversion link are in parallel；
The negative phase-sequence inhibits waveform generation module according to the negative sequence voltage amplitude and phase detected, and utilizes commutation inversion module
It generates three-phase negative/positive and inhibits voltage waveform；
The rectification link is made of the cascade submodule of three-phase；Every phase is parallel with Diode series branch；
The filtering link includes reactor and capacitor；The both ends of the reactor respectively with one end of capacitor and inversion ring
One end connection of a phase in section；
The inversion link is made of three-phase diode series arm；The Diode series branch routes concatenated diode group
At；
The protection act mechanism of the negative phase-sequence suppressor are as follows: when asynchronous machine power supply non-equilibrium among three phase voltages are between 0~5%
When, negative phase-sequence suppressor works normally, and produces the three-phase voltage waveform for inhibiting negative sequence component in asynchronous machine power supply；When different
It walks motor power non-equilibrium among three phase voltages and is greater than 5% and stator maximum monophase current Imax>INWhen, the first control module is then sent out
Pre-warning signal out, and asynchronous machine power supply switch K, I are cut off simultaneouslymax=max { IA、IB、IC, wherein IA、IB、ICRespectively
For asynchronous machine stator three-phase current virtual value；If Imax≤INWhen, then negative phase-sequence suppressor works normally, and continues to monitor asynchronous electricity
Electromechanical source non-equilibrium among three phase voltages and the single-phase maximum current value of stator.
2. a kind of implementation method of the asynchronous machine negative phase-sequence suppressor under the conditions of Voltage unbalance as described in claim 1,
It is characterized in that, the method includes the following steps:
1. obtaining asynchronous machine positive-negative sequence voltage magnitude and phase, voltage unbalance factor and the single-phase maximum current of stator；
2. negative phase-sequence suppressor produces the three-phase voltage waveform for inhibiting asynchronous machine negative sequence component；
The step 1. in, positive-negative sequence measure voltage & acquire in real time asynchronous machine generator terminal three-phase windings voltage magnitude with
Phase, and the detection algorithm based on multiple least square is utilized to acquire the negative sequence component amplitude and phase of winding voltage, calculate electricity
Degree of unbalancedness is pressed, the single-phase maximum current of asynchronous machine stator is obtained；
In the power system, asynchronous machine generator terminal is expressed as following discrete form without the unbalanced threephase voltage of zero-sequence component:
In formula, ω indicates power supply angular frequency；Um +、Um -Indicate the amplitude of the positive and negative order components of voltage；Indicate voltage positive-negative sequence
The initial phase angle of component；Δ T indicates the sampling interval；K indicates sampled instantaneous value；εa(k)、εb(k)、εc(k) indicate random noise and
Any combination of higher hamonic wave；Component of the supply voltage under α β coordinate system are as follows:
Complex voltage vector is obtained according to above formula (2):
In formula, first item and Section 2 respectively indicate the positive and negative sequence phasor of supply voltage, and Section 3 indicates that random noise and high order are humorous
Composite phasor of the wave after coordinate transform；
Assuming that supply frequency is it is known that above formula (3) is expressed as:
In formula:
Subscript d and q represent the variable under synchronous rotating frame, and the three-phase imbalance voltage transformation that formula (4) are indicated is at square
Formation formula:
U (k)=hTθ+η(k) (6)；
In formula:
Least-squares algorithm, Optional Value function are answered using the recursion with forgetting factor are as follows:
In formula, λ is forgetting factor, λ ∈ (0,1]；Subscript " * " and " T " respectively indicate the conjugation and transposition of complex matrix；Acquiring makes
The θ that cost function minimizes, uses the least square method of recursion with forgetting factor shown in formula (9):
Initial parameter is taken as:
In formula, π0For initial error covariance constant, π0>0；I is unit matrix；Positive sequence dq axis component and negative phase-sequence dq axis component two
The relationship of person is as follows:
Prevent evaluated error covariance matrix P (k) from going to zero using evaluated error covariance resetting technique: threshold value first,
Evaluated error covariance matrix P (k) is reset to initial value π0I；When each supply voltage mutates, the inspection of positive-negative sequence voltage and current
Surveying module all has initial capability for correcting；
It determines to reset the moment using the method that stagnant ring compares, hysteresis band is determined by the harmonic wave and noise contained in voltage；
The positive-negative sequence detection module is defined using IEC voltage unbalance factor, and calculation formula is as follows:
In formula: UN- negative sequence voltage vector form,
UP- positive sequence voltage vector form,
A-coefficient,
Ua、Ub、Uc- asynchronous machine stator winding three-phase voltage vector form；
The step 2. in, negative phase-sequence inhibit waveform generation module by computer control commutation inversion module, make negative phase-sequence suppressor
Produce the three-phase voltage waveform for inhibiting asynchronous machine negative sequence component；Include the following steps:
1) commutation inversion module input side supplies three phase mains through pressure regulator by power grid, adjusts three-phase input voltage according to demand
Value；
2) voltage waveform is inhibited by the three-phase of commutation inversion module output, after voltage magnitude and phase-detection, output inhibits wave
Shape voltage magnitude U–And phase
3) by comparing element to U–、With Um –、It is compared, and exports negative sequence voltage amplitude error euAnd phase error
4) by negative sequence voltage amplitude error euAnd phase errorIt is delivered to the second control module, the second control module is according to error
Value issue control command, adjust commutation inversion module in power electronic devices open and the turn-off time, then again output repair
Three-phase voltage negative phase-sequence after just inhibits waveform, so as to circulate back and forth enabling generated negative phase-sequence that waveform to be inhibited to offset asynchronous electricity
Negative sequence component in machine stator winding reduces the added losses being induced by it, is safely operated asynchronous machine.
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| CN108631341B (en) * | 2018-05-17 | 2021-12-21 | 福建奥通迈胜电力科技有限公司 | Zero-sequence current-based three-phase unbalance evaluation method for distribution transformer low-voltage side current |
| CN109245663B (en) * | 2018-09-06 | 2021-03-30 | 西南交通大学 | Multi-dimensional voltage-sharing space vector modulation method suitable for single-phase cascade converter |
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