CN106501574B - A kind of Active Power Filter Harmonic Currents detection method - Google Patents
A kind of Active Power Filter Harmonic Currents detection method Download PDFInfo
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Abstract
The invention discloses a kind of new A PF harmonic current detecting methods, to the voltage of points of common connection in collected three-phase power grid voltage unbalanced system, pass through the relationship between current on line side after introducing conductance factor representation voltage on line side and compensating, fundamental positive sequence voltage effective value is acquired according to Active Power Filter-APF power conservation principle, pass through the construction Lagrangian between grid current harmonic content and network voltage simultaneously, target grid electric current is obtained by the method for seeking extreme value, and made the difference with load current and negate can just obtain compensation current instruction value, to realize the power control to Active Power Filter-APF, and then control signal is generated by PWM technology, control the output of Active Power Filter-APF.The present invention replaces the phase voltage in traditional algorithm using the fundamental positive sequence of voltage, so that the variation synchronous with the holding of the fundamental positive sequence of voltage of compensated system power waveform, to overcome the problem of cannot completely eliminating harmonic wave when network voltage distorts.
Description
Technical field
The invention belongs to the control technology fields of power electronic equipment.Specifically, the present invention relates to one kind to be based on power grid
The acquisition methods of the harmonic current of the Active Power Filter-APF of parameter.
Background technique
Mainly there are two sides for application of the Active Power Filter-APF (APF:Active power filter) in power distribution network
Face: system power factor and regulating system voltage are improved.Although the two aspects are all by Active Power Filter-APF to system
For middle injecting reactive current come the purpose difference realized, but compensated, the method realized is also different, but the detection of harmonic current is real
The key factor of existing APF control effect.
Active Power Filter-APF mainly includes major loop and control loop two parts, working principle can be briefly described as
Under: firstly, Harmonic currents detection module carries out analysis detection to harmonic source, require to obtain according to different system balances corresponding
Harmonic wave command signal；Then, current follow-up control circuit passes through current control circuit using harmonic wave command signal as reference signal
The driving signal of main circuit is obtained with modulation module；Finally, under the control of driving signal, benefit needed for main circuit generation system
Repay electric current.The electric current for flowing through power grid includes harmonic source load current and Active Power Filter-APF compensation electric current two parts, two kinds of electricity
After stream superposition, the power network current that harmonic content is extremely low, is similar to sine is just obtained.
Harmonic wave command signal is the foundation that Active Power Filter-APF compensates, the performance of harmonic wave command signal extraction algorithm
Quality is related to the final compensation effect of active power filter system.Ideal harmonic wave command signal extract can in real time with
With the variation that harmonic source loads, the harmonic wave command signal for needing to compensate accurately is detected.
Currently, the anti-therapy of Harmonic currents detection mainly include the following types:
(1) the digital assay method based on FFT
FFT (Fast Fourier Transformation) i.e. fast Fourier decomposition method.By to periodic harmonic wave
Electric current carries out fast Fourier decomposition, harmonic wave command signal needed for obtaining system balance.This method can extract any time
Harmonic signal, and not by mains frequency variation influenced；But this method can only detect periodic harmonic signal, and examine
It needs to carry out a large amount of mathematical computations during surveying, rapidity is poor.Therefore, this method can not be used for harmonic source and frequently change
System.
(2) adaptive Harmonic detection
Adaptation theory is applied to field of signal processing earliest, for extracting original from the signal containing additive noise
Signal.Adaptive harmonic wave command signal extraction algorithm is a kind of closed loop detection method based on adaptive interference cancelling principle, is led to
Overfitting constantly changes the parameter of sef-adapting filter, so that the output valve infinite approach harmonic wave command signal of filter.From
Adapting to detection method has its advantage: not being influenced by system voltage frequency, waveform variation, applied widely, strong robustness.But
Adaptive process is constantly to approach a process for target, convergence rate and system initial state, selection mathematical model and
The optiaml ciriterion of use is related, and therefore, system dynamic responding speed is slow.
(3) based on the detection method of instantaneous reactive power theory
Instantaneous reactive power theory is the most typical with p-q method and ip-iq method, and two methods are obtained by coordinate transform
Instantaneous reality predetermined, fictitious power.When voltage waveform equally exists distortion, the electricity that is calculated using p-q detection algorithm
It flows and contains harmonic component identical with voltage in fundamental wave；And in the current first harmonics being calculated at this time using ip-iq detection method simultaneously
Without these harmonic components.But it needs to carry out multiple changes in coordinates in the use process of this method, calculation amount is larger；Together
When, the introducing of low-pass filter also reduces the rapidity of harmonic detecting.
(4) synchronization detection method
Synchronized harmonics command signal extraction algorithm is analysis with single-phase load currents in harmonic wave command signal extraction process
Object comprehensively considers threephase load harmonic wave and system balance requirement after extracting the harmonic wave command signal in every phase again, thus
Obtain the reference harmonic command signal for meeting system balance requirement.Generally speaking for three-phase system, synchronization detection method is with system
Power-balance is detection target, the decomposition computation of the every phase current of concern that will not be excessive.For three-phase unsymmetrical winding, synchronous inspection
Survey method, not only can be with the idle and positive sequence harmonic point in the load of compensation harmonic source from the angle of three-phase power balance
Amount, moreover it is possible to the asymmetric degree in good improvement system.Traditional synchronized harmonics command signal extraction algorithm is according to three-phase
When balanced dynamometer calculates harmonic current command signal, need using the phase and amplitude information for arriving voltage signal；According to electricity
It presses infomation detection algorithm inappropriate, then can introduce very big detection delay, influence the rapidity and accuracy of harmonic detecting.
(5) (including the harmonic wave based on artificial neural network (Neural Network, NN) instructs for other harmonic detecting methods
Extraction method, FBD harmonic wave instruction extraction method, harmonic wave instruction extraction method based on analog filter etc.).
The theory deduction of aforementioned several common harmonic wave instruction extraction algorithms and verifying be all with three-phase power grid voltage balance and
Premised on undistorted.But in actual application, the continuous superposition accumulation of harmonic signal can cause the distortion of voltage, power grid
Break down or certain specific operations under can equally cause the imbalance of three-phase voltage；At this point, above-mentioned harmonic wave command signal mentions
The accuracy and precision for taking strategy will receive influence.The present invention needs to measure electricity for conventional synchronization harmonic wave instruction extraction algorithm
The drawbacks of pressing signal proposes a kind of improved synchronized harmonics instruction extraction algorithm, avoids conventional synchronization harmonic wave command signal and mention
Algorithm is taken to need the drawbacks of detecting voltage magnitude；Meanwhile appropriate adjustment can be required to control target according to compensation, control mode is cleverer
It is living, there is very strong practicability.
Summary of the invention
Insufficient according to prior art, the present invention provides a kind of Active Power Filter Harmonic Currents detection method, mesh
Be to consider that power grid there are when non-equilibrium state, uses conventional methods Active Power Filter-APF and carry out harmonic current inspection
It surveys, may result in and testing result occur and deviation occur or cannot detect harmonic wave and reactive component, new detection side completely
Method is not only able to achieve network voltage distortion time-harmonic wave current detecting, but also using the balance component in distorted voltage as synchronizing electricity
Pressure, improves the asymmetric degree of three-phase current, improves the compensation effect of Active Power Filter-APF.
The present invention is realized by following technical scheme:
A kind of Active Power Filter Harmonic Currents detection method, method includes the following steps:
Step 1: the three-phase phase current and active electric power of three-phase power grid voltage, load-side at acquisition points of common connection
The DC capacitor voltage of filter；
Step 2: according to the three-phase power grid voltage at collected points of common connection, fundamental wave is obtained using coordinate transformation method
Positive sequence voltage signal, in the three-phase phase current to points of common connection three-phase power grid voltage and load-side, carry out Clark transformation and
Park transformation, and Instantaneous Power Theory is utilized, calculate the average active power p that load is absorbed from grid sideavgAnd active electric power
The average loss p of filter workloss；
Step 3: the processing of virtual value processing module, construction one are sent into collected points of common connection three-phase power grid voltage
A Lagrangian objective function for meeting grid current harmonic aberration rate and the limitation of Voltage Harmonic aberration rate, should by solving
Objective function obtains the apparent energy minimum value of Active Power Filter-APF, to acquire conductance factor Gn, and then acquire target electricity
Net electric current；
Step 4: target grid electric current and threephase load side electric current are made the difference and are negated and can be obtained compensation current-order
Value calculates the reactive power that can be obtained system and need to compensate by instruction current follow-up control circuit；
Step 5: current follow-up control circuit is tracked to compensate current instruction value as reference signal by instruction current
Control circuit and voltage space vector modulation module obtain the driving signal of main circuit；Finally in the control of pwm pulse driving signal
Under system, so that compensation electric current needed for main circuit generation system.
Preferably, the specific implementation of the target grid electric current in step 3 are as follows: the inspection of the target grid electric current
Survey includes two parts: first, using the extracting method based on coordinate transform and Instantaneous Power Theory, meeting three-phase power grid voltage
Demand for control when balance；Second, passing through the net side electricity after voltage on line side and compensation in three-phase power grid voltage unbalanced system
Conductance factor G is introduced between streamn, when according to Active Power Filter-APF steady operation, system power conserva-tion principle, to construct one
Meet the Lagrangian of power conservation and percent harmonic distortion restrictive condition；Again by solving to the function, mesh is obtained
Mark power network current.
Preferably, the voltage of three-phase power grid voltage points of common connection is expressed as:
In formula: χ=a, b, c；H=highest overtone order；ExnThe virtual value of each harmonic voltage；φxnEach harmonic electricity
The initial phase angle of pressure；
Load-side three-phase current indicates are as follows:
In formula: θ is phaselocked loop locking phase angle, Δ θ=θ-ω t, C23=C32 -1, In、The virtual value of each primary current and just
Phase angle, ipFor the active component of current,For ipDC component,
The DC capacitor voltage of Active Power Filter-APF are as follows:
Udc≥3esx (c)。
Preferably, positive sequence voltage is separated, the balance component of voltage is represented by formula at points of common connection:
Wherein: e 'sxnThe n times balance of voltage component extracted in unbalance voltage.
Preferably, in Active Power Filter-APF compensation system, complete Harmonics elimination is that load harmonic is fully compensated,
Obtain the power network current of standard sine with net side fundamental voltage same-phase；Unity power factor compensation is with High Power Factor
For the purpose of, the current on line side with actual electric network voltage in phase, i.e. voltage and current synchronization are obtained, is even deposited when power grid is asymmetric
In distortion, power network current equally contains the harmonic wave of corresponding number at this time；
In order to show the relationship after voltage on line side and compensation between current on line side, conductance factor G is introducedn；
Since the component of voltage and target grid current value that extract are three-phase symmetricals, three-phase is chosen identical
Conductance factor Gn。
Preferably, it can be obtained according to Active Power Filter-APF power conservation principle:
Wherein, pavgLoad average active power is obtained according to instantaneous power principle by threephase load electric current and network voltage
?；ploss-The average loss of Active Power Filter-APF work, for stablizing Active Power Filter-APF DC voltage；E′snN times
The virtual value that component is balanced in harmonic voltage, works as n=1, E 's1Indicate fundamental positive sequence voltage effective value, E 'snCalculating formula be,
Preferably, by introducing electricity percent harmonic distortion limit value, THD is usedio、THDieThe actual electric current surprise of expression system,
Even-order harmonic aberration rate, THDvo、THDveThe odd, even subharmonic aberration rate of the actual voltage of expression system, constructs objective function,
This value is the square value of apparent energy:
Wherein,
Preferably, it when one timing of band load situation, finds out a system and is meeting power conservation and percent harmonic distortion limitation
Under the conditions of minimum Apparent Power, apparent energy is smaller, then power factor is higher；Power minimum asks method to pass through building glug
Bright day function asks conditional extremum to obtain conductance factor Gn,
Formula (i) is brought into formula (e), obtains target grid electric current, making the difference and negating with load current can be compensated
Current instruction value.
Preferably, the THDiomaxAnd THDiemaxSelection, meet following condition:
THD in formulaiostdAnd THDiestdThe respectively grid current harmonic aberration rate of national standard limitation.
The invention has the advantages that:
The drawbacks of present invention needs measurement voltage signal for conventional synchronization harmonic wave instruction extraction algorithm, proposes a kind of improvement
Harmonic wave instruct extraction algorithm, avoid conventional synchronization harmonic wave command signal extraction algorithm and need the drawbacks of detecting voltage magnitude；
It still being able to accurately detect harmonic wave in three-phase power grid voltage imbalance, compensation effect is excellent, meanwhile, it can be required according to compensation suitable
When adjustment controls target, control mode is more flexible, has very strong practicability；It can basis in unbalanced source voltage
Different compensation demand adjustment control targets, realize complete Harmonics elimination or unity power factor compensation.
Conductance factor G is being introduced after voltage on line side and compensation between current on line siden, when being worked according to Active Power Filter-APF
Power conservation principle, to construct the Lagrangian for meeting power conservation and percent harmonic distortion restrictive condition.Pass through again
The function is solved, can obtain target grid electric current, can quickly calculate compensation current instruction value.
Increase the rapidity of Active Power Filter-APF access point voltage-controlled dynamic stability performance and voltage compensation.
Detailed description of the invention
Fig. 1 is ip-iq method harmonic detecting schematic diagram；
Fig. 2 is synchronous reference coordinate system phaselocked loop basic principle flow chart；
Fig. 3 is to extract fundamental positive sequence voltage flow chart using coordinate transform；
Fig. 4 is improved active filter harmonic current detection method schematic diagram；
The harmonic current waveforms that Fig. 5 is detected when being unbalanced source voltage using ip-iq method；
The harmonic current waveforms detected when Fig. 6 is unbalanced source voltage using detection method is improved；
When Fig. 7 selects HF compensation, compensation front and back net side three-phase current comparison of wave shape；
When Fig. 8 selects HF compensation, when using improving detection method detection harmonic wave, current on line side harmonic content value (a) after compensation；
DC voltage waveform (b), net side power factor (c)；
When Fig. 9 selects UPF compensation, A phase network voltage, current waveform (a), net side power factor (b).
Specific embodiment
Below in conjunction with attached drawing, by specific embodiment, the present invention is further illustrated.
Existing common harmonic wave command signal extracts the proposition of strategy and theory deduction, verification process are all based on three-phase
Grid balance symmetrically carries out.When unbalanced source voltage in system, these harmonic wave command signals extract tactful whether can also
Fast and accurate progress harmonic detecting is unknown.The present invention in the widest ip-iq detection method of practical engineering application,
Analyze influence of the unbalanced power supply to harmonic detecting.
As shown in Figure 1, in figure, C32, C respectively indicate Clark transformation matrix and Park transformation matrix.
In formula, ω-electrical network angular frequency.
Assuming that three-phase symmetrical, is detected load current are as follows:
In formula, In、The virtual value and initial phase angle of each primary current.
The distortionless situation of network voltage
When there is no when distortion, three-phase voltage is symmetrical and is represented by following form for grid voltage waveform:
In formula, E1mThe single-phase peak value of network voltage, i.e. power grid fundamental voltage amplitude；
Load current is transformed under synchronous rotating frame:
In formula, ip、iqThe active and reactive component of electric current.
In formula, when n=3k+1, takes symbol, and when n=3k-1 removes symbol, k=0, and 1,2....
ip、iqLow-pass filtered device LPF (Low Pass Filter, LPF) obtains:
In formula,-ip、iqDC component.
It can be obtained by Fig. 2-1 again:
In formula, iaf、ibf、icfRespectively indicate the fundametal compoment in each phase load electric current；C23=C32 -1。
When Active Power Filter-APF is used for compensation harmonic and reactive component simultaneously, i need to be only disconnectedqChannel, at this time:
Exactly equal to fundamental active component.
There is the case where distortion in network voltage
In formula (2-2), the ω t in transformation matrix is and eaCorresponding phase angle can be obtained by phaselocked loop.Work as power grid
When voltage is distorted, the angle that phaselocked loop obtains no longer is stringent ω t, below with synchronous reference coordinate system phaselocked loop
It is subject to analytic explanation for (Synchronous Reference Frame Phase Locked Loop, SRF-PLL).
As shown in Fig. 2, it is first transformed to ɑ-β through Clarke with (2-4) by voltage expression when network voltage balance
Coordinate system:
It is transformed under synchronous rotating frame by park transformation again:
In formula, θ is phaselocked loop locking phase angle, enables network voltage actual phase ω t=θ*, then formula (2-11) further indicates that
Are as follows:
It is found that when locking phase is accurate, i.e. θ*=θ, voltage q axis component is zero.Therefore control component of voltage, makes eq *=0 reaches
When to stable state, PGC demodulation can be realized.
After network voltage is distorted, positive sequence network is contained it is found that removing in voltage waveform by symmetrical components theory analysis
Outside, also contain a large amount of negative phase-sequence and zero-sequence network.For three-phase three-line system, since zero sequence is not turned on path, therefore can
Only consider positive sequence therein and negative sequence network.Voltage signal is obtained by each frequency component linear superposition, therefore in subsequent reason
By in derivation process, process, only considers the positive sequence and negative sequence network in fundamental signal to simplify the analysis.
It is assumed that the network voltage being distorted is indicated with formula (2-13).
In formula, V1、V1Respectively represent the amplitude of the positive and negative sequence voltage of fundamental wave, φ1、φ2Respectively represent the positive and negative sequence voltage of fundamental wave
Initial phase.
After it is accordingly transformed to d-q reference axis by formula (2-10), (2-11), expression is as follows:
If according further to the locking phase principle of SRF-PLL, phase angle that when stable state locks:
As it can be seen that when network voltage contains distortion, the angle that when phaselocked loop stable state obtains no longer is fundamental positive sequence voltage
Phase.
Assuming that deviation between practical locking phase angle and ω t is Δ θ, i.e. Δ θ=θ-ω t, then:
This up-to-date style (2-7) indicates are as follows:
Its contravariant, which is changed under three-phase a-b-c coordinate system, again to obtain:
As it can be seen that ip-iq method is not by power grid distortion effects if only compensation harmonic electric current.
But when needing compensation harmonic simultaneously and reactive current, formula (2-9) becomes:
Fundamental active component in the load current detected is wrong, it is seen that ip-iq method is no longer applicable in such cases
Harmonics and reactive current detection.
Fundamental positive sequence voltage is extracted using coordinate transform, principle is identical as ip-iq harmonic component extraction method, such as Fig. 3
Shown, the nth harmonic voltage under synchronous reference coordinate system may be expressed as:
In formula, edn、eqn- nth harmonic d-axis and quadrature axis component.
edn、eqnAgain and then it may be expressed as:
In formula,The corresponding DC component of-nth harmonic, i.e., the balance component in nth harmonic； - n times
The corresponding AC compounent of harmonic wave, i.e. unbalanced component in nth harmonic.
Therefore, the balance component e' under Static Synchronous referential in nth harmonicsnIt may be expressed as:
Obviously, it when phaselocked loop locking phase angle is positive sequence voltage phase of fundamental wave angle, can be extracted by method shown in Fig. 3
Fundamental positive sequence voltage.But when network voltage is asymmetric or even containing distortion, by SRF-PLL principle analysis it is found that locking phase angle
Degree is no longer the phase information of fundamental positive sequence voltage.Influence of the lower surface analysis locking phase angular deviation to fundamental positive sequence voltage subtraction.
It is assumed that in the case where unbalanced source voltage, between the angle and fundamental positive sequence voltage phase angle of SRF-PLL locking phase
Deviation be Δ θ, the same formula of unbalanced electric grid voltage expression formula (2-10), being transformed to has under rotational coordinates:
Its contravariant is changed under a-b-c coordinate system again, is obtained:
It can be seen that this fundamental positive sequence voltage subtraction method is not influenced by phaselocked loop angular deviation, can apply it to
When unbalanced power supply among the extraction of fundamental positive sequence voltage, this is also one of the advantages of it is relative to other extracting methods.
When unbalanced source voltage, improved harmonic detecting method are as follows:
As shown in figure 4, points of common connection (the Point of Common in three-phase power grid voltage unbalanced system
Coupling, PCC) voltage may be expressed as:
In formula, x=a, b, c；N-overtone order；H-highest overtone order；ExnThe virtual value of-each harmonic voltage；
φxnThe initial phase angle of-each harmonic voltage.
It is separated according to positive sequence voltage, the balance component of voltage may be expressed as: at points of common connection
In formula, e'sxnThe n times balance of voltage component extracted in-unbalance voltage.
In Active Power Filter-APF compensation system, there are two the standards of compensation: complete Harmonics elimination (HF) and specific work
Rate factor compensation (UPF).The purpose of the former compensation is that load harmonic is fully compensated, and is obtained and net side fundamental voltage same-phase
, the power network current of standard sine；The latter is to obtain the net side with actual electric network voltage in phase for the purpose of High Power Factor
Electric current, i.e. voltage and current synchronization, when power grid is asymmetric even there is distortion, power network current equally contains corresponding number at this time
Harmonic wave.
In order to show the relationship after voltage on line side and compensation between current on line side, conductance factor G is introducedn。
Since the component of voltage and target grid current value that extract are three-phase symmetricals, three-phase is chosen identical
Conductance factor Gn。
By Active Power Filter-APF working principle it is found that when Active Power Filter-APF steady operation has not consumed theoretically
Function power, it can be obtained according to power conservation principle:
In formula, pavg- load average active power, can be according to instantaneous power principle by threephase load electric current and network voltage
It obtains；plossThe average loss of-APF work, for stablizing APF DC voltage；E′snComponent is balanced in-nth harmonic voltage
Virtual value, work as n=1, E 's1Indicate fundamental positive sequence voltage effective value.
E′snCalculating can refer to following formula and obtain:
All electricity percent harmonic distortion can be limited within limits in engineering.Assuming that the odd, even subharmonic that engineering limits
The current distortion rate upper limit is respectively THDiomax、THDiemax.The actual odd, even subharmonic aberration rate THD of systemio、THDieAre as follows:
Should then it meet:
Under normal circumstances, THDiomaxAnd THDiemaxSelection, meet following condition:
THD in formulaiostdAnd THDiestdThe respectively grid current harmonic aberration rate of national standard limitation, THDvoAnd THDveFor reality
The voltage harmonic aberration rate on border.
Introduce THDiomaxAnd THDiemaxRather than it is directly defined as zero, it is to meet certain pairs of power factor commands
Stringent occasion.If grid voltage waveform is containing distortion at this time, in addition to there are also other higher hamonic waves for fundamental wave, then net side is electric
Stream needs the higher hamonic wave containing corresponding content also to meet unity power factor.The purpose done so is exactly to contain in the harmonic wave of permission
Measure increase power factor as far as possible in range.
The limiting value of grid current harmonic content within the allowable range are as follows:
That is:
An objective function can be constructed, this value is the square value of apparent energy:
When band carries the timing of situation one, a system is found out in the case where meeting power conservation and percent harmonic distortion restrictive condition most
Small apparent energy, apparent energy is smaller, then power factor is higher.Power minimum asks method can be by constructing Lagrangian
Conditional extremum is asked to obtain.Formula (2-46), (2-53) are respectively constraint equation:
In formula, γ1、γ2、γ3- Lagrangian.
Above-mentioned equation is to G1、Go、GeIt seeks single order local derviation and can be obtained with conditional equation simultaneous:
G3=G5=...=Go (2-57)
G2=G4=...=Ge (2-58)
Bringing formula (2-57) (2-58) into (2-56) can obtain:
In formula
Solution (2-59)~(2-61) has:
Formula (2-45) is brought into you can get it target grid electric current, compensation electric current can just be obtained by making the difference and negating with load current
Instruction value.
Embodiment:
Using Matlab software, the present invention is emulated.System emulation parameter setting is as follows: the uncontrollable rectification of three-phase
8 Europe resistance of bridge band is as harmonic source；DC side busbar voltage value is set as 180V；DC side bus capacitor is 2200uF；Load-side
Smoothing reactor 0.45mH；Active Power Filter-APF exchanges side filter inductance 1.5mH；Switching frequency is set as 12.5kHz；Active electricity
Force filter system is put into 0.06s.
The harmonic wave for improving detection method and detecting is given when Fig. 5 gives unbalanced source voltage using ip-iq method and Fig. 6
Current waveform obviously can be seen that the harmonic current waveforms for using improved method to detect more comprehensively from figure；Fig. 7 gives choosing
When selecting HF compensation, compensation front and back net side three-phase current comparison of wave shape reaches in the time less than a cycle after system is put into
Stablize, and compensated power network current is the power frequency sinusoidal current of three-phase symmetrical, waveform is undistorted；Fig. 8 gives selection HF and mends
When repaying, when using improving detection method detection harmonic wave, current on line side harmonic content value, DC voltage waveform, net side function after compensation
Rate factor meets power grid it can be seen from the figure that grid current harmonic aberration rate is reduced to 3.77% by 30.78% before compensating
It is required that DC side voltage regulation result is good, ripple voltage very little.DC side busbar voltage stable requirement when meeting APF work, choosing
When selecting HF compensation, the power factor of net side substantially meets the standard that power factor is 1 between 97% to 1；Fig. 9 gives choosing
Select UPF compensation when, A phase network voltage, current waveform, net side power factor waveform, it can be seen from the figure that compensation front and back wave
Shape phase is almost the same, and power factor is maintained between 0.99 to 1.
Effect has reached following target: using the balance component in distorted voltage as synchronizing voltage, improving three-phase current
Asymmetric degree, while can be needed to select complete Harmonics elimination (HF) or unity power factor control (UPF) according to compensation.
Claims (9)
1. a kind of Active Power Filter Harmonic Currents detection method, it is characterised in that: method includes the following steps:
Step 1: the three-phase phase current and active power filtering of three-phase power grid voltage, load-side at acquisition points of common connection
The DC capacitor voltage of device；
Step 2: according to the three-phase power grid voltage at collected points of common connection, fundamental positive sequence is obtained using coordinate transformation method
Voltage signal carries out Clark transformation and Park becomes in the three-phase phase current to points of common connection three-phase power grid voltage and load-side
It changes, and utilizes Instantaneous Power Theory, calculate the average active power p that load is absorbed from grid sideavgAnd Active Power Filter-APF
The average loss p of workloss；
Wherein, using coordinate transformation method acquisition fundamental positive sequence voltage signal, the specific method is as follows:
Nth harmonic voltage under synchronous reference coordinate system may be expressed as:
In formula, edn、eqn- nth harmonic d-axis and quadrature axis component；
edn、eqnAgain and then it may be expressed as:
In formula,The corresponding DC component of-nth harmonic, i.e., the balance component in nth harmonic； - nth harmonic
Corresponding AC compounent, i.e. unbalanced component in nth harmonic；
Therefore, the balance component e ' under Static Synchronous referential in nth harmonicsnIt may be expressed as:
Step 3: the processing of virtual value processing module is sent into collected points of common connection three-phase power grid voltage, constructs one completely
The Lagrangian objective function of sufficient grid current harmonic aberration rate and the limitation of Voltage Harmonic aberration rate, by solving the target
Function obtains the apparent energy minimum value of Active Power Filter-APF, to acquire conductance factor Gn, and then acquire target grid electricity
Stream；
Step 4: target grid electric current and threephase load side electric current are made the difference and are negated and can be obtained compensation current instruction value,
The reactive power that can be obtained system and need to compensate is calculated by instruction current follow-up control circuit；
Step 5: current follow-up control circuit passes through instruction current tracing control to compensate current instruction value as reference signal
Circuit and voltage space vector modulation module obtain the driving signal of main circuit；Finally under the control of pwm pulse driving signal,
So that compensation electric current needed for main circuit generation system.
2. a kind of Active Power Filter Harmonic Currents detection method according to claim 1, which is characterized in that step 3
In target grid electric current specific implementation are as follows: the detection of the target grid electric current include two parts:
First, using the extracting method based on coordinate transform and Instantaneous Power Theory, control when meeting three-phase power grid voltage balance
Demand；
Second, in three-phase power grid voltage unbalanced system, by being introduced between current on line side after voltage on line side and compensation
Conductance factor Gn, when according to Active Power Filter-APF steady operation, system power conserva-tion principle meets power constructing one and keeps
Permanent and percent harmonic distortion restrictive condition Lagrangian；Again by solving to the function, target grid electric current is obtained.
3. a kind of Active Power Filter Harmonic Currents detection method according to claim 1, it is characterised in that:
The voltage of three-phase power grid voltage points of common connection is expressed as:
In formula: χ=a, b, c；H=highest overtone order；ExnThe virtual value of-each harmonic voltage；φxn- each harmonic voltage
Initial phase angle；
Load-side three-phase current indicates are as follows:
In formula: θ is phaselocked loop locking phase angle, Δ θ=θ-ω t, C23=C32 -1, In、For the virtual value and first phase of each primary current
Angle, ipFor the active component of current,For ipDC component,
The DC capacitor voltage of Active Power Filter-APF are as follows:
Udc≥3esx (c)。
4. a kind of Active Power Filter Harmonic Currents detection method according to claim 3, it is characterised in that:
Positive sequence voltage is separated, the balance component of voltage is represented by formula at points of common connection:
Wherein: e 'sxnThe n times balance of voltage component extracted in-unbalance voltage.
5. a kind of Active Power Filter Harmonic Currents detection method according to claim 4, it is characterised in that: active
In electric-power filter compensation system, complete Harmonics elimination is that load harmonic is fully compensated, and is obtained and the same phase of net side fundamental voltage
Position, standard sine power network current；Unity power factor compensation is obtained and actual electric network electricity for the purpose of High Power Factor
The current on line side of same-phase, i.e. voltage and current synchronization are pressed, when power grid is asymmetric even there is distortion, power network current is same at this time
Sample contains the harmonic wave of corresponding number；
In order to show the relationship after voltage on line side and compensation between current on line side, conductance factor G is introducedn；
HF is complete Harmonics elimination, and UPF is unit power factor compensation, due to component of voltage and the target grid electricity extracted
Flow valuve is three-phase symmetrical, therefore three-phase chooses identical conductance factor Gn。
6. a kind of Active Power Filter Harmonic Currents detection method according to claim 5, which is characterized in that according to having
Active power filter power conservation principle can obtain:
Wherein, pavg- load average active power is obtained according to instantaneous power principle by threephase load electric current and network voltage；
plossThe average loss of-Active Power Filter-APF work, for stablizing Active Power Filter-APF DC voltage；E′sn- n times
The virtual value that component is balanced in harmonic voltage, works as n=1, E 's1Indicate fundamental positive sequence voltage effective value, E 'snCalculating formula be,
In formula, edn、eqn- nth harmonic d-axis and quadrature axis component,The corresponding DC component of-nth harmonic, i.e. n times are humorous
Balance component in wave.
7. a kind of Active Power Filter Harmonic Currents detection method according to claim 6, it is characterised in that: by drawing
Enter electricity percent harmonic distortion limit value, uses THDio、THDieThe odd, even subharmonic aberration rate of the actual electric current of expression system, THDvo、
THDveThe odd, even subharmonic aberration rate of the actual voltage of expression system, constructs objective function, this value is square of apparent energy
Value:
Wherein,
8. a kind of Active Power Filter Harmonic Currents detection method according to claim 7, it is characterised in that: when band carries
One timing of situation, finds out minimum Apparent Power of the system in the case where meeting power conservation and percent harmonic distortion restrictive condition, depending on
Smaller in power, then power factor is higher；Power minimum asks method to ask conditional extremum to obtain by constructing Lagrangian
Conductance factor Gn,
Wherein, THDiomax、THDiemaxFor the odd, even subharmonic current aberration rate upper limit, formula (i) is brought into formula (e), obtains target
Power network current, compensation current instruction value can be obtained by making the difference and negating with load current.
9. a kind of Active Power Filter Harmonic Currents detection method according to claim 8, it is characterised in that: described
THDiomaxAnd THDiemaxSelection, meet following condition:
THD in formulaiostdAnd THDiestdThe respectively grid current harmonic aberration rate of national standard limitation.
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