CN110350534A - A kind of active power filter system and its compensation method based on seven level converters - Google Patents
A kind of active power filter system and its compensation method based on seven level converters Download PDFInfo
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- CN110350534A CN110350534A CN201910644045.5A CN201910644045A CN110350534A CN 110350534 A CN110350534 A CN 110350534A CN 201910644045 A CN201910644045 A CN 201910644045A CN 110350534 A CN110350534 A CN 110350534A
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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
- H02J3/01—Arrangements for reducing harmonics or ripples
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
- H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/20—Active power filtering [APF]
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- Power Engineering (AREA)
- Inverter Devices (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
A kind of active power filter system and its compensation method based on seven level converters, belongs to utility power quality control field；More level active power filtering systems in the prior art are solved using switching tube quantity is excessive, filter construction is huge, the high problem of harmonic content；Seven level converters of the invention include the identical A phase inverter of structure, B phase inverter and C phase inverter, and A phase inverter includes second bridge arm of three DC capacitors, the first bridge arm that four power switch tubes are constituted and four additional power switch tube composition；The present invention has many advantages, such as that switching loss is small, voltage stress is small, electromagnetic interference is low, power system capacity is big, and exports voltage with multiple levels waveform and harmonic content is small, to reduce the volume of filtering device.
Description
Technical field
The present invention relates to utility power quality control fields, filter more particularly to a kind of active electric power based on seven level converters
Wave system system and its compensation method.
Background technique
It is rapidly improved with China's scientific and technological level, in daily life, the figure for the harmonic load that grows on trees.And it is electric
Harmonic wave in net be all by power electronic equipment inside nonlinear device (diode, power switch tube, transformer) generate,
The presence of harmonic wave will increase the additional loss of electrical equipment, and the harmonic current for passing through high frequency in reactant devices can generate sharp make an uproar
Sound can also make the silicon steel sheet of reactor or ferrite be saturated and seriously generate heat in advance；Contain a large amount of harmonic wave electricity in transmission line of electricity
Stream can reduce the power transmission efficiency of electric system, also result in route overheat (route may be made on fire when serious), accelerate route
Aging.
Compared with traditional two level active power filters, more level active power filters have switching loss it is small,
The advantages that voltage stress is small, electromagnetic interference is low, power system capacity is big, and export voltage with multiple levels waveform and harmonic content is small, from
And reduce the volume of filtering device.
But existing more level have chance with power filter structure complexity, it is more using switching tube quantity, make filter device
Bulky, level extended capability is limited, and harmonic content is more.
Summary of the invention
In view of the foregoing deficiencies of prior art, the purpose of the present invention is to provide a kind of based on seven level converters
Active power filter system and its compensation method, with switching loss is small, voltage stress is small, electromagnetic interference is low, power system capacity is big
The advantages that, and export voltage with multiple levels waveform and harmonic content is small, to reduce the volume of filtering device.
In order to achieve the above objects and other related objects, the present invention provides a kind of active electric power based on seven level converters
Filtering system, including sampling unit, control unit, driving unit and power cell, the input terminal of sampling unit are separately connected three
Phase AC network and power cell, the output end of sampling unit connect control unit, and control unit passes through driving unit and power
Unit establishes connection, and the thermal compensation signal of power cell, which is sent into three-phase nonlinear load, carries out harmonic compensation；
The power cell includes seven level converters, specifically includes the identical A phase inverter of structure, B phase inverter and C
Phase inverter, A phase inverter include DC capacitor C1, DC capacitor C2, DC capacitor C3, by power switch tube Sa1, power switch
Pipe Sa2, power switch tube Sa3With power switch tube Sa4Constitute the first bridge arm and by power switch tube Sb1, power switch tube Sb2、
Power switch tube Sb3With power switch tube Sb4The second bridge arm constituted；
The power switch tube Sa1Collector and power switch tube Sa2Collector pass through tie point a1Connection, power
Switching tube Sa2Emitter and power switch tube Sa3Emitter pass through tie point a2Connection, the S of power switch tubea3Collection
The S of electrode and power switch tubea4Collector pass through tie point a3Connection；The power switch tube Sb1Emitter opened with power
Close pipe Sb2Emitter pass through tie point b1Connection, power switch tube Sb2Collector and power switch tube Sb3Pass through tie point b2
Connection, the S of power switch tubeb3Emitter and power switch tube Sb4Connection is established by tie point b3；The DC capacitor C1
Positive terminal and negative pole end be separately connected tie point a1With tie point b1, the C of DC capacitor2Negative pole end and positive terminal connect respectively
Tie point a2With tie point b2；DC capacitor C3Positive terminal and negative pole end be separately connected tie point a3With tie point b3。
Further, the A phase inverter, B phase inverter and C phase inverter are connected with the hub-and-spoke configuration that neutral point suspends
It connects.
Further, the A phase inverter, B phase inverter and C phase inverter pass through filter inductance respectively and access power grid.
Further, DC capacitor C1, DC capacitor C2With DC capacitor C3Capacitance voltage it is equal.
Further, described control unit includes:
Dsp chip: the dsp chip is realized to the processing of sampled data true value and current tracking algorithm；
Fpga chip: realizing and receives the data of dsp chip sending, exports pwm pulse signal by logical operation.
Further, the sampling unit includes power network current sample circuit, line voltage sample circuit, active electric power filter
Wave system system output current sampling circuit and DC capacitor voltage sample circuit.
A kind of active power filtering compensation method based on seven level converters, includes the following steps:
Three phase harmonic current component is obtained by Harmonic currents detection；
Level-one control, three direct currents of the every phase of three-phase inverter are carried out to the global voltage of three DC capacitors in every phase
The sum of the given voltage value of capacitor and three DC capacitor voltage actual values and make poor, obtain adjusting direct current through pi regulator
The command signal of pressure, command signal are multiplied to obtain active current with corresponding phase voltage with the SIN function of phase；
Threephase load electric current obtains three-phase instruction current as difference with overall watt current；
Three-phase instruction current and three-phase inverter output electric current obtain deviation signal after making difference, and offset current signal is sent into
In the composite controller be made of quasi- PR controller and repetitive controller, the offset current signal is respectively fed to quasi- PR controller
In repetitive controller, modulated signal is formed through quasi- PR controller and repetitive controller treated Signal averaging；
Two-stage control is carried out to three DC capacitors in every phase, three DC capacitors of the every phase of three-phase inverter give
It is poor that voltage value is made with three DC capacitor actual voltage values respectively, is superimposed upon on modulating wave after PI is adjusted；
Operation of the modulated signal data through Overmodulation Method, obtains the pwm signal with dead zone.
Further, the transmission function of the quasi- PR controller are as follows:
In formula, KpSubject to PR controller proportionality coefficient, KinResonance coefficient, ωcIt is the cutoff frequency of equivalent low-pass filter
Rate, ωnSubject to PR controller resonance frequency.
Further, the repetitive controller includes: time delay process z-N, auxiliary compensation device Q (z), controlled device transmitting
Function P (z), gain coefficient Kr, the lead compensation link z that phase compensation is carried out to compensator S (z) and controlled device P (z)K、
For the compensator S (z) of controlled device P (z)；
The time delay process z-NPositive feedback internal model is constituted with transmission function Q (z)；Gain coefficient Kr, compensator S (z) and right
Compensator S (z) and controlled device P (z) carries out the lead compensation link z of phase compensationKConstitute compensator.
As described above, the present invention provides a kind of active power filter system based on seven level converters and its compensation side
Method has the following beneficial effects:
1, active power filter system provided by the present application has the advantages that quick, safe and stable, with two traditional level
Active electric filter device is compared, and more level active power filters are with switching loss is small, voltage stress is small, electromagnetic interference
Low, the advantages that power system capacity is big, and export voltage with multiple levels waveform and harmonic content is small, to reduce the body of filtering device
Product.
2, the invention proposes a kind of seven level converter structures is made of 3 DC capacitors and 8 power switch tubes, often
Three DC capacitor voltages of phase bridge arm are equal, open shutdown by 8 power switch tubes of every phase bridge arm, effectively with 16
Switch state can synthesize seven level voltage output waveforms, compared with seven traditional level cascaded H-bridges topological structures, novel seven
Level converter topological structure has less power switch tube quantity and smaller switching loss.
3, the present invention uses the ip-iq electric current testing based on instantaneous reactive power theory, and this method can accurately detect
The size of watt current in power grid and reactive current out, the application and the current follow-up control plan for adding Repetitive controller using quasi- PR
Slightly, the stability that system is improved to constant current can precisely be tracked.
4, the DC capacitor voltage of the application uses grading control mode, firstly, the voltage of three DC capacitors of every phase is given
The sum of the sum of definite value and three DC capacitor voltage actual values carry out make it is poor, by resulting difference after PI is adjusted with corresponding phase
The SIN function of arc in phase makees difference and obtains the Setting signal of watt current, completes the level-one control of capacitance voltage；By three electricity
It is poor that the given voltage value of appearance is made with actual voltage value respectively, is superimposed upon on modulating wave after pi regulator and completes Two-stage control,
The balance control and DC bus-bar voltage balance control of capacitance voltage are realized by voltage grading control.Shorten active electric power filter
The execution cycle of wave apparatus control algolithm improves the response time of system.
5, the control unit of the application uses the control mode of DSP+FPGA, and DSP and the FPGA division of labor are clear, cooperates.
DSP is mainly responsible for the processing of sampled data true value and current follow-up control algorithm is realized, peripheral expansion of the FPGA as dsp chip
Device mainly realizes the parallel data for receiving DSP and issuing, the defeated of pwm pulse signal is realized by the logical operation of FPGA
Out.
Detailed description of the invention
Fig. 1 is the active power filter system entirety functional block diagram based on seven level converters of the embodiment of the present invention；
Fig. 2 is seven level active power filter main circuit schematic diagrams of the embodiment of the present invention；
Fig. 3 is the A phase converter circuit schematic diagram of the embodiment of the present invention；
Fig. 4 is control strategy of embodiment of the present invention schematic diagram, and Fig. 4 a is whole control strategy schematic diagram, Fig. 4 b be electric current with
Track part control strategy schematic diagram；
Fig. 5 is the frequency response of PR controller；
Fig. 6 is the quasi- PR controller frequency response of the embodiment of the present invention；
Fig. 7 is the discrete repeated controlling system block diagram of the embodiment of the present invention；
Fig. 8 is the seven level waveforms figure of phase voltage of the embodiment of the present invention；
Fig. 9 is the A phase capacitance voltage waveform diagram of the embodiment of the present invention；
Figure 10 is A phase power network current simulation waveform before the embodiment of the present invention compensates；
Figure 11 is A phase power network current simulation waveform after compensation of the embodiment of the present invention；
Figure 12 is the DSP power supply circuit of the embodiment of the present invention；
The FPGA power supply circuit of Figure 13 embodiment of the present invention；
The power network current sample circuit of Figure 14 embodiment of the present invention；
The line voltage sample circuit of Figure 15 embodiment of the present invention；
The active electric filter device of Figure 16 embodiment of the present invention exports current sampling circuit；
The DC capacitor voltage sample circuit of Figure 17 embodiment of the present invention；
The driving circuit based on 2SD315AI of Figure 18 embodiment of the present invention；
The main program flow chart of Figure 19 embodiment of the present invention；
The AD of Figure 20 embodiment of the present invention interrupts flow chart；
The compensation three-phase power network current waveform of Figure 21 embodiment of the present invention；
Three phase network current waveform after the compensation of Figure 22 embodiment of the present invention.
Specific embodiment
Illustrate embodiments of the present invention below by way of specific specific example, those skilled in the art can be by this specification
Other advantages and efficacy of the present invention can be easily understood for disclosed content.The present invention can also pass through in addition different specific realities
The mode of applying is embodied or practiced, the various details in this specification can also based on different viewpoints and application, without departing from
Various modifications or alterations are carried out under spirit of the invention.It should be noted that in the absence of conflict, following embodiment and implementation
Feature in example can be combined with each other.
It should be noted that illustrating the basic structure that only the invention is illustrated in a schematic way provided in following embodiment
Think, only shown in diagram then with related component in the present invention rather than component count, shape and size when according to actual implementation
Draw, when actual implementation kenel, quantity and the ratio of each component can arbitrarily change for one kind, and its assembly layout kenel
It is likely more complexity.
As shown in Figure 1, the active power filter system based on seven level converters of the present embodiment, including sampling unit,
The input terminal of control unit, driving unit and power cell, sampling unit is separately connected three-phase AC grid and power cell, adopts
The output end of sample unit connects control unit, and control unit establishes connection by driving unit and power cell, power cell
Thermal compensation signal is sent into three-phase nonlinear load and carries out harmonic compensation；
The power cell includes seven level converters, as shown in Fig. 2, specifically including the identical A phase inverter of structure, B
Phase inverter and C phase inverter, A phase inverter, B phase inverter and C phase inverter are connected with the hub-and-spoke configuration that neutral point suspends；
Specifically as shown in figure 3, A phase inverter includes DC capacitor C1, DC capacitor C2, DC capacitor C3, by power switch
Pipe Sa1, power switch tube Sa2, power switch tube Sa3With power switch tube Sa4Constitute the first bridge arm and by power switch tube Sb1、
Power switch tube Sb2, power switch tube Sb3With power switch tube Sb4The second bridge arm constituted, DC capacitor C1, DC capacitor C2With
DC capacitor C3Capacitance voltage it is equal.
Power switch tube Sa1Collector and power switch tube Sa2Collector pass through tie point a1Connection, power switch
Pipe Sa2Emitter and power switch tube Sa3Emitter pass through tie point a2Connection, the S of power switch tubea3Collector
With the S of power switch tubea4Collector pass through tie point a3Connection；The power switch tube Sb1Emitter and power switch tube
Sb2Emitter pass through tie point b1Connection, power switch tube Sb2Collector and power switch tube Sb3Pass through tie point b2Even
It connects, the S of power switch tubeb3Emitter and power switch tube Sb4Connection is established by tie point b3；The DC capacitor C1's
Positive terminal and negative pole end are separately connected tie point a1With tie point b1, the C of DC capacitor2Negative pole end and positive terminal respectively in succession
Contact a2With tie point b2；DC capacitor C3Positive terminal and negative pole end be separately connected tie point a3With tie point b3, single-phase topology
The DC voltage value of each DC capacitor of knot is Vdc, can be made by the conducting of control switch pipe and shutdown each capacitor output+
Vdc or-Vdc.Every phase inverter shares 16 effective switch states, can synthesize 7 voltage levels, be respectively as follows: 0, ± Vdc,
The harmonic wave of active electric filter device output is effectively reduced as shown in table 1 in ± 2Vdc, ± 3Vdc.
1 seven level converter switch state of table；
Harmonic wave, the A phase inverter, B phase inverter and the C phase change of current are generated by converter power switch motion in order to reduce
Device accesses power grid by filter inductance respectively, and functionally, eliminates the harmonic current in nonlinear load injection capacitor.
The present embodiment described control unit is for realizing capacitance voltage pressure stabilizing, current follow-up control, coordinate transform, controller
Closed-loop control and drive waveforms generate, using dsp chip+fpga chip framework, in the course of work, and wherein DSP digital processing core
Piece selects the TMS320F28335 chip of TI company, and FPGA selects the EP4CE15E22C8N chip of ALTERA company, described
DSP digital processing chip is mainly responsible for the operation of treated sampled signal, instruction current extracts, current follow-up control is calculated
Method presses the realization of algorithm and obtains final three-phase modulations signal, and by modulating wave transmitted in parallel to FPGA, FPGA is main
It is responsible for the modulated signal data received passing through the operation that modulating wave and carrier wave compare, obtains the pwm signal with dead zone, PWM warp
The power switch tube in each phase inverter is driven to work after overdrive circuit amplification.
DSP power supply circuit as shown in figure 12, TPS767D301 export 3.3V, 1.9V as the DSP chip powered；
FPGA power supply circuit as shown in fig. 13 that, 1.2V, 2.5V and 3.3V power supply needed for FPGA pass through AMS1117-
1.2, AMS1117-2.5, AMS1117-3.3 are generated.
The low power control signal amplification of the low level that the driving circuit is used to export FPGA, makes it possible to driving function
Rate switching tube.As shown in figure 18, the model 2SD315AI that the driving circuit of the present embodiment selects Switzerland CONCEPT company to release
Drive module 8 foot MOD of driver and VDD are shorted, work with two kinds of working methods of Direct Model and half-bridge mode
Make in Direct Model, channel A and B are not related at this time, and two channels work independently, and RC1 and RC2 and GND is shorted, at this time shape
State output SO1/SO2 is also to work independently.8 foot MOD of driver and GND are shorted, half-bridge mode is worked in, two interchannels produce
A raw dead time, dead time are adjusted by the RC network between pin 5 and 7, and INB connects high level and enables at this time, and INA is two
Total input terminal of signal.
Sampling unit described in the present embodiment includes power network current sample circuit, line voltage sample circuit, active electric power filter
Wave system system output current sampling circuit and DC capacitor voltage sample circuit.
It is as shown in figure 14 power network current sample circuit, electric current becomes a milliampere rank by mutual inductor, by ratio circuit
Amplification simultaneously compensates phase, in addition being filtered after bias voltage, inputs in DSP.
It is as shown in figure 15 line voltage sample circuit, by two 100K resistance and 1:1 voltage transformer, then passes through ratio
Example circuit conversion be small voltage signal, increase bias voltage after after filter circuit filters, be input to control chip DSP in.
It is as shown in figure 16 active electric power filter to output current sample circuit, power cell output electric current measure is using electricity
Hall sensor is flowed, current Hall sensor output electric current is converted to voltage signal by sampling resistor, adds bias voltage
And it is input in controller after filtering.
It is as shown in figure 17 DC capacitor voltage sample circuit, busbar voltage is reduced voltage by differential amplifier circuit
To within 3V, then by the isolation input DSP of voltage follower.
The present embodiment passes through MATLAB/Simulink Softwares of System Simulation before the design of above-mentioned hardware circuit first
System is emulated, accordingly result is obtained.Fig. 8 is that inverter exports seven level waveforms figure of phase voltage, and Fig. 9 is A phase capacitor electricity
Corrugating figure, Figure 10 are A phase power network current simulation waveform before compensating, and Figure 11 is A phase power network current simulation waveform after compensation.
The active power filtering compensation method based on seven level converters of the present embodiment, such as the whole control strategy principle of Fig. 4
Shown in figure, include the following steps,
1, three phase harmonic current component is obtained by Harmonic currents detection；
The present embodiment is extracted active in load current using the ip-iq electric current testing based on instantaneous reactive power theory
Component obtains the DC component in load current active component by low-pass filter, subtracts DC component by load current and obtain
To harmonic current as giving, compensation electric current is exported as feedback using active electric filter device, this method can accurately be examined
The size for measuring the watt current and reactive current in power grid, it is substantially non-delay when detecting fundamental reactive current, specifically
Include:
I is obtained out by formula (1)p、iq:
Due toAccording to the relationship of the component of e resultant vector and e, obtain:
In formula,Wherein: ω t is the locking phase that phaselocked loop tracking power grid obtains.
The i that will be calculatedp、iq, carry out digital filtering and obtain DC componentChange its contravariant into three-phase electricity again
The fundamental current of stream, shown in transformation for mula such as formula (3):
Threephase load current signal is subtracted into gained fundamental current, three phase harmonic current component can be obtained, and then complete
Detection work to harmonic current, when needing to disconnect i in figure to system harmonics and idle while when detectingqPath,
To iqCarrying out inverse transformation can be obtained System Reactive Power electric current.
2, DC voltage level-one controls:
The sum of the given voltage value of three DC capacitors of the every phase of three-phase inverter and three DC capacitor voltage actual values
And make it is poor, through pi regulator obtain adjusting DC voltage command signal, command signal is with corresponding phase voltage with the sine of phase
Function is multiplied to obtain active current；
3, current tracking:
Threephase load electric current obtains three-phase instruction current signal as difference with overall watt currentWith
Three-phase instruction current signalWithElectric current i is exported with three-phase inverter respectivelyna、inb、incIt is obtained after making difference
Offset current signal is sent into the composite controller being made of quasi- PR controller and repetitive controller by deviation signal Δ i, described
Offset current signal is respectively fed in quasi- PR controller and repetitive controller, and through quasi- PR controller and repetitive controller, treated
Signal averaging forms modulated signal；
Under normal conditions, the general transmission function of PR controller are as follows:
In formula, ωnFor the resonance frequency of PR controller, KpProportionality coefficient, K for PR controllerinFor resonance coefficient, i.e., pair
The gain of resonance frequency.
Fig. 5 is resonance frequency f=50Hz (ωn=100 π rad/s), Proportional coefficient Kp=0.5, resonance coefficient Kin=20
When, the Bode diagram of PR controller frequency response.PR controller can be regarded as PI controller for resonant frequency point in a frequency domain
Translate ω together to the left and to the rightnAngular frequency forms one in ± ωnPlace is all with the controller of resonance point, it is in ± ωn
Possess very big gain, resonance coefficient K at (being ± 50Hz in Fig. 5)inIt is directly proportional with gain of the controller at resonance point, when
KinBigger, controller gain at resonance point is bigger, and in resonant frequency point ± ωnGain reduction is very at frequency in addition
Fastly, so PR controller has very narrow bandwidth, this also causes it can only diagonal frequencies ± ωnSignal have preferable control special
Property.
PR controller is a kind of controller ideally, due to the fluctuation of load, in real power supply system, power grid
Electric voltage frequency also has small-scale fluctuation, and the maximum magnitude that power grid standardizing standard provides that network voltage frequency fluctuation allows exists
Between ± 0.5Hz.The maximum magnitude of so harmonic fluctuations just becomes ± 0.5nHz, and n is overtone order.Frequency fluctuation range is got over
Greatly, because of the bandwidth very little of PR controller, PR controller will become unstable to its gain.Illustrate to deposit in practical applications
In voltage ripple of power network, digital display circuit sampling error and rounding error and truncated error, it is desirable to apply PR in actual condition
In, the integrator under complex frequency domain is substituted with low-pass first order filter, then the transmission function of PR controller becomes formula (5):
New controller formula (5) is referred to as quasi- PR controller, K in formulapSubject to PR controller proportionality coefficient, KinResonance system
Number, ωcIt is the cutoff frequency of equivalent low-pass filter.Due to ωcMuch smaller than ωn, expression formula can simplify are as follows:
Fig. 6 is the frequency response Bode diagram of quasi- PR controller.Wherein resonance frequency f=50Hz, proportionality coefficient Kp=
0.5, resonance coefficient Kin=20, ωcRespectively 3rad/s, 6rad/s, 9rad/s when.
The function of repetitive controller is can be being effectively eliminated in a stable closed loop periodically deviation.This
Kind algorithm is mainly using internal model principle as foundation, i.e., in feedback control system, if in stable closed-loop control system including phase
The dynamic model of same controlled external signal, then the system can be realized as the tracking to input signal floating.Internal model is former
The essence of reason is exactly additional one model for having external signal to control inside model, so that system stability is not by model
Inside input influences, even if controller input signal contains a large amount of interference signals or input signal completely disappears, controller
The stability of control system can be kept by the external signal control module of internal additional.It were it not for internal additional increasing
If external Controlling model, when the margin of error is close to 0, that is, the feedback signal of controller is no better than Setting signal, then,
Controller input signal at this time is equivalent to be 0, that is, without input signal, system may break down.So
Internal model principle is in internal model additional external signal control module very good solution controller stability by input signal
The problem of influence, can make controller become the signal generator for not depending on external variable, the feelings that can be given in no outside
Control signal is issued under condition.
Idle and harmonic current is as Setting signal, the signal comprising multiple frequencies, it is desirable to realize DAZ gene, it is necessary to
Multiple inner membrances are set, i.e., an internal model harmonic signal of each frequency is all arranged, this results in internal model quantity very big, practical
Using difficult to realize.Harmonic signal is identical in the waveform of each power frequency period.Therefore it can choose such internal model such as formula
(7) it is
L in above-mentioned formula is the cycle time of the specified rate of input, carrys out this system input and output as can be seen from the above equation
There is certain time-delay, output has positive feedback effect with input, if the specified rate of input is arbitrary shape, as long as it
With fundamental frequency multiple, circulation, repeatability, which runs past internal mode controller and adds up, and each period can accumulate once,
The signal of output has the delay in several periods, that is to say, that the input signal in the 4th period is 0, then the 7th or 8 period
Output quantity is the accumulation amount in first four period, is similar to multiple integral elements, each point of period demand signal is in each period
It accumulates once, is equivalent to an integral element.
Its discrete form is formula (8), for its discrete form, is equivalent to N number of integrator series connection, wherein N is one
The sampling number in period.
The repetitive controller schematic diagram of the present embodiment is as shown in fig. 7, as seen from the figure, the repetitive controller includes time delay ring
Save z-N, the transmission function P (z) of controlled device, gain coefficient Kr, phase benefit is carried out to compensator S (z) and controlled device P (z)
The lead compensation link z repaidK, be directed to the compensator S (z) of controlled device P (z), R (z) is given input quantity；Y is system output
Amount；Deviation signal of the e between input and output；Rc is to pass through compensated reference signal；D (z) is disturbance quantity；Q (z) is that auxiliary is mended
Device is repaid, in order to stablize system, a constant or low-pass filter less than 1 can be taken.
The time delay process z-NPositive feedback internal model is constituted with transmission function Q (z)；Gain coefficient Kr, compensator S (z) and right
Compensator S (z) and controlled device P (z) carries out the lead compensation link z of phase compensationKConstitute compensator.
Repetitive controller and quasi- PR control are to work at the same time in the present embodiment, and specific structure is as shown in Figure 4 b, two controllers
Input signal it is identical, enter next link after the superposition of respective output signal.The output signal of quasi- PR and Repetitive controller is actually
Be modulating wave a part and capacitor voltage equalizing Signal averaging after formed robust modulation wave, by carrier wave be laminated output PWM.
4, DC capacitor voltage Two-stage control:
The given voltage value of three DC capacitors of the every phase of three-phase inverter respectively with three DC capacitor actual voltage values
It is poor to make, and is superimposed upon on modulating wave after PI is adjusted；
Operation of the modulated signal data through Overmodulation Method, obtains the pwm signal with dead zone.
The main program flow chart of system is as shown in figure 19.This system is controlled using F28335, and main program is mainly completed
The contents such as system initialization and fault detection, interrupt routine include AD sampling, phaselocked loop and DC voltage and compensation electric current
The realization of strategy.In the main program flow chart of the system shown in Figure 19, one is closed when just bringing into operation in system and is hited
The initialization for the system of progress of having no progeny completes the initial setting of each unit used in program.It is opened after the completion of initialization
It interrupts, starts timer, wait to be interrupted.
The flow chart of interruption subroutine is as shown in figure 20.AD interruption is for completing sampling, the inquiry sine table of harmonic current
Software phase-lock loop, coordinate transform, the calculating of number sliding mean filter, the control of DC voltage and the current tracking control of mode
Algorithm operation processed, sends data to FPGA, generates 24 tunnel PWM waves after FPGA realizes unique modulation algorithm.
It is as shown in figure 21 and figure hardware circuit Real output waveform figure of the present invention, Figure 21 is compensation three-phase power grid electricity
Waveform is flowed, Figure 22 is three phase network current waveform after compensation, and as seen from Figure 21, compensation three-phase power network current wave distortion is tight
Weight, compensating control method through this embodiment, output waveform is obvious smooth and occurs without larger burr phenomena, passes through
Spectrum analysis, current distortion rate comply fully with GB standard, illustrate the active power filter system and compensation method of the present embodiment
With good harmonic suppression effect.
The above-described embodiments merely illustrate the principles and effects of the present invention, and is not intended to limit the present invention.It is any ripe
The personage for knowing this technology all without departing from the spirit and scope of the present invention, carries out modifications and changes to above-described embodiment.Cause
This, institute is complete without departing from the spirit and technical ideas disclosed in the present invention by those of ordinary skill in the art such as
At all equivalent modifications or change, should be covered by the claims of the present invention.
Claims (9)
1. a kind of active power filter system based on seven level converters, it is characterised in that: seven level converter includes
The identical A phase inverter of structure, B phase inverter and C phase inverter, A phase inverter include DC capacitor C1, DC capacitor C2, it is straight
Galvanic electricity holds C3, by power switch tube Sa1, power switch tube Sa2, power switch tube Sa3With power switch tube Sa4The first bridge constituted
Arm and by power switch tube Sb1, power switch tube Sb2, power switch tube Sb3With power switch tube Sb4The second bridge arm constituted；
The power switch tube Sa1Collector and power switch tube Sa2Collector pass through tie point a1Connection, power switch
Pipe Sa2Emitter and power switch tube Sa3Emitter pass through tie point a2Connection, the S of power switch tubea3Collector
With the S of power switch tubea4Collector pass through tie point a3Connection；The power switch tube Sb1Emitter and power switch tube
Sb2Emitter pass through tie point b1Connection, power switch tube Sb2Collector and power switch tube Sb3Pass through tie point b2Even
It connects, the S of power switch tubeb3Emitter and power switch tube Sb4Connection is established by tie point b3；The DC capacitor C1's
Positive terminal and negative pole end are separately connected tie point a1With tie point b1, the C of DC capacitor2Negative pole end and positive terminal respectively in succession
Contact a2With tie point b2；DC capacitor C3Positive terminal and negative pole end be separately connected tie point a3With tie point b3。
2. a kind of active power filter system based on seven level converters according to claim 1, it is characterised in that: described
A phase inverter, B phase inverter and C phase inverter are connected with the hub-and-spoke configuration that neutral point suspends.
3. a kind of active power filter system based on seven level converters according to claim 1, it is characterised in that: described
A phase inverter, B phase inverter and C phase inverter pass through filter inductance respectively and access power grid.
4. a kind of active power filter system based on seven level converters according to claim 1, it is characterised in that: direct current
Capacitor C1, DC capacitor C2With DC capacitor C3Capacitance voltage it is equal.
5. a kind of active power filter system based on seven level converters according to claim 1, it is characterised in that: described
A kind of active power filter system based on seven level converters includes control unit, and control unit includes:
Dsp chip: the dsp chip is realized to the processing of sampled data true value and current tracking algorithm；
Fpga chip: realizing and receives the data of dsp chip sending, exports pwm pulse signal by logical operation.
6. a kind of active power filter system based on seven level converters according to claim 1, it is characterised in that: described
A kind of active power filter system based on seven level converters includes sampling unit, and sampling unit includes power network current sampling electricity
Road, line voltage sample circuit, active power filter system output current sampling circuit and DC capacitor voltage sample circuit.
7. a kind of active power filtering compensation method based on seven level converters, characterized by the following steps:
Three phase harmonic current component is obtained by Harmonic currents detection；
Level-one control, three DC capacitors of the every phase of three-phase inverter are carried out to the global voltage of three DC capacitors in every phase
Given voltage value sum and three DC capacitor voltage actual values and make poor, obtain adjusting DC voltage through pi regulator
Command signal, command signal are multiplied to obtain active current with corresponding phase voltage with the SIN function of phase；
Threephase load electric current obtains three-phase instruction current as difference with overall watt current；
Three-phase instruction current and three-phase inverter output electric current obtain deviation signal after making difference, and offset current signal is sent by standard
In the composite controller that PR controller and repetitive controller are constituted, the offset current signal is respectively fed to quasi- PR controller and again
In multiple controller, through quasi- PR controller and repetitive controller, treated that Signal averaging forms modulated signal；
Two-stage control, the given voltage of three DC capacitors of the every phase of three-phase inverter are carried out to three DC capacitors in every phase
It is poor that value is made with three DC capacitor actual voltage values respectively, is superimposed upon on modulating wave after PI is adjusted；
Operation of the modulated signal data through Overmodulation Method, obtains the pwm signal with dead zone.
8. a kind of active power filtering compensation method based on seven level converters according to claim 7, it is characterised in that: described
The transmission function of quasi- PR controller are as follows:
In formula, KpSubject to PR controller proportionality coefficient, KinResonance coefficient, ωcIt is the cutoff frequency of equivalent low-pass filter, ωn
Subject to PR controller resonance frequency.
9. a kind of active power filtering compensation method based on seven level converters according to claim 7, it is characterised in that: described
Repetitive controller includes: time delay process z-N, it is auxiliary compensation device Q (z), the transmission function P (z) of controlled device, gain coefficient Kr, right
Compensator S (z) and controlled device P (z) carries out the lead compensation link z of phase compensationK, be directed to controlled device P (z) compensation
Device S (z)；
The time delay process z-NPositive feedback internal model is constituted with transmission function Q (z)；Gain coefficient Kr, compensator S (z) and to compensation
Device S (z) and controlled device P (z) carries out the lead compensation link z of phase compensationKConstitute compensator.
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