CN105846697B - PWM rectifications control method and system under a kind of low switching frequency - Google Patents
PWM rectifications control method and system under a kind of low switching frequency Download PDFInfo
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- CN105846697B CN105846697B CN201610292325.0A CN201610292325A CN105846697B CN 105846697 B CN105846697 B CN 105846697B CN 201610292325 A CN201610292325 A CN 201610292325A CN 105846697 B CN105846697 B CN 105846697B
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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
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/14—Arrangements for reducing ripples from dc input or output
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Abstract
PWM rectifications control method and system under a kind of low switching frequency, method include：S1, sampling network voltage and DC bus-bar voltage, and based on phaselocked loop phase-lock technique tracking grid phase and mains frequency, according to mains frequency sampling rate adjusting and update PID control period；S2, it is based on the newer PID control period, carrying out vector controlled to PWM rectifier according to network voltage and DC bus-bar voltage obtains the amplitude U of output voltager；S3, it is based on the newer PID control period, the continuous grid phase angle in a PID control period is calculated according to grid phase and mains frequency；S4, according to amplitude Ur, grid phase angle and prestore harmonic wave optimization pulse angle table, obtain the switch angle under 1/4 grid cycle；S5, it is expanded the switch angle under 1/4 grid cycle to obtain the pwm pulse signal of a grid cycle.The characteristics of method that the present invention generates pwm pulse belongs to synchronous modulation, compared to the total harmonic distortion that asynchronous modulation can effectively reduce output current.
Description
Technical field
The present invention relates to PWM rectifications control method under technical field of electric power more particularly to a kind of low switching frequency and it is
System.
Background technology
Existing three level four-quadrants frequency-converter device, using three level neutral-point-clampeds (Neutral Point Clamped),
Back to back structure connects, and Active Front End is connect with power grid by reactor using PWM rectifier.Traditional skill of PWM rectifier
Art mostly uses voltage-type SPWM controls in control mode.
Mathematical model of the SPWM control methods based on system under grid voltage orientation dq rotating coordinate systems, using voltage,
Current double closed-loop structure realizes vector controlled.With reference to figure 1, first, real-time grid phase theta is obtained by PHASE-LOCKED LOOP PLL TECHNIQUES；So
Afterwards, DC bus-bar voltage V is on the one hand sampleddc, by VdcWith target voltage Vdc *After being compared active electricity is obtained through pi regulator
Stream instruction id *, on the other hand sample AFE three-phase input voltages uAFE, according to uAFEAFE three-phase input currents i is calculatedAFE, with
θSOrientation carries out dq and converts to obtain d shaft currents idWith q shaft currents iq；Subsequently by idWith id *It is obtained through pi regulator after being compared
D axis to output voltage instructs ud, equally, by iqWith artificial setting iq *Be compared, obtain output voltage q axis instruction uq；
Finally by udAnd uqWith θSOrientation carries out dq and converts to obtain SPWM control instructions ua、ub、uc。
Obtain ua、ub、ucIt uses common asynchronous PWM modulation strategy again afterwards, realizes the vector controlled of PWM rectifier.Modulation methods
In formula, sampled at starting point and the vertex moment of each triangular carrier, carrier frequency determines the sampling of entire control system
Frequency and controlling cycle.PWM modulation link approximation is usually reduced to first order inertial loop.It is carried using traditional symmetric triangular
Wave modulation method generally remains carrier frequency fcIt immobilizes, as frequency of modulated wave frWhen variation, carrier wave ratio N is variation.It is adjusting
In the half period of wave processed, the pulse number of PWM wave is not fixed, and phase is also not fixed, and the pulse of positive-negative half-cycle is asymmetric, half cycle
The pulse in front and back 1/4 period is also asymmetric in phase.In short, the prior art uses common asynchronous PWM modulation, and sample frequency is solid
It is fixed, there is no synchronized relation with grid phase.
Above-mentioned frequency converter control method is analyzed mainly for the higher situation of PWM switching frequencies, is designed, controlling party
Method is not suitable in high-power field, otherwise will lead to that such as output waveform harmonic distortion is excessive, control system bandwidth drop
The problems such as low, speed adjusting performance declines.PWM modulation link approximation is usually reduced to one by prior art in Control System Design
The premise of rank inertial element is：The switching frequency of PWM modulation is higher, and delay is relatively small, can ignore this delay and be to control
The influence of system.And with the reduction of switching frequency, in the occasion of 500Hz low switching frequencies below, the delay of PWM modulation link
It significantly increases.
When switching frequency is higher, low-order harmonic is practically free of in the output waveform of PWM modulation, and higher hamonic wave is because of its frequency
Relative system bandwidth is higher to be ignored；Using traditional symmetric triangular carrier modulation method, in the starting point of each triangular carrier
It is sampled with the vertex moment, can directly obtain fundamental wave.
When switching frequency is relatively low, because of dead zone, non-linear and the reason of realize precision, relative to height switch frequency in control system
There are more low-order harmonics for rate situation, if directly filtering out harmonic wave using the methods of low-pass filtering, ring is filtered in dynamic process
The delay of section reduces the stability and dynamic property of control system by serious, or even can not restrain, and traditional control method cannot
The disturbance of low-order harmonic is effectively resisted while quickly tracking fundamental wave instruction.
PWM rectifier at present in pressure high-power applications, switching loss increase with modulating frequency and are increased, and device is set
It is larger to count capacity, response modulating frequency reduces, therefore preferably with low switching frequency, and low switching frequency can lead to output voltage
Harmonic wave increase, when serious influence system normal work.Especially in high-power grid-connected converter, output should be met and held
Amount is reduced switching frequency, meets networking harmonic requirement again, cannot be satisfied using above-mentioned prior art.
Invention content
The technical problem to be solved in the present invention is, for the drawbacks described above of the prior art, provides a kind of low switching frequency
Lower PWM rectifications control method and system.
The technical solution adopted by the present invention to solve the technical problems is：Construct PWM rectification controls under a kind of low switching frequency
Method processed is applied to the PWM rectifier of High Power Active, the method includes：
S1, the sample frequency f with settingcSample network voltage uAFEWith DC bus-bar voltage Vdc, and it is based on phaselocked loop locking phase
Method tracks grid phase θsWith mains frequency fs, according to mains frequency fsThe sample frequency f of adjustment setting in real timecEqual to N*fsWith
And the update PID control period, N is positive integer；
S2, it is based on the newer PID control period, according to the network voltage u of real-time sampling in step S1AFEAnd DC bus
Voltage VdcVector controlled is carried out to PWM rectifier and obtains the amplitude U of output voltager；
S3, it is based on the newer PID control period, according to the grid phase θ of real-time tracking in step S1sAnd mains frequency
fsContinuous grid phase angle in the newer PID control period of off-line calculation one；
S4, the amplitude U according to output voltager, grid phase angle and prestore harmonic wave optimization pulse angle table, obtain
Switch angle under 1/4 grid cycle；
S5, it is expanded the switch angle under 1/4 grid cycle to obtain the pwm pulse signal of a grid cycle, root
PWM rectifications control is realized according to the pwm pulse signal；
The step S3 includes：With based on the newest obtained grid phase θ of phaselocked loop phase-lock techniquesFor initial value, with one
A newer PID control period is the time of integration, to mains frequency fsIntegral obtained in the newer PID control period
Continuous grid phase angle：
Under low switching frequency of the present invention in PWM rectifications control method, the PID control period is equal to sampling frequency
Rate fcCorresponding sampling period, the step S4 include：
S41, the current PID control period is divided into M moment, M is respectively obtained according to the continuous grid phase angle
The voltage magnitude of the grid phase at a moment, the M moment is equal to current start time in PID control period corresponding amplitude
Ur；
S42, the voltage magnitude according to the grid phase and M moment at M moment call the harmonic wave to prestore to optimize pulse angle
Table is spent, the switch angle at each moment in M moment is determined after being tabled look-up；
S43, S1 is gone to step to obtain the switch angle at M moment in next PID control period, until obtaining
The switch angle at all moment corresponding to 1/4 grid cycle.
It is electric by 1/4 described in the step S5 under low switching frequency of the present invention in PWM rectifications control method
The pwm pulse signal that switch angle under the net week phase is expanded to obtain a grid cycle includes：It will be under 1/4 grid cycle
Switch angle carries out mirror image and obtains the switch angle in 1/4-1/2 grid cycles, and the switch angle under 1/2 grid cycle is carried out
Mirror image obtains the switch angle in 1/2-1 grid cycles again after reversed.
Under low switching frequency of the present invention in PWM rectifications control method,
If the mains frequency of phaselocked loop output is f in the step S1S, then the sample frequency of setting is adjusted in real time
fcEqual to N*fs, on the basis of locking phase output phase, in k-th of sampling instant, the grid phase θ of the phaselocked loop outputSFor k*
(2 π/N), wherein k=0,1 ..., N-1, N are positive integer.
Under low switching frequency of the present invention in PWM rectifications control method, the step S2 includes：
S21, by DC bus-bar voltage VdcWith target voltage Vdc *After being compared watt current instruction is obtained through pi regulator
id *；
S22, according to network voltage uAFEPower network current i is calculatedAFE, with grid phase θSOrientation carries out dq and converts to obtain
D shaft currents idWith q shaft currents iq；
S23, by d shaft currents idI is instructed with watt currentd *It obtains through pi regulator representing output voltage after being compared
The d axis of active component instructs ud, by q shaft currents iqWith the referenced reactive current i of user settingq *Through pi regulator after being compared
Obtain representing the q axis instruction u of the reactive component of output voltageq；
S24, the amplitude U that output voltage is calculated according to following formular：
The invention also discloses PWM rectification control systems under a kind of low switching frequency, the PWM for being applied to High Power Active is whole
Device is flowed, including：
Phase locking unit, for the sample frequency f of settingcSample network voltage uAFEWith DC bus-bar voltage Vdc, and be based on
Phaselocked loop phase-lock technique tracks grid phase θsWith mains frequency fs；
Sample frequency and PID control period updating unit, for according to mains frequency fsThe sampling of adjustment setting in real time
Frequency fcEqual to N*fsAnd the update PID control period, N is positive integer；
Output voltage amplitude determination unit is based on the newer PID control period, according to the network voltage u of real-time samplingAFE
With DC bus-bar voltage VdcVector controlled is carried out to PWM rectifier and obtains the amplitude U of output voltager；
Grid phase angle determination unit, for being based on the newer PID control period, according to the grid phase of real-time tracking
θsAnd mains frequency fsContinuous grid phase angle in the newer PID control period of off-line calculation one；
Pwm pulse signal generation unit, for according to amplitude Ur, grid phase angle and prestore harmonic wave optimization pulse
Angle table obtains the switch angle under 1/4 grid cycle, is expanded the switch angle under 1/4 grid cycle to obtain one
The pwm pulse signal of grid cycle realizes PWM rectifications control according to the pwm pulse signal；
The grid phase angle determination unit is with based on the newest obtained grid phase θ of phaselocked loop phase-lock techniquesIt is first
Initial value, using a newer PID control period as the time of integration, to mains frequency fsIntegral obtains the newer PID control
Continuous grid phase angle in period processed：
Under low switching frequency of the present invention in PWM rectification control systems, the PID control period is equal to sampling frequency
Rate fcCorresponding sampling period, the pwm pulse signal generation unit include：
First computation subunit, for the current PID control period to be divided into M moment, according to the continuous power grid phase
Parallactic angle degree respectively obtains the grid phase at M moment, and the voltage magnitude at the M moment is equal to the current PID control period and opens
Begin moment corresponding amplitude Ur；
Second computation subunit, according to the voltage magnitude of the grid phase and M moment at M moment, call prestore it is humorous
Wave optimizes pulse angle table, and the switch angle at each moment in M moment is determined after being tabled look-up；
The subelement that third calculates, triggers the switching angle at the M moment that other units obtained in next PID control period
Degree, until obtaining the switch angle at all moment corresponding to 1/4 grid cycle.
It is described by opening under 1/4 grid cycle under low switching frequency of the present invention in PWM rectification control systems
It closes angle and is expanded to obtain the pwm pulse signal of a grid cycle and include：Switch angle under 1/4 grid cycle is carried out
Mirror image obtains the switch angle in 1/4-1/2 grid cycles, by the switch angle under 1/2 grid cycle carry out it is reversed after mirror image again
Obtain the switch angle in 1/2-1 grid cycles.
Implement PWM rectifications control method and system under the low switching frequency of the present invention, has the advantages that：This hair
Bright sample frequency fcIt is according to mains frequency fsAdjustment obtains, and realizes that sampling instant is synchronous with grid phase, meets synchronous modulation
Basic demand；Continuous grid phase angle in one PID control period of off-line calculation optimizes pulse angle using harmonic wave
Table method of calling exports pwm pulse, realizes that off-line calculation obtains the switch angle so that current harmonic content minimum, and entire week
The characteristics of pwm pulse of phase is expanded to obtain, belong to synchronous modulation by the switch angle under 1/4 grid cycle, this modulator approach
Compared to asynchronous PWM modulation, the total harmonic distortion of output current can be effectively reduced；
Further, when calculating grid phase angle, integral is all that phaselocked loop phase-lock technique is newest to be obtained to be based on every time
The grid phase θ arrivedsFor initial value, the limitation of sampling precision can be overcome, continuous grid phase information is obtained, realize simultaneously
Phase bit comparison amendment, keeps the calculating of switch angle more accurate；The sample frequency f of adjustment setting in real timecEqual to N*fs, improve sampling
Precision, while the stability of output PWM voltages can be improved.
Description of the drawings
Present invention will be further explained below with reference to the attached drawings and examples, in attached drawing：
Fig. 1 is the model schematic for generating pwm pulse in the prior art；
Fig. 2 is flow chart of the method for the present invention；
Fig. 3 is that the method for the present invention generates the model schematic of pwm pulse；
Fig. 4 be the present invention method in sampling instant and grid phase relationship；
Fig. 5 is that integral obtains the schematic diagram of continuous grid phase angle in step S3；
Fig. 6 is the schematic diagram that the pwm pulse signal for obtaining a grid cycle is expanded in step S5.
Specific implementation mode
For a clearer understanding of the technical characteristics, objects and effects of the present invention, now control attached drawing is described in detail
The specific implementation mode of the present invention.
As shown in Fig. 2, being flow chart of the method for the present invention.
PWM rectification control methods under the low switching frequency of the present invention are applied to the PWM rectifier of High Power Active, mainly
Including：
S1, the sample frequency f with settingcSample network voltage uAFEWith DC bus-bar voltage Vdc, and it is based on phaselocked loop locking phase
Method tracks grid phase θsWith mains frequency fs, according to mains frequency fsThe sample frequency f of adjustment setting in real timecAnd update
The PID control period；
Wherein, the PID control period is equal to sample frequency fcThe corresponding sampling period；
S2, it is based on the newer PID control period, according to the network voltage u of real-time sampling in step S1AFEAnd DC bus
Voltage VdcVector controlled is carried out to PWM rectifier and obtains the amplitude U of output voltager；
S3, it is based on the newer PID control period, according to the grid phase θ of real-time tracking in step S1sAnd mains frequency
fsContinuous grid phase angle in the newer PID control period of off-line calculation one；
S4, the amplitude U according to output voltager, grid phase angle and prestore harmonic wave optimization pulse angle table, obtain
Switch angle under 1/4 grid cycle；
S5, it is expanded the switch angle under 1/4 grid cycle to obtain the pwm pulse signal of a grid cycle, root
PWM rectifications control is realized according to the pwm pulse signal.
With reference to Fig. 3, above each step is described in detail successively.
About step S1：
Phaselocked loop phase-lock technique is the technology of a comparative maturity, and as shown in Figure 3, the input of phaselocked loop is that sampling obtains
Network voltage uAFE, output is grid phase θsWith mains frequency fs, therefore frequently with phase-lock technique tracking grid phase θs
With mains frequency fs。
The application is in order to realize the effect of synchronous modulation, using adaptive phase-lock technique, if described in the step S1
The mains frequency of phaselocked loop output is fS, then the sample frequency f of setting is adjusted in real timecEqual to N*fs, and with locking phase output phase be
Benchmark, with reference in figure 4, in k-th of sampling instant, the grid phase θ of the phaselocked loop outputSFor k* (2 π/N), wherein k=0,
1 ..., N-1, N are positive integer.
Also it just says that sample frequency is not changeless, but is adjusted in real time according to mains frequency, therefore can be with
See that the time interval between any two sampling instant in Fig. 4 is variation.Due to adjusting the sample frequency of setting in real time
fcEqual to N*fs, sample frequency f of the present inventioncIt is according to mains frequency fsAdjustment obtains, and realizes the same of sampling instant and grid phase
Step improves sampling precision, while can improve the stability of output PWM voltages, meets the basic demand of synchronous modulation.
About step S2：
Continuing with Fig. 3, the step S2 includes：
S21, by DC bus-bar voltage VdcWith target voltage Vdc *After being compared watt current instruction is obtained through pi regulator
id *；
S22, according to network voltage uAFEPower network current i is calculatedAFE, with grid phase θSOrientation carries out dq and converts to obtain
D shaft currents idWith q shaft currents iq；
In fact, net electric current iAFEIt can also directly be directly acquired by current sample, this is not limited.
S23, by d shaft currents idI is instructed with watt currentd *It obtains through pi regulator representing output voltage after being compared
The d axis of active component instructs ud, by q shaft currents iqWith the referenced reactive current i of user settingq *Through pi regulator after being compared
Obtain representing the q axis instruction u of the reactive component of output voltageq；
S24, the amplitude U that output voltage is calculated according to following formular：
About step S3：
With reference to figure 5, the step S3 in step S1 based on the newest obtained grid phase θ of phaselocked loop phase-lock techniquesFor
Initial value, using a newer PID control period as the time of integration, to mains frequency fsIntegral obtains the newer PID
Continuous grid phase angle in controlling cycle：
For example, t in Fig. 50-t1、t1-t2、t2-t3... a sampling period is indicated respectively, namely indicates one respectively
The PID control period.It is only capable of obtaining t by step S10、t1、t2、t3... the mains frequency f of these discrete instantssIf not
It being integrated, then the grid phase sampled will appear the stair-stepping variation in figure, the PID control period (namely one adopted
The sample period) in mains frequency fsIt is unknown, the mains frequency f in a PID control period in order to obtains, present invention use
Continuous grid phase angle in a PID control period is calculated by integrating time-out in offline computing method, can with gram
The limitation for taking sampling precision obtains continuous grid phase information, such as the curved section Y in figure01、Y12、Y23... one is indicated respectively
Continuous grid phase information in a PID control period.
Moreover, the present invention is in each integral, using based on the newest obtained grid phase θ of phaselocked loop phase-lock techniques
For initial value, rather than the numerical value of the above integration period finish time is initial value, is equivalent to and realizes phase bit comparison amendment,
Keep the calculating of switch angle more accurate.That is Y in Fig. 512Initial value be not Y01Finish time numerical value, but according to locking phase
The mains frequency f that ring locking phase obtainss, and so on.
About step S4：
Sample frequency f in previous step S1cEqual to N*fs, therefore, grid cycle is equal to N times of sampling period.Step S4
It is to obtain the pwm pulse information of 1/4 grid cycle, is obtained in complete grid cycle using expansion mode in step S5
Pwm pulse information.In order to obtain the pwm pulse information of 1/4 grid cycle, (sampling is all by a PID control period by the present invention
Phase) thinner division is carried out, it is divided into M moment, then a grid cycle includes N*M moment, corresponding to 1/4 grid cycle
At the time of sum 1/4*N*M be denoted as L, step S4 is the switch angle that determine this L moment.
The step S4 includes：
S41, the current PID control period is divided into M moment, M is respectively obtained according to the continuous grid phase angle
The voltage magnitude of the grid phase at a moment, the M moment is equal to current start time in PID control period corresponding amplitude
Ur；
As it can be seen that the phase at each moment is to be obtained using continuous grid phase angle, and consider a PID control week
The amplitude no-load voltage ratio very little of output voltage in phase, it is believed that the amplitude U in a PID control periodrIt is constant.
S42, the voltage magnitude according to the grid phase and M moment at M moment call the harmonic wave to prestore to optimize pulse angle
Table is spent, the switch angle at each moment in M moment is determined after being tabled look-up；
Wherein, harmonic wave optimization pulse angle table is table known in the art, and which describe most of voltage magnitude, phase institutes
The corresponding switch angle for making harmonic wave minimum.
S43, S1 is gone to step to obtain the switch angle at M moment in next PID control period, until obtaining
The switch angle at all moment (i.e. L moment) corresponding to 1/4 grid cycle.
As it can be seen that if L is less than or equal to M, only with the switching angle for determining each moment in the L moment in step S42
Degree can enter step S5；If L is more than M, the switch angle in a PID control period is obtained by off-line calculation,
Can time-out obtain, therefore can first off-line calculation obtain the switch angle in a PID control period, remaining L-1*M moment
Switch angle according to described in step S43, the S1 that gos to step continues the off-line calculation of the second wheel, if L-1*M is more than M,
Continue the off-line calculation of third round, and so on, until after being taken turns to P, the switch angle at remaining L-P*M moment less than etc.
In M, then it can take turns one-time calculation in P+1 and obtain the switch angle at the L-P*M moment.In this way, having obtained L moment
Angle is switched to get to the switch angle of 1/4 grid cycle.
About step S5：
With reference to figure 6, a in figure1、a2、……、ak... indicate that the switch angle at each moment, 0- pi/2s indicate 1/4 power grid week
Phase, 0- π indicate that 1/2 grid cycle, 0-2 π indicate complete grid cycle.
The switch angle under 1/4 grid cycle is expanded to obtain grid cycle described in the step S5
Pwm pulse signal includes：Switch angle under 1/4 grid cycle is subjected to mirror image and obtains the switch in 1/4-1/2 grid cycles
Angle, mirror image obtains the switch angle in 1/2-1 grid cycles again after the switch angle under 1/2 grid cycle is carried out reversely.
The pwm pulse of whole cycle is expanded to obtain by the switch angle under 1/4 grid cycle, belongs to the spy of synchronous modulation
Point, this modulator approach can effectively reduce the total harmonic distortion of output current compared to asynchronous PWM modulation.
The invention also discloses PWM rectification control systems under a kind of low switching frequency accordingly, are applied to High Power Active
PWM rectifier, including：
Phase locking unit, for the sample frequency f of settingcSample network voltage uAFEWith DC bus-bar voltage Vdc, and be based on
Phaselocked loop phase-lock technique tracks grid phase θsWith mains frequency fs；
Sample frequency and PID control period updating unit, for according to mains frequency fsThe sampling of adjustment setting in real time
Frequency fcAnd update PID control period, the PID control period are equal to sample frequency fcThe corresponding sampling period；
Output voltage amplitude determination unit is based on the newer PID control period, according to the network voltage u of real-time samplingAFE
With DC bus-bar voltage VdcVector controlled is carried out to PWM rectifier and obtains the amplitude U of output voltager；
Grid phase angle determination unit, for being based on the newer PID control period, according to the grid phase of real-time tracking
θsAnd mains frequency fsContinuous grid phase angle in the newer PID control period of off-line calculation one；
Pwm pulse signal generation unit, for the amplitude U according to the output voltager, grid phase angle and prestore
Harmonic wave optimize pulse angle table, obtain the switch angle under 1/4 grid cycle, by the switch angle under 1/4 grid cycle into
Row is expanded and obtains the pwm pulse signal of a grid cycle, and PWM rectifications control is realized according to the pwm pulse signal.
Wherein, the grid phase angle determination unit is with based on the newest obtained grid phase θ of phaselocked loop phase-lock techniques
For initial value, using a newer PID control period as the time of integration, to mains frequency fsIntegral obtains one, and this is newer
Continuous grid phase angle in the PID control period：
Wherein, the pwm pulse signal generation unit includes：
First computation subunit, for the current PID control period to be divided into M moment, according to the continuous power grid phase
Parallactic angle degree respectively obtains the grid phase at M moment, and the voltage magnitude at the M moment is equal to the current PID control period and opens
Begin moment corresponding amplitude Ur；
Second computation subunit, according to the voltage magnitude of the grid phase and M moment at M moment, call prestore it is humorous
Wave optimizes pulse angle table, and the switch angle at each moment in M moment is determined after being tabled look-up；
The subelement that third calculates, triggers the switching angle at the M moment that other units obtained in next PID control period
Degree, until obtaining the switch angle at all moment corresponding to 1/4 grid cycle.
Wherein, the switch angle by under 1/4 grid cycle is expanded to obtain the pwm pulse of a grid cycle
Signal includes：Switch angle under 1/4 grid cycle is subjected to mirror image and obtains the switch angle in 1/4-1/2 grid cycles, it will
Mirror image obtains the switch angle in 1/2-1 grid cycles again after switch angle progress reversely under 1/2 grid cycle.
In conclusion implementing PWM rectifications control method and system under low switching frequency of the invention, have beneficial below
Effect：Sample frequency f of the present inventioncIt is according to mains frequency fsAdjustment obtains, and realizes that sampling instant is synchronous with grid phase, full
The basic demand of sufficient synchronous modulation；Continuous grid phase angle in one PID control period of off-line calculation, it is excellent using harmonic wave
Change pulse angle table method of calling and export pwm pulse, realizes that off-line calculation obtains the switching angle so that current harmonic content minimum
Degree, and the characteristics of the pwm pulse of whole cycle is expanded to obtain, belong to synchronous modulation by the switch angle under 1/4 grid cycle, this
Kind modulator approach can effectively reduce the total harmonic distortion of output current compared to asynchronous PWM modulation；Further, electricity is being calculated
When net phase angle, integral is all with based on the newest obtained grid phase θ of phaselocked loop phase-lock technique every timesIt, can for initial value
To overcome the limitation of sampling precision, continuous grid phase information is obtained, while realizing phase bit comparison amendment, makes switch angle
It calculates more accurate；The sample frequency f of adjustment setting in real timecEqual to N*fs, sampling precision is improved, while output PWM electricity can be improved
The stability of pressure.
The embodiment of the present invention is described with above attached drawing, but the invention is not limited in above-mentioned specific
Embodiment, the above mentioned embodiment is only schematical, rather than restrictive, those skilled in the art
Under the inspiration of the present invention, without breaking away from the scope protected by the purposes and claims of the present invention, it can also make very much
Form, all of these belong to the protection of the present invention.
Claims (8)
1. PWM rectifications control method under a kind of low switching frequency is applied to the PWM rectifier of High Power Active, which is characterized in that
The method includes：
S1, the sample frequency f with settingcSample network voltage uAFEWith DC bus-bar voltage Vdc, and it is based on phaselocked loop phase-lock technique
Track grid phase θsWith mains frequency fs, according to mains frequency fsThe sample frequency f of adjustment setting in real timecEqual to N*fsAnd more
In the new PID control period, N is positive integer；
S2, it is based on the newer PID control period, according to the network voltage u of real-time sampling in step S1AFEAnd DC bus-bar voltage
VdcVector controlled is carried out to PWM rectifier and obtains the amplitude U of output voltager；
S3, it is based on the newer PID control period, according to the grid phase θ of real-time tracking in step S1sAnd mains frequency fsFrom
Continuous grid phase angle in the newer PID control period of line computation one；
S4, the amplitude U according to output voltager, grid phase angle and prestore harmonic wave optimization pulse angle table, obtain 1/4 electricity
Switch angle under the net week phase；
S5, it is expanded the switch angle under 1/4 grid cycle to obtain the pwm pulse signal of a grid cycle, according to this
Pwm pulse signal realizes PWM rectifications control；
The step S3 includes：With based on the newest obtained grid phase θ of phaselocked loop phase-lock techniquesFor initial value, updated with one
The PID control period be the time of integration, to mains frequency fsIntegral obtains continuous in the newer PID control period
Grid phase angle：
2. PWM rectifications control method under low switching frequency according to claim 1, which is characterized in that the PID control week
Phase is equal to sample frequency fcCorresponding sampling period, the step S4 include：
S41, the current PID control period is divided into M moment, when respectively obtaining M according to the continuous grid phase angle
The voltage magnitude of the grid phase at quarter, the M moment is equal to current start time in PID control period corresponding amplitude Ur；
S42, the voltage magnitude according to the grid phase and M moment at M moment call the harmonic wave to prestore to optimize pulse angle
Table determines the switch angle at each moment in M moment after being tabled look-up；
S43, S1 is gone to step to obtain the switch angle at M moment in next PID control period, until obtaining 1/4
The switch angle at all moment corresponding to grid cycle.
3. PWM rectifications control method under low switching frequency according to claim 1, which is characterized in that in the step S5
The pwm pulse signal that switch angle under 1/4 grid cycle is expanded to obtain a grid cycle includes：By 1/
Switch angle under 4 grid cycles carries out mirror image and obtains the switch angle in 1/4-1/2 grid cycles, will be under 1/2 grid cycle
Switch angle carry out it is reversed after again mirror image obtain the switch angle in 1/2-1 grid cycles.
4. PWM rectifications control method under low switching frequency according to claim 1, which is characterized in that
In the step S1, on the basis of locking phase output phase, in k-th of sampling instant, the power grid phase of the phaselocked loop output
Position θSFor k* (2 π/N), wherein k=0,1 ..., N-1.
5. PWM rectifications control method under low switching frequency according to claim 1, which is characterized in that the step S2 packets
It includes：
S21, by DC bus-bar voltage VdcWith target voltage Vdc *Watt current is obtained through pi regulator instruct i after being comparedd *；
S22, according to network voltage uAFEPower network current i is calculatedAFE, with grid phase θSOrientation carries out dq and converts to obtain d axis electricity
Flow idWith q shaft currents iq；
S23, by d shaft currents idI is instructed with watt currentd *It obtains through pi regulator representing the active of output voltage after being compared
The d axis of component instructs ud, by q shaft currents iqWith the referenced reactive current i of user settingq *It is obtained through pi regulator after being compared
Represent the q axis instruction u of the reactive component of output voltageq；
S24, the amplitude U that output voltage is calculated according to following formular：
6. PWM rectification control systems under a kind of low switching frequency are applied to the PWM rectifier of High Power Active, which is characterized in that
Including：
Phase locking unit, for the sample frequency f of settingcSample network voltage uAFEWith DC bus-bar voltage Vdc, and it is based on locking phase
Ring phase-lock technique tracks grid phase θsWith mains frequency fs；
Sample frequency and PID control period updating unit, for according to mains frequency fsThe sample frequency f of adjustment setting in real timec
Equal to N*fsAnd the update PID control period, N is positive integer；
Output voltage amplitude determination unit is based on the newer PID control period, according to the network voltage u of real-time samplingAFEWith it is straight
Flow busbar voltage VdcVector controlled is carried out to PWM rectifier and obtains the amplitude U of output voltager；
Grid phase angle determination unit, for being based on the newer PID control period, according to the grid phase θ of real-time trackingsWith
And mains frequency fsContinuous grid phase angle in the newer PID control period of off-line calculation one；
Pwm pulse signal generation unit, for according to amplitude Ur, grid phase angle and prestore harmonic wave optimization pulse angle
Table obtains the switch angle under 1/4 grid cycle, and the switch angle under 1/4 grid cycle is expanded to obtain a power grid
The pwm pulse signal in period realizes PWM rectifications control according to the pwm pulse signal；
The grid phase angle determination unit is with based on the newest obtained grid phase θ of phaselocked loop phase-lock techniquesFor initial value,
Using a newer PID control period as the time of integration, to mains frequency fsIntegral obtains the newer PID control period
Interior continuous grid phase angle：
7. PWM rectification control systems under low switching frequency according to claim 6, which is characterized in that the PID control week
Phase is equal to sample frequency fcCorresponding sampling period, the pwm pulse signal generation unit include：
First computation subunit, for the current PID control period to be divided into M moment, according to the continuous grid phase angle
Degree respectively obtains the grid phase at M moment, when the voltage magnitude at the M moment is equal to the current PID control period and starts
Carve corresponding amplitude Ur；
Second computation subunit calls the harmonic wave to prestore excellent according to the voltage magnitude of the grid phase and M moment at M moment
Change pulse angle table, the switch angle at each moment in M moment is determined after being tabled look-up；
The subelement that third calculates, triggers the switch angle at the M moment that other units obtained in next PID control period,
Until obtaining the switch angle at all moment corresponding to 1/4 grid cycle.
8. PWM rectification control systems under low switching frequency according to claim 6, which is characterized in that described by 1/4 electricity
The pwm pulse signal that switch angle under the net week phase is expanded to obtain a grid cycle includes：It will be under 1/4 grid cycle
Switch angle carries out mirror image and obtains the switch angle in 1/4-1/2 grid cycles, and the switch angle under 1/2 grid cycle is carried out
Mirror image obtains the switch angle in 1/2-1 grid cycles again after reversed.
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| CN103401405A (en) * | 2013-08-05 | 2013-11-20 | 天津电气传动设计研究所有限公司 | Method for realizing selective harmonic elimination modulation by adopting fixed control cycle |
| CN103532170A (en) * | 2013-10-31 | 2014-01-22 | 哈尔滨工业大学 | Fixed control method for switching period for grid-connected current hysteresis control algorithm |
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| CN102136716A (en) * | 2010-09-08 | 2011-07-27 | 上海岩芯电子科技有限公司 | Grid frequency detection method based on phase locked loop technology |
| CN103401405A (en) * | 2013-08-05 | 2013-11-20 | 天津电气传动设计研究所有限公司 | Method for realizing selective harmonic elimination modulation by adopting fixed control cycle |
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