CN105846697A - PWM rectification control method under low switching frequency and PWM rectification control system thereof - Google Patents
PWM rectification control method under low switching frequency and PWM rectification control system thereof Download PDFInfo
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- CN105846697A CN105846697A CN201610292325.0A CN201610292325A CN105846697A CN 105846697 A CN105846697 A CN 105846697A CN 201610292325 A CN201610292325 A CN 201610292325A CN 105846697 A CN105846697 A CN 105846697A
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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
The invention provides a PWM rectification control method under low switching frequency and a PWM rectification control system thereof. The method comprises the steps that S1. power grid voltage and DC bus voltage are sampled, the power grid phase and the power grid frequency are tracked based on a phase-locked loop phase locking method, and sampling frequency is adjusted and a PID control period is updated according to the power grid frequency; S2. vector control is performed on a PWM rectifier based on the updated PID control period according to the power grid voltage and the DC bus voltage so that the amplitude Ur of output voltage is obtained; S3. continuous power grid phase angles in one PID control period are calculated based on the updated PID control period according to the power grid phase and the power grid frequency; S4. a switching angle under the 1/4 power grid period is obtained according to the amplitude Ur, the power grid phase angles and a pre-stored harmonic optimization pulse angle table; and S5. the switching angle under the 1/4 power grid period is expanded so that PWM pulse signals of one power grid period are obtained. The PWM pulse generation method belongs to the characteristic of synchronous modulation, and total harmonic distortion of output current can be effectively reduced in comparison with that of asynchronous modulation.
Description
Technical field
The present invention relates to technical field of electric power, particularly relate to PWM rectification control method under a kind of low switching frequency
And system.
Background technology
Existing three level four-quadrant frequency-converter devices, use three level neutral-point-clamped (Neutral Point
Clamped), back to back structure connects, and its Active Front End uses PWM rectifier with electrical network by reactor even
Connect.The conventional art of PWM rectifier voltage-type SPWM of employing in control mode control more.
SPWM control method, based on system mathematical model under grid voltage orientation dq rotating coordinate system, is adopted
Vector controlled is realized by voltage, current double closed-loop structure.With reference to Fig. 1, first, obtained by PHASE-LOCKED LOOP PLL TECHNIQUE
To real-time grid phase thetaS；Then, on the one hand sample DC bus-bar voltage Vdc, by VdcWith target voltage Vdc *
Watt current instruction i is obtained through pi regulator after comparingd*, on the other hand the input of sampling AFE three-phase is electric
Pressure uAFE, according to uAFEIt is calculated AFE three-phase input current iAFE, with θSOrientation carries out dq conversion and obtains
D shaft current idWith q shaft current iq；Subsequently by idWith id *Exported through pi regulator after comparing
The d axle instruction u of voltaged, equally, by iqWith i is manually setq *Compare, obtain output voltage
Q axle instruction uq；Finally by udAnd uqWith θSOrientation carries out dq conversion and obtains SPWM control instruction ua、ub、
uc。
Obtain ua、ub、ucAfter use common asynchronous PWM strategy again, it is achieved the arrow of PWM rectifier
Amount controls.In modulation system, the starting point at each triangular carrier was sampled with the summit moment, carrier frequency
Determine sample frequency and the control cycle of whole control system.Generally the approximation letter of PWM link
Turn to first order inertial loop.Use traditional symmetric triangular carrier modulation method, generally remain carrier frequency fcGu
Fixed constant, as frequency of modulated wave frDuring change, carrier wave ratio N is change.In the half period of modulating wave,
The pulse number of PWM ripple is not fixed, and phase place is not fixed, and the pulse of positive-negative half-cycle is asymmetric, in the half period
Front and back the pulse in 1/4 cycle is the most asymmetric.In a word, prior art uses common asynchronous PWM, and adopts
Sample frequency is fixed, and does not has synchronized relation with grid phase.
Above-mentioned frequency converter control method is analyzed mainly for the situation that PWM switching frequency is higher, designs,
Its control method is not suitable in high-power field, otherwise will cause such as output waveform harmonic distortion
Greatly, degradation problem under control system bandwidth reduction, speed adjusting performance.Prior art in Control System Design,
Generally PWM link approximation being reduced to the premise of first order inertial loop is: the switch lock of PWM
Rate is higher, and time delay is relatively small, can ignore this time delay impact on control system.And along with switching frequency
Reduction, in the occasion of the low switching frequency of below 500Hz, the delay of PWM link significantly increases.
When switching frequency is higher, the output waveform of PWM is practically free of low-order harmonic, and higher hamonic wave
Because of it, frequency relative system bandwidth is higher can be left in the basket；Use traditional symmetric triangular carrier modulation method,
The starting point of each triangular carrier was sampled with the summit moment, all can directly obtain first-harmonic.
When switching frequency is relatively low, because of dead band, non-linear and realize the reason of precision, in control system relative to
There is more low-order harmonic in high switching frequency situation, if directly using the methods such as low-pass filtering to filter harmonic wave,
The time delay then filtering link in dynamic process will seriously reduce stability and the dynamic property of control system, even
Cannot restrain, traditional control method can not effectively resist low-order harmonic while quickly following the tracks of first-harmonic instruction
Disturbance.
PWM rectifier in pressure high-power applications at present, its switching loss raises with modulating frequency and increases,
Device design capacity is relatively big, and response modulating frequency reduces, therefore preferably with low switching frequency, and low switch
Frequency can cause the harmonic wave of output voltage to increase, and affects the normal work of system time serious.Especially in big merit
In rate grid-connected converter, output capacity should be met, reduce switching frequency, meet networking harmonic requirement again,
Above-mentioned prior art is used to meet.
Summary of the invention
The technical problem to be solved in the present invention is, for the drawbacks described above of prior art, it is provided that one is low to be opened
Close PWM rectification control method and system under frequency.
The technical solution adopted for the present invention to solve the technical problems is: PWM under a kind of low switching frequency of structure
Rectification control method, is applied to the PWM rectifier of High Power Active, and described method includes:
S1, with set sample frequency fcSampling line voltage uAFEWith DC bus-bar voltage Vdc, and based on lock
Phase ring phase-lock technique follows the tracks of grid phase θsWith mains frequency fs, according to mains frequency fsAdjust setting in real time
Sample frequency fcAnd update the PID control cycle；
S2, PID based on renewal control the cycle, according to the line voltage u of real-time sampling in step S1AFEWith
DC bus-bar voltage VdcPWM rectifier is carried out vector controlled and obtains amplitude U of output voltager；
S3, PID based on renewal control the cycle, according to the grid phase θ of real-time tracking in step S1sWith
And mains frequency fsContinuous print grid phase angle in the PID control cycle of one this renewal of calculated off line；
S4, amplitude U according to output voltager, grid phase angle and the harmonic wave that prestores optimize pulse angle
Degree table, obtains the switch angle under 1/4 grid cycle；
S5, carry out the switch angle under 1/4 grid cycle expanding the pwm pulse obtaining a grid cycle
Signal, realizes PWM rectification according to this pwm pulse signal and controls.
Under low switching frequency of the present invention in PWM rectification control method, described step S3 includes:
With based on the up-to-date grid phase θ obtained of phaselocked loop phase-lock techniquesFor initial value, control with a PID updated
Cycle processed is the time of integration, to mains frequency fsCompany in the PID control cycle that integration obtains this renewal
Continuous grid phase angle:
Under low switching frequency of the present invention in PWM rectification control method, the described PID control cycle etc.
In sample frequency fcIn the corresponding sampling period, described step S4 includes:
S41, the cycle that controlled by current PID are divided into M moment, according to this continuous print grid phase angle
Respectively obtaining the grid phase in M moment, the voltage magnitude in this M moment is equal to current PID and controls
Amplitude U that start time in cycle is correspondingr；
S42, according to the grid phase in M moment and the voltage magnitude in M moment, call the harmonic wave prestored
Optimize pulse angle table, after tabling look-up, determine the switch angle in each moment in M moment；
S43, jump to step S1 to obtain the switch angle in M moment in the next PID control cycle,
Until obtaining the switch angle in all moment corresponding to 1/4 grid cycle.
Under low switching frequency of the present invention in PWM rectification control method, described in described step S5
The switch angle under 1/4 grid cycle is carried out expand the pwm pulse signal bag obtaining a grid cycle
Include: the switch angle under 1/4 grid cycle is carried out mirror image and obtains the switching angle in 1/4-1/2 grid cycle
Degree, in after the switch angle under 1/2 grid cycle being carried out reversely, mirror image obtains 1/2-1 grid cycle again
Switch angle.
Under low switching frequency of the present invention in PWM rectification control method,
If the mains frequency of described phaselocked loop output is f in described step S1S, then setting is adjusted in real time
Sample frequency fcEqual to N*fs, on the basis of phase-locked output phase place, at kth sampling instant, described lock
The grid phase θ of phase ring 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 rectification control method, described step S2 includes:
S21, by DC bus-bar voltage VdcWith target voltage Vdc *Gained merit through pi regulator after comparing
Current-order id *；
S22, according to line voltage uAFEIt is calculated power network current iAFE, with grid phase θSOrientation carries out dq
Conversion obtains d shaft current idWith q shaft current iq；
S23, by d shaft current idI is instructed with watt currentd *Obtain representing defeated after comparing through pi regulator
Go out the d axle instruction u of the real component of voltaged, by q shaft current iqReferenced reactive current with user setup
iq *Obtain representing the q axle instruction u of the idle component of output voltage through pi regulator after comparingq；
S24, it is calculated amplitude U of output voltage according to below equationr:
The invention also discloses PWM rectification control system under a kind of low switching frequency, be applied to High Power Active
PWM rectifier, including:
Phase locking unit, for sample frequency f to setcSampling line voltage uAFEWith DC bus-bar voltage Vdc,
And follow the tracks of grid phase θ based on phaselocked loop phase-lock techniquesWith mains frequency fs；
Sample frequency and PID control cycle updating block, for according to mains frequency fsAdjust setting in real time
Sample frequency fcAnd update the PID control cycle；
Output voltage amplitude determines unit, controls the cycle based on the PID updated, according to the electrical network of real-time sampling
Voltage uAFEWith DC bus-bar voltage VdcPWM rectifier is carried out vector controlled and obtains the amplitude of output voltage
Ur；
Grid phase angle determination unit, for controlling the cycle based on the PID updated, according to real-time tracking
Grid phase θsAnd mains frequency fsContinuous print in the PID control cycle of one this renewal of calculated off line
Grid phase angle；
Pwm pulse signal signal generating unit, for according to amplitude Ur, grid phase angle and the harmonic wave that prestores
Optimize pulse angle table, obtain the switch angle under 1/4 grid cycle, by the switch under 1/4 grid cycle
Angle carries out expanding the pwm pulse signal obtaining a grid cycle, realizes according to this pwm pulse signal
PWM rectification controls.
Under low switching frequency of the present invention in PWM rectification control system, described grid phase angle is true
Cell is with based on the up-to-date grid phase θ obtained of phaselocked loop phase-lock techniquesFor initial value, update with one
The PID control cycle is the time of integration, to mains frequency fsIntegration obtains the PID of this renewal and controls the cycle
Interior continuous print grid phase angle:
Under low switching frequency of the present invention in PWM rectification control system, the described PID control cycle etc.
In sample frequency fcIn the corresponding sampling period, described pwm pulse signal signal generating unit includes:
First computation subunit, is divided into M moment for current PID controls the cycle, continuous according to this
Grid phase angle respectively obtain the grid phase in M moment, the voltage magnitude in this M moment is equal to
Amplitude U that current PID control start time in cycle is correspondingr；
Second computation subunit, according to grid phase and the voltage magnitude in M moment in M moment, calls
The harmonic wave prestored optimizes pulse angle table, determines the switch angle in each moment in M moment after tabling look-up；
3rd subelement calculated, triggers other unit and obtains M the moment in the next PID control cycle
Switch angle, until obtaining the switch angle in all moment corresponding to 1/4 grid cycle.
Under low switching frequency of the present invention in PWM rectification control system, described is all by 1/4 electrical network
Switch angle under phase carries out expanding and obtains the pwm pulse signal of a grid cycle and include: by 1/4 electrical network
Switch angle under cycle carries out the switch angle that mirror image obtains in 1/4-1/2 grid cycle, by 1/2 electrical network
Switch angle under cycle carries out the switch angle in mirror image obtains 1/2-1 grid cycle again after reversely.
Implement PWM rectification control method and system under the low switching frequency of the present invention, there is following useful effect
Really: sample frequency f of the present inventioncIt is according to mains frequency fsAdjustment obtains, it is achieved sampling instant and grid phase
Synchronization, meet the basic demand of synchronous modulation；Continuous print electricity in one PID control cycle of calculated off line
Net phase angle, uses harmonic wave to optimize pulse angle table method of calling output pwm pulse, it is achieved calculated off line
Obtain the switch angle minimum so that current harmonic content, and the pwm pulse in whole cycle is by 1/4 electrical network week
Switch angle under phase is expanded and is obtained, and belongs to the feature of synchronous modulation, and this modulator approach is compared to asynchronous
PWM, can effectively reduce the total harmonic distortion of output electric current；
Further, when calculating grid phase angle, each integration is all with based on phaselocked loop phase-lock technique
The up-to-date grid phase θ obtainedsFor initial value, the restriction of sampling precision can be overcome, obtain continuous print electrical network
Phase information, realizes phase bit comparison correction simultaneously, and the calculating making switch angle is more accurate；Adjust setting in real time
Sample frequency fcEqual to N*fs, improve sampling precision, stablizing of output PWM voltage can be improved simultaneously
Property.
Accompanying drawing explanation
Below in conjunction with drawings and Examples, the invention will be further described, in accompanying drawing:
Fig. 1 is the model schematic generating pwm pulse in prior art；
Fig. 2 is the method flow diagram of the present invention；
Fig. 3 is the model schematic of the method generation pwm pulse of the present invention；
Fig. 4 be the present invention method in sampling instant and grid phase relation；
Fig. 5 is the schematic diagram that in step S3, integration obtains continuous print grid phase angle；
Fig. 6 is the schematic diagram expanding the pwm pulse signal obtaining a grid cycle in step S5.
Detailed description of the invention
In order to be more clearly understood from the technical characteristic of the present invention, purpose and effect, now comparison accompanying drawing is detailed
Describe the detailed description of the invention of the bright present invention in detail.
As in figure 2 it is shown, be the method flow diagram of the present invention.
PWM rectification control method under the low switching frequency of the present invention, is applied to the PWM rectification of High Power Active
Device, specifically includes that
S1, with set sample frequency fcSampling line voltage uAFEWith DC bus-bar voltage Vdc, and based on lock
Phase ring phase-lock technique follows the tracks of grid phase θsWith mains frequency fs, according to mains frequency fsAdjust setting in real time
Sample frequency fcAnd update the PID control cycle；
Wherein, described PID controls the cycle equal to sample frequency fcThe corresponding sampling period；
S2, PID based on renewal control the cycle, according to the line voltage u of real-time sampling in step S1AFEWith
DC bus-bar voltage VdcPWM rectifier is carried out vector controlled and obtains amplitude U of output voltager；
S3, PID based on renewal control the cycle, according to the grid phase θ of real-time tracking in step S1sWith
And mains frequency fsContinuous print grid phase angle in the PID control cycle of one this renewal of calculated off line；
S4, amplitude U according to output voltager, grid phase angle and the harmonic wave that prestores optimize pulse angle
Degree table, obtains the switch angle under 1/4 grid cycle；
S5, carry out the switch angle under 1/4 grid cycle expanding the pwm pulse obtaining a grid cycle
Signal, realizes PWM rectification according to this pwm pulse signal and controls.
Below in conjunction with Fig. 3, successively each above step is described in detail.
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
The line voltage u that sampling obtainsAFE, output is grid phase θsWith mains frequency fs, therefore frequently with lock
Phase method follows the tracks of grid phase θsWith mains frequency fs。
The application, in order to realize the effect of synchronous modulation, uses self adaptation phase-lock technique, in described step S1
If the mains frequency of described phaselocked loop output is fS, then sample frequency f set is adjusted in real timecIt is equal to
N*fs, and on the basis of phase-locked output phase place, with reference in Fig. 4, at kth sampling instant, described lock
The grid phase θ of phase ring outputSFor k* (2 π/N), wherein k=0,1 ..., N-1, N are positive integer.
The most just say that sample frequency is not changeless, but adjust in real time according to mains frequency, because of
This is it can be seen that the time interval between any two sampling instant in Fig. 4 is change.Owing to adjusting in real time
Sample frequency f of whole settingcEqual to N*fs, sample frequency f of the present inventioncIt is according to mains frequency fsIt is adjusted so as to
Arrive, it is achieved sampling instant is synchronization with grid phase, improve sampling precision, output PWM can be improved simultaneously
The stability of voltage, meets the basic demand of synchronous modulation.
About step S2:
Continuing with Fig. 3, described step S2 includes:
S21, by DC bus-bar voltage VdcWith target voltage Vdc *Gained merit through pi regulator after comparing
Current-order id *；
S22, according to line voltage uAFEIt is calculated power network current iAFE, with grid phase θSOrientation carries out dq
Conversion obtains d shaft current idWith q shaft current iq；
It practice, net electric current iAFEDirectly can also directly be obtained by current sample, this is not limited.
S23, by d shaft current idI is instructed with watt currentd *Obtain representing defeated after comparing through pi regulator
Go out the d axle instruction u of the real component of voltaged, by q shaft current iqReferenced reactive current with user setup
iq *Obtain representing the q axle instruction u of the idle component of output voltage through pi regulator after comparingq；
S24, it is calculated amplitude U of output voltage according to below equationr:
About step S3:
With reference to Fig. 5, described step S3 with in step S1 based on the up-to-date electrical network obtained of phaselocked loop phase-lock technique
Phase thetasFor initial value, control the cycle as the time of integration with PID updated, to mains frequency fsIntegration
Continuous print grid phase angle in the PID control cycle obtaining this renewal:
Such as, t in Fig. 50-t1、t1-t2、t2-t3... represent a sampling period, namely difference respectively
Represent that a PID controls the cycle.It is only capable of obtaining t by step S10、t1、t2、t3... when these are discrete
The mains frequency f carvedsIf be not integrated, then the ladder that the grid phase obtained of sampling there will be in figure
The change of shape, PID controls the mains frequency f in the cycle (namely a sampling period)sIt is unknown, for
Obtain the mains frequency f in the PID control cycles, the present invention uses offline computing method to pass through integration
Time-out is calculated the continuous print grid phase angle in the PID control cycle, can overcome sampling precision
Restriction, obtain continuous print grid phase information, such as the curved section Y in figure01、Y12、Y23... represent respectively
Continuous print grid phase information in one PID control cycle.
And, the present invention is when each integration, uses based on the up-to-date electrical network obtained of phaselocked loop phase-lock technique
Phase thetasNumerical value for initial value rather than an above integration period finish time is initial value, is equivalent to
Realizing phase bit comparison correction, the calculating making switch angle is more accurate.Y in i.e. Fig. 512Initial value be not Y01's
The numerical value of finish time, but according to the phase-locked mains frequency f obtained of phaselocked loops, the like.
About step S4:
Sample frequency f in previous step S1cEqual to N*fs, therefore, grid cycle is equal to the sampling period
N times.Step S4 is the pwm pulse information obtaining 1/4 grid cycle, is to use expansion side in step S5
Formula obtains the pwm pulse information in complete grid cycle.In order to obtain the PWM of 1/4 grid cycle
Pulse information, PID control cycle (sampling period) is carried out thinner division, is divided into M by the present invention
The individual moment, then a grid cycle includes N*M moment, by the moment sum corresponding to 1/4 grid cycle
1/4*N*M is designated as L, and step S4 is i.e. intended to determine the switch angle in this L moment.
Described step S4 includes:
S41, the cycle that controlled by current PID are divided into M moment, according to this continuous print grid phase angle
Respectively obtaining the grid phase in M moment, the voltage magnitude in this M moment is equal to current PID and controls
Amplitude U that start time in cycle is correspondingr；
Visible, the phase place in each moment is to utilize continuous print grid phase angle to obtain, and in view of one
In the PID control cycle, the amplitude no-load voltage ratio of output voltage is the least, it is believed that the width in the PID control cycle
Value UrIt is constant.
S42, according to the grid phase in M moment and the voltage magnitude in M moment, call the harmonic wave prestored
Optimize pulse angle table, after tabling look-up, determine the switch angle in each moment in M moment；
Wherein, harmonic wave optimize pulse angle table be table known in the art, which describe major part voltage magnitude,
The switch angle making harmonic wave minimum corresponding to phase place.
S43, jump to step S1 to obtain the switch angle in M moment in the next PID control cycle,
Until obtaining the switch angle in all moment (i.e. L moment) corresponding to 1/4 grid cycle.
Visible, if L is less than or equal to M, then in step S42 only with determine in this L moment each time
The switch angle carved can enter step S5；If L is more than M, the then switch in the PID control cycle
Angle is to be obtained by calculated off line, can time-out obtain, and therefore first calculated off line can obtain a PID control
Switch angle in cycle, the switch angle in remaining L-1*M moment, according to described in step S43, redirects
Continue the second calculated off line taken turns to step S1, if L-1*M is more than M, then continue the off-line of third round
Calculate, by that analogy, until after taking turns to P, the switch angle in remaining L-P*M moment is less than or equal to
M, then can obtain the switch angle in this L-P*M moment in P+1 wheel one-time calculation.So,
Arrive the switch angle in L moment, i.e. obtain the switch angle of 1/4 grid cycle.
About step S5:
With reference to Fig. 6, a in figure1、a2、……、ak... represent the switch angle in each moment, 0-pi/2
Represent that 1/4 grid cycle, 0-π represent that 1/2 grid cycle, 0-2 π represent complete grid cycle.
The switch angle under 1/4 grid cycle carried out expansion obtain an electricity described in described step S5
The pwm pulse signal in net cycle includes: the switch angle under 1/4 grid cycle is carried out mirror image and obtains
Switch angle in 1/4-1/2 grid cycle, after the switch angle under 1/2 grid cycle being carried out reversely again
Mirror image obtains the switch angle in 1/2-1 grid cycle.
The pwm pulse in whole cycle is expanded by the switch angle under 1/4 grid cycle and is obtained, and belongs to same step
The feature of system, this modulator approach, compared to asynchronous PWM, can effectively reduce total harmonic wave of output electric current
Distortion.
The invention also discloses PWM rectification control system under a kind of low switching frequency accordingly, be applied to big merit
The PWM rectifier that rate is active, including:
Phase locking unit, for sample frequency f to setcSampling line voltage uAFEWith DC bus-bar voltage Vdc,
And follow the tracks of grid phase θ based on phaselocked loop phase-lock techniquesWith mains frequency fs；
Sample frequency and PID control cycle updating block, for according to mains frequency fsAdjust setting in real time
Sample frequency fcAnd updating the PID control cycle, described PID controls the cycle equal to sample frequency fcCorresponding
Sampling period；
Output voltage amplitude determines unit, controls the cycle based on the PID updated, according to the electrical network of real-time sampling
Voltage uAFEWith DC bus-bar voltage VdcPWM rectifier is carried out vector controlled and obtains the amplitude of output voltage
Ur；
Grid phase angle determination unit, for controlling the cycle based on the PID updated, according to real-time tracking
Grid phase θsAnd mains frequency fsContinuous print in the PID control cycle of one this renewal of calculated off line
Grid phase angle；
Pwm pulse signal signal generating unit, for amplitude U according to described output voltager, grid phase angle
And the harmonic wave prestored optimizes pulse angle table, obtain the switch angle under 1/4 grid cycle, by 1/4
Switch angle under grid cycle carries out expanding the pwm pulse signal obtaining a grid cycle, according to this
Pwm pulse signal realizes PWM rectification and controls.
Wherein, described grid phase angle determination unit is with based on the up-to-date electrical network obtained of phaselocked loop phase-lock technique
Phase thetasFor initial value, control the cycle as the time of integration with PID updated, to mains frequency fsIntegration
Continuous print grid phase angle in the PID control cycle obtaining this renewal:
Wherein, described pwm pulse signal signal generating unit includes:
First computation subunit, is divided into M moment for current PID controls the cycle, continuous according to this
Grid phase angle respectively obtain the grid phase in M moment, the voltage magnitude in this M moment is equal to
Amplitude U that current PID control start time in cycle is correspondingr；
Second computation subunit, according to grid phase and the voltage magnitude in M moment in M moment, calls
The harmonic wave prestored optimizes pulse angle table, determines the switch angle in each moment in M moment after tabling look-up；
3rd subelement calculated, triggers other unit and obtains M the moment in the next PID control cycle
Switch angle, until obtaining the switch angle in all moment corresponding to 1/4 grid cycle.
Wherein, described carry out expanding by the switch angle under 1/4 grid cycle obtain a grid cycle
Pwm pulse signal includes: the switch angle under 1/4 grid cycle is carried out mirror image and obtains 1/4-1/2 electrical network
Switch angle in cycle, after the switch angle under 1/2 grid cycle being carried out reversely, mirror image obtains again
Switch angle in 1/2-1 grid cycle.
In sum, implement PWM rectification control method and system under the low switching frequency of the present invention, have
Following beneficial effect: sample frequency f of the present inventioncIt is according to mains frequency fsAdjustment obtains, it is achieved sampling instant
Synchronization with grid phase, meet the basic demand of synchronous modulation；In one PID control cycle of calculated off line
Continuous print grid phase angle, use harmonic wave to optimize pulse angle table method of calling output pwm pulse, real
Existing calculated off line obtains the switch angle minimum so that current harmonic content, and the pwm pulse in whole cycle by
Switch angle under 1/4 grid cycle is expanded and is obtained, and belongs to the feature of synchronous modulation, this modulator approach phase
Compared with asynchronous PWM, the total harmonic distortion of output electric current can be effectively reduced；Further, electricity is being calculated
During net phase angle, each integration is all with based on the up-to-date grid phase θ obtained of phaselocked loop phase-lock techniquesFor
Initial value, can overcome the restriction of sampling precision, obtains continuous print grid phase information, realizes phase place simultaneously
Relatively revising, the calculating making switch angle is more accurate；Adjust sample frequency f set in real timecEqual to N*fs,
Improve sampling precision, the stability of output PWM voltage can be improved simultaneously.
Above in conjunction with accompanying drawing, embodiments of the invention are described, but the invention is not limited in above-mentioned
Detailed description of the invention, above-mentioned detailed description of the invention is only schematic rather than restrictive, this
The those of ordinary skill in field, under the enlightenment of the present invention, is being protected without departing from present inventive concept and claim
Under the ambit protected, it may also be made that a lot of form, within these belong to the protection of the present invention.
Claims (10)
1. a PWM rectification control method under low switching frequency, is applied to the PWM rectification of High Power Active
Device, it is characterised in that described method includes:
S1, with set sample frequency fcSampling line voltage uAFEWith DC bus-bar voltage Vdc, and based on lock
Phase ring phase-lock technique follows the tracks of grid phase θsWith mains frequency fs, according to mains frequency fsAdjust setting in real time
Sample frequency fcAnd update the PID control cycle；
S2, PID based on renewal control the cycle, according to the line voltage u of real-time sampling in step S1AFEWith
DC bus-bar voltage VdcPWM rectifier is carried out vector controlled and obtains amplitude U of output voltager；
S3, PID based on renewal control the cycle, according to the grid phase θ of real-time tracking in step S1sWith
And mains frequency fsContinuous print grid phase angle in the PID control cycle of one this renewal of calculated off line；
S4, amplitude U according to output voltager, grid phase angle and the harmonic wave that prestores optimize pulse angle
Degree table, obtains the switch angle under 1/4 grid cycle；
S5, carry out the switch angle under 1/4 grid cycle expanding the pwm pulse obtaining a grid cycle
Signal, realizes PWM rectification according to this pwm pulse signal and controls.
PWM rectification control method under low switching frequency the most according to claim 1, it is characterised in that
Described step S3 includes: with based on the up-to-date grid phase θ obtained of phaselocked loop phase-lock techniquesFor initial value,
With a PID control cycle updated as the time of integration, to mains frequency fsIntegration obtains this renewal
Continuous print grid phase angle in the PID control cycle:
PWM rectification control method under low switching frequency the most according to claim 1, it is characterised in that
Described PID controls the cycle equal to sample frequency fcIn the corresponding sampling period, described step S4 includes:
S41, the cycle that controlled by current PID are divided into M moment, according to this continuous print grid phase angle
Respectively obtaining the grid phase in M moment, the voltage magnitude in this M moment is equal to current PID and controls
Amplitude U that start time in cycle is correspondingr；
S42, according to the grid phase in M moment and the voltage magnitude in M moment, call the harmonic wave prestored
Optimize pulse angle table, after tabling look-up, determine the switch angle in each moment in M moment；
S43, jump to step S1 to obtain the switch angle in M moment in the next PID control cycle,
Until obtaining the switch angle in all moment corresponding to 1/4 grid cycle.
PWM rectification control method under low switching frequency the most according to claim 1, it is characterised in that
The switch angle under 1/4 grid cycle carried out expansion obtain an electrical network week described in described step S5
The pwm pulse signal of phase includes: the switch angle under 1/4 grid cycle is carried out mirror image and obtains 1/4-1/2
Switch angle in grid cycle, after the switch angle under 1/2 grid cycle being carried out reversely, mirror image obtains again
Switch angle in 1/2-1 grid cycle.
PWM rectification control method under low switching frequency the most according to claim 1, it is characterised in that
If the mains frequency of described phaselocked loop output is f in described step S1S, then setting is adjusted in real time
Sample frequency fcEqual to N*fs, on the basis of phase-locked output phase place, at kth sampling instant, described lock
The grid phase θ of phase ring outputSFor k* (2 π/N), wherein k=0,1 ..., N-1, N are positive integer.
PWM rectification control method under low switching frequency the most according to claim 1, it is characterised in that
Described step S2 includes:
S21, by DC bus-bar voltage VdcWith target voltage Vdc *Gained merit through pi regulator after comparing
Current-order id *；
S22, according to line voltage uAFEIt is calculated power network current iAFE, with grid phase θSOrientation carries out dq
Conversion obtains d shaft current idWith q shaft current iq；
S23, by d shaft current idI is instructed with watt currentd *Obtain representing defeated after comparing through pi regulator
Go out the d axle instruction u of the real component of voltaged, by q shaft current iqReferenced reactive current with user setup
iq *Obtain representing the q axle instruction u of the idle component of output voltage through pi regulator after comparingq；
S24, it is calculated amplitude U of output voltage according to below equationr:
7. a PWM rectification control system under low switching frequency, is applied to the PWM rectification of High Power Active
Device, it is characterised in that including:
Phase locking unit, for sample frequency f to setcSampling line voltage uAFEWith DC bus-bar voltage Vdc,
And follow the tracks of grid phase θ based on phaselocked loop phase-lock techniquesWith mains frequency fs；
Sample frequency and PID control cycle updating block, for according to mains frequency fsAdjust setting in real time
Sample frequency fcAnd update the PID control cycle；
Output voltage amplitude determines unit, controls the cycle based on the PID updated, according to the electrical network of real-time sampling
Voltage uAFEWith DC bus-bar voltage VdcPWM rectifier is carried out vector controlled and obtains the amplitude of output voltage
Ur；
Grid phase angle determination unit, for controlling the cycle based on the PID updated, according to real-time tracking
Grid phase θsAnd mains frequency fsContinuous print in the PID control cycle of one this renewal of calculated off line
Grid phase angle；
Pwm pulse signal signal generating unit, for according to amplitude Ur, grid phase angle and the harmonic wave that prestores
Optimize pulse angle table, obtain the switch angle under 1/4 grid cycle, by the switch under 1/4 grid cycle
Angle carries out expanding the pwm pulse signal obtaining a grid cycle, realizes according to this pwm pulse signal
PWM rectification controls.
PWM rectification control system under low switching frequency the most according to claim 7, it is characterised in that
Described grid phase angle determination unit is with based on the up-to-date grid phase θ obtained of phaselocked loop phase-lock techniquesFor
Initial value, with a PID control cycle updated as the time of integration, to mains frequency fsIntegration obtains one
Continuous print grid phase angle in the PID control cycle of this renewal:
PWM rectification control system under low switching frequency the most according to claim 7, it is characterised in that
Described PID controls the cycle equal to sample frequency fcIn the corresponding sampling period, described pwm pulse signal generates single
Unit includes:
First computation subunit, is divided into M moment for current PID controls the cycle, continuous according to this
Grid phase angle respectively obtain the grid phase in M moment, the voltage magnitude in this M moment is equal to
Amplitude U that current PID control start time in cycle is correspondingr；
Second computation subunit, according to grid phase and the voltage magnitude in M moment in M moment, calls
The harmonic wave prestored optimizes pulse angle table, determines the switch angle in each moment in M moment after tabling look-up；
3rd subelement calculated, triggers other unit and obtains M the moment in the next PID control cycle
Switch angle, until obtaining the switch angle in all moment corresponding to 1/4 grid cycle.
PWM rectification control system under low switching frequency the most according to claim 7, it is characterised in that
Described switch angle under 1/4 grid cycle being carried out expands the pwm pulse letter obtaining a grid cycle
Number include: the switch angle under 1/4 grid cycle is carried out mirror image and obtains opening in 1/4-1/2 grid cycle
Closing angle, after the switch angle under 1/2 grid cycle being carried out reversely, mirror image obtains 1/2-1 grid cycle again
Interior switch angle.
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| CN108173420A (en) * | 2018-01-30 | 2018-06-15 | 无锡市优利康电气有限公司 | A kind of minimum current harmonic wave PWM implementation methods |
| CN110729879A (en) * | 2019-11-01 | 2020-01-24 | 中车永济电机有限公司 | Low harmonic suppression method for four-quadrant converter of electric locomotive |
| CN113325358A (en) * | 2021-05-07 | 2021-08-31 | 南方电网数字电网研究院有限公司 | Method and system for rapidly detecting residual current of intelligent electric meter |
| CN113568339A (en) * | 2021-07-15 | 2021-10-29 | 许继电气股份有限公司 | Converter fixed time delay control method and device |
| CN114859120A (en) * | 2022-06-17 | 2022-08-05 | 烟台东方威思顿电气有限公司 | Harmonic analysis method |
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