CN107681896A - Double duty cycle control arrangements of current mode bridge-type photovoltaic converter - Google Patents
Double duty cycle control arrangements of current mode bridge-type photovoltaic converter Download PDFInfo
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- CN107681896A CN107681896A CN201710899396.1A CN201710899396A CN107681896A CN 107681896 A CN107681896 A CN 107681896A CN 201710899396 A CN201710899396 A CN 201710899396A CN 107681896 A CN107681896 A CN 107681896A
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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
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
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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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- 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
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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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
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The present invention discloses a kind of double duty cycle control arrangements of the current mode bridge converter applied to photovoltaic generating system, and it includes MPPT maximum power point tracking module, photovoltaic cell voltage close loop control device and low-pressure side DC voltage closed-loop control device.Wherein reference signal of the signal of MPPT maximum power point tracking module output as photovoltaic cell voltage；On the one hand the control of photovoltaic cell voltage close loop ensures photovoltaic cell output voltage stabilization, on the other hand also realize and suppress low-frequency ripple content in photovoltaic cell output current, its function is realized by boosting dutycycle；Low-pressure side DC voltage closed-loop control device control low-pressure side voltage matches with dc bus side voltage, so that the current stress of device is smaller, its function is realized by power duty cycle.The implementation of the present invention can ensure the ability that photovoltaic converter realizes relatively low device current stress, high efficiency, stable energy harvesting rate and low-frequency current Ripple Suppression when using thin-film capacitor.
Description
Technical field
The present invention relates to a kind of control device of current mode bridge-type photovoltaic converter, belong to converters control
Technical field.
Background technology
Important form of the photovoltaic AC module (micro- inverter) as photovoltaic generation, with its is easy for installation, hot-swappable,
The features such as redundancy performance is good, energy harvesting rate is high, is more and more paid attention in recent years.
Photovoltaic micro-inverter it is usual based on inverse-excitation type and positive activation type topology, can be obtained in the case of lower-wattage
Obtain high efficiency.With the raising of photoelectric transformation efficiency, monolithic the output power from photovoltaic cells is increasing, to obtain efficient conversion,
Common solution is crisscross parallel normal shock or anti exciting converter, but when power further increases, quantity in parallel needs phase
It should increase, this significantly increases the complexity of micro- inverter.Therefore, researcher is developed to recommend, half-bridge, full-bridge
With micro- inverter based on Zeta.Wherein, the micro- inverter circuit structure of bridge-type is although relative complex, but the electric current of its device
Stress is low, and wave filter design is relatively easy, therefore is now subjected to extensive attention.
It is one of important performance indexes of photovoltaic micro-inverter to weight efficiency, such as CEC efficiency and European efficiency, therefore, micro-
The lifting of inverter efficiency is always study hotspot, at present, is mainly improved from Advanced Control Strategies with circuit topology micro- to be lifted
The weighting efficiency of inverter.For the micro- inverter of bridge-type, because the voltage pulsation of input side photovoltaic cell is very big, cause
Micro- inverter prime DC/DC converters mismatch in input, outlet side voltage so that conversion efficiency reduces.Therefore, some are literary
To offer based on current mode full-bridge converter, the input of control bridge circuit, output voltage match in whole power frequency period,
It ensure that higher conversion efficiency.But this method is applied to the two-stage type combining inverter of relatively high power.
Photovoltaic micro-inverter running environment is severe, to ensure that its life-span matches with photovoltaic cell, it is necessary to using thin-film capacitor
Instead of electrochemical capacitor, low-frequency ripple (LFCR) content of photovoltaic cell output current is thus aggravated, this is maximum to photovoltaic cell
Considerable influence be present in the stability of power output and system.To suppress LFCR, one piece can be increased in micro- inverter by opening
The energy buffer unit that device is formed with energy storage device is closed, but this directly increases the complexity and cost of micro- inverter.For not
Increase the complexity of micro- inverter, energy snubber is all typically carried out using the output filter capacitor of prime DC/DC converters, and
There is different control strategies.Pertinent literature propose Double closed-loop of voltage and current strategy, electric current loop at double power frequency have compared with
Big gain is to ensure current tracking performance, and due to containing low-frequency ripple in feedback voltage, it is therefore necessary to which design voltage ring exists
Open-loop gain very little at double power frequency, which just can guarantee that, is free of ripple in current reference value, cause Voltage loop bandwidth minimum, inversion
The dynamic characteristic of device is very poor.The reason for nearest result of study shows bicyclic strategy restriction LFCR, and propose in control loop
Insertion trapper achieves good control effect to improve the bandwidth of Voltage loop, but what this method directly controlled is filtered electrical
Inducing current, to ensure that instantaneous power is constant, the filter capacitor of front stage converter needs very big value to ensure DC bus-bar voltage
With instantaneous power substantially constant, LFCR otherwise can not be completely eliminated in photovoltaic cell input side electric current.Some photovoltaic DC-to-AC converters
Front stage converter has current source output characteristics, and its output voltage realizes voltage stabilizing by the controller of rear class SPWM combining inverters,
The Voltage Feedback parameter of front stage converter is photovoltaic cell voltage, and current feedback parameters are the directly related boostings of photovoltaic cell
Inductive current, therefore its control effect is preferable, but two presence of the dutycycle of control circuit and phase shifting angle simultaneously of its need couple pass
The amount of system, in addition the transformer primary secondary device of front stage converter use wholly-controled device, the circuit phase for micro- inverter
To complexity.
Therefore, control device corresponding to the front stage converter of bridge-type photovoltaic micro-inverter is found, to ensure the micro- inversion of photovoltaic
Utensil has higher efficiency, and the content for suppressing low-frequency ripple in the output current of photovoltaic cell side is very important, we
Thus case produces.
The content of the invention
Goal of the invention：For the existing deficiency applied to two-stage type photovoltaic micro-inverter front stage converter control technology,
The present invention is using double duty ratio modulation current mode bridge converters, using the voltage of boosting Duty ratio control photovoltaic cell, herein
On the basis of can suppress low-frequency ripple composition in photovoltaic cell output current；On the one hand photovoltaic is controlled using power duty cycle
The watt level of converter processing, on the other hand makes low-pressure side voltage track DC bus-bar voltage, so that electric current in converter
Stress is optimized.The photovoltaic micro-inverter front stage converter of double duty ratio modulations has an efficiency high, and property indices are high
Feature.
Technical scheme：A kind of double duty cycle control arrangements of current mode bridge-type photovoltaic converter include signal detection link,
MPPT maximum power point tracking module, photovoltaic cell voltage controller, low-pressure side voltage controller and signal modulator；Wherein light
Lie prostrate cell voltage controller and include the first subtracter, proportional and integral controller, the second subtracter, the first proportional integration resonance tune
Save device, adder, low-pressure side voltage controller include proportional component, the 3rd subtracter, the second proportional integration resonant regulator with
And signal modulator.
Signal detection link includes 5 output ends, respectively the first output end to the 5th output end.Maximum power point with
Two inputs of track module connect the first output end and the second output end of signal detection link respectively；First subtracter
Positive input terminal, negative input end connect the output end of MPPT maximum power point tracking module and the second output of signal detection link respectively
End；The input of proportional and integral controller connects the output end of the first subtracter；The positive input terminal of second subtracter, negative input
End connects the output end of proportional and integral controller and the 3rd output end of signal detection link respectively；First proportional integration resonance
The input of adjuster connects the output end of the second subtracter；Two positive input terminals of adder are connected respectively to peak power
The output end and the output end of the first proportional integration resonant regulator of point tracking module；The input of proportional component is connected to letter
4th output end of number detection；The positive input terminal of 3rd subtracter is connected the output of proportional component with negative input end respectively
End and the 5th output end of signal detection link；The input of second proportional integration resonant regulator connects the 3rd subtracter
Output end；The first input end of signal modulator is connected the output end of adder respectively with the second input and the second ratio is accumulated
Divide the output end of resonant regulator, the first output end of signal modulator converts with the second output end respectively as photovoltaic bridge-type
First bridge arm switching tube of device and the drive signal of the second bridge arm switching tube.
Photovoltaic cell voltage controller, it is characterised in that inner loop feedback amount is directly related with photovoltaic cell output current
Boost inductor current, and adoption rate integral resonance adjuster, the mains frequency for setting resonant frequency to be equal to twice so that
Boost inductor current accurately tracks a reference value, is not influenceed by converter outlet side different loads；Photovoltaic cell voltage conduct
The feedback quantity of outer shroud, after the double power-frequency ripple current of current inner loop is inhibited, the output power from photovoltaic cells is a stabilization
Value, therefore it is a stable direct current signal to control in the proportional and integral controller output signal of photovoltaic voltage；Pass through above-mentioned voltage
The control of outer shroud, current inner loop so that the low-frequency ripple composition in photovoltaic cell voltage stabilization and photovoltaic cell output current
It is effectively suppressed.
Low-pressure side voltage controller, it is characterised in that its voltage reference value and DC bus-bar voltage close in certain ratio
System, so as to optimize the current stress of switching tube in converter；After adoption rate integral resonance adjuster, in twice of electricity
Great open-loop gain is obtained at net frequency, low-pressure side voltage and DC bus-bar voltage synchronously proportional change is ensure that, enters one
Step reduces the current stress of switching tube in converter.
Signal modulator, its input signal are two dutycycles, modulate first bridge arm and the of bridge converter respectively
Two bridge arms, the dimension of converter is improved, improve the control efficiency of converter.
Beneficial effect：After such scheme, the stabilization and photovoltaic electric of photovoltaic cell output voltage are on the one hand realized
Effective suppression of pond output current low-frequency ripple, on the other hand also achieve converter input, the matching of output voltage, optimization
The current stress of device；Therefore, there is the advantages of good performance indexes, efficiency high using the photovoltaic converter of the present invention.
Brief description of the drawings
Fig. 1 is a kind of double duty cycle control arrangement figures of current mode bridge-type photovoltaic converter of the embodiment of the present invention；
Fig. 2 is the bridge-type photovoltaic converter main circuit of the embodiment of the present invention；
Fig. 3 is the drive waveforms and key operation waveforms of the bridge-type photovoltaic converter of the embodiment of the present invention；
Fig. 4 is the operation mode 1 of the bridge-type photovoltaic converter of the embodiment of the present invention；
Fig. 5 is the operation mode 2 of the bridge-type photovoltaic converter of the embodiment of the present invention；
Fig. 6 is the operation mode 3 of the bridge-type photovoltaic converter of the embodiment of the present invention；
Fig. 7 is the operation mode 4 of the bridge-type photovoltaic converter of the embodiment of the present invention；
Fig. 8 is the operation mode 5 of the bridge-type photovoltaic converter of the embodiment of the present invention；
Fig. 9 is the operation mode 6 of the bridge-type photovoltaic converter of the embodiment of the present invention；
Figure 10 is the photovoltaic converter equivalent schematic of the embodiment of the present invention；
Figure 11 is the boost inductor current inner ring of the embodiment of the present invention, photovoltaic cell outer voltage control block diagram；
Figure 12 is that the boost inductor current inner ring adjuster of the embodiment of the present invention corrects Bode diagram；
Figure 13 is that the photovoltaic cell outer voltage adjuster of the embodiment of the present invention corrects Bode diagram；
Figure 14 be the photovoltaic cell Voltage loop parameter designed by the embodiment of the present invention fix in power, voltage change when
Root locus diagram；
Figure 15 be the embodiment of the present invention designed by photovoltaic cell Voltage loop parameter changed power, voltage fix when
Root locus diagram；
Figure 16 is mesolow of embodiment of the present invention side voltage close loop control block diagram；
Figure 17 is that mesolow of embodiment of the present invention side voltage close loop adjuster corrects Bode diagram；
Figure 18 be low-pressure side voltage closed-loop parameters designed by the embodiment of the present invention fix in power, voltage change when root
Trajectory diagram；
Figure 19 be low-pressure side voltage closed-loop parameters designed by the embodiment of the present invention fix in power, voltage change when root
Trajectory diagram；
Designation in figure：IPVf--- photovoltaic cell output current feedback signal；UPVf--- photovoltaic cell output voltage
Feedback signal；iLf--- boost inductor current feedback signal；UDCf--- dc bus output voltage feedback signal；Udf——
Low-pressure side voltage feedback signal；UPV* --- photovoltaic cell output voltage reference signal； uPVe--- photovoltaic cell output voltage misses
Difference signal；iL* --- boost inductor current reference signal；iLe--- boost inductor current error signal；Ud* --- low-pressure side
Voltage reference signal；Ude--- low-pressure side voltage error signal；Db--- boosting dutycycle；Dp--- power duty cycle；uS1-
uS4--- the drive signal of the switching tubes of first switch Guan Zhi tetra-；Cd--- low-pressure side voltage filter capacitor；Ud--- low-pressure side
Voltage；id--- low-pressure side electric current；CPV--- photovoltaic cell voltage filter electric capacity；UPV--- photovoltaic cell output voltage；
IPV--- photovoltaic cell output current；iL--- boost inductor current；Ldc--- boost inductance；uAB--- high-frequency inverter
AC voltage；Lr--- energy snubber inductance；ir--- energy snubber inductive current；T --- high frequency transformer；N --- it is high
The no-load voltage ratio of frequency power transformer；S1-S4 --- the switching tubes of first switch Guan Zhi tetra-；D1-D2 --- the first diode is to the two or two pole
Pipe；C1-C2--- the first filter capacitor and the second filter capacitor of voltage doubling rectifing circuit；C12--- the of voltage doubling rectifing circuit
One filter capacitor connected with the second filter capacitor after equivalent capacitance value； uCD--- voltage doubling rectifing circuit AC voltage；
irec1-irec2--- the first diode current and the second diode current of voltage doubling rectifing circuit；UDC--- dc bus exports
Voltage；iDC--- dc bus output current；t0- t6--- 6 change of current moment in a switch periods；Impp--- photovoltaic
Equivalent output current during battery Maximum Power Output；Rmpp--- equivalent output resistance during photovoltaic cell Maximum Power Output
It is anti-；Gv(s) --- the transmission function of photovoltaic cell output voltage control outer shroud adoption rate integral controller；Gcb(s) --- rise
Voltage inductance current inner loop uses the transmission function of the first proportional integration resonant regulator；Hr(s) --- the one of signal detection use
Rank low pass filter function；Tcb(s) --- the open-loop transfer function after the compensation of boost inductor current inner ring；Tv(s)
--- the open-loop transfer function after the compensation of photovoltaic cell output voltage outer ring；Gvp(s) --- low-pressure side voltage closed loop using the and
The transmission function of proportional integration resonant regulator；GUd_Dp(s) --- the transmission function of low-pressure side voltage to power duty cycle；
GUd_Db(s) --- the transmission function of low-pressure side voltage to dutycycle of boosting；GUd_UDC(s) --- low-pressure side voltage to dc bus
The transmission function of voltage.
Embodiment
With reference to specific embodiment, the present invention is furture elucidated, it should be understood that these embodiments are merely to illustrate the present invention
Rather than limitation the scope of the present invention, after the present invention has been read, various equivalences of the those skilled in the art to the present invention
The modification of form falls within the application appended claims limited range.
As shown in figure 1, a kind of double duty cycle control arrangements of current mode bridge-type photovoltaic converter include signal detection loop
Section, MPPT maximum power point tracking module, photovoltaic cell voltage controller, low-pressure side voltage controller and signal modulator；Wherein
Photovoltaic cell voltage controller includes the first subtracter, proportional and integral controller, the second subtracter, the first proportional integration resonance
Adjuster, adder, low-pressure side voltage controller include proportional component, the 3rd subtracter, the second proportional integration resonant regulator
And signal modulator.
Signal detection link includes 5 output ends, respectively the first output end to the 5th output end.Maximum power point with
Two inputs of track module connect the first output end and the second output end of signal detection link respectively；First subtracter
Positive input terminal, negative input end connect the output end of MPPT maximum power point tracking module and the second output of signal detection link respectively
End；The input of proportional and integral controller connects the output end of the first subtracter；The positive input terminal of second subtracter, negative input
End connects the output end of proportional and integral controller and the 3rd output end of signal detection link respectively；First proportional integration resonance
The input of adjuster connects the output end of the second subtracter；Two positive input terminals of adder are connected respectively to peak power
The output end and the output end of the first proportional integration resonant regulator of point tracking module；The input of proportional component is connected to letter
4th output end of number detection；The positive input terminal of 3rd subtracter is connected the output of proportional component with negative input end respectively
End and the 5th output end of signal detection link；The input of second proportional integration resonant regulator connects the 3rd subtracter
Output end；The first input end of signal modulator is connected the output end of adder respectively with the second input and the second ratio is accumulated
Divide the output end of resonant regulator, the first output end of signal modulator converts with the second output end respectively as photovoltaic bridge-type
First bridge arm switching tube of device and the drive signal of the second bridge arm switching tube.
Photovoltaic cell voltage controller, it is characterised in that inner loop feedback amount is directly related with photovoltaic cell output current
Boost inductor current, and adoption rate integral resonance adjuster, the mains frequency for setting resonant frequency to be equal to twice so that
Boost inductor current accurately tracks a reference value, is not influenceed by converter outlet side different loads；Photovoltaic cell voltage conduct
The feedback quantity of outer shroud, after the double power-frequency ripple current of current inner loop is inhibited, the output power from photovoltaic cells is a stabilization
Value, therefore it is a stable direct current signal to control in the proportional and integral controller output signal of photovoltaic voltage；Pass through above-mentioned voltage
The control of outer shroud, current inner loop so that the low-frequency ripple composition in photovoltaic cell voltage stabilization and photovoltaic cell output current
It is effectively suppressed.
Low-pressure side voltage controller, it is characterised in that its voltage reference value and DC bus-bar voltage close in certain ratio
System, so as to optimize the current stress of switching tube in converter；After adoption rate integral resonance adjuster, in twice of electricity
Great open-loop gain is obtained at net frequency, low-pressure side voltage and DC bus-bar voltage synchronously proportional change is ensure that, enters one
Step reduces the current stress of switching tube in converter.
Signal modulator, its input signal are two dutycycles, modulate first bridge arm and the of bridge converter respectively
Two bridge arms, the dimension of converter is improved, improve the control efficiency of converter.
Fig. 2 show the photovoltaic converter main circuit that Fig. 1 is controlled, wherein boost inductance Ldc, switching tube S1-S2 form
Bridge arm, low-pressure side filter capacitor CdConstitute booster converter；Switching tube S1-S4, buffer inductance Lr, transformer T, diode
D1-D2, electric capacity C1-C2Constitute a kind of bridge-type class resonance DC/DC converters.As can be seen that the converter has following characteristics：
1. the bridge arm multiplexing functions that switching tube S1-S2 is formed, are realized on the basis of circuit complexity is not increased to relatively low photovoltaic electric
The rise of cell voltage；2. low-pressure side DC voltage UdControl can be realized by S1 dutycycle, to match DC bus-bar voltage UDC,
Realize less device current stress；3. control S3-S4 dutycycle, it is possible to achieve the control of transimission power；4. due to micro- inverse
Become the relatively small power of device, by inductive current design in discontinuous mode, the ZVS or ZCS of achievable switching device；5. two poles
Pipe D1-D2, electric capacity C1-C2The voltage doubling rectifing circuit of composition is simple, alleviates the excessive situation of transformer voltage ratio.
Fig. 3 is the drive signal and primary variables waveform of current mode bridge-type photovoltaic converter shown in Fig. 2, is believed according to driving
Number, definition boosting dutycycle：
Define power duty cycle：
In formula, TsFor switch periods.Adjust DbAdjustable low-pressure side voltage UdSize；Adjust DpIt can adjust from low-pressure side
Flow to high-pressure side (DC bus-bar voltage UDC) power.
In one switch periods, photovoltaic converter shown in Fig. 2 has 6 operation modes, is respectively described below.
Switch mode 1 [corresponding diagram 4]：
t0Before moment, only switching tube S2 conductings, boost inductance LdcElectric current iLKeep on the occasion of and increase, buffer inductance LrElectricity
Flow irRemain zero.t0Moment, S2 shut-offs, S1, S4 are simultaneously turned on, electric current iLStart linear decline；Voltage uAB=Ud, rectification two
Pole pipe D1 is begun to turn on, voltage uCD=0.5UDC, electric current irStart from scratch linear rise.
Switch mode 2 [corresponding diagram 5]：
t1At the moment, S4 is turned off, S3 anti-and diode is begun to turn on, voltage uAB=0, electric current irLinear decline, circuit its
Its device state is constant.
Switch mode 3 [corresponding diagram 6]：
t2Moment, electric current irDrop to 0, S3 anti-simultaneously diode, rectifying tube D1 to be turned off, voltage uCD=0, circuit is other
Device state is constant.
Three switch mode next and first three mode are symmetrical, and here is omitted.It should be noted that due to photovoltaic
The fluctuation of cell voltage and low-pressure side voltage UdNeed to adjust, boosting dutycycle DbFluctuated in 0.5 less scope, because
This, electric current irWaveform be not strict symmetrical in half of switch periods, but as long as ensureing S3 and S4 ON time phase
Deng, transformer T just can normal operation without causing iron core that saturation occurs.
Boost inductance Ldc, switching tube S1-S2 form bridge arm, low-pressure side filter capacitor CdBooster converter is constituted, its
Input voltage is photovoltaic cell voltage UPV, its output voltage is converter low-pressure side voltage Ud, boost inductor current iLDesign
Continuous mode (CCM) is operated in, both are at corresponding relation
Buffer inductance electric current irDesign work is in discontinuous mode (DCM), its peak point current
According to t1-t2And t4-t5Period inductance LrVoltage is born, obtains power drop dutycycle
It can thus be concluded that electric current irRise, fall time is to the ratio of switch periods
For the low-pressure side of converter, the power that it absorbs in half of power frequency period is equal with the power discharged, because
This, corresponding voltage side electric current idComprising two compositions, a part is t0-t3The electric current i in stageL, use iLdRepresent, it is corresponding to flow into electricity
Hold Cd；Another part is t0-t1And t3-t4The electric current i in stager, use irdRepresent.
id=ird-iLd (7)
Obtain converter in switch periods according to this relation is to the power of outlet side transfer
It can be seen from (8) formula converter institute transimission power only with power duty cycle DpCorrelation, and with boost dutycycle Db
It is unrelated, therefore coupled relation is not present in control, it is favourable to the dynamic property of converter.
Carrying micro- inverter is functionally equivalent to boost+ bridge-type DC/DC converter+SPWM combining inverters herein,
Equivalent schematic is as shown in Figure 10, and wherein photovoltaic cell current source is in parallel with a resistor equivalent, C12For filter capacitor C1、C2String
Join equivalence value.
Equivalent booster converter transmits power
PLd=DbILUd (9)
Wherein, ILFor electric current iLAverage value in switch periods.According to (8), (9), boosting dutycycle DbControl photovoltaic
The energy that battery conveys to low-pressure side, power duty cycle DpControl input effluent is to the energy of outlet side, and therefore, the present invention is
Current mode bridge-type photovoltaic converter proposes the control device shown in Fig. 1.
Current mode bridge-type photovoltaic converter control device includes three parts：1. part i, exported according to photovoltaic cell
Voltage and electric current, using MPPT maximum power point tracking control algolithm, obtain the reference voltage value U of photovoltaic cellPV*；2. II portion
Point, control photovoltaic cell output voltage stabilization is at maximum power point, and adoption rate integral resonance (PIR) adjuster is real
Now to the low-frequency ripple of input side electric current, wherein the dynamic characteristic of system can be improved comprising feedforward control；3. III part,
Control low-pressure side voltage UdSize, its corresponding a reference value is according to DC bus-bar voltage UDCObtain, wherein k is one adjustable
Coefficient, according to power output, voltage Ud、UDCSize together decide on, ensure electric current irIt is operated in as far as possible close to critical continuous mode shape
State (BCM), to realize relatively low device current stress.
Converter equivalent schematic according to Figure 10, respectively to photovoltaic cell side filter capacitor in front stage converter
CPV, boost inductance Ldc, low-pressure side filter capacitor CdVoltage-current relationship corresponding to foundation, respectively
The mean value model established to (10)-(12) formula in switch periods, and disturbance is introduced, obtain front stage converter
Small-signal model, as shown in appendix A, respectively obtain voltage UPVTo the dutycycle D that boostsbTransmission function GUPV_DbAnd voltage Ud
To the dutycycle D that boostspTransmission function GUd_Dp。
Wherein
Figure 11 positions photovoltaic cell output voltage outer ring, the wherein control block diagram of boost inductor current inner ring, Gv(s)、 Gcb
(s)、Hr(s) it is respectively the transmission function of outer voltage adjuster, current inner loop adjuster and feedback using wave filter, selects
Take Hr(s) cut-off frequency is the 1/4 of switching frequency, then
According to loop characteristics design current iLInner ring adjuster is
Total open-loop gain of inner ring closed loop is after then compensating
Figure 12 gives UPVThe Bode diagram of current inner loop transmission function before and after being compensated in the case of=36V, P=350W, its is steady
Allowance is determined for 66 °, is 10 octaves from double power frequency (100Hz) place with a width of 1020Hz, it is ensured that low-frequency ripple is suppressed
Dynamic property；Due to the introducing of resonant controller, the gain 50.8dB at 100Hz, can effectively ensure that low under stable situation
The suppression of frequency ripple.
The closed loop transfer function, of current inner loop is
Then outer voltage totality open-loop gain is equal to
Design voltage adjuster is
Figure 13 is the Bode diagram of system before and after the compensation of photovoltaic cell outer voltage, it can be seen that voltage loop bandwidth after compensation
30Hz, 100 ° of stability margin, although bandwidth is relatively low, relative to the dynamic property and photovoltaic of photovoltaic cell output voltage
The disturbance step-length of battery MPPT algorithm, design bandwidth are enough to ensure that micro- inverter is stable, quickly realizes tracking target.
Design parameter Bode diagram shown in Figure 12, Figure 13 only for UPV=36V, P=350W situation, it is also necessary to
Micro- inverter under voltage, power is possible to photovoltaic cell can keep stabilization to verify.
In Figure 11, order
Then electric current loop closed loop transfer function, is
Outer voltage closed loop transfer function, is
Root locus diagram under different photovoltaic cell running parameters is drawn according to formula (24), as shown in Figure 14, Figure 15, owned
Characteristic root in the left half side of s planes, then designed voltage parameter can ensure all works of photovoltaic cell with current ring parameter
It is stable in the case of work, it is stronger in relatively low voltage and the stability of system under less power situation.
Low-pressure side filter capacitor CPVEnergy come from the photovoltaic cell of Boost converter input side, pass through isolation
Type bridge converter exports to dc bus side, when input power is more than power output, UPVRise；When input power is less than
During power output, UPVDecline.From formula (8) as can be seen that power output only with power duty cycle DpCorrelation, therefore control can be passed through
D processedpRealize voltage UPVStabilization.To realize efficiency optimization, U can adjustPVA reference value and DC bus-bar voltage into (1/k) (its
Middle k>1/2n) times relation.To ensure that device current stress is optimal, k values should be one related to photovoltaic cell running parameter
Function, it is limited to this paper lengths and does not discuss, set k=0.18 here.Figure 16 is photovoltaic cell low-pressure side voltage control block diagram,
Due to the dutycycle D that boostsbWith voltage UDCDisturbance the stability of closed loop is not influenceed, therefore the design of controller only considers
D in forward pathpThe influence of disturbance.Designing low-pressure side voltage controller is
In PIR adjusters, (80Hz) sets a zero point to ensure the gain at double power frequency at less than 100Hz
It is unlikely to too small, spike when (1.2kHz) sets a limit to suppress underloading at the half of resonance spikes frequency.From figure
The Bode diagram of adjuster shown in 17 can be seen that due to adding resonant controller at double power frequency, at all 100Hz
Total open-loop gain reach 36.7dB；The effective bandwidth of this outer ring reaches 1.25kHz, and the two features can effectively ensure that low-pressure side
Voltage UdIn low-frequency ripple effectively tracked, so as to DC bus-bar voltage UDCRealization is effectively matched.
When Figure 18, Figure 19 are that photovoltaic cell operating point changes, the root locus diagram of low-pressure side voltage closed-loop system, it can see
Go out, the Principal eigenvalue position of system is basically unchanged on the basis of designed voltage regulator, that is photovoltaic cell operating point
Change does not influence substantially on the stability of system.
In summary, the present invention, which is directed in a kind of current mode bridge-type photovoltaic converter, introduces a kind of new double dutycycle controls
Device processed, stable duty ratio photovoltaic cell output voltage and the low frequency in photovoltaic cell output current is inhibited by boosting
Ripple component；Realize that photovoltaic converter low-pressure side voltage matches with DC bus-bar voltage by power duty cycle, so as to optimize
The current stress of switching device in converter so that conversion efficiency greatly improves；In addition set by rational regulator parameter
Meter causes converter to have higher dynamic characteristic.Therefore, the current mode bridge-type photovoltaic converter that the present invention controls has conversion
The advantages that efficiency high, dynamic characteristic are good, low-frequency ripple is rationally suppressed.
Claims (5)
- A kind of 1. double duty cycle control arrangements of current mode bridge-type photovoltaic converter, it is characterised in that：Including signal detection link, MPPT maximum power point tracking module, photovoltaic cell voltage controller, low-pressure side voltage controller and signal modulator；Wherein photovoltaic Cell voltage controller includes the first subtracter, proportional and integral controller, the second subtracter, the regulation of the first proportional integration resonance Device, adder, low-pressure side voltage controller include proportional component, the 3rd subtracter, the second proportional integration resonant regulator and Signal modulator.
- 2. a kind of signal detection link as claimed in claim 1 includes 5 output ends, respectively the first output end is to the 5th defeated Go out end, two inputs of MPPT maximum power point tracking module as claimed in claim 1 connect the of signal detection link respectively One output end and the second output end；Positive input terminal, the negative input end of first subtracter connect MPPT maximum power point tracking module respectively Output end and signal detection link the second output end；The input of proportional and integral controller connects the output of the first subtracter End；Positive input terminal, the negative input end of second subtracter connect the output end and signal detection link of proportional and integral controller respectively The 3rd output end；The input of first proportional integration resonant regulator connects the output end of the second subtracter；The two of adder Individual positive input terminal is connected respectively to the output end of MPPT maximum power point tracking module and the output of the first proportional integration resonant regulator End；The input of proportional component is connected to the 4th output end of signal detection link；The positive input terminal of 3rd subtracter is defeated with bearing Enter end and connect the output end of proportional component and the 5th output end of signal detection link respectively；Second proportional integration resonant regulator Input connect the 3rd subtracter output end；The first input end of signal modulator is connected addition respectively with the second input The output end of device and the output end of the second proportional integration resonant regulator, the first output end and the second output end of signal modulator The drive signal of the first bridge arm switching tube and the second bridge arm switching tube respectively as photovoltaic bridge converter.
- 3. a kind of photovoltaic cell voltage controller as claimed in claim 1, it is characterised in that inner loop feedback amount is and photovoltaic electric The directly related boost inductor current of pond output current, and adoption rate integral resonance adjuster, resonant frequency is set to be equal to two Mains frequency again so that boost inductor current accurately tracks a reference value, is not influenceed by converter outlet side different loads； Feedback quantity of the photovoltaic cell voltage as outer shroud, after the double power-frequency ripple current of current inner loop is inhibited, photovoltaic cell Power output is a stationary value, therefore it is a stable direct current letter to control in the proportional and integral controller output signal of photovoltaic voltage Number；Pass through the control of above-mentioned outer voltage, current inner loop so that in photovoltaic cell voltage stabilization and photovoltaic cell output current Low-frequency ripple composition be effectively suppressed.
- 4. a kind of low-pressure side voltage controller as claimed in claim 1, it is characterised in that its voltage reference value and dc bus Voltage is in certain proportionate relationship, so as to optimize the current stress of switching tube in converter；Adoption rate integral resonance is adjusted After saving device, great open-loop gain is obtained at twice of mains frequency, ensure that low-pressure side voltage is same with DC bus-bar voltage Proportional change is walked, further reduces the current stress of switching tube in converter.
- 5. a kind of signal modulator as claimed in claim 1, its input signal is two dutycycles, modulates bridge-type conversion respectively Two switching tubes in two switching tubes and second bridge arm in first bridge arm of device, improve the control dimension of converter Number, improve the control efficiency of converter.
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