CN204334377U  Based on the miniature photovoltaic DCtoAC converter of flyback transformer primary current feedback  Google Patents
Based on the miniature photovoltaic DCtoAC converter of flyback transformer primary current feedback Download PDFInfo
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 CN204334377U CN204334377U CN201420733527.0U CN201420733527U CN204334377U CN 204334377 U CN204334377 U CN 204334377U CN 201420733527 U CN201420733527 U CN 201420733527U CN 204334377 U CN204334377 U CN 204334377U
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 flyback transformer
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 Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSSSECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSSREFERENCE 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

 Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSSSECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSSREFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
 Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
 Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
 Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
 Y02E40/40—Arrangements for reducing harmonics
Abstract
Based on a miniature photovoltaic DCtoAC converter for flyback transformer primary current feedback, decoupling capacitor C
_{pv}in parallel with photovoltaic cell PV, one end of photovoltaic cell PV is connected with one end, former limit of flyback transformer TR, the former limit other end of flyback transformer TR and prime power switch tube S
_{m}source electrode connect, S
_{m}drain electrode be connected with the other end of photovoltaic cell PV, S
_{m}grid be connected with PWM generator, S
_{m}drain electrode be connected with filter, filter is connected with current comparator, and the output of current comparator is connected with the input of PI resonant controller, and the output of PI resonant controller is connected with PWM generator; One end of TR secondary is connected with the positive pole of secondary output diode D, the other end of the negative pole of secondary output diode D, the secondary of TR respectively with output capacitance C
_{o}, full bridge inverter is connected with filter circuit.The utility model effectively eliminates the harmonic wave of gridconnected current zero crossing, improves the grid connection efficiency of inverter and gridconnected quality.
Description
Technical field
The utility model belongs to new forms of energy electric control field, especially a kind of photovoltaic combining inverter based on flyback transformer primary current feedback.
Background technology
Gridconnected current control technology mainly contains traditional control technology and the control technology based on modern control theory.Wherein traditional gridconnected current control technology mainly contains PI control, Hysteresis control, Repetitive controller, predictivecurrent control, monocyclic control method etc.And mainly contain fuzzy control, Sliding mode variable structure control, adaptive control etc. based on the gridconnected current control technology of modern control theory.For existing Miniature inverter product, due to will cost factor be considered, substantially be all adopt have algorithm simple, realize that cost is low, the PI controller of good stability, but PI controls to there are two problems: be difficult to realize the DAZ gene of reference sine wave and poor antijamming capability.Therefore propose ratio resonance (PR) to control, it can produce enough large gain at fixed frequency place, realizes DAZ gene.But due to the restriction of analogue system component parameter precision and digital system precision, ratio resonance (PR) controller not easily realizes, and when mains frequency produces skew, the harmonic wave that just cannot effectively suppress electrical network to produce.Therefore, on the basis that ratio resonance controls, propose a kind of accurate ratio resonance (PR) controller being easy to realize, both the highgain of ratio resonance (PR) controller can have been kept, the impact of mains frequency skew on inverter output current can also be effectively reduced simultaneously, but accurate ratio resonance resonant controller can not suppress the DC component of prime input current, then this patent proposes PI resonance control method.
Photovoltaic DCtoAC converter has three kinds of mode of operations, discontinuous conduct mode (DCM), electric current critical continuous conduction mode (BCM), continuous current mode (CCM).During model study at present for photovoltaic DCtoAC converter, normally allow inverter work in one mode.Due under singlemode time, when input power is lower, grid connection efficiency is lower, and the harmonic wave at zero passage place can be larger.
Summary of the invention
In order to overcome existing photovoltaic DCtoAC converter singlemode mode when input power is lower, the problem that grid connection efficiency is lower, the harmonic wave at zero passage place can be larger, the utility model provides a kind of and effectively improves the grid connection efficiency of inverter, the miniature photovoltaic DCtoAC converter based on flyback transformer primary current feedback of reduction gridconnected current harmonic wave.
The utility model solves the technical scheme that its technical problem adopts:
Based on a miniature photovoltaic DCtoAC converter for flyback transformer primary current feedback, this inverter adopts the topological structure of inverseexcitation type conversion, and described photovoltaic DCtoAC converter comprises photovoltaic cell PV, decoupling capacitor C
_{pv}, prime power switch tube S
_{m}, flyback transformer TR, secondary output diode D and output capacitance C
_{o}, described decoupling capacitor C
_{pv}in parallel with photovoltaic cell PV, one end of described photovoltaic cell PV is connected with one end, former limit of flyback transformer TR, the former limit other end of described flyback transformer TR and described prime power switch tube S
_{m}source electrode connect, described prime power switch tube S
_{m}drain electrode be connected with the other end of described photovoltaic cell PV, described prime power switch tube S
_{m}grid be connected with PWM generator, described prime power switch tube S
_{m}drain electrode be connected with filter, described filter with for comparing current i and reference current i
_{pri}difference DELTA i whether be less than the precision ε of current deviation current comparator connect, the output of described current comparator is connected with the input of PI resonant controller, and the output of described PI resonant controller is connected with described PWM generator; One end of the secondary of described flyback transformer TR is connected with the positive pole of described secondary output diode D, the other end of the negative pole of described secondary output diode D, the secondary of described flyback transformer TR respectively with output capacitance C
_{o}two ends connect, described output capacitance C
_{o}two ends be connected with full bridge inverter, the output of described full bridge inverter is connected with filter circuit, and the output of described filter circuit is the output of inverter.
Further, described reference current is according to gridconnected voltage V
_{grid}, photovoltaic input voltage U
_{m}, photovoltaic input current I
_{m}calculation of parameter draws, i.e. reference current
Further again, in described step (5), by by PI and quasi resonant control is in series is used for the PI resonance control and compensation device that flyback combining inverter realizes gridconnected output, its transfer function G (s) is:
Wherein, G
_{pi}s () represents the transfer function of PI controller, G
_{c}s () represents the transfer function of quasi resonant control, K
_{p}be the gain of resonant controller, Q is bandwidth factor, and ω is resonance frequency, K
_{r}for resonance coefficient.
Technical conceive of the present utility model is: the control mode adopting two kinds of mode of operations to switch, and effectively can improve the grid connection efficiency of inverter, reduces the harmonic wave of gridconnected current.
The beneficial effects of the utility model are mainly manifested in: can solve the problem of the gridconnected output of Miniature inverter in the harmonic distortion at zero passage place, the impact of mains frequency skew on inverter output current can be effectively reduced simultaneously, suppress the DC component of prime input current, improve the grid connection efficiency of inverter, reduce the THD value of gridconnected current.
Accompanying drawing explanation
Fig. 1 is the miniature photovoltaic DCtoAC converter fundamental diagram based on flyback transformer primary current feedback of the present utility model.
Fig. 2 is the program control flow chart based on PI resonance control algolithm of the present utility model.
Fig. 3 is the operating current figure of miniature photovoltaic DCtoAC converter of the present utility model under continuous current mode (CCM).
Fig. 4 is the operating current figure of miniature photovoltaic DCtoAC converter of the present utility model under discontinuous conduct mode (DCM).
Fig. 5 is the bode figure of PI resonant controller of the present utility model.
Fig. 6 is the bode figure of resonant controller.
Embodiment
Below in conjunction with accompanying drawing, the utility model is further described.
With reference to Fig. 1 ~ Fig. 6, a kind of miniature photovoltaic DCtoAC converter based on flyback transformer primary current feedback, this inverter adopts the topological structure of inverseexcitation type conversion, and described photovoltaic DCtoAC converter comprises photovoltaic cell PV, decoupling capacitor C
_{pv}, prime power switch tube S
_{m}, flyback transformer TR, secondary output diode D and output capacitance C
_{o}, described decoupling capacitor C
_{pv}in parallel with photovoltaic cell PV, one end of described photovoltaic cell PV is connected with one end, former limit of flyback transformer TR, the former limit other end of described flyback transformer TR and described prime power switch tube S
_{m}source electrode connect, described prime power switch tube S
_{m}drain electrode be connected with the other end of described photovoltaic cell PV, described prime power switch tube S
_{m}grid be connected with PWM generator, described prime power switch tube S
_{m}drain electrode be connected with filter, described filter with for comparing current i and reference current i
_{pri}difference DELTA i whether be less than the precision ε of current deviation current comparator connect, the output of described current comparator is connected with the input of PI resonant controller, and the output of described PI resonant controller is connected with described PWM generator; One end of the secondary of described flyback transformer TR is connected with the positive pole of described secondary output diode D, the other end of the negative pole of described secondary output diode D, the secondary of described flyback transformer TR respectively with output capacitance C
_{o}two ends connect, described output capacitance C
_{o}two ends be connected with full bridge inverter, the output of described full bridge inverter is connected with filter circuit, and the output of described filter circuit is the output of inverter.
Further, described reference current is according to gridconnected voltage V
_{grid}, photovoltaic input voltage U
_{m}, photovoltaic input current I
_{m}calculation of parameter draws, i.e. reference current
Further again, in described step (5), by by PI and quasi resonant control is in series is used for the PI resonance control and compensation device that flyback combining inverter realizes gridconnected output, its transfer function G (s) is:
Wherein, G
_{pi}s () represents the transfer function of PI controller, G
_{c}s () represents the transfer function of quasi resonant control, K
_{p}be the gain of resonant controller, Q is bandwidth factor, and ω is resonance frequency, K
_{r}for resonance coefficient.
Output based on the photovoltaic miniature gridconnected inverter of flyback transformer primary current feedback is connected with electrical network.
Basic functional principle based on the photovoltaic miniature gridconnected inverter of flyback transformer primary current feedback is that the direct current that prime photovoltaic cell exports generates halfsinusoid after switching tube Sm modulates, then the fullbridge circuit be made up of 4 IGBT carries out line commutation, then flows to electrical network after device filtering after filtering and carries out gridconnected.And the general principle of control system first detects prime flyback transformer former limit input current i
_{in}, after filtering, obtain current i and reference current i
_{pri}relatively, Δ i can be obtained, then through the adjustment of PI resonance, eventually pass PWM wave producer, pwm signal is sent to mos pipe S
_{m}end.
In the present embodiment, the photovoltaic combining inverter PI resonance control method that continuous current mode and discontinuous conduct mode switch, ratedetermining steps is as follows:
Detect photovoltaic input voltage V
_{pv}, setting reference voltage V
_{st}for 30V, photovoltaic input voltage V
_{pv}with reference voltage V
_{st}compare, judge photovoltaic input voltage V
_{pv}whether higher than 30V, if higher than 30V, then controller can normally work, otherwise treats machine testing, until photovoltaic input voltage V
_{pv}higher than 30V.
Detect inverter output voltage V
_{o}, and compare V
_{o}with boundary voltage V
_{bo}size, wherein boundary voltage V
_{bo}for critical voltage when CCM pattern and DCM pattern switch.
f is switching frequency, and n is turn ratio, L
_{m}be transformer inductance, R is electrical network equiva lent impedance, V
_{pv}it is photovoltaic input voltage.
When  V
_{o} <V
_{bo}time, in dcm mode, corresponding duty ratio is D in miniature photovoltaic DCtoAC converter work
_{dCM}, when  V
_{o}>=V
_{bo}time, in ccm mode, corresponding duty ratio is D in miniature photovoltaic DCtoAC converter work
_{cCM}.
Use Statespace Averaging Principle can solve the duty ratio steady state solution obtained under CCM pattern and DCM pattern, be shown below
Wherein V
_{o}the gridconnected output voltage of Miniature inverter, L
_{m}transformer inductance, I
_{in}be the effective value of photovoltaic input current, ω is the angular frequency of gridconnected voltage.
Reference current is according to gridconnected voltage V
_{grid}, photovoltaic input voltage U
_{m}, photovoltaic input current I
_{m}draw etc. calculation of parameter, reference current
carry out filtering process by RC filter circuit to flyback transformer primary current, the transfer function of filter circuit is
primary current i after detecting after filtering, by filtered primary current i and reference current i
_{pri}compare, then can obtain Δ i=ii
_{pri}.Adopt PI resonant controller to carry out computing to Δ i, calculate ac small signal duty ratio d.I.e. d=Δ i*G (s).
By superimposed for ac small signal duty ratio d and stable state duty ratio D, obtain the duty ratio needed for drive circuit
namely
controller is according to duty ratio
send corresponding PWM ripple and control prime mos pipe S
_{m}action, thus the former limit input current i changing flyback transformer
_{in}value, control circuit is as shown in Figure 1
According to i and i
_{pri}difference DELTA i whether be less than ε to start PI resonant controller.If Δ i=ii
_{pri}> ε, then illustrate total duty ratio
undesirable, then need to return the primary current i detecting flyback transformer again, and adjust total duty ratio
.If Δ i≤ε, the primary current of flyback transformer within the range of permission, then can make miniature photovoltaic inverter output current reach gridconnected requirement.
When miniature photovoltaic DCtoAC converter work in ccm mode time, as shown in Figure 3, when miniature photovoltaic DCtoAC converter is operated in dcm mode, operating current is as shown in Figure 4 for operating current.
In the utility model, the concrete steps of PI resonance control design case are as follows:
The controller that engineering is extensively used is PI controller, and it has two parameters to determine, proportionality coefficient and integral coefficient, and it controls transfer function:
In formula, k
_{p}for proportionality coefficient, k
_{i}for integral coefficient.
Wherein, the effect of proportion adjustment is the deviation of reaction system in proportion, and system is once occur deviation, and proportion adjustment produces regulating action immediately to reduce deviation.Proportional action is large, can accelerate to regulate, and reduces error, but excessive ratio, the stability of system is declined, even causes the instability of system.Autocatalytic reset action makes system eliminate steadystate error, improves without margin.Because there is error, integral adjustment just carries out, until by error concealment, integral adjustment stops.The power of integral action depends on the constant Ti of the time of integration, and Ti is less, and the effect of integration is stronger.Otherwise Ti is larger, and then integral action is more weak, add integral adjustment and the stability of a system can be made to decline, dynamic response is slackoff.Integral action and proportional action are combined, and just constitute PI controller.
Because the utility model is discussed by zero point of transfer function and gain, therefore, need above formula to be converted into formula form:
${G}_{\mathrm{pi}}\left(s\right)={k}_{p}+{k}_{i}\frac{1}{s}=K\frac{\frac{1}{{S}_{c}}s+1}{s}$
In formula, K=k
_{i}for the gain of PI controller, S
_{z}=k
_{p}/ k
_{i}for the zero point of PI controller.
The basis that PI controls is introduced a second order concussion link again can function to achieve the objective sin
^{2}the DAZ gene of (ω t).But there will be the problems such as the DAZ gene that is difficult to realize reference sine wave and poor antijamming capability owing to introducing second order concussion link, therefore, need to improve, by 2 ω second order concussion link
^{2}/ (s
^{2}+ 4 ω
^{2}) be converted to quasi resonant control:
In formula, K
_{r}for the voltage amplification factor at resonance frequency omega place, K
_{p}it is the gain of resonant controller; Q is bandwidth factor, determines the bandwidth of resonant controller.
So far, by by PI and quasi resonant control is in series is used for the PI resonance control and compensation device that flyback combining inverter realizes gridconnected output, its transfer function is:
Four parameter K of quasi resonant control in formula
_{p}, bandwidth factor Q, resonance frequency omega, resonance coefficient K
_{r}impact be amplitudefrequency characteristic and the phasefrequency characteristic at 100rad/s resonance frequency place, be specially: K
_{p}relevant with steadystate behaviour and interference free performance, K
_{p}larger, steadystate gain is larger, and resonance peak is less, and cutoff frequency is higher; Bandwidth factor Q determines resonance frequency omega place bandwidth, and Q is larger, and bandwidth is larger; Resonance coefficient K
_{r}determine the gain of resonance frequency omega place, K
_{r}larger, resonance spikes is larger, and Phase margin is less.Fig. 5 is the bode figure of PI resonant controller, Fig. 6 is that the bode of resonant controller schemes.As can be known from Fig. 5, the magnitude margin bandwidth of PI resonant controller at 100rad/s place becomes large, and the change of phase margin is relatively slow; As can be known from Fig. 6, resonant controller bandwidth in 100rad/s place magnitude margin is narrow, and phase margin change is violent.Therefore PI resonance algorithm is compared resonance control algolithm and is more prone to realize, and becomes large due to PI resonant controller bandwidth range, when mains frequency produces skew, also can realize the suppression to mains by harmonics, reduce the THD value of gridconnected current.
Claims (1)
1. based on a miniature photovoltaic DCtoAC converter for flyback transformer primary current feedback, it is characterized in that: this inverter adopts the topological structure of inverseexcitation type conversion, and described photovoltaic DCtoAC converter comprises photovoltaic cell PV, decoupling capacitor Cpv, prime power switch tube S
_{m}, flyback transformer TR, secondary output diode D and output capacitance Co, described decoupling capacitor Cpv is in parallel with photovoltaic cell PV, one end of described photovoltaic cell PV is connected with one end, former limit of flyback transformer TR, the former limit other end of described flyback transformer TR and described prime power switch tube S
_{m}source electrode connect, described prime power switch tube S
_{m}drain electrode be connected with the other end of described photovoltaic cell PV, described prime power switch tube S
_{m}grid be connected with PWM generator, the drain electrode of described prime power switch tube S m is connected with filter, described filter with for comparing electric current
iwith reference current
i _{ pri }difference
Δ iwhether be less than the precision of current deviation
εcurrent comparator connect, the output of described current comparator is connected with the input of PI resonant controller, and the output of described PI resonant controller is connected with described PWM generator; One end of the secondary of described flyback transformer TR is connected with the positive pole of described secondary output diode D, the other end of the negative pole of described secondary output diode D, the secondary of described flyback transformer TR is connected with the two ends of output capacitance Co respectively, the two ends of described output capacitance Co are connected with full bridge inverter, the output of described full bridge inverter is connected with filter circuit, and the output of described filter circuit is the output of inverter.
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Cited By (3)
Publication number  Priority date  Publication date  Assignee  Title 

CN104485833A (en) *  20141127  20150401  浙江工业大学  Miniature photovoltaic inverter based on primary side current feedback of flyback transformer 
CN105187005A (en) *  20150605  20151223  上海大学  Miniature photovoltaic inverter with zero input secondary ripple current content 
CN107800377A (en) *  20160831  20180313  无锡昊阳新能源科技有限公司  Photovoltaic generation magnetic saturation transformation inverter 

2014
 20141127 CN CN201420733527.0U patent/CN204334377U/en not_active Expired  Fee Related
Cited By (3)
Publication number  Priority date  Publication date  Assignee  Title 

CN104485833A (en) *  20141127  20150401  浙江工业大学  Miniature photovoltaic inverter based on primary side current feedback of flyback transformer 
CN105187005A (en) *  20150605  20151223  上海大学  Miniature photovoltaic inverter with zero input secondary ripple current content 
CN107800377A (en) *  20160831  20180313  无锡昊阳新能源科技有限公司  Photovoltaic generation magnetic saturation transformation inverter 
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Granted publication date: 20150513 Termination date: 20171127 

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