CN201869102U - DC/DC changer of photovoltaic high-frequency isolating boosting soft switch - Google Patents

DC/DC changer of photovoltaic high-frequency isolating boosting soft switch Download PDF

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CN201869102U
CN201869102U CN2010206447849U CN201020644784U CN201869102U CN 201869102 U CN201869102 U CN 201869102U CN 2010206447849 U CN2010206447849 U CN 2010206447849U CN 201020644784 U CN201020644784 U CN 201020644784U CN 201869102 U CN201869102 U CN 201869102U
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current
converter
voltage
circuit
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杜春水
张承慧
陈阿莲
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Shandong University
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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
    • 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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Abstract

The utility model relates to a DC/DC (direct current/direct current) changer of a photovoltaic high-frequency isolating boosting soft switch, which solves the problems that the current changing of an advancing arm is difficult under no-load or light-load conditions and the efficiency is reduced under full-load condition, improves the efficiency and realizes soft switches of the changer in a full-power range. The DC/DC changer comprises a high-frequency transformer, the original side of which is provided with a phase shift PWM control changer. Three secondary sides are arranged on the high-frequency transformer, two of the secondary sides are connected by a bridge type diode rectifying circuit in series so as to output high voltage, output ends of the two secondary sides are connected with the output voltage and a current sampling circuit, and the output voltage and the current sampling circuit are connected with a controller; the third secondary side is connected with a current changing inductor and a switch by a step-down winding. The original side of the transformer is provided with a blocking-up capacitor Cb and an inductor LS that are connected in series. Output filter inductors Lf1 and Lf2 are coupled inductors and commonly use one magnetic core; and output ends Df1-R1-Cf1 and Df2-R2-Cf2 form a cross clamping buffer circuit. Asymmetrical phase shift PWM controllers control the power switching devices VT1-VT4 and a switch K0.

Description

The photovoltaic high-frequency isolation soft switch DC/DC converter that boosts
Technical field
The utility model relates to a kind of photovoltaic high-frequency isolation soft switch DC/DC converter that boosts.
Background technology
At present, parallel network power generation has become the main development trend of photovoltaic utilization and focus (the Carrasco J M of correlation technique research, Franquelo L G, Bialasiewicz J T, et al.Power-electronics systems for the grid integration of renewable energy sources:a survey[J] .IEEE Transactions on Industrial Electronics, 2006,53 (4): 1002-1016.).Because the output of photovoltaic battery array maximum power is subjected to relatively more serious (the Trishan Esram of the influence of factors such as intensity of illumination, cell panel temperature, each series component performance parameter, Patrick L Chapman.Comparison of photovoltaic array maximum power point tracking techniques[J] .IEEE Transactions on Energy Conversion, 2007,22 (2): 439-449.), usually reduce cell panel series connection quantity, to reduce the withstand voltage of photovoltaic generating system and device for power switching as far as possible.For satisfying the control of photovoltaic array MPPT maximum power point tracking and the voltage requirements that is incorporated into the power networks, combining inverter often has the link of boosting.
Non-isolation type photovoltaic combining inverter leakage current to personal safety have bigger threat (Zhang Xing, Sun Longlin are permitted quite, etc. common mode current suppresses research [J] in the single-phase non-isolation type photovoltaic parallel in system. solar energy journal, 2009,36 (9): 1202-1207; Xiao Huafeng, Xie Shaojun. be used for grid-connected staggered two-tube Buck-Boost converter [J]. Proceedings of the CSEE, 2010,30 (21): 7-12), the photovoltaic combining inverter of high and medium power grade requires to have transformer isolation.The transformer isolation type can be divided into the high frequency transformer isolation again and Industrial Frequency Transformer is isolated two kinds.Not enough (Zhang Xing such as that the high frequency transformer isolation type grid-connected inverter has overcome that power frequency boosts that isolating transformer exists is bulky, consumptive material serious, cost an arm and a leg, Sun Longlin, permitted quite, Deng. common mode current suppresses research [J] in the single-phase non-isolation type photovoltaic parallel in system. solar energy journal, 2009,36 (9): 1202-1207.), in single-phase low-voltage middle low power photovoltaic generating system, use more.In recent years, soft switch technique (the T.T.Song that various full-bridge circuit topologys combine with the phase-shift PWM controlled strategy, N.C.Huang, A.Ioinovici.A family ofzero-voltage and zero-current-switching (ZVZCS) three-level DC-DC converter the secondary-assisted regenerative passive snubber[J] .IEEE Transactions on circuits and systems, 2005,52 (11): 2473-2481; Jiang Xuesong, Wen Xuhui, Xu Haiping. the fuel cell electric vehicle research [J] of isolating the Boost full-bridge converter. Nanjing Aero-Space University's journal, 2006,38 (1): 64-69., Ruan Xinbo, tight Rangoon. the soft switch technique [M] of pulse-width modulation DC/DC full-bridge converter. Beijing: Science Press, 2001.; Li Chuanwen. the boost development [D] of full-bridge soft-switching DC-DC converter of photovoltaic, Jinan: Shandong University, 2008.; Poplar is logical, Huang Yanling, Zhang Guangxian. digitized contravariant arc welding power source [J]. electric welding machine, 2009,39 (2): 11-17.Yang Tong, Huang Yanling, Zhang Guang xian.Digitalized arc welding power[J] .Electric Welding Machine, 2009,39 (2): 11-17.; Zhao Zhenmin, Yue Yuntao. a kind of full-bridge soft-switching DC/DC converter [J] based on UC3879 control. power electronic technology, 2005,39 (3): 107-110), significantly improve the efficient and the power density of DC/DC converter, be widely used in high-power low-voltage output field.
For satisfying high-power isolated form three-phase photovoltaic grid-connected inverting device DC side high input voltage (generally will reach more than the 650V) requirement, usually need boost by high frequency transformer, yet the secondary side voltage peak of high step-up ratio is very harsh to the rectifier diode requirement of withstand voltage.For this reason, document [Li Chuanwen. the boost development [D] of full-bridge soft-switching DC-DC converter of photovoltaic, Jinan: Shandong University, 2008] provided the circuit topology of a kind of secondary side series connection rectification, effectively reduced requirement of withstand voltage, but that its CDD passive clamp circuit causes the transformer primary current to impact is big fast diode, output current is interrupted under underloading or no-load condition, the leading arm electric capacity change of current is incomplete, and it directly discharges fragile device for power switching by device for power switching in parallel with it.And document [poplar is logical, Huang Yanling, Zhang Guangxian. digitized contravariant arc welding power source [J]. and electric welding machine, 2009,39 (2): 11-17.] provided a kind of step-down output circuit topology of auxiliary induction, all participate in the change of current and this change of current inductance is unloaded still fully loaded.Its high-frequency current amplitude can reach 14A during the work of being fully loaded with.Bring serious system loss thus, it comprises the on-state loss and the line loss of the former limit of magnetic hysteresis loss, the transformer power switch pipe of coil copper loss, magnetic core.These losses have not only reduced system effectiveness, have also improved the device for power switching power grade, have increased cost.Simultaneously, the control precision of traditional phase-shift PWM controlled special chip (as UC3875, UC3879 etc.) and the not high deficiency of flexibility, (Zhao Zhenmin, Yue Yuntao. a kind of full-bridge soft-switching DC/DC converter [J] based on UC3879 control. power electronic technology, 2005,39 (3): 107-110.).
The utility model content
The purpose of this utility model is exactly for satisfying the demand of three-phase photovoltaic grid-connected inverting device high input voltage, overcome its power frequency serious deficiency of isolating transformer consumptive material of boosting, a kind of photovoltaic high-frequency isolation soft switch DC/DC converter that boosts has been proposed, its high frequency transformer has three secondary, and wherein the rectification that is used to connect of two windings that boost realizes high voltage output; The step-down winding that another connects change of current inductance and switch has solved the problem that efficient reduces under leading arm change of current difficulty, the full load conditions under zero load or the underloading situation, has significantly improved the efficient of converter.
For achieving the above object, the utility model adopts following technical scheme:
A kind of photovoltaic high-frequency isolation soft switch DC/DC converter that boosts, it comprises high frequency transformer, the phase-shift PWM controlled converter, described high frequency transformer is provided with three secondary, wherein two secondary adopt full-bridge rectification and series connection to improve output voltage, their output and output voltage, current sampling circuit connects, output voltage, current sampling circuit is connected with controller, the phase-shift PWM output of controller is connected with isolated drive circuit, isolated drive circuit then is connected with the phase-shift PWM controlled converter on former limit, and the phase-shift PWM controlled converter on former limit is provided with the blocking capacitor C of series connection bWith pulsactor L SThe 3rd secondary is the step-down winding, and it is connected with change of current inductance and switch.
Described phase-shift PWM controlled converter is the full-bridge circuit in parallel with photovoltaic cell, and it is by the leading arm power switch pipe VT of series connection 1, VT 2Lagging leg power switch pipe VT with series connection 3, VT 4Compose in parallel; Wherein, leading arm power switch pipe VT 1, VT 2Respectively with separately inverse parallel diode D T1, D T2In parallel; Lagging leg power switch pipe VT 3, VT 4With inverse parallel diode D separately T3, D T4Parallel connection, the blocking capacitor C of series connection bWith pulsactor L SBe arranged on the leading arm power switch pipe VT of series connection 1, VT 2Lagging leg power switch pipe VT with series connection 3, VT 4Between; Leading arm power switch pipe VT 1, VT 2With lagging leg power switch pipe VT 3, VT 4Drive by isolated drive circuit.
A full bridge rectifier is by fast recovery diode D in the described secondary 1-D 4Form the diode D of the output of this full-bridge circuit serial connection in parallel F1, capacitor C F1, an output is again through filter inductance L then F1Another output and the output filter capacitor C of back and this full-bridge circuit O1In parallel;
Second full bridge rectifier is by fast recovery diode D 5-D 8Form the diode D of the output of this rectification circuit serial connection in parallel F2, capacitor C F2, an output is again through filter inductance L F2Another output and the output filter capacitor C of back and this rectification circuit O2In parallel.
Filter inductance L F1With filter inductance L F2Be the shared magnetic core of coupling inductance; Output D F1-R 1-C F1With D F2-R 2-C F2Constitute intersection clamp buffer circuit.
Described controller is the TMS320F2812 chip.
Described controller also is connected with overheating protection circuit with under-voltage, the overvoltage of input, overcurrent.
The boost control method of soft switch DC/DC converter of a kind of photovoltaic high-frequency isolation, it adopts asymmetric phase-shift PWM controlled scheme, and it comprises full-bridge type work and two kinds of situations of semibridge system work.
Full-bridge type working control signal characteristics are shown in Fig. 2 a: opening of (1) leading arm and lagging leg switching tube is constantly identical, and turn-offs different constantly; (2) leading arm control signal pulse-width modulation, and the lagging leg control signal keeps maximum pulse width constant.This kind mode of operation can satisfy load internal power regulatory demand on a large scale.And the semibridge system working control signal is shown in Fig. 2 b, and leading arm has turn-offed, and leading arm electric capacity is formed the semibridge system structure with the lagging leg switching tube, and only lagging leg control signal pulse-width modulation this moment is to realize the adjusting of underloading micropower.
Described phase-shift PWM generates method step:
(1) in normal output power range, makes the value n of the register CMPR2 of controller self 2Equal period register numerical value n 0, i.e. n 2=n 0At this moment, lagging leg two complementary conductings of power device up and down; Change the value n of the register CMPR1 of controller self 1, n 1≤ n 0, realize 0 °～180 ° variations of leading arm conducting pulsewidth, thereby realize the power output adjusting; Work as n 1=n 0The Shi Chaoqian arm turn-offs; Work as n 1=0 o'clock, 180 ° of two each conductings of power device up and down of leading arm, it is maximum that power output reaches;
(2) power output increases process by zero load or underloading: at first, the value of the comparand register CMPR1 of shilling controller self equals the value of period register, i.e. n 1=n 0Leading arm turn-offs the value n of control lag arm register 2From n 0Reduce gradually, lagging leg conducting pulsewidth increases gradually; Value n as register CMPR2 2Equal at 0 o'clock, it is maximum that the lagging leg pulsewidth reaches; Along with the increase of power output, reduce the value n of CMPR1 gradually 1, leading arm pulsewidth broadens gradually, up to n 1=0, reach maximum conducting pulsewidth;
(3) power output reduces process to zero load, comparand register numerical value change and process (2) changing inversely by fully loaded or heavy duty; Increase the value n of CMPR1 earlier 1, work as n 1=n 0After increase the value n of CMPR2 again 2Up to n 2=n 0, this moment, all power devices turn-offed fully.
The beneficial effects of the utility model are: proposed a kind of modified model full-bridge soft-switching DC/DC converter, its high frequency transformer has three secondary, and wherein the rectification that is used to connect of two windings that boost realizes high voltage output.Another step-down winding connects change of current inductance and K switch 0: under the interrupted light duty of output current, K 0Closure, change of current inductance provide reactive current to realize the soft switch of leading arm; When output current consecutive hours, K switch 0Disconnect, reduced system's change of current, realized the soft switch of total power scope inner conversion device, overcome the Industrial Frequency Transformer isolation boosting and brought deficiencies such as consumptive material is many, volume big, heaviness, significantly improved transducer effciency.
Be control precision and the not high deficiency of flexibility that overcomes traditional phase-shift PWM controlled special chip (as UC3875, UC3879 etc.) [11]Realize high frequencyization, the digitlization of converter, designed full bridge phase shift PWM numerical control system, simplified peripheral circuit, improved system reliability based on TMS320F2812.
By labor the operation principle of asymmetric phase-shift PWM controlled situation downconverter, provided the production method of concrete pwm waveform, realized the control of full-load range converter digital soft switch.
High efficiency, reliable, have good power output regulating power.
This converter not only is used for grid-connected photovoltaic system, can also be used for the DC boosting occasion of fuel cell, small-size wind power-generating, accumulator of electric car power supply and feedback type electronic load.
Description of drawings
Fig. 1 is the utility model system construction drawing;
Fig. 1 a is the tap winding structural representation on the former limit of transformer;
Fig. 1 b is the tap winding structural representation of transformer secondary;
Fig. 1 c is the independent winding structural representation;
Fig. 2 a is that full-bridge type power is regulated control signal figure on a large scale;
Fig. 2 b is semibridge system power fine setting control signal figure;
Fig. 3 groundwork principle oscillogram;
The equivalent electric circuit of Fig. 4 a operation mode 1;
The equivalent electric circuit of Fig. 4 b operation mode 2;
The equivalent electric circuit of Fig. 4 c operation mode 2;
The equivalent electric circuit of Fig. 4 d operation mode 3;
The asymmetric full bridge PWM control signal of Fig. 5 a figure;
Fig. 5 b semibridge system pwm control signal figure;
The asymmetric phase-shift PWM of Fig. 6 a drives experimental waveform;
The asymmetric phase-shift PWM of Fig. 6 b drives experimental waveform;
The soft switch experiment oscillogram of Fig. 7 a;
The soft switch experiment oscillogram of Fig. 7 b;
The soft switch experiment oscillogram of Fig. 7 c;
The RCD absorption circuit of Fig. 8 routine;
Fig. 9 intersects the clamp buffer circuit.
Embodiment
Below in conjunction with accompanying drawing and embodiment the utility model is described further.
Among Fig. 1, the photovoltaic full bridge soft switch converter system configuration of boosting comprises main circuit structure topological sum control system in the utility model.VT 1And VT 2Be leading arm power switch pipe, VT 3And VT 4Be lagging leg power switch pipe, U G1～U G4Be their drive signal.D T1～D T4Inverse parallel diode for the switching tube parasitism.C 1, C 2Be leading arm capacitance, and C 1=C 2=C rD 1～D 8Be fast recovery diode, L F1, L F2Be output inductor, C O1, C O2Be output filter capacitor, C bBe blocking capacitor, L sBe pulsactor.
This system and traditional full bridge inverter mainly contain following some difference: (1) adopts transformer two-pack limit rectification cascaded structure, has satisfied the requirement of back level three-phase grid-connected inverter high input voltage, has reduced secondary fast recovery diode voltage withstand class simultaneously.(2) on transformer, increased and had switch and linear inductance L cChange of current winding T 12, satisfied the soft switch job requirement of inverter full-load range.(3) big for overcoming traditional phase-shift PWM controlled converter intermediate ring road electric current, the problem that loss is serious, blocking capacitor C has connected on the former limit of transformer b, this electric capacity also helps improving the anti-magnetic bias ability of transformer simultaneously.
The utility model adopts TI company's T MS320F2812 chip as master controller, and main functional modules comprises: the realization of MPPT maximum power point tracking, phase-shift PWM, A/D conversion, error protection, keyboard and liquid crystal display.This system at first becomes digital quantity with input, output voltage, current signal through the A/D module converts, then according to the demand of MPPT maximum power point tracking control, regulate the switching time and the phase difference of four tunnel control signals of DSP generation, and utilize pulse transformer to drive the device for power switching of leading arm and lagging leg.
Under-voltage, overvoltage in the control system, overcurrent, guard signal such as overheated flow to the universaling I/O port of DSP; with the fault type of judging that it is concrete; simultaneously with these protection output signals with after be connected to the PDPINTA pin, hardware protection when realizing fault, quick switch-off power switching device.Realize and upper remote data communication by the CAN module; The SCI communication module is finished execute-in-place control and liquid crystal display.
Operation principle of the present utility model is: classical phase-shift PWM controlled is by regulating leading arm and the phase shift of lagging leg conducting pulsewidth, the realization power output is regulated, and leading arm and lagging leg pulse duration are not regulated (Ruan Xinbo, tight Rangoon. the soft switch technique [M] of pulse-width modulation DC/DC full-bridge converter. Beijing: Science Press, 2001.; Zhao Zhenmin, Yue Yuntao. a kind of full-bridge soft-switching DC/DC converter [J] based on UC3879 control. power electronic technology, 2005,39 (3): 107-110.).The utility model has provided a kind of new asymmetric phase-shift PWM controlled scheme, and it comprises full-bridge type work and two kinds of situations of semibridge system work.
Full-bridge type working control signal characteristics are shown in Fig. 2 a: opening of (1) leading arm and lagging leg switching tube is constantly identical, and turn-offs different constantly; (2) leading arm control signal pulse-width modulation, and the lagging leg control signal keeps maximum pulse width constant.This kind mode of operation can satisfy load internal power regulatory demand on a large scale.And the semibridge system working control signal is shown in Fig. 2 b, and leading arm has turn-offed, and leading arm electric capacity is formed the semibridge system structure with the lagging leg switching tube, and only lagging leg control signal pulse-width modulation this moment is to realize the adjusting of underloading micropower.
The concrete operation principle of novel full-bridge soft-switching inverter is as follows: the former limit of establishing transformer is 1 with single rectification umber of turn ratio: n (n＞1), with change of current winding turns ratio be 1: m (m＜1), change of current inductance value is L o, switch periods is T, ON time is T On, duty ratio D=T then On/ T.For ease of analyzing, suppose: all devices are desirable device; Blocking capacitor value C b＞＞C rTwo rectification circuit device parameters unanimities of outlet side, operation mode is identical, only considers single rectification circuit situation during analysis.
In switch periods of full-bridge inverter, the working condition of circuit is identical in the transformer positive and negative half period, and soft switch work during for assurance system underloading is existing with control switch K 0Closure, positive half period work are the example explanation, and its groundwork waveform as shown in Figure 3.
(1) [t 1～t 2] stage: VT 1And VT 4Zero current passing
Supposing the system is steady operation, t 1Constantly: VT 1And VT 4Conducting simultaneously, the current circuit of transformer is shown in Fig. 4 a.Being added in equivalent inductance and the magnitude of voltage on the pulsactor that transformer leakage inductance, change of current inductance be folded to former limit this moment is (V In+ V Cb), the increase of starting from scratch of the electric current on former limit.Since the inhibitory action that pulsactor changes electric current, switching device VT 1, VT 4Be zero current turning-on.When electric current surpassed the saturation value of pulsactor, pulsactor was equivalent to short circuit, and the electric current on former limit increases sharply.
In this stage, pulsactor provides adequate condition for the switching device zero current turning-on, also produces some duty-cycle loss simultaneously.For reducing duty-cycle loss and excitation loss, select the good Ferrite Material of permeability rectangle performance usually as the pulsactor magnetic core.
At [t 1～t 2] during: the former limit of transformer series capacitance C bVoltage increase by reverse maximum forward.Because the primary current i of transformer pBigger, pulsactor L sBe in short-circuit condition, fast recovery diode D 1And D 4Conducting, change of current inductive current begins the linear increase of forward from maximum reverse current.
Change of current inductive current:
i Lc ( t ) = 1 L c ∫ t 1 t 2 m * u 1 ( t ) dt - - - ( 1 )
Wherein, i Lc(t 1) be the negative peak electric current.
If transformer leakage inductance is L L1, then under the original edge voltage effect of transformer, the linear leakage inductance electric current that increases is:
i l 1 ( t ) = 1 L l 1 ∫ t 1 t 2 u 1 ( t ) dt - - - ( 2 )
Wherein, i 11(t 1) be the negative peak electric current of leakage inductance.
Output inductor L fBigger, output current I in a switch periods oBe constant.Therefore, the electric current on former limit comprises change of current inductive current i Lc, output current I oReduced value and transformer leakage inductance current i L1Sum, promptly
i P(t)＝2*n*I o+m*i Lc(t)+i l1(t) (3)
Blocking capacitor voltage:
u cb ( t ) = 1 C b ∫ t 1 t 2 i p ( t ) dt
Wherein, u Cb(t 1) be its negative peak voltage;
Transformer original edge voltage: u 1(t)=U In-u Cb(t).
(2) [t 2～t 3] stage: VT 1For no-voltage is turn-offed VT 4Still conducting
Shown in Fig. 4 b, at t 2Constantly, VT 1Begin to turn-off, the primary current of transformer is from VT 1Transfer to C 1And C 2Branch road: C 1Begin charging, magnitude of voltage start from scratch linear rising so VT 1For no-voltage is turn-offed; C 2Begin discharge, its voltage linear descends.The rate of change of leading arm capacitance voltage is relevant with load current, and load current is big more, and the rate of climb is fast more.Attention: for guaranteeing VT 1Turn-off for no-voltage, need to determine leading arm capacitance according to the turn-off time of maximum load current and switching tube.
Fast recovery diode D 1And D 4Still conducting, output current I oApproximate constant current.Blocking capacitor voltage v CbConstantly raise, primary current is promptly decayed, and has effectively overcome the big problem of circulation loss that traditional phase-shift PWM controlled is brought.Blocking capacitor C bVoltage is:
v Cb ( t ) = V Cb ( t 2 ) + i P · t - t 2 C b - - - ( 4 )
The resonant capacitance voltage of leading arm parallel connection:
v C 1 ( t ) = I P 2 C r ( t - t 2 ) - - - ( 5 )
v C 2 ( t ) = U in - i P 2 C r ( t - t 2 ) - - - ( 6 )
At [t 2～t 3] during, capacitor C bWith leading arm capacitor C 1, C 2Convert the equivalent inductance L on former limit with transformer leakage inductance and change of current inductance r, form the LC series resonant tank, shown in Fig. 4 c, resonance frequency is
Figure BDA0000036393300000067
Cycle should be less than 0.5T d, T wherein dBe Dead Time; C eBe loop equivalent capacity, i.e. C e=(C 1+ C 2) * C b/ (C 1+ C 2+ C b).
(3) diode DT 2Afterflow, VT 4Turn-off
Shown in Fig. 4 d, leading arm capacitor C 1Voltage through L rC eResonance rises to input voltage U very soon In, C 2Voltage drops to zero.After this by diode D T2Afterflow, pulsactor are still saturated, D T2-C b-L r-VT 4Form the loop.At this moment, the former limit of transformer is by short circuit, rectifier diode D 1～D 4All conductings are for the load output current provides path.
At t 3Constantly, because blocking capacitor is to the attenuation of primary current, reduce to zero oppositely the time when electric current, pulsactor withdraws from saturated, and former limit is equivalent to open a way switching tube VT 4Zero-current switching.
(4) [t 3～t 4] stage: switching tube work " dead band "
At [t 3～t 4] during, shown in Fig. 4 e, because the effect of transformer leakage inductance and pulsactor, the primary current of transformer is very little, almost open circuit.Blocking capacitor voltage is constant, the whole conductings of fast-recovery commutation diode, and the former and deputy polygonal voltage of transformer is zero, the electric current of change of current inductance is constant substantially.
At following half work period, at first VT 2And VT 3Zero current turning-on, leading then arm switch pipe VT 2No-voltage is turn-offed, then VT 3Zero-current switching, VT after the stage of dead band 1And VT 4The while zero current turning-on, the course of work is identical with first cycle.
As load output current I oGreater than set point I GAnd the electric current consecutive hours, K switch 0Disconnect, the soft switch job analysis of system is identical during with charged sense, is that change of current inductance is not worked.I GSize depend on leading arm capacitor charge and discharge situation, promptly to guarantee leading arm switch pipe open before the capacitance voltage of its two ends parallel connection be zero.
(5) semibridge system inversion operation mode
Under the situation of load underloading, leading arm switch pipe turn-offs.Leading arm electric capacity and lagging leg switching tube are formed half bridge circuit, realize the fine setting of power.Under the semibridge system operation mode, because the current switch effect of pulsactor and blocking capacitor be to the attenuation of primary current, the lagging leg switching device still is a Zero Current Switch.
This shows,, can in the total power scope, realize the soft switch of device for power switching based on the modified model inverter of asymmetric phase-shift PWM controlled strategy.
TMS320F2812 is the 32-bit number signal processor that TI company releases in the utility model, and for industrial automation, power electronics control design, its disposal ability can reach 150MIPS specially.Chip internal comprises two task manager EVA and EVB module, each task manager comprises 2 general purpose timers, 3 full comparing units, 8 road PWM output, 3 capturing unit (Su Kuifeng, Lv Qiang .TMS320F2812 principle and exploitation [M]. Beijing: Electronic Industry Press, 2005.).
Utilize DSP to realize the common method of phase-shift PWM waveform: at present, to utilize DSP to realize that Phase-shifted PWM Control Method comprises modification counter initial value method, hardware additive process.Revise counter initial value method (Kim E.S., Kim T.J., Byun Y.B., Koo T.G..High power full-bridge DC/DC converter using digital-to-phase-shift PWM circuit[J] .Institute of Electrical and Electronics Engineers Inc., 2001,1:221-225.), promptly establishing the T1CNT initial value earlier is x 0, the T3CNT initial value is made as 0, calculates phase shifting angle and revises x according to phase shifting angle by control algolithm 0Value realize phase-shift PWM controlled, this method need be utilized two task managers.The hardware additive process, mainly contain DSP+CPLD method (Chen Gang, Zhang Yong, Wang Rui, malleable iron army. based on the inversion spot welding power supply phase-shift PWM controlled research [J] of DSP. electric welding machine, 2006,36 (9): 22-25.) with DSP+D trigger method (Eun-Soo Kim, Tae-Jin Kim, Young-Bok Byun, Tae-Geun Koo.High power full bridge DC/DC convener using digital-to-phase-shift PWM circuit[R] .IEEE APEC 2002.), the former produces the pulse signal that two-way can phase shift by DSP, by CPLD to anti-phase other two path control signal that obtains of control corresponding pulse signal; The latter adopts dsp chip and adds a plurality of d type flip flops and produces the phase-shift pulse signal.As seen, the hardware additive process need be added complicated more circuit, and implementation procedure is trouble.
The utility model utilizes the timer comparing function to realize phase-shift PWM, according to the operation principle of modified model soft switching inverter, has provided a kind of asymmetric phase-shift PWM controlled scheme based on TMS320F2812, shown in Fig. 5 a, Fig. 5 b.
It is to utilize relatively four tunnel required phase-shift PWM controlled signals of interrupt function realization inverter soft switching work of timer.At first select the complementary output U of comparing unit G1, U G2As the drive signal of leading arm, U G3, U G4Drive signal as lagging leg.General purpose timer T is set then 1Counting mode for subtracting count mode continuously, dead band control register DBTCONA sets needed Dead Time, pack into the value n of required PWM carrier cycle of period register 0, the COMCONA register enables compare operation, enables complete comparator.N in modulated process 0Remain unchanged, and set CMPR1=n 1, CMPR2=n 2, in the PWM cycle interruption, change n 1And n 2Value is to adjust the duty ratio of PWM phase-shifted control signal.
Ignoring under the Dead Time situation, the specific implementation method of asymmetric phase-shift PWM controlled signal is as follows:
(1) in the normal output power range, makes the value n of register CMPR2 2Equal period register numerical value n 0, i.e. n 2=n 0At this moment, lagging leg two complementary conductings of power device up and down.Change n 1Value (n 1≤ n 0) can realize 0 °～180 ° variations of leading arm conducting pulsewidth, thus realize the power output adjusting.Work as n 1=n 0The Shi Chaoqian arm turn-offs; Work as n 1=0 o'clock, 180 ° of two each conductings of power device up and down of leading arm, it is maximum that power output reaches.
(2) power output increases process by zero load or underloading: at first, the value of shilling comparand register CMPR1 equals the value of period register, i.e. n 1=n 0Leading arm turn-offs the value n of control lag arm register 2From n 0Reduce gradually, lagging leg conducting pulsewidth increases gradually.Value n as register CMPR2 2Equal at 0 o'clock, it is maximum that the lagging leg pulsewidth reaches.Along with the increase of power output, reduce the value n of CMPR1 gradually 1, leading arm pulsewidth broadens gradually, up to n 1=0, reach maximum conducting pulsewidth.
(3) power output reduces process to zero load, comparand register numerical value change and process (2) changing inversely by fully loaded or heavy duty.Increase the value n of CMPR1 earlier 1, work as n 1=n 0After increase the value n of CMPR2 again 2Up to n 2=n 0, this moment, all power devices turn-offed fully.
This shows, in realizing asymmetric four tunnel phase-shift PWM signal production processes, only need a task manager to produce, and need not add any hardware, thereby improved system reliability.
Fig. 6 a, Fig. 6 b are the pulse transformer drive waveforms of pwm signal, switching frequency 20kHz, Dead Time t=4 μ s.
The drive signal of full-bridge mode work shown in Fig. 6 a, U G1And U G2Pulse-width modulation changes power output, and U G3And U G4Pulse duration is maximum constant.The drive signal of semibridge system work shown in Fig. 6 b, U G1And U G2Complete is zero level, and promptly leading arm turn-offs; U G3And U G4Pulse-width modulation changes power output.
The experimental test result:
Full-bridge DC/DC converter obtains input voltage 200-300VDC by three-phase 380VAC alternating current and experimentizes behind voltage regulating rectifier.Output voltage 600～700VDC is adjustable continuously, switching frequency 20kHz, power 10kW.Switching tube VT 1～VT 4Adopting the IGBT power model model of EUPEC company is BSM200GB60DLC, and fast-recovery commutation diode adopts APT30D100K.
The soft switch work wave of leading arm and lagging leg shown in Fig. 7 a～c, U G1, U G4Leading arm of difference and lagging leg driving voltage waveform; Curve i pBe transformer primary current waveform; Curve U Ce1, U Ce4Be respectively leading arm power device voltage and lagging leg power device voltage waveform, U oBe output voltage waveforms; Curve v CbBe the former limit series connection of transformer blocking capacitor voltage waveform; Curve i LcCurrent waveform for change of current inductance.
By Fig. 7 a as can be seen, leading arm V T1Opening moment electric current is zero, and the primary current of transformer is given the electric capacity charging of leading arm parallel connection during shutoff, and the initial voltage of electric capacity is zero, so V T1For no-voltage is turn-offed.Fig. 7 b is lagging leg V as can be seen T4Turn on and off constantly, the primary current of transformer is zero, so lagging leg is a Zero Current Switch.During underloading under the semibridge system inversion mode of operation, the lagging leg device for power switching still is zero current turning-on, zero-current switching to Fig. 7 c as can be seen.Because the capacitance of leading arm parallel connection is less, the primary current i of transformer pChange and be not triangular wave very much.
Under zero load or light duty, can satisfy the inverter soft switching requirement, but because the auxiliary induction operating mode of electric welding machine has obviously different with operating mode in the photovoltaic generation: (1) is with the Transformer Winding number of turn of change of current inductance identical with secondary rectification umber of turn, the two can be shared, and native system can not be shared, and both numbers of turn are inequality; (2) change of current inductance in the electric welding machine can not disconnect, and the change of current inductance and the K switch of the photovoltaic generating system of applying for 0Series connection is when electric current consecutive hours K switch 0Disconnect.
(1) K switch 0Necessity:
The change of current inductive current (bigger) of transformer: on the one hand, coil copper loss and magnetic core magnetic hysteresis loss increase, and on the other hand, the transformer primary current increases, and cause that the device for power switching on-state loss increases.
(2) K switch 0Selection:
Under the continuous situation of output current, the leading arm electric capacity change of current is complete, K switch 0Disconnect, can eliminate the inaction loss that change of current inductance causes.Because the power output pace of change of photovoltaic cell characteristic decision slow (second level), this switch adopts electronic relay, is controlled according to the situation of output current by control board.
(3) output intersection clamp buffer circuit necessity demonstration
Two output rectification series connection improve output voltage to satisfy three-phase photovoltaic grid-connected required High Level DC Voltage (about 700V), can effectively reduce exporting the withstand voltage of fast-recovery commutation diode.For suppressing diode D 1～D 8Oppositely the recovery stage is because the due to voltage spikes that its junction capacitance and the line inductance higher-order of oscillation cause often adopts RCD absorption circuit such as Fig. 8.For not influencing the operate as normal of system, this capacitance voltage should just be controlled at diode voltage safety operation area 800V (rated voltage is the fast recovery diode of 1200V) for good.Each switch periods C F1The higher-order of oscillation energy that absorbs should in time discharge, in order to avoid voltage continues to increase the damage diode.Shown in Figure 8, resistance R 1Be positioned at capacitor C F1With output capacitance C 01Between, R 1* C F1The frequency that discharges and recharges be 2 times of switching frequency.
Single output rectifier output voltage is:
0.5U o＝0.5*700＝350V，
Therefore, the buffer capacitor change in voltage is:
dU＝800-350＝450V，
Then buffer capacitor discharges and recharges power and is
P c＝1/2*C*dU^2*2*f＝k*C*dU^2
As seen discharge resistance power is
P r＝P c＝k*C*dU^2
For guaranteeing diode D 1～D 8Crest voltage be operated in the safety operation area, reduce resistance R again 1And R 2Power consumption, need to reduce the capacitance voltage fluctuation range, intersection clamp connected mode has been proposed as shown in Figure 9.
Capacitance voltage C fThe both end voltage fluctuation range is:
dU＝800-700＝100V
With intersect before relatively, the discharge resistance power ratio is
P 1r/P 2r＝450^2/100^2＝2025
As seen, power consumption only is 1/20th of the simple series connection of two rectification circuits.
(4) inductance L 1 and L2 are coupling inductance
Inductance L 1 and L2 are coupling inductance, and both shared magnetic cores under the constant situation of filter effect, have effectively reduced the quantity of magnetic core, have reduced system cost and volume.

Claims (6)

1. a photovoltaic high-frequency isolation soft switch DC/DC converter that boosts, it comprises high frequency transformer, its former limit is provided with the phase-shift PWM controlled converter, it is characterized in that, described high frequency transformer is provided with three secondary, wherein two secondary employing full-bridge circuits are connected in series and carry out rectification with output HIGH voltage, their output and output voltage, current sampling circuit connects, output voltage, current sampling circuit is connected with controller, the phase shift output of controller is connected with isolated drive circuit, isolated drive circuit then is connected with the phase-shift PWM controlled converter on former limit, and the phase-shift PWM controlled converter on former limit is provided with the blocking capacitor C of series connection bWith pulsactor L SThe 3rd secondary is step-down windings in series change of current inductance and K switch 0
2. the photovoltaic high-frequency isolation as claimed in claim 1 soft switch DC/DC converter that boosts is characterized in that described phase-shift PWM controlled converter is the full-bridge circuit in parallel with photovoltaic cell, and it is by the power switch pipe VT of band inverse parallel diode 1, VT 2Be composed in series leading arm, the power switch pipe VT of band inverse parallel diode 3, VT 4Be composed in series lagging leg; Wherein, VT 1, VT 2Respectively with capacitor C 1And C 2In parallel; The lagging leg power switch pipe is shunt capacitance not.Blocking capacitor C bWith pulsactor L SConnect with the former limit of high frequency transformer.
3. the photovoltaic high-frequency isolation as claimed in claim 1 soft switch DC/DC converter that boosts is characterized in that a full bridge rectifier is by fast recovery diode D in the described secondary 1-D 4Form the diode D of the output of this rectification circuit serial connection in parallel F1, capacitor C F1An output is again through filter inductance L F1Another output and the output filter capacitor C of back and this full-bridge circuit O1In parallel; Resistance R 1An end and D F1And C F1Points of common connection link to each other the other end and filter capacitor C O2Low-pressure end links to each other.
Second full bridge rectifier is by fast recovery diode D 5-D 8Form the diode D of the output of this rectification circuit serial connection in parallel F2, capacitor C F2, an output is again through filter inductance L F2Another output and the output filter capacitor C of back and this full-bridge circuit O2In parallel; Resistance R 2An end and D F2And C F2Points of common connection link to each other the other end and filter capacitor C O1High-pressure side links to each other.
Filter inductance L F1With filter inductance L F2Be the shared magnetic core of coupling inductance; Output D F1-R 1-C F1With D F2-R 2-C F2Constitute intersection clamp buffer circuit.
4. the photovoltaic high-frequency isolation as claimed in claim 1 soft switch DC/DC converter that boosts is characterized in that, series connection change of current inductance and K switch 0The step-down winding, its form of expression has three kinds: first kind is the tap winding on the former limit of transformer; Second kind is the tap winding of transformer secondary; The third is an independent winding.
5. the photovoltaic high-frequency isolation as claimed in claim 1 soft switch DC/DC converter that boosts is characterized in that described controller core processor is the TMS320F2812 chip.
6. as claim 1 or the 4 described photovoltaic high-frequency isolation soft switch DC/DC converter that boosts, it is characterized in that described controller is also under-voltage with input, overvoltage, overcurrent are connected with overheating protection circuit.
CN2010206447849U 2010-12-06 2010-12-06 DC/DC changer of photovoltaic high-frequency isolating boosting soft switch Expired - Fee Related CN201869102U (en)

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