CN105048490A - Low current stress photovoltaic micro inverter and digital control device associated with the same - Google Patents
Low current stress photovoltaic micro inverter and digital control device associated with the same Download PDFInfo
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Abstract
The invention discloses a low current stress photovoltaic micro inverter and a digital control device associated with the same. The main circuit of the photovoltaic micro inverter comprises a Buck-Boost converter, a high frequency full-bridge inverter, a follow current switch, an energy buffering inductor, a transformer, a rectifier, a pseudo direct current link filter capacitor, a power frequency inverter and a grid connecting filter inductor. The digital control device works according to a DSP digital controller. The input voltage and the output voltage from the Buck-Boost converter are connected in series to serve for the input power supply of the high frequency full-bridge inverter and the output voltage from the Buck-Boost converter is controlled to change regularly in a power frequency cycle to ensure reduced current stress of devices under the same power. The follow current switch is capable of maintaining the current from the energy buffering inductor in a discontinuous state so as to realize the soft switching of electric appliance and to realize efficient power conversion. The Buck-Boost converter and the high frequency full-bridge inverter share two common switch tubes. For such an arrangement, the manufacturing cost for the micro inverter is reduced without sacrificing the performance of the inverter.
Description
Technical field
The present invention relates to a kind of photovoltaic micro-inverter and numerical control device thereof of low current stress, belong to converters and control technology field thereof.
Background technology
Photovoltaic generation is subject to increasing attention as one of the important way of renewable energy utilization, photovoltaic cell generates electricity to process and is divided into independent operating mode and synchronizing mode, wherein independent operating mode is applicable to the remote districts that electrical network is difficult to arrive, and system generally needs to be equipped with storage battery; The photovoltaic generating system of synchronizing mode can not be equipped with the higher storage battery of cost, is therefore widely studied.At present, photovoltaic under synchronizing mode exports electric energy process two kinds of modes, and namely focus on and power with modularization, wherein focusing on is gone here and there on a large scale by photovoltaic cell and combine, obtain rational voltage, carry out grid-connected after adopting the converter concentrated to carry out energy conversion; Modularization is powered and is undertaken integrated by monolithic photovoltaic battery panel and corresponding small-power converter, and be referred to as AC module, small-power converter is wherein exactly micro-inverter.Because the output voltage of monolithic photovoltaic cell is lower, therefore the micro-inverter research with high-frequency isolation transformer is wider, according to converter intermediate link direct voltage type, micro-inverter can be divided into without the micro-inverter of DC link, have the micro-inverter of DC link and the micro-inverter of pseudo-DC link.Because the Sine Modulated of the micro-inverter of pseudo-DC link is carried out in prime DC/DC converter, the inverter power frequency work of grid side, greatly reduces switching loss, is therefore widely studied at present.
Although the more employing circuit of reversed excitation of the front stage converter of the micro-inverter of pseudo-DC link, but circuit of reversed excitation device current, voltage stress are all larger, there is the problems such as transformer leakage inductance resonance, and along with monolithic photovoltaic power increasing, the efficiency of circuit of reversed excitation process is more and more lower.Although bridge circuit circuit structure is slightly complicated, its device voltage, current stress are all lower, and resonant element can be coordinated easily to realize the Sofe Switch of device, and being therefore applied in micro-inverter by bridge circuit has brighter prospect.
The micro-inverter of Full-Bridge Buck type, high frequency transformer prime adopts active full-bridge, the rectifying full bridge circuit that transformer rear class adopts diode to form, energy snubber adopts single inductance, and design buffer inductance current work can realize zero current turning-on and the zero-current switching of device in discontinuous mode.But there is an obvious shortcoming in the micro-inverter of pseudo-DC link Full-Bridge Buck type: flow to output for realizing energy when ensureing line voltage peak value by input, must ensure that the step-up ratio of transformer is larger, the problem brought thus is when line voltage is lower, transformer preceding-stage inversion device runs with minimum modulation ratio, and the electric current flowing to load-side is equal, so the switching device of transformer prime bears current effective value very greatly, causes loss higher.According to this problem, one-level power conversion can be increased again before transformer preceding-stage inversion device, realize the input voltage of the micro-inverter of Full-Bridge Buck type with grid voltage change, but the conversion stages increased reduces system effectiveness.
Therefore, set up a kind of can not increase power conversion progression and the input voltage realizing the micro-inverter of Full-Bridge Buck type with the circuit topology of voltage ripple of power network and control strategy, to improve micro-inverter efficiency, improve photovoltaic cell utilance, reduce system cost there is positive meaning.
Therefore, find do not increase conversion progression, reasonably circuit structure and control strategy, the micro-inverter input voltage of guarantee Full-Bridge Buck type with voltage ripple of power network, and is main task of the present invention by the stable operation of digit chip control realization whole system.
Summary of the invention
Goal of the invention: the problem that during for the micro-inverter of pseudo-DC link Full-Bridge Buck type near line voltage zero passage, device current stress is excessive, propose to increase a brachium pontis in the multiplexing bridge circuit of buck-boost converter, output and the photovoltaic cell of buck-boost converter are in series, control the output voltage of buck-boost converter with voltage ripple of power network, ensure that the high frequency transformer boosting of design is smaller, thus when ensureing that the micro-inverter of pseudo-DC link Full-Bridge Buck type is near line voltage zero passage, the current stress of device is less.Effectively can reduce the current stress of device according to the program, and improve the conversion efficiency of system and the utilance of photovoltaic cell.
Technical scheme: a kind of photovoltaic micro-inverter of low current stress, comprises buck-boost converter, high frequency full-bridge inverter, continued flow switch, energy snubber inductance, transformer, rectifier, pseudo-DC link filter electric capacity, power frequency inverter, grid-connected filter inductance.Wherein, buck-boost converter exports energy as input power using photovoltaic cell, and comprises photovoltaic cell filter capacitor C
pV, buck inductance L
bB, band anti-and the first switching tube, second switch pipe, the buck output filter capacitor C of diode
bB; The source electrode of the first switching tube is connected with the drain electrode of second switch pipe, the drain electrode of the first switching tube and buck output filter capacitor C
bBanode connect, the source electrode of second switch pipe and photovoltaic cell filter capacitor C
pVnegative terminal and photovoltaic cell negative terminal connect, buck inductance L
bBone end be connected to the tie point that the first switching tube source electrode and second switch pipe drain, buck inductance L
bBthe other end and anode, the photovoltaic cell filter capacitor C of photovoltaic cell
pVanode, buck output filter capacitor C
bBnegative terminal link together;
Described high frequency full-bridge inverter and public first switching tube of buck-boost converter, second switch pipe, and the 3rd switching tube, the 4th switching tube that comprise the anti-also diode of band.Wherein the source electrode of the 3rd switching tube is connected with the drain electrode of the 4th switching tube, the drain electrode of the 3rd switching tube and the drain electrode of the first switching tube and buck output filter capacitor C
bBanode connect, the source electrode of the 4th switching tube and the source electrode of second switch pipe, photovoltaic cell filter capacitor C
pVnegative terminal, photovoltaic cell negative terminal connect;
Described continued flow switch comprises the 5th switching tube, the 6th switching tube of the anti-also diode of band; Wherein the drain electrode of the 5th switching tube is connected with the drain electrode of the 6th switching tube, the source electrode of the 5th switching tube and the source electrode of the first switching tube, the drain electrode of second switch pipe, buck inductance L
bBthe other end, energy snubber inductance L
rone end link together, the drain electrode of the source electrode of the 6th switching tube and the source electrode of the 3rd switching tube, the 4th switching tube links together;
Described rectifier comprises the first diode, the second diode, the 3rd diode, the 4th diode.The anode of the first diode is connected with the negative electrode of the second diode, and the anode of the 3rd diode is connected with the negative electrode of the 4th diode, and the negative electrode of the first diode is connected with the negative electrode of the 3rd diode, and the anode of the second diode is connected with the anode of the 4th diode;
Described transformer comprises former limit winding and vice-side winding, the Same Name of Ends of its limit, Central Plains winding and energy snubber inductance L
rthe other end connect, the different name end of former limit winding and the drain electrode of the 6th switching tube, the source electrode of the 3rd switching tube, the drain electrode of the 4th switching tube link together; The Same Name of Ends of transformer secondary winding is connected with the negative electrode of the anode of the first diode, the second diode, and the different name end of vice-side winding is connected with the negative electrode of the anode of the 3rd diode, the 4th diode;
Described power frequency inverter comprises the first thyristor, the second thyristor, the 3rd thyristor, the 4th thyristor, wherein the negative electrode of the first thyristor, the anode of the second thyristor and grid-connected filter inductance L
gone end connect, the negative electrode of the 3rd thyristor, the anode of the 4th thyristor are connected with the zero line of electrical network; The anode of the first thyristor, the anode of the 3rd thyristor, the negative electrode of the first diode, the negative electrode of the 3rd diode and pseudo-DC link filter electric capacity C
ganode link together; The negative electrode of the second thyristor, the negative electrode of the 4th thyristor, the anode of the second diode, the anode of the 4th diode and pseudo-DC link filter electric capacity C
gnegative terminal link together; Grid-connected filter inductance L
gthe other end be connected with the live wire of electrical network.
Buck-boost converter and high frequency full-bridge inverter share the brachium pontis that two switching tubes are formed, and under the prerequisite not reducing systematic function, reduce the cost of system; The output voltage controlling buck-boost converter be that certain rule changes with line voltage, and using it input power as high frequency full-bridge inverter, effectively can reduce the current stress of whole system breaker in middle device, improve the efficiency of whole micro-inverter system.
A kind of numerical control device of photovoltaic micro-inverter of low current stress, comprise the first voltage sensor, second voltage sensor, tertiary voltage transducer, first current sensor, second current sensor, 3rd current sensor and DSP digitial controller, wherein DSP digitial controller comprises phase-locked loop, first subtracter, buck voltage regulator, second subtracter, buck current regulator, first signal modulator, MPPT maximum power point tracking module, multiplier, high frequency full-bridge inverter modulation ratio precalculation module, 3rd subtracter, power network current adjuster, adder, secondary signal modulator and polarity recognizer,
The input of the first voltage sensor is connected to buck output filter capacitor C
bBtwo ends, the input of the second voltage sensor is connected to the two ends of photovoltaic cell, and tertiary voltage transducer is connected to the two ends of electrical network, the first current sensor and buck inductance L
bBbe in series, the second current sensor and photovoltaic cell are in series, the 3rd current sensor and grid-connected filter inductance L
gbe in series;
The input of phase-locked loop connects the output of above-mentioned tertiary voltage transducer, first of phase-locked loop exports the positive input terminal of termination first subtracter, the output of negative input termination first voltage sensor of the first subtracter, the input of the output termination buck voltage regulator of the first subtracter, the positive input terminal of output termination second subtracter of buck voltage regulator, the output of negative input termination first current sensor of the second subtracter, the input of the output termination buck current regulator of the second subtracter, the input of output termination first signal modulator of buck current regulator, the output of the first signal modulator exports the first switching tube, the drive singal of second switch pipe,
First, second input of MPPT maximum power point tracking module connects the output of the second current sensor and the output of the second voltage sensor respectively; First, second input of multiplier connects the second output of phase-locked loop and the output of MPPT maximum power point tracking module respectively; First, second, third input of high frequency bridge-type inverter modulation ratio precalculation module connects the output of the output of multiplier, the output of the second voltage sensor and tertiary voltage transducer respectively;
The positive input terminal of the 3rd subtracter and negative input end connect the output of multiplier and the output of the 3rd current sensor respectively, and the output of the 3rd subtracter gets access to grid the input of current regulator; First addition end and the second addition end of adder get access to grid the output of current regulator and the output of high frequency full-bridge inverter premodulated than computing module respectively; First, second input of secondary signal modulator connects the output of the first signal modulator and the output of adder respectively, the output of secondary signal modulator export the 3rd switching tube, the 4th switching tube, the 5th switching tube, the 6th switching tube, drive singal;
The output of the input termination tertiary voltage transducer of polarity recognizer, the output of polarity recognizer exports the drive singal of the first thyristor, the second thyristor, the 3rd thyristor, the 4th thyristor.
Beneficial effect: after adopting such scheme, the present invention is in series by the output voltage of buck-boost converter and the output voltage of photovoltaic cell, increase input voltage size on the one hand, also achieve the input voltage of the micro-inverter of Full-Bridge Buck type with voltage ripple of power network on the other hand, ensure that switching device realizes high-quality grid-connected function with less current stress, improve the whole efficiency of micro-inverter.
Accompanying drawing explanation
Fig. 1 is photovoltaic micro-inverter and the numerical control device block diagram thereof of the low current stress of the embodiment of the present invention;
Fig. 2 is the main signal waveform schematic diagram of the embodiment of the present invention in a power frequency period;
Fig. 3 be the embodiment of the present invention when line voltage positive half period, the main oscillogram in a power frequency period;
Fig. 4 be the embodiment of the present invention when line voltage positive half period, the equivalent circuit diagram of mode 1;
Fig. 5 be the embodiment of the present invention when line voltage positive half period, the equivalent circuit diagram of mode 2;
Fig. 6 be the embodiment of the present invention when line voltage positive half period, the equivalent circuit diagram of mode 3;
Fig. 7 be the embodiment of the present invention when line voltage positive half period, the equivalent circuit diagram of mode 4;
Fig. 8 be the embodiment of the present invention when line voltage positive half period, the equivalent circuit diagram of mode 5;
Fig. 9 be the embodiment of the present invention when line voltage positive half period, the equivalent circuit diagram of mode 6;
Figure 10 be the embodiment of the present invention when line voltage positive half period, the equivalent circuit diagram of mode 7;
Designation in figure: U
pV---photovoltaic cell output voltage; I
pV---photovoltaic cell output current; C
pV---photovoltaic cell filter capacitor; U
bB---buck-boost converter output voltage; C
bB---buck output filter capacitor; i
bB---buck inductive current; S1-S6---the first switching tube is to the 6th switching tube; i
s1-i
s4---flow through the electric current of the first switching tube to the 4th switching tube; D1-D4---the first diode is to the 4th diode; L
r---energy snubber inductance; i
r---energy snubber inductive current; T---high frequency transformer; W1---high frequency transformer former limit winding; W2---high frequency transformer vice-side winding; N---high frequency transformer step-up ratio; i
w2---high frequency transformer secondary winding current; u
aB---high frequency full-bridge inverter output voltage; u
cD---high frequency transformer secondary voltage; U
dC---pseudo-DC link output voltage; C
dC---pseudo-DC link filter electric capacity; i
rec---rectifier current output; i
ga---power frequency input current of inverter; VT1-VT4---the first thyristor is to the 4th thyristor; L
g---grid-connected current filter inductance; i
g---grid-connected current; u
g---line voltage; U
bBf---the first voltage sensor output signal; i
bBf---the first current sensor output; U
pVf---the second voltage sensor output signal; I
pVf---the second current sensor output; u
gf---tertiary voltage sensor output signal; i
gf---the 3rd current sensor output; U
bB*---buck-boost converter output voltage reference signal; U
bBe---the first subtracter output signal; i
bB*---buck-boost converter inductive current reference signal; i
bBe---the second subtracter output signal; U
bBr---buck-boost converter modulation signal; i
ge---the 3rd subtracter output signal; i
g*---grid-connected current reference signal; I
g---grid-connected current reference amplitude signal; ω t---grid phase angle signal; d
w---grid-connected current duty cycle trimmer signal; d
w---the pre-tonal signal of grid-connected current duty ratio; i
gr---grid-connected current duty cycle signals; u
s1~ u
s6---the first switching tube is to the drive singal of the 6th switching tube; u
vT1~ u
vT4---the first thyristor is to the drive singal of the 4th thyristor.
Embodiment
Below in conjunction with specific embodiment, illustrate the present invention further, these embodiments should be understood only be not used in for illustration of the present invention and limit the scope of the invention, after having read the present invention, the amendment of those skilled in the art to the various equivalent form of value of the present invention has all fallen within the application's claims limited range.
As shown in Figure 1, the photovoltaic micro-inverter of low current stress, comprises buck-boost converter, high frequency full-bridge inverter, continued flow switch, energy snubber inductance L
r, transformer T, rectifier, pseudo-DC link filter electric capacity C
dC, power frequency inverter, grid-connected filter inductance.Wherein, buck-boost converter exports energy as input power using photovoltaic cell, and comprises photovoltaic cell filter capacitor C
pV, buck inductance L
bB, band anti-and the first switching tube S1, second switch pipe S2, the buck output filter capacitor C of diode
bB; The source electrode of S1 is connected with the drain electrode of S2, the drain electrode of S1 and buck output filter capacitor C
bBanode connect, the source electrode of S2 and photovoltaic cell filter capacitor C
pVnegative terminal and photovoltaic cell negative terminal connect, buck inductance L
bBone end be connected to the tie point that S1 source electrode and S2 drain, buck inductance L
bBthe other end and anode, the photovoltaic cell filter capacitor C of photovoltaic cell
pVanode, buck output filter capacitor C
bBnegative terminal link together;
High frequency full-bridge inverter and buck-boost converter public S1, S2, and the 3rd switching tube S3, the 4th switching tube S4 that comprise the anti-also diode of band.Wherein the source electrode of S3 is connected with the drain electrode of S4, the drain electrode of S3 and the drain electrode of S1 and buck output filter capacitor C
bBanode connect, the source electrode of S4 and the source electrode of S2, photovoltaic cell filter capacitor C
pVnegative terminal, photovoltaic cell negative terminal connect;
Continued flow switch comprises the 5th switching tube S5, the 6th switching tube S6 of the anti-also diode of band; Wherein the drain electrode of S5 is connected with the drain electrode of S6, the source electrode of S5 and the source electrode of S1, the drain electrode of S2, buck inductance L
bBthe other end, energy snubber inductance L
rone end link together, the drain electrode of the source electrode of S6 and the source electrode of S3, S4 links together;
Rectifier comprises the first diode D1, the second diode D2, the 3rd diode D3, the 4th diode D4.The anode of D1 is connected with the negative electrode of D2, and the anode of D3 is connected with the negative electrode of D4, and the negative electrode of D1 is connected with the negative electrode of D3, and the anode of D2 is connected with the anode of D4;
Transformer T comprises former limit winding W1 and vice-side winding W2, wherein the Same Name of Ends of W1 and energy snubber inductance L
rthe other end connect, the different name end of W1 and the drain electrode of S6, the source electrode of S3, the drain electrode of S4 link together; The Same Name of Ends of W2 is connected with the negative electrode of the anode of D1, D2, and the different name end of W2 is connected with the anode of D3, the negative electrode of D4;
Power frequency inverter comprises the first thyristor VT1, the second thyristor VT2, the 3rd thyristor VT3, the 4th thyristor VT4, wherein the negative electrode of VT1, the anode of VT2 and grid-connected filter inductance L
gone end connect, the anode of VT3, VT4 is connected with the zero line of electrical network; The anode of VT1, the anode of VT3, the negative electrode of D1, the negative electrode of D3 and pseudo-DC link filter electric capacity C
ganode link together; The negative electrode of VT2, the negative electrode of VT4, the anode of D2, the anode of D4 and pseudo-DC link filter electric capacity C
gnegative terminal link together; Grid-connected filter inductance L
gthe other end be connected with the live wire of electrical network.
The numerical control device of the photovoltaic micro-inverter of low current stress, comprise the first voltage sensor, second voltage sensor, tertiary voltage transducer, first current sensor, second current sensor, 3rd current sensor and DSP digitial controller, wherein DSP digitial controller comprises phase-locked loop, first subtracter, buck voltage regulator, second subtracter, buck current regulator, first signal modulator, MPPT maximum power point tracking module, multiplier, high frequency full-bridge inverter modulation ratio precalculation module, 3rd subtracter, power network current adjuster, adder, secondary signal modulator and polarity recognizer,
The input of the first voltage sensor is connected to buck output filter capacitor C
bBtwo ends, the input of the second voltage sensor is connected to the two ends of photovoltaic cell, and tertiary voltage transducer is connected to the two ends of electrical network, the first current sensor and buck inductance L
bBbe in series, the second current sensor and photovoltaic cell are in series, the 3rd current sensor and grid-connected filter inductance L
gbe in series;
The input of phase-locked loop connects the output of above-mentioned tertiary voltage transducer, first of phase-locked loop exports the positive input terminal of termination first subtracter, the output of negative input termination first voltage sensor of the first subtracter, the input of the output termination buck voltage regulator of the first subtracter, the positive input terminal of output termination second subtracter of buck voltage regulator, the output of negative input termination first current sensor of the second subtracter, the input of the output termination buck current regulator of the second subtracter, the input of output termination first signal modulator of buck current regulator, the output of the first signal modulator exports S1, the drive singal of S2,
First, second input of MPPT maximum power point tracking module connects the output of the second current sensor and the output of the second voltage sensor respectively; First, second input of multiplier connects the second output of phase-locked loop and the output of MPPT maximum power point tracking module respectively; First, second, third input of high frequency bridge-type inverter modulation ratio precalculation module connects the output of the output of multiplier, the output of the second voltage sensor and tertiary voltage transducer respectively;
The positive input terminal of the 3rd subtracter and negative input end connect the output of multiplier and the output of the 3rd current sensor respectively, and the output of the 3rd subtracter gets access to grid the input of current regulator; First addition end and the second addition end of adder get access to grid the output of current regulator and the output of high frequency full-bridge inverter premodulated than computing module respectively; First, second input of secondary signal modulator connects the output of the first signal modulator and the output of adder respectively, the output of secondary signal modulator export S3, S4, S5, S6, drive singal;
The output of the input termination tertiary voltage transducer of polarity recognizer, the output of polarity recognizer exports the drive singal of VT1, VT2, VT3, VT4.
The signal of the first input end of high frequency full-bridge inverter modulation ratio precalculation module, the second input, the 3rd input is i respectively
g*, U
pVf, u
gf, then high frequency full-bridge inverter modulation ratio precalculation module d
pfor:
wherein, k
1, k
2, k
3for the constant relevant to circuit.
Fig. 2 gives the present invention the waveform modulated schematic diagram in a power frequency period, can find out, in a power frequency period, the frequency modulating signal of buck-boost converter is the power frequency of twice, and the output voltage that can obtain buck-boost converter thus presents periodic fluctuation; The Sine Modulated of high frequency full-bridge inverter based on buck brachium pontis switching tube S1, S2, and controls another brachium pontis switching tube S3, S4 realization, so can obtain the output voltage u of high frequency full-bridge inverter
aBfor the high-frequency alternating current of Sine Modulated; The design of energy snubber inductive current can be ensured the Zero Current Switch of device at discontinuous conduct mode.Rectifier is by the rectification of buffer inductance high-frequency ac current and obtain steamed bun ripple electric current through pseudo-DC link filter capacitor filtering, finally realizes grid-connected by the power frequency inverter that loss is minimum, obtains high-quality grid-connected current.
When Fig. 3 is line voltage positive half cycle, the main waveform of micro-inverter in a switch periods, the wherein complementary conducting of two switching tubes S1, S2 of buck-boost converter, and another brachium pontis S3, S4 two switching tubes of full-bridge inverter are staggered conducting, and there is simultaneously not ON time centre, during this period of time by continued flow switch pipe S5, S6 conducting, and the electric current of afterflow energy snubber inductance.
Know in a switch periods have 7 switch mode by Fig. 3, the corresponding time is t
0-t
7.When Fig. 4 to Figure 10 is line voltage positive half cycle, carry the equivalent electric circuit of micro-inverter in a switch periods, the following detailed description of these 7 circuit mode.
Switch mode 1 [corresponding diagram 4]:
T
0before moment, switching tube S2 conducting, energy snubber inductive current i
r=0, therefore no current in rectifier, buck inductive current is greater than 0.At t
0in the moment, switching tube S2 turns off, switching tube S1, S4 conducting.T
0after moment, due to slope voltage inductance current i
bBbe greater than current i
r, therefore switching tube S1 and anti-also diode thereof have electric current to flow through; Buck inductive current i
bBto reduce gradually, energy snubber inductive current then linearly increases; In transformer secondary circuit, rectifier diode D1, D4 conducting, power frequency inverter VT1, VT4 conducting, and by the Energy transfer grid side by transformer primary side.
Switch mode 2 [corresponding diagram 5]:
T
1moment, current i
bBbe greater than current i
r, the sense of current flowing through switching tube S1 changes, and flow to source electrode by its drain electrode, other state of circuit is consistent with switch mode 1.
Switch mode 3 [corresponding diagram 6]:
T
2in the moment, switching tube S4 turns off, continued flow switch pipe S5, S6 conducting; Current i
bBcontinue to decline, inductance storage power transfers to buck filter capacitor; Current i
rafterflow is carried out, current i by continued flow switch pipe S5, S6
rlinear decline is become from linear rising.
Switch mode 4 [corresponding diagram 7]:
T
3moment, current i
rdrop to 0, then continued flow switch pipe S5, S6 turn off naturally, also do not have electric current to flow through in rectifier; In this stage, except thyristor VT1, VT4 of buck-boost converter breaker in middle pipe S1 and power frequency inverter has electric current and flow through, in micro-inverter, other switching device does not all have electric current to flow through.
Switch mode 5 [corresponding diagram 8]:
T
4in the moment, on-off switching tube S1, S5, S6, open switching tube S2, S3; High frequency full-bridge inverter output voltage u
aBbecome negative value, therefore buck inductive current i
bBlinear rising is become, current i from linear decline
rstart reverse linear to increase, transformer secondary output voltage u
cDalso negative value is become.
Switch mode 6 [corresponding diagram 9]:
T
5in the moment, on-off switching tube S3, opens switching tube S5, S6; Due to the effect of continued flow switch, high frequency full-bridge inverter output voltage u
aBbecome 0, thereafter, current i
bBcontinue linear increasing, and energy snubber inductive current i
rthrough continued flow switch S5, S6 afterflow, current value starts to diminish.
Switch mode 7 [corresponding Figure 10]:
T
6moment, energy snubber inductive current i
rdrop to 0, in circuit except thyristor VT1, VT4 of buck switching tube S2 and power frequency inverter have electric current and flow through, in micro-inverter, other switching device does not all have electric current to flow through.
T
7in the moment, next switch periods starts.
In sum, the present invention carry low current stress photovoltaic micro-inverter be increase switching device basis on, add buck-boost converter, reduce system cost; The output voltage of buck-boost converter and the output voltage of photovoltaic cell are in series, increase input voltage size on the one hand, also achieve the input voltage of the micro-inverter of Full-Bridge Buck type with voltage ripple of power network on the other hand, ensure that switching device realizes high-quality grid-connected function with less current stress, improve the whole efficiency of micro-inverter.
Claims (6)
1. the photovoltaic micro-inverter of a low current stress, it is characterized in that, comprise buck-boost converter, high frequency full-bridge inverter, continued flow switch, energy snubber inductance, transformer, rectifier, pseudo-DC link filter electric capacity, power frequency inverter, grid-connected filter inductance; Wherein, buck-boost converter using photovoltaic cell output voltage as input power, and comprises photovoltaic cell filter capacitor C
pV, buck inductance L
bB, band anti-and the first switching tube, second switch pipe, the buck output filter capacitor C of diode
bB; The source electrode of the first switching tube is connected with the drain electrode of second switch pipe, the drain electrode of the first switching tube and buck output filter capacitor C
bBanode connect, the source electrode of second switch pipe and photovoltaic cell filter capacitor C
pVnegative terminal and photovoltaic cell negative terminal connect, buck inductance L
bBone end be connected to the tie point that the first switching tube source electrode and second switch pipe drain, buck inductance L
bBthe other end and anode, the photovoltaic cell filter capacitor C of photovoltaic cell
pVanode, buck output filter capacitor C
bBnegative terminal link together.
2. the photovoltaic micro-inverter of low current stress as claimed in claim 1, is characterized in that, described high frequency full-bridge inverter and public first switching tube of buck-boost converter, second switch pipe, and comprises the 3rd switching tube, the 4th switching tube of the anti-also diode of band; Wherein the source electrode of the 3rd switching tube is connected with the drain electrode of the 4th switching tube, the drain electrode of the 3rd switching tube and the drain electrode of the first switching tube and buck output filter capacitor C
bBanode connect, the source electrode of the 4th switching tube and the source electrode of second switch pipe, photovoltaic cell filter capacitor C
pVnegative terminal, photovoltaic cell negative terminal connect.
3. the photovoltaic micro-inverter of low current stress as claimed in claim 1, is characterized in that, described continued flow switch comprises the 5th switching tube, the 6th switching tube of the anti-also diode of band; Wherein the drain electrode of the 5th switching tube is connected with the drain electrode of the 6th switching tube, the source electrode of the 5th switching tube and the source electrode of the first switching tube, the drain electrode of second switch pipe, buck inductance L
bBthe other end, energy snubber inductance L
rone end link together, the drain electrode of the source electrode of the 6th switching tube and the source electrode of the 3rd switching tube, the 4th switching tube links together;
Described rectifier comprises the first diode, the second diode, the 3rd diode, the 4th diode.The anode of the first diode is connected with the negative electrode of the second diode, and the anode of the 3rd diode is connected with the negative electrode of the 4th diode, and the negative electrode of the first diode is connected with the negative electrode of the 3rd diode, and the anode of the second diode is connected with the anode of the 4th diode;
Described transformer comprises former limit winding and vice-side winding, the Same Name of Ends of its limit, Central Plains winding and energy snubber inductance L
rthe other end connect, the different name end of former limit winding and the drain electrode of the 6th switching tube, the source electrode of the 3rd switching tube, the drain electrode of the 4th switching tube link together; The Same Name of Ends of transformer secondary winding is connected with the negative electrode of the anode of the first diode, the second diode, and the different name end of vice-side winding is connected with the negative electrode of the anode of the 3rd diode, the 4th diode.
4. the photovoltaic micro-inverter of low current stress as claimed in claim 1, it is characterized in that, described power frequency inverter comprises the first thyristor, the second thyristor, the 3rd thyristor, the 4th thyristor, wherein the negative electrode of the first thyristor, the anode of the second thyristor and grid-connected filter inductance L
gone end connect, the negative electrode of the 3rd thyristor, the anode of the 4th thyristor are connected with the zero line of electrical network; The anode of the first thyristor, the anode of the 3rd thyristor, the negative electrode of the first diode, the negative electrode of the 3rd diode and pseudo-DC link filter electric capacity C
ganode link together; The negative electrode of the second thyristor, the negative electrode of the 4th thyristor, the anode of the second diode, the anode of the 4th diode and pseudo-DC link filter electric capacity C
gnegative terminal link together; Grid-connected filter inductance L
gthe other end be connected with the live wire of electrical network.
5. the signal of the first input end of high frequency full-bridge inverter modulation ratio precalculation module as claimed in claim 1, the second input, the 3rd input is i respectively
g*, U
pVf, u
gf, then high frequency full-bridge inverter modulation ratio precalculation module d
pfor:
wherein, k
1, k
2, k
3for the constant relevant to circuit.
6. the numerical control device of the photovoltaic micro-inverter of the low current stress as described in claim 1-5 any one, it is characterized in that: comprise the first voltage sensor, second voltage sensor, tertiary voltage transducer, first current sensor, second current sensor, 3rd current sensor and DSP digitial controller, wherein DSP digitial controller comprises phase-locked loop, first subtracter, buck voltage regulator, second subtracter, buck current regulator, first signal modulator, MPPT maximum power point tracking module, multiplier, high frequency full-bridge inverter modulation ratio precalculation module, 3rd subtracter, power network current adjuster, adder, secondary signal modulator and polarity recognizer,
The input of the first voltage sensor is connected to buck output filter capacitor C
bBtwo ends, the input of the second voltage sensor is connected to the two ends of photovoltaic cell, and tertiary voltage transducer is connected to the two ends of electrical network, the first current sensor and buck inductance L
bBbe in series, the second current sensor and photovoltaic cell are in series, the 3rd current sensor and grid-connected filter inductance L
gbe in series;
The input of phase-locked loop connects the output of above-mentioned tertiary voltage transducer, first of phase-locked loop exports the positive input terminal of termination first subtracter, the output of negative input termination first voltage sensor of the first subtracter, the input of the output termination buck voltage regulator of the first subtracter, the positive input terminal of output termination second subtracter of buck voltage regulator, the output of negative input termination first current sensor of the second subtracter, the input of the output termination buck current regulator of the second subtracter, the input of output termination first signal modulator of buck current regulator, the output of the first signal modulator exports the first switching tube, the drive singal of second switch pipe,
First, second input of MPPT maximum power point tracking module connects the output of the second current sensor and the output of the second voltage sensor respectively; First, second input of multiplier connects the second output of phase-locked loop and the output of MPPT maximum power point tracking module respectively; First, second, third input of high frequency bridge-type inverter modulation ratio precalculation module connects the output of the output of multiplier, the output of the second voltage sensor and tertiary voltage transducer respectively;
The positive input terminal of the 3rd subtracter and negative input end connect the output of multiplier and the output of the 3rd current sensor respectively, and the output of the 3rd subtracter gets access to grid the input of current regulator; First addition end and the second addition end of adder get access to grid the output of current regulator and the output of high frequency full-bridge inverter premodulated than computing module respectively; First, second input of secondary signal modulator connects the output of the first signal modulator and the output of adder respectively, the output of secondary signal modulator export the 3rd switching tube, the 4th switching tube, the 5th switching tube, the 6th switching tube, drive singal;
The output of the input termination tertiary voltage transducer of polarity recognizer, the output of polarity recognizer exports the drive singal of the first thyristor, the second thyristor, the 3rd thyristor, the 4th thyristor.
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Inventor after: Ge Yuhua Inventor after: Han Jiarong Inventor after: Zhang Shouguo Inventor after: Wu Yunya Inventor after: Gu Chunlei Inventor after: Xie Shaojun Inventor after: Yang Chen Inventor after: Xu Jinming Inventor before: Han Jiarong Inventor before: Wu Yunya Inventor before: Gu Chunlei Inventor before: Xie Shaojun Inventor before: Yang Chen Inventor before: Xu Jinming |
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Denomination of invention: Low current stress photovoltaic micro inverter and its digital control device Effective date of registration: 20210705 Granted publication date: 20170725 Pledgee: Bank of Suzhou Co.,Ltd. Yancheng branch Pledgor: JIANGSU HASEN ELECTRIC Co.,Ltd. Registration number: Y2021320010236 |