CN104104256A - Single-phase grid-connected inverter with active power decoupling function, and power decoupling method - Google Patents
Single-phase grid-connected inverter with active power decoupling function, and power decoupling method Download PDFInfo
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- CN104104256A CN104104256A CN201410290277.2A CN201410290277A CN104104256A CN 104104256 A CN104104256 A CN 104104256A CN 201410290277 A CN201410290277 A CN 201410290277A CN 104104256 A CN104104256 A CN 104104256A
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Abstract
The invention relates to the technical field of miniature single-phase photovoltaic grid-connected inverters, and particularly discloses a single-phase grid-connected inverter with an active power decoupling function, and a power decoupling control method of the single-phase grid-connected inverter. The inverter comprises a buck-boost converter, a single-phase two-bridge-arm inversion circuit, an alternating-current low-pass output filter circuit and an active power decoupling circuit, wherein the active power decoupling circuit is embedded into the single-phase two-bridge-arm inversion circuit to form a three-bridge-arm inversion circuit; a direct-current input source of the inverter is connected with an input end of the buck-boost converter; an input filter capacitor is connected in parallel between the direct-current input source of the inverter and the input end of the buck-boost converter; an output end of the buck-boost converter is connected with an input end of the three-bridge-arm inversion circuit; an output end of the three-bridge-arm inversion circuit is connected with an input end of the alternating-current low-pass output filter circuit; and power decoupling control is performed by a pulse width energy modulation method. The inverter can use a non-electrolytic capacitor as a decoupling capacitor and avoids an electrolytic capacitor, so that the fault interval time of the inverter is prolonged, and the reliability of a system is improved.
Description
Technical field
The present invention relates to miniature single-phase photovoltaic grid-connected inverter technical field, particularly a kind of single-phase grid-connected inverter and power decoupled control method thereof with active power decoupled function.
Background technology
House power supply is main mainly with single-phase electricity, therefore single-phase grid-connected inverter topology is widely used in familial distribution of cases formula electricity generation system.But single-phase grid-connected inverter, in meeting grid-connected requirement, can cause the input side of inverter to occur the power pulsations of twice power frequency.The pulsation of input side low frequency power can have a strong impact on direct current input source capacity usage ratio and increase total percent harmonic distortion of output grid-connected current.
In prior art, conventionally adopt the method for passive power decoupled to address this problem, pass through in the middle of direct current input source and inverter and the input filter capacitor of the United Nations General Assembly's capacitance, utilize electric capacity self-characteristic Passive intake pulsating power to realize inverter input and the instantaneous power balance of exporting, and ensure that input side direct current power is constant.Input filter capacitor capacitance is:
C＝W
store-total/(Δ∨·V
in)
Wherein, W
store-total=P
in/ ω is the gross energy of the required absorption of power decoupled, depends on direct current input side instantaneous power, therefore steady; Δ v is the peak-to-peak value of DC input voitage pulsation; V
inthe mean value of DC input voitage.Input filter capacitor also needs to reduce the pulsation of DC input voitage in complete Absorbing Fluctuation power.For obtaining more wide in range direct current input service voltage to improve direct current input capacity usage ratio, the mean value of DC input voitage should be got little as far as possible.This characteristic makes to adopt passive power decoupled method only to increase input filter capacitor capacitance, removes the power pulsations of the twice power frequency of input side by the electrochemical capacitor of large capacitance.For example, direct current input side instantaneous power is 400 watts, and DC input voitage is 96 volts, and the peak-to-peak value of DC input voitage pulsation gets 10%, and at least to select capacitance be the electrochemical capacitor of 133 millifarads to input filter capacitor.But the short feature of the mean time between failures (MTBF) of electrochemical capacitor can restrict the mean time between failures (MTBF) of inverter, thus the reliability of reduction system.
Summary of the invention
The problem to be solved in the present invention is the low defect of existing inverter power decoupled system reliability, a kind of have initiatively single-phase grid-connected inverter and the power decoupled control method of power decoupled function are provided, it can avoid using electrochemical capacitor to extend the time between failures of inverter, improves system reliability.
For achieving the above object, the technical solution adopted in the present invention is:
A kind of single-phase grid-connected inverter with active power decoupled function, it comprises buck current transformer, single-phase two brachium pontis inverter circuits, exchanges low pass output filter circuit and active power decoupling circuit, and described active power decoupling circuit embeds in described single-phase two brachium pontis inverter circuits and forms three brachium pontis inverter circuits; The direct current input source of inverter is connected with the input of described buck current transformer, an input filter capacitor in parallel therebetween, the output of described buck current transformer is connected with the input of described three brachium pontis inverter circuits, and described three brachium pontis inverter circuit outputs are connected with the input of described interchange low pass output filter circuit.
Preferably, described active power decoupling circuit comprises brachium pontis decoupling zero switching tube, lower brachium pontis decoupling zero switching tube, upper brachium pontis circuit switching pipe, lower brachium pontis circuit switching pipe, decoupling zero diode, loop diode and decoupling capacitance; The drain electrode of the drain electrode of described upper brachium pontis decoupling zero switching tube and described upper brachium pontis circuit switching pipe is connected with the negative pole end of direct current input source respectively; The negative electrode of the source electrode of described lower brachium pontis decoupling zero switching tube and described loop diode is connected with buck current transformer respectively; Decoupling capacitance one end is connected with the negative electrode of decoupling zero diode and the drain electrode of lower brachium pontis decoupling zero switching tube respectively, and the other end is connected with the drain electrode of lower brachium pontis circuit switching pipe with the source electrode of upper brachium pontis circuit switching pipe; The drain electrode of the source electrode of described upper brachium pontis decoupling zero switching tube and the anode of decoupling zero diode, lower brachium pontis decoupling zero switching tube is connected in series composition decoupling zero brachium pontis successively; The drain electrode of the source electrode of described upper brachium pontis circuit switching pipe and lower brachium pontis decoupling zero switching tube, the anode of loop diode are connected in series composition loop brachium pontis successively.
Preferably, described buck current transformer comprises buck switching tube, the first buck diode, the second buck diode and buck inductance; The drain electrode of the positive terminal of the direct current input source of inverter and the anode of the first buck diode, buck switching tube is connected in series successively; The source electrode of buck switching tube is connected with the negative electrode of the second buck diode and one end of buck inductance buck inductance respectively; The other end of buck inductance is connected with the negative pole end of direct current input source.
Preferably, described single-phase two brachium pontis inverter circuits comprise the upper brachium pontis circuit switching pipe, lower brachium pontis circuit switching pipe and the loop diode that share with active power decoupling circuit, also comprise brachium pontis polarity reversing switch pipe, lower brachium pontis polarity reversing switch pipe, upper brachium pontis polarity conversion diode and lower brachium pontis polarity conversion diode, the drain electrode of described upper brachium pontis polarity reversing switch pipe is connected with the drain electrode of described upper brachium pontis circuit switching pipe; The negative electrode of described lower brachium pontis polarity conversion diode is connected with the negative electrode of described loop diode; The source electrode of described upper brachium pontis polarity reversing switch pipe is connected in series composition polarity conversion brachium pontis successively with the anode of the anode of upper brachium pontis polarity conversion diode, the drain electrode of lower brachium pontis polarity reversing switch pipe, lower brachium pontis polarity conversion diode respectively.
Preferably, described interchange low pass output filter circuit comprises filter capacitor and the first filter inductance, one end of described the first filter inductance is connected with the negative electrode of upper brachium pontis polarity conversion diode with the drain electrode of lower brachium pontis polarity reversing switch pipe, and the other end is connected with the N end of electrical network; Or described first filter inductance one end is connected with the drain electrode of lower brachium pontis circuit switching pipe with the source electrode of upper brachium pontis circuit switching pipe, the other end is connected with the L end of electrical network, one end of described filter capacitor is connected with the source electrode of described upper brachium pontis circuit switching pipe, the drain electrode of lower brachium pontis circuit switching pipe, and the other end is connected with the negative electrode of upper brachium pontis polarity conversion diode, the drain electrode of lower brachium pontis polarity reversing switch pipe.
Preferably, described interchange low pass output filter circuit also comprises the second filter inductance, one end of described the first filter inductance is connected with the negative electrode of upper brachium pontis polarity conversion diode with the drain electrode of lower brachium pontis polarity reversing switch pipe, the other end is connected with the N end of electrical network, one end of described the second filter inductance is connected with the drain electrode of lower brachium pontis circuit switching pipe with the source electrode of upper brachium pontis circuit switching pipe, and the other end is connected with the L end of electrical network.
Preferably, described filter capacitor, input filter capacitor and decoupling capacitance are non-electrolytic capacitor.
A power decoupled control method for single-phase grid-connected inverter, adopts pulsewidth energy modulation:
By the input energy steady of inverter in the conducting unit of control switch periods of buck switching tube in control buck current transformer, realize direct current input side instantaneous power and smoothly export; According to the required output energy of inverter in the inverter input energy meter unit of calculating switch periods in unit switch periods; By control in power decoupling circuit initiatively the conducting of upper brachium pontis circuit switching pipe, lower brachium pontis circuit switching pipe in the brachium pontis of loop realize inverter energy flow to switching, reach the object of controlling inverter output energy in unit switch periods, ensure that output instantaneous power equals input direct-current instantaneous power according to the pulsation of twice power frequency and output average power; By controlling the upper brachium pontis polarity reversing switch pipe in single-phase two brachium pontis inverter circuits, lower brachium pontis polarity reversing switch pipe, offset of sinusoidal half-wave output current carries out polarity conversion according to power frequency, realizes sineization output current and injects electrical network.
Preferably, the power decoupled control method of described single-phase grid-connected inverter is: in the time that described inverter input energy in unit switch periods is greater than in unit switch periods the required output energy of inverter, described active power decoupling circuit initiatively stores unnecessary energy; The upper brachium pontis decoupling zero switching tube conducting of described inverter decoupling zero brachium pontis, lower brachium pontis decoupling zero switching tube is closed; In described inverter loop brachium pontis, upper brachium pontis circuit switching pipe is closed, the conducting of lower brachium pontis decoupling zero switching tube; In the time that described decoupling capacitance storage power reaches requirement, by described inverter loop brachium pontis switch inverter energy flow to; Described inverter loop brachium pontis coordinates polarity to change the upper brachium pontis polarity reversing switch pipe of brachium pontis, lower brachium pontis polarity reversing switch pipe forms loop to grid side energy feeding until energy is zero; In described inverter polarity Bridge arm, upper brachium pontis polarity reversing switch pipe, lower brachium pontis polarity reversing switch pipe are opened shutoff according to line voltage polarity; In the time that described inverter input energy in unit switch periods is less than in unit switch periods the required output energy of inverter, described active power decoupling circuit initiatively discharges required energy; The upper brachium pontis decoupling zero switching tube of described inverter decoupling zero brachium pontis is closed, the conducting of lower brachium pontis decoupling zero switching tube; Upper brachium pontis circuit switching pipe, the conducting of lower brachium pontis decoupling zero switching tube in described inverter loop brachium pontis, the reverse-biased shutoff of loop diode; When described decoupling capacitance releases energy while reaching requirement, the lower brachium pontis decoupling zero switching tube of described inverter decoupling zero brachium pontis turn-offs; Described inverter loop brachium pontis coordinates polarity to change the upper brachium pontis polarity reversing switch pipe of brachium pontis, lower brachium pontis polarity reversing switch pipe forms loop to grid side energy feeding until energy is zero; Upper brachium pontis polarity reversing switch pipe, lower brachium pontis polarity reversing switch pipe in described inverter polarity Bridge arm are opened shutoff according to line voltage polarity.
Preferably, in the power decoupled control method of described single-phase grid-connected inverter:
The input energy W of described inverter in k unit switch periods
infor:
The required output energy W of described inverter in k unit switch periods
outfor:
W
out＝W
in(1-cos(2ωkT
s))
The energy W of described inverter decoupling zero circuit in k unit switch periods
storefor:
W
store＝W
in-W
out＝W
in·cos(2ωkT
s)
Wherein P
infor the constant output of direct current input source; T
sfor the switch periods of described inverter; ω is electrical network angular frequency.
Single-phase grid-connected inverter and the power decoupled method thereof with active power decoupled function of the present invention, its beneficial effect is:
Initiatively store and release energy by secondary power decoupling zero circuit, thereby while realizing the AC instantaneous power twice power frequency of inverter, become and keep DC side instantaneous power level and smooth simultaneously, and make DC side instantaneous power equal AC average power under harmless system.Remove low frequency power pulsation on input filter capacitor by decoupling capacitance, reduce the requirement of input filter capacitor capacitance thereby realize.By step-up/step-down circuit, decoupling capacitance voltage Bootstrap is conducive to reduce decoupling capacitance capacitance.Because additional decoupling zero circuit and direct current input source and inverter circuit are that three ends are connected, increasing decoupling capacitance mains ripple does not affect the volt-ampere external characteristic of continuous current excitation.Therefore be also conducive to reduce decoupling capacitance capacitance by increasing decoupling capacitance mains ripple, these two characteristics make to use non-electrolytic capacitor as decoupling capacitance, avoid using electrochemical capacitor to extend the time between failures of inverter, improve the reliability of system.
Brief description of the drawings
Fig. 1 is that the embodiment of the present invention has the initiatively schematic diagram of the single-phase grid-connected inverter of power decoupled function;
Fig. 2 is the traffic coverage schematic diagram of single-phase grid-connected inverter in the next power frequency period of unity power factor that the embodiment of the present invention has a power decoupled function initiatively;
Fig. 3 is that the embodiment of the present invention has the initiatively interior switching tube on off sequence under four kinds of basic working modes of power frequency period of single-phase grid-connected inverter of power decoupled function.
Wherein:
1, buck current transformer; 11, buck switching tube; 12, the first buck diode; 13, the second buck diode; 14, buck inductance; 2, single-phase two brachium pontis inverter circuits; 21, upper brachium pontis polarity reversing switch pipe; 22, lower brachium pontis polarity reversing switch pipe; 23, upper brachium pontis polarity conversion diode; 24, lower brachium pontis polarity conversion diode; 3, exchange low pass output filter circuit; 31, filter capacitor; 32, the first filter inductance; 33, the second filter inductance; 4, active power decoupling circuit; 41, upper brachium pontis decoupling zero switching tube; 42, lower brachium pontis decoupling zero switching tube; 43, upper brachium pontis circuit switching pipe; 44, lower brachium pontis circuit switching pipe; 45, decoupling zero diode; 46, loop diode; 47, decoupling capacitance; 5, three brachium pontis inverter circuits; 6, direct current input source; 7, electrical network; 8, input filter capacitor.
Embodiment
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing, the present invention is described in further detail.
Embodiment:
Please refer to Fig. 1, the single-phase grid-connected inverter with active power decoupled function of the present invention, it comprises buck current transformer 1, single-phase two brachium pontis inverter circuits 2, exchanges low pass output filter circuit 3 and active power decoupling circuit 4, and initiatively power decoupling circuit 4 embeds in single-phase two brachium pontis inverter circuits 2 and forms three brachium pontis inverter circuits 5; The direct current input source 6 of inverter is connected with the input of buck current transformer 1, an input filter capacitor 8 in parallel therebetween, the output of buck current transformer 1 is connected with the input of three brachium pontis inverter circuits 5, three brachium pontis inverter circuit 5 outputs are connected with the input that exchanges low pass output filter circuit 3, form the circuit of single-phase grid-connected inverter.
Wherein, initiatively power decoupling circuit 4 comprises brachium pontis decoupling zero switching tube 41, lower brachium pontis decoupling zero switching tube 42, upper brachium pontis circuit switching pipe 43, lower brachium pontis circuit switching pipe 44, decoupling zero diode 45, loop diode 46 and decoupling capacitance 47; The drain electrode of the drain electrode of upper brachium pontis decoupling zero switching tube 41 and upper brachium pontis circuit switching pipe 43 is connected with the negative pole end of direct current input source 6 respectively; The negative electrode of the source electrode of lower brachium pontis decoupling zero switching tube 42 and described loop diode 46 is connected with buck current transformer 1 respectively; Decoupling capacitance 47 one end are connected with the negative electrode of decoupling zero diode 45 and the drain electrode of lower brachium pontis decoupling zero switching tube 42 respectively, and the other end is connected with the drain electrode of lower brachium pontis circuit switching pipe 44 with the source electrode of upper brachium pontis circuit switching pipe 43; The drain electrode of the source electrode of upper brachium pontis decoupling zero switching tube 41 and the anode of decoupling zero diode 45, lower brachium pontis decoupling zero switching tube 42 is connected in series composition decoupling zero brachium pontis successively; The drain electrode of the source electrode of described upper brachium pontis circuit switching pipe 43 and lower brachium pontis decoupling zero switching tube 42, the anode of loop diode 46 are connected in series composition loop brachium pontis successively.
Buck current transformer 1 comprises buck switching tube 11, the first buck diode 12, the second buck diode 13 and buck inductance 14; The drain electrode of the positive terminal of the direct current input source 6 of inverter and the anode of the first buck diode 12, buck switching tube 11 is connected in series successively; The source electrode of buck switching tube 11 is connected with the negative electrode of the second buck diode 13 and one end of buck inductance buck inductance 14 respectively; The other end of buck inductance 14 is connected with the negative pole end of direct current input source 6.
Single-phase two brachium pontis inverter circuits 2 comprise the upper brachium pontis circuit switching pipe 43, lower brachium pontis circuit switching pipe 44 and the loop diode 46 that share with active power decoupling circuit 4, also comprise brachium pontis polarity reversing switch pipe 21, lower brachium pontis polarity reversing switch pipe 22, upper brachium pontis polarity conversion diode 23 and lower brachium pontis polarity conversion diode 24, the drain electrode of upper brachium pontis polarity reversing switch pipe 21 is connected with the drain electrode of described upper brachium pontis circuit switching pipe 43; The negative electrode of described lower brachium pontis polarity conversion diode 24 is connected with the negative electrode of described loop diode 46; The source electrode of described upper brachium pontis polarity reversing switch pipe 21 is connected in series composition polarity conversion brachium pontis successively with the anode of the anode of upper brachium pontis polarity conversion diode 23, the drain electrode of lower brachium pontis polarity reversing switch pipe 22, lower brachium pontis polarity conversion diode 24 respectively.
Exchange low pass output filter circuit 3 and comprise filter capacitor 31 and the first filter inductance 32, wherein the connected mode of the first filter inductance 32 can be: first filter inductance 32 one end are connected with the negative electrode of upper brachium pontis polarity conversion diode 23 with the drain electrode of lower brachium pontis polarity reversing switch pipe 22, and the other end is connected with the N end of electrical network 7; Or one end of the first filter inductance 32 is connected with the drain electrode of lower brachium pontis circuit switching pipe 44 with the source electrode of upper brachium pontis circuit switching pipe 43, the other end is connected with the L end of electrical network 7.One end of filter capacitor 31 is connected with the source electrode of described upper brachium pontis circuit switching pipe 43, the drain electrode of lower brachium pontis circuit switching pipe 44, and the other end is connected with the negative electrode of upper brachium pontis polarity conversion diode 23, the drain electrode of lower brachium pontis polarity reversing switch pipe 22.The above-mentioned circuit that only includes a filter inductance does not illustrate in the drawings.
Can also in interchange low pass output filter circuit 3, two filter inductances be set, exchange low pass output filter circuit 3 and also comprise the second filter inductance 33, now first filter inductance 32 one end are connected with the negative electrode of upper brachium pontis polarity conversion diode 23 with the drain electrode of lower brachium pontis polarity reversing switch pipe 22, the other end is connected with the N end of electrical network 7, second filter inductance 33 one end are connected with the drain electrode of lower brachium pontis circuit switching pipe 44 with the source electrode of upper brachium pontis circuit switching pipe 43, and the other end is connected with the L end of electrical network 7.
Wherein, filter capacitor 31, input filter capacitor 8 are non-electrolytic capacitor with decoupling capacitance 47.
The above-mentioned single-phase grid-connected inverter with active power decoupled function, is the input energy steady of inverter in the conducting unit of control switch periods by controlling buck switching tube 11 in buck current transformer 1, realizes direct current input side instantaneous power and smoothly exports; According to the required output energy of inverter in the inverter input energy meter unit of calculating switch periods in unit switch periods; By control in power decoupling circuit 4 initiatively the conducting of upper brachium pontis circuit switching pipe 43, lower brachium pontis decoupling zero switching tube 42 in the brachium pontis of loop realize inverter energy flow to switching, reach the object of controlling inverter output energy in unit switch periods, ensure that output instantaneous power equals input direct-current instantaneous power according to the pulsation of twice power frequency and output average power; By controlling the upper brachium pontis polarity reversing switch pipe 21 in single-phase two brachium pontis inverter circuits 2, lower brachium pontis polarity reversing switch pipe 22, offset of sinusoidal half-wave output current carries out polarity conversion according to power frequency, realizes sineization output current and injects electrical network 7.
Specifically: in the time that described inverter input energy in unit switch periods is greater than in unit switch periods the required output energy of inverter, described active power decoupling circuit 4 initiatively stores unnecessary energy; Upper brachium pontis decoupling zero switching tube 41 conductings of described inverter decoupling zero brachium pontis, lower brachium pontis decoupling zero switching tube 42 is closed; In described inverter loop brachium pontis, upper brachium pontis circuit switching pipe 43 is closed, 42 conductings of lower brachium pontis decoupling zero switching tube; In the time that described decoupling capacitance 47 storage power reach requirement, by described inverter loop brachium pontis switch inverter energy flow to; Described inverter loop brachium pontis coordinates that polarity is changed the upper brachium pontis polarity reversing switch pipe 21 of brachium pontis, lower brachium pontis polarity reversing switch pipe 22 forms loop to grid side energy feeding until energy is zero; In described inverter polarity Bridge arm, upper brachium pontis polarity reversing switch pipe 21, lower brachium pontis polarity reversing switch pipe 22 are opened shutoff according to the polarity of voltage of electrical network 7; In the time that described inverter input energy in unit switch periods is less than in unit switch periods the required output energy of inverter, described active power decoupling circuit 4 initiatively discharges required energy; The upper brachium pontis decoupling zero switching tube 41 of described inverter decoupling zero brachium pontis is closed, 42 conductings of lower brachium pontis decoupling zero switching tube; Upper brachium pontis circuit switching pipe 43,42 conductings of lower brachium pontis decoupling zero switching tube in described inverter loop brachium pontis, the reverse-biased shutoff of loop diode 46; When described decoupling capacitance 47 releases energy while reaching requirement, the lower brachium pontis decoupling zero switching tube 42 of described inverter decoupling zero brachium pontis turn-offs; Described inverter loop brachium pontis coordinates that polarity is changed the upper brachium pontis polarity reversing switch pipe 21 of brachium pontis, lower brachium pontis polarity reversing switch pipe 22 forms loop to grid side energy feeding until energy is zero; Upper brachium pontis polarity reversing switch pipe 21, lower brachium pontis polarity reversing switch pipe 22 in described inverter polarity Bridge arm are opened shutoff according to the polarity of voltage of electrical network 7.
Illustrate: please refer to Fig. 2, in a power frequency period, (cos φ=1) sinusoidal line voltage v under unity power factor
gridcorresponding inverter output instantaneous power is Pout.
Line voltage: v
grid(t)=V
m(ω t) for sin
Power network current: i
grid(t)=I
m(ω t) for sin
Output instantaneous power: p
out(t)=v
grid(t) i
grid(t)=V
mi
m[1-cos (2 ω are t)]/2=P
av+ P
ac
Wherein V
mfor line voltage peak value; I
mfor grid-connected current peak value; ω is electrical network angular frequency; P
avfor inverter output average power; P
acfor inverter output ripple power.In the time that inverter output average power equals inverter input power and initiatively the absorbed power of power decoupling circuit 4 equals inverter output ripple power, inverter is realized input and the decoupling zero of outlet side instantaneous power.
The input energy W of inverter in k unit switch periods
infor:
The required output energy W of described inverter in k unit switch periods
outfor:
W
out＝W
in(1-cos(2ωkT
s))
Energy W in k unit switch periods moment inverter decoupling zero circuit
storefor:
Wherein P
infor the steady power output of direct current input source 6; T
sfor the switch periods of described inverter.Comparison according to input instantaneous power with output instantaneous power, a power frequency period is divided into two kinds of groundwork situations: when 1) input instantaneous power is greater than output instantaneous power, be energy storage pattern; 2) can pattern for releasing when input instantaneous power is less than output instantaneous power.According to inverter output current polarity, every kind of groundwork situation is divided into again two kinds of fundamental modes.So, be equally divided in eight intervals inverter alternation four kinds of basic working modes at a power frequency period.
Please refer to Fig. 3, in a power frequency period, initiatively power decoupled control is embodied in four kinds of inverter switching device pipe on off sequences under different basic working modes.Wherein, S0 is the buck switching tube 11 of buck current transformer 1; S1 is the upper brachium pontis circuit switching pipe 43 of loop brachium pontis; S2 is the lower brachium pontis circuit switching pipe 44 of loop brachium pontis; S3 is the upper brachium pontis polarity reversing switch pipe 21 of polarity conversion brachium pontis; S4 is the lower brachium pontis polarity reversing switch pipe 22 of property conversion brachium pontis; S5 is the upper brachium pontis decoupling zero switching tube 41 of decoupling zero brachium pontis; S6 is the lower brachium pontis decoupling zero switching tube 42 of decoupling zero brachium pontis.
In a switch periods, inverter is through the switching of four kinds of groundwork states.Input energy storage state, by the input energy steady of described inverter in the conducting control unit switch periods of control buck switching tube 11, smoothly exports thereby realize direct current input side instantaneous power.Initiatively power decoupling circuit 4 storage power states, in the time that inverter input energy in unit switch periods is greater than in unit switch periods the required output energy of inverter, initiatively power decoupling circuit 4 initiatively stores unnecessary energy.In inverter decoupling zero brachium pontis, upper brachium pontis decoupling zero switching tube 41 is open-minded, and lower brachium pontis decoupling zero switching tube 42 is closed; In inverter loop brachium pontis, upper brachium pontis circuit switching pipe 43 is closed, and lower brachium pontis circuit switching pipe 44 is open-minded.In the time that active power decoupling circuit 4 storage power reach requirement, pattern once by inverter loop brachium pontis on brachium pontis circuit switching pipe 43 open and make the reverse-biased shutoff of decoupling zero diode 45, switch inverter energy flow to; Pattern two times by brachium pontis decoupling zero switching tube 41 in inverter decoupling zero brachium pontis turn-off switch inverter energy flows to.Initiatively power decoupling circuit 4 state that releases energy, in the time that inverter input energy in unit switch periods is less than in unit switch periods the required output energy of inverter, initiatively power decoupling circuit 4 initiatively discharges required energy.In inverter decoupling zero brachium pontis, upper brachium pontis decoupling zero switching tube 41 is closed, and lower brachium pontis decoupling zero switching tube 42 is opened and made the reverse-biased shutoff of loop diode 46 in the brachium pontis of loop.When upper brachium pontis decoupling zero switching tube 41 releases energy while reaching requirement, pattern three and four times shutoffs by the lower brachium pontis decoupling zero switching tube 42 in decoupling zero brachium pontis of pattern switching inverter energy flow to, thereby reach the object of controlling inverter output energy in unit switch periods, to ensure that output instantaneous power is according to the pulsation of twice power frequency, and output average power equals input direct-current instantaneous power.
Under the active operating state of inverter, the upper brachium pontis circuit switching pipe 43 of loop brachium pontis, lower brachium pontis decoupling zero switching tube 42 form loop with upper brachium pontis polarity reversing switch pipe 21, the lower brachium pontis polarity reversing switch pipe 22 of polarity conversion brachium pontis, to AC energy feeding until energy is zero; Upper brachium pontis polarity reversing switch pipe 21 in inverter polarity Bridge arm, lower brachium pontis polarity reversing switch pipe 22 is opened shutoff according to electrical network 7 polarity of voltages.Because inverter output voltage, by electrical network 7 voltage clamps, just means that inverter keeps sineization output current to inject electrical network therefore keep output instantaneous power to equal to input instantaneous power according to the pulsation of twice power frequency and output average power.
According to the control of above-mentioned power decoupled method, can remove single-phase grid-connected inverter direct current input side twice power frequency power pulsations, and dwindle input filter capacitor value and decoupling capacitance value.
The above is the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention; can also make some improvements and modifications, these improvements and modifications are also considered as protection scope of the present invention.
Claims (10)
1. one kind has the initiatively single-phase grid-connected inverter of power decoupled function, it is characterized in that: comprise buck current transformer (1), single-phase two brachium pontis inverter circuits (2), exchange low pass output filter circuit (3) and active power decoupling circuit (4), described active power decoupling circuit (4) embeds composition three brachium pontis inverter circuits (5) in described single-phase two brachium pontis inverter circuits (2); The direct current input source (6) of inverter is connected with the input of described buck current transformer (1), an input filter capacitor in parallel (8) therebetween, the output of described buck current transformer (1) is connected with the input of described three brachium pontis inverter circuits (5), and described three brachium pontis inverter circuit (5) outputs are connected with the input of described interchange low pass output filter circuit (3).
2. there is according to claim 1 the initiatively single-phase grid-connected inverter of power decoupled function, it is characterized in that: described active power decoupling circuit (4) comprises brachium pontis decoupling zero switching tube (41), lower brachium pontis decoupling zero switching tube (42), upper brachium pontis circuit switching pipe (43), lower brachium pontis circuit switching pipe (44), decoupling zero diode (45), loop diode (46) and decoupling capacitance (47); The drain electrode of the drain electrode of described upper brachium pontis decoupling zero switching tube (41) and described upper brachium pontis circuit switching pipe (43) is connected with the negative pole end of direct current input source (6) respectively; The negative electrode of the source electrode of described lower brachium pontis decoupling zero switching tube (42) and described loop diode (46) is connected with buck current transformer (1) respectively; Decoupling capacitance (47) one end is connected with the negative electrode of decoupling zero diode (45) and the drain electrode of lower brachium pontis decoupling zero switching tube (42) respectively, and the other end is connected with the drain electrode of lower brachium pontis circuit switching pipe (44) with the source electrode of upper brachium pontis circuit switching pipe (43); The anode of the source electrode of described upper brachium pontis decoupling zero switching tube (41) and decoupling zero diode (45), the drain electrode of lower brachium pontis decoupling zero switching tube (42) are connected in series composition decoupling zero brachium pontis successively; The drain electrode of the source electrode of described upper brachium pontis circuit switching pipe (43) and lower brachium pontis decoupling zero switching tube (42), the anode of loop diode (46) are connected in series composition loop brachium pontis successively.
3. there is according to claim 1 the initiatively single-phase grid-connected inverter of power decoupled function, it is characterized in that: described buck current transformer (1) comprises buck switching tube (11), the first buck diode (12), the second buck diode (13) and buck inductance (14); The drain electrode of the positive terminal of the direct current input source (6) of inverter and the anode of the first buck diode (12), buck switching tube (11) is connected in series successively; The source electrode of buck switching tube (11) is connected with the negative electrode of the second buck diode (13) and one end of buck inductance buck inductance (14) respectively; The other end of buck inductance (14) is connected with the negative pole end of direct current input source (6).
4. there is according to claim 1 the initiatively single-phase grid-connected inverter of power decoupled function, it is characterized in that: described single-phase two brachium pontis inverter circuits (2) comprise the upper brachium pontis circuit switching pipe (43) sharing with active power decoupling circuit (4), lower brachium pontis circuit switching pipe (44) and loop diode (46), also comprise brachium pontis polarity reversing switch pipe (21), lower brachium pontis polarity reversing switch pipe (22), upper brachium pontis polarity conversion diode (23) and lower brachium pontis polarity conversion diode (24), the drain electrode of described upper brachium pontis polarity reversing switch pipe (21) is connected with the drain electrode of described upper brachium pontis circuit switching pipe (43), the negative electrode of described lower brachium pontis polarity conversion diode (24) is connected with the negative electrode of described loop diode (46), the source electrode of described upper brachium pontis polarity reversing switch pipe (21) is connected in series composition polarity conversion brachium pontis successively with the anode of the anode of upper brachium pontis polarity conversion diode (23), the drain electrode of lower brachium pontis polarity reversing switch pipe (22), lower brachium pontis polarity conversion diode (24) respectively.
5. there is according to claim 4 the initiatively single-phase grid-connected inverter of power decoupled function, it is characterized in that: described interchange low pass output filter circuit (3) comprises filter capacitor (31) and the first filter inductance (32), one end of described the first filter inductance (32) is connected with the negative electrode of upper brachium pontis polarity conversion diode (23) with the drain electrode of lower brachium pontis polarity reversing switch pipe (22), and the other end is connected with the N end of electrical network (7); Or one end of described the first filter inductance (32) is connected with the drain electrode of lower brachium pontis circuit switching pipe (44) with the source electrode of upper brachium pontis circuit switching pipe (43), the other end is connected with the L end of electrical network (7), one end of filter capacitor (31) is connected with the source electrode of described upper brachium pontis circuit switching pipe (43), the drain electrode of lower brachium pontis circuit switching pipe (44), and the other end is connected with the negative electrode of upper brachium pontis polarity conversion diode (23), the drain electrode of lower brachium pontis polarity reversing switch pipe (22).
6. there is according to claim 5 the initiatively single-phase grid-connected inverter of power decoupled function, it is characterized in that: described interchange low pass output filter circuit (3) also comprises the second filter inductance (33), one end of described the first filter inductance (32) is connected with the negative electrode of upper brachium pontis polarity conversion diode (23) with the drain electrode of lower brachium pontis polarity reversing switch pipe (22), the other end is connected with the N end of electrical network (7), one end of described the second filter inductance (33) is connected with the drain electrode of lower brachium pontis circuit switching pipe (44) with the source electrode of upper brachium pontis circuit switching pipe (43), the other end is connected with the L end of electrical network (7).
7. there is according to claim 5 the initiatively single-phase grid-connected inverter of power decoupled function, it is characterized in that: described filter capacitor (31), input filter capacitor (8) are non-electrolytic capacitor with decoupling capacitance (47).
8. a power decoupled control method for single-phase grid-connected inverter, is characterized in that, adopts pulsewidth energy modulation:
By the input energy steady of inverter in the conducting unit of control switch periods of buck switching tube (11) in control buck current transformer (1), realize direct current input side instantaneous power and smoothly export; According to the required output energy of inverter in the inverter input energy meter unit of calculating switch periods in unit switch periods;
By control in power decoupling circuit (4) initiatively the conducting of upper brachium pontis circuit switching pipe (43), lower brachium pontis circuit switching pipe (44) in the brachium pontis of loop realize inverter energy flow to switching, reach the object of controlling inverter output energy in unit switch periods, ensure that output instantaneous power equals input direct-current instantaneous power according to the pulsation of twice power frequency and output average power;
By controlling upper brachium pontis polarity reversing switch pipe (21), the lower brachium pontis polarity reversing switch pipe (22) in single-phase two brachium pontis inverter circuits (2), offset of sinusoidal half-wave output current carries out polarity conversion according to power frequency, realizes sineization output current and injects electrical network (7).
9. the power decoupled control method of single-phase grid-connected inverter according to claim 8, is characterized in that:
In the time that described inverter input energy in unit switch periods is greater than in unit switch periods the required output energy of inverter, described active power decoupling circuit (4) initiatively stores unnecessary energy; Upper brachium pontis decoupling zero switching tube (41) conducting of described inverter decoupling zero brachium pontis, lower brachium pontis decoupling zero switching tube (42) is closed; In described inverter loop brachium pontis, upper brachium pontis circuit switching pipe (43) is closed, lower brachium pontis decoupling zero switching tube (42) conducting; In the time that described decoupling capacitance (47) storage power reaches requirement, by described inverter loop brachium pontis switch inverter energy flow to; Described inverter loop brachium pontis coordinates polarity to change the upper brachium pontis polarity reversing switch pipe (21) of brachium pontis, lower brachium pontis polarity reversing switch pipe (22) forms loop to grid side energy feeding until energy is zero; In described inverter polarity Bridge arm, upper brachium pontis polarity reversing switch pipe (21), lower brachium pontis polarity reversing switch pipe (22) are opened shutoff according to the polarity of voltage of electrical network (7);
In the time that described inverter input energy in unit switch periods is less than in unit switch periods the required output energy of inverter, described active power decoupling circuit (4) initiatively discharges required energy; The upper brachium pontis decoupling zero switching tube (41) of described inverter decoupling zero brachium pontis is closed, lower brachium pontis decoupling zero switching tube (42) conducting; Upper brachium pontis circuit switching pipe (43), lower brachium pontis decoupling zero switching tube (42) conducting in described inverter loop brachium pontis, the reverse-biased shutoff of loop diode (46); When described decoupling capacitance (47) releases energy while reaching requirement, the lower brachium pontis decoupling zero switching tube (42) of described inverter decoupling zero brachium pontis turn-offs; Described inverter loop brachium pontis coordinates polarity to change the upper brachium pontis polarity reversing switch pipe (21) of brachium pontis, lower brachium pontis polarity reversing switch pipe (22) forms loop to grid side energy feeding until energy is zero; Upper brachium pontis polarity reversing switch pipe (21), lower brachium pontis polarity reversing switch pipe (22) in described inverter polarity Bridge arm are opened shutoff according to the polarity of voltage of electrical network (7).
10. the power decoupled control method of single-phase grid-connected inverter described according to Claim 8～9 any one, is characterized in that:
The input energy W of described inverter in k unit switch periods
infor:
The required output energy W of described inverter in k unit switch periods
outfor:
W
out＝W
in(1-cos(2ωkT
s))
The energy W of described inverter decoupling zero circuit in k unit switch periods
storefor:
W
store＝W
in-W
out＝W
in·cos(2ωkT
s)
Wherein P
infor the constant output of direct current input source; T
sfor the switch periods of described inverter; ω is electrical network angular frequency.
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