CN106411165B - Resonant inverter circuit and control method thereof - Google Patents

Resonant inverter circuit and control method thereof Download PDF

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Publication number
CN106411165B
CN106411165B CN201611036015.9A CN201611036015A CN106411165B CN 106411165 B CN106411165 B CN 106411165B CN 201611036015 A CN201611036015 A CN 201611036015A CN 106411165 B CN106411165 B CN 106411165B
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voltage
signal
circuit
output
capacitor
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CN106411165A (en
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吴国勇
李光
余蓓
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Shenzhen Top Leather Technology Co Ltd
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Shenzhen Top Leather Technology Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/4815—Resonant converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a resonant inverter circuit, which comprises a full-bridge inverter circuit, a parallel resonant circuit, a rectifying circuit, a polarity inverter and a CLC low-pass filter. The full-bridge inverter circuit adopts a secondary side series-parallel resonant circuit to make the output of the secondary side series-parallel resonant circuit be a high-frequency chain, and then utilizes the polarity inverter and the CLC filter circuit to be connected with the commercial power, so that the current fed into the commercial power is a sine waveform with low distortion and the same phase with the voltage of the commercial power. The full-bridge inverter adopts variable-conduction-time variable-frequency control, and the switching frequency is changed and the conduction time is adjusted according to the output power, the alternating voltage angle and the output-input voltage ratio, so that the switching frequency is effectively reduced and the zero-current switching effect is achieved, and the aim of high conversion efficiency is fulfilled.

Description

Resonant inverter circuit and control method thereof
Technical Field
The invention relates to the technical field of photovoltaic inversion, in particular to a resonant inverter circuit and a control method thereof.
Background
In the field of photovoltaic inversion, a plurality of groups of PV modules are connected in series and in parallel to intensively generate electricity, so that the problems of shielding effect and inconvenience in maintenance are solved, and a single PV module is used as a Maximum Power Point Tracking (MPPT) mode and directly feeds electric power into commercial power, so that the shielding effect can be reduced, and the convenience in installation and maintenance is improved.
The existing single-module power generation and direct grid-connection small DC-AC inverter design ideas mainly comprise two types, one type is shown in figure 1, a two-stage inverter architecture scheme is adopted, and the scheme has the defects that two stages are high-frequency switching, the circuit is complex, the efficiency is poor, and a high-voltage electrolyte capacitor is generally needed.
In another type, as shown in fig. 2, the scheme is a single-stage current source output DC/DC converter connected in series with a power frequency switching inverter architecture, and the advantages of the scheme include: (i) the first-stage DC/DC converter provides current source output, is a high-voltage direct current-free link and can avoid a high-voltage electrolyte capacitor; (ii) the second-stage inverter adopts a low-frequency switching mode synchronous with mains supply, almost has no switching loss, has the same overall efficiency as a single-stage circuit, and (iii) the DC/DC converter simultaneously provides electrical isolation, has no problem of leakage current of positive grounding or negative grounding of a photovoltaic module, can prolong the service life of the photovoltaic module.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, a first object of the present invention is to provide a resonant inverter circuit.
A second object of the present invention is to provide a method for controlling a resonant inverter circuit.
In order to achieve the above object, a resonant inverter circuit according to an embodiment of the first aspect of the present invention includes a full-bridge inverter circuit, a parallel resonant circuit, a rectifier circuit, a polarity inverter, and a CLC low-pass filter;
the parallel resonant circuit comprises a transformer leakage inductance, a third capacitor Cz and a fourth capacitor Cp which are connected with a secondary side coil of the transformer leakage inductance in series;
the rectifying circuit comprises a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4, wherein the first diode D1 is connected with the positive end of the fourth diode D4, the second diode D2 is connected with the negative end of the third diode D3, the negative end of the first diode D1 is connected with the positive end of the second diode D2, and the negative end of the fourth diode D4 is connected with the positive end of the third diode D3;
the CLC low-pass filter comprises a first capacitor C1, a second capacitor C2 and an inductor L;
wherein the input end of the full-bridge inverter circuit is electrically connected with the photovoltaic module, the output end of the full-bridge inverter circuit is electrically connected with the primary side coil of the transformer, one end of the fourth capacitor Cp connected to the third capacitor Cz is connected to the positive terminal of the second diode D2, the other end of the fourth capacitor Cp is connected to the positive terminal of the third diode D3, the positive input terminals of the polarity inverter are electrically connected to the positive terminals of the first diode D1 and the fourth diode D4, the negative pole input end of the polarity reverser is respectively electrically connected with the negative poles of the second diode D2 and the third diode D3, the output end of the polarity reverser is connected with commercial power, the inductor is connected in series with the output end of the polarity reverser, the first capacitor C1 is connected in parallel with the input end of the polarity inverter, and the second capacitor C2 is connected in parallel with the output end of the polarity inverter;
the inverter comprises a full-bridge inverter circuit, a first control module and a second control module, wherein the first control module is used for controlling the full-bridge inverter circuit to work, the second control module is used for controlling the polarity inverter to work, and the first control module is used for calculating generated power obtained according to an alternating current sideP o And the output voltage of the photovoltaic moduleV pv And controlling the trigger signal which outputs the variable conduction time to control the full-bridge inverter circuit to work.
Preferably, the first control module comprises:
a maximum power point tracking controller for calculating the generated power according to the AC sideP o And the output voltage of the photovoltaic moduleV pv Calculating and outputting a first voltage control signalV pvr ；
A voltage controller for receiving the first voltage control signalV pvr And the output voltage of the photovoltaic moduleV pv Controlling output amplitude control signalI m ；
A current controller for controlling the current according to the current control signalI o,r And a current signal output from the rectifying circuitI o Controlling to output the second voltage control signalV fbc ；
A feedforward controller for generating a forward control signalV ffc And is in conjunction with the second voltage control signalV fbc After adding, a third control voltage signal is obtainedV con ；
Further comprises a voltage controlled oscillator and a variable on-time controller connected in sequence for controlling the on-time according to a third control voltage signalV con Obtaining a trigger signal of a full-bridge inverter circuit driving circuit;
wherein the amplitude control signalI m Multiplying by a synchronous sine wave signalV sin Is derived from the absolute value signal of the current control signalI o,r The synchronous sine wave signalV sin And the second control module controls the sending.
Preferably, the second control module comprises:
a phase locked loop for outputting the voltage according to the polarity inverterV grid Obtaining a switch control signal;
and the polarity reversing circuit is used for controlling the power frequency switching of the polarity reverser according to the switch control signal.
Preferably, the phase locked loop is further configured to reverse the output voltage of the polarity inverter according to the output voltageV grid Obtaining the synchronous sine wave signalV sin 。
Preferably, the voltage controlled oscillator includes a capacitor having charge and dischargeC t The charging and discharging circuit of (1), the charging and discharging capacitorC t Voltage ofV t A comparator is connected, and a preset reference voltage is input into the input end of the comparatorV tm And the output end of the comparator is electrically connected with the variable conduction time controller.
Preferably, the variable on-time controller includes:
a single-click circuit for generating a switch-on time according to the output signal of the amplifierT on The pulse signal of (3);
a conduction time determiner for setting the conduction time of the switchT on ；
The JK trigger is used for controlling the interactive triggering of the first half period and the second half period of the output signal of the full-bridge inverter circuit according to the output signal of the amplifier;
an SR flip-flop for generating a CLK signal for controlling a switch according to the amplifier trigger signalTo the charging and discharging capacitorC t And discharging is performed.
Preferably, the output end of the photovoltaic module is also connected with a voltage stabilizing capacitor in parallelC in 。
According to the resonant inverter circuit provided by the embodiment of the invention, the full-bridge inverter circuit is subjected to variable-conduction-time variable-frequency control, and the generated power obtained by calculation on the AC side is usedP o And the output voltage of the photovoltaic moduleV pv The switching frequency is changed and the conduction time is adjusted at the same time, so that the switching frequency is effectively reduced and the zero current switching effect is achieved, and the aim of high conversion efficiency is fulfilled. The series-parallel resonant circuit of the resonant inverter circuit also enables the circuit to have a wider input voltage range, can adapt to various modules and extend the power generation time, and increases the power generation capacity.
In order to achieve the above object, a method for controlling a resonant inverter circuit according to an embodiment of the second aspect of the present invention includes:
according to the output current of the rectification circuitI o Output voltage of a polarity inverterV grid And the output voltage of the photovoltaic moduleV pv And controlling the output of the trigger signal with variable conduction time to control the switching of the frequency of the full-bridge inverter circuit.
Preferably, the specific control steps of the frequency switching are as follows:
the method comprises the following steps: according to the output current of the rectification circuitI o Output voltage of a polarity inverterV grid And the output voltage of the photovoltaic moduleV pv Controlling to output a third control voltage signalV con ；
Step two: according to the third control voltage signalV con Controlling a current source to charge and discharge a capacitorC t Charging is carried out, the capacitorC t Voltage acrossV t Input to a comparator and a preset reference voltageV tm Comparing, when charging and discharging the capacitorC t Voltage acrossV t Up to the preset reference voltageV tm When the control generates a switch on-timeT on The pulse signal of (2) controls the state transition of a JK trigger in a driving circuit of the full-bridge inverter circuit at the same time, and realizes the interactive triggering of the first half period and the second half period of the output signal of the full-bridge inverter circuit.
Preferably, when charging and discharging the capacitorC t Voltage acrossV t Up to the preset reference voltageV tm And when the charge-discharge capacitor is charged, an SR trigger is also controlled to send out a CLK signal, and the CLK signal controls a switch to charge and discharge the charge-discharge capacitorC t And discharging, and re-entering the step two after discharging is finished.
According to the control method of the resonant inverter circuit, the full-bridge inverter circuit is subjected to variable-conduction-time variable-frequency control, and the generated power is calculated and obtained according to the alternating current sideP o And the output voltage of the photovoltaic moduleV pv The switching frequency is changed and the conduction time is adjusted at the same time, so that the switching frequency is effectively reduced and the zero current switching effect is achieved, and the aim of high conversion efficiency is fulfilled. The series-parallel resonant circuit of the resonant inverter circuit also enables the circuit to have a wider input voltage range, can adapt to various modules and extend the power generation time, and increases the power generation capacity.
Drawings
FIG. 1 is a schematic diagram of a prior art bipolar inverter circuit configuration;
FIG. 2 is a schematic diagram of a circuit structure of a single-stage current source output DC/DC converter connected in series with a power frequency switching inverter in the prior art;
fig. 3 is a schematic structural diagram of a resonant inverter circuit according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a resonant inverter circuit and a control module thereof according to the present invention;
fig. 5 is a schematic diagram of a control module of a full-bridge inverter circuit in the resonant inverter circuit according to the present invention;
FIG. 6 is a schematic diagram of the operation region on the series-parallel resonant gain curve of the resonant inverter circuit according to the present invention;
fig. 7 is a schematic diagram of the output current waveform of the full-bridge inverter circuit in the resonant inverter circuit according to the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
A user tag encoding method and a user tag encoding apparatus according to an embodiment of the present invention are described below with reference to the accompanying drawings.
Fig. 3 is a resonant inverter circuit provided in an embodiment of the present invention, which includes a full-bridge inverter circuit 200, a parallel resonant circuit 300, a rectifier circuit 400, a polarity inverter 500, and a CLC low-pass filter;
the parallel resonant circuit 300 includes a transformer leakage inductanceL r And leakage inductance of transformerL r A third capacitor Cs and a fourth capacitor Cp connected in series with the secondary winding;
the rectifying circuit 400 comprises a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4, wherein the first diode D1 is connected with the positive end of the fourth diode D4, the second diode D2 is connected with the negative end of the third diode D3, the negative end of the first diode D1 is connected with the positive end of the second diode D2, and the negative end of the fourth diode D4 is connected with the positive end of the third diode D3;
the CLC low-pass filter comprises a first capacitor C1, a second capacitor C2 and an inductor L;
wherein, the input end of the full-bridge inverter circuit 200 is electrically connected with the photovoltaic module 110, and the output end of the full-bridge inverter circuit 200 is connected with the transformer leakage inductanceL r The primary side coil is electrically connected, and one end of the fourth capacitor Cp connected with the third capacitor Cs is connected with the secondary side coilThe positive end of the second diode D2 is connected, the other end of the fourth capacitor Cp is connected with the positive end of the third diode D3, the positive input end of the polarity inverter is electrically connected with the positive ends of the first diode D1 and the fourth diode D4, respectively, the negative input end of the polarity inverter is electrically connected with the negative ends of the second diode D2 and the third diode D3, respectively, the output end of the polarity inverter 500 is connected to the commercial power 120, the inductor is connected in series with the output end of the polarity inverter 500, the first capacitor C1 is connected in parallel with the input end of the polarity inverter 500, and the second capacitor C2 is connected in parallel with the output end of the polarity inverter 500;
still including the first control module that is used for controlling full-bridge inverter circuit 200 work and be used for controlling the second control module of polarity reverser 500 work, first control module with full-bridge inverter circuit 200's control end electricity is connected, the second control module with the control end electricity of polarity reverser is connected, first control module is used for calculating the generated power who obtains according to the AC sideP o And the output voltage of the photovoltaic module 110V pv The trigger signal for controlling the output of the variable on-time controls the operation of the full-bridge inverter circuit 200.
The generated powerP o Calculated by a power calculating unit 100, the power calculating unit 100 is based on the current signal of the AC sideI o And a voltage signalV grid Calculating to obtain the generated powerP o The current signalI o I.e. the output current after rectification by the rectification circuit 400, the voltage signalV grid I.e. the output voltage of the polarity inverter.
The invention adopts the single-stage type structure, and the circuit structure adopts the inverter based on the full-bridge type inverter circuit in order to obtain higher power conveniently. In order to solve the aforementioned problem of wide voltage, the proposed full-bridge inverter circuit adopts a secondary side series and parallel resonance (series and parallel resonance) circuit to make the scheme have a wider voltage gain, the output current is high frequency resonance and the current amplitude is half sine wave, then a power frequency switching polarity inverter 500 is used to convert the output current into alternating current, and then the alternating current signal is connected to the utility power 120 through a CLC low pass filter circuit, so that the current fed into the utility power is sine wave with low distortion and the same phase as the utility power voltage.
Further, in order to reduce the cost and the circuit size, the resonant circuit 300 employs a leakage inductance component of a transformer (not shown).
In order to make the output voltage of the output end of the photovoltaic module 110 more stable, the output end of the photovoltaic module 110 is also connected in parallel with a voltage stabilizing capacitorC in 。
As shown in fig. 4, the first control module includes:
a maximum power point tracking controller 90 for calculating the generated power according to the AC sideP o And the output voltage of the photovoltaic moduleV pv Calculating and outputting a first voltage control signalV pvr ；
A voltage controller 80 for receiving the first voltage control signalV pvr And the output voltage of the photovoltaic moduleV pv Controlling output amplitude control signalI m ；
A current controller 40 for controlling the current according to the current control signalI o,r And a current signal output from the rectifying circuitI o Controlling to output the second voltage control signalV fbc ；
A feedforward controller 50 for generating a forward control signalV ffc And is in conjunction with the second voltage control signalV fbc After adding, a third control voltage signal is obtainedV con ；
Further comprising a voltage controlled oscillator 30 and a variable on-time controller 20 connected in series for generating a third control voltage signalV con Obtaining a trigger signal of the driving circuit 10 of the full-bridge inverter circuit 200;
wherein the amplitude control signalI m Multiplying by a synchronous sine wave signalV sin Is derived from the absolute value signal of the current control signalI o,r The synchronous sine wave signalV sin And the second control module controls the sending.
The second control module includes:
a phase locked loop 70 for outputting a voltage according to the polarity inverter 500V grid Obtaining a switch control signal;
and the polarity reversing circuit 60 is used for controlling the power frequency switching of the polarity reverser 500 according to the switch control signal.
In the above control scheme, the first control module finally outputs the trigger signal of the full-bridge inverter circuit 200.
The output signal of the full-bridge inverter circuit 200 finally generates a half sine wave type pulse current signal through the parallel resonant circuit 300, the half sine wave type pulse current signal is converted into an alternating current through the power frequency switching polarity reversing circuit 500, and the polarity reversing circuit 60 for controlling the polarity reversing circuit 500 obtains the synchronous sine wave signal by using the phase lock loop 70(phase lock loop)V sin In addition to providing a reference signal for generating a current command, it is also used as a control signal for judging the power frequency switching.
Referring to fig. 5, fig. 5 shows a circuit structure of a control module of a full-bridge inverter circuit in a resonant inverter circuit according to the present invention, wherein the voltage-controlled oscillator 30 includes a capacitor having charge and discharge functionsC t The charging and discharging circuit of (1), the charging and discharging capacitorC t Voltage ofV t A comparator 25 is connected, and a preset reference voltage is further input to the input end of the comparator 25V tm And the output end of the comparator is electrically connected with the variable conduction time controller.
The variable on-time controller includes:
one-click circuit 22 for generating a switch on-time based on the output signal of amplifier 25T on The pulse signal of (3);
an on-time determiner 21 for setting the on-time of the switchT on ；
The JK flip-flop 24 is configured to control the interactive triggering of the first half cycle and the second half cycle of the output signal of the full-bridge inverter circuit 200 according to the output signal of the amplifier 25;
an SR flip-flop 23 for generating a CLK signal for controlling a switch to charge and discharge the capacitor according to the trigger signal of the amplifier 25C t And discharging is performed.
In the resonant inverter circuit according to the embodiment of the present invention, the inverter input connected to the utility power supply 120 is a low-voltage dc, and the output is a high-voltage sinusoidal ac, so that when the inverter is in operation, the gain of the input voltage to the output voltage of the inverter needs to be adjusted at any time along with the angle of the ac sinusoidal wave, and a lower gain is required near the zero crossing of the ac waveform, whereas a higher gain is required near the peak of the ac waveform. The full-bridge inverter circuit of the circuit adopts a series-parallel resonant circuit, and the gain of the output voltage to the input voltage is (V o /V i ) The curve is shown in fig. 6, where there are two resonance points, one is determined by the series resonance frequency and the other is determined by the series-parallel resonance frequency, and the series-parallel resonance enables the circuit to have a wider gain range to accommodate more photovoltaic module specifications. Meanwhile, the working range of the circuit at low input voltage is increased, so that the power generation amount under low sunlight is improved. To achieve the above dc-to-ac gain requirement, as shown in the dashed square box operating region shown in fig. 6, the circuit of the present invention operates on the left side of the series resonance point, so that the gain is adjusted along with the waveform angle of the mains voltage, the operating frequency is adjusted to be higher at the high point of the mains voltage waveform to obtain higher gain, and the operating frequency is adjusted to be lower at the low point of the mains voltage waveform to reduce the gain and reduce the switching frequency to obtain higher efficiency
As shown in fig. 7, the left circuit operating at the resonance point will have Zero Current Switching (ZCS) characteristics and match the changing frequency. In order to accurately master the switching time of zero current, the frequency conversion of the invention is specially added with on-time control, so that each resonance can be completed, and each switching of the switch can achieve zero current switching to reduce the switching loss. The high frequency current waveform is then passed through a low pass filter comprising a polarity inverter 500 and C1-L-C2 to make the final current waveform fed into the commercial power a low distortion sine wave.
Further, an embodiment of the present invention also provides a control method of the resonant inverter circuit, where the control method includes:
according to the output current of the rectification circuitI o Output voltage of a polarity inverterV grid And the output voltage of the photovoltaic moduleV pv And controlling the output of the trigger signal with variable conduction time to control the switching of the frequency of the full-bridge inverter circuit.
Further, the specific control steps of the frequency switching are as follows:
the method comprises the following steps: according to the output current of the rectification circuitI o Output voltage of a polarity inverterV grid And the output voltage of the photovoltaic moduleV pv Controlling to output a third control voltage signalV con ；
Specifically, a maximum power point tracking controller 90 that uses the generated power obtained by the ac side calculationP o And the output voltage of the photovoltaic moduleV pv The current operating point on the PV curve is determined to determine the direction of the next move. The MPPT controller 90 moves the operating point by changing the voltage of the PV module 110, which generates a first voltage control signal for the voltage control loop of the intermediate PV module 110V pvr The regulated output of the voltage controller is then used to generate an amplitude control signal for the output current of the full-bridge inverter circuit of the innermost current loopI m The amplitude control signal is multiplied by the synchronous sine wave signalV sin To obtain a final current control signalI o,r . Current control signalI o,r And a current signal output from the rectifying circuitI o Comparing the first voltage with the second voltage and adjusting the second voltage by a current controller to obtain a second voltage control signalV fbc 。
In order to make the current follow its command more closely, the present control structure adds a feedforward controller 50, which utilizes the output powerP o And photovoltaic module voltageV pv Generating the forward control signalV ffc Then, the feedback control voltage is addedV fbc Adding the obtained third control voltage signalV con 。
Step two: according to the third control voltage signalV con Controlling a current source to charge and discharge a capacitorC t Charging is carried out, the voltage at two ends of the capacitorV t Is a sawtooth wave voltage which rises linearly, the capacitorC t Voltage acrossV t Input to a comparator and a preset reference voltageV tm Comparing, when charging and discharging the capacitorC t Voltage acrossV t Up to the preset reference voltageV tm When the trigger single-click circuit 22 is triggered, a switch on time is generatedT on The on-time of the pulse signal can be set by the on-time determiner. Simultaneously controlling the JK trigger 24 in the driving circuit of the full-bridge inverter circuit to change the state, so that the circuit can provide the double-end full-bridge inverter circuit for interactive triggering of the first half period and the second half period, and the conduction time in the first half period and the second half period is controlled by the circuitT on And (4) pulse determination.
Further, when the capacitor is charged and dischargedC t Voltage acrossV t Up to the preset reference voltageV tm And then, controlling an SR trigger 23 to send out a CLK signal, wherein the CLK signal controls a switch to charge and discharge the capacitorC t Discharging, and after the discharging is finished, re-entering the second step to start to charge and discharge the capacitorC t Another cycle of charging operation is performed.
Resonant inverter circuit of the embodiment of the inventionThe circuit adopts variable conduction time variable frequency control to the full-bridge inverter circuit and calculates the generated power according to the AC sideP o And the output voltage of the photovoltaic moduleV pv The switching frequency is changed and the conduction time is adjusted at the same time, so that the switching frequency is effectively reduced and the zero current switching effect is achieved, and the aim of high conversion efficiency is fulfilled. The series-parallel resonant circuit of the resonant inverter circuit also enables the circuit to have a wider input voltage range, can adapt to various modules and extend the power generation time, and increases the power generation capacity.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (6)

1. A resonant inverter circuit, characterized by: the inverter comprises a full-bridge inverter circuit, a parallel resonance circuit, a rectifying circuit, a polarity inverter and a CLC low-pass filter;
the parallel resonant circuit comprises a transformer leakage inductance, a third capacitor Cz and a fourth capacitor Cp which are connected with a secondary side coil of the transformer leakage inductance in series;
the rectifying circuit comprises a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4, wherein the first diode D1 is connected with the positive end of the fourth diode D4, the second diode D2 is connected with the negative end of the third diode D3, the negative end of the first diode D1 is connected with the positive end of the second diode D2, and the negative end of the fourth diode D4 is connected with the positive end of the third diode D3;
the CLC low-pass filter comprises a first capacitor C1, a second capacitor C2 and an inductor L;
wherein the input end of the full-bridge inverter circuit is electrically connected with a photovoltaic module, the output end of the full-bridge inverter circuit is electrically connected with the primary side coil of the transformer, one end of the fourth capacitor Cp connected to the third capacitor Cz is connected to the positive terminal of the second diode D2, the other end of the fourth capacitor Cp is connected to the positive terminal of the third diode D3, the positive input terminals of the polarity inverter are electrically connected to the positive terminals of the first diode D1 and the fourth diode D4, the negative pole input end of the polarity reverser is respectively electrically connected with the negative poles of the second diode D2 and the third diode D3, the output end of the polarity reverser is connected with commercial power, the inductor is connected in series with the output end of the polarity reverser, the first capacitor C1 is connected in parallel with the input end of the polarity inverter, and the second capacitor C2 is connected in parallel with the output end of the polarity inverter;
the inverter comprises a full-bridge inverter circuit, a first control module and a second control module, wherein the first control module is used for controlling the full-bridge inverter circuit to work, the second control module is used for controlling the polarity inverter to work, and the first control module is used for calculating generated power obtained according to an alternating current sideP o And the output voltage of the photovoltaic moduleV pv The control output variable turn-on time's trigger signal control the work of full-bridge inverter circuit, wherein, first control module includes:
a maximum power point tracking controller for calculating the generated power according to the AC sideP o And the output voltage of the photovoltaic moduleV pv Calculating and outputting a first voltage control signalV pvr ；
A voltage controller for receiving the first voltage control signalV pvr And the output voltage of the photovoltaic moduleV pv Controlling output amplitude control signalI m ；
A current controller for controlling the current according to the current control signalI o,r And a current signal output from the rectifying circuitI o Controlling to output the second voltage control signalV fbc ；
A feedforward controller for generating a forward control signalV ffc And is in conjunction with the second voltage control signalV fbc After adding, a third control voltage signal is obtainedV con ；
Further comprises the steps ofA voltage controlled oscillator and a variable on-time controller connected to receive the third control voltage signalV con Obtaining a trigger signal of a full-bridge inverter circuit driving circuit;
wherein the amplitude control signalI m Multiplying by a synchronous sine wave signalV sin Is derived from the absolute value signal of the current control signalI o,r The synchronous sine wave signalV sin The second control module controls the sending;
the second control module includes:
a phase locked loop for outputting the voltage according to the polarity inverterV grid Obtaining a switch control signal;
and the polarity reversing circuit is used for controlling the power frequency switching of the polarity reverser according to the switch control signal.
2. The resonant inverter circuit according to claim 1, wherein: the phase-locked loop is also used for outputting voltage according to the polarity reverserV grid Obtaining the synchronous sine wave signalV sin 。
3. The resonant inverter circuit according to claim 1, wherein: the voltage controlled oscillator comprises a capacitor having charge and dischargeC t The charging and discharging circuit of (1), the charging and discharging capacitorC t Voltage ofV t A comparator is connected, and a preset reference voltage is input into the input end of the comparatorV tm And the output end of the comparator is electrically connected with the variable conduction time controller.
4. The resonant inverter circuit according to claim 3, wherein: the variable on-time controller includes:
a single-click circuit for generating a switch-on time according to the output signal of the amplifierT on The pulse signal of (3);
a conduction time determiner for setting the conduction time of the switchT on ；
The JK trigger is used for controlling the interactive triggering of the first half period and the second half period of the output signal of the full-bridge inverter circuit according to the output signal of the amplifier;
an SR flip-flop for generating a CLK signal according to the amplifier trigger signal to control a switch to charge and discharge the capacitorC t And discharging is performed.
5. The resonant inverter circuit according to claim 1, wherein: the output end of the photovoltaic module is also connected with a voltage stabilizing capacitor in parallelC in 。
6. A control method of a resonant inverter circuit comprises a full-bridge inverter circuit, a parallel resonant circuit, a rectifying circuit, a polarity inverter and a CLC low-pass filter which are electrically connected in sequence; full-bridge inverter circuit is connected with photovoltaic module electricity, its characterized in that: the control method comprises the following steps:
according to the output current of the rectification circuitI o Output voltage of a polarity inverterV grid And the output voltage of the photovoltaic moduleV pv Controlling the output of the trigger signal with variable conduction time to control the switching of the frequency of the full-bridge inverter circuit, wherein the specific control steps of the frequency switching are as follows:
the method comprises the following steps: according to the output current of the rectification circuitI o Output voltage of a polarity inverterV grid And the output voltage of the photovoltaic moduleV pv Controlling to output a third control voltage signalV con ；
Step two: according to the third control voltage signalV con Controlling a current source to charge and discharge a capacitorC t Charging is carried out, the capacitorC t Voltage acrossV t Input to a comparator and a preset reference voltageV tm Comparing, when charging and discharging the capacitorC t Voltage acrossV t Up to the preset reference voltageV tm When the control generates a switch on-timeT on The pulse signal of the full-bridge inverter circuit controls the JK trigger in the driving circuit of the full-bridge inverter circuit to change the state at the same time, so that the interactive triggering of the first half period and the second half period of the output signal of the full-bridge inverter circuit is realized; when charging and discharging the capacitorC t Voltage acrossV t Up to the preset reference voltageV tm And when the charge-discharge capacitor is charged, an SR trigger is also controlled to send out a CLK signal, and the CLK signal controls a switch to charge and discharge the charge-discharge capacitorC t And discharging, and re-entering the step two after discharging is finished.
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CN103401463A (en) * 2013-07-25 2013-11-20 天津大学 Miniature photovoltaic grid-connected inverter with optimized DC (Direct Current) bus capacitor and control method
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