CN117318517A - Single-phase DC-AC inverter - Google Patents

Single-phase DC-AC inverter Download PDF

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Publication number
CN117318517A
CN117318517A CN202311135963.8A CN202311135963A CN117318517A CN 117318517 A CN117318517 A CN 117318517A CN 202311135963 A CN202311135963 A CN 202311135963A CN 117318517 A CN117318517 A CN 117318517A
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China
Prior art keywords
current
power switch
switch device
voltage
transformer
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Chinese (zh)
Inventor
陈国呈
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Shanghai Yanxin Electronic Technology Co ltd
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Shanghai Yanxin Electronic Technology Co ltd
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Priority to CN202311135963.8A priority Critical patent/CN117318517A/en
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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
    • H02M7/53—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 using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H02M1/126—Arrangements for reducing harmonics from ac input or output using passive filters
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/01—Resonant DC/DC converters
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33573—Full-bridge at primary side of an isolation transformer
    • 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
    • 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)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a single-phase DC-AC inverter, comprising: the inverter bridge is used for receiving the direct-current voltage and chopping the direct-current voltage according to a sine wave rule, and directly generating alternating voltage with fundamental wave components synchronous with the same frequency of the power grid voltage; a resonant circuit for receiving the alternating voltage generated by the inverter and converting the alternating voltage into an alternating current; a transformer for receiving the alternating current and outputting the alternating current as a high frequency alternating current; the rectifier is used for rectifying the high-frequency alternating current output by the transformer into high-frequency pulsating direct current rich in harmonic components, wherein the fundamental frequency of the high-frequency pulsating direct current is equal to the positive half frequency and the negative half frequency of the power grid frequency; and the filter is used for converting the high-frequency pulsating direct current output by the rectifier into smooth synchronous sine wave current which changes according to the power grid frequency. The switching loss of the power switching device is effectively reduced, the conversion efficiency of the inverter is obviously improved, and the electromagnetic interference EMS caused by ON/OFF of the switching device is greatly reduced. And simultaneously, the inverter is lighter.

Description

Single-phase DC-AC inverter
Technical Field
The invention relates to the technical field of inverters, in particular to a single-phase DC-AC inverter.
Background
The traditional single-phase DC-AC inverter comprises a phase-shifting full bridge, a transformer, a rectifier, a high-frequency inverter bridge and a filter. The phase-shifting full bridge converts the input direct-current voltage into alternating-current voltage through high-frequency chopping, and the voltage is isolated by a transformer and then is output to a rectifier. The rectifier rectifies the alternating voltage output by the transformer into direct voltage, the direct voltage is chopped by the high-frequency PWM of the inverter bridge, the direct voltage is converted into alternating voltage synchronous with the same frequency of the fundamental wave component of the power grid current, the fundamental wave current is formed after filtering by the filter, and the fundamental wave current is merged into the power grid or is directly used by a user.
Because the inverter uses the phase-shifting full bridge and the inversion bridge, the two-stage H bridge not only increases the cost of devices, but also increases the conduction loss of the devices and the switching loss of high-frequency chopping, and the hard switching operation also brings great electromagnetic interference EMS; the voltage output by the step-up transformer is rectified by the rectifier to form direct-current high voltage, so that the direct-current capacitor with high withstand voltage and large capacity is used as the filter capacitor for flat wave and decoupling, and the cost and the volume are both increased.
Disclosure of Invention
In order to solve the technical problems in the background technology, the invention provides a single-phase DC-AC inverter.
The invention provides a single-phase DC-AC inverter, comprising:
the inverter bridge is used for receiving the direct-current voltage and chopping the direct-current voltage according to a sine wave rule, and directly generating alternating voltage with fundamental wave components synchronous with the same frequency of the power grid voltage;
a resonant circuit for receiving the alternating voltage generated by the inverter and converting the alternating voltage into an alternating current;
a transformer for receiving the alternating current and outputting the alternating current as a high frequency alternating current;
the rectifier is used for rectifying the high-frequency alternating current output by the transformer into high-frequency pulsating direct current rich in harmonic components, wherein the fundamental frequency of the high-frequency pulsating direct current is equal to the positive half frequency and the negative half frequency of the power grid frequency;
and the filter is used for converting the high-frequency pulsating direct current output by the rectifier into smooth synchronous sine wave current which changes according to the power grid frequency.
Preferably, the method further comprises:
and the buffer is connected between the direct-current voltage source and the inverter and is used for filtering clutter.
Preferably, the method further comprises:
the current sensor is connected between the filter and the load and is used for detecting the output current of the inverter and outputting a feedback current signal;
the processor outputs 8 pulse driving signals according to the preset requirement on the output power of the DC-AC inverter after receiving the feedback current signal of the current sensor;
the 4 pulse driving signals are used for driving and controlling the inverter bridge to carry out high-frequency chopping on the direct-current voltage, and the other 4 pulse driving signals are used for driving and controlling the rectifier to carry out full-wave rectification on the high-frequency alternating-current output by the transformer 4.
Preferably, the inverter bridge comprises 4 power switching devices;
the power switch device S1 is connected with the power switch device S2 in series and then connected with the power switch device S3 and the power switch device S4 in parallel;
when the power switch device S1 and the power switch device S4 receive pulse driving signals and are simultaneously turned on, the inverter bridge chops the input direct-current voltage, and at the moment, the power switch device S1 and the power switch device S4 are turned on by Zero Current Switching (ZCS);
during the on period of the power switch devices S1 and S4, the power switch device S1 is turned off, and the turn-off of the power switch device S1 belongs to Zero Voltage Switching (ZVS) turn-off;
similarly, when the power switch device S3 and the power switch device S2 receive the pulse driving signals and are simultaneously turned on, the inverter bridge chops the input direct-current voltage, and at the moment, the S3 and the S2 are turned on by Zero Current Switching (ZCS);
during the on period of the power switching devices S3, S2, the power switching device S3 is turned off, and the turn-off of S3 belongs to Zero Voltage Switching (ZVS) turn-off.
Preferably, the resonant circuit is formed by an inductance L r1 Inductance L r2 And capacitor C r Composition;
when S1 and S4 are switched on with Zero Current Switching (ZCS), the inductor L r1 And capacitor C r Start series resonance, inductance L r1 And capacitor C r The current on the current collector is increased from 0 step by step and flows into C r The current is increased gradually from 0, C r The voltage on the capacitor gradually decreases from a negative value to 0 and then0 increases in the positive direction. When C r When the voltage on the primary winding is higher than the voltage reflected to the primary winding of the transformer by the network side voltage, the resonant circuit outputs alternating positive current to the primary winding of the transformer;
after S3 and S2 are switched on with Zero Current Switching (ZCS), inductor L r1 And capacitor C r Start series resonance, inductance L r1 And capacitor C r The current on the current collector is increased from 0 step by step and flows into C r The current is increased gradually from 0, C r The voltage gradually decreases from a positive value to 0, and then increases from 0 to a negative direction;
when C r When the voltage on the resonant circuit is larger than the voltage reflected to the primary winding of the transformer by the network side voltage, the resonant circuit outputs alternating negative current to the primary winding of the transformer.
Preferably, the transformer has three windings, wherein the primary side electrically connected to the resonant circuit is a single winding and the secondary side is a double winding;
when the power switch device S1 and the power switch device S4 work, the primary winding current of the transformer flows into the same-name end from top to bottom, and the secondary winding current flows out of the same-name end;
when the power switching device S3 and the power switching device S2 are operated, the primary winding current of the transformer flows in from the lower-side synonym terminal, and the secondary winding current flows out from the respective lower-side synonym terminals.
Preferably, the rectifier bridge consists of 4 power switching devices, and performs switching on and off at a current zero crossing point at the power grid frequency, and the power switching devices S5 and S8 are always conducted in the positive half cycle time of the output current;
when the power switching device S1 and the power switching device S4 of the inverter bridge are conducted, primary side current of the transformer flows in from the same-name end of the winding, current of the secondary side winding flows out from the same-name end, and current output by the transformer outputs forward current to the filter through the power switching device S5 and the body diode D6 of the power switching device S6;
when the power switching device S3 and the power switching device S2 of the inverter bridge are conducted, primary side current of the transformer flows in from the winding synonym end, current of the secondary side winding flows out from the synonym end, and current output by the transformer outputs forward current to the filter through the power switching device S8 and the body diode D7 of the power switching device S7;
in the negative half cycle time of the output current, the power switching devices S6 and S7 are always conducted;
when the power switching device S1 and the power switching device S4 of the inverter bridge are conducted, primary side current of the transformer flows in from the same-name end of the winding, current of the secondary side winding flows out from the same-name end, and current output by the transformer outputs negative current to the filter through the power switching device S7 and the body diode D8 of the power switching device S8;
when the power switch device S3 and the power switch device S2 of the inverter bridge are conducted, primary side current of the transformer flows in from the winding synonym end, current of the secondary side winding flows out from the synonym end, and current output by the transformer outputs negative current to the filter through the power switch device S6 and the body diode D5 of the power switch device S5.
Preferably, the filter comprises an inductance L f1 Inductance L f2 Capacitance C f Inductance L f1 Inductance L f2 Capacitance C f Forming an LCL third-order filter circuit;
when the secondary winding of the transformer 4 outputs high-frequency pulsating direct current through a rectifier, the filter absorbs and stores the output high-frequency pulsating direct current;
when the transformer stops outputting the high-frequency alternating current, the filter releases the energy stored in the filter capacitor and the inductor.
In the invention, the single-phase DC-AC inverter is provided, direct-current voltage is chopped through an inverter bridge according to a sine wave rule, and alternating voltage with fundamental wave component synchronous with the same frequency of the power grid voltage is directly generated; the alternating voltage forms alternating current after passing through a resonant circuit, and is output after being isolated by a transformer; the rectifier rectifies the high-frequency alternating current output by the transformer into high-frequency pulsating direct current which has fundamental wave frequency equal to positive half frequency and negative half frequency of the power grid frequency and is rich in harmonic components, and the high-frequency pulsating direct current passes through the filter to form synchronous sine wave current which changes according to the power grid frequency and flows into the power grid or is directly used by a user.
The inverter can realize DC-AC conversion after full-wave rectification by only using the primary inverter bridge for high-frequency chopping, and compared with the traditional single-phase DC-AC inverter, the inverter reduces the primary high-frequency inverter bridge, thereby reducing the cost of power switching devices and the switching loss and the conduction loss caused by the number of power switching devices. The power switching device of the rectifier only performs switching at the current zero crossing point at the power frequency, and the switching loss is approximately 0. The power switching device ON the inverter bridge is turned ON/OFF in a soft switching mode, so that the switching loss of the power switching device is effectively reduced, the conversion efficiency of the inverter is obviously improved, and the electromagnetic interference EMS caused by the ON/OFF of the switching device is also greatly reduced. The topological structure of the inverter does not have a high-voltage direct current bus, so that a high-voltage-resistant high-capacity direct current capacitor is not needed, the cost of the capacitor is saved, the space occupied by the high-voltage capacitor is also saved, and the inverter is lighter.
Drawings
Fig. 1 is a schematic diagram of a conventional structure of a single-phase DC-AC inverter according to the present invention;
fig. 2 is a schematic diagram of a system structure of a single-phase DC-AC inverter according to the present invention;
fig. 3 is a schematic circuit diagram of a single-phase DC-AC inverter according to the present invention;
FIG. 4 is a schematic diagram illustrating an embodiment of a resonant circuit of a single-phase DC-AC inverter according to the present invention;
fig. 5 is a schematic diagram of a filter structure of a single-phase DC-AC inverter according to an embodiment of the present invention.
Legend description:
1. a buffer; 2. an inverter bridge; 3. a resonant circuit; 4. a transformer; 5. a rectifier; 6. a filter; 7. a current sensor; 8. a processor.
Detailed Description
Referring to fig. 1-5, a single-phase DC-AC inverter according to the present invention includes:
the inverter bridge 2 is used for receiving the direct-current voltage and chopping the direct-current voltage according to a sine wave rule to directly generate alternating voltage with fundamental wave component synchronous with the same frequency of the power grid voltage;
a resonance circuit 3 for receiving the alternating voltage generated by the inverter 2 and converting the alternating voltage into an alternating current;
a transformer 4 for receiving an alternating current and outputting the alternating current as a high-frequency alternating current;
a rectifier 5 for rectifying the high-frequency alternating current outputted from the transformer 4 into a high-frequency pulsating direct current rich in harmonic components having a fundamental frequency equal to the positive half-cycle and the negative half-cycle of the grid frequency;
a filter 6 for converting the high frequency pulsating direct current output by the rectifier 5 into a smooth synchronous sine wave current varying with the grid frequency.
Specifically, as shown in fig. 2, the method further includes:
buffer 1, buffer 1 is connected between DC voltage source and inverter 2, and is used for filtering clutter.
Specifically, as shown in fig. 2, the method further includes:
a current sensor 7, the current sensor 7 is connected between the filter 6 and the load, and is used for detecting the output current of the inverter and outputting a feedback current signal;
the processor 8 outputs 8 pulse driving signals according to the preset requirement on the output power of the DC-AC inverter after receiving the feedback current signal of the current sensor 7;
the 4 pulse driving signals are used for driving and controlling the inverter bridge 2 to carry out high-frequency chopping on the direct-current voltage, and the other 4 pulse driving signals are used for driving and controlling the rectifier 5 to carry out full-wave rectification on the high-frequency alternating-current output by the transformer 4.
In this embodiment, the current sensor 7 is connected between the filter 6 and the power grid (or load), and is used for detecting the output current of the inverter, and feeding back to the processor 8 for the processor 8 to judge and process.
After receiving the feedback current signal of the current sensor 7, the processor 8 adjusts and controls the magnitude of the output current modulation signal according to the requirement on the output power of the DC-AC inverter, and outputs 8 control signals, wherein 4 power switching devices S1, S2, S3 and S4 used for driving the inverter bridge 2 realize high-frequency chopping on the DC voltage, and the other 4 signals are used for driving 4 power switching devices S5, S6, S7 and S8 of the rectifier 5 to realize full-wave rectification on the positive and negative half-cycle power frequency current output by the rectifier 4.
Specifically, as shown in fig. 2, the inverter bridge 2 includes 4 power switching devices;
the power switch device S1 is connected with the power switch device S2 in series and then connected with the power switch device S3 and the power switch device S4 in parallel;
when the power switch device S1 and the power switch device S4 receive pulse driving signals and are simultaneously turned on, the inverter bridge 2 chops the input direct-current voltage, and at the moment, the power switch device S1 and the power switch device S4 are turned on by Zero Current Switching (ZCS);
during the on period of the power switching devices S1, S4, the power switching device S1 is turned off, and the turn-off of S1 belongs to Zero Voltage Switching (ZVS) turn-off.
Similarly, when the power switch device S3 and the power switch device S2 receive the pulse driving signals and are simultaneously turned on, the inverter bridge 2 chops the input direct-current voltage, and at the moment, the S3 and the S2 are turned on by Zero Current Switching (ZCS);
when the power switch device S3 and the power switch device S2 receive the pulse driving signals and the power switch device S3 is turned off during the same time, the turn-off of the power switch device S3 belongs to zero voltage turn-on (ZVS) turn-off.
In the present embodiment, the power switching device is generally referred to as a MOSFET or an IGBT, but is not limited to both, and other power switching devices having such switching characteristics are not excluded.
In the present embodiment, before the power switch device S1 and the power switch device S4 are turned on, the state of the resonant circuit 3 is a continuous state after the power switch device S3 and the power switch device S2 are turned off, at this time L r2 And C r The current on the two electrodes being equal to zero, C r The upper voltage is negative and positive, and the power grid voltage is reflected to the amplitude of the primary winding of the transformer 4 at the moment tV P ，V P The expression of (2) is as follows:
e in the above g 、ω、θ 0 N are the effective value of the grid voltage, the angular velocity, the initial phase angle and the step-up ratio of the transformer, respectively.
When the processor 8 modulates and outputs a pulse driving signal to drive the power switching device S1 and the power switching device S4 of the inverter bridge 2 to be simultaneously turned on according to a sine wave rule, the inverter bridge 2 chops the input direct current voltage. Above V Cr The voltage passes through the power switch device S1, the power switch device S4 and the direct current voltage E dc The inductance L applied to the resonant circuit 3 after superposition r1 And capacitor C r Is of the inductance L r1 And capacitor C r Start series resonance, inductance L r1 And capacitor C r The current on the same time increases gradually from 0, so that the power switching device S1 and the power switching device S4 are turned on with ZCS at this time.
With flowing into the capacitor C r The current on the capacitor C increases gradually from 0 r The voltage on the battery also gradually goes from a negative value shown in the above formula to 0, and further increases from 0 to positive direction.
When the capacitor C r The voltage on the transformer is larger than the value of the voltage reflected to the primary winding of the transformer 4 at the moment t;
i.e.At the time point C starts to point towards the inductance L r2 And the primary winding of the transformer 4 outputs a positive current (shown from left to right) and gradually increases the capacitance C r The terminal voltage of (c) continues to rise.
According to kirchhoff's law, the inductance L is then r1 Capacitance C r Inductance L r2 The sum of the three currents must be 0. Due to inductance L r1 The current flowing from the DC side is equal to the output to the capacitor C r And inductance L r2 Is a sum of the currents of (a) and (b).
With capacitance C r Rise of terminal voltage, capacitance C r The current will gradually decrease and the inductance L r1 Shunt to inductance L r2 The upper current increases and holds the capacitor C r Current and inductance L r2 The sum of the currents on is equal to the inductance L r1 And the current on.
When the inductance L r2 The upper current increases to be equal to the inductance L r1 When current is applied, capacitor C r The current on is also reduced to 0, the capacitance C r The voltage across it peaks. When the power switch device S1 is turned off at this moment, the inter-junction capacitor C1 inside the power switch device S1 starts to charge, and the inter-junction capacitor C2 inside the power switch device S2 starts to discharge, and because the capacity of the capacitor C1 and the capacity of the capacitor C2 are very small, the turn-off of the power switch device S1 is completed in nanosecond time, so that the terminal voltage of the power switch device S1 reaches the direct-current side voltage E dc 。
At the same time, the capacitor C2 is discharged in synchronization with the capacitor C1, when the terminal voltage of the capacitor C1 is equal to the DC side voltage E dc At this time, the terminal voltage of the capacitor C2 is also equal to 0. The reverse bias voltage of the body diode D2 in the lower bridge arm power switch device S2 is also reduced to 0, so that the inductance L r1 The resonant current on the inductor L r2 The transformer primary winding, S4 and D2 are freewheeling. The switch-off of S1 is therefore ZVS switch-off.
At L r1 During the freewheel period L r2 The current on equals C r And L r1 The sum of the freewheel currents C r The terminal voltage of (2) decreases from the peak value.
At L r1 C during the gradual decrease of the discharge current r 、L r2 While resonance of L is underway r1 When the current of (C) is reduced to 0 r Is equal to L r2 Input current (i.e. primary winding of transformer), C r The voltage on it continues to drop. After that, the power switch device S4 is turned off, and ZCS turn-off of S4 can be realized.
When C r The voltage on the capacitor drops to the time tTerminal voltage of primary winding of transformerAt time C r The discharge current of (2) also falls to 0, correspondingly L r2 The current on the capacitor is also reduced to 0, C r Is embedded in the terminal voltage of the aboveNumerically, the transformer has no output, corresponding to an open circuit, C r 、L r2 And the resonance of (c) ends.
Specifically, as shown in fig. 3 and 4, the resonant circuit 3 is composed of an inductance L r1 Inductance L r2 And capacitor C r Composition;
when S1 and S4 are switched on with Zero Current Switching (ZCS), the inductor L r1 And capacitor C r Start series resonance, inductance L r1 And capacitor C r The current on the current collector is increased from 0 step by step and flows into C r The current is increased gradually from 0, C r The voltage on the capacitor gradually decreases from a negative value to 0, and then increases from 0 to a positive direction. When C r When the voltage on it is greater than the voltage reflected by the network side voltage to the primary winding of the transformer, the resonant circuit 3 outputs an alternating positive current to the primary winding of the transformer 4.
After S3 and S2 are switched on with Zero Current Switching (ZCS), inductor L r1 And capacitor C r Start series resonance, inductance L r1 And capacitor C r The current on the current collector is increased from 0 step by step and flows into C r The current is increased gradually from 0, C r The voltage on the capacitor gradually decreases from a positive value to 0, and then increases from 0 to a negative direction. When C r When the voltage on the primary winding of the transformer is higher than the voltage reflected by the network side voltage at this time, the resonance circuit 3 outputs an alternating negative current to the primary winding of the transformer 4.
The resonant circuit 3 is L r1 -C r -L r2 The resonant circuit 3 can be constructed with L r1 -C r Structural replacement, when the resonant circuit 3 adopts L r1 -C r Structure, and L r2 By leakage inductance of the primary winding of the transformer or by leakage inductance of the primary windingThe other method is replaced.
In the present embodiment, when C r When the voltage on the primary winding of the transformer 4 is higher than the voltage value of the voltage reflected by the network side r2 Current flows from 0 upwards, due to L r2 In series with the primary winding of the transformer 4, so that the input current of the primary winding is L r2 An input current at, and is equal to L r1 Subtracting C from the current r Current on, when the secondary winding of the transformer 4 outputs positive current, C r The terminal voltage of (c) continues to rise.
When L r2 The input current at, i.e. at the primary winding of the transformer 4 being equal to L r1 At the output current of C r The input current is reduced to 0, C r The upper terminal voltage peaks. Thereafter the power switching device S1 may be turned off, it being apparent that S1 belongs to Zero Voltage Switching (ZVS) off, L r1 The current on it freewheels through D2. Thereafter, L r1 、C r 、L r2 Simultaneous resonance, C r The current on the current-supply line increases from 0 in the opposite direction to L r1 The current on the primary winding of the transformer 4 flows into the primary winding after being converged, and along with C r The current on the upper part is reversely increased, L r1 The freewheel current gradually decreases.
When C r The reverse current on is equal to L r2 At the current level, L r1 The freewheel current on drops to 0, after which the power switching device S4 can be turned off, S4 belonging to Zero Current Switching (ZCS) turn-off.
Thereafter, C r 、L r2 The resonance of (C) is completely separated from the inverter bridge r 、L r2 Forms an independent loop with the primary winding of the transformer 4, and the resonant current is such that C r The voltage on the transformer 4 is gradually reduced, when the voltage is reduced to be equal to the voltage of the voltage reflected to the primary winding of the transformer 4 at the network side, the input and output currents of the transformer 4 are stopped, the primary winding of the transformer 4, L r2 、C r The current on the current collector drops to zero, C r The voltage on is maintained at the positive voltage value of the primary winding.
When S3 and S2 are switched on with Zero Current Switching (ZCS), the operating principle of the resonant circuit 3 is the same as the above-described procedure, which is not repeated.
Specifically, as shown in fig. 3, the transformer 4 has three windings, wherein the primary side electrically connected to the resonant circuit 3 is a single winding, and the secondary side is a double winding;
when the power switch device S1 and the power switch device S4 work, the primary winding current of the transformer 4 flows into the same-name end from top to bottom, and the secondary winding current flows out of the same-name end;
when the power switching device S3 and the power switching device S2 are operated, the primary winding current of the transformer 4 flows in from the lower-side synonym terminal, and the secondary winding current flows out from the respective lower-side synonym terminals.
And the transformer 4 is used for receiving the high-frequency alternating current of the resonant circuit and outputting the high-frequency alternating current to the rectifier bridge.
Specifically, as shown in fig. 3, the rectifier bridge 5 is composed of 4 power switching devices, and performs switching at a current zero crossing point according to the power grid frequency, and in the positive half cycle time of the output current, the power switching devices S5 and S8 are always turned on;
when the power switch device S1 and the power switch device S4 of the inverter bridge 2 are conducted, primary side current of the transformer 4 flows in from the same-name end of the winding, current of the secondary side winding flows out from the same-name end, and current output by the transformer 4 outputs forward current to the filter 6 through the power switch device S5 and the body diode D6 of the power switch device S6;
when the power switch device S3 and the power switch device S2 of the inverter bridge 2 are conducted, primary side current of the transformer 4 flows in from a winding synonym end, current of a secondary side winding flows out from the synonym end, and current output by the transformer 4 outputs forward current to the filter 6 through the power switch device S8 and the body diode D7 of the power switch device S7;
in the negative half cycle time of the output current, the power switching devices S6 and S7 are always conducted;
when the power switch device S1 and the power switch device S4 of the inverter bridge 2 are conducted, primary side current of the transformer 4 flows in from the same-name end of the winding, current of the secondary side winding flows out from the same-name end, and current output by the transformer 4 outputs negative current to the filter through the power switch device S7 and the body diode D8 of the power switch device S8;
when the power switching device S3 and the power switching device S2 of the inverter bridge 2 are turned on, the primary side current of the transformer 4 flows in from the winding synonym end, the current of the secondary side winding flows out from the synonym end, and the current output by the transformer 4 outputs negative current to the filter through the power switching device S6 and the body diode D5 of the power switching device S5.
In this embodiment, the rectifier bridge 5 is composed of 4 power switching devices and performs switching at the zero crossing point of the current at the grid frequency, so that the switching loss is approximately 0.
In the positive half cycle time of the output current, the power switching devices S5 and S8 are always conducted; during the negative half cycle of the output current, the power switching devices S6, S7 are always on.
In the positive half cycle time of the output current, when the S1 and the S4 of the inverter bridge 2 are conducted, the primary side current of the transformer 4 flows in from the same-name end of the winding, and the current of the secondary side winding flows out from the same-name end. Wherein the current of the upper winding passes through the power switch device S5, the diode D6 (the body diode of S6), the filter capacitor C f And a filter inductance L connected in parallel therewith f1 、L f2 The grid (or load) then returns to the middle common of the secondary winding, i.e., outputs forward current to the filter. However, since D7 (the body diode of S7) is reverse biased, the lower winding of the secondary side of the transformer 4 has no current output.
Conversely, when the inverter bridge 2 is turned on at S3 and S2, the primary current of the transformer 4 flows in from the winding opposite end, the current of the secondary winding flows out from the opposite end, and at this time, the current of the lower winding flows through the power switch device S8, the diode D7 (the body diode of S7), and the filter capacitor C f And a filter inductance L connected in parallel therewith f2 、L f1 The grid (or load) then returns to the middle common of the secondary winding, which also outputs forward current to the filter 6. However, since D6 (the body diode of S6) is reverse biased, the upper winding on the secondary side of the transformer 4 has no current output.
It can be seen that during the positive half cycle, the current of the secondary winding of the transformer flows in from the upper terminal of the filter 6 and flows out from the lower terminal, and the filter 6 outputs a smooth sine wave current with positive half cycle.
Similarly, in the negative half cycle time of the output current, when the S1 and S4 of the inverter bridge 2 are conducted, the primary side current of the transformer 4 flows in from the same-name end of the winding, the current of the secondary side winding flows out from the same-name end, the current of the lower winding flows out from the same-name end, namely the middle common end of the secondary side winding, and the current flows out from the filter capacitor C f And a filter inductance L connected in parallel therewith f2 、L f1 The grid (or load) and the power switching device S7, the diode D8 (the body diode of S8) then return to the synonym end of the lower winding, i.e. output a negative current to the filter 6.
But the upper winding of the transformer 4 has no current output since D5 (the body diode of S5) is reverse biased.
Conversely, when the S3 and S2 of the inverter bridge 2 are conducted, the primary current of the transformer 4 flows in from the winding opposite-name end, the current of the secondary winding flows out from the opposite-name end, and at the moment, the current of the winding on the secondary side flows out from the middle common end of the secondary winding and passes through the filter capacitor C f And a filter inductance L connected in parallel therewith f2 、L f1 The power grid (or load) and the power switch device S6, the diode D5 (the body diode of S5) return to the same-name end of the upper winding, and negative current is output to the filter 6.
But the lower winding of the transformer 4 has no current output since D8 (the body diode of S8) is reverse biased.
It can be seen that during the negative half cycle time, the current of the secondary winding of the transformer 4 flows in from the lower terminal of the filter 6, and flows out from the upper terminal, and the filter 6 outputs a sine wave current with a negative half cycle.
Specifically, as shown in fig. 3 and 5, the filter 6 includes an inductance L f1 Inductance L f2 Capacitance C f Inductance L f1 Inductance L f2 Capacitance C f Forming an LCL third-order filter circuit;
when the secondary winding of the transformer 4 outputs high-frequency pulsating direct current through the rectifier 5, the filter 6 absorbs and stores the output high-frequency pulsating direct current;
when the transformer stops outputting the high frequency alternating current, the filter 6 releases the energy stored in the filter capacitor and the inductor.
In the present embodiment, the filter 6 is formed by L f1 、L f2 、C f Composition;
when the secondary winding of the transformer 4 outputs a current through the rectifier, the filter 6 is responsible for absorbing and storing the output current (including fundamental and harmonic components). Filter inductance L f1 、L f2 The counter potential direction of (C) is to resist the increase of the inductor current, so that the output current will have a small fluctuation in a short time but still be at the output current, and C is to follow the increase of the output current of the transformer 4 f The voltage on rises, after which L f1 、L f2 The current on it is also increasing.
When the transformer 4 stops outputting current, the output current is stored in the capacitor C f And inductance L f1 、L f2 The energy in the capacitor is released, and the output current is gradually reduced. Overall, the current output by the inverter is relatively smooth, approximating a sine wave.
In the present embodiment, the filter 6 may be C f -L f1 -L f2 The structure, filter 6 can also be C f -L f Structure is as follows.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to substitute or change the technical scheme and the inventive concept method according to the present invention within the scope of the present invention.

Claims (8)

1. A single-phase DC-AC inverter, comprising:
the inverter bridge (2) is used for receiving the direct-current voltage and chopping the direct-current voltage according to a sine wave rule, and directly generating alternating voltage with fundamental wave components synchronous with the same frequency of the power grid voltage;
a resonant circuit (3) for receiving the alternating voltage generated by the inverter (2) and converting the alternating voltage into an alternating current;
a transformer (4) for receiving an alternating current and outputting the alternating current as a high frequency alternating current;
a rectifier (5) for rectifying the high-frequency alternating current outputted by the transformer (4) into a high-frequency pulsating direct current rich in harmonic components with a fundamental frequency equal to the positive half-cycle and the negative half-cycle of the grid frequency;
and the filter (6) is used for converting the high-frequency pulsating direct current output by the rectifier (5) into smooth synchronous sine wave current which changes according to the power grid frequency.
2. The single-phase DC-AC inverter of claim 1, further comprising:
and the buffer (1) is connected between the direct-current voltage source and the inverter (2) and is used for filtering clutter.
3. The single-phase DC-AC inverter of claim 1, further comprising:
the current sensor (7) is connected between the filter (6) and the load and is used for detecting the output current of the inverter and outputting a feedback current signal;
the processor (8) receives the feedback current signal of the current sensor (7) and outputs 8 pulse driving signals according to the preset requirement on the output power of the DC-AC inverter;
the 4 pulse driving signals are used for driving and controlling the inverter bridge (2) to carry out high-frequency chopping on the direct-current voltage, and the other 4 pulse driving signals are used for driving and controlling the rectifier (5) to carry out full-wave rectification on the high-frequency alternating-current output by the transformer 4.
4. A single-phase DC-AC inverter according to claim 3, characterized in that the inverter bridge (2) comprises 4 power switching devices;
the power switch device S1 is connected with the power switch device S2 in series and then connected with the power switch device S3 and the power switch device S4 in parallel;
when the power switch device S1 and the power switch device S4 receive pulse driving signals and are simultaneously turned on, the inverter bridge (2) chops the input direct-current voltage, and at the moment, the power switch device S1 and the power switch device S4 are turned on by Zero Current Switching (ZCS);
during the on period of the power switch devices S1 and S4, the power switch device S1 is turned off, and the turn-off of the power switch device S1 belongs to Zero Voltage Switching (ZVS) turn-off;
similarly, when the power switch device S3 and the power switch device S2 receive pulse driving signals and are simultaneously turned on, the inverter bridge (2) chops the input direct-current voltage, and at the moment, the power switch device S3 and the power switch device S2 are turned on by Zero Current Switching (ZCS);
during the on period of the power switching devices S3, S2, the power switching device S3 is turned off, and the turn-off of S3 belongs to Zero Voltage Switching (ZVS) turn-off.
5. Single-phase DC-AC inverter according to claim 4, characterized in that the resonant circuit (3) is formed by an inductance L r1 Inductance L r2 And capacitor C r Composition;
when S1 and S4 are switched on with Zero Current Switching (ZCS), the inductor L r1 And capacitor C r Start series resonance, inductance L r1 And capacitor C r The current on the current collector is increased from 0 step by step and flows into C r The current is increased gradually from 0, C r The voltage on the capacitor gradually decreases from a negative value to 0, and then increases from 0 to a positive direction. When C r When the voltage on the primary winding is higher than the voltage reflected to the primary winding of the transformer by the network side voltage, the resonant circuit (3) outputs alternating positive current to the primary winding of the transformer (4);
after S3 and S2 are switched on with Zero Current Switching (ZCS), inductor L r1 And capacitor C r Start series resonance, inductance L r1 And capacitor C r The current on the current collector is increased from 0 step by step and flows into C r The current is increased gradually from 0, C r The voltage gradually decreases from a positive value to 0, and then increases from 0 to a negative direction;
when C r When the voltage on this is greater than the voltage reflected by the network side voltage to the primary winding of the transformer,the resonant circuit (3) outputs an alternating negative current to the primary winding of the transformer (4).
6. The single-phase DC-AC inverter according to claim 5, characterized in that the transformer (4) has three windings, wherein the primary side electrically connected to the resonant circuit (3) is a single winding and the secondary side is a double winding;
when the power switch device S1 and the power switch device S4 work, the primary side winding current of the transformer (4) flows into the same-name end from top to bottom, and the secondary side winding current flows out of the same-name end;
when the power switching device S3 and the power switching device S2 are operated, the primary winding current of the transformer (4) flows in from the lower-side synonym terminal, and the secondary winding current flows out from the lower-side synonym terminal.
7. The single-phase DC-AC inverter according to claim 4, characterized in that the rectifier bridge (5) consists of 4 power switching devices and performs switching at the current zero crossing at the grid frequency, and in the positive half cycle time of the output current, the power switching devices S5, S8 are always on;
when the power switch device S1 and the power switch device S4 of the inverter bridge (2) are conducted, primary side current of the transformer (4) flows in from the same-name end of the winding, current of the secondary side winding flows out from the same-name end, and current output by the transformer (4) outputs forward current to the filter (6) through the power switch device S5 and the body diode D6 of the power switch device S6;
when the power switch device S3 and the power switch device S2 of the inverter bridge (2) are conducted, primary side current of the transformer (4) flows in from a winding synonym end, current of a secondary side winding flows out from the synonym end, and current output by the transformer (4) outputs forward current to the filter (6) through the power switch device S8 and the body diode D7 of the power switch device S7;
in the negative half cycle time of the output current, the power switching devices S6 and S7 are always conducted;
when the power switch device S1 and the power switch device S4 of the inverter bridge (2) are conducted, primary side current of the transformer (4) flows in from the same-name end of the winding, current of the secondary side winding flows out from the same-name end, and current output by the transformer (4) outputs negative current to the filter through the power switch device S7 and the body diode D8 of the power switch device S8;
when the power switch device S3 and the power switch device S2 of the inverter bridge (2) are conducted, primary side current of the transformer (4) flows in from a winding synonym end, current of a secondary side winding flows out from the synonym end, and current output by the transformer (4) outputs negative current to the filter through the power switch device S6 and the body diode D5 of the power switch device S5.
8. Single-phase DC-AC inverter according to claim 6, characterized in that the filter (6) comprises an inductance L f1 Inductance L f2 Capacitance C f Inductance L f1 Inductance L f2 Capacitance C f Forming an LCL third-order filter circuit;
when the secondary winding of the transformer 4 outputs high-frequency pulsating direct current through the rectifier (5), the filter (6) absorbs and stores the output high-frequency pulsating direct current;
when the transformer stops outputting the high-frequency alternating current, the filter (6) releases the energy stored in the filter capacitor and the inductor.
CN202311135963.8A 2023-09-05 2023-09-05 Single-phase DC-AC inverter Pending CN117318517A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202311135963.8A CN117318517A (en) 2023-09-05 2023-09-05 Single-phase DC-AC inverter

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202311135963.8A CN117318517A (en) 2023-09-05 2023-09-05 Single-phase DC-AC inverter

Publications (1)

Publication Number Publication Date
CN117318517A true CN117318517A (en) 2023-12-29

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CN (1) CN117318517A (en)

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