CN109687753B - DC-AC converter - Google Patents

DC-AC converter Download PDF

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Publication number
CN109687753B
CN109687753B CN201811653346.6A CN201811653346A CN109687753B CN 109687753 B CN109687753 B CN 109687753B CN 201811653346 A CN201811653346 A CN 201811653346A CN 109687753 B CN109687753 B CN 109687753B
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diode
inductor
capacitor
switch tube
voltage
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CN109687753A (en
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阚加荣
孔德凯
董小燕
吴云亚
吴冬春
葛玉华
张守国
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Zhongtian Broadband Technology Co Ltd
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Yancheng Institute of Technology
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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
    • 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
    • H02M7/539—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 with automatic control of output wave form or frequency
    • H02M7/5395—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 with automatic control of output wave form or frequency by pulse-width modulation

Abstract

The invention discloses a direct current-alternating current conversion device which comprises an input direct current source, a direct current conversion unit, an alternating current conversion unit and a filtering unit, wherein the direct current conversion unit is used for outputting direct current bus voltage according to the direct current source, and the direct current bus voltage is higher than the voltage of the direct current source; the alternating current conversion unit receives the direct current bus voltage and converts the direct current bus voltage into alternating current voltage and alternating current; the filtering unit is used for filtering the alternating current and the ripple of the alternating voltage so as to provide smooth alternating voltage and alternating current to the load. The power conversion device of the invention enables the voltage stress of the switch tube to be smaller, and the voltage stress is less than that of the switch tube used in the traditional two-stage scheme, thereby reducing the conduction loss and the turn-off loss of the switch tube and improving the efficiency of the whole converter.

Description

DC-AC converter
Technical Field
The invention relates to the technical field of electric energy conversion, in particular to a direct current-alternating current conversion device.
Background
With the increasing emphasis on energy conservation and environmental protection at present, new energy power generation is widely applied, but due to the influence of factors such as external environment, the output voltage range of a new energy power generation system such as solar energy/wind energy is wide, and meanwhile, the electromagnetic working environment is severe, a high-efficiency and high-reliability direct current and alternating current conversion device with high boosting capacity needs to be configured, so that the output voltage of the new energy is changed into alternating current voltage with the voltage frequency meeting the requirement. The traditional DC-AC conversion circuit has the problem of bridge arm direct connection, has low reliability in an electromagnetic interference environment, needs AC output voltage lower than DC input voltage, and cannot meet the working requirements.
The existing solution is to add an ac transformer or a dc converter to a dc-ac circuit to achieve the boost function, but the ac transformer is bulky and high in cost, and the two-stage structure added with the dc converter makes the system implementation complicated and affects the efficiency, and meanwhile, the reliability of the system is not improved; the existing single-pole converter such as an impedance source converter has the boosting capacity and high reliability, but the boosting work of the converter needs to utilize the direct-connection state of a bridge arm, the current stress and the conduction loss of a switching tube are large, the system efficiency is low, and the converter is only suitable for the application occasions of three-phase alternating current output.
Disclosure of Invention
The purpose of the invention is as follows: in order to overcome the problems of the prior art described above, an object of the present invention is to provide a high-efficiency and high-reliability dc-ac converter having a boosting capability and a control method of the dc-ac converter.
The technical scheme is as follows:
a direct current and alternating current conversion device comprises a direct current power supply, a first capacitor, a second capacitor, a first inductor, a second inductor, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a seventh diode, an eighth diode, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a third inductor, a fourth inductor, a fifth inductor, a sixth inductor and a third capacitor; the positive electrode of the direct current power supply is connected with the anode of the first diode and the first end of the second inductor; the cathode of the first diode is connected with the first end of the first inductor, the second end of the first inductor is connected with the first end of the second capacitor and the anode of the second diode, and the second end of the second inductor is connected with the second end of the second capacitor, the anode of the third diode and the anode of the fourth diode; the cathode of the third diode is connected with the anode of a fifth diode, the input end of a second switching tube and the first end of a fourth inductor, the second end of the fourth inductor is connected with the first end of the third inductor and the first end of a third capacitor, the second end of the third inductor is connected with the output end of the first switching tube and the cathode of a seventh diode, the cathode of the fourth diode is connected with the anode of a sixth diode, the input end of a fourth switching tube and the first end of a sixth inductor, the second end of the sixth inductor is connected with the first end of the fifth inductor and the second end of a third capacitor, the second end of the fifth inductor is connected with the output end of the third switching tube and the cathode of an eighth diode, and the third capacitor is connected with a load in parallel; the cathode of the fifth diode, the cathode of the sixth diode and the input end of the first switching tube are connected with the input end of the third switching tube and the anode of the first capacitor, the cathode of the first capacitor is grounded, the output end of the second switching tube, the output end of the fourth switching tube, the anode of the seventh diode and the anode of the eighth diode are connected with the cathode of the direct-current power supply, and the cathode of the direct-current power supply is grounded; the direct current power supply, the first capacitor, the second capacitor, the first inductor, the second inductor, the first diode, the second diode, the third diode, the fourth diode, the fifth diode, the sixth diode, the second switch tube and the fourth switch tube form a direct current conversion unit, the fifth diode, the sixth diode, the seventh diode, the eighth diode, the first switch tube, the second switch tube, the third switch tube and the fourth switch tube form an alternating current conversion unit, and the third inductor, the fourth inductor, the fifth inductor, the sixth inductor and the third capacitor form a filtering unit; the direct current conversion unit is used for outputting direct current bus voltage according to a direct current power supply, wherein the direct current bus voltage is higher than the voltage of the direct current power supply, when at least one of the second switch tube and the fourth switch tube is conducted, the direct current power supply charges the second capacitor and the second inductor, and the second capacitor and the second inductor store energy; when the second switching tube and the fourth switching tube are both turned off, the second capacitor is connected in series with the second inductor to convert the respective stored electric energy into the first capacitor, so as to boost the voltage of the first capacitor, namely boost the voltage of the direct current bus; the alternating current conversion unit receives the direct current bus voltage and converts the direct current bus voltage into alternating current voltage and alternating current; the filtering unit is used for filtering the alternating current and the ripple waves of the alternating voltage so as to provide the smooth alternating voltage and the smooth alternating current to a load.
Further, the first switch tube and the second switch tube are conducted complementarily, and the third switch tube and the fourth switch tube are conducted complementarily.
Further, the proportional relation between the dc bus voltage and the voltage of the dc power supply is:
Figure GDA0002798919770000021
wherein, UinIs the voltage of a DC power supply, UdcIs a DC bus voltage, DdcIs the duty cycle of the dc conversion unit.
Further, the logic relationship of the driving signals of the first switching tube, the second switching tube, the third switching tube and the fourth switching tube is as follows:
Figure GDA0002798919770000031
wherein Sd1、Sd2、Sd3、Sd4Respectively the driving signals of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, SdcIs a first modulation signal, Sac1Is a second modulation signal, Sac2Is a third modulation signal.
Furthermore, the first modulation signal is a fixed pulse signal generated by intercepting a modulation wave with constant amplitude and a carrier wave; the second modulation signal is a pulse signal generated by intercepting a first sine half-wave modulation wave and a carrier wave; the third modulation signal is a pulse signal generated by intersecting a second sinusoidal half-wave modulation wave with the carrier, wherein the phase difference between the second sinusoidal half-wave modulation wave and the first sinusoidal half-wave modulation wave is 180 degrees.
Has the advantages that: compared with the prior art, the direct current-alternating current conversion device provided by the invention has the following advantages:
1) compared with the traditional two-stage structure, the device has higher direct current boosting capacity and small requirement on inductance value, and reduces the copper loss, iron loss and magnetic core loss of the inductor;
2) the direct current bus voltage is high, and the requirement on a direct current bus decoupling capacitor is lower;
3) the number of the used switching tubes is small, the stress of the switching tubes is small, and the overall efficiency of the converter is improved;
4) the switch tube has no direct connection state, and the system reliability is high.
Drawings
Fig. 1 is a circuit diagram of a dc-ac converter.
Fig. 2 is a schematic diagram of a modulation scheme of the dc-ac converter.
Fig. 3 is a schematic diagram of the driving signal generation of the switching tube of the dc-ac converter.
Fig. 4 is a schematic diagram of the input and output voltages and the dc bus side voltage of the dc-ac converter.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and examples.
The invention provides a direct current and alternating current conversion device which comprises a direct current conversion unit, an alternating current conversion unit and a filtering unit, wherein the direct current conversion unit is used for obtaining higher direct current bus voltage and reducing the requirement on decoupling capacitance of the direct current bus side.
The technical scheme of the invention is explained in detail in the following with the accompanying drawings:
as shown in fig. 1, the dc-ac conversion device includes a dc conversion unit 1, an ac conversion unit 2, and a filter unit 3. Since both a higher voltage is obtained across the first capacitor and the use of the switching tube is minimized to improve the system efficiency, the switching tubes 1 and 2 are shared without affecting the implementation of their respective functions. The DC conversion unit 1 includes an input DC power supply VinA first capacitor C1A second capacitor C2First inductance L1A second inductor L2And a first diode D1 and a second diode D2. When the first diode D1 is turned on, VinRespectively to the second inductance L2A second capacitor C2Charging; when the first switch tube S1 and the third switch tube S3 are turned on simultaneously, the first diode D1 is turned off and the second diode D2 is turned on, and the second inductor L2A second capacitor C2In series to the first capacitor C1Energy is released. A second diode D3 and a third diode D4 for turning on the second inductor L when the second switch tube S2 and the fourth switch tube S4 are turned on2A second capacitor C2Storing energy; when the second switch tube S2 and the fourth switch tube S4 are turned off, the second diode D2 provides the first capacitor C with the first capacitor C1And a charging path. Thus, the DC conversion unit converts the input voltage VinRising to a certain level, namely the first capacitor C on the side of the direct current bus1The two ends of the AC conversion unit obtain higher voltage, so that the voltage is used as an input source of the AC conversion unit and is matched with the output voltage of the AC side. The alternating current conversion unit 2 includes a first arm, a second arm, a third arm, and a fourth arm, and each arm is connected in parallel. Wherein the first bridge arm comprises a first switch tube S1 and a seventh diode D7 connected in series therewith; the second bridge arm comprises a second switching tube S2 and a fifth diode D5 connected in series with the second switching tube S2; the third bridge arm comprises a third switching tube S3 and an eighth diode D8 connected in series therewith; the fourth leg includes a fourth switch transistor S4 and a sixth diode D6 connected in series therewith. Wherein, each diode D5, D6, D7 and D8 is each inductor L3、L4、L5、L6A freewheel loop is provided. Because the diodes in the switch tube body are not beneficial to high-frequency commutation, and the conduction and turn-off loss is larger, the four diodes all adopt external diodes, such as fast recovery diodes. The alternating current conversion unit is used for converting direct current electric energy on the direct current bus side into alternating current electric energy to be output. The filter unit filters the output voltage and current of the AC conversion unit and comprises a third inductor L3A fourth inductor L4A fifth inductor L5A sixth inductor L6The four inductors can be used as filter inductors, so that the output load current is smooth, and the filter inductors have a wave smoothing function. Third capacitor C3To output the filter capacitor, the output voltage is smoothed, so that the output voltage waveform at two ends of the load is close to a sine wave.
Wherein, the first inductance L1Is connected to the cathode of a first diode D1, a first inductance L1And the anode, C of the first diode D22Are connected with each other; first inductance L2First terminal of (1) and DC power supply VinThe positive electrode of (1) is connected; first inductorL2A second terminal and a second capacitor C2Is connected with the second end of the first end; first inductance L2Are connected to the anodes of diodes D5 and D6 via diodes D3 and D4, respectively. The output ends of S1 are respectively connected with L3Is connected to the cathode of diode D7; the input end of the second switch tube S2 and the anode of D5, L4Is connected with the first end of the first connecting pipe; output terminal of S3 and L5The first end is connected with the cathode of a diode D8; s4 input terminal and L6The first end, D6 anode. Third inductance L3Second terminal and L4A second terminal connected to a third capacitor C3The first ends are connected. Fifth inductance L5Second terminal and sixth inductor L6A second terminal connected to the third capacitor C3The second ends are connected. The input ends of the first switch tube S1 and the third switch tube S3 are connected with the cathodes of D5 and D6, and are connected with the first capacitor C1Is connected to the positive pole of a first capacitor C1The negative electrode of (2) is grounded. The output ends of S2 and S4 are connected with the anodes of D7 and D8 and are connected with VinNegative electrode connected to VinThe negative electrode is grounded. Two ends of the load and a third capacitor C3The first end and the second end are respectively connected.
Compared with the traditional two-stage structure that only a single inductor is adopted at the direct current end for boosting, the direct current and alternating current conversion device of the embodiment adopts two inductors L in the direct current conversion unit1、L2And a capacitor C2. When the second switch tube S2 and the fourth switch tube S4 are turned on, the DC power supply V is inputtedinAre respectively to C2、L2Charging, L1As a resonant inductor, the inductance is small to limit the current flowing through the capacitor C2Current peak of (C)2、L2And (4) storing energy. When the second switch tube S2 and the fourth switch tube S4 are turned off, C2、L2Are connected in series and are common to the first capacitor C1Energy is released, so that higher voltage can be obtained at two ends of the first capacitor on the direct current bus side, and compared with the voltage gain of a traditional two-stage inverter bus, the voltage gain is obviously improved. In addition, the direct current and alternating current device only uses four switching tubes, the number of the switching tubes is less than that of the switching tubes used in the traditional two-stage structure, and the number of the switching tubes in the system is effectively reducedThe conduction loss and the turn-off loss of the switching tube are simple to control; compared with the traditional two-stage structure, the direct current-alternating current power conversion device can realize direct current-alternating current power conversion at the same stage, so that the output efficiency of the system is effectively improved.
In use, the dc conversion unit 1 and the ac conversion unit 2 in this example can work synchronously, and in one embodiment, the modulation mode is to control two signals, i.e. the modulation signal of the dc conversion unit 1 and the modulation signal of the ac conversion unit 2. The dc conversion unit 1 and the ac conversion unit 2 multiplex the switching tubes S2 and S4. The dc conversion unit 1 duty control signal is kept constant as shown in fig. 2. Available at a fixed voltage urdcAnd carrier ucIntercept to generate a first modulated signal SdcAs a control signal for the DC converter unit 1 at a fixed voltage urdcU is greater than or equal tocWhen S is presentdcAt a high level, at a fixed voltage urdcLess than ucWhen S is presentdcIs low. For the alternating current conversion unit, two groups of sine half waves with the phase difference of 180 degrees can be modulated by intersecting with the carrier wave to generate two groups of modulation signals. As shown in fig. 2, two sets of half-waves u are usedrac1And urac2Are respectively associated with the carrier ucIntercept to generate a second modulated signal Sac1And a third modulation signal Sac2As positive and negative half cycle control signals of the ac converting unit 2, respectively. Wherein u israc1And urac2Is 180 degrees. Half-wave sine urac1Greater than or equal to carrier ucTime of day, second modulation signal Sac1Is at a high level; otherwise, the second modulation signal Sac1Is low. Half-wave sine urac2Greater than or equal to carrier ucTime of day, third modulation signal Sac2Is at a high level; otherwise, the third modulation signal Sac2Is low.
The duty ratio signal of the direct current conversion unit keeps constant, and a modulation wave with constant amplitude can be intersected with a carrier wave to obtain a fixed pulse signal; the duty ratio signal of the alternating current conversion unit needs to change along with the sine signal, a sine half-wave modulation wave needs to be intercepted with the carrier, and then the fixed pulse signal and the sine pulse signal generate driving signals of each switching tube through a logic circuit.
According to a first modulation signal SdcA second modulation signal Sac1And a third modulation signal Sac2The driving signal of the switching tube is obtained through the output of the logic circuit, and the logic relation is shown as the formula (1). Therefore, the four switching tubes are in a high-frequency working state, harmonic components are reduced, and the output voltage waveforms at two ends of the load are closer to a sine wave. FIG. 3 is a schematic diagram of a logic circuit for generating a driving signal of a switching tube, a second modulation signal Sac1After passing through the NOT gate, the first modulation signal SdcThrough AND operation, a driving signal of a switch tube S2 is generated; the driving signal of the switch tube S2 passes through the not gate to generate the driving signal of the switch tube S1. Third modulated signal Sac2After passing through the NOT gate, the first modulation signal SdcThrough AND operation, a driving signal of a switch tube S4 is generated; the driving signal of the switch tube S4 passes through the not gate to generate the driving signal of the switch tube S3. Each driving signal drives the corresponding switch tube to realize power conversion.
Figure GDA0002798919770000061
Wherein Sd1、Sd2、Sd3、Sd4Respectively, driving signals S1, S2, S3 and S4 of the switch tubes S1, S2dcIs a first modulated signal, Sac1Is the second modulation signal, Sac2Is the third modulated signal.
According to the driving signal and the working characteristic of the switch tube of the embodiment, the following are provided:
when V isinTo C2、L2When the battery is charged,
Figure GDA0002798919770000062
when C is present2、L2When the discharge is performed in series, the discharge voltage is reduced,
uL2＝-(Uin+UC2-Udc) (3)
and obtaining the voltage gain of the direct current bus by utilizing the voltage-second balance of the inductor:
Figure GDA0002798919770000063
wherein, UC2、uL2Are respectively C2、L2Voltage across, DdcIs the duty cycle of the dc conversion unit.
In a traditional direct current-alternating current conversion circuit, only a single inductor is adopted at an input end for boosting, and the voltage gain of a direct current bus side is as follows:
Figure GDA0002798919770000064
therefore, compared with the traditional direct current-alternating current circuit, the direct current-alternating current conversion device has the advantages that the voltage on the direct current bus side is obviously improved, the problem that the gain of the direct current bus side of the traditional direct current-alternating current circuit is low is solved, the requirement on duty ratio is low, the conduction time of the switch tube is shortened, and the conduction loss of the switch tube is reduced. Traditional conversion equipment is for example two-stage type structure, and it is more than four to adopt the switch tube quantity, and this example only adopts four switch tubes to realize the electric energy conversion, and switching loss is little, has also reduced the system loss. The whole efficiency of the two-stage structure is the product of the efficiency of the direct current conversion unit and the efficiency of the alternating current conversion unit, the electric energy conversion is realized in a single stage, and the efficiency is higher than that of the two-stage structure.
In steady state, V is turned on at the positive half cycle when S1 and S4 are turned oninAre respectively to C2、L2And charging, wherein the inductor in the direct current conversion unit is in an energy storage state. A first capacitor C1Discharging, wherein the alternating current conversion unit is in an alternating current output state, the direct current and alternating current units work simultaneously in control, and S4 is conducted when the direct current conversion unit works; when the ac conversion unit is operated, S4 is also turned on. Therefore, the switching tube S4 is a common switching tube for the dc and ac conversion units. S1 is complementarily turned on with S2, and S3 is complementarily turned on with S4.
When S2, S4 are turned on, C2、L2The direct current conversion unit is still in a charging state, the direct current conversion unit is in a boosting state, and the alternating current conversion unit is in an inductive current follow current state; at this time, S2 and S4 are common switching tubes.
When S1, S3 are turned on, C2、L2Is in a discharge state. At this time C2、L2Series connection pair C1And charging, wherein the alternating current conversion unit is in an inductive current follow current state. The negative half cycle operating conditions are similar.
In the positive or negative half cycle, the inductance C2、L2Only when S1 and S3 are turned on, the discharge state is maintained, and the rest are charged. The output of the alternating current conversion unit can obtain a power frequency sinusoidal alternating current voltage at two ends of the load through the filtering unit.
According to the operating characteristics of this example, D is requireddc≥Dac(max)Wherein D isac(max)For the maximum duty ratio of the ac conversion unit, the output voltage can obtain the desired sinusoidal ac voltage according to the control logic of fig. 2 and 3, and fig. 3 shows the logic modulation diagram of the present circuit. In fig. 4, the ordinate is the dc bus voltage, the output ac voltage, and the input dc voltage in this order from top to bottom.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.

Claims (3)

1. A DC-AC converter is characterized in that: comprising a DC power supply (V)in) A first capacitor (C)1) A second capacitor (C)2) A first inductor (L)1) A second inductor (L)2) The diode comprises a first diode (D1), a second diode (D2), a third diode (D3), a fourth diode (D4), a fifth diode (D5), a sixth diode (D6), a seventh diode (D7), an eighth diode (D8), a first switch tube (S1), a second switch tube (S2), a third switch tube (S3), a fourth switch tube (S4) and a third inductor (L8)3) A fourth inductor (L)4) A fifth inductor (L)5) A sixth inductor (L)6) And a third capacitance (C)3) (ii) a The DC power supply (V)in) And an anode of the first diode (D1), a second inductor (L)2) Is connected with the first end of the first connecting pipe; the cathode of the first diode (D1) is connected with a first inductor (L)1) First terminal of (1), first inductance (L)1) Is connected to a second capacitor (C)2) A first terminal of a second diode (D2), an anode of a second inductor (L)2) Second terminal and second capacitor (C)2) The anode of the third diode (D3) and the anode of the fourth diode (D4); the cathode of the third diode is connected with the anode of the fifth diode (D5), the input end of the second switch tube (S2) and the fourth inductor (L)4) The fourth inductance (L), the first terminal of4) And said third inductance (L)3) First terminal, third capacitor (C)3) Is connected to a third inductance (L)3) Is connected with the output end of the first switch tube (S1) and the cathode of the seventh diode (D7), and the cathode of the fourth diode is connected with the anode of the sixth diode (D6), the input end of the fourth switch tube (S4) and the sixth inductor (L)6) A sixth inductance (L)6) And said fifth inductance (L)5) First terminal, third capacitor (C)3) Is connected to the second terminal of the fifth inductor (L)5) A second terminal of the third diode (D8) is connected to an output terminal of a third switching tube (S3), and a cathode of the eighth diode, and the third capacitor is connected in parallel to a load; the cathode of the second diode (D2), the cathode of the fifth diode (D5), the cathode of the sixth diode (D6), the input end of the first switching tube (S1) and the input end of the third switching tube (S3) are connected, and are connected with the first capacitor (C)1) Is connected to the positive electrode of a first capacitor (C)1) Is grounded, the output end of the second switching tube (S2), the output end of the fourth switching tube (S4), the anode of the seventh diode (D7), the anode of the eighth diode (D8) and the direct current power supply (V)in) Negative pole connected to DC power supply (V)in) The negative electrode is grounded; the DC power supply (V)in) A first capacitor (C)1) A second capacitor (C)2) A first inductor (L)1) A second inductor (L)2) A first diode (D1), a second diode (D2), a third diode (D3),A fourth diode (D4), a fifth diode (D5), a sixth diode (D6), a second switching tube (S2) and a fourth switching tube (S4) constitute a dc conversion unit, the fifth diode (D5), the sixth diode (D6), the seventh diode (D7), the eighth diode (D8), the first switching tube (S1), the second switching tube (S2), the third switching tube (S3) and the fourth switching tube (S4) constitute an ac conversion unit, and the third inductor (L4)3) A fourth inductor (L)4) A fifth inductor (L)5) A sixth inductor (L)6) And a third capacitance (C)3) Forming a filtering unit; the DC conversion unit is used for outputting a DC bus voltage according to a DC power supply, wherein the DC bus voltage is higher than the DC power supply, and when at least one of the second switch tube (S2) and the fourth switch tube (S4) is conducted, the DC power supply supplies the second capacitor (C)2) And a second inductance (L)2) Charging, the second capacitor (C)2) And a second inductance (L)2) Storing energy; when the second switch tube (S2) and the fourth switch tube (S4) are both turned off, the second capacitor (C)2) And the second inductance (L)2) In series to convert the respective stored electrical energy to the first capacitor (C)1) To boost the voltage of the first capacitor, i.e. boost the dc bus voltage; the alternating current conversion unit receives the direct current bus voltage and converts the direct current bus voltage into alternating current voltage and alternating current; the filtering unit is used for filtering ripples of the alternating current and the alternating voltage so as to provide the smooth alternating voltage and the smooth alternating current to a load; the logic relation of the driving signals of the first switching tube, the second switching tube, the third switching tube and the fourth switching tube is as follows:
Figure FDA0002798919760000021
wherein Sd1、Sd2、Sd3、Sd4Respectively the driving signals of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, SdcIs a first modulation signal, Sac1Is a second modulation signal,Sac2Is a third modulation signal; the first modulation signal is a fixed pulse signal generated by intercepting a modulation wave with constant amplitude and a carrier wave; the second modulation signal is a pulse signal generated by intercepting a first sine half-wave modulation wave and a carrier wave; the third modulation signal is a pulse signal generated by intersecting a second sinusoidal half-wave modulation wave with the carrier, wherein the phase difference between the second sinusoidal half-wave modulation wave and the first sinusoidal half-wave modulation wave is 180 degrees.
2. A dc-ac converter according to claim 1, wherein: the first switch tube (S1) and the second switch tube (S2) are conducted complementarily, and the third switch tube (S3) and the fourth switch tube (S4) are conducted complementarily.
3. A dc-ac converter according to claim 1, wherein: the proportional relation between the DC bus voltage and the voltage of the DC power supply is as follows:
Figure FDA0002798919760000022
wherein, UinIs the voltage of a DC power supply, UdcIs a DC bus voltage, DdcIs the duty cycle of the dc conversion unit.
CN201811653346.6A 2018-12-30 2018-12-30 DC-AC converter Active CN109687753B (en)

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