CN102594189A - Non-isolated direct-current converter type differential three-level inverter - Google Patents

Abstract

The invention discloses a non-isolated direct-current converter type differential three-level inverter. The circuit structure of the inverter consists of a power supply, an input filter, two bidirectional three-level direct-current converters, an output filter and an alternating current load, wherein the bidirectional three-level direct-current converters are connected in a differential way, i.e. input ends are connected in parallel and output ends are connected in series. By the inverter, the function of converting unstable and low-quality direct-current voltage into stable and high-quality sine alternating-current voltage as required can be realized. A circuit topology family of non-isolated direct-current converter type differential three-level inverters, including Boost type, Buck type, Buck-Boost type, Cuk type, Sepic type and Zeta type, is obtained by changing the type of the bidirectional three-level direct-current converters. The inverter has the characteristics of simple circuit topology, capability of adapting to wider voltage input range, bidirectional power current, single-stage conversion, small volume, light weight, low cost, simple control, high conversion rate, high load adaptability, high dynamic performance and the like, and is applied to a high-voltage input occasion.

Description

A non-isolated DC converter type differential three-level inverter

technical field

The invention belongs to the technical field of power electronic conversion, in particular to a non-isolated DC converter type differential three-level inverter.

Background technique

DC-AC inverter technology is a static converter device that uses power semiconductor devices to convert DC power into sinusoidal AC power with a fixed frequency or adjustable frequency. It is used for AC loads and is widely used in national defense, industrial and mining enterprises, and scientific research. Institutions, university laboratories and everyday life.

At present, domestic and foreign power electronics researchers mainly focus on two aspects of research on DC-AC inverters. One is the research on two-level DC-AC converters such as non-electrically isolated, low-frequency and high-frequency electrically isolated; the other is research on multi-level inverters. The multi-level inverter has the advantages of low voltage stress of the switching tube, small output voltage harmonics, and fast dynamic response. Since A.Nabae et al. proposed it in 1980, it has attracted the research interest of many scholars. Flying capacitor and cascaded multilevel inverters. However, the traditional three-level inverter can only realize the function of step-down. To realize the function of step-up or step-down, two or more stages are required, resulting in complex circuit topology, high loss and low efficiency. and other shortcomings.

S.Cuk and others proposed the Cuk DC converter inverter ("A conceptually new high-frequency switched-mode amp[Li]fier technique e[Li]minates current ripple", Proc.Fifth National So[Li]d-State Power Conversion Conf.1978, pp.G3.1～G3.22). The inverter consists of two identical Cuk DC converters whose input ends are connected in parallel and the output ends are connected in series, which can adapt to a wide voltage input range, realize single-stage power conversion, bidirectional power flow, and can realize buck-boost function. Afterwards, Ramon Caceres proposed the Boost DC converter inverter, and some other scholars also successively proposed Buck DC converter and Buck-boost DC converter inverters. Although the above inverters have many advantages, they are all Two-level inverters, and in the case of high-voltage electric energy conversion, have defects such as high switching voltage stress, high harmonic content of output voltage, large loss, and large energy storage components.

Contents of the invention

The purpose of the present invention is to provide a circuit topology that is simple, can adapt to a wide voltage input range, bidirectional power flow, single-stage conversion, small size, light weight, low cost, simple control, high conversion efficiency, and strong load adaptability. Good dynamic performance, non-isolated DC converter type differential three-level inverter suitable for high voltage input occasions.

The technical solution to realize the purpose of the present invention is: a non-isolated DC converter type differential three-level inverter, which consists of a high-voltage DC power supply, an input filter inductor, an input filter capacitor, and two identical bidirectional Composed of a three-level DC converter and an AC load; among them, the input terminals of two non-isolated bidirectional three-level DC converters are connected in parallel, and the output terminals are connected in series; the positive pole of the input high-voltage DC power supply is connected to one end of the input filter inductor, and the input filter inductor The other end of the input filter capacitor is respectively connected to two bidirectional three-level DC converters and input filter capacitors, and the other end of the input filter capacitor is respectively connected to the negative pole of the input high-voltage DC power supply and two bidirectional three-level DC converters. The input filter inductance and the input filter capacitor form an input filter, and the input filter filters the input high-voltage DC power supply; the two bidirectional three-level DC converters convert the input voltage filtered by the input filter into three Level output voltage, the first bidirectional three-level DC converter is composed of a first energy storage inductor, a first power switch tube, a second power switch tube, a third power switch tube, a fourth power switch tube, and a first equalizing clamp bit capacitor and the first output filter capacitor; the second bidirectional three-level DC converter consists of an energy storage inductance, a fifth power switch tube, a sixth power switch tube, a seventh power switch tube, an eighth power switch tube, and a second equalizer Clamp capacitor and second output filter capacitor; in a bidirectional three-level DC converter, one end of the first energy storage inductor is connected to the input filter, and the other end is connected to the first power switch tube and the third switch tube respectively. connection; the other end of the first power switch tube is connected to the second power switch tube and the first equalizing clamping capacitor respectively; the other end of the second power switch tube is connected to the fourth power switch tube, and the fourth power switch tube The other end of the first output filter capacitor is connected to the first output filter capacitor, and one end of the first output filter capacitor is connected to one end of the output AC load; in the bidirectional three-level DC converter, one end of the second energy storage inductor is connected to the input filter, and the other One end is respectively connected with the fifth power switch tube and the seventh power switch tube; the other end of the fifth power switch tube is respectively connected with the sixth power switch tube and the second equalizing clamp capacitor; the other end of the sixth power switch tube One end is connected to the input filter; the second equalizing clamp capacitor is respectively connected to the other end of the seventh power switch tube and the eighth power switch tube, and the other end of the eighth power switch tube is connected to the second output filter capacitor respectively ; One end of the second output filter capacitor is connected to the other end of the output AC load; the output of the two DC converters has the same DC bias, the same frequency, and a sinusoidal AC voltage with a phase difference of 180°, and the difference between the two is the output Voltage u ₀ .

Compared with the prior art, the present invention has significant advantages: the present invention is the basis for realizing grid-connected and reliable inversion of new energy sources such as fuel cells, storage batteries, and solar energy, and is the basis for realizing DC transmission, reactive power compensation, and active power in power systems. The basis of key technologies such as filters. Compared with the traditional three-level inverter, the non-isolated DC converter type differential three-level inverter can adapt to a wider voltage input range due to the introduction of a differential structure, and can realize single-stage step-up and step-down function, improve conversion efficiency, power density and reliability; compared with traditional two-level inverters, due to the introduction of three-level technology, this type of converter can be applied to high-voltage DC-AC conversion occasions, reducing switch stress and energy loss, and can improve the spectral characteristics of the output voltage, thereby reducing the volume and weight of the output filter and improving the quality of the output waveform. Therefore, the present invention greatly broadens the application occasions of the three-level DC-AC inverter, and has broad application prospects in high-voltage DC-AC power conversion occasions in civil, national defense, and industrial fields.

Description of drawings

Fig. 1 is a circuit structure diagram of a non-isolated DC converter type differential three-level inverter of the present invention.

Fig. 2 is a boost type topology diagram of a non-isolated direct current converter type differential three-level inverter of the present invention.

Fig. 3 is a Buck topology diagram of a non-isolated DC converter type differential three-level inverter according to the present invention.

Fig. 4 is a Buck-boost topology diagram of a non-isolated DC converter type differential three-level inverter of the present invention.

Fig. 5 is a Cuk-type topology diagram of the non-isolated DC converter type differential three-level inverter of the present invention.

Fig. 6 is a Sepic topological diagram of a non-isolated DC converter type differential three-level inverter of the present invention.

Fig. 7 is a Zeta topology diagram of the non-isolated DC converter type differential three-level inverter of the present invention.

Detailed ways

A non-isolated DC converter type differential three-level inverter of the present invention consists of a high-voltage DC power supply, an input filter, two completely identical non-isolated bidirectional three-level DC converters and an AC load connected in sequence composition. Wherein, the input ends of the two bidirectional three-level DC converters are connected in parallel, and the output ends are connected in series. It can directly convert unstable high-voltage and low-quality direct current into stable and high-quality sinusoidal alternating current, realize the function of single-stage buck-boost, reduce the number of power conversion stages, and realize the circuit structure of single-stage power conversion, that is, input high-voltage DC power supply The positive pole of U _i is connected to one end of the input filter inductor L _i , and the other end of the input filter inductor L _i is respectively connected to two non-isolated bidirectional three-level DC converters and an input filter capacitor C _i , the input filter capacitor The other end of C _i is respectively connected to the negative pole of the input high-voltage DC power supply U _i and two bidirectional three-level DC converters. The input filter inductor L _i and input filter capacitor C _i form an input filter, and the input filter Filter the input high-voltage DC power supply U _i ; the two identical non-isolated bidirectional three-level DC converters output sinusoidal AC voltages with the same DC bias, the same frequency, and a phase difference of 180°.

In the non-isolated DC converter type differential three-level inverter of the present invention, a high-voltage DC power supply U _i , an input filter, two completely identical non-isolated bidirectional three-level Boost converters and an AC load are sequentially connected Z _L is combined into a Boost circuit topology suitable for step-up DC-AC conversion occasions, that is, the positive pole of the input DC power U _i is connected to the positive pole of the input filter inductor L _i , and the negative pole of the input DC power U _i is connected to the negative pole of the input filter capacitor C _i , the source of the second power switch tube S ₁₂ and the negative pole of the first output filter capacitor C _f1 are connected and grounded; the negative pole of the input filter inductor L _i is connected to the positive pole of the first energy storage inductor L ₁ and the input filter capacitor C _i The anode of the input filter L _i and the input filter capacitor C _i form an input filter; the negative electrode of the first energy storage inductance L ₁ is connected to the drain of the first power switch tube S ₁₁ and the third power switch tube The source of S ₁₃ is connected; the drain of the third power switch S ₁₃ is respectively connected to the source of the fourth power switch S ₁₄ and the negative pole of the first equalizing clamp capacitor C _c1 ; the first power switch The source of S ₁₁ is connected to the drain of the second power switch S ₁₂ and the anode of the first equalizing clamp capacitor C _c1 ; the drain of the fourth power switch S ₁₄ is connected to the drain of the first output filter capacitor C _f1 The positive pole is connected to one end of the load Z _L , which constitutes a bidirectional three-level Boost converter; the negative pole of the input filter inductor L _i is connected to the positive pole of the second energy storage inductor L ₂ ; the second energy storage inductor L ₂ The negative pole of the fifth power switch tube _S21 is connected to the source of the seventh power switch tube _S23 ; the source of the fifth power switch tube _S21 is connected to the drain of the sixth power switch tube _S22 and the The anode of the second equalizing clamping capacitor _Cc2 is connected; the drain of the seventh power switch _S23 is connected to the source of the eighth power switch _S24 and the negative pole of the second equalizing clamping capacitor _Cc2 ; The source of the sixth power switch _S22 is respectively connected to the negative pole of the output filter capacitor C _f2 and the negative pole of the input DC power supply U _i and grounded; the drain of the eighth power switch _S24 is connected to the second output filter capacitor C _f2 The positive phase of the positive pole is connected to the other end of the load Z _L , and the above constitutes another bidirectional three-level Boost DC converter; the output filter capacitors C _f1 and C _f2 filter out the high-order harmonics in the output voltage of the three-level DC converter Wave, low-frequency sinusoidal AC voltages u _o1 and u _o2 with the same DC bias and a phase difference of 180° are obtained on both sides of the AC load, thereby obtaining a high-quality output voltage u _o .

In the non-isolated DC converter type differential three-level inverter of the present invention, a high-voltage DC power supply U _i , an input filter, two completely identical non-isolated bidirectional three-level Buck converters and an AC load are sequentially connected Z _L is combined into a Buck circuit topology suitable for step-down DC-AC conversion occasions, that is, the positive pole of the input high-voltage DC power supply U _i is connected to the positive pole of the input filter inductor L _i , and the negative pole of the input high-voltage DC power supply U _i is connected to the input filter capacitor C _i The negative pole of the fourth power switch tube _S14 and the negative pole of the first output filter capacitor C _f1 are connected and grounded; the negative pole of the input filter inductor L _i is respectively connected to the positive pole of the input filter capacitor C _i and the second power switch tube The drains of S ₁₂ are connected; the input filter inductance L _i and input filter capacitor C _i form an input filter, and the input filter filters the input high-voltage DC power supply U _i ; the source of the second power switch tube S ₁₂ Connected to the drain of the first power switch S ₁₁ and the positive pole of the first equalizing clamp capacitor C _c1 ; the source of the first power switch tube S ₁₁ and the positive pole of the first output filter inductor L _f1 , the third power switch The drain of the tube S ₁₃ is connected; the negative pole of the first flying capacitor C _c1 is connected with the source of the third power switch tube S ₁₃ and the drain of the fourth power switch tube S ₁₄ ; the first output filter inductance L _f1 The negative pole of the first output filter capacitor C _f1 is connected to one end of the load Z _L ; the above-mentioned first output filter inductor L _f1 and the first output filter capacitor C _f1 constitute an output filter circuit, which filters out the three-level output The high-order harmonics in the voltage get a high-quality sinusoidal voltage u _o1 with a DC bias; the above constitutes a bidirectional three-level Buck DC converter; the negative pole of the input filter inductor L _i and the sixth power switch tube The drains of _S22 are connected; the source of the sixth power switch _S22 is connected to the drain of the fifth power switch _S21 and the anode of the second equalizing clamp _Cc2 ; the fifth power switch _S21 The source of the seventh power switch tube _S23 is connected to the positive pole of the second output filter inductor L _f2 ; the negative pole of the second equalizing clamp capacitor _Cc2 is connected to the source of the seventh power switch tube _S23 and The drain of the eighth power switch tube _S24 is connected; the source of the eighth power switch tube _S24 is connected to the negative pole of the second output filter capacitor C _f2 and the negative pole of the DC power supply _Ui and grounded; the second output filter inductor The negative pole of L _f2 and the positive pole of the second output filter capacitor C _f2 are connected to the other end of the load Z _L ; the above-mentioned second output filter inductor L _f2 and the second output filter capacitor C _f2 constitute an output filter circuit, filtering High-order harmonics in the three-level output voltage obtain a high-quality sinusoidal voltage u _o2 with a DC bias; the above constitutes another bidirectional three-level Buck converter.

In the non-isolated DC converter type differential three-level inverter of the present invention, the high-voltage DC power supply U _i , the input filter, two completely identical non-isolated bidirectional three-level Buck-boost converters and The AC load Z _L is combined into a Buck-boost circuit topology suitable for buck-boost DC-AC conversion occasions, that is, the positive pole of the input high-voltage DC power supply U _i is connected to the positive pole of the input filter inductor L _i , and the negative pole of the input high-voltage DC power supply U _i It is connected to the negative pole of the input filter capacitor C _i , the negative pole of the first energy storage inductor _L1 and the negative pole of the first output filter capacitor C _f1 and grounded; the negative pole of the input filter inductor L _i is respectively connected to the positive pole of the input filter capacitor C _i and The drain of the second power switch tube _S12 is connected; the input filter inductor L _i and the input filter capacitor C _i form an input filter, and the input filter filters the input high-voltage DC power supply Ui; the second power switch tube S ₁₂ is connected to the drain of the first power switch tube _S12 and the positive pole of the first equalizing clamp capacitor C _c1 ; the source of the first power switch tube _S11 is connected to the third power switch tube _S13 respectively. The drain is connected to the positive pole of the first energy storage inductor _L1 ; the source of the third power switch tube _S13 is connected to the negative pole of the first equalizing clamp capacitor C _c1 and the drain of the fourth power switch tube _S14 ; The source of the fourth power switch tube S ₁₄ is connected to one end of the load Z _L with the first output filter capacitor C _f1 , and the above constitutes a bidirectional three-level Buck-boost DC converter; the input filter inductor L _i The negative pole is connected to the drain of the sixth power switch _S22 ; the source of the sixth power switch _S22 is connected to the drain of the fifth power switch _S21 and the positive pole of the second equalizing clamp capacitor _Cc2 ; The source of the fifth power switch _S21 is connected to the drain of the seventh power switch _S23 and the positive pole of the second energy storage inductance _L2 ; the negative pole of the second energy storage inductance _L2 is respectively connected to the second output filter The negative pole of the capacitor C _f2 is connected to the negative pole of the DC input power supply U _i and grounded; the negative pole of the second flying capacitor C _c2 is connected to the source of the seventh power switch _S23 and the drain of the eighth power switch _S24 connection; the source of the eighth power switch tube S ₂₄ and the positive pole of the second output filter capacitor C _f2 are connected to the other end of the load Z _L , and the above constitutes another road bidirectional three-level Buck-boost converter; the output filter Capacitors C _f1 and C _f2 filter out the high-order harmonics in the output voltage of the three-level DC converter, and obtain low-frequency sinusoidal AC voltage u _o1 , u with the same DC bias and a phase difference of 180° on both sides of the AC load _o2 , so as to obtain high-quality output voltage u _o .

In the non-isolated DC converter type differential three-level inverter of the present invention, a high-voltage DC power supply U _i , an input filter, two completely identical non-isolated bidirectional three-level Cuk converters and an AC load are sequentially connected Group Z _L synthesizes the Cuk circuit topology suitable for buck-boost DC-AC conversion occasions, that is, the positive pole of the input high-voltage DC power supply U _i is connected to the positive pole of the input filter inductor L _i , and the negative pole of the input high-voltage DC power supply U _i is connected to the input filter capacitor C The negative pole of _i , the source pole of the second power switching tube _S12 , the drain pole of the fourth power switching tube _S14 and the negative pole of the first output filter capacitor C _f1 are connected and grounded; the negative pole of the input filter inductor L _i is respectively connected to the input The positive pole of the filter capacitor C _i is connected to the positive pole of the first energy storage inductor _L1 ; the input filter inductor L _i and the input filter capacitor C _i form an input filter, and the input filter filters the input high-voltage DC power supply U _i ; The negative pole of the first energy storage inductance L ₁ is connected to the drain of the first power switch tube S ₁₁ and the positive pole of the first energy storage capacitor C ₁ ; the source of the first power switch tube S ₁₁ is connected to the first equalizing clamp The positive pole of the bit capacitor C _c1 is connected to the drain of the second power switch tube _S12 ; the negative pole of the first energy storage capacitor _C1 is connected to the source pole of the third power switch tube _S13 and the positive pole of the first output filter inductor L _f1 The negative pole of the first equalizing clamping capacitor C _c1 is connected with the drain pole of the third power switch tube S ₁₃ and the source pole of the fourth power switch tube S ₁₄ ; the negative pole of the first output filter inductor L _f1 is connected with the drain pole of the fourth power switch tube S 14 An output filter capacitor C _f1 is connected to one end of the load Z _L ; the above-mentioned first output filter inductor L _f1 and the first output filter capacitor C _f1 constitute an output filter circuit, which filters out high-order harmonics in the three-level output voltage wave, and a high-quality sinusoidal voltage u _o1 with a DC bias is obtained; the above constitutes a bidirectional three-level Cuk DC converter; the negative pole of the input filter inductor L _i is connected to the positive pole of the second energy storage inductor L ₂ ; The negative pole of the second energy storage inductance L ₂ is connected to the drain electrode of the fifth power switch tube S ₂₁ and the positive pole of the second energy storage capacitor C ₂ , and the source pole of the fifth power switch tube S ₂₁ is connected to the sixth power switch tube The drain of S ₂₂ is connected to the positive pole of the second equalizing clamp capacitor C _c2 ; the negative pole of the second energy storage capacitor C ₂ is connected to the source pole of the seventh power switch tube S ₂₃ and the positive pole of the second output filter inductor L _f2 connected; the negative pole of the second equalizing clamp capacitor _Cc2 is connected to the drain of the seventh power switch tube _S23 and the source of the eighth power switch tube _S24 ; the source of the sixth power switch tube _S22 is respectively It is connected to the drain of the eighth power switch tube _S24 , the negative pole of the second output filter capacitor C _f2 , and the negative pole of the input DC power supply _Ui and grounded; the negative pole of the second output filter inductor L _f2 is connected to the negative pole of the second output filter capacitor C The positive pole of _f2 is connected to the other end of the load Z _L ; the second output filter inductor L _f2 and the second output filter capacitor C _f2 constitutes an output filter circuit, which filters out high-order harmonics in the three-level output voltage, and obtains a high-quality sinusoidal voltage u _o2 with a DC bias; the above constitutes another bidirectional three-level Cuk converter.

In the non-isolated DC converter type differential three-level inverter of the present invention, a high-voltage DC power supply U _i , an input filter, two completely identical non-isolated bidirectional three-level Sepic converters and an AC load are sequentially connected Z _L is combined into a Sepic circuit topology suitable for buck-boost DC-AC conversion occasions, that is, the positive pole of the input high-voltage DC power supply U _i is connected to the positive pole of the input filter inductor L _i , and the negative pole of the input high-voltage DC power supply U _i is connected to the input filter capacitor C The negative pole of _i , the source pole of the second power switch tube _S12 , the negative pole of the second energy storage inductor _L12 and the negative pole of the first output filter capacitor C _f1 are connected and grounded; the negative pole of the input filter inductor L _i is respectively connected to the input filter The positive pole of the capacitor C _i is connected to the positive pole of the first energy storage inductor L ₁₁ ; the input filter inductor L _i and the input filter capacitor C _i form an input filter, and the input filter filters the input high-voltage DC power supply U _i ; The negative pole of the first energy storage inductance L ₁₁ is connected to the drain of the first power switch tube S ₁₁ and the positive pole of the first energy storage capacitor C ₁ ; the source of the first power switch tube S ₁₁ is connected to the first voltage equalizing clamp The positive pole of the bit capacitor C _c1 is connected to the drain of the second power switch tube _S12 ; the negative pole of the first energy storage capacitor _C1 is connected to the source pole of the third power switch tube _S13 and the positive pole of the second energy storage inductor _L12 connected; the negative pole of the first equalizing clamp capacitor C _c1 is connected to the drain of the third power switch tube _S13 and the source of the fourth power switch tube _S14 ; the drain of the fourth power switch tube _S14 is connected to The positive phase of the first output filter capacitor C _f1 is connected to one end of the load Z _L , which constitutes a bidirectional three-level Sepic DC converter; the negative pole of the input filter inductor L _i and the positive phase of the third energy storage inductor L ₂₁ connection; the negative pole of the third energy storage inductance L ₂₁ is connected to the drain of the fifth power switch tube S ₂₁ and the positive pole of the second energy storage capacitor C ₂ , and the source of the fifth power switch tube S ₂₁ is connected to the sixth power switch The drain of the tube S ₂₂ is connected to the positive pole of the second flying capacitor C _c2 ; the negative pole of the second energy storage capacitor C ₂ is connected to the source pole of the seventh power switch tube S ₂₃ and the positive pole of the fourth energy storage inductor L ₂₂ connected; the negative pole of the second equalizing clamp capacitor _Cc2 is connected to the drain of the seventh power switch _S23 and the source of the eighth power switch _S24 ; the negative pole of the fourth energy storage inductor _L22 is connected to the first The source of the six power switch tubes _S22 , the negative pole of the input DC power supply _Ui and the negative pole of the second output filter capacitor C _f2 are connected and grounded; the drain of the eighth power switch tube _S24 is connected to the second output filter capacitor C _f2 The positive phase of the positive pole is connected to the other end of the load Z _L to form another bidirectional three-level Sepic converter; the output filter capacitors C _f1 and C _f2 filter out the higher harmonics in the output voltage of the three-level DC converter, A low-frequency sinusoidal AC voltage u _o1 with the same DC bias and a phase difference of 180° is obtained on both sides of the AC load , u _o2 , so as to obtain high-quality output voltage u _o .

In the non-isolated DC converter type differential three-level inverter of the present invention, a high-voltage DC power supply U _i , an input filter, two completely identical non-isolated bidirectional three-level Zeta converters and an AC load are sequentially connected Z _L is combined into a Zeta circuit topology suitable for step-up DC-AC conversion occasions, that is, the positive pole of the input high-voltage DC power supply U _i is connected to the positive pole of the input filter inductor L _i , and the negative pole of the input high-voltage DC power supply U _i is connected to the input filter capacitor C _i The negative pole of the first energy storage inductor _L1 , the source of the fourth power switch _S14 and the negative pole of the first output filter capacitor C _f1 are connected and grounded; the negative pole of the input filter inductor L _i is connected to the input filter capacitor The anode of C _i is connected to the drain of the second power switch tube _S12 ; the input filter inductance L _i and input filter capacitor C _i form an input filter, and the input filter filters the input high-voltage DC power supply U _i ; The source of the second power switch tube S ₁₂ is connected to the drain of the first power switch tube S ₁₁ and the anode of the first equalizing clamp capacitor C _c1 ; the source of the first power switch tube S ₁₁ is connected to the first The positive pole of the energy storage capacitor _C1 is connected; the negative pole of the first energy storage capacitor _C1 is connected to the positive pole of the first energy storage inductor _L1 , the drain of the third power switch tube _S13 , and the positive pole of the first output filter inductor _Lf1 connected; the negative pole of the first equalizing clamp capacitor C _c1 is connected with the source pole of the third power switch tube S ₁₃ and the drain pole of the fourth power switch tube S ₁₄ ; the negative pole of the first output filter inductor Lf1 is connected with the The positive pole of an output filter capacitor C _f1 is connected to one end of the load Z _L ; the first output filter inductor L _f1 and the first output filter capacitor C _f1 constitute an output filter circuit, which filters out the three-level output voltage High-order harmonics, high-quality sinusoidal voltage u _o1 with DC bias is obtained; the above constitutes a bidirectional three-level Zeta DC converter; the negative pole of the input filter inductor L _i and the sixth power switch tube S ₂₂ The drains are connected; the source of the sixth power switch _S22 is connected to the drain of the fifth power switch _S21 and the anode of the second equalizing clamp capacitor _Cc2 ; the source of the fifth power switch _S21 The pole is connected to the positive pole of the second energy storage capacitor _C2 ; the negative pole of the second energy storage capacitor _C2 is connected to the positive pole of the second energy storage inductor _L2 , the drain of the seventh power switch tube _S23 and the second output filter The positive pole of the inductor L _f2 is connected; the negative pole of the second equalizing clamping capacitor C _c2 is connected to the source of the seventh power switch _S23 and the drain of the eighth power switch _S24 ; the eighth power switch S The source of ₂₄ is connected to the negative pole of the second energy storage inductor L ₂ , the second output filter capacitor C _f2 and the input DC power supply U _i and grounded; the negative pole of the second output filter inductor L _f2 is connected to the positive pole of the second energy storage capacitor C _f2 connected to the other end of the load Z _L ; the second output filter inductance L _f2 and the second output filter capacitor C _f2 constitute An output filter circuit is formed, which filters out high-order harmonics in the three-level output voltage, and obtains a high-quality sinusoidal voltage u _o2 with a DC bias; the above constitutes another bidirectional three-level Zeta converter.

The present invention will be described in further detail below in conjunction with the accompanying drawings.

In conjunction with Fig. 1, the circuit structure of the differential DC converter type non-isolated three-level inverter of the present invention consists of an input high-voltage DC power supply, an input filter, two identical non-isolated bidirectional three-level DC converters and The output AC load constitutes. This circuit structure can directly transform unstable high-voltage and low-quality direct current into stable and high-quality sinusoidal alternating current. The positive pole of the input high-voltage DC power supply Ui is connected to one end of the input filter inductor Li, and the other end of the input filter inductor Li is respectively connected to two bidirectional three-level DC converters and the input filter capacitor Ci, and the other end of the input filter capacitor Ci One end is respectively connected to the negative pole of the input high-voltage DC power supply Ui and two bidirectional three-level DC converters, the input filter inductor Li and the input filter capacitor Ci constitute an input filter, and the input filter controls the input high-voltage DC power supply Ui Filtering; the two identical non-isolated bidirectional three-level DC converters output sinusoidal AC voltages with the same DC bias, the same frequency, and a phase difference of 180°. The difference between the two is the required output sinusoidal voltage uo. Compared with traditional step-up and step-down DC-AC inverters, this circuit structure only has single-stage power conversion stages, so this type of converter can improve input side power factor, conversion efficiency, power density and reliability. Due to the differential structure, this type of inverter can adapt to a wider voltage input range; due to the introduction of three-level technology, the voltage stress on each switching tube is half of that of the two-level DC-AC inverter , effectively reducing the volume and weight of the output filter, improving the output voltage waveform and spectrum characteristics, and improving the quality of the output waveform.

The basic working principle of the non-isolated DC converter type differential three-level inverter is as follows: According to the requirements of different output voltages, the voltage and current double closed-loop control is adopted, and Ui, Ui can be obtained by adjusting the duty cycle of the bidirectional DC converter. Voltages of different levels such as /2, 0, etc. are filtered by the output filter respectively, so that the left and right bidirectional three-level DC converters can output sinusoidal voltages with the same DC bias and a phase difference of 180°. The load terminal differentially outputs positive and negative alternating stable, high-quality sinusoidal AC voltage.

The non-isolated DC converter differential three-level inverter with the above circuit structure proposed by the present invention can obtain different circuit topology families by changing the type of bidirectional three-level DC converter, including Boost type and Buck type , Buck-Boost type, Cuk type, Sepic type and Zeta type six circuit topologies, all topologies in this circuit topology family have the same differential structure, but there are still some slight differences, such as Buck type, Cuk type and Zeta type Type circuit topology has an output filter inductor Lf, while Boost type, Buck-Boost type and Sepic type circuit topologies do not have an output filter inductor Lf; Buck type does not have a boost inductor L, while the rest have boost inductors.

Among them, the Boost circuit topology is shown in Figure 2, and its specific circuit connections are as follows: the positive pole of the input DC power supply Ui is connected to the positive pole of the input filter inductor Li, the negative pole of the input DC power supply Ui is connected to the negative pole of the input filter capacitor Ci, and the second power The source of the switch tube S12 is connected to the negative pole of the first output filter capacitor Cf1 and grounded; the negative pole of the input filter inductor Li is respectively connected to the positive pole of the first energy storage inductor L1 and the positive pole of the input filter capacitor Ci; the first energy storage The negative pole of the inductor L1 is connected to the drain of the first power switch S11 and the source of the third power switch S13; the drain of the third power switch S13 is respectively connected to the source of the fourth power switch S14 and the first The negative electrodes of the equalizing clamp capacitor Cc1 are connected; the source of the first power switch S11 is connected to the drain of the second power switch S12 and the positive electrode of the first equalizing clamp capacitor Cc1 is connected; the fourth power switch S14 The drain of the first output filter capacitor Cf1 is connected to the positive pole of the load ZL, and the above constitutes a bidirectional three-level Boost converter; the negative pole of the input filter inductor Li is connected to the positive pole of the second energy storage inductor L2 ; The negative pole of the second energy storage inductor L2 is connected to the drain of the fifth power switch S21 and the source of the seventh power switch S23; the source of the fifth power switch S21 is connected to the sixth power switch S22 respectively The drain is connected to the positive pole of the second voltage equalizing clamp capacitor Cc2; the drain of the seventh power switch tube S23 is connected to the source of the eighth power switch tube S24 and the negative pole of the second voltage equalizing clamp capacitor Cc2; The sources of the six power switch tubes S22 are respectively connected to the negative pole of the output filter capacitor Cf2 and the negative pole of the input DC power supply Ui and grounded; the drain of the eighth power switch tube S24 is connected to the positive pole of the second output filter capacitor Cf2 and connected to the ground. The other end of the load ZL constitutes another bidirectional three-level Boost DC converter. The Boost topology is suitable for step-down DC-AC conversion applications.

The Buck type circuit topology is shown in Figure 3, and its specific circuit connections are as follows: the positive pole of the input high-voltage DC power supply Ui is connected to the positive pole of the input filter inductor Li, the negative pole of the input high-voltage DC power supply Ui is connected to the negative pole of the input filter capacitor Ci, and the fourth power switch The source of the tube S14 is connected to the negative pole of the first output filter capacitor Cf1 and grounded; the negative pole of the input filter inductor Li is respectively connected to the positive pole of the input filter capacitor Ci and the drain of the second power switch tube S12; the second power switch tube The source of S12 is connected to the drain of the first power switch S11 and the positive pole of the first equalizing clamp capacitor Cc1; the source of the first power switch S11 is connected to the positive pole of the first output filter inductor Lf1, and the third power switch The drain of the tube S13 is connected; the negative pole of the first flying capacitor Cc1 is connected with the source of the third power switch tube S13 and the drain of the fourth power switch tube S14; the negative pole of the first output filter inductor Lf1 is connected with the first The positive pole of the output filter capacitor Cf1 is connected to one end of the load ZL; the above constitutes a bidirectional three-level Buck DC converter. The negative pole of the input filter inductor Li is connected to the drain of the sixth power switch S22; the source of the sixth power switch S22 is connected to the drain of the fifth power switch S21 and the positive pole of the second equalizing clamp Cc2 The source of the fifth power switch tube S21 is connected to the drain of the seventh power switch tube S23 and the positive pole of the second output filter inductor Lf2; the negative pole of the second equalizing clamp capacitor Cc2 is connected to the seventh power switch tube S23 The source and the drain of the eighth power switch tube S24 are connected; the source of the eighth power switch tube S24 is connected to the negative pole of the second output filter capacitor Cf2 and the negative pole of the DC power supply Ui and grounded; the second output filter inductor Lf2 The negative pole of the second output filter capacitor Cf2 is connected to the other end of the load ZL; the above constitutes another bidirectional three-level Buck converter. The Buck topology is suitable for step-down DC-AC conversion applications.

The Buck-boost circuit topology is shown in Figure 4, and its specific circuit connections are as follows: the positive pole of the input high-voltage DC power supply Ui is connected to the positive pole of the input filter inductor Li, the negative pole of the input high-voltage DC power supply Ui is connected to the negative pole of the input filter capacitor Ci, the first The negative pole of an energy storage inductor L1 and the negative pole of the first output filter capacitor Cf1 are connected and grounded; the negative pole of the input filter inductor Li is respectively connected to the positive pole of the input filter capacitor Ci and the drain of the second power switch tube S12; the second power The source of the switch tube S12 is connected to the drain of the first power switch tube S12 and the positive pole of the first equalizing clamp capacitor Cc1; the source of the first power switch tube S11 is connected to the drain of the third power switch tube S13 respectively , the positive pole of the first energy storage inductor L1 is connected; the source of the third power switch tube S13 is connected to the negative pole of the first equalizing clamp capacitor Cc1 and the drain of the fourth power switch tube S14; the fourth power switch tube The source of S14 and the first output filter capacitor Cf1 are connected to one end of the load ZL, which constitutes a bidirectional three-level Buck-boost DC converter; the negative electrode of the input filter inductor Li and the drain of the sixth power switch S22 The poles are connected; the source of the sixth power switch S22 is connected to the drain of the fifth power switch S21 and the positive pole of the second equalizing clamp capacitor Cc2; the source of the fifth power switch S21 is connected to the seventh power switch S21 The drain of the switch tube S23 is connected to the positive pole of the second energy storage inductor L2; the negative pole of the second energy storage inductor L2 is respectively connected to the negative pole of the second output filter capacitor Cf2 and the negative pole of the DC input power supply Ui and grounded; the second The negative pole of the flying capacitor Cc2 is connected to the source of the seventh power switch S23 and the drain of the eighth power switch S24; the source of the eighth power switch S24 is connected to the positive pole of the second output filter capacitor Cf2 The other end of the input load ZL constitutes another bidirectional three-level Buck-boost converter. Buck-boost topology is suitable for step-up and step-down DC-AC conversion occasions.

The Cuk-type circuit topology is shown in Figure 5, and its specific circuit connections are as follows: the positive pole of the input high-voltage DC power supply Ui is connected to the positive pole of the input filter inductor Li, the negative pole of the input high-voltage DC power supply Ui is connected to the negative pole of the input filter capacitor Ci, and the second power switch The source of the tube S12, the drain of the fourth power switch tube S14 and the negative pole of the first output filter capacitor Cf1 are connected and grounded; the negative pole of the input filter inductor Li is respectively connected to the positive pole of the input filter capacitor Ci and the first energy storage inductor L1 The positive pole is connected; the negative pole of the first energy storage inductor L1 is connected to the drain of the first power switch tube S11 and the positive pole of the first energy storage capacitor C1; the source pole of the first power switch tube S11 is connected to the first voltage equalizing clamp The positive pole of the capacitor Cc1 is connected to the drain of the second power switch tube S12; the negative pole of the first energy storage capacitor C1 is connected to the source pole of the third power switch tube S13 and the positive pole of the first output filter inductor Lf1; The negative pole of the clamping capacitor Cc1 is connected to the drain of the third power switch S13 and the source of the fourth power switch S14; the negative pole of the first output filter inductor Lf1 is connected to the load with the first output filter capacitor Cf1 One end of ZL; the above constitutes a bidirectional three-level Cuk DC converter; the negative pole of the input filter inductor Li is connected to the positive pole of the second energy storage inductor L2; the negative pole of the second energy storage inductor L2 is connected to the fifth power switch tube S21 The drain of the second energy storage capacitor C2 is connected to the drain, the source of the fifth power switch S21 is connected to the drain of the sixth power switch S22 and the positive of the second equalizing clamping capacitor Cc2; the second The negative pole of the energy storage capacitor C2 is connected to the source of the seventh power switch tube S23 and the positive pole of the second output filter inductor Lf2; the negative pole of the second equalizing clamp capacitor Cc2 is connected to the drain of the seventh power switch tube S23 and the The source poles of the eight power switch tubes S24 are connected; the source poles of the sixth power switch tube S22 are respectively connected to the drain pole of the eighth power switch tube S24, the negative pole of the second output filter capacitor Cf2, and the negative pole of the input DC power supply Ui, and grounded; the negative pole of the second output filter inductor Lf2 and the positive pole of the second output filter capacitor Cf2 are connected to the other end of the load ZL; the above forms another bidirectional three-level Cuk converter. Cuk topology is suitable for step-up and step-down DC-AC conversion occasions.

The Sepic circuit topology is shown in Figure 6, and its specific circuit connections are as follows: the positive pole of the input high-voltage DC power supply Ui is connected to the positive pole of the input filter inductor Li, the negative pole of the input high-voltage DC power supply Ui is connected to the negative pole of the input filter capacitor Ci, and the second power switch The source of the tube S12, the negative pole of the second energy storage inductor L12 and the negative pole of the first output filter capacitor Cf1 are connected and grounded; the negative pole of the input filter inductor Li is respectively connected to the positive pole of the input filter capacitor Ci and the first energy storage inductor L11 The positive pole is connected; the negative pole of the first energy storage inductor L11 is connected to the drain of the first power switch tube S11 and the positive pole of the first energy storage capacitor C1; the source of the first power switch tube S11 is connected to the first voltage equalizing clamp The positive pole of the capacitor Cc1 is connected to the drain of the second power switch tube S12; the negative pole of the first energy storage capacitor C1 is connected to the source of the third power switch tube S13 and the positive pole of the second energy storage inductor L12; The negative pole of the clamping capacitor Cc1 is connected to the drain of the third power switch S13 and the source of the fourth power switch S14; the drain of the fourth power switch S14 is connected to the positive pole of the first output filter capacitor Cf1 Connected to one end of the load ZL, the above constitutes a bidirectional three-level Sepic DC converter; the negative pole of the input filter inductor Li is connected to the positive pole of the third energy storage inductor L21; the negative pole of the third energy storage inductor L21 is connected to the fifth power The drain of the switching tube S21 is connected to the positive pole of the second energy storage capacitor C2, the source of the fifth power switching tube S21 is connected to the drain of the sixth power switching tube S22 and the positive pole of the second flying capacitor Cc2; The negative pole of the second energy storage capacitor C2 is connected to the source of the seventh power switch tube S23 and the positive pole of the fourth energy storage inductor L22; the negative pole of the second voltage equalizing clamp capacitor Cc2 is connected to the drain of the seventh power switch tube S23 And the source of the eighth power switch tube S24 is connected; the negative pole of the fourth energy storage inductor L22 is connected with the source pole of the sixth power switch tube S22, the negative pole of the input DC power supply Ui and the negative pole of the second output filter capacitor Cf2 and grounding; the drain of the eighth power switch S24 and the positive pole of the second output filter capacitor Cf2 are connected to the other end of the load ZL, forming another bidirectional three-level Sepic converter. The Sepic topology is suitable for step-up and step-down DC-AC conversion applications.

The Zeta-type circuit topology is shown in Figure 7, and its specific circuit connections are as follows: the positive pole of the input high-voltage DC power supply Ui is connected to the positive pole of the input filter inductor Li, the negative pole of the input high-voltage DC power supply Ui is connected to the negative pole of the input filter capacitor Ci, and the first energy storage The negative pole of the inductor L1, the source pole of the fourth power switch tube S14, and the negative pole of the first output filter capacitor Cf1 are connected and grounded; the negative pole of the input filter inductor Li is connected to the positive pole of the input filter capacitor Ci and the second power switch tube S12 respectively. The drains are connected; the source of the second power switch tube S12 is connected to the drain of the first power switch tube S11 and the anode of the first equalizing clamp capacitor Cc1; the source of the first power switch tube S11 is connected to the first The positive pole of the energy storage capacitor C1 is connected; the negative pole of the first energy storage capacitor C1 is connected with the positive pole of the first energy storage inductor L1, the drain of the third power switch tube S13, and the positive pole of the first output filter inductor Lf1; the first The negative pole of the equalizing clamp capacitor Cc1 is connected to the source pole of the third power switch tube S13 and the drain pole of the fourth power switch tube S14; the negative pole of the first output filter inductor Lf1 is connected to the positive pole of the first output filter capacitor Cf1 The phase is connected to one end of the load ZL; the above constitutes a bidirectional three-level Zeta DC converter; the negative pole of the input filter inductor Li is connected to the drain of the sixth power switch tube S22; the source of the sixth power switch tube S22 It is connected to the drain of the fifth power switch tube S21 and the positive pole of the second voltage equalizing clamp capacitor Cc2; the source of the fifth power switch tube S21 is connected to the positive pole of the second energy storage capacitor C2; the second energy storage capacitor The negative pole of C2 is connected to the positive pole of the second energy storage inductor L2, the drain pole of the seventh power switch tube S23, and the positive pole of the second output filter inductor Lf2; the negative pole of the second equalizing clamp capacitor Cc2 is connected to the seventh power switch The source of the tube S23, the eighth

The drain of the power switch tube S24 is connected; the source of the eighth power switch tube S24 is connected to the second energy storage inductor L2, the second output filter capacitor Cf2 and the negative pole of the input DC power supply Ui and grounded; the second output filter inductor Lf2 The negative pole is connected to the positive pole of the second energy storage capacitor Cf2 and connected to the other end of the load ZL; the above forms another bidirectional three-level Zeta converter. The Zeta topology is suitable for step-up and step-down DC-AC conversion occasions.

Claims (7)

1. A non-isolated DC converter type differential three-level inverter, characterized in that: a high-voltage DC power supply [U _i ], an input filter inductor [L _i ], an input filter capacitor [C _i ], two identical bidirectional three-level DC converters and AC loads; among them, the input terminals of two non-isolated bidirectional three-level DC converters are connected in parallel, and the output terminals are connected in series; the input high-voltage DC power supply [U _i ] The positive pole is connected to one end of the input filter inductor [L _i ], and the other end of the input filter inductor [L _i ] is respectively connected to two bidirectional three-level DC converters and an input filter capacitor [C _i ]. The input filter capacitor [ The other end of C _i ] is respectively connected to the negative pole of the input high-voltage DC power supply [U _i ] and two bidirectional three-level DC converters, and the input filter inductor [L _i ] and input filter capacitor [C _i ] constitute the input filter, the input filter filters the input high-voltage DC power supply [U _i ]; the two bidirectional three-level DC converters convert the input voltage filtered by the input filter into a three-level output voltage, the first A bidirectional three-level DC converter [1] consists of a first energy storage inductor [L ₁ ], a first power switch tube [S ₁₁ ], a second power switch tube [S ₁₂ ], a third power switch tube [S ₁₃ ], the fourth power switch tube [S ₁₄ ], the first equalizing clamp capacitor [C _c1 ] and the first output filter capacitor [C _f1 ]; the second bidirectional three-level DC converter [2] consists of an energy storage inductor [L ₂ ], the fifth power switch tube [S ₂₁ ], the sixth power switch tube [S ₂₂ ], the seventh power switch tube [S ₂₃ ], the eighth power switch tube [S ₂₄ ], the second equalizing clamp Bit capacitor [C _c2 ] and the second output filter capacitor [C _f2 ]; in the bidirectional three-level DC converter [1], one end of the first energy storage inductor [L ₁ ] is connected to the input filter, and the other end respectively connected to the first power switch tube [S ₁₁ ] and the third switch tube [S ₁₃ ]; the other end of the first power switch tube [S ₁₁ ] is respectively connected to the second power switch tube [S ₁₂ ] and the first The other end of the second power switch tube [S ₁₂ ] is connected to _{the fourth power switch tube [S 14 ], and the other end of the fourth power switch tube [S 14 ] is} connected to the The first output filter capacitor [C _f1 ], one end of the first output filter capacitor [C _f1 ] is connected to one end of the output AC load [Z _L ]; in the bidirectional three-level DC converter [2], the second energy storage One end of the inductor [L ₂ ] is connected to the input filter, and the other end is respectively connected to the fifth power switch tube [S ₂₁ ] and the seventh power switch tube [S ₂₃ ]; the other end of the fifth power switch tube [S ₂₁ ] One end is respectively connected to the sixth power switch tube [S ₂₂ ] and the second equalizing clamp capacitor [C _c2 ]; the sixth power switch tube [S _{2 2} ] is connected to the input filter; the second equalizing clamp capacitor [C _c2 ] is respectively connected to the other end of the seventh power switch tube [S ₂₃ ] and the eighth power switch tube [S ₂₄ ]. The other ends of the eight power switch tubes [S ₂₄ ] are respectively connected to the second output filter capacitor [C _f2 ]; one end of the second output filter capacitor [C _f2 ] is connected to the other end of the output AC load [Z _L ]; the two The two DC converters output sinusoidal AC voltages with the same DC bias, the same frequency, and a phase difference of 180°. The difference between the two is the output voltage u ₀ . 2. A kind of non-isolated DC converter type differential three-level inverter according to claim 1, characterized in that: the high-voltage DC power supply [U _i ], input filter, two identical The non-isolated bidirectional three-level Boost converter and AC load [Z _L ] are combined to form a Boost circuit topology suitable for step-up DC-AC conversion occasions, that is, the positive pole of the input DC power supply [U _i ] and the input filter inductor [L _i ] is connected to the positive pole, the negative pole of the input DC power supply [U _i ] is in phase with the negative pole of the input filter capacitor [C _i ], the source of the second power switch tube [S ₁₂ ] and the negative pole of the first output filter capacitor [C _f1 ] connected and grounded; the negative pole of the input filter inductor [L _i ] is respectively connected to the positive pole of the first energy storage inductor [L ₁ ] and the positive pole of the input filter capacitor [C _i ]; the input filter inductor [L _i ] and The input filter capacitor [C _i ] constitutes the input filter; the negative pole of the first energy storage inductor [L ₁ ] is in phase with the drain of the first power switch tube [S ₁₁ ] and the source of the third power switch tube [S ₁₃ ] connection; the drain of the third power switch tube [S ₁₃ ] is respectively connected to the source of the fourth power switch tube [S ₁₄ ] and the negative pole of the first equalizing clamp capacitor [C _c1 ]; the first power switch tube The source of [S ₁₁ ] is connected to the drain of the second power switch [S ₁₂ ] and the anode of the first equalizing clamp capacitor [C _c1 ]; the drain of the fourth power switch [S ₁₄ ] is connected to The positive pole of the first output filter capacitor [C _f1 ] is connected to one end of the load [Z _L ], which constitutes a bidirectional three-level Boost converter; the negative pole of the input filter inductor [L _i ] is connected to the second energy storage inductor The positive pole of [L ₂ ] is connected; the negative pole of the second energy storage inductor [L ₂ ] is connected to the drain of the fifth power switch [S ₂₁ ] and the source of the seventh power switch [S ₂₃ ]; The sources of the five power switch tubes [S ₂₁ ] are respectively connected to the drains of the sixth power switching tube [S ₂₂ ] and the anode of the second equalizing clamp capacitor [C _c2 ]; the seventh power switch tube [S ₂₃ ] is connected to the source of the eighth power switch tube [S ₂₄ ] and the negative pole of the second equalizing clamp capacitor [C _c2 ]; the source of the sixth power switch tube [S ₂₂ ] is respectively connected to the output filter The negative pole of the capacitor [C _f2 ] is connected to the negative pole of the input DC power supply [U _i ] and grounded; the drain of the eighth power switch tube [S ₂₄ ] is connected to the positive pole of the second output filter capacitor [C _f2 ]. The other end of the load [Z _L ] constitutes another bidirectional three-level Boost DC converter; the output filter capacitors C _f1 and C _f2 filter out the higher harmonics in the output voltage of the three-level DC converter. Both sides of the load get a low-frequency sinusoidal AC voltage with the same DC bias and a phase difference of 180° u _o1 , u _o2 , so as to obtain the output voltage u _o . 3. The non-isolated DC converter type differential three-level inverter according to claim 1, characterized in that: a high-voltage DC power supply [U _i ], an input filter, two identical non- The isolated bidirectional three-level Buck-boost converter and the AC load [Z _L ] are combined to form a Buck-boost circuit topology suitable for buck-boost DC-AC conversion occasions, that is, the positive pole of the input high-voltage DC power supply [U _i ] and the input The filter inductor [L _i ] is connected to the positive pole, and the negative pole of the [U _i ] input high-voltage DC power supply is connected to the negative pole of the input filter capacitor [C _i ], the negative pole of the first energy storage inductor [L ₁ ] and the first output filter capacitor [C The negative pole of _f1 ] is connected and grounded; the negative pole of the input filter inductor [L _i ] is respectively connected with the positive pole of the input filter capacitor [C _i ] and the drain of the second power switch tube [S ₁₂ ]; the input filter inductor [L _i ] and input filter capacitor [C _i ] form an input filter; the source of the second power switch [S ₁₂ ], the drain of the first power switch [S ₁₂ ] and the first equalizing clamp capacitor The anode of [C _c1 ] is connected; the source of the first power switch [S ₁₁ ] is respectively connected to the drain of the third power switch [S ₁₃ ] and the anode of the first energy storage inductor [L ₁ ]; The source of the third power switch [S ₁₃ ] is connected to the negative pole of the first equalizing clamp capacitor [C _c1 ] and the drain of the fourth power switch [S ₁₄ ]; the fourth power switch [S ₁₄ ] and the first output filter capacitor [C _f1 ] are connected to one end of the load [Z _L ], which constitutes a bidirectional three-level Buck-boost DC converter; the negative pole of the input filter inductor [L _i ] Connected to the drain of the sixth power switch tube [S ₂₂ ]; the source of the sixth power switch tube [S ₂₂ ], the drain of the fifth power switch tube [S ₂₁ ] and the second equalizing clamp capacitor C The anode of _c2 is connected; the source of the fifth power switch [S ₂₁ ] is connected to the drain of the seventh power switch [S ₂₃ ] and the anode of the second energy storage inductor [L ₂ ]; the second energy storage The negative pole of the inductor [L ₂ ] is respectively connected to the negative pole of the second output filter capacitor [C _f2 ] and the negative pole of the DC input power supply [U _i ] and grounded; the negative pole of the second flying capacitor [C _c2 ] is connected to the seventh power The source of the switch tube [S ₂₃ ] is connected to the drain of the eighth power switch tube [S ₂₄ ]; the source of the eighth power switch tube [S ₂₄ ] is connected to the positive pole of the second output filter capacitor [C _f2 ] Connect to the other end of the load [Z _L ], the above constitutes another bidirectional three-level Buck-boost converter; the output filter capacitors C _f1 and C _f2 filter out the high-order harmonics in the output voltage of the three-level DC converter wave, with the same DC bias on both sides of the AC load, with a phase difference of 1 80° low-frequency sinusoidal AC voltage u _o1 , u _o2 to obtain the output voltage u _o . 4. The non-isolated DC converter type differential three-level inverter according to claim 1, characterized in that: a high-voltage DC power supply [U _i ], an input filter, two identical non- The isolated bidirectional three-level Cuk converter and the AC load group [Z _L ] synthesize the Cuk circuit topology suitable for buck-boost DC-AC conversion occasions, that is, the positive pole of the input high-voltage DC power supply [U _i ] and the input filter inductance [L _i ] connected to the positive pole, the negative pole of the input high-voltage DC power supply [U _i ] and the negative pole of the input filter capacitor [C _i ], the source of the second power switch tube [S ₁₂ ], and the drain of the fourth power switch tube [S ₁₄ ] pole and the negative pole of the first output filter capacitor [C _f1 ] are connected and grounded; the negative pole of the input filter inductor [L _i ] is connected to the positive pole of the input filter capacitor [C _i ] and the positive pole of the first energy storage inductor [L ₁ ] respectively connected; the input filter inductor [L _i ] and the input filter capacitor C _i form an input filter; the negative pole of the first energy storage inductor [L ₁ ] is connected to the drain of the first power switch tube [S ₁₁ ] and the first The positive pole of the energy storage capacitor [C ₁ ] is connected; the source of the first power switch tube [S ₁₁ ] is connected with the positive pole of the first equalizing clamp capacitor C _c1 and the drain of the second power switch tube [S ₁₂ ] connection; the negative pole of the first energy storage capacitor [C ₁ ] is connected to the source pole of the third power switch tube [S ₁₃ ] and the positive pole of the first output filter inductor [L _f1 ]; the first equalizing clamp capacitor [C The negative pole of _c1 ] is connected to the drain of the third power switch tube [S ₁₃ ] and the source pole of the fourth power switch tube [S ₁₄ ]; the negative pole of the first output filter inductor [L _f1 ] is connected to the first output filter capacitor [C _f1 ] is connected to one end of the load Z _L ; the above-mentioned first output filter inductor [L _f1 ] and first output filter capacitor [C _f1 ] constitute an output filter circuit, which filters out the high voltage in the three-level output voltage subharmonic, and a high-quality sinusoidal voltage u _o1 with a DC bias is obtained; the above constitutes a bidirectional three-level Cuk DC converter; the negative pole of the input filter inductor [L _i ] and the second energy storage inductor [L ₂ ] is connected to the positive pole; the negative pole of the second energy storage inductor [L ₂ ] is connected to the drain of the fifth power switch tube [S ₂₁ ] and the positive pole of the second energy storage capacitor [C ₂ ], and the fifth power switch The source of the tube [S ₂₁ ] is connected to the drain of the sixth power switch tube [S ₂₂ ] and the positive pole of the second equalizing clamp capacitor [C _c2 ]; the negative pole of the second energy storage capacitor [C ₂ ] is connected to the The source of the seventh power switch tube [S ₂₃ ] is connected to the positive pole of the second output filter inductor [L _f2 ]; the negative pole of the second equalizing clamp capacitor [C _c2 ] is connected to the seventh power switch tube [S ₂₃ ] The drain of the eighth power switch tube [S ₂₄ ] is connected to the source; the source of the sixth power switch tube [S 22 ] is connected to the eighth power switch tube [S ₂₂ ] respectively. The drain of the power switch tube [S ₂₄ ], the negative pole of the second output filter capacitor [C _f2 ], and the negative pole of the input DC power supply [U _i ] are connected and grounded; the negative pole of the second output filter inductor [L _f2 ] is connected to the first The positive phase of the second output filter capacitor [C _f2 ] is connected to the other end of the load [Z _L ]; the above-mentioned second output filter inductor [L _f2 ] and the second output filter capacitor [C _f2 ] constitute an output filter circuit, and the filter In addition to the higher harmonics in the three-level output voltage, a sinusoidal voltage u _o2 with a DC bias is obtained; the above constitutes another bidirectional three-level Cuk converter. 5. The non-isolated DC converter type differential three-level inverter according to claim 1, characterized in that: a high-voltage DC power supply [U _i ], an input filter, two identical non- The isolated bidirectional three-level Sepic converter and the AC load [Z _L ] are combined into a Sepic circuit topology suitable for buck-boost DC-AC conversion occasions, that is, the positive pole of the input high-voltage DC power supply [U _i ] and the input filter inductor [L _i ] connected to the positive pole, the negative pole of the input high-voltage DC power supply [U _i ] and the negative pole of the input filter capacitor [C _i ], the source pole of the second power switch tube [S ₁₂ ], and the negative pole of the second energy storage inductor [L ₁₂ ] And the negative pole of the first output filter capacitor [C _f1 ] is connected and grounded; the negative pole of the input filter inductor [L _i ] is connected to the positive pole of the input filter capacitor [C _i ] and the positive pole of the first energy storage inductor [L ₁₁ ] respectively connected; the input filter inductor [L _i ] and the input filter capacitor C _i form an input filter; the negative pole of the first energy storage inductor [L ₁₁ ] is connected to the drain of the first power switch tube [S ₁₁ ] and the first The positive pole of the energy storage capacitor C ₁ is connected; the source of the first power switch tube [S ₁₁ ] is connected to the positive pole of the first voltage equalizing clamp capacitor [C _c1 ] and the drain of the second power switch tube [S ₁₂ ] connection; the negative pole of the first energy storage capacitor [C ₁ ] is connected to the source pole of the third power switch tube [S ₁₃ ] and the positive pole of the second energy storage inductor [L ₁₂ ]; the first equalizing clamp capacitor [C The negative pole of _c1 ] is connected to the drain of the third power switch [S ₁₃ ] and the source of the fourth power switch [S ₁₄ ]; the drain of the fourth power switch [S ₁₄ ] is connected to the first output filter The positive pole of the capacitor [C _f1 ] is connected to one end of the load [Z _L ], which constitutes a bidirectional three-level Sepic DC converter; the negative pole of the input filter inductor [L _i ] and the third energy storage inductor [L ₂₁ ] is connected to the positive pole; the negative pole of the third energy storage inductor L ₂₁ is connected to the drain of the fifth power switch tube [S ₂₁ ] and the positive pole of the second energy storage capacitor [C ₂ ], and the fifth power switch tube [S 2 ₂₁ ] is connected to the drain of the sixth power switch tube [S ₂₂ ] and the positive pole of the second flying capacitor [C _c2 ]; the negative pole of the second energy storage capacitor [C ₂ ] is connected to the seventh power switch tube The source of [S ₂₃ ] and the positive pole of the fourth energy storage inductor L ₂₂ are connected; the negative pole of the second equalizing clamp capacitor [C _c2 ] is connected to the drain of the seventh power switch tube [S ₂₃ ] and the eighth The source of the power switch tube [S ₂₄ ] is connected; the negative pole of the fourth energy storage inductor [L ₂₂ ] is connected to the source pole of the sixth power switch tube [S ₂₂ ], the negative pole of the input DC power supply [U _i ] and the second The negative pole of the output filter capacitor [C _f2 ] is connected and grounded; the drain of the eighth power switch tube [S ₂₄ ] is connected to the second output filter The positive phase of the capacitor [C _f2 ] is connected to the other end of the load [Z _L ] to form another bidirectional three-level Sepic converter; the output filter capacitors C _f1 and C _f2 filter the output voltage of the three-level DC converter The high-order harmonics in the AC load get low-frequency sinusoidal AC voltages u _o1 and u _o2 with the same DC bias and a phase difference of 180° on both sides of the AC load, thereby obtaining the output voltage u _o . 6. The non-isolated DC converter type differential three-level inverter according to claim 1, characterized in that: a high-voltage DC power supply [U _i ], an input filter, two identical non- The isolated bidirectional three-level Zeta converter and the AC load [Z _L ] are combined to form a Zeta circuit topology suitable for step-up DC-AC conversion occasions, that is, the positive pole of the input high-voltage DC power supply [U _i ] and the input filter inductor [L _i ] positive pole connection, the negative pole of the input high-voltage DC power supply [U _i ] and the negative pole of the input filter capacitor [C _i ], the negative pole of the first energy storage inductor [L ₁ ], the source pole of the fourth power switch tube [S ₁₄ ] and The negative pole of the first output filter capacitor [C _f1 ] is connected to the ground; the negative pole of the input filter inductor [L _i ] is connected to the positive pole of the input filter capacitor [C _i ] and the drain of the second power switch tube [S ₁₂ ] respectively connected; the input filter inductance [L _i ] and input filter capacitor [C _i ] constitute an input filter; the source of the second power switch tube [S ₁₂ ] and the drain of the first power switch tube [S ₁₁ ] And the positive pole of the first equalizing clamp capacitor [C _c1 ] is connected; the source of the first power switch tube [S ₁₁ ] is connected to the positive pole of the first energy storage capacitor [C ₁ ]; the first energy storage capacitor [ The negative pole of C ₁ ] is connected to the positive pole of the first energy storage inductor [L ₁ ], the drain pole of the third power switch tube [S ₁₃ ], and the positive pole of the first output filter inductor [L _f1 ]; the first equalizing clamp The negative pole of the bit capacitor [C _c1 ] is connected to the source pole of the third power switch tube [S ₁₃ ] and the drain pole of the fourth power switch tube [S ₁₄ ]; the negative pole of the first output filter inductor [L _f1 ] is connected to the The positive phase of the first output filter capacitor [C _f1 ] is connected to one end of the load [Z _L ]; the first output filter inductor [L _f1 ] and the first output filter capacitor [C _f1 ] constitute an output filter circuit, The high-order harmonics in the three-level output voltage are filtered out, and a high-quality sinusoidal voltage u _o1 with a DC bias is obtained; the above constitutes a bidirectional three-level Zeta DC converter; the input filter inductor [L _i ] The negative pole of the sixth power switch tube [S ₂₂ ] is connected to the drain; the source of the sixth power switch tube [S ₂₂ ] is connected to the drain of the fifth power switch tube [S ₂₁ ], and the second voltage equalizing clamp The positive electrode of the capacitor [C _c2 ] is connected; the source of the fifth power switch tube [S ₂₁ ] is connected to the positive electrode of the second energy storage capacitor [C ₂ ]; the negative electrode of the second energy storage capacitor [C ₂ ] is connected to the first The positive pole of the second energy storage inductor [L ₂ ], the drain of the seventh power switch tube [S ₂₃ ] and the positive pole of the second output filter inductor [L _f2 ] are connected; the second equalizing clamp capacitor [C _c2 ] The cathode of the seventh power switch [S ₂₃ ] is connected to the source of the eighth power switch [S ₂₄ ]; the eighth power switch The source of the rate switching tube [S ₂₄ ] is connected to the second energy storage inductor [L ₂ ], the second output filter capacitor [C _f2 ] and the negative electrode of the input DC power supply [U _i ] and grounded; the second output filter inductor [ The negative pole of L _f2 ] is connected to the positive pole of the second energy storage capacitor [C _f2 ] and connected to the other end of the load [Z _L ]; the above-mentioned second output filter inductor [L _f2 ] and the second output filter capacitor [C _f2 ] constitute The output filter circuit is established to filter out the higher harmonics in the three-level output voltage, and the sinusoidal voltage u _o2 with DC bias is obtained; the above constitutes another bidirectional three-level Zeta converter. 7. A non-isolated DC converter type differential three-level inverter, characterized in that: a high-voltage DC power supply [U _i ] connected in sequence, an input filter, two identical non-isolated bidirectional three-level inverters A flat Buck converter and an AC load [Z _L ] are combined to form a Buck circuit topology suitable for step-down DC-AC conversion applications, that is, the positive pole of the input high-voltage DC power supply [U _i ] is connected to the positive pole of the input filter inductor [L _i ], and the input The negative pole of the high-voltage DC power supply [U _i ] is connected to the negative pole of the input filter capacitor [C _i ], the source pole of the fourth power switch tube [S ₁₄ ] and the negative pole of the first output filter capacitor [C _f1 ] and grounded; the input The negative pole of the filter inductor [L _i ] is respectively connected to the positive pole of the input filter capacitor [C _i ] and the drain of the second power switch tube [S ₁₂ ]; the input filter inductor [L _i ] and the input filter capacitor [C _i ] constitutes an input filter; the source of the second power switch tube [S ₁₂ ] is connected to the drain of the first power switch [S ₁₁ ] and the anode of the first equalizing clamp capacitor [C _c1 ]; the first The source of the power switch tube [S ₁₁ ] is connected to the positive pole of the first output filter inductor [L _f1 ] and the drain of the third power switch tube [S ₁₃ ]; the negative pole of the first flying capacitor [C _c1 ] and The source of the third power switch tube [S ₁₃ ] is connected to the drain of the fourth power switch tube [S ₁₄ ]; the negative pole of the first output filter inductor [L _f1 ] is connected to the first output filter capacitor [C _f1 ] The positive pole is connected to one end of the load [Z _L ]; the above-mentioned first output filter inductor [L _f1 ] and first output filter capacitor [C _f1 ] constitute an output filter circuit, which filters out high-order Harmonics, get a high-quality sinusoidal voltage u _o1 with DC bias; the above constitutes a bidirectional three-level Buck DC converter; input the negative pole of the filter inductor [L _i ] and the sixth power switch tube [S ₂₂ ] is connected to the drain; the source of the sixth power switch [S ₂₂ ] is connected to the drain of the fifth power switch [S ₂₁ ] and the anode of the second equalizing clamp [C _c2 ]; the fifth The source of the power switch tube [S ₂₁ ] is connected to the drain of the seventh power switch tube [S ₂₃ ] and the positive pole of the second output filter inductor [L _f2 ]; the second equalizing clamp capacitor [C _c2 ] The negative pole is connected to the source of the seventh power switch [S ₂₃ ] and the drain of the eighth power switch [S ₂₄ ]; the source of the eighth power switch [S ₂₄ ] is connected to the second output filter capacitor [C The negative pole of _f2 ] and the negative pole of the DC power supply [U _i ] are connected and grounded; the negative pole of the second output filter inductor [L _f2 ] is connected to the positive pole of the second output filter capacitor [C _f2 ] and connected to the load [Z _L ] the other end; the above-mentioned second output filter inductor [L _f2 ] and the second output filter The wave capacitor [C _f2 ] constitutes an output filter circuit, which filters out the high-order harmonics in the three-level output voltage, and obtains a sinusoidal voltage u _o2 with a DC bias; the above constitutes another bidirectional three-level Buck conversion device.

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