CN108847777B - Isolated modular cascade converter based on high-frequency chain technology - Google Patents

Isolated modular cascade converter based on high-frequency chain technology Download PDF

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CN108847777B
CN108847777B CN201810775586.7A CN201810775586A CN108847777B CN 108847777 B CN108847777 B CN 108847777B CN 201810775586 A CN201810775586 A CN 201810775586A CN 108847777 B CN108847777 B CN 108847777B
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active
voltage
diode
switch tube
bridge
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CN108847777A (en
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刘闯
蔡国伟
温联鑫
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Northeast Electric Power University
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Northeast Dianli University
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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
    • H02M7/53875—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 with analogue control of three-phase output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of DC power input into DC power output
    • H02M3/22—Conversion of DC power input into DC power output with intermediate conversion into AC
    • H02M3/24—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters
    • H02M3/28—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC
    • H02M3/325—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/007—Plural converter units in cascade

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

Abstract

The invention discloses an isolated modular cascade converter based on a high-frequency chain technology, which can realize the conversion from low-voltage direct current to high-voltage alternating current, wherein a single-phase topological structure and a three-phase topological structure of the converter are respectively formed by single-stage high-frequency isolated modules, the three-phase structures can be connected in a star shape or an angular shape, each module consists of an upper sub-module and a lower sub-module, and the sub-modules comprise a front-stage driving H bridge, a high-frequency transformer, a rear-stage driving H bridge and a voltage clamping circuit. The invention belongs to single-stage power conversion, so that the high-voltage side of each module does not need to be supported by a capacitor any more, compared with a two-stage modular cascade converter, the use of the capacitor can be reduced, the size and the cost of the device are reduced, and the problems of secondary side conversion, voltage spike and the like of the traditional single-stage converter are solved.

Description

Isolated modular cascade converter based on high-frequency chain technology
Technical Field
The invention relates to an isolated modular cascaded power conversion technology, in particular to an isolated modular cascaded converter based on a high-frequency chain technology.
Background
The application of the power electronic transformer in new energy grid connection is more and more extensive. In order to improve the voltage level of a high-voltage side, the conventional power electronic transformer widely adopts a modular cascade structure, such as a cascade H-bridge type, most of the modular cascade structures adopt a two-stage power conversion system according to the stage number of power conversion, as shown in figure 1, and the two-stage power conversion has the problems that a large number of voltage-stabilizing capacitors are needed by the high-voltage side of each module to buffer the secondary power fluctuation of a single-phase system, so that the device is large in size, low in power density and high in cost; meanwhile, voltage imbalance exists among the modules, complex voltage balance control is needed, and system reliability is reduced.
Disclosure of Invention
In order to solve the problems, the invention provides an isolated modular cascaded converter based on a high-frequency chain technology, which belongs to single-stage power conversion, so that the high-voltage side of each module does not need to be supported by a capacitor and controlled by voltage sharing, the problems of secondary side conversion, voltage spike and the like of the traditional single-stage converter are solved, and the power conversion between low-voltage direct current and high-voltage alternating current can be realized.
In order to achieve the purpose, the invention adopts the technical scheme that:
an isolated modular cascade converter based on high-frequency link technology, wherein the single-phase structure of the converter comprises a filter inductor LfA low voltage DC side capacitor CdcLN single-stage high-frequency isolation modules and n single-stage high-frequency isolation moldsThe blocks are connected in an input-parallel output-series (IPOS) structure, and the low-voltage DC ports (A, B) of the single-stage high-frequency isolation type modules are connected in parallel to form the low-voltage DC port (P) of the single-phase converterL、NL) The high-voltage alternating current ports (C, D) of the single-stage high-frequency isolation modules are connected in series, and the C port of the first single-stage high-frequency isolation module is connected in series with a filter inductor LfThen used as a high-voltage alternating current positive electrode port PHThe outgoing line of the D port of the module N is used as a high-voltage alternating-current negative port NH；
The three-phase structure of the converter comprises three single-phase structures and a low-voltage direct-current side capacitor C connected in parallel with a low-voltage direct-current busdcLThe low-voltage direct-current ports of the three single-phase structures are respectively connected in parallel on a low-voltage direct-current bus, and the three single-phase structures can be divided into star connection and angle connection according to different connection modes among the high-voltage alternating-current ports of the phase structures.
Preferably, when the star connection is adopted, three high-voltage alternating-current negative ports (N) in a single-phase structureH(a)、NH（b)、NH(c)) Making star connection; high voltage AC negative port (N) of phase A configuration when angular connection (101) is employedH(a)) High voltage AC positive port (P) connected to B phase unitH(b)) High voltage AC negative port of B-phase structure (N)H(b)) High voltage AC positive port (P) connected to C-phase structureH(c)) High voltage AC negative terminal port of C phase structure (N)H(c)) High voltage AC positive port (P) connected with A phase structureH(a))。
Preferably, the single-stage high-frequency isolation module consists of an upper submodule, a lower submodule and a low-voltage direct-current side capacitor CdcLThe upper sub-module and the lower sub-module are composed of a front-stage active H bridge, a high-frequency transformer, a rear-stage active H bridge and a voltage clamping circuit, the front-stage active H bridge is connected with the primary side of the high-frequency transformer, the rear-stage active H bridge and the clamping circuit are connected with the secondary side of the high-frequency transformer, and the positive and negative electrode ports (P) of the front-stage active H bridge of the upper sub-module1、N1) And positive and negative electrode ports (P) of preceding active H bridge of lower submodule2、N2) Are respectively connected in parallel as a low-voltage direct current port (A, B) and a post-stage active H-bridge port stringConnected to form a high-voltage AC port (C, D) and a low-voltage DC side capacitor CdcLThe low-voltage direct current port is connected in parallel; the front-stage active H bridge and the rear-stage active H bridge are both composed of active switching tubes with 4 anti-parallel diodes, the collector of each active switching tube is respectively connected with the cathode of each freewheeling diode, and the emitter is respectively connected with the anode of each freewheeling diode.
Preferably, the modulation ratio of the upper sub-module is an alternating current-direct current hybrid modulation ratio duD + D, the modulation ratio of the lower sub-module is the AC/DC mixed modulation ratio DlD-D, wherein D is a dc common modulation ratio, D is an ac modulation ratio, and the ac modulation ratios between different phases differ by 120 °;
the output voltage of the upper sub-module port (C, O) is a positive high-frequency voltage square wave with alternating current and direct current components, the output voltage of the lower sub-module port (O, D) is a negative high-frequency voltage square wave with alternating current and direct current components, and the output voltage of the port (C, D) of the single-stage high-frequency isolation module (1) is a high-frequency voltage square wave with positive and negative polarities and only alternating current components.
Preferably, the preceding active H-bridge of the upper submodule comprises a first active switching tube Q1A second active switch tube Q2A third active switch tube Q3And a fourth active switch tube Q4(ii) a First active switch tube Q1And a third active switch tube Q3Series, second active switching tube Q2And a fourth active switch tube Q4In series, with two arms in series, i.e. the first active switching tube Q1Collector and second active switching tube Q2Is connected as the positive electrode port P of the active H bridge1The third active switch tube Q3Emitter and fourth active switching tube Q4Is connected as a negative electrode port N of the active H bridge1(ii) a First active switch tube Q1Emitter and third active switching tube Q3Is connected with a first high-frequency transformer T1A second active switch tube Q connected to the primary side end E2Emitter and fourth active switching tube Q4After being connected with the collector of the secondA high frequency transformer T1The other terminal F of the primary side is connected;
the last-stage active H bridge of the upper submodule comprises a fifth active switching tube Q5A sixth active switch tube Q6A seventh active switch tube Q7And an eighth active switch tube Q8(ii) a Fifth active switch tube Q5And a seventh active switch tube Q7Series, sixth active switch tube Q6And an eighth active switch tube Q8In series, with two arms in series, i.e. fifth active switching tube Q5Collector and sixth active switching tube Q6Is connected as the positive terminal C of the active H bridge, and a seventh active switch tube Q7Emitter and eighth active switching tube Q8The emitter of the active H bridge is connected with a negative electrode port Q of the active H bridge; fifth active switch tube Q5Emitter and seventh active switching tube Q7Is connected with a first high-frequency transformer T1A sixth active switch tube Q connected with the secondary side end G6Emitter and eighth active switching tube Q8Is connected with a first high-frequency transformer T1The other terminal H of the secondary side is connected.
Preferably, the high-frequency transformer part of the upper submodule comprises a first high-frequency transformer T1The terminal (E, F) is a first high-frequency transformer T1Two terminals on the primary side, terminal (G, H), are the first high-frequency transformer T1Two terminals of the secondary side, wherein the terminals (E, G) are homonymous terminals; the high-frequency transformer part of the lower sub-module comprises a second high-frequency transformer T2The terminal (I, J) is a second high-frequency transformer T2Two terminals on the primary side, terminal (K, L), being a second high-frequency transformer T2Two terminals of the secondary side, wherein the terminals (I, K) are homonymous terminals;
preferably, the voltage clamping circuit of the upper sub-module comprises a first diode D1A second diode D2A third diode D3A fourth diode D4A first capacitor C1And a first resistor R1First diode D1And a third diode D3Are respectively connected with the first capacitor C after being connected in series1A first resistor R1Parallel, a second diode D2And a fourth diode D4Are respectively connected with the first capacitor C after being connected in series1A first resistor R1Parallel, first diode D1A second diode D2Cathode and first capacitor C1A first resistor R1Is connected to the anode of a third diode D3A fourth diode D4Anode and first capacitor C1A first resistor R1Is connected to the negative electrode of a first diode D1Anode of and a third diode D3Cathode of, first high-frequency transformer T1A secondary side terminal G connected to a second diode D2Anode of and a fourth diode D4Cathode of, first high-frequency transformer T1The other end H of the secondary side is connected.
Preferably, the preceding active H-bridge of the lower sub-module comprises a ninth active switching tube Q9A tenth active switch tube Q10An eleventh active switch tube Q11And a twelfth active switch tube Q12(ii) a Ninth active switch tube Q9And an eleventh active switch tube Q11Series, tenth active switch tube Q10And a twelfth active switch tube Q12In series, with two arms in series, i.e. ninth active switching tube Q9Collector and tenth active switching tube Q10Is connected as the positive electrode port P of the active H bridge2Eleventh active switch tube Q11Emitter and twelfth active switching tube Q12Is connected as a negative electrode port N of the active H bridge2(ii) a Ninth active switch tube Q9Emitter and eleventh active switching tube Q11Is connected with a second high-frequency transformer T2The original side end I is connected with a tenth active switch tube Q10Emitter and twelfth active switching tube Q12Is connected with a second high-frequency transformer T2The other terminal J of the primary side is connected.
The lower sub-module of the rear-stage active H bridge comprises a thirteenth active switching tube Q13A firstFourteen active switch tube Q14A fifteenth active switch tube Q15And a sixteenth active switch tube Q16: thirteenth active switch tube Q13And the fifteenth active switch tube Q15Series, fourteenth active switch tube Q14And a sixteenth active switch tube Q16In series, with two arms in series, i.e. thirteenth active switching tube Q13Emitter and fourteenth active switching tube Q14Is connected as the positive electrode port Q of the active H bridge, and a fifteenth active switching tube Q15Collector and sixteenth active switching tube Q16The collector of the active H bridge is connected with a negative electrode port D of the active H bridge; thirteenth active switch tube Q13Collector and fifteenth active switching tube Q15Is connected with a second high-frequency transformer T2A sub-edge connected to the sub-edge, a fourteenth active switch tube Q14Collector and sixteenth active switching tube Q16Is connected with a second high-frequency transformer T2The other terminal L of the secondary side is connected.
Preferably, the voltage clamping circuit of the lower sub-module comprises a fifth diode D5A sixth diode D6A seventh diode D7An eighth diode D8A second capacitor C3And a second resistor R2Fifth diode D5And a seventh diode D7Are respectively connected with a second capacitor C after being connected in series2A second resistor R2Parallel, sixth diode D6And an eighth diode D8Are respectively connected with a second capacitor C after being connected in series2A second resistor R2Parallel, fifth diode D5A sixth diode D6Cathode and second capacitor C2A second resistor R2Is connected to the anode of a seventh diode D7An eighth diode D8Anode and second capacitor C2A second resistor R2Is connected to the negative pole of a fifth diode D5Anode of and seventh diode D7Cathode of, a second high-frequency transformer T2A sixth diode D connected to the secondary side terminal K6Anode of and the eighth diode D8Cathode of, a second high-frequency transformer T2The other end L of the secondary side is connected.
The invention has the following beneficial effects:
(1) the converter can reduce the number of capacitors. On one hand, the structure is single-stage power conversion, the pulse width modulation of the high-voltage side is completed through the action combination of front and rear driving H-bridge switching tubes of the sub-modules, and the pulse width modulation voltage wave is coupled by the high-frequency transformer and can be directly supported by a capacitor on the low-voltage direct-current side, so that the capacitor support is not needed on the high-voltage side; on the other hand, all double-frequency power fluctuation of the three-phase structure of the converter is transferred to the common low-voltage direct-current bus and counteracted with each other, so that the common low-voltage direct-current bus does not need a large amount of capacitors for supporting, compared with the traditional two-stage isolation type modular cascade converter, a large amount of voltage-stabilizing capacitors can be reduced, and the converter has the characteristics of high efficiency, small volume, low cost, high power density and the like.
(2) The converter does not require a bidirectional switching tube. Because the polarity of the high-voltage side port voltage of the upper submodule and the high-voltage side port voltage of the lower submodule are always unchanged, a bidirectional switch tube is not needed, and the secondary side current conversion problem and the voltage spike problem of the traditional single-stage converter are avoided.
(3) The converter does not require voltage sharing control. Because the high-voltage side voltage of each module is directly clamped by the voltage of the common low-voltage direct-current bus through the high-frequency transformer, the steady-state and dynamic characteristics of the output voltage of each module are consistent, voltage-sharing control does not need to be additionally added, and the complexity of control is reduced.
Drawings
Fig. 1 is a schematic structural diagram of a conventional two-stage isolated modular cascaded converter;
FIG. 2 is a schematic diagram of the structure of the isolated modular cascaded converter based on the high-frequency chain for single phase and three phase of the present invention
FIG. 3 is a topological structure diagram of a single-stage high-frequency isolation module according to the present invention;
FIG. 4 is a waveform diagram of the output of the single-stage high-frequency isolation module of the present invention;
FIG. 5 is a topology structure diagram of the single-phase high-frequency chain-based isolated modular cascaded converter of the present invention;
FIG. 6 is a topological structure diagram of a star-connected three-phase high-frequency chain-based isolated modular cascaded converter of the present invention;
FIG. 7 is a topological structure diagram of an isolated modular cascaded converter with three phases connected by an angle according to the present invention;
in the figure: 1: a single-stage high-frequency isolated module;
2: an upper sub-module of the single-stage high-frequency isolation module;
21: an upper submodule preceding-stage active H bridge;
22: the upper sub-module is a rear-stage active H bridge;
23: an upper sub-module voltage clamping circuit;
3: a single-stage high-frequency isolated module lower sub-module;
31: a lower submodule preceding-stage active H bridge;
32: a lower sub-module rear-stage active H bridge;
33: a lower sub-module voltage clamping circuit;
10: the single-phase high-frequency chain-based isolated modular cascade converter;
100: the star-connected three-phase high-frequency chain-based isolated modular cascade converter is characterized by comprising three star-connected three-phase high-frequency chain-based isolated modular cascade converters;
101: the angle-connected three-phase high-frequency chain-based isolated modular cascade converter comprises an angle-connected three-phase high-frequency chain-based isolated modular cascade converter;
PL: a low voltage DC positive port;
NL: a low voltage dc negative port;
PH: a high voltage alternating current positive port;
NH: a high voltage ac negative port;
Lf: an AC side filter inductor;
CdcL: a low-voltage DC capacitor;
T1、T2: a high-frequency transformer;
A. b: the low-voltage side positive and negative ports of the single-stage high-frequency isolation type module;
P1、N1: the front-stage active H bridge positive and negative electrode ports of the upper submodule;
P2、N2: front-stage active H bridge positive and negative electrode ports of the lower submodule;
C. o: the positive and negative electrode ports of the upper sub-module rear-stage active H bridge;
o, D: the positive and negative electrode ports of the lower sub-module rear-stage active H bridge;
E. f: high-frequency transformer T1A primary side port;
G. h: high-frequency transformer T1A secondary side port;
I. j: high-frequency transformer T2A primary side port;
K. l: high-frequency transformer T2A secondary side port;
Q1～Q4: an upper sub-module preceding-stage active H-bridge switching tube such as an Insulated Gate Bipolar Transistor (IGBT); q5～Q8: an upper sub-module rear-stage active H-bridge switching tube such as an Insulated Gate Bipolar Transistor (IGBT);
Q9～Q12: a preceding-stage active H-bridge switching tube of the lower sub-module, such as an Insulated Gate Bipolar Transistor (IGBT); q13～Q16: a lower sub-module rear-stage active H-bridge switching tube such as an Insulated Gate Bipolar Transistor (IGBT);
D1～D4: an upper sub-module voltage clamping circuit diode;
D6～D8: a lower sub-module voltage clamping circuit diode;
C1、C2: a voltage clamp circuit capacitor;
R1、R2: a voltage clamp circuit resistor.
Detailed Description
In order that the objects and advantages of the invention will be more clearly understood, the invention is further described in detail below with reference to examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
FIG. 2 shows an embodiment of the present inventionThe topological structure diagram of the single-stage high-frequency isolation module 1 comprises an upper submodule 2, a lower submodule 3 and a low-voltage side direct current capacitor CdcL. The upper submodule 2 comprises a preceding stage active H bridge 21 and a first high-frequency transformer T1A rear-stage active H-bridge 22, a voltage clamp circuit 23; the lower sub-module 3 comprises a preceding-stage active H bridge 31 and a second high-frequency transformer T2A post-stage active H-bridge 32, and a voltage clamp circuit 33. Preceding stage active H bridge positive and negative electrode ports P of upper submodule 21、N1Respectively connected with the front-stage active H-bridge positive and negative electrode ports P of the lower sub-module 32、N2And are connected in parallel to form the low voltage dc positive and negative terminals A, B of the module. In the upper submodule 2, the primary side terminal E, F of the first high-frequency transformer T1 is connected to the front-stage active H-bridge 21, and the secondary side terminal G, H is connected to the rear-stage active H-bridge 22 and the voltage clamp circuit 23. In the lower submodule 3, the primary side terminal I, J of the second high-frequency transformer T2 is connected to the front-stage active H-bridge 31, and the secondary side terminal K, L is connected to the rear-stage active H-bridge 32 and the voltage clamp circuit 33. The high-voltage ac positive and negative terminals C, D of the module are formed by connecting the positive and negative terminals C, O of the rear-stage active H-bridge of the upper submodule 2 and the positive and negative terminals O, D of the rear-stage active H-bridge of the lower submodule 3 in series. Low-voltage side DC capacitor CdcLIn parallel with the low voltage dc port A, B.
When the single-stage high-frequency isolation module works, the modulation ratio of the upper submodule and the lower submodule is the AC-DC mixed modulation ratio duAnd d1(duFor upper sub-module modulation ratio, d1Modulation ratio of lower sub-module), and duAnd d1The device consists of a direct current modulation ratio D and an alternating current modulation ratio D, and the alternating current modulation ratios of different phases are different by 120 degrees. When the DC modulation ratio is 0.5, dmIt is required to be equal to or greater than zero and equal to or less than 0.5 to satisfy formula (1).
Figure BSA0000167183560000061
When the single-stage high-frequency isolation module works, the input voltage of the low-voltage direct-current side is assumed to be VdcLAnd the transformation ratio of the high-frequency transformer winding is k: 1, so that the port voltage of the module meets the formula (2).
Figure BSA0000167183560000071
Figure 3 is a graph of the output voltage waveform of the ac port of the single-stage high-frequency isolated module of the embodiment shown in figure 2, when the module works, low-voltage direct current is input from the low-voltage direct current port A, B, the low-voltage direct current is converted into high-frequency voltage square waves through the switch combination of the preceding-stage active H bridge, is coupled to the rear-stage active H bridge through a high-frequency transformer, and after the switching transformation of the rear-stage active H bridge, the rear-stage active H-bridge port C, O of the upper sub-module outputs a positive-polarity high-frequency voltage square wave with dc and ac components, the rear-stage active H-bridge port O, D of the lower sub-module outputs a negative-polarity high-frequency voltage square wave with dc and ac components, because of the serial connection of the ports, the high-voltage alternating current port C, D of the module outputs high-frequency voltage square waves with positive and negative polarities and only alternating current components, and perfect sine waves can be output after filtering. Assume that the low voltage DC port A, B input voltage of a single module is VdcLWhen the AC modulation ratio is d and the high-frequency transformer winding transformation ratio is k: 1, the output voltage of the high-voltage AC port C, D is
Figure BSA0000167183560000072
Fig. 4 is a topology structure diagram of an embodiment of the single-phase high-frequency-chain-based isolated modular cascaded converter of the present invention. The single-phase converter consists of n single-stage high-frequency isolation modules 1 and an output filter inductor LfAnd a low-voltage DC side capacitor C connected in parallel with the low-voltage DC busdcLThe low-voltage direct-current ports A, B between the modules are connected in parallel on a common low-voltage direct-current bus, PL、NLThe positive and negative terminals of the common low-voltage DC bus are connected in series through an AC side port C, D between modules, and a filter inductor L is connected in series through a C port of the module 1fThen used as a high-voltage alternating current positive electrode port PHThe outgoing line of the D port of the module N is used as a high-voltage alternating-current negative port NH. When the input voltage of the low-voltage DC port A, B is VdcLAc modulation ratio of d, high frequencyWhen the transformation ratio of the transformer windings is k: 1, the output voltage of the high-voltage alternating-current port C, D of the single-phase converter is
Figure BSA0000167183560000073
Fig. 5 is a topology diagram of an embodiment of the three-phase high-frequency-chain-based isolated modular cascaded converter of the present invention using star connection. The three-phase converter 100 comprises three identical single-phase structures 10 and a low-voltage direct-current capacitor C connected in parallel to a low-voltage direct-current busdcLEach single-phase structure 10 is composed of n single-stage high-frequency isolation modules 1 and an output filter inductor LfThe low voltage DC port A, B of each module is connected in parallel to a common low voltage DC bus, PL、NLThe AC ports C, D between the modules of each single-phase structure 10 are connected in series for the positive and negative ports of the common low-voltage DC bus, and the C port of the module 1 of each single-phase structure 10 is connected in series with a filter inductor LfThen as the high-voltage AC positive port P of the phaseH(a)/PH(b))/PH(c)The D port outgoing line of the module N of each single-phase structure 10 is used as the high-voltage alternating-current negative electrode port N of the phaseH(a)/NH(b))/NH(c)High voltage ac negative terminal N of each phaseH(a)/NH(b))/NH(c)Making star connection.
Fig. 6 is a topology diagram of an embodiment of the isolated modular cascaded converter based on high frequency chains in three phases according to the present invention, which uses an angle connection. The three-phase converter 101 comprises three identical single-phase structures 10 and a low-voltage direct-current capacitor C connected in parallel with a low-voltage direct-current busdcLEach single-phase structure 10 is composed of n single-stage high-frequency isolation modules 1 and an output filter inductor LfThe low voltage DC side ports A, B of each module are connected in parallel to a common low voltage DC bus, PL、NLThe AC ports C, D between the modules of each single-phase structure 10 are connected in series for the positive and negative ports of the common low-voltage DC bus, and the C port of the module 1 of each single-phase structure 10 is connected in series with a filter inductor LfThen as the high-voltage AC positive port P of the phaseH(a)/PH(b))/PH(c)The D port outgoing line of the module N of each single-phase structure 10 is used as the high-voltage alternating-current negative electrode port N of the phaseH(a)/NH(b))/NH(c)High voltage ac negative electrode port N of a-phase structureH(a)High-voltage alternating-current positive port P connected with B-phase structureH(b)High voltage AC negative electrode port N of B-phase structureH(b)High-voltage alternating-current positive electrode port P connected with C-phase unitH(c)High voltage AC negative electrode port N of C phase structureH(c)High-voltage alternating-current positive port P connected with A-phase structureH(a)。
The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention.

Claims (10)

1. An isolated modular cascade converter based on a high-frequency chain technology is characterized in that:
the single-phase structure (10) of the converter comprises a filter inductor LfA low voltage DC side capacitor CdcLAnd n single-stage high-frequency isolation type modules (1), wherein the n single-stage high-frequency isolation type modules (1) are connected in an input-parallel-output-series structure, and the low-voltage direct current port (A, B) of each single-stage high-frequency isolation type module (1) is connected in parallel to form a low-voltage direct current port (P) of the single-phase converterL、NL) The high-voltage alternating current ports (C, D) of the single-stage high-frequency isolation type modules (1) are connected in series, and the C port of the first single-stage high-frequency isolation type module (1) is connected in series with a filter inductor LfThen used as a high-voltage alternating current positive electrode port PHThe outgoing line of the D port of the module N is used as a high-voltage alternating-current negative port NH；
The three-phase structure of the converter comprises three single-phase structures (10) and a low-voltage direct-current side capacitor C connected in parallel with a low-voltage direct-current busdcLThe low-voltage direct-current ports of the three single-phase structures (10) are respectively connected in parallel on a low-voltage direct-current bus, and the low-voltage direct-current ports can be divided into star connection (100) and angles according to different connection modes among the high-voltage alternating-current ports of the phase structuresA male connection (101);
the single-stage high-frequency isolation module is composed of an upper sub-module (2), a lower sub-module (3) and a low-voltage direct-current side capacitor CdcLThe upper sub-module (2) and the lower sub-module (3) are respectively composed of a front-stage active H bridge, a high-frequency transformer, a rear-stage active H bridge and a voltage clamping circuit, the front-stage active H bridge is connected with the primary side of the high-frequency transformer, the rear-stage active H bridge and the clamping circuit are connected with the secondary side of the high-frequency transformer, and the positive and negative electrode ports (P) of the front-stage active H bridge of the upper sub-module1、N1) And positive and negative electrode ports (P) of preceding active H bridge of lower submodule2、N2) Are respectively connected in parallel as a low-voltage direct current port (A, B), the rear-stage active H-bridge port is connected in series to form a high-voltage alternating current port (C, D), and a low-voltage direct current side capacitor CdcLThe low-voltage direct current port is connected in parallel; the front-stage active H bridge and the rear-stage active H bridge are both composed of active switching tubes with 4 anti-parallel diodes, the collector of each active switching tube is respectively connected with the cathode of each freewheeling diode, and the emitter is respectively connected with the anode of each freewheeling diode.
2. The isolated modular cascaded converter based on high frequency link technology according to claim 1, wherein: three high-voltage AC negative terminals (N) of a single-phase structure (10) when star connection (100) is adoptedH(a)、NH(b)、NH(c)) Making star connection; high voltage AC negative port (N) of phase A configuration when angular connection (101) is employedH(a)) High voltage AC positive port (P) connected to B phase unitH(b)) High voltage AC negative port of B-phase structure (N)H(b)) High voltage AC positive port (P) connected to C-phase structureH(c)) High voltage AC negative terminal port of C phase structure (N)H(c)) High voltage AC positive port (P) connected with A phase structureH(a))。
3. The isolated modular cascaded converter based on high frequency link technology according to claim 1, wherein: the modulation ratio of the upper submodule (2) is an alternating current-direct current hybrid modulation ratio duD + D, the modulation ratio of the lower sub-module (3) is AC/DC mixed modulationSystem ratio dlD-D, wherein D is a dc common modulation ratio, D is an ac modulation ratio, and the ac modulation ratios between different phases differ by 120 °;
the output voltage of the port (C, O) of the upper sub-module (2) is a positive high-frequency voltage square wave with alternating current and direct current components, the output voltage of the port (O, D) of the lower sub-module (3) is a negative high-frequency voltage square wave with alternating current and direct current components, and the output voltage of the port (C, D) of the single-stage high-frequency isolation module (1) is a positive and negative high-frequency voltage square wave with only alternating current components.
4. The isolated modular cascaded converter based on high frequency link technology according to claim 1, wherein: the preceding-stage active H bridge (21) of the upper submodule (2) comprises a first active switching tube Q1A second active switch tube Q2A third active switch tube Q3And a fourth active switch tube Q4(ii) a First active switch tube Q1And a third active switch tube Q3Series, second active switching tube Q2And a fourth active switch tube Q4In series, with two arms in series, i.e. the first active switching tube Q1Collector and second active switching tube Q2Is connected as the positive electrode port P of the active H bridge1The third active switch tube Q3Emitter and fourth active switching tube Q4Is connected as a negative electrode port N of the active H bridge1(ii) a First active switch tube Q1Emitter and third active switching tube Q3Is connected with a first high-frequency transformer T1A second active switch tube Q connected to the primary side end E2Emitter and fourth active switching tube Q4Is connected with a first high-frequency transformer T1The other terminal F of the primary side is connected.
5. The isolated modular cascaded converter based on high frequency link technology according to claim 1, wherein: the rear-stage active H bridge (22) of the upper submodule (2) comprises a fifth active switching tube Q5A sixth active switchTube Q6A seventh active switch tube Q7And an eighth active switch tube Q8(ii) a Fifth active switch tube Q5And a seventh active switch tube Q7Series, sixth active switch tube Q6And an eighth active switch tube Q8In series, with two arms in series, i.e. fifth active switching tube Q5Collector and sixth active switching tube Q6Is connected as the positive terminal C of the active H bridge, and a seventh active switch tube Q7Emitter and eighth active switching tube Q8The emitter of the active H bridge is connected with a negative electrode port O of the active H bridge; fifth active switch tube Q5Emitter and seventh active switching tube Q7Is connected with a first high-frequency transformer T1A sixth active switch tube Q connected with the secondary side end G6Emitter and eighth active switching tube Q8Is connected with a first high-frequency transformer T1The other terminal H of the secondary side is connected.
6. The isolated modular cascaded converter based on high frequency link technology according to claim 1, wherein: the high-frequency transformer part of the upper sub-module (2) comprises a first high-frequency transformer T1The terminal (E, F) is a first high-frequency transformer T1Two terminals on the primary side, terminal (G, H), are the first high-frequency transformer T1Two terminals of the secondary side, wherein the terminals (E, G) are homonymous terminals; the high-frequency transformer part of the lower sub-module (3) comprises a second high-frequency transformer T2The terminal (I, J) is a second high-frequency transformer T2Two terminals on the primary side, terminal (K, L), being a second high-frequency transformer T2The two terminals on the secondary side, terminals (I, K) are homonymous terminals.
7. The isolated modular cascaded converter based on high frequency link technology according to claim 1, wherein: the voltage clamping circuit (23) of the upper submodule (2) comprises a first diode D1A second diode D2A third diode D3A fourth diode D4A first capacitor C1And a first resistor R1First diode D1And a third diode D3Are respectively connected with the first capacitor C after being connected in series1A first resistor R1Parallel, a second diode D2And a fourth diode D4Are respectively connected with the first capacitor C after being connected in series1A first resistor R1Parallel, first diode D1A second diode D2Cathode and first capacitor C1A first resistor R1Is connected to the anode of a third diode D3A fourth diode D4Anode and first capacitor C1A first resistor R1Is connected to the negative electrode of a first diode D1Anode of and a third diode D3Cathode of, first high-frequency transformer T1A secondary side terminal G connected to a second diode D2Anode of and a fourth diode D4Cathode of, first high-frequency transformer T1The other end H of the secondary side is connected.
8. The isolated modular cascaded converter based on high frequency link technology according to claim 1, wherein: the preceding stage active H bridge (31) of the lower sub-module (3) comprises a ninth active switching tube Q9A tenth active switch tube Q10An eleventh active switch tube Q11And a twelfth active switch tube Q12(ii) a Ninth active switch tube Q9And an eleventh active switch tube Q11Series, tenth active switch tube Q10And a twelfth active switch tube Q12In series, with two arms in series, i.e. ninth active switching tube Q9Collector and tenth active switching tube Q10Is connected as the positive electrode port P of the active H bridge2Eleventh active switch tube Q11Emitter and twelfth active switching tube Q12Is connected as a negative electrode port N of the active H bridge2(ii) a Ninth active switch tube Q9Emitter and eleventh active switching tube Q11Is connected with a second high-frequency transformer T2The original side end I is connected with a tenth active switch tube Q10Emitter and twelfth activeSwitch tube Q12Is connected with a second high-frequency transformer T2The other terminal J of the primary side is connected.
9. The isolated modular cascaded converter based on high frequency link technology according to claim 1, wherein: the rear-stage active H bridge (32) of the lower sub-module (3) comprises a thirteenth active switching tube Q13A fourteenth active switch tube Q14A fifteenth active switch tube Q15And a sixteenth active switch tube Q16(ii) a Thirteenth active switch tube Q13And the fifteenth active switch tube Q15Series, fourteenth active switch tube Q14And a sixteenth active switch tube Q16In series, with two arms in series, i.e. thirteenth active switching tube Q13Emitter and fourteenth active switching tube Q14Is connected as the positive electrode port O of the active H bridge, and a fifteenth active switching tube Q15Collector and sixteenth active switching tube Q16The collector of the active H bridge is connected with a negative electrode port D of the active H bridge; thirteenth active switch tube Q13Collector and fifteenth active switching tube Q15Is connected with a second high-frequency transformer T2A sub-edge connected to the sub-edge, a fourteenth active switch tube Q14Collector and sixteenth active switching tube Q16Is connected with a second high-frequency transformer T2The other terminal L of the secondary side is connected.
10. The isolated modular cascaded converter based on high frequency link technology according to claim 1, wherein: the voltage clamping circuit (33) of the lower submodule (3) comprises a fifth diode D5A sixth diode D6A seventh diode D7An eighth diode D8A second capacitor C2And a second resistor R2Fifth diode D5And a seventh diode D7Are respectively connected with a second capacitor C after being connected in series2A second resistor R2Parallel, sixth diode D6And an eighth diode D8Are respectively connected with a second capacitor C after being connected in series2A second resistor R2Parallel, fifth diode D5A sixth diode D6Cathode and second capacitor C2A second resistor R2Is connected to the anode of a seventh diode D7An eighth diode D8Anode and second capacitor C2A second resistor R2Is connected to the negative pole of a fifth diode D5Anode of and seventh diode D7Cathode of, a second high-frequency transformer T2A sixth diode D connected to the secondary side terminal K6Anode of and the eighth diode D8Cathode of, a second high-frequency transformer T2The other end L of the secondary side is connected.
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