CN111293893B - Three-phase modularized isolation matrix converter topology structure - Google Patents

Three-phase modularized isolation matrix converter topology structure Download PDF

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CN111293893B
CN111293893B CN202010118758.0A CN202010118758A CN111293893B CN 111293893 B CN111293893 B CN 111293893B CN 202010118758 A CN202010118758 A CN 202010118758A CN 111293893 B CN111293893 B CN 111293893B
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CN111293893A (en
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岳舟
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Hunan University of Humanities Science and Technology
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
    • H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
    • H02M5/22—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M5/275—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc 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
    • H02M5/293—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks

Abstract

The invention provides a three-phase modularized isolation matrix converter topological structure, which comprises the following steps: the positive electrode end of the first voltage source is electrically connected with the first end of the first capacitor, and the negative electrode end of the first voltage source is electrically connected with the second end of the first capacitor; the positive electrode end of the second voltage source is electrically connected with the first end of the second capacitor, and the negative electrode end of the second voltage source is electrically connected with the second end of the second capacitor; and the positive end of the third voltage source is electrically connected with the first end of the third capacitor, and the negative end of the third voltage source is electrically connected with the second end of the third capacitor. The three-phase modularized isolation matrix converter topological structure can reduce the volume of the power electronic device and the cost while realizing electric isolation, and simultaneously increases the isolation degree, the modularity and the flexibility of the power electronic device, thereby being very suitable for traction application and low-voltage or medium-voltage future distribution networks with limited space.

Description

Three-phase modularized isolation matrix converter topology structure
Technical Field
The invention relates to the field of power conversion devices, in particular to a topological structure of a three-phase modularized isolation matrix converter.
Background
In 1988 Alesina and venturi proposed the first direct alternating current-to-alternating current (AC-AC) power Converter, called Matrix Converter (MC), in which the output is directly connected to the input through nine bi-directional switches, avoiding large oscillating capacitances, thus providing a single stage solution of high power density and reliability, the topology thus obtained being particularly suitable for applications such as integrated motor drives.
If a direct AC-AC converter is applied to a traction or interconnection Low Voltage (LV) or Medium Voltage (MV) AC grid, an isolation stage must be included to prevent fault propagation, and an increase in the frequency transformer based on the conventional MC can achieve isolation, but at the cost of increasing the volume and weight of the power conversion device, space is limited and expensive in urban centers or transportation systems, such as electric locomotives, etc., and thus, more compact solutions based on medium frequency/high frequency (medium frequency/high frequency) transformers must be studied.
Converters that embed an isolation stage to replace a power frequency transformer are often referred to as solid state transformers (Solid State Transformer, SST), mc Murray first proposed this concept in 1968, but until now new SST is not used for grid interconnection and traction applications, however SST technology remains an evolving field, indeed they have a smaller footprint compared to power frequency transformers, but at the same time with higher complexity and lower reliability SST can be applied to future distribution networks and new traction systems, but it has to be pointed out that SST without energy storage, e.g. based on traditional Mc, has reduced controllability under unbalanced grid conditions due to lack of decoupling elements.
Disclosure of Invention
The invention provides a topological structure of a three-phase modularized isolation matrix converter, which aims to solve the problems of large volume, high cost and low modularity of a traditional power electronic device.
To achieve the above object, an embodiment of the present invention provides a three-phase modular insulation matrix converter topology, including:
the positive electrode end of the first voltage source is electrically connected with the first end of the first capacitor, and the negative electrode end of the first voltage source is electrically connected with the second end of the first capacitor;
the positive electrode end of the second voltage source is electrically connected with the first end of the second capacitor, and the negative electrode end of the second voltage source is electrically connected with the second end of the second capacitor;
a third voltage source, wherein the positive end of the third voltage source is electrically connected with the first end of the third capacitor, and the negative end of the third voltage source is electrically connected with the second end of the third capacitor;
the unit module, the unit module is provided with three groups, the first end of unit module with the first end electricity of first electric capacity is connected, the second end of unit module with the second end electricity of first electric capacity is connected, the third end of unit module with the first end electricity of second electric capacity is connected, the fourth end of unit module with the second end electricity of second electric capacity is connected, the fifth end of unit module with the first end electricity of third electric capacity is connected, the sixth end of unit module with the second end electricity of third electric capacity is connected.
Wherein each group of the unit modules includes:
a first unit, wherein a first end of the first unit is electrically connected with a first end of the first capacitor, and a second end of the first unit is electrically connected with a second end of the first capacitor;
a second unit, wherein a first end of the second unit is electrically connected with a first end of the second capacitor, a second end of the second unit is electrically connected with a second end of the second capacitor, and a third end of the second unit is electrically connected with a third end of the first unit;
and the first end of the third unit is electrically connected with the first end of the third capacitor, the second end of the third unit is electrically connected with the second end of the third capacitor, and the third end of the third unit is electrically connected with the third end of the second unit.
Wherein the first unit, the second unit, and the third unit of the unit module each include:
an input H bridge;
an intermediate frequency/high frequency transformer, a first end of the intermediate frequency/high frequency transformer is electrically connected with a first end of the input H bridge, and a second end of the intermediate frequency/high frequency transformer is electrically connected with a second end of the input H bridge;
and the first end of the output H bridge is electrically connected with the third end of the intermediate frequency/high frequency transformer, and the second end of the output H bridge is electrically connected with the fourth end of the intermediate frequency/high frequency transformer.
Wherein the input H-bridge comprises:
a first bi-directional switch having a first end electrically connected to a first end of the intermediate/high frequency transformer;
a second bidirectional switch, a first end of which is electrically connected with a first end of the first bidirectional switch;
a third bi-directional switch having a first end electrically connected to the second end of the first bi-directional switch;
and the first end of the fourth bidirectional switch is electrically connected with the second end of the intermediate frequency/high frequency transformer and the second end of the third bidirectional switch respectively, and the second end of the fourth bidirectional switch is electrically connected with the second end of the second bidirectional switch.
Wherein the output H-bridge comprises:
a fifth bi-directional switch, a first end of the fifth bi-directional switch being electrically connected to a third end of the intermediate/high frequency transformer;
a sixth bi-directional switch, a first end of the sixth bi-directional switch being electrically connected to a second end of the fifth bi-directional switch, a second end of the sixth bi-directional switch being electrically connected to a fourth end of the intermediate/high frequency transformer;
a seventh bi-directional switch, a first end of the seventh bi-directional switch being electrically connected to the first end of the fifth bi-directional switch;
and the first end of the eighth bidirectional switch is electrically connected with the second end of the seventh bidirectional switch, and the second end of the eighth bidirectional switch is electrically connected with the second end of the sixth bidirectional switch.
Wherein each group of the unit modules is further provided with:
an inductor, a first end of the inductor is electrically connected with a second end of a fifth bidirectional switch of the first unit, a second end of a seventh bidirectional switch of the first unit is electrically connected with a second end of a fifth bidirectional switch of the second unit, and a second end of a seventh bidirectional switch of the second unit is electrically connected with a second end of a fifth bidirectional switch of the third unit;
and the first end of the current source is electrically connected with the second end of the inductor, and the second end of the current source is electrically connected with the second end of the seventh bidirectional switch of the third unit.
The scheme of the invention has the following beneficial effects:
according to the three-phase modularized isolation matrix converter topological structure, electrical isolation is achieved, meanwhile, the size of a power electronic device can be reduced, cost is reduced, meanwhile, isolation degree, modularity and flexibility of the power electronic device are improved, and the three-phase modularized isolation matrix converter topological structure is very suitable for traction application and low-voltage or medium-voltage future distribution networks with limited space.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 is a schematic view of the structure of the unit module according to the present invention;
FIG. 3 is a basic waveform diagram of the result of the first unit switching function of the present invention;
FIG. 4 is a duty cycle configuration diagram of the present invention;
FIG. 5 is a waveform diagram showing the result of the switching function of the cell output voltage according to the present invention;
FIG. 6 is a specific circuit diagram of a single cell of the present invention;
FIG. 7 shows a single cell of the present invention during a switching period T S An ideal commutation waveform diagram in the interior;
FIG. 8 is a state transition diagram of the present invention;
fig. 9 is a schematic diagram of a bidirectional switch structure according to the present invention.
[ reference numerals description ]
1-a first voltage source; 2-a second voltage source; 3-a third voltage source; 4-a first capacitance; 5-a second capacitor; 6-a third capacitor; 7-unit modules; 8-input H-bridge; 9-an intermediate/high frequency transformer; 10-output H-bridge; 11-a first unit; 12-a second unit; 13-a third unit; 14-a first bi-directional switch; 15-a second bi-directional switch; 16-a third bi-directional switch; 17-fourth bidirectional switch; 18-a fifth bi-directional switch; 19-a sixth bi-directional switch; 20-seventh bi-directional switch; 21-eighth bi-directional switch; 22-inductance; 23-current source.
Detailed Description
In order to make the technical problems, technical solutions and advantages to be solved more apparent, the following detailed description will be given with reference to the accompanying drawings and specific embodiments.
Aiming at the problems of large volume, high cost and low modularity of the existing power electronic device, the invention provides a three-phase modularized isolation matrix converter topological structure.
As shown in fig. 1 to 9, an embodiment of the present invention provides a three-phase modular isolated matrix converter topology, including: a first voltage source 1, wherein the positive end of the first voltage source 1 is electrically connected with the first end of a first capacitor 4, and the negative end of the first voltage source 1 is electrically connected with the second end of the first capacitor 4; a second voltage source 2, wherein the positive terminal of the second voltage source 2 is electrically connected with the first terminal of the second capacitor 5, and the negative terminal of the second voltage source 2 is electrically connected with the second terminal of the second capacitor 5; a third voltage source 3, wherein the positive terminal of the third voltage source 3 is electrically connected with the first terminal of a third capacitor 6, and the negative terminal of the third voltage source 3 is electrically connected with the second terminal of the third capacitor 6; the unit module 7, the unit module 7 is provided with three groups, the first end of unit module 7 with the first end electricity of first electric capacity 4 is connected, the second end of unit module 7 with the second end electricity of first electric capacity 4 is connected, the third end of unit module 7 with the first end electricity of second electric capacity 5 is connected, the fourth end of unit module 7 with the second end electricity of second electric capacity 5 is connected, the fifth end of unit module 7 with the first end electricity of third electric capacity 6 is connected, the sixth end of unit module 7 with the second end electricity of third electric capacity 6 is connected.
Wherein each set of the unit modules 7 includes: a first unit 11, wherein a first end of the first unit 11 is electrically connected with a first end of the first capacitor 4, and a second end of the first unit 11 is electrically connected with a second end of the first capacitor 4; a second unit 12, wherein a first end of the second unit 12 is electrically connected to a first end of the second capacitor 5, a second end of the second unit 12 is electrically connected to a second end of the second capacitor 5, and a third end of the second unit 12 is electrically connected to a third end of the first unit 11; and a third unit 13, wherein a first end of the third unit 13 is electrically connected with a first end of the third capacitor 6, a second end of the third unit 13 is electrically connected with a second end of the third capacitor 6, and a third end of the third unit 13 is electrically connected with a third end of the second unit 12.
Wherein the first unit 11, the second unit 12 and the third unit 13 of the unit module 7 each comprise: an input H-bridge 8; an intermediate frequency/high frequency transformer 9, a first end of the intermediate frequency/high frequency transformer 9 is electrically connected with a first end of the input H-bridge 8, and a second end of the intermediate frequency/high frequency transformer 9 is electrically connected with a second end of the input H-bridge 8; an output H-bridge 10, a first end of the output H-bridge 10 being electrically connected to a third end of the intermediate/high frequency transformer 9, and a second end of the output H-bridge 10 being electrically connected to a fourth end of the intermediate/high frequency transformer 9.
The three-phase modular isolated matrix converter topology according to the above embodiment of the present invention, with the units consisting of the input H-bridge 8, the output H-bridge 10 and one of the medium/high frequency transformers 9, a plurality of units being repeated to maintain modularity, each unit being a single-phase to single-phase ac-ac power converter, since the output frequency has to be always matched to the input frequency, the application of the individual units being limited, in order to be able to achieve an output frequency adaptation, in which three separate single-phase to single-phase ac power converters and the medium/high frequency transformers 9 are combined, each output phase being connected in series on the secondary side, in order to use the modulation technique of a conventional matrix converter, for example 50% venturi modulation, for the modular isolated matrix converter, the first step being to identify the Modulation States (MS) available in the three-phase modular isolated matrix converter topology, the input H-bridge 8 and the output H-bridge 10 in fig. 2 being considered, the input end having the first voltage source 1, the second voltage source 2 and the third voltage source 3 and the current source 3 and the input H-bridge 10 being the ideal voltage source 1, the input end being the input H-bridge 3 and the input H-bridge 9 being the ideal H-bridge (v/v-bridge) being defined by the general-bridge 1):
Figure BDA0002392307300000061
where i represents an input end, o represents an output end, K represents three input phases, k= A, B, C, a is an input phase where the first voltage source 1 is located, B is an input phase where the second voltage source 2 is located, C is an input phase where the third voltage source 3 is located, j represents an output phase, j=a, B, C, a, B, C respectively correspond to each group of unit modules 7.
To comply with the constraint that the input voltage source cannot be shorted and the output current source cannot be opened during operation, three MS matrices are available as shown in equation (2), MS 1 And MS (MS) 2 Is in two active states, and the MS 0 Is a zero state matrix, note that the zero state can be implemented with two different modulation state matrices, but the two matrices have the same effect on the modulation waveform.
Figure BDA0002392307300000062
The basic principle of operation of a modular isolated matrix converter is to first convert a low frequency input voltage waveform to a 50% duty cycle intermediate/high frequency voltage waveform, as shown in fig. 3 (b), simply at a switching frequency f sw The input voltage is regulated, which corresponds to the implementation of a switching function on three of said input H-bridges 8 as shown in equation (3), T S Is a switching period, in the first period 0<t<T S The inner equation is abbreviated as equation (3) and the other equations will take the same compact notation. As can be seen from equation (3), the modulation state MS 1 Will be applied in the first half of the switching cycle, i.e. from 0 to 0.5T S Let V TK ＝V Ki While modulating state MS 2 Will be applied to the other half of the switching cycle, i.e. from 0.5T S To T S Let V TK ＝-V Ki Thus, all of the input H-bridges 8 generate 50% duty cycle mid/high frequency waveforms at their mid/high frequency transformer 9 ends.
Figure BDA0002392307300000071
The 50% duty cycle modulation of the input H-bridge 8 is only used to provide the intermediate/high frequency transformer 9 with a suitable voltage waveform irrespective of the value of the modulated wave, instead of the voltage V of the output H-bridge 10 in fig. 2 Ko Defined according to the 50% venturi modulation of formula (4), wherein D kj Is the duty cycle of the input phase K when the output phase j produces the output voltage, and from equations (4) - (6), the equations are the same as those used in conventional matrix converters, where the contribution time of each input to the output voltage is determined by venturi modulation.
Figure BDA0002392307300000072
V Ki ＝V m sin(ω i t+φ K ) (5)
V jo ＝qV m sin(ω o t+φ j ) (6)
Wherein V is Ki For three-phase input voltage, V jo Is a three-phase output voltage.
Wherein the input H-bridge 8 comprises: a first bidirectional switch 14, a first end of the first bidirectional switch 14 is electrically connected with a first end of the intermediate frequency/high frequency transformer 9; a second bidirectional switch 15, a first end of the second bidirectional switch 15 is electrically connected with a first end of the first bidirectional switch 14; a third bi-directional switch 16, a first end of the third bi-directional switch 16 being electrically connected to a second end of the first bi-directional switch 14; a fourth bi-directional switch 17, wherein a first end of the fourth bi-directional switch 17 is electrically connected to a second end of the intermediate frequency/high frequency transformer 9 and a second end of the third bi-directional switch 16, respectively, and a second end of the fourth bi-directional switch 17 is electrically connected to a second end of the second bi-directional switch 15.
Wherein the output H-bridge 10 comprises: a fifth bi-directional switch 18, a first terminal of the fifth bi-directional switch 18 being electrically connected to a third terminal of the intermediate/high frequency transformer 9; a sixth bi-directional switch 19, a first end of the sixth bi-directional switch 19 being electrically connected to a second end of the fifth bi-directional switch 18, a second end of the sixth bi-directional switch 19 being electrically connected to a fourth end of the intermediate/high frequency transformer 9; a seventh bi-directional switch 20, a first end of the seventh bi-directional switch 20 being electrically connected to a first end of the fifth bi-directional switch 18; an eighth bi-directional switch 21, a first end of the eighth bi-directional switch 21 is electrically connected to the second end of the seventh bi-directional switch 20, and a second end of the eighth bi-directional switch 21 is electrically connected to the second end of the sixth bi-directional switch 19.
The three-phase modular isolation matrix converter topology according to the above embodiment of the present invention is provided with three sets of three-phase to single-phase structures, only one set of three-phase to single-phase structures being considered here for simplicity of analysis. Fig. 4 shows the duty cycle configuration in this simplified case, which may be realized in each of said output H-bridges 10 of the modular isolating matrix converter by means of the switching functions (7), (8) and (9) of fig. 4Equation (7) is to be applied to the output H-bridge 10 of the first unit 11, in equation (7), the duty ratio D Aa May be less than or equal to 0.5, i.e. D Aa T S ≤0.5T S Or greater than 0.5, i.e. D Aa T S >0.5T S . In the case where the duty ratio DAa is less than or equal to 0.5, condition D Aa T S ≤0.5T S Effectively, and in equation (7) there may be two time intervals on the basis of which two MS matrices, i.e. MS, are applied 1 And MS (MS) 0 . If D is satisfied Aa T S ≤0.5T S Is to be an active state matrix MS 1 Applying for a period of time, wherein the time interval is more than or equal to 0 and less than or equal to t and less than or equal to D Aa T S While zero state matrix MS 0 Will be applied to the remaining D Aa T S <t≤T S Within a time interval. Likewise, the switching function equation (8) will be applied to the output H-bridge 10 of the second cell 12, e.g., if the first condition, D in equation (8) Aa T S ≤0.5T S ≤(D Aa +D Ba )T S If true, there are a total of four intervals, where the state MS 0 Will be applied to the interval 0.ltoreq.t.ltoreq.D Aa T S ，MS 1 Applied to the interval D Aa T S <t≤0.5T S ，MS 2 Applied to the interval of 0.5T S <t<(D Aa +D Ba )T S ，MS 0 Applied to the remaining time interval (D Aa +D Ba )T S <t≤T S Other conditions and ranges of all switching functions in the formulas (7), (8) and (9) can be understood according to the illustrated method.
Figure BDA0002392307300000081
Figure BDA0002392307300000091
Figure BDA0002392307300000092
It is noted that the formulas (7), (8) and (9) are written assuming that all the input H-bridges 8 are synchronously offset, so that the primary voltage applied to each of the intermediate/high frequency transformers 9 is V TK And modulated by a corresponding said output H-bridge 10, equal to the corresponding phase voltage of the first half of the switching cycle and the phase voltage V of the other half Ki 。
The total output voltage V in FIG. 5 ao Is the sum of the output voltages of the individual cells, since the output H-bridge 10 of the three-phase to single-phase configuration in FIG. 2 is connected in series, cell voltage V Ko The expression of (2) is summed up by the expression (7), the expression (8) and the expression (9) to obtain the expression (10), wherein the expression (10) is the generated total output voltage V ao Instantaneous output voltage V ao Can also be written as equation (11), which means the input voltage V Ai Will appear at the output, i.e. V ao ＝V Ai The duration time t is more than or equal to 0 and less than or equal to D Aa T S ，V Ai This follows the duty cycle configuration of the conventional matrix converter shown in fig. 4.
Figure BDA0002392307300000093
Figure BDA0002392307300000094
For practical implementations of equations (7), (8) and (9), the required states for each cell in FIG. 2 are MS, respectively Ki MS Ko ＝[MS 1 MS 1 ,MS 2 MS 2 ,MS 1 MS 0 ,MS 2 MS 0 ]In fig. 6, the output voltage waveform and the input and output currents have harmonic content, and the discussion of the harmonics of the present invention is limited to the voltage V of the intermediate/high frequency transformer 9, considering that the output voltage spectrum of the modular isolated matrix converter is identical to the output voltage spectrum of the conventional matrix converter TK The Fourier series of which is shown in formula (12), for the intermediate/high frequency variationsThe design of the press 9 is of vital importance. In contrast, the cell output voltage V given in the formula (7), the formula (8) and the formula (9) Ko Is used only to verify the modulation method, each cell outputting a voltage V by ignoring harmonics at the switching frequency Ko Given in equation (13), due to the series connection of the output H-bridge 10 of the first, second and third units 11, 12 and 13, these components are reduced to as shown in equation (14) because of V ao The other terms in (2) are cancelled in the summation and equation (14) demonstrates that 50% venturi modulation is suitable for a three-phase modular isolated matrix converter topology.
Figure BDA0002392307300000101
Figure BDA0002392307300000102
Figure BDA0002392307300000103
The voltage regulation ratio of the three-phase modular isolation matrix converter topology depends on the turns ratio of the intermediate/high frequency transformer 9, but assuming the turns ratio of the intermediate/high frequency transformer 9 is 1, a maximum voltage regulation ratio of 0.86 can be achieved by injecting 3 rd harmonic adjustment duty cycle formula (4).
Wherein each group of the unit modules 7 is further provided with: an inductor, a first end of the inductor is electrically connected to a second end of a fifth bidirectional switch 18 of the first unit 11, a second end of a seventh bidirectional switch 20 of the first unit 11 is electrically connected to a second end of a fifth bidirectional switch 18 of the second unit 12, and a second end of a seventh bidirectional switch 20 of the second unit 12 is electrically connected to a second end of a fifth bidirectional switch 18 of the third unit 13; a current source 23, a first end of the current source 23 is electrically connected to the second end of the inductor, and a second end of the current source 23 is electrically connected to the second end of the seventh bi-directional switch 20 of the third unit 13.
The three-phase modular isolated matrix converter topology according to the above embodiment of the present invention, in which the analysis of the three-phase modular isolated matrix converter topology modulation technique assumes that the semiconductor device is ideal, is characterized by being capable of instantaneous switching, and in addition, the intermediate frequency/high frequency transformer 9 is considered to be ideal, with zero leakage inductance, and in which the modulation is implemented in the actual three-phase modular isolated matrix converter topology, neither assumption above holds, and therefore the modulation must be enhanced by an appropriate strategy to ensure safe commutation of the bidirectional switch, and by improving the four-step commutation used in the conventional matrix converter, the switching time can be easily considered, whereas the safe commutation technique is further elucidated in view of the non-zero leakage inductance of the intermediate frequency/high frequency transformer 9.
In a conventional matrix converter, where the commutation method is designed to safely change the state of the bi-directional switch without opening the output current or shorting the input voltage source, each bridge can implement an independent four-step commutation method, as long as the influence of leakage inductance of the mid/high frequency transformer 9 is ignored. However, in the case of non-negligible leakage inductance, when the output H-bridge 10 in one of the cells commutates, the standard four-step commutation method can lead to an overvoltage on the semiconductor device, since commutation of the output H-bridge 10 requires a current I through the leakage inductance TK Is always at +I ao (grid current) and-I ao Depending on the state of the output H-bridge 10.
To highlight this phenomenon, FIG. 7 shows the switching period T S An example of an ideal commutation waveform in an inner single cell, as can be seen from FIG. 7, is seen from MS 1 MS 1 To MS 2 MS 2 State transition of (2) requires transformer current I TB from-I ao And +I ao Abrupt inversion, which will produce voltage spikes in the actual transformer where leakage inductance is not negligible. As a result, only when all of the input H-bridges 8 andthe output H-bridge 10 has dissipative clamping to prevent overvoltage, standard four-step commutation can be applied to the three-phase modular isolated matrix converter topology, which results in additional losses, since the clamping circuit is triggered each time the modulator needs a state change corresponding to the leakage inductance current reversal, reducing the leakage inductance can alleviate but not eliminate the problem, parallel or series capacitors can be used on the intermediate/high frequency transformer 9 to achieve safe commutation, however, these choices are at the cost of reduced power density and increased power loss.
With additional states in the three-phase modular isolating matrix converter topology, which are not necessary under ideal conditions but are necessary in handling leakage inductance problems, a current decoupling phase is introduced here, during which the output H-bridge 10 is temporarily in a controlled short-circuit state, during which the leakage inductance current driven by the input voltage is reversed, the modular isolating matrix converter states being selected such that when the leakage inductance current matches the output current value, the temporary output short-circuit ends naturally. Thus, the short circuit is controllable, requiring only a commutation sequence of a suitably fixed time, which method ensures that the safe commutation of the clamp protection is not triggered during most of the power frequency cycles, except during intervals when the available input voltage is insufficient to drive the leakage current, i.e. near zero crossings of the input voltage.
Based on the proposed commutation scheme in fig. 8 a Finite State Machine (FSM) is implemented to move between the steady state of fig. 6, in which the commutation path is indicated by an arrow, the short commutation state is indicated by a small circle, the steady state is indicated by a large gray circle, the CS (commutation state) matrix of the input H-bridge 8 and the output H-bridge 10 of a single cell can be represented by equation (15) like the MS matrix, wherein each bi-directional switch consists of two Insulated Gate Bipolar Transistors (IGBTs). For example, in fig. 9, a bi-directional switch S WKi Including insulated gate bipolar transistor S in a common collector configuration WK0i And insulated gate bipolar transistor S WK1i The definition of CS matrix is expressed by formula (16), and the state change variable S N Store information about the next stability requiredInformation of state T com Controlling the time delay between commutation states determines the delay time T for all commutation steps for simplicity com For example, assuming the finite state machine is in swap state BB, the counter will start and continue counting until it reaches a value equal to T com And once the counter reaches T com The finite state machine will move to the next switching state, HH, which resets the counter to zero, V Ki Representing input voltage, I ao Representing the output current.
Figure BDA0002392307300000121
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Figure BDA0002392307300000122
In the configuration of the three-phase modular isolating matrix converter topology duty cycle, by selecting the most suitable combination of available input voltages, the output voltage waveform required for each output phase can be generated, so that the modulation technique used for the development of the traditional matrix converter is also suitable for the three-phase modular isolating matrix converter topology, and therefore, the three-phase modular isolating matrix converter topology has the same performance at the input and output ends as the traditional matrix converter, namely the same characteristics as the traditional matrix converter, has the advantages of embedded and distributed MF/FH isolation and modularization, and in addition, in the three-phase modular isolating matrix converter, the semiconductor stress is distributed among a large number of increased devices, the stress of the semiconductor device is greatly reduced, the three-phase modular isolating matrix converter topology can also reduce the volume of a power electronic device and the cost thereof while realizing electrical isolation, and the isolation degree, the modularity and the flexibility of the power electronic device are very suitable for traction application and space-limited low-voltage (LV) or medium-voltage (MV) distribution network.
While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present invention, and such modifications and adaptations are intended to be comprehended within the scope of the present invention.

Claims (4)

1. A three-phase modular isolated matrix converter topology comprising:
the positive electrode end of the first voltage source is electrically connected with the first end of the first capacitor, and the negative electrode end of the first voltage source is electrically connected with the second end of the first capacitor;
the positive electrode end of the second voltage source is electrically connected with the first end of the second capacitor, and the negative electrode end of the second voltage source is electrically connected with the second end of the second capacitor;
a third voltage source, wherein the positive end of the third voltage source is electrically connected with the first end of the third capacitor, and the negative end of the third voltage source is electrically connected with the second end of the third capacitor;
the unit module is provided with three groups, a first end of the unit module is electrically connected with a first end of the first capacitor, a second end of the unit module is electrically connected with a second end of the first capacitor, a third end of the unit module is electrically connected with a first end of the second capacitor, a fourth end of the unit module is electrically connected with a second end of the second capacitor, a fifth end of the unit module is electrically connected with a first end of the third capacitor, and a sixth end of the unit module is electrically connected with a second end of the third capacitor;
each set of the unit modules includes:
a first unit, wherein a first end of the first unit is electrically connected with a first end of the first capacitor, and a second end of the first unit is electrically connected with a second end of the first capacitor;
a second unit, wherein a first end of the second unit is electrically connected with a first end of the second capacitor, a second end of the second unit is electrically connected with a second end of the second capacitor, and a third end of the second unit is electrically connected with a third end of the first unit;
a third unit, wherein a first end of the third unit is electrically connected with a first end of the third capacitor, a second end of the third unit is electrically connected with a second end of the third capacitor, and a third end of the third unit is electrically connected with a third end of the second unit;
the first unit, the second unit, and the third unit of the unit module each include:
an input H bridge;
an intermediate frequency/high frequency transformer, a first end of the intermediate frequency/high frequency transformer is electrically connected with a first end of the input H bridge, and a second end of the intermediate frequency/high frequency transformer is electrically connected with a second end of the input H bridge;
and the first end of the output H bridge is electrically connected with the third end of the intermediate frequency/high frequency transformer, and the second end of the output H bridge is electrically connected with the fourth end of the intermediate frequency/high frequency transformer.
2. The three-phase modular isolation matrix converter topology of claim 1, wherein the input H-bridge comprises:
a first bi-directional switch having a first end electrically connected to a first end of the intermediate/high frequency transformer;
a second bidirectional switch, a first end of which is electrically connected with a first end of the first bidirectional switch;
a third bi-directional switch having a first end electrically connected to the second end of the first bi-directional switch;
and the first end of the fourth bidirectional switch is electrically connected with the second end of the intermediate frequency/high frequency transformer and the second end of the third bidirectional switch respectively, and the second end of the fourth bidirectional switch is electrically connected with the second end of the second bidirectional switch.
3. The three-phase modular isolation matrix converter topology of claim 2, wherein the output H-bridge comprises:
a fifth bi-directional switch, a first end of the fifth bi-directional switch being electrically connected to a third end of the intermediate/high frequency transformer;
a sixth bi-directional switch, a first end of the sixth bi-directional switch being electrically connected to a second end of the fifth bi-directional switch, a second end of the sixth bi-directional switch being electrically connected to a fourth end of the intermediate/high frequency transformer;
a seventh bi-directional switch, a first end of the seventh bi-directional switch being electrically connected to the first end of the fifth bi-directional switch;
and the first end of the eighth bidirectional switch is electrically connected with the second end of the seventh bidirectional switch, and the second end of the eighth bidirectional switch is electrically connected with the second end of the sixth bidirectional switch.
4. A three-phase modular isolation matrix converter topology according to claim 3, characterized in that each set of said cell modules is further provided with:
an inductor, a first end of the inductor is electrically connected with a second end of a fifth bidirectional switch of the first unit, a second end of a seventh bidirectional switch of the first unit is electrically connected with a second end of a fifth bidirectional switch of the second unit, and a second end of a seventh bidirectional switch of the second unit is electrically connected with a second end of a fifth bidirectional switch of the third unit;
and the first end of the current source is electrically connected with the second end of the inductor, and the second end of the current source is electrically connected with the second end of the seventh bidirectional switch of the third unit.
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