Transformer and parallel multilevel convertor

Abstract

Disclosed are a transformer and a parallel multilevel convertor. The transformer of the present invention is a transformer of a parallel multilevel convertor, and comprises a primary winding and a secondary winding, the transformer being characterized in that: the secondary winding includes a (2-1)-th winding and a (2-2)-th winding that are separated independently of each other and that provide power, transmitted from the primary winding, to a first module and a second module, respectively; and the (2-1)-th winding and the (2-2)-th winding are connected in different ways so as to output voltages having the same magnitude and different phases.

Description

Transformers and Parallel Multilevel Converters

[0001] The present invention relates to a transformer and a parallel multilevel converter.

[0002]

[0003] As the capacity of power conversion systems gradually increases, the use of multilevel converters is increasing due to the voltage withstand limitations of semiconductor switches.

[0004] A multi-level converter is a device that converts AC power into DC power or DC power into AC power using multiple sub-modules, and operates by controlling each sub-module into charging, discharging, or bypass states.

[0005] Multilevel converters are utilized in High-Voltage Direct Current (HVDC) transmission, Static Synchronous Compensators (STATCOM), and motor drives due to their advantages, such as easy voltage level expansion through the connection of a large number of sub-modules and the ability to obtain excellent output through high voltage levels even at low switching frequencies.

[0006] However, in multi-level converters, the imbalance between multiple DC voltage levels causes overload on the output filter, and because the DC voltages are not properly smoothed, the lifespan of the output filter decreases and heat generation increases. This leads to a problem where the reliability of the entire system is reduced.

[0007] The background technology of the present invention is disclosed in Korean Registered Patent Publication No. 10-2524800 (April 19, 2023), titled ‘Modular multi-level converter and method of operation thereof’.

[0008]

[0009] The present invention was devised to improve upon the aforementioned problems, and an objective according to one aspect of the present invention is to provide a transformer and a parallel multi-level converter that cancel out the third harmonic of the midpoint voltage and smooth the midpoint voltage by winding two secondary windings that are independently separated from each other in different ways to cause phase delay.

[0010]

[0011] A transformer according to one aspect of the present invention is a transformer of a parallel multi-level converter, comprising a primary winding and a secondary winding, wherein the secondary winding comprises a 2-1st winding and a 2-2nd winding that are independently separated from each other and transmit power transmitted from the primary winding to a first module and a second module, respectively, and wherein the 2-1st winding and the 2-2nd winding are connected in different ways such that the voltages are output with the same magnitude and different phases.

[0012] The present invention is characterized in that the primary winding is Y-connected, the secondary primary winding is Y-connected, the secondary secondary winding is inverse Y-connected, and each phase of the secondary secondary winding is connected with a polarity and sign different from that of the primary winding.

[0013] The a, b, and c phases of the primary winding of the present invention are connected to correspond to the -b, -c, and -a phases of the secondary winding, respectively.

[0014] A parallel multi-level converter according to one aspect of the present invention comprises a primary winding and a secondary winding, wherein the secondary winding is independently separated from each other and includes a transformer comprising a 2-1st winding and a 2-2nd winding that converts the voltage of a three-phase commercial power supply delivered from the primary winding; a first module that converts the AC power supplied from the 2-1st winding into DC power; a second module that converts the AC power supplied from the 2-2nd winding into DC power; and an output unit that outputs the DC power output from the first module and the second module, wherein the 2-1st winding and the 2-2nd winding are connected in different ways so that the voltages are output with the same magnitude and different phases.

[0015] The present invention is characterized in that the primary winding is Y-connected, the secondary primary winding is Y-connected, the secondary secondary winding is inverse Y-connected, and each phase of the secondary secondary winding is connected with a polarity and sign different from that of the primary winding.

[0016] The a, b, and c phases of the primary winding of the present invention are connected to correspond to the -b, -c, and -a phases of the secondary winding, respectively.

[0017]

[0018] A transformer and a parallel multilevel converter according to one aspect of the present invention wind two secondary windings that are independently separated from each other in different ways to cause phase delay, thereby canceling out the third harmonic of the midpoint voltage and smoothing the midpoint voltage.

[0019] A transformer and a parallel multilevel converter according to another aspect of the present invention can suppress voltage distortion, thereby reducing the size of the output filter of the multilevel converter and increasing the lifespan of the multilevel converter due to reduced heat generation.

[0020]

[0021] FIG. 1 is a circuit diagram of a parallel multilevel converter according to one embodiment of the present invention.

[0022] FIGS. 2a and FIGS. 2b are drawings illustrating examples of YY connection between the primary side of a transformer and the secondary side of a first module, respectively, according to an embodiment of the present invention.

[0023] Figure 3 is a waveform diagram according to the wiring method of Figures 2a and 2b.

[0024] FIGS. 4a and FIGS. 4b are drawings illustrating examples of Y-Inverse Y connections between the primary side of a transformer and the secondary side of a second module, respectively, according to an embodiment of the present invention.

[0025] Figure 5 is a waveform diagram according to the wiring method of Figures 4a and 4b.

[0026]

[0027] The following describes an embodiment of a transformer and a parallel multilevel converter according to an embodiment of the present invention. In this process, the thickness of lines or the size of components shown in the drawings may be exaggerated for clarity and convenience of explanation. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intention or convention of the user or operator. Therefore, the definitions of these terms should be based on the content throughout this specification.

[0028] The present invention may be implemented in various different forms and is not limited to the embodiments described herein. Furthermore, in order to clearly explain the invention in the drawings, parts unrelated to the description have been omitted, and similar parts throughout the specification have been given similar reference numerals.

[0029] Throughout the specification, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0030] The implementations described herein may be implemented, for example, as methods or processes, devices, software programs, data streams, or signals. Even if discussed only in the context of a single form of implementation (e.g., discussed only as a method), the implementation of the discussed features may also be implemented in other forms (e.g., devices or programs). Devices may be implemented in appropriate hardware, software, and firmware, etc. Methods may be implemented in devices such as processors, which generally refer to processing devices including, for example, computers, microprocessors, integrated circuits, or programmable logic devices.

[0031]

[0032] FIG. 1 is a circuit diagram of a parallel multilevel converter according to one embodiment of the present invention.

[0033] Referring to FIG. 1, a parallel multi-level converter according to one embodiment of the present invention may include a power supply unit (100), a transformer (200), a first module (300), a second module (400), and an output unit (500).

[0034] The power supply unit (100) can receive three-phase AC power inputs, for example, phase a, phase b, and phase c, and supply them to the transformer (200).

[0035] The transformer (200) can change the voltage of the three-phase AC power supplied from the power supply unit (100).

[0036] The transformer (200) may include a primary winding (210) and a secondary winding (220).

[0037] The primary winding (210) can be connected to the power supply unit (100).

[0038] The secondary winding (220) may include a 2-1st winding (2321) and a 2-2nd winding (222) that are separated independently of each other.

[0039] The 2-1 side winding (221) is connected to the first rectifier (320) of the first module (300) and can transmit power from the primary side winding (210) to the first module (300).

[0040] The primary winding (210) of the transformer (200) can be Y-connected with a three-phase AC power source. The secondary primary winding (221) of the transformer (200) can be Y-connected. That is, as the primary winding (210) of the transformer (200) is Y-connected and the secondary primary winding (221) is also YY-connected, the a-phase, b-phase, and c-phase of the primary winding (210) of the transformer (200) can be electrically connected to the a-phase, b-phase, and c-phase of the secondary primary winding (221).

[0041] FIGS. 2a and FIGS. 2b are drawings illustrating examples of YY connection between the primary side of a transformer and the secondary side of a first module according to an embodiment of the present invention, respectively, and FIG. 3 is a waveform diagram according to the connection method of FIGS. 2a and FIG. 2b.

[0042] As shown in FIGS. 2a and 2b, the primary winding (210) of the transformer (200) is connected in Y with a three-phase AC power source, and the secondary primary winding (221) of the transformer (200) is connected in Y, so that the primary winding (210) and the secondary primary winding (221) can be connected in YY. Accordingly, the voltages of phases a, b, and c of the primary winding (210) can be transmitted to phases a, b, and c of the secondary primary winding (221) with the same magnitude and phase. That is, as the primary winding (210) and the secondary primary winding (221) are connected in YY, as shown in FIG. 3, the magnitude of the voltages of the primary winding (210) and the secondary primary winding (221) of the transformer (200) are the same and the phases are the same.

[0043] The 2-secondary winding (222) is connected to the second rectifier (420) of the second module (400) and can transmit power from the primary winding (210) to the second module (400).

[0044] The secondary winding (222) of the transformer (200) can be inverse Y connected with the second rectifier (420) of the second module (400). Here, inverse Y connection means connecting each phase of the secondary winding (222) of the transformer (200) with a different polarity and sign from each phase of the primary winding (210). That is, the a, b, and c phases of the primary winding (210) of the transformer (200) are insulated from the -b, -c, and -a phases of the secondary winding (222), respectively, and can be connected to the -b, -c, and -a phases in a corresponding manner.

[0045] FIGS. 4a and FIGS. 4b are drawings illustrating examples of Y-Inverse Y connections between the primary side of a transformer and the secondary side of a second module according to an embodiment of the present invention, respectively, and FIG. 5 is a waveform diagram according to the connection method of FIGS. 4a and FIG. 4b.

[0046] As shown in FIG. 4a and FIG. 4b, the primary winding (210) of the transformer (200) is Y-connected and the secondary winding (222) of the transformer (200) is inverse Y-connected with the second module (400). As shown in FIG. 5, the voltages of phases a, b, and c of the primary winding (210) are transmitted to phases a, b, and c of the secondary winding (222) with the same magnitude, and a phase delay of 60 degrees may occur.

[0047] As described above, according to the YY connection of the primary winding (210) and the secondary primary winding (221) of the transformer (200), a voltage of the same magnitude and phase as that of the primary winding (210) can be generated in the secondary primary winding (221) and applied to the first module (300). Additionally, according to the Y-inverse Y connection of the primary winding (210) and the secondary secondary winding (222) of the transformer (200), a voltage of the same magnitude as that of the primary winding (210) but with a phase delayed by 60 degrees can be generated in the secondary secondary winding (222) and applied to the second module (400). That is, the secondary primary winding (221) and the secondary secondary winding (222) can be wound such that their respective voltages are of the same magnitude and output with different phases.

[0048] The first module (300) can convert AC power input from the second-first winding (221) of the transformer (200) into DC power. The first module (300) may be a Vienna rectifier (3-phase vienna rectifier).

[0049] The first module (300) may include a plurality of first inductors (310), a first rectifier (320), and a first switching unit (330).

[0050] The first rectifier (320) can rectify the voltage applied from the second-first winding (221) of the transformer (200). The first rectifier (320) may include a plurality of diodes (D1, D2, D3, D4, D5, D6). Diodes (D1) and (D2) may be connected in series, diodes (D3) and (D4) may be connected in series, and diodes (D5) and (D6) may be connected in series to form a three-phase bridge. The (+) terminal of the first rectifier (320) may be connected to the first output terminal (OUP1), and the (-) terminal of the first rectifier (320) may be connected to the second output terminal (OUP2).

[0051] The first switching unit (330) can be switched by a switching controller (not shown) to form an output voltage.

[0052] The first switching unit (330) may include switching elements (S1, S2, S3, S4, S5, S6). Switching elements (S1) and (S2) may be connected in series and connected between diode (D1) and diode (D2). Switching elements (S3) and (S4) may be connected in series and connected between diode (D3) and diode (D4). Switching elements (S5) and (S6) may be connected in series and connected between diode (D5) and diode (D6). Switching elements (S1, S2, S3, S4, S5, S6) may be switched according to a Pulse Width Modulation (PWM) control signal of a switching controller to form a voltage at the output terminal of the output unit (500). In this case, the switching controller may convert the AC voltage into a DC voltage through the switching operation of the switching elements (S1) and (S2) in the case of phase a. In the case of phase b, the switching controller can convert the AC voltage into a DC voltage through the switching operation of the switching element (S3) and the switching element (S4). In the case of phase c, the switching controller can convert the AC voltage into a DC voltage according to the switching operation of the switching element (S5) and the switching element (S6). Here, the switching elements (S1, S2, S3, S4, S5, S6) may be power semiconductor devices for PWM control.

[0053] The first inductor (310) may include inductors (L1, L2, L3). One side of the inductor (L1) may be connected to phase a of the second-first winding (221) and the other side may be connected to a switching element (S1). One side of the inductor (L2) may be connected to phase b of the second-first winding (221) and the other side may be connected to a switching element (S3). One side of the inductor (L3) may be connected to phase c of the second-first winding (221) and the other side may be connected to a switching element (S5). Depending on the switching operation of the switching elements (S1, S2, S3, S4, S5, S6), the inductors (L1, L2, L3) may store or output the current of each phase.

[0054] The second module (400) can convert AC power input from the second-secondary winding (222) of the transformer (200) into DC power. The second module (400) may be a Vienna rectifier.

[0055] The second module (400) may include a plurality of second inductors (410), a second rectifier (420), and a second switching unit (430).

[0056] The second rectifier (420) can rectify the voltage applied from the secondary winding (222) of the transformer (200). The second rectifier (420) may include a plurality of diodes (D7, D8, D9, D10, D11, D12). Diodes (D7) and (D8) may be connected in series, diodes (D9) and (D10) may be connected in series, and diodes (D11) and (D12) may be connected in series to form a three-phase bridge. The (+) terminal of the second rectifier (420) may be connected to the first output terminal (OUP1), and the (-) terminal of the second rectifier (420) may be connected to the second output terminal (OUP2). The second switching unit (430) may be switched by a switching controller to form an output voltage.

[0057] The second switching unit (430) may include switching elements (S7, S8, S9, S10, S11, S12). Switching elements (S7) and switching elements (S8) may be connected in series and connected between diode (D7) and diode (D8). Switching elements (S9) and switching elements (S10) may be connected in series and connected to a node between diode (D9) and diode (D10). Switching elements (S11) and switching elements (S12) may be connected in series and connected to a node between diode (D11) and diode (D12). Switching elements (S7, S8, S9, S10, S11, S12) may be switched according to the PWM control signal of the switching controller to form a voltage at the output terminal of the output unit (500). In this case, the switching controller may convert the AC voltage into a DC voltage through the switching operation of switching elements (S7) and switching elements (S8) in the case of the -b phase. - In the case of phase -c, the AC voltage can be converted into a DC voltage through the switching operation of the switching element (S9) and the switching element (S10). - In the case of phase -a, the AC voltage can be converted into a DC voltage according to the switching operation of the switching element (S11) and the switching element (S12). Here, the switching elements (S7, S8, S9, S10, S11, S12) may be power semiconductor devices for PWM control.

[0058] The second inductor (410) may include inductors (L4, L5, L6). One side of the inductor (L1) may be connected to the -b phase of the second-secondary winding (222) and the other side may be connected to the switching element (S7). One side of the inductor (L2) may be connected to the -c phase of the second-secondary winding (222) and the other side may be connected to the switching element (S9). One side of the inductor (L3) may be connected to the -a phase of the second-secondary winding (222) and the other side may be connected to the switching element (S11). Depending on the switching operation of the switching elements (S7, S8, S9, S10, S11, S12), the inductors (L4, L5, L6) may store or output the current of each phase.

[0059] The output unit (500) can output voltages output from the first module (300) and the second module (400). Here, the (+) terminal of the first rectifier unit (320) and the (+) terminal of the second rectifier unit (420) can be connected to the first output terminal (OUP1). The (-) terminal of the first rectifier unit (320) and the (-) terminal of the second rectifier unit (420) can be connected to the second output terminal (OUP2). The first switching terminal (SWP1) of the first switching unit (330) and the second switching terminal (SWP2) of the second switching unit (430) can be connected to an intermediate point (m).

[0060] The output section (500) is the first DC link capacitor (C H ) and the second DC link capacitor (C L It may include ).

[0061] First DC link capacitor (C H ) and the second DC link capacitor (C L ) can be connected in series. The first DC link capacitor (C H ) is positioned between the first output terminal (OUP1) and the midpoint (m), and the second DC link capacitor (C L ) can be placed between the second output terminal (OUP2) and the midpoint (m).

[0062] First DC link capacitor (C H ) and the second DC link capacitor (C L ) is a first current (i) according to the switching operation of the first switching unit (330) and the second switching unit (430). CH ) or second current (i CL ) flows into the first DC link capacitor (C H ) and the second DC link capacitor (C L ) Voltage (v) on each CH ) and voltage (v CL ) can be formed.

[0063] Output voltage (V) of the output section (500) DC ) is the first DC link capacitor (C H) voltage (v CH ) and the second DC link capacitor (C L ) voltage (v CL It can be a voltage formed by ).

[0064] As described above, since the primary winding (210) of the transformer (200) is Y-connected, the secondary primary winding (221) is YY-connected, and the secondary secondary winding (222) is inverse Y-connected, the magnitude of the voltage output from the first module (300) and the second module (400) can be the same and the phase can be delayed by 60 degrees. As a result, the high-side voltage (v) of each of the first module (300) and the second module (400) CH ) cancel each other out so that the voltage at the midpoint (m) is smoothed, and the low-side voltage (v) of each of the first module (300) and the second module (400) CL ) can cancel each other out, so the voltage at the midpoint (m) can be smoothed.

[0065] In this way, the transformer and parallel multilevel converter according to one embodiment of the present invention wind two secondary windings that are independently separated from each other in different ways to cause phase delay, thereby canceling out the third harmonic of the midpoint voltage and smoothing the midpoint voltage.

[0066] In addition, the transformer and parallel multilevel converter according to one embodiment of the present invention can suppress voltage distortion, thereby reducing the size of the output filter of the multilevel converter and increasing the lifespan of the multilevel converter due to reduced heat generation.

[0067] Although the present invention has been described with reference to embodiments illustrated in the drawings, this is merely illustrative and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be determined by the claims below.

Claims

1. As a transformer for a parallel multilevel converter, Primary winding; It includes a secondary winding, The above secondary winding includes a 2-1st side winding and a 2-2nd side winding that are independently separated from each other and transmit power transmitted from the above primary winding to the first module and the second module, respectively. A transformer in which the above 2-1st winding and the above 2-2nd winding are connected in different ways so that the voltage outputs with the same magnitude and different phases.

2. In Paragraph 1, The above primary winding is Y-connected, the above 2-1st winding is Y-connected, and the above 2-2nd winding is inverse Y-connected, A transformer in which the above 2-secondary windings are connected such that each phase has a different polarity and sign from the above primary winding.

3. In Paragraph 2, A transformer in which the a, b, and c phases of the primary winding are connected to correspond, respectively, the -b, -c, and -a phases of the secondary winding.

4. A transformer comprising a primary winding and a secondary winding, wherein the secondary winding is independently separated from each other and includes a 2-1st winding and a 2-2nd winding that convert the voltage of a three-phase commercial power supply transmitted from the primary winding; A first module that converts AC power supplied from the above 2-1st side winding into DC power; A second module that converts AC power supplied from the above 2-secondary winding into DC power; and It includes an output unit that outputs DC power output from the first module and the second module, A parallel multilevel converter in which the above 2-1st side winding and the above 2-2nd side winding are connected in different ways so that the voltage outputs with the same magnitude and different phases.

5. In Paragraph 4, The above primary winding is Y-connected, the above 2-1st winding is Y-connected, and the above 2-2nd winding is inverse Y-connected, The above 2-secondary winding is a parallel type multilevel converter in which each phase is connected with a polarity and sign different from the above primary winding.

6. In Paragraph 5, A parallel multi-level converter in which the a, b, and c phases of the primary winding are connected to correspond, respectively, the -b, -c, and -a phases of the secondary winding.

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