WO2015083916A1 - Ac electric machine and driving apparatus including same - Google Patents

Abstract

The present invention relates to an AC electric machine having improved current harmonic characteristics for a second energy transfer unit, and to an AC electric machine driving apparatus including same. An AC electric machine according to an embodiment of the present invention comprises: a first energy transfer unit electrically coupled with the second energy transfer unit; the second energy transfer unit including at least two or more three-phase coil portions; a core electrically connecting the first energy transfer unit with at least two or more three-phase coil portions; and a connecting unit directly electrically connecting at least two or more three-phase coil portions, wherein by means of the connecting unit, the at least two or more three-phase coil portions equivalently constitute one delta connection coil portion.

Description

AC electromechanical machines and drives including them

The present invention relates to an alternating current electric machine and a driving device including the same, and more particularly, to an alternating current electric machine and a driving device including the same that improve the current harmonic characteristics of the winding connected to the power converter.

Recently, there are many applications for grid connection of renewable energy such as wind and solar, or grid connection of large-capacity battery energy storage devices for supporting the grid, and interest in this is rapidly increasing. In order to connect a new power source such as a renewable energy source or a fuel cell or a battery to an existing power system, the power source is usually connected to the system through a power converter. Since the power converter generally synthesizes a grid side voltage using pulse width modulation (PWM), harmonic components may be included in the grid current. Therefore, when a new power source such as wind, solar, fuel cell or battery is connected to the existing system through the power converter, IEEE Std. 1547 or IEEE Std. International standards such as 519 or harmonic standards set by national regulatory bodies must be met.

As the PWM frequency increases, the output harmonic characteristics of the power converter can be easily improved, while the switching losses increase, which reduces the overall conversion efficiency. Furthermore, too high PWM frequencies may cause electromagnetic interference (EMI) problems. In the case of using a power converter having a low PWM frequency, the weight and volume of the device are relatively increased, and there is a problem in that an additional harmonic suppression filter must be installed to satisfy the harmonic standards set by the relevant regulations.

In recent years, as the cost of semiconductor devices has decreased, it has become easier to operate a plurality of power converters in parallel in order to connect a large power source to the grid. A method of reducing harmonic pulsations has been proposed. This method has the advantage of minimizing the use of additional filters and can be easily implemented using a transformer as shown in FIG. 1.

However, even in this case, the harmonics of the transformer primary current can be suppressed by appropriately controlling the PWMs of the paralleled power converters, but the harmonic current pulsation still remains largely in the current flowing through the secondary transformer of the transformer. Increasing the root mean square current increases the current rating of the power converter and reduces the power conversion efficiency.

This problem may also occur in the case of an electric motor or a generator connected to a power converter. The driving principle is very similar to a transformer in that an electric motor or a generator transfers energy through magnetic coupling. For example, in the case of an electric motor, the flow of alternating current through the stator windings creates a magnetic flux that rotates in space, which causes the rotor to generate torque that causes rotation. At this time, as the power converter used for driving the motor uses PWM, the current flowing through the stator windings includes harmonic components of the switching frequency band in addition to the frequency components that generate torque required for rotation. Harmonic components of the motor drive current may also cause the problem of increasing the RMS current as mentioned above, increasing the current rating of the power converter and reducing the power conversion efficiency.

In addition, the power converter for driving an AC electromechanical machine has a limit in reducing the current pulsation by increasing the switching frequency when the capacity of the target AC electromechanical device increases, thus reducing the current pulsation flowing to the stator while maintaining a low switching frequency. There is a need.

According to an aspect of the present invention, by applying a new connection method with the power converter to the winding of the second energy transfer unit including a plurality of three-phase winding of the AC electric machine, the harmonic characteristics of the current of the second energy transfer unit is improved. It is possible to provide an alternating current electromechanical machine and an alternating current electromechanical driving device including the same.

According to another aspect of the present invention, it is possible to provide an alternating current electromechanical apparatus and an alternating current electromechanical driving apparatus including the same.

According to another aspect of the present invention, it is possible to provide an alternating current electromechanical device and an alternating current electromechanical driving device including the same, which are composed of elements having a lower rated current, thereby reducing manufacturing costs.

AC electric machine according to the embodiments of the present invention, the first energy transfer unit magnetically coupled to the second energy transfer unit; A second energy transfer comprising at least two three-phase windings; A core magnetically connecting the first energy transfer unit and the at least two three-phase windings; And a connection part for directly connecting the at least two three-phase winding parts, wherein the windings included in the at least two three-phase winding parts are connected to one delta (Δ) wired winding part. Configure equivalently.

In an embodiment, the alternating current electrical machine is a transformer, the first energy transfer portion is a transformer primary stage, the second energy transfer unit is a transformer secondary stage, and the core is a transformer core.

In an embodiment, the alternating current electrical machine is an electric motor or a generator, the first energy transfer portion is a rotor, the second energy transfer portion is a stator, and the core is a stator core.

In an embodiment, line voltages or line voltages of at least two or more three-phase power sources are connected to nodes between the windings of the delta-connected winding.

In an embodiment, the nodes and the line voltages or line voltages are connected one to one, respectively.

In an embodiment, the line voltages or the line voltages of the at least two three-phase power sources form a delta connection or a Y connection for each of the corresponding three-phase power sources.

In an embodiment, the at least two three-phase power supplies are a combination of three three-phase pulse width modulation (PWM) power supplies or three single-phase PWM power supplies.

In an embodiment, three phase power input terminals of at least two or more three phase loads are connected to nodes between the windings of the delta connected winding.

In an embodiment, the nodes and the three-phase power input terminals are each connected one-to-one.

An AC electromechanical driving device according to embodiments of the present invention includes: a first energy transfer unit magnetically coupled to a second energy transfer unit; A second energy transfer comprising at least two three-phase windings; A core magnetically connecting the first energy transfer unit and the at least two three-phase windings; And a connection portion for directly connecting the at least two three-phase winding portions, wherein the at least two three-phase winding portions are equivalently constituted by one Delta (Δ) wired winding portion. Alternating current electrical machinery; And at least two or more three phase power sources electrically connected directly to at least two or more three phase windings of the second energy transfer unit.

In an embodiment, the alternating current electrical machine is a transformer, the first energy transfer portion is a transformer primary stage, the second energy transfer unit is a transformer secondary stage, and the core is a transformer core.

In an embodiment, the alternating current electrical machine is an electric motor or a generator, the first energy transfer portion is a rotor, the second energy transfer portion is a stator, and the core is a stator core.

In an embodiment, the at least two three-phase power supplies are a combination of three three-phase pulse width modulation (PWM) power supplies or three single-phase PWM power supplies.

In an embodiment, line voltages or line voltages of the at least two three-phase power sources are connected to nodes between the windings of the delta-connected winding.

In an embodiment, the nodes and the line voltages or line voltages are connected one to one, respectively.

An AC electromechanical driving device according to embodiments of the present invention includes: a first energy transfer unit magnetically coupled to a second energy transfer unit; A second energy transfer comprising at least two three-phase windings; A core magnetically connecting the first energy transfer unit and the at least two three-phase windings; And a connection portion for directly connecting the at least two three-phase winding portions, wherein the at least two three-phase winding portions are equivalently constituted by one Delta (Δ) wired winding portion. Alternating current electrical machinery; And at least two or more three phase loads electrically connected to at least two or more three phase windings of the second energy transfer unit.

In an embodiment, the alternating current electrical machine is a transformer, the first energy transfer portion is a transformer primary stage, the second energy transfer unit is a transformer secondary stage, and the core is a transformer core.

In an embodiment, the alternating current electrical machine is an electric motor or a generator, the first energy transfer portion is a rotor, the second energy transfer portion is a stator, and the core is a stator core.

In an embodiment, three phase power input terminals of at least two or more three phase loads are connected to nodes between the windings of the delta connected winding.

According to embodiments of the present invention, the output harmonic characteristics of the AC electric machine and the power converter are improved. In addition, since the effective current of the second energy transfer unit including a plurality of three-phase windings of the AC electric machine is reduced, the overall power conversion efficiency is improved, and the AC electric machine and the AC electric machine driving device with lower rated current elements. It can be configured to reduce the production cost.

1 is a circuit diagram showing a conventional transformer and a driving device.

2A is a block diagram illustrating an AC electric machine and a driving device according to an embodiment of the present invention.

2B is a circuit diagram illustrating a transformer and a driving device according to an embodiment of the present invention.

FIG. 2C is a circuit diagram illustrating a cross-sectional view of an AC electric machine and an output voltage of an AC electric machine and a power converter, according to an exemplary embodiment.

3 is a circuit diagram specifically illustrating the three-phase PWM power supply of FIG. 2A as an example.

4 is a circuit diagram schematically illustrating the connection of the secondary winding of a transformer in the form of a delta connection according to an embodiment of the present invention.

FIG. 5 is a circuit diagram illustrating a secondary winding connection of a transformer having a different phase order according to an embodiment of the present invention.

6 is a circuit diagram illustrating a secondary winding connection of a transformer having three or more three-phase windings according to an exemplary embodiment of the present invention.

7 and 8 are timing diagrams showing simulation results of the AC electromechanical driving apparatus according to the prior art and the AC electromechanical driving apparatus according to the present invention, respectively, to show the advantageous effects of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The following detailed description of the invention refers to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present disclosure. It is to be understood that the various embodiments of the invention are different, but need not be mutually exclusive. For example, specific shapes, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention with respect to one embodiment.

In addition, it is to be understood that the location or arrangement of individual components within each disclosed embodiment may be variously changed without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined in the appended claims in principle, and encompasses what is described in the claims and the equivalent embodiments thereof. When like reference numerals are used in the drawings, like reference numerals refer to the same or similar functions for the various embodiments.

Conventional AC electric machines and drive devices including the same have the problems described above, and AC electric machines generally include a transformer, an electric motor, and a generator. The transformer controls the magnetic flux in the transformer windings to which the power converter is connected to exchange energy with the other windings of the transformer through the transformer core. Alternating current electrical machines with stators and rotors, such as motors and generators, have stators connected to the power converter. The magnetic flux changes in the windings to exchange energy with the rotor through the stator core and voids. Since the problems of the prior art and the main principles of the present invention described below are equally applicable to the secondary winding of a transformer or the stator winding and the power converter of an alternating current electric machine, the following description will be given with reference to FIG. The prior art will be described.

1 is a circuit diagram illustrating a conventional transformer and a driving device including the same. Referring to FIG. 1, the driving device 10 includes a winding unit 15 of a transformer primary stage, a winding unit 11 and 13 of a secondary transformer stage, a transformer core 17, an AC load 16, and a PWM power supply 12. , 14). Among them, the winding unit 15 of the transformer primary stage, the winding units 11 and 13 of the transformer secondary stage, and the transformer core 17 may constitute one transformer.

In power converters having relatively low PWM frequencies (e.g., PWM power supplies 12, 14), at least two power supplies in parallel with the transformer secondary, as shown in Figure 1, to reduce the use of harmonic suppression filters. Can be operated. Here, the power supply means a circuit module composed of one PWM power supply and a winding connected thereto. For example, the first PWM power source 12 and the first winding unit 11, and the second PWM power source 14 and the second winding unit 13 each constitute one power supply unit. Here, each of the PWM power supplies 12 and 14 is a three-phase PWM power supply, and each of the winding parts 11, 13, and 15 of the transformer first and second stages is a three-phase winding.

The driving device 10 may cause the phases of the output pulsations provided to the windings 11 and 13 to be different from each other by different carrier waves of the PWM power supplies 12 and 14. The harmonic pulsations are synthesized through the magnetic circuits of the transformers 11, 13, 17, and 15, and appear in the first stage of the transformer in a state in which harmonic components of each other are cancelled. As a result, only much lower harmonic pulsations appear in the transformer primary. As such, by applying a plurality of power supply units operated in parallel, the harmonic criterion in the first stage of the transformer can be more easily satisfied because harmonic pulsations different in phase from each other are magnetically synthesized through the transformer.

However, even in this case, since the effects of canceling each other with respect to the currents of the transformer secondary winding windings 11 and 13 cannot be expected, the harmonic pulsation caused by the low frequency PWM still remains in the secondary transformer. The pulsation of the secondary stage of the transformer increases the root mean square (RMS) current to reduce the power conversion efficiency, and switching elements of the PWM power supplies 12 and 14 are devices having a large rated current compared to the fundamental wave current. It causes a problem that must be configured.

In general, in a plurality of power supply units operated in parallel, the windings 11 and 13 of the secondary stage of the transformer included in each of the plurality of power supply units are configured to have no direct electrical connection with each other. In contrast, the present invention provides a method for creating a direct electrical connection between the transformer secondary windings 11, 13 to reduce the current pulsation flowing through the windings 11, 13 and improve the power conversion efficiency of the power converter. present.

2A is a circuit diagram illustrating an AC electric machine and an AC electric machine driving apparatus including the same according to an exemplary embodiment of the present invention. Referring to FIG. 2A, the driving device 100 includes a first energy transfer unit 160, a second energy transfer unit including windings 110 and 130, a core 180, and a PWM power supply 120 and 140. It may include. In addition, the driving device 100 may include an AC load (or a three-phase load) 170. Among these, the first energy transfer unit 160, the second energy transfer unit including the windings 110 and 130, and the core 180 may constitute one AC electric machine. The second energy transfer unit including the first energy transfer unit 160 and the windings 110 and 130 magnetically couples to each other to exchange energy due to the induced magnetic phenomenon.

Meanwhile, in FIG. 2A, the windings 110 and 130 of the second energy transfer part of the AC electromechanical part are illustrated as being connected to the PWM power supply 120 and 140, in which case the energy transfer direction is the first in the second energy transfer part. Will be directed to the energy transfer unit 160, but the scope of the present invention is not limited thereto. For example, the windings 110 and 130 of the second energy transfer unit of the AC electric machine may be connected to a three-phase load (eg, a battery to be charged) instead of the PWM power sources 120 and 140. In this case, three-phase power input terminals of three-phase loads will be connected to nodes between the windings of the windings 110, 130 of the second electromechanical second energy transfer. And, the energy transfer direction will be directed from the first energy transfer unit 160 to the second energy transfer unit.

In an embodiment, the AC electric machine is a three-phase connection relaying the connection of the windings 110 and 130 of the second energy transfer unit with external three-phase power sources (here, PWM power sources 120 and 140) or three-phase loads. Terminals may be further included.

In FIG. 2A, the PWM power supplies 120, 140 and the windings 110, 130 are three phase power and three phase windings, respectively. The windings 110 and 130 of the second energy transfer unit of the AC electric machine are connected by the connection unit 150 in an equivalent delta shape. Each line voltage of the PWM power supplies 120 and 140 is applied to a node between the windings α ₁ , β ₁ , γ ₁ , α ₂ , β ₂ , γ ₂ connected in a delta form.

Since the alternating current electrical machine composed of the first energy transfer unit 160, the windings 110 and 130, and the core 180 of the driving device 100 is a three-phase alternating current electrical machine, ideally, the windings α, β, and γ Are equal in magnitude and have a phase difference of 120 degrees from each other.

In the present invention, the driving device 100 is to maintain the harmonic characteristics of the first energy transfer unit 160 of the alternating current electric machine, while reducing the current harmonic pulsation of the second energy transfer unit of the alternating current electric machine. It further includes a connection portion 150 for directly connecting the windings (110, 130) of the energy transfer.

The connection part 150 connects the nodes of the first winding part 110 and the nodes of the second winding part 130 so that the first winding part 110 and the second winding part 130 are equivalently delta-connected. It is configured to form one winding of the form.

The present invention is a plurality of three-phase windings (α ₁ , β ₁ , γ ₁ , α ₂ through the connection unit 150, while operating the DC power supply in parallel through the power converter to the second energy transfer unit of the AC electric machine) , β ₂ , γ ₂ ) are electrically connected to form one delta winding. When the two windings 110 and 130 illustrated in FIG. 2A are defined as a pair of windings, several pairs of windings may be magnetically connected to a core of one AC electric machine.

Specific principles and additional embodiments for connecting the windings 110 and 130 of the driving device 100 will be described in more detail later, but as in the embodiment of the present invention, a direct connection between the windings 110 and 130 is added. The harmonic pulsations in the second energy transfer section of the AC electric machine are greatly reduced. As such, the driving device 100 which reduces the harmonic pulsation of the second energy transfer part of the AC electric machine has the following advantageous effects.

In general, the switching elements of the power converters 120 and 140 are not ideal, so that some voltage drop occurs during the current conduction, and the conduction loss is multiplied by the product of the switch voltage drop [V] and the conduction current [A]. W] occurs. Furthermore, at the instant of switching, voltage and current increase / decrease with a finite slope, resulting in switching losses proportional to the product of current and voltage. Therefore, in order to reduce such conduction loss and switching loss, it is advantageous that the harmonic pulsating current other than the fundamental wave component not contributing to the power transfer is as small as possible. Since the current can be reduced, the power conversion efficiency of the driving device 100 is improved.

In addition, since the filter for removing the pulsating current can be eliminated or minimized, the manufacturing cost, volume, and weight of the driving device 100 can be reduced. In addition, if the efficiency of the driving device 100 is improved, the operation loss of the heat dissipating device for maintaining the temperature of the switching element can be reduced, and the heat dissipation design is advantageous, thereby adding the overall volume and weight of the driving device 100. Can be further reduced.

2B is a circuit diagram illustrating an AC electric machine and a driving device including the same according to an exemplary embodiment of the present invention. Referring to FIG. 2B, the AC electromechanical apparatus of the present invention may be a transformer including a transformer primary stage 360, a transformer secondary stage including windings 310 and 330, and a transformer core 380. In addition, the AC electromechanical driving apparatus 300 may include a winding 360 of the first stage of the transformer, windings 310 and 330 of the second stage of the transformer, a transformer core 380, and a PWM power source 320 and 340. It may also include an AC load (or a three-phase load) 370.

In FIG. 2B, the winding unit 360 of the first stage of the transformer is illustrated in the form of a Y connection, but the winding unit 360 may be configured in another connection form. For example, the winding 360 of the first stage of the transformer may be configured in a delta (Δ) connection form.

In FIG. 2B, the PWM power sources 320, 340 and the windings 310, 330, 360 are three phase power and three phase windings, respectively. The windings 310 and 330 of the second stage of the transformer are connected by the connection unit 350 in an equivalent delta shape. Each line voltage of the PWM power sources 320 and 340 is applied to a node between the windings α ₁ , β ₁ , γ ₁ , α ₂ , β ₂ , γ ₂ connected in the delta form.

Since the transformer of the drive device 300 is a three-phase transformer, the windings of the same phase (eg, α ₁ and α ₂ ) are transformer primary 360 regardless of the winding number (subscripted 1 or 2). Corresponds to the same winding (eg, α _p ).

In the present invention, the drive unit 300 is a connection portion for directly connecting the transformer secondary winding windings 310 and 330 to reduce the current harmonic pulsation of the transformer secondary stage while maintaining the harmonic characteristics of the transformer primary stage 360. And further includes 350.

The connection part 350 connects the nodes of the first winding part 310 and the nodes of the second winding part 330 so that the first winding part 310 and the second winding part 330 are equivalently delta-connected. It is configured to form one winding of the form.

2C is a cross-sectional view of an AC electric machine and a driving apparatus according to an embodiment of the present invention, which includes a stator and a rotor, and a connection relationship with an output voltage of the power converter. Here, the AC electric machine may be an electric motor or a generator. Referring to FIG. 2C, an alternating current electric machine includes a rotor 460, windings composed of windings α ₁ , β ₁ , γ ₁ , α ₂ , β ₂ , γ ₂ , and a stator core 480. It may include a stator. In addition, the AC electromechanical driving device 400 may include the AC electromechanical and PWM power sources 420 and 440 of the present embodiment, and the PWM power may act as a load when operating as a generator.

In FIG. 2C, a typical three-phase electric motor or a generator transmits and receives energy through three electrical connections from a driving device. The AC electromechanical driving device 400 of the present invention internally stir-winds a plurality of windings α _1. , β ₁ , γ ₁ , α ₂ , β ₂ , and γ ₂ ) further includes a connection unit 450 for allowing each of the windings to receive energy directly from the plurality of three-phase PWM power sources. The connection unit 450 connects the first windings α ₁ , β ₁ , γ ₁ and the second windings α ₂ , β ₂ , γ ₂ , and the windings α ₁ , β ₁ , γ ₁ , α ₂ , β ₂ , γ ₂ ) are configured to equivalently form one winding in the form of a delta (Δ) connection. Each line voltage of the PWM power supplies 420 and 440 is applied to a node between the windings α ₁ , β ₁ , γ ₁ , α ₂ , β ₂ , and γ ₂ connected in a delta form.

When the direction of energy transfer is from the stator of the alternating current electric machine to the rotor, the currents (or voltages) applied to the windings (a ₁ , β ₁ , γ ₁ , α ₂ , β ₂ , γ ₂ ) of the stator are Are synthesized to transfer energy to the rotor 460. Conversely, when the direction of energy transfer is directed from the rotor to the stator, the energy of the rotor is current (or voltage) in the windings of the stator (α ₁ , β ₁ , γ ₁ , α ₂ , β ₂ , γ ₂ ). It is divided into two parts. Even in this case, by electrically connecting the windings α ₁ , β ₁ , γ ₁ , α ₂ , β ₂ , γ _{2 of the} stator 450, the windings α ₁ , β ₁ , γ of the stator ₁ , α ₂ , β ₂ , γ ₂ ) is not changed that the harmonic pulsation is reduced.

The cross-sectional view of the AC electric machine shown in FIG. 2C is a structure composed of six slots, but the scope of the present invention is not limited thereto. The shape or number of slots and the way in which the windings are wound can be varied, and the number of poles of the rotor can be adjusted accordingly.

In general, a three-phase alternating current electric machine is such that the stator winding is powered from the outside through a three-phase winding (eg, an electric motor) or sends generated power to the outside (eg, a generator). In particular, in the case of a large AC electric machine, a plurality of three-phase windings improves the starting characteristics or increases the output through a serial / parallel connection. In an embodiment of the present invention, two three-phase windings or 2n (n = natural number) The three 3-phase windings transmit power to the outside. At this time, if the carrier phase of each power converter (for example, PWM power supply) that applies voltage to the AC electric machine is adjusted differently, pulsation reduction effect can be obtained in the stator winding current and the magnetic flux linking to the rotor. have. It may seem disadvantageous to use a plurality of power converters to drive one AC electric machine, but in the case of driving a large AC machine, parallel operation of the power converters is difficult due to the capacity limitation of the switching element. Inevitably, the cost burden does not increase.

3 is a circuit diagram specifically illustrating an example of the three-phase PWM power supply of FIGS. 1 and 2A to 2C as an example of a power converter. Referring to FIG. 3, the three-phase PWM power supply 120 includes a DC power supply 121, a switching unit 122, and an output terminal 123. Although FIG. 3 shows a two-level power converter, a power converter having a higher level output may be used, and unlike FIG. 3 in which a three-phase power source is generated from one DC power source, each phase output is a separate DC power source. It may also be generated from.

The DC power supply 121 operates as a source of power. The DC power supply 121 includes various types of power supplies. For example, the DC power supply 121 may include a battery, a solar panel, or a power supply using a rectifier circuit for converting AC into DC. The DC power supply 121 provides power to the output terminal 123 through the switching unit 122.

The switching unit 122 is inserted between the DC power supply 121 and the output terminal 123 to convert the DC power provided by the DC power supply 121 into PWM power through switching. The switching unit 122 includes a plurality of power switches therein, and controls the opening and closing of each switch to convert DC power into three-phase PWM power. Since a specific control method of the switching unit 122 for converting DC power into three-phase PWM power is well known in the art, a description thereof will be omitted here.

The three-phase PWM power converted by the switching unit 122 is provided to the three-phase windings 110 and 130 (see FIG. 2A) through the output terminal 123.

The output terminal 123 is a terminal for outputting the provided three-phase PWM power to the three- phase windings 110 and 130. The output terminal 123 may be configured as a hardware terminal including a connector, or may be simply configured as a simple electrical connection.

Hereinafter, the windings of the AC electric machine according to the exemplary embodiment of the present invention will be described with reference to FIG. 4 as an example of a transformer in the form of a delta connection. The alternating current electric machine including the stator and the rotor are similarly applied to the secondary and primary stages of the transformer, respectively. 4 is a circuit diagram schematically illustrating the connection of the secondary winding of the transformer shown in FIG. 2B in the form of a delta connection. Referring to FIG. 4, in order to more clearly understand the winding connection of FIG. 2B, a circuit diagram showing the windings of FIG. 2B and the line voltages applied to them in the form of a delta connection is shown.

The result of connecting the secondary windings 310, 330 (see FIG. 2B) of the transformer of FIG. 2B directly through the connection 350 (see FIG. 2B) results in a delta connection of the windings and the line voltages shown in FIG. Equivalent to the circuit Here, the line voltages V _ab , V _bc , V _ca , V _rs , V _st , and V _tr refer to voltages between the output terminals of the PWM power supplies 320, 340, and FIG. 2B, respectively.

For example, the line voltage V _ab refers to the voltage between the output terminals a and b of the first PWM power supply 320, and the line voltage V _bc refers to the output of the first PWM power supply 320. The voltage between the terminals b and c, and the line voltage V _ca , refers to the voltage between the output terminals c and a of the first PWM power supply 320. Similarly, the line voltage V _rs refers to the voltage between the output terminals r and s of the second PWM power supply 340, and the line voltage V _st is the output terminal of the second PWM power supply 340. The line voltage (V _tr ) means the voltage between the output terminals (t, r) of the second PWM power supply 340.

Referring to FIG. 4, the line voltage provided by the first PWM power supply 320 and the line voltage provided by the second PWM power supply 340 simultaneously act on each of the windings. That is, due to the circuit structure in which the two PWM power sources 320 and 340 are combined in a delta form, each of the windings α ₁ , β ₁ , γ ₁ , α ₂ , β ₂ , and γ ₂ may have different PWM. Line voltages derived from the power sources 320 and 340 are superposed and applied. Therefore, if the output carrier phase of the PWM power supplies 320 and 340 are different from each other, the harmonic pulsation of each winding is canceled due to the superposition effect of the line voltages in the second stage of the transformer.

When the direction of power transfer is directed from the secondary stage of the transformer to the primary stage of the transformer, the currents (or voltages) applied to the first and second windings 310 and 330 are combined to form the winding 360 of the primary stage of the transformer. , See FIG. 2B). Conversely, when the direction of power transfer is from the first stage of the transformer to the second stage of the transformer, the current (or voltage) applied to the winding 360 of the transformer primary stage is the first and second windings of the secondary transformer stage. It is divided into (310, 330). Even in this case, the change in harmonic pulsation of the first and second windings 310 and 330 is reduced by electrically connecting the first and second windings 310 and 330. none.

Meanwhile, as described above, α, β, and γ mean three phases having a phase difference of 120 degrees from each other, and phases corresponding to each other in the first winding part 310 and the second winding part 330 (for example, For example, α ₁ and α ₂ ) are the same size and phase with each other. Therefore, there is no superiority or sequence difference between the first winding 310 and the second winding 330, and the two are distinguished only because the PWM power or load to be connected is different. For example, even if α ₁ and α ₂ are arranged in the state where they are mutually inverted in FIG. 4, there is no difference in achieving the intended effect of the present invention, and this is true even in windings corresponding to β phase or γ phase. same.

The part of the windings α ₁ , β ₁ , γ ₁ , α ₂ , β ₂ , γ ₂ corresponds to the transformer secondary when the positive voltage is applied to the node pointed at the transformer primary. This means that a positive voltage is applied to the node where the dot on which the dot is marked. The dotted node is also a relative meaning, and may be configured such that each of the windings has a polarity opposite to that shown in FIG. 4 according to the winding direction of the transformer secondary winding.

Meanwhile, although the line voltages are shown as delta power sources, the scope of the present invention is not limited thereto. For example, delta power supplies may be equivalently converted to a Y power source. In this case, however, the connected line voltages will be replaced by the line voltages of the output terminals. The three-phase power source may be generated from one power converter, but may be generated using a plurality of power converters.

According to the configuration described above, since the line voltages of the PWM power supplies having different phases are applied to each of the windings, harmonic pulsations of the respective windings are reduced.

FIG. 5 is a circuit diagram illustrating connection of secondary windings of a transformer having a different phase order according to an embodiment of the present invention. Referring to FIG. 5, windings and line voltages are arranged to have a phase order in the opposite direction to FIG. 4.

In FIG. 4, the phase change of the line voltages of the first PWM power source 320 (see FIG. 2B) and the second PWM power source 340 (see FIG. 2B) is shown in the counterclockwise direction. In FIG. 5, the first PWM power source 320 is shown in FIG. 5. ) And the phase change of the line voltages of the second PWM power supply 340 appear in a clockwise direction. This can be implemented simply by reversing the phase order of the output currents (or voltages) of the PWM power supplies 320, 340.

Even when the phase order is changed in this way, the voltages between the wires of the PWM power sources 320 and 340 which are out of phase with each other are applied to each of the windings α ₁ , β ₁ , γ ₁ , α ₂ , β ₂ , and γ ₂ . Since there is no difference, the effect of reducing the harmonic pulsation of each of the windings is also fully exhibited.

Meanwhile, as a result of directly connecting the respective windings α ₁ , β ₁ , γ ₁ , α ₂ , β ₂ , and γ ₂ of the stator of the AC electric machine of FIG. 2C through the connection part 450, The circuit is equivalent to the delta connection of the windings and the line voltages shown. That is, referring to FIG. 5, the line voltage provided by the first PWM power supply 420 and the line voltage provided by the second PWM power supply 440 simultaneously act on the respective windings of the AC electric machine of FIG. 2C. That is, due to the circuit structure in which the two PWM power sources 420 and 440 are combined in a delta form, each of the windings α ₁ , β ₁ , γ ₁ , α ₂ , β ₂ , and γ ₂ may have different PWM. Line voltages derived from the power sources 420 and 440 are applied in overlap. Therefore, if the output carrier phase of the PWM power supplies 420 and 440 are different from each other, the harmonic pulsation of each winding is canceled due to the superposition effect of the line voltages in the stator of the AC electric machine.

In the present invention, the manner of connecting the windings and the line voltages is not limited to that shown in FIGS. 4 and 5. The present invention connects a plurality of windings (for example, windings 310 and 330 of FIG. 2B) that are separated from each other through a connection portion (for example, connection portion 350 of FIG. 2B) to form a delta connection. One delta winding may be generated, and the line voltage or line voltage of the plurality of three-phase power sources may be connected to each node between the respective windings included in the delta winding.

In this case, one three-phase power supply (for example, 320) may apply all of the line voltage or line voltages to one winding part (eg, 310), or two or more winding parts (eg, 310). , 330 may be applied.

6 is a circuit diagram illustrating an AC electric machine having three or more three-phase windings in a second energy transfer unit according to an embodiment of the present disclosure. In one example, the AC electric machine may be a transformer. Referring to FIG. 6, a total of 12 windings 211, 212, 213, 221, 222, 223, 231, 232, 233, 241, 242, and 243 of four three-phase windings are connected in a delta connection form.

Windings with similar reference numerals constitute the same winding. For example, the windings 211, 212, 213 make up the first winding, the windings 221, 222, 223 make up the second winding, and the windings 231, 232, 233 make up the third winding. The winding comprises a winding and the windings 241, 242, 243 constitute a fourth winding.

Although the delta winding unit 200 illustrated in FIG. 6 is configured such that windings constituting the same winding unit are positioned adjacent to each other, this is exemplary and the present invention is not limited thereto. For example, the winding 211 constituting the first winding part may be disposed between the winding 222 constituting the second winding part and the winding 232 constituting the third winding part.

The dotted lines in FIG. 6 represent four three-phase power supplies connected in delta. The line voltage or line voltages of the four three-phase power sources are respectively between the respective windings 211, 212, 213, 221, 222, 223, 231, 232, 233, 241, 242, and 243 of the delta winding 200. Connected to the node. Meanwhile, although the four three-phase power sources are connected to the delta winding unit 200 in a circular form having regularity with each other, this is exemplary and the present invention is not limited thereto. The four three-phase power supplies may be connected to the delta winding 200 in a symmetrical or non-cyclic manner, with only three phase power sources having different carrier phases in at least one winding of the delta winding 200. It is sufficient if they are configured to intersect (i.e., to connect the line voltage or line voltage of a three-phase power source with different carrier phases across both ends of the winding).

On the other hand, as described above, the delta-connected three-phase power source may be replaced by the power supply of the Y connection type.

According to the above configuration, the present invention can be extended to the AC electric machine having three or more three-phase windings in the second energy transfer unit. Therefore, even in the case of having three or more three-phase windings in the second energy transfer portion of the alternating current electric machine, harmonic pulsations can be reduced and thus power conversion efficiency can be improved.

7 and 8 are timing diagrams showing simulation results of the driving apparatus according to the prior art and the driving apparatus according to the embodiment of the present invention, respectively, to show the advantageous effects of the present invention. In FIG. 7 and FIG. 8, the alternating current electric machine is a transformer and four three-phase windings are included in the second stage.

FIG. 7 is a timing diagram illustrating currents of a transformer primary stage and a transformer secondary stage in the driving apparatus according to the related art.

The timing diagram 710 shows the system current Iap of the first stage of the transformer. Since the three-phase powers of different phases of the second stage of the transformer are synthesized and appear in the first stage of the transformer, it can be seen that the harmonic content is greatly reduced. .

The timing diagram 720 shows a phase currents Iai1, Iai2, Iai3, and Iai4 of the transformer secondary stage. Since the transformer secondary stage includes four three-phase windings, there are four three-phase power supplies correspondingly. The a phase currents Iai1, Iai2, Iai3, and Iai4 mean a phase currents of the three phase power sources. In the timing diagram 720, the harmonic component appears large, unlike in the case of transformer primary breaking. This large harmonic component increases the RMS current of the power converter, lowers power conversion efficiency, and increases grid loss and switching loss.

8 is a timing diagram illustrating currents in a transformer primary stage and a transformer secondary stage in a driving apparatus according to an embodiment of the present invention.

The timing diagram 810 shows the system current Iap of the transformer primary stage, and shows the same result as in FIG. 7. Similarly, since three-phase powers having different carrier phases in the second stage of the transformer are synthesized and appear in the first stage of the transformer, it can be seen that the harmonic components are greatly reduced in the first stage of the transformer.

The timing diagram 820 shows a phase currents Iai1, Iai2, Iai3, and Iai4 of the transformer secondary stage. Since the transformer secondary stage includes four three-phase windings, there are four three-phase power supplies correspondingly. The a phase currents Iai1, Iai2, Iai3, and Iai4 mean a phase currents of the three phase power sources.

In embodiments of the present invention, line voltages or line voltages of different three-phase power sources are applied to both ends of each of the windings. Therefore, each of the windings overlaps the line voltage or the line voltage of different three-phase power sources. Therefore, when the carrier phase of the three-phase power supplies are different from each other, the harmonic components in the respective windings cancel each other out.

Looking at the timing diagram 820, unlike FIG. 7, the harmonic content of the second stage of the transformer is significantly reduced. Therefore, the AC electromechanical driving apparatus according to the embodiment of the present invention suppresses the harmonics of the second stage of the transformer, so that the power conversion efficiency is improved, and the conduction loss and the switching loss can be confirmed.

Meanwhile, the present invention may contribute to improving the performance of a transformer and a driving device including the same, and may be widely used anywhere in the field of power conversion in which a power converter may be used in addition to the field of battery energy storage.

In addition, in the illustrated embodiments, it has been described that the three-phase power source connected to the transformer second stage is a three-phase PWM power source, but the scope of the present invention is not limited thereto. For example, in another embodiment of the present invention, power sources in which three single-phase PWM power supplies are combined may be used instead of the three-phase PWM power supply.

In the detailed description of the present specification, a specific embodiment has been described. However, each embodiment may be modified in various forms without departing from the scope of the present specification.

In addition, although specific terms are used herein, they are used only for the purpose of describing the present invention and are not used to limit the scope of the present specification as defined in the meaning or claims. Therefore, the scope of the present specification should not be limited to the above-described embodiments, but should be defined by the following claims and their equivalents.

Claims (19)

1. A first energy transfer unit magnetically coupled with the second energy transfer unit;

   The second energy transfer unit comprising at least two three-phase windings;

   A core magnetically connecting said first energy transfer portion and said at least two three-phase windings; And

   A connection for directly connecting the at least two three-phase windings electrically;

   By means of said connection, said at least two three-phase windings equivalently constitute one delta-connected winding.
2. The method of claim 1,

   The AC electric machine is a transformer,

   The first energy transfer unit is a transformer primary stage, the second energy transfer unit is a transformer secondary stage,

   The core is a transformer core.
3. The method of claim 1,

   The AC electric machine is an electric motor or a generator,

   The first energy transfer part is a rotor, the second energy transfer part is a stator,

   The core is a stator core.
4. The method according to any one of claims 1 to 3,

   And line voltages or line voltages of at least two or more three-phase power supplies are connected to nodes between the windings of the delta-connected winding.
5. The method of claim 4, wherein

   And the nodes and the line voltages or line voltages are each connected one-to-one.
6. The method of claim 4, wherein

   Wherein the line voltages or line voltages of the at least two three-phase power supplies form a delta connection or a Y connection for each corresponding three-phase power source.
7. The method of claim 4, wherein

   Wherein said at least two three-phase power supplies are power supplies in combination of three-phase pulse width modulation (PWM) power supplies or three single-phase PWM power supplies.
8. The method according to any one of claims 1 to 3,

   And three-phase power input terminals of at least two three-phase loads are connected to nodes between the windings of the delta-connected winding.
9. The method of claim 8,

   And the nodes and the three-phase power input terminals are each connected one-to-one.
10. A first energy transfer unit magnetically coupled with the second energy transfer unit;

    The second energy transfer unit comprising at least two three-phase windings;

    A core magnetically connecting said first energy transfer portion and said at least two three-phase windings; And

    A connection for directly connecting the at least two three-phase windings electrically;

    By said connecting portion, said at least two three-phase windings equivalently constitute one delta-connected winding; And

    And at least two or more three phase power sources electrically connected directly to at least two or more three phase windings of the second energy transfer unit.
11. The method of claim 10,

    The AC electric machine is a transformer,

    The first energy transfer unit is a transformer primary stage, the second energy transfer unit is a transformer secondary stage,

    And the core is a transformer core.
12. The method of claim 10,

    The AC electric machine is an electric motor or a generator,

    The first energy transfer part is a rotor, the second energy transfer part is a stator,

    And the core is a stator core.
13. The method according to any one of claims 10 to 12,

    And said at least two three-phase power supplies are power supplies in combination of a three-phase pulse width modulation (PWM) power supply or three single-phase PWM power supplies.
14. The method according to any one of claims 10 to 12,

    And line voltages or line voltages of the at least two three-phase power supplies are connected to nodes between the windings of the delta-connected winding.
15. The method of claim 14,

    And the nodes and the line voltages or line voltages are each connected one-to-one.
16. A first energy transfer unit magnetically coupled with the second energy transfer unit;

    A second energy transfer comprising at least two three-phase windings;

    A core magnetically connecting said first energy transfer portion and said at least two three-phase windings; And

    A connection for directly connecting the at least two three-phase windings electrically;

    By said connecting portion, said at least two three-phase windings equivalently constitute one delta-connected winding; And

    And at least two or more three phase loads electrically connected to at least two or more three phase windings of the second energy transfer portion.
17. The method of claim 16,

    The AC electric machine is a transformer,

    The first energy transfer unit is a transformer primary stage, the second energy transfer unit is a transformer secondary stage,

    And the core is a transformer core.
18. The method of claim 16,

    The AC electric machine is an electric motor or a generator,

    The first energy transfer part is a rotor, the second energy transfer part is a stator,

    And the core is a stator core.
19. The method according to any one of claims 16 to 18,

    And three-phase power input terminals of at least two or more three-phase loads are connected to nodes between the windings of the delta-connected winding.

Images