KR20110060289A - Multiple wired electric machine system - Google Patents

Abstract

PURPOSE: A multiple winding type electrical machinery system is provided to enhance an efficiency by being made of plural converters, connected to a multiple winding type electric machinery and a multiply wound wire, and a system side multi-level converter. CONSTITUTION: The multiple winding type generator forms stator windings(122a-122c) with 3 phase insulated multiply wound wires. A rotor(123) rotates by supplying power for a stator winding. A plurality of generator side converters is connected to a generator stator multiple winding. A system side converter is connected to each generator side converter via an individual DC link and at the same time to the system side. Coils forming each phase are divided into plural groups and are wound round a stator(121).

Description

Multiple wired electric machine system

The present invention relates to an electric machine, and more particularly to a multi-wound electric machine system including a generator or an electric motor and a drive system for driving the same.

Renewable energy is an energy used by converting existing fossil fuels or converting renewable energy including sunlight, water, geothermal energy, and bioorganisms, and is recently becoming a future energy source for a sustainable energy supply system. I am getting it.

In particular, new and renewable energy has grown in importance due to the instability of oil prices and the regulatory response to the climate change convention.Solar, solar, biomass, wind, small hydro, geothermal, and marine energy (wave energy, tidal power, tidal current, etc.) , Renewable energy such as waste energy, and new energy fields such as fuel cell, coal liquefied gas and hydrogen energy.

Also, as is well known, a variety of turbines and solar cells are used to obtain power from energy sources such as wind, wave, tidal, tidal and solar power as renewable energy. For example, a synchronous generator may be driven using a rotary turbine. The system can be used.

In the renewable energy generation system using the wind, tidal power, tidal current as described above is a power converter (Power Converter), which is a variable voltage, variable frequency characteristics due to the variable wind speed or flow rate conditions It is a device for purifying high-quality secondary energy with constant voltage and constant frequency characteristics so as to link low-quality primary energy with a power system.

In particular, the generators that are widely applied in the renewable energy generation system market include a doubly-fed induction generator (DFIG) and a synchronous generator (SG).

FIG. 1 is a block diagram illustrating an example of a driving system that may be applied to a general three-phase synchronous generator, and illustrates a power converter having a back-to-back two-level converter.

In Figure 1 the reference numeral 31 denotes a capacitor provided in the DC- link terminal, reference numeral V _dc denotes a terminal voltage DC- link, reference numeral V _a, V _b, V _c represents the system (grid) voltage.

As shown, the structure of the power converter applied to the three-phase synchronous generator (SG) (1), the AC (AC) / DC (DC) converter (generator side converter) and the DC / AC converter (system side converter) It has a structure with an AC-DC-AC conversion function that converts AC power into DC power and then converts it into AC power.

More specifically, the output of the synchronous generator 1 is a single three-phase, DC-between the generator-side converter 10 connected to the synchronous generator and the grid-side converter 20 connected to the power grid (grid) side. The link stage is provided, and both converters share a DC-link stage.

At this time, the generator-side converter 10 and the grid-side converter 20 are constituted by a two-level converter having six switching elements (semiconductor switches) 11 and 21 as shown.

In addition, a plurality of power conversion units consisting of a generator-side converter 10, a DC-link stage provided with a capacitor 31, and a grid-side converter 20 are connected in parallel to each other in capacity, and are generally configured and operated as a parallel system. Can be.

That is, the plurality of generator-side converters 10 are connected in parallel to the synchronous generator 1, and the grid-side converters 20 are connected to each generator-side converter 10 with a DC-link terminal interposed therebetween. A plurality of power converters consisting of the side converter 10, the DC-link stage, the grid side converter 20 is connected in parallel to the generator 1 and the power system, to form a single integrated power converter as a whole will be.

In this structure, the DC-link stage voltage (V _dc ) provided between the generator-side converter 10 and the grid-side converter 20 so that energy generated through the rotor winding of the generator 1 can be transferred to the grid is Controlled to stay constant at all times.

On the other hand, Figure 2 is a schematic diagram showing the generator and grid (grid) control scheme in the system shown in Figure 1, showing a control function performed by each converter, the generator side converter is the power control of the generator, and generator side The power factor control of the voltage and the current is performed, and the grid-side converter performs the voltage control of the DC-link stage and the power factor control of the grid-side voltage and current.

In the case of parallel operation with a plurality of power converters, as shown in the illustrated example, the individual controllers are mounted to perform the control independently, and only the command value of the power control is divided and applied.

In the configuration of Figs. 1 and 2, L1 is a boost reactor, in which a filter 40 composed of LC or LCL, including this, is indicated by a dashed line, but such a filter may or may not be used.

However, even if a filter is not used, the boost reactor L1 must be used. When a filter is used, L1 is combined with a filter LC or LCL circuit and used for boost and filter.

In general, since the generated current converted using the power converter includes a lot of harmonics, most of them use a hardware filter to remove the harmonics of the current. Thus, the filter 40 is used to remove harmonics of current.

However, as shown in the figure, if each converter 10, 20 of the entire system is composed of only two-level converters, it is difficult to solve the problem of harmonic generation, and the size of the filter for solving the current harmonic problem increases. There is a problem.

In addition, compared to the conventional power converter composed of a back-to-back two-level converter, there is a need for an improved method in terms of cost and efficiency in terms of configuration and operation.

Accordingly, the present invention has been invented in view of the above, and an object of the present invention is to provide a multi-wound electric machine system which is improved in cost and efficiency compared to a system consisting of a single three-phase electric machine and a two-level converter only. There is this.

In order to achieve the above object, the present invention provides a multi-wound generator comprising a stator winding consisting of three insulated multiple windings; In order to drive the multi-wound generator, a plurality of generator-side converters connected to the stator multiple windings of the generator, and the grid side is connected to the grid side at the same time connected via each of the generator-side converter and the individual DC-link It provides a multi-wound electric machine system comprising a; power converter consisting of a converter.

Here, the multi-wound generator is characterized in that the coils constituting each phase is divided into a plurality of groups, wound on a stator, and the three-phase coils of each group are connected to each generator-side converter.

In addition, each generator-side converter is a three-phase two-level converter, characterized in that the grid-side converter is a cascade multi-level converter having a plurality of full-bridge converters connected to each generator-side converter by a separate DC-link.

In addition, the generator may be a synchronous generator or an induction generator.

In addition, the present invention provides a multi-wound motor comprising a stator winding comprising three insulated multiple windings; It is for driving the multi-wound motor, comprising a plurality of inverters connected to the stator multiple windings of the motor, and a grid-side converter connected to the grid side at the same time connected to each inverter and a separate DC-link It provides a multi-wound electric machine system comprising a power converter.

Here, the multi-wound motor is characterized in that the coils constituting each phase is divided into a plurality of groups, wound on a stator, and three-phase coils of each group are connected to each inverter.

In addition, each inverter is a three-phase two-level inverter, the grid-side converter is characterized in that the cascade multi-level converter having a plurality of full-bridge converters connected to each inverter by a separate DC-link.

The motor may also be a synchronous motor or an induction motor.

Accordingly, according to the multi-wound electric machine system of the present invention, it is composed of a multi-wound electric machine, a plurality of converters connected to the multi-wound, and a multi-level converter on the grid side, so that a single three-phase electric machine and a two-level Compared with the conventional system consisting only of the converter, there is an advantage in terms of cost and efficiency.

More specifically, the disadvantage of cascaded multi-level converters is that the use of a special transformer with three phases on the primary side and an insulated multi-tap on the secondary side becomes unnecessary. In addition, it can be used by connecting directly to a high-voltage grid (grid) without the use of a step-down transformer, there is an advantage that can reduce the harmonic current flowing into the system due to the use of a multi-level converter.

In addition, when the generator-side converter 210 is configured in a large capacity, it is possible to make a large capacity by using a plurality of small capacity converters. There is an advantage to configuring the installation.

In addition, even if a failure occurs in the generator-side converter, power generation can be continued except for a failed converter, thereby increasing the operating time of the generator and minimizing losses such as stopping power generation due to a converter failure.

In addition, when the three-phase two-level converter on the generator side and the full-bridge converter on the grid side are modularized, the connection lines between the modules correspond to the load lines, so that the modules can be freely arranged without affecting the operation of the converter. .

In the case of the parallel winding method, when the phase difference of the generated voltage occurs, a circulating current may be generated between the parallel windings to burn out the generator.However, when the multiple windings are used, the phase difference of the generated voltage may occur in each winding. Since they are electrically independent of each other, the problem of circulating current does not occur.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

The present invention relates to a multi-wound electric machine system, and relates to a multi-wound electric machine system including a generator or an electric motor and a driving system for driving the same.

The electric machine system of the present invention can be usefully applied to a system for obtaining electric power from energy sources such as wind power, wave force, tidal power, and tidal current as renewable energy, and a generator driven by a rotary turbine and a method for driving the same. It includes a drive system, the drive system includes a power converter for converting the power generated by the generator to provide to the power system.

In addition, the electric machine system of the present invention may include an electric motor driven by driving the electric power and a driving system for driving the same, the driving system converts the power supplied through the power system for driving the electric motor is applied to the electric motor That is to include a power converter (including an inverter).

In the present invention, the generator may be a synchronous generator or a induction generator. At this time, the generator is a multi-wound generator that divides the windings constituting each phase of the stator winding into a plurality of groups, the drive system of the present invention for driving the improved power conversion device to enable the driving of the multi-wound generator Has

In addition, in the present invention, the electric motor may be a synchronous motor or a induction motor. In this case, the motor is a multi-wound type electric motor implemented by dividing the windings constituting each phase of the stator winding into several groups, and the driving system of the present invention for driving the same is an improved power conversion device capable of driving the multi-wound motor. Has

As described above, when the present invention is an electric motor system instead of a generator system, the rotary turbine is a rotary load such as a fan, an impeller, and a propeller.

In the following description, the configuration of the present invention will be described by taking an example of a multi-winding synchronous generator system (which includes a generator and a driving system), and the system of the present invention can be applied to a generator or a motor system. Those skilled in the art to which the present invention pertains, in the case of the configuration of the electric motor system, in the following description, the generator is an electric motor, and the three-phase two-level converters of the generator side converter are inverters for driving the motor, that is, three phase It will be appreciated that it will be replaced by two-level inverters.

2 is a block diagram illustrating a multiple wired synchronous generator and a driving system thereof according to an embodiment of the present invention.

First, as an example, there is provided a rotary turbine 110 including a blade 111 to produce electric power from wind, and a multi-winding synchronous generator 120 thereby driving rotation.

When rotating the generator 120 in the rotary turbine 110, in the case of the winding type injecting an excitation current according to the speed or power to create a magnetic flux, in the case of a permanent magnet to generate the magnetic flux by itself to generate power.

In addition, the power conversion structure of the generator drive system, the DC-link stage is provided between the generator-side converter 210 connected to the synchronous generator 120 and the grid-side converter 220 connected to the power system (grid) side, The converter shares a DC-link stage.

Here, the generator-side converter 210 may be a two-level converter having six switching elements (semiconductor switches) 211, as shown, wherein the three-phase two-level converter 210 is connected to a separate DC-link. Is connected so that each two-level converter functions to control the power of the generator.

In addition, the stator winding of the synchronous generator 120 is composed of insulated multiple windings having three phases, after dividing the coil constituting each phase into a plurality of groups and winding the stator (see FIGS. 4 and 5), each group The three-phase coil of is connected to each two-level converter 210.

Referring to FIG. 2, it can be seen that nine two-level converters 210 are connected to the multi-winding synchronous generator 120 in which the windings are divided into nine equivalent groups in the stator windings. The power of the generator is controlled by 210.

The use of a generator having multiple windings insulated as described above makes it unnecessary to use a special transformer having three phases on the primary side and three taps on the secondary side, which are disadvantages of the cascade multi-level converter described later.

In addition, it can be used by directly connecting to a high-voltage grid (grid) without the use of a step-down transformer, there is an advantage that can reduce the harmonic current flowing into the system due to the use of a multi-level converter.

In addition, the grid-side converter 220 is a cascade multi-level (or H-bridge) configured by connecting a full-bridge converter 211 in a cascade form, for example, as illustrated. It can be a H-Bridge Multi-Level (HBML) converter. In FIG. 2, reference numeral 222 denotes a switching element constituting each full-bridge converter 221.

In the cascade multi-level converter 220 used in the present invention, the number of levels N may be configured as 7-levels as illustrated, which may be changed and may be configured as other level numbers. The number of DC-link capacitors is therefore determined. In general, each equivalent full-bridge converter 221 is three-level, two five-level and three seven-level.

As shown, the full-bridge converter 221 of the cascade multi-level converter 220, which is a grid-side converter, corresponds to each corresponding two-level on the generator side via an individual DC-link with a capacitor (not shown) installed. In connection with the converter 210, the DC-link voltages V _DC1 to V _DC9 are applied from the two-level converter 210.

In addition, in the configuration of FIG. 2, L1 is a boost reactor, in which a filter 230 including LC or LCL is indicated by a dotted line, but such a filter may or may not be used as in the prior art.

Thus, in the driving system of the multi-winding-type synchronous generator 120 of FIG. 2, the cascade multi-level converter 220 receives three-phase power from the grid side through the boost reactor L1 to control the DC-link voltage. Then, the voltages of the individual DC-link voltages V _DC1 to V _DC9 are controlled to a constant value.

As described above, in the case of connecting the plurality of generator-side converters 210 to the multi-wound generator 120 in the driving system of the present invention, in configuring the generator and the drive system for driving the generators, the generator-side converter 210 ) Can be made large by using several small converters.

For example, if the generator capacity is 9MW, 9MW is required when using one converter in the conventional configuration, but in the present invention, nine converters of 1MW can be used. This offers the advantage of reducing the cost and overall equipment cost, and also provides the advantage of constructing a larger capacity.

In addition, even if a failure occurs in the generator-side converter 210, since the power generation can be continued except the failed converter, it is possible to increase the operating time of the generator 120, it is possible to minimize the loss, such as stopping the power generation due to the converter failure. .

In addition, when the three-phase two-level converter 210 on the generator side and the full-bridge converter 221 on the grid side are modularized, since the connection lines between the modules correspond to the load lines, the modules may be freely disposed. It also has advantages.

In addition, in the case of the method using the parallel winding, when the phase difference of the generating voltage occurs, a circulating current may be generated between the parallel windings to burn out the generator. Even though they are electrically independent of each other, the problem of circulating current does not occur.

As mentioned above, the configuration of the generator drive system illustrated in FIG. 2 is applicable to the configuration of the motor drive system, wherein the cascade multi-level converter performs DC-link voltage control, and is connected to each DC-link. A phase two-level inverter controls the speed or torque of a multi-wound motor to drive rotary loads such as pumps, impellers, propellers and fans.

Of course, such a motor drive system has the same advantages as a generator drive system.

Meanwhile, referring to the winding structure of the motor / generator according to the present invention, first, FIG. 3 is a view illustrating a form of a conventional general concentrated winding two-pole three-phase generator / motor and showing a stator winding structure. to be.

As shown in the drawing, in a general concentrated generator / motor, a winding is performed by connecting a group of series coils or a plurality of groups of coils in parallel on one phase of the stator winding so that each phase has two output terminals.

On the other hand, Figure 4 is a view showing the form of a multi-wound three-phase generator / motor according to the present invention, a diagram showing a stator winding structure. Reference numeral 121 denotes a stator, reference numerals 122a, 122b and 122c denote stator windings, and reference numeral 123 denotes a rotor. This is a view showing an embodiment in which the series winding of each phase is composed of nine groups in the multi-wound three-phase generator / motor of FIG. 2, and the output terminals are 18 in each phase.

5 is a view showing another form of the multi-wound three-phase generator / motor according to the present invention, it shows that the stator winding can be configured in the form of a distributed winding.

The embodiments of the present invention have been described in detail above, but the scope of the present invention is not limited to the above-described embodiments, and various modifications of those skilled in the art using the basic concepts of the present invention defined in the following claims and Improved forms are also included in the scope of the present invention.

1 is a configuration diagram showing an example of a power conversion apparatus that can be applied to a conventional three-phase synchronous generator.

FIG. 2 is a schematic diagram illustrating a generator and a system control scheme in the system shown in FIG. 1, illustrating a control function performed by each converter.

3 is a view showing the shape of a conventional general concentrated two-pole three-phase power generator / motor, showing a stator winding structure.

Figure 4 is a view showing the form of a multi-wound three-phase generator / motor according to the present invention, showing a stator winding structure.

5 is a view showing another form of the multi-wound three-phase generator / motor according to the present invention, illustrating a stator winding of the distribution range.

<Explanation of symbols for the main parts of the drawings>

110: rotary turbine 120: generator

121: stator 122a, 122b, 122c: stator winding

210: generator side converter (2-level converter)

211: switching element

220: grid-side converter (cascade multi-level converter)

221: full-bridge converter 222: switching device

Claims (8)

A multi-wound generator comprising a stator winding consisting of three insulated multiple windings; In order to drive the multi-wound generator, a plurality of generator-side converters connected to the stator multiple windings of the generator, and the grid side is connected to the grid side at the same time connected via each of the generator-side converter and the individual DC-link A power converter composed of a converter; Multi-wound electric machine system comprising a. The method according to claim 1, The multi-wound generator is a multi-wound electric machine system, characterized in that the coil constituting each phase is divided into a plurality of groups are wound on the stator, and the three-phase coil of each group is connected to each generator side converter. The method according to claim 1 or 2, Each generator side converter is a three-phase two-level converter, The grid-side converter is a cascade multi-level converter having a plurality of full-bridge converters connected to each generator-side converter by separate DC-links. The method according to claim 1, The generator is a multi-wound electric machine system, characterized in that the synchronous generator or induction generator. A multi-wound motor comprising a stator winding consisting of three phases of isolated multiple windings; A power conversion system for driving the multi-wound motor, comprising a plurality of inverters connected to the stator multiple windings of the motor, and a grid-side converter connected to each inverter and a separate DC-link and simultaneously connected to the grid side. Device; Multi-wound electric machine system comprising a. The method according to claim 5, The multi-wound electric motor is a multi-wound electric machine system, characterized in that the coil constituting each phase is divided into a plurality of groups are wound on the stator and the three-phase coil of each group is connected to each inverter. The method according to claim 5 or 6, Each said inverter is a three-phase two-level inverter, The grid-side converter is a cascade multi-level converter having a plurality of full-bridge converters connected to each inverter by individual DC-links. The method according to claim 5, The electric motor system of claim 1, wherein the electric motor is a synchronous motor or an induction motor.

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