GB2526213A

GB2526213A - Rotating electrical machine system and wind power generation system

Info

Publication number: GB2526213A
Application number: GB1512808.5A
Authority: GB
Inventors: Masahiro Hori; Mamoru Kimura; Nobuhiro KUSUNO
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2013-03-08
Filing date: 2013-03-08
Publication date: 2015-11-18
Anticipated expiration: 2033-03-08
Also published as: TW201507323A; JP5908646B2; GB2526213B; WO2014136251A1; DE112013006792T5; JPWO2014136251A1; TWI516001B; GB201512808D0

Abstract

The present invention provides a rotating electrical machine system capable of preventing an increase in size of an entire rotating electrical machine and a reduction in the range of operation. The rotating electrical machine system according to the present invention comprises: a first rotating electrical machine constituted by a first stator having a first stator winding, and a first rotor having a first rotor winding and arranged on the inner diameter side of the first stator at a prescribed gap; a second rotating electrical machine constituted by a second stator having a second stator winding, and a second rotor having a second rotor winding and arranged on the inner diameter side of the second stator at a prescribed gap; and a power convertor electrically connected to the first and second rotating electrical machines. The rotating electrical machine system is configured to have the first and second rotating electrical machines, and the power convertor mechanically connected to a rotary shaft, and satisfies p1 / p2 > 1.8, where p1 represents the number of poles in one rotating electrical machine that is always operating for power generation, and p2 represents the number of poles in the other rotating electrical machine.

Description

DESCR:PTION Title of Invention: ROTATING ELECTRICAL MACHINE SYSTEMAND WIND

POWER GENERATION SYSTEM

Technical Field

[0001] The present invention relates to a rotating electrical machine system and a wind power generation system, particularly to a rotating electrical machine system and a wind power generation system, both of which are preferable to a system that is provided with a first rotating electrical machine (main generator) anda second rotating electrical machine (auxiliary generator)

Background Art

[0002] In recent years, there has been a focus on a generation system that uses natural energy, as used in wind power generation, solar power generation, or the like, in order to prevent global warming. ANong such generation systems, there are a great number of examples of using an alternating current excitation type rotating electrical machine as a generating apparatus in a wind power generation system in which wind power is used.

[0003] In a case of using an alternating current excitation type rotating electrical machine as a generating apparatus in a wind power generation system, it is necessary to supply excited power to a rotor winding in a rotating rotor during operation of the alternating current excitation type rotating electrical machine. To supply power to the rotor winding, usually, a slip ring and a brush are disposed, and conduction is provided by bringing the brush into contact with a rotating slip ring.

[0004] However, the amount of energy for performing generating operation in the wind power generation system is large, and when the slip ring and the brush are disposed to supply excited power after the generating operation is performed, wearing of the brush proceeds, thus requiring periodical maintenance.

[0005] Incidentally, in the wind power generation system, the alternating current excitation type rotating electrical machine is installed in a nacelle on a tower of a windmill, and periodical maintenance is necessarily performed in a limited space of the inside of the nacelle. Thus, reducing maintenance is required by, for example, making the alternating current excitation type rotating electrical machine brushless.

[0006] There is disclosed a technology for a brushless alternating current excitation type rotating electrical machine, for example, in PTL 1. In PIL 1, there is disclosed performing generating operation in a manner in which power of a system is rectified to a direct current by a rotating exciter and a power converter, both of which are disposed coaxially with an alternating current excitation synchronous generator, the direct current is conducted to a stator of the rotating exciter, power is supplied to a rotor according to the principle o the synchronous generator, and then power of which the voltage and the frequency are converted by the power converter is supplied to a rotor of the alternating current excitation synchronous generator.

Citation List Patent Literature [0007] PTL: JP-A-2002-136191

Disclosure of Invention

Technical Problem [0008] In a general alternating current excitation synchronous generator in the related art, power of a system is supplied to a rotor through a power converter when the speed of the rotor is less than or equal to a synchronous speed, and power of the rotor is supplied to the system through the power converter when the speed of the rotor is greater than or equal to the synchronous speed.

[0009] In OTt 1, however, even though it is possible to supply power from the system to the alternating ourrent excitation synchronous generator, the voltage of the system is supplied to the rotatinq exciter after rectified by a rectifier. Since the rectifier is installed, it is not possible to supply power from the alternating current excitation synchronous generator to the system. Therefore, the extent of operation of the one in PTIJ 1 is narrow when compared with that of a general alternating current excitation synchronous generator in the related art.

[0010] In PTL 1, since the rotating exciter is disposed in addition to the generator, the total size of the generator is increased by the disposed rotating exciter, and a wide arrangement space is required.

[0011] The invention is devised with consideration of the above points, and an object thereof is to provide a rotating electrical machine system and a wind power generation system in which, even when the systems are provided with a first rotating electrical machine and a second rotating electrical machine, the rotating electrical machines can be brushless, and upsizing of the entire rotating electrical machines and reduction of the operable range thereof can be prevented.

Solution to Problem [0012] According to an aspect of the invention, in order to achieve the above object, there is provided a rotating electrical machine system including a first rotating electrical machine that is configured by a first stator which includes a first stator winding and a first rotor which includes a first rotor winding and is arranged on an inside diameter side of the first stator with a predetermined gap interposed therebetween, a second rotating electrical machine that is configured by a second stator which includes a second stator winding and a second rotor which includes a second rotor winding and is arranged on an inside diameter side of the second stator with a predetermined gap interposed therebetween, and a power converter that is electrically connected to the first and the second rotor windings, in which the first and the second rotors and the power converter are mechanically connected to a rotor shaft, and given that the number of poles in one of the two rotating electrical machines that performs generating operation at all times is P:, and the number of poles in the other rotating electrical machine is P2, pl/p2 > 1.8 is established.

[0013] According to another aspect of the invention, there is provided a wind power generation system including a rotor that rotates by receiving wind, the rotating electrical machine system that has the above configuration and is connected to the rotor via a main shaft, a nacelle that accommodates the rotating electrical machine system, and a tower that supports the nacelle, in which the first and the second rotating electrical machines are rotated by torque of the rotor, and the stator windings of the first and the second rotating electrical machines are connected to a power system.

Brief Description of Drawings

[0014] [Fig. 1] Fig. 1 is a schematic configuration diagram illustrating a first embodiment of a rotating electrical machine system of the invention.

[Fig. 2] Fig. 2 is a diagram for describing a flow of energy in a case where the speed of rotation of a rotor shaft in the first embodiment of the rotating electrical machine system of the invention is less than the synchronous speed of a main generator.

[Fig. 3] Fig. 3 is a diagram for describing a flow of energy in a case where the speed of rotation of the rctor shaft in the first embodiment of the rotating electrical machine system of the invention is greater than the speed of rotation of the main generator.

[Fig. 4] Fig. 4 is a characteristic diagram illustrating a relationship between a slip of the main generator and output of the main generator, output of an auxiliary generator, and output of a system in a case of Condition 1.

[Fig. 5] Fig. 5 is a diagram representing a relationship between a slip of the main generator and a slip of the auxiliary generator in a case of Condition 2.

[Fig. 61 Fig. 6 is a diagram for describing a flow of energy when the speed of rotation of the rotor shaft is less than the synchronous speed of the main generator in the case of Condition 2.

[Fig. 7] Fig. 7 is a diagram representing a relationship between a slip of the main generator and a slip of the auxiliary generator in a case of Condition 3.

[Fig. 8] Fig. 8 is a diagram for describing a flow of energy when the speed of rotation of the rotor shaft is greater than the speed of rotation of the main generator in the case of Condition 3.

[Fig. 9] Fig. 9 is a characteristic diagram illustrating a relationship between a slip of the main generator and output of the main generator and output of the auxiliary generator in a case of Condition 4.

[Fig. 10] Fig. l0isacross-sectionalviewillLlstrating a second embodiment of the rotating electrical machine of the invention.

[Fig. 11] Fig. ilisacross-sectionalviewillustrating a third embodiment of the rotating electrical machine of the invention.

[Fig. 12] Fig. l2isacross-sectionalviewillustrating a fourth embodiment of the rotating electrical machine of the invention.

[Fig. 13] Fig. 13 is a schematic configuration diagram illustrating a wind power generation system to which the rotating electrical machine system of the invention is applied (fifth embodiment)

Description of Embodiments

[0015] Hereinafter, a rotating electrical machine system and a wind power generation system of the invention will be described on the basis of the illustrated embodiments. Each embodiment will be described with the same sign for the same constituent.

First Embodiment [0016] Fig. 1 illustrates a first embodiment of the rotating electricai machine system of the invention. Both a below-described main generator and an auxiliary generator are radial gap type rotating electrical machines in whioh a gap between a stator and a rotor is formed in a diametrical direction.

[0017] As illustrated in Fig. 1, a rotating electrical machine system 1 of the present embodiment is provided with a main generator 2 that is a first rotating electrical machine which operates as a generator to transport generated power to a power system, an auxiliary generator 3 that is a second rotating electrical machine which operates in two ways as either an exciter or a generator depending on operating conditions, and a power converter 4 that is electrically connected to the main generator 2 and the auxiliary generator 3, all of which are arranged in the same rotating electrical machine frame 16.

[0018] The main generator 2 is configured by a main generator stator 6, a main generator rotor 5 that is arranged on the inside diameter side of the main generator stator 6 with a predetermined gap disposed therebetween, a three-phase main generator stator winding 7 that is wound as a short-pitched double layer winding inside a slot which is disposed in the main generator stator 6, and a three-phase main generator rotor winding 8 that is wound as a full-pitched double layer winding inside a slot which is disposed in the main generator rotor 5. The three-phase main generator stator winding 7 and the three-phase main generator rotor winding 8 are electrically arranged at an intervai of 120°.

[0019] Similarly, the auxiliary generator 3 is configured by an auxiliary generator stator 9, an auxiliary generator rotor that is arranged on the inside diameter side of the auxiliary generator stator 9 with a predetermined gap disposed therebetween, a three-phase auxiliary generator stator winding 11 that is wound as a short-pitched double layer winding inside a slot which is disposed in the auxiliary generator stator 9, and a three-phase auxiliary generator rotor winding 12 that is wound as a full-pitched double layer winding inside a slot which is disposed in the auxiliary generator rotor 10.

The three-phase auxiliary generator stator winding 11 and the three-phase auxiliary generator rotor winding 12 are electrically arranged at an interval of 120°.

[0020] The main generator 2 and the auxiliary generator 3 described above have different operating modes as will be described later. Specifically, the main generator 2 performs generating operation at all times, but the auxiliary generator 3 may operate as an exciter or may operate as a generator, depending on the speed of rotation. Output of the main generator 2 is greater than or equal to output of the auxiliary generator 3.

[0021] The power converter 4 is configured by a power converter 13 that is electrically connected to the main generator 2 and a power converter 14 that is electrically connected to the auxiliary generator 3. The power converter 13 and the power converter 14 are electrically connected through direct current.

When the power converter 13 and the power converter 14 are connected through alternating current, each of the power converter 13 and the power converter 14 needs to be provided with a power converter for AC -* DC -* AC. However, by connecting the power converter 13 and the power converter 14 through direct current, each of the power converters 13 and 14 only needs to convert AC and DC, and the functions that each of the power converter 13 and 14 has can be reduced by half.

[0022] The main generator 2, the auxiliary generator 3, and the power converter 4 described above are mechanically connected to a rotor shaft 15.

[0023] That is to say, the main generator stator 6 and the auxiliary generator stator 9 are connected to the rotating electrical machine frame 16 via a plurality of arms 17, but the main generator rotor 5 is connected via a plurality of arms 19 to the outside of a power converter frame 18 in which the power oonverters 13 and 14 are arranged, and the inside of the power converter frame 18 is mechanically connected to the rotor shaft 15 in a rotatable manner. In addition, the power converter frame 18 in which the power converters 13 and 14 are arranged is arranged inside the main generator rotor 5. This is because the main generator 2 has greater output than the auxiliary generator 3 and thus is larger. Therefore, it is possible to secure a wide space for incorporating the power converter 4.

[0024] In other words, the above-described configuration means that the rotor shaft 15 rotating allows the main generator 2, the auxiliary generator 3, and power converter 4 to rotate simultaneously at the same number of rotations. Accordingly, problems in that pieces of wiring that connect the main generator 2 and the power converter 13, the power converter 13 and the power converter 14, and the power converter 14 and the auxiliary generator 3 are twisted do not arise.

[0025] The power converter 4 needs to receive instruction information from the outside and transmit operating status information in order to be controlled according to operating conditions. Therefore, since the power converter 4 rotates in the present embodiment, wireless communication is effective in transmission of information, and the power converter 4 is preferably connected to a device that can transmit and receive information wirelessly.

[0026] Next, a description will be provided for a flow of energy in the rotating electrical machine system.

[0027] Fig. 2 illustrates a flow of energy in a case where the speed of rotation of the rotor shaft 15 is less than the synchronous speed of the main generator 2.

[0028] In Fig. 2, the main generator stator windIng 7 and the auxiliary generator stator winding 11 are electrically connected to a power system. A power system has a commercial frequency, and an alternating current flows therein. Thus, by the voltage changing temporally and the auxiliary generator rotor 10 rotating, an induced current is generated in the auxiliary generator rotor winding 12 depending on the number of magnetic poles and the speed of rotation. The auxiliary generator rotor winding 12 is electrically connected to the main generator rotor winding 8 via the power converter 4.

Because of the induced current that is generated by rotation of the auxiliary generator rotor winding 12, an exciting current can be provided to the main generator 2.

[0029] The auxiliary generator 3, therefore, operates as an exciter in a condition where the speed of rotation of the rotor shaft 15 is less than the synchronous speed of the main generator 2. A direct current is required to flow in the main generator rotor winding 8 when the speed of rotation of the rotor shaft 15 is the same as the synchronous speed of the main generator 2, but by applying a direct current voltage with the power converter 4, the auxiliary generator 3 can be operated.

[0030] Fig. 3 illustrates a flow of energy in a case where the speed of rotation of the rotor shaft 15 is greater than the speed of rotation of the main generator 2.

[0031] In Fig. 3, an induced current that is generated in the main generator rotor winding 8 flows into the auxiliary generator rotor winding 12 through the power converter 4 and further flows into the auxiliary generator stator winding 11 from the auxiliary generator rotor winding 12. This supplies power from the auxiliary generator stator winding 11 to the power system.

[0032] The auxiliary generator 3, therefore, operates as a generator in a condition where the speed of rotation of the rotor shaft 15 is greater than the speed of rotation of the main generator 2.

[0033] Accordingly, an exciting current can flow in the main generator rotor winding 8 and the auxiliary generator rotor winding 12 without using a slip ring and a brush (brushless) and thus maintenance due to wearing of a brush is not necessary.

[0034] Although an example of using wireless communication in transmission of information to the power converters 13 and 14 is described in the present embodiment, the amount of energy required for transmitting information is not large. Thus, the extent of wearing is small even if a brush is used. Therefore, a brush and a slip ring may be disposed in order for the power converters 13 and 14 to transmit information. Similarly, a brush and a slip ring may be disposed for grounding.

[0035] Characteristics of an alternating current excitation type rotating electrical machine are determined by a slip s that is represented in Equation 1.

[0036] s = (N0 -N) / N0 (Equation 1) [0037] Here, N0 is a synchronous speed, and N is a speed of rotation.

[0038] Characteristics of a brushless alternating current excitation type rotating electrical machine are determined by two slips of a slip s of a main generator and a slip 2 of an auxiliary generator because a brushless alternating current excitation type rotating electrical machine is configured by two alternating current excitation type rotating electrical machines of a main generator and an auxiliary generator. In addition, the synchronous speed N0 is determined by the number of poles. Thus, it is necessary to appropriately choose the number of poles p in the main generator and the number of poles P2 in the auxiliary generator according to specifications of a generator. Here, the slip s-of the main generator and the slip 52 of the auxiliary generator have the following relationship.

[0039] = 1 -P2K1 -s) / p (Equation 2) [0040] Hereinafter, characteristics with respect to p:/p2 will be described for oases. Since the alternating current excitation type rotating electrical machine has a variable speed range, it is assumed that the lower limit thereof is s, and the upper limit thereof is S. In addition, when the main generator and the auxiliary generator are electrically connected to the power system, and output thereof is negative, this means that energy from the power system is supplied thereto.

[0041] Condition 1: P: < P2, pl/p2/ > (1 -s) Fig. 4 illustrates a relationship between the slip s and output of the main generator, output of the auxiliary generator, and the total output in Condition 1. As is apparent from Fig. 4, in Condition 1, the output of the allxiliary generator is negative in a high output region. Thus, by the corresponding amount of the negative output, the output of the main generator is increased from the total output. Therefore, since it is necessary to arrange the main generator according to the output of the main generator, the main generator is upsized.

[0042] Condition 2: p < P2, pl/p2/ < (1 -s) Fig. 5 illustrates the graph of Equation 2 with a straight line A in Condition 2. The horizontal axis of the graph is si, and the vertical axis thereof is 52. It is understood from Fig. 5 that 2 = 0 is present within an operable range. The auxiliary generator is in a state of operating synchronously in the case of s2 = 0. Thus, magnetic fluxes are not interlinked with the rotor, and energy cannot be supplied to the rotor from the stator (Fig. 6 illustrates this state) . For this reason, energy cannot be supplied to the rotor of the main generator, and the main generator cannot operate.

[0043] It is therefore necessary to operate the main generator while avoiding a speed of rotation near 2 = 0. As illustrated in Fig. 5, an inoperable range is present within the operable range, and the operable range is decreased by the extent of the inoperable range.

[0044] Condition 3: m > P2, pi/p2 < (1 -3) Fig. 7 illustrates the graph of Eguation 2 with a straight line B in Condition 3. The horizontal axis of the graph is si, and the vertical axis thereof is i. It is understood from Fig. 7 that s2 = 0 is present within the operable range. The auxiliary generator is in a state of operating synchronously in the case of s2 = 0. Thus, energy of a direct current is supplied from the power converter to the rotor (Fig. 8 illustrates this state) . However, the temperature of the power converter may be high when the power converter outputs a direct current.

[0045] It is therefore necessary to operate the main generator while avoiding a speed of rotation near 52 = 0. As illustrated in Fig. 7, a hardly operable range is present within the operable range, and the operable range is decreased by the extent of the hardly operable range.

[0046] Condition 4: P: > P2, Pi/P2 C 1.8 Fig. 9 illustrates a relationship between the maximum output of the main generator and the maximum output of the auxiliary generator with respeot to a ratio of the numbers of poles in Condition 4. An output surplus in Fig. 9 is defined as follows.

[0047] Output Surplus = (Maximum Output of Main Generator + Maximum Output of Auxiliary Generator) -1 That is to say, output of the generator is reguired to be greater than the total output in a case of output surplus != 0, and thus the generator is upsized. It is understood from Fig. 9 that the output surplus occurs when the ratio of the numbers of poles p/p2 is less than 1.8.

[0048] It is, from the above description, not necessary for the generator to have large output beoause the output surplus does not occur (the generator can operate while avoiding the hardly operable range) when the ratio of the numbers of poles pl/p2 is greater than 1.8 (pl/p2 >1.8), andupsizingof the brushless alternating current excitation type rotating electrical machine and reduction of the operable range can be prevented.

Second Fxrbodiment [0049] Fig. 10 illustrates a second embodiment of the rotating electrical machine system of the invention.

[0050] The power oonverter 4 is arranged inside the main generator rotor 5 in the above first embodiment. However, in the present embodiment, the power converter 4 is arranged over the inside of both the main generator rotor 5 and the auxiliary generator rotor 10 as illustrated in Fig. 10. In addition, the main generator stator 6 and the auxiliary generator stator 9 are connected to the rotating electrical machine frame 16 via the plurality of arms 17. The main generator rotor 5 and the auxiliary generator rotor 10 are connected via the plurality of arms 19 and a plurality of arms 20 to the outside of the power converter frame 18 in which the power converter 4 is arranged. The inside of the power converter frame 18 is connected to the rotor shaft 15. In the same manner as the first embodiment, given that the number of poles in the main generator 2 that performs generating operation at all times is P1, and the nurber of poles in the other auxiliary generator 3 is P2 in the present embodiment, pl/p2 > 1.8 is established.

[0051] According to the embodiment, the same effect as the first embodiment is apparently achieved, and the power converter 4 can be arranged further on an inner circumference side. Thus, centrifugal force applied to the power converter 4 can be reduced.

Third Embodiment [0052] Fig. 11 illustrates a third embodiment of the rotating electrical machine system of the invention.

[0053] In the present embodiment illustrated in Fig. 11, the main generator stator winding 7 and the main generator rotor winding 8 are arranged as overlapping with each oTher in a diametrical direction, and so are the auxiliary generator stator winding 11 and the auxiliary generator rotor winding 12. In the same manner as the first embodiment, given that the number of poles in the main generator 2 that performs generating operation at all times is Pi, and the number of poles in the other auxiliary generator 3 Is P2 In the present embodiment, pi/p2 > 1.8 is established.

[0054] According to the embodiment, the same effect as the first embodiment is apparently achieved, and the size of the generator system can be reduced because the axial length of the generator system can be reduced.

Fourth Embodiment [0055] Fig. 12 illustrates a fourth embodiment of the rotating electrical machine system of the invention.

[0056] In the embodiment illustrated in Fig. 12, a stepped frame 21 that is in accordance with the outside diameter of the main generator 2 and the auxiliary generator 3 is used in the configuration of the first embodiment illllstrated in Fig. 1.

That is to say, the stepped frame 21 is configured in a manner in which a part where the main generator 2 is arranged and a part where the auxiliary generator 3 is arranged have a different diameter and thus are stepped. In the same manner as the first embodiment, given that the number of poles in the main generator 2 that performs generating operation at all times is P1, and the number of poles in the other auxiliary generator 3 is P2 in the present embodiment, p-/p2 > 1.8 is established.

[0057] According to the embodiment, the same effect as the first embodiment is apparently aohieved, space is further saved without redundant space, and the generator system can be lightened in weight.

Fifth Embodiment [0058] Fig. 13 illustrates a fifth embodiment in which the rotating electrical machine system of the invention is applied to a wind power generation system.

[0059] As illustrated in Fig. 13, the wind power generation system in the present embodiment is configured by a rotor 24 that rotates by receiving wind, a rotating electrical machine system 22 of the invention that is connected to the rotor 24 via a speed increaser 23, a nacelle (not illustrated) that accommodates the rotating electrical machine system 22, and a tower (not illustrated) that snpports the nacelle. A main generator 25 and an auxiliary generator 26 are rotated by torque of the rotor 24, and a main generator stator winding and an auxiliary generator stator winding are connected to a power system 27.

[0060] Accordingly, the rotating electrical machine system 22 can convert the energy of wind that the rotor 24 receives into electrical energy and transmit the electrical energy to the power system 27.

[0061] According to the present embodiment, since the rotating electrical machine system in the above embodiment is used, upsizing of apparatuses can be prevented, and this can contribute to downsizing of the nacelle.

[0062] A power converter 28 can be protected from excessive power that is applied at the time of a system failure by disposing a circuit breaker 29 in parallel with the power converter 28. The invention may be further applied to a gearless system that does not have the speed increaser 23.

[0063] The invention is not limited to the above embodiments and inoludes various modification examples. For example, the above embodiments are described in detail in order to facilitate understanding of the invention, and not all of the described configurations are necessarily inoluded in an embodiment of the invention. In addition, it is possible to replace a part of configurations in an embodiment with configurations in another embodiment, and it is also possible to add configurations in another embodiment to configurations in an embodiment. In addition, a part of configurations of each embodiment can be removed or replaced with another configuration, or another configuration can be added thereto.

Reference Signs List [0064] 1, 22 rotating electrical machine system, 2, 25 main generator, 3, 26 auxiliary generator, 4, 13, 14, 28 power converter, 5 main generator rotor, 6 main generator stator, 7 main generator stator winding, 8 main generator rotor winding, 9 auxiliary generator stator, 10 auxiliary generator rotor, II auxiliary generator stator winding, 12 auxiliary generator rotor winding, 15 rotor shaft, 16 rotating electrical machine frame, 17, 19, 20 arm, 18 power converter frame, 21 stepped frame, 23 speed increaser, 24 rotor, 27 power system, 29 circuit breaker