GB2518989A

GB2518989A - Power generation system

Info

Publication number: GB2518989A
Application number: GB1419765.1A
Authority: GB
Inventors: Tomomichi Ito; Nobuhiro KUSUNO; Mamoru Kimura
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2012-07-30
Filing date: 2013-07-10
Publication date: 2015-04-08
Also published as: JP5988750B2; JP2014027824A; GB201419765D0; WO2014021066A1; DE112013003764T5

Abstract

The purpose of the present invention is to provide a power generation system capable of improving continuity in operation when an abnormality occurs in a generator or a control device. In order to solve the abovementioned problem, the power generation system comprises: a generator (101) having a plurality of stator windings (10012, 10013) provided on a stator; power convertors (31, 32) provided on each stator winding; a sensor provided on each stator winding or on each power convertor to detect the state thereof; and an abnormality detection means for detecting the abnormality in the stator windings or the power convertors on the basis of the output from the sensor. The abnormality detection means outputs the presence or absence of an abnormality for each stator winding or each power convertor, and when the abnormality detection means outputs the presence of an abnormality, the power convertor in which the abnormality was detected or the power convertor provided on the stator winding in which the abnormality was detected cuts off the current of the stator winding.

Description

DESCRIPTION

Title of the Invention

ELECTRIC POWER GENERATOR SYSTEM

Technical Field

[0001] The present invention relates generally to electric power generator systems that use power converters to control qualities of the electric power generated. More particularly, the invention is directed to electric power generator systems that allow for improvement in operational continuity.

Background Art

[0002] A large amount of electric energy generated by wind power generator systems is used worldwide as a principal renewable-energy supply sources beyond electric energy generated by other types of power generating systems such as a photovoltaic power generator system and geothermal power generator system. The generator in such a wind power generator system is disposed inside a nacelle of a limited space, and thus there are restrictions on making the generator large. Attempting at greater generating capacity, on the other hand, renders it difficult to avoid the upsizing of rotors and stators. In connection with these drawbacks, Patent Document 1, for example, describes a power generator system including one generator having a plurality of rotors therein, for enhanced generator efficiency.

[0003] According to Patent Document 1, the generator in the power generator system includes a first and a second rotor, and as at least one of the rotors rotates, the generator converts motive power of at least the particular rotor into electrical energy via a magnetic circuit formed by a stator and the two rotors, and then outputs the electrical energy to the stator to generate electricity. Rotating magnetic* fields developed during the generation of electricity, and the first and second rotors will rotate while maintaining predetermined collinear relationships in rotational speed between each other. The generator also includes a first and a second impeller. The first impeller converts kinetic energy of a fluid into rotational kinetic energy and after transmitting this energy to the first rotor, exerts a first torque upon the first rotor to rotate it in one direction.

The second impeller converts the kinetic energy of the fluid into rotational kinetic energy and after transmitting this energy to the second rotor, rotates the second rotor in a direction opposite to the rotational direction of the first rotor, thus exerting a second torque greater than the first torque, upon the second rotor.

Prior Art Documents

Patent Documents [0004] Patent Document 1: JP-2009-185782-A

Summary of the Invent ion

Problem to be Solved by the Invention [0005] In recent years, the expansion of wind power generator systems in capacity has been continuing and systems with a wind turbine tower exceeding 70 m high are increasing. In addition, offshore as well as land-based installation cases are increasing.

[0006] Furthermore, with the upscaling of wind turbines, repairing in case of device trouble has been becoming difficult, and access to the wind turbines is difficult to gain, particularly on the ocean. It is desired, therefore, that maintenance loads be reduced by, for example, extending part replacement periods and maintenance periods.

[0007] To an operator of a wind power generator system, while reduction in maintenance loads is pivotal, since repairs cannot always be conducted immediately after occurrence of an abnormality, it is desirable that even after the occurrence of the abnormality and even in exchange of a decrease in generable power, until the abnormality has been corrected, the wind power generator system should remain able to continue to generate electricity, for increasing system availability.

[0008] For the power generator system in Patent Document 1, however, no description is given of the continuity of operation upon the occurrence of an abnormality relating to the generator or a control device.

[00091 Accordingly, an object of the present invention is to provide an electric power generator system enhanced in operational continuity even in case of trouble with a generator or a control device.

Means for Solving the Problem [0010] To solve the above problem, an electric power generator system according to an aspect of the present invention includes the following: an electric generator including a rotor, stators facing the rotor, and a plurality of stator windings disposed in the stators; electric power converters each including an inverter disposed at a power grid side, a converter disposed at the generator side, and a capacitor disposed between the inverter and the converter, the power converter being provided for each of the stator windings; sensors each provided for one of the stator windings or power converters, each sensor being adapted to detect a state of the stator-windings or power converters; and means that detects an abnormality of the stator windings or power converters according to a particular output of the sensors. The abnormality detection means is further configured to output a signal that denotes presence/absence of an abnormality for each of the stator windings or power converters. If any information indicating existence of an abnormality is output from the abnormality detection means, the power converter in whichabnormality was detected or the power converter provided for the stator winding in which abnormality was detected serves to cut of f a current f lowing through the stator winding.

Effects of the Invention [0011] In accordance with the present invention, provided is a power generator system that can enhance operational continuity even in case of trouble with a generator or a control device.

Brief Description of the Drawings

Fig. 1 is a schematic diagram of an entire power generator system according to a first embodiment of the pre sent invention.

Fig. 2 is an explanatory diagram showing a flow of control of the power generator system according to the first embodiment.

Fig. 3 is an explanatory diagram showing a configuration of a power converter in the first embodiment.

Fig. 4 is an explanatory diagram that shows internal parts layout of a power generator in the first embodiment.

Fig. 5 is an explanatory diagram showing relative sizes of internal devices of the power generator in the first embodiment.

Fig. 6 is an axial sectional view of the power generator in the first embodiment.

Fig. 7 is an explanatory diagram of a power converter controller included in the first embodiment.

Fig. 8 is an explanatory diagram of a power converter controller included in a second embodiment of the present invention.

Fig. 9 is an explanatory diagram showing a flow of control of a power generator system according to a third embodiment of the present invention.

Fig. 10 is an explanatory diagram of a power converter controller included in the third embodiment.

Fig. 11 is an explanatory diagram of a power converter controller included in a fourth embodiment of the present invention.

Fig. 12 is an axial sectional view showing an example of a power generator in a fifth embodiment of the present invention.

Fig. 13 is an axial sectional view showing another example of a power generator in the fifth embodiment of the present invention.

Fig. 14 is an explanatory diagram showing a flow of control of a power generator system according to a sixth embodiment of the present invention.

Fig. 15 is an explanatory diagram of a power converter controller included in the sixth embodiment.

Fig. 16 is an explanatory diagram showing a flow of control of a power generator system according to a seventh embodiment of the present invention.

Fig. 17 is an explanatory diagram showing a configuration of a converter in the seventh embodiment.

Fig. 18 is an explanatory diagram that shows internal parts layout of the power generator in the seventh embodiment.

Fig. 19 is a diagram f or describing how voltage pulsations at a neutral point are offset according to the seventh embodiment.

Modes for Carrying Out the Invention [00131 Hereunder, embodiments preferred for carrying out the present invention will be described using the accompanying drawings. The following merely describes examples and is not intended to limit a mode of carrying out the invention to the specific embodiments set forth below. The invention may be modified in various forms besides the following embodiments.

First Embodiment [00141 A first embodiment is described below using Figs. 1 to 7. Fig. 1 shows an outline of a wind power generator system including an electric power generator system of the present embodiment. As schematically shown in the figure, the wind power generator system 1 includes: blades 10 that receive a force of wind and obtain a turning force; a hub 11 that transmits the torque of the blades 10 to a shaft 14; a generator/converter section 100 that connects mechanically to the shaft 14, converts mechanical input energy into electricity, and transmits the electricity to a power grid 2; a nacelle 60 connected to the shaft 14 and containing a part of the shaft 14 and the generator/converter section 100; and a tower 70 that supports the nacelle GO rotatable in a horizontal direction.

At an upper section of the nacelle 60 is set up an anemometer 203, output information from which is input to a host controller 1000. In addition, a pitch angle controller 12 (shown in Fig. 2) that controls an angle of the blades 10 is disposed at a connection between the hub 11 and the blades 10.

[00151 As shown in Fig. 2, the generator/converter section includes an electrical generator 101 described later herein, power converters 31 and 32, and a power converter controller 2000 that controls the power converters 31 and 32. Electric power that the generator 101 has generated is frequency-converted by the power converters and then transmitted to the power grid 2.

[00161 A control system of the wind power generator system 1, and detailed configurations of various sections constituting the generator/converter section 100 of the wind power generator system 1 are described' below.

[00171 The wind power generator system 1 is divided into two major controllers. One of the controllers is a host controller 1000 that calculates a pitch angle command value "4ref" and a total transmit-to-grid power command value (generated-power command value) "Pref" of the power converters 31, 32, to control a rotating speed of the blades 10 according to a wind velocity that the anemometer 203 has detected. The other controller is a power converter controller 2000 that controls power to be transmitted to the power grid 2, in accordance with the generated-power command value) "Pref" that is output from the host controller 1000.

[0018] The host controller 1000 receives an output "IT" from the anemometer 203, a calculation result of a generated-power value P from the power converter controller 2000, a spinning blade angular velocity meter 203, a calculation result of a generated-power value P frter herein. The host controller 1000 also outputs the pitch angle command value "4ref" and the total generated-power command value "Pref" of the power converters 31, 32.

[0019] The pitch angle command value "ref" that has been ii output from the host controller 1000 is input to the pitch angle controller 12. The pitch angle controller 12 then controls a pitch angle of the blades 10 in accordance with the received pitch angle command value "tref'. The control of the pitch angle enables a swept area of the blades to be changed.

[00201 The generated-power command value "Pref" that has been output from the host controller 1000 is input to the power converter controller 2000. The power converter controller 2000 then controls the power converters 31, 32 so that total active power that the power converters 31, 32 receive from the generator 101 will match the above power command value.

If the power generator system error signal LERR that has been output from the power converter controller 2000 is active (in the present embodiment, when the error detection signal is in a state of 0, LERR is active, denoting that an abnormality has been detected, and when the error detection signal is in a state of 1, L_ERR is not active, denoting a normal state), then the host controller 1000 determines that a maximum blade deceleration torque value obtained from the generator/converter section 100 has decreased by half, arid limits each of the pitch angle command value "4)ref' and the total generated-power command value "Pref". The limiting here refers to controlling the pitch angle command value "4'ref" for a reduction in swept area, and controlling the total generated-power command value "Pref" for a reduction in the command value itself.

The limitation of the pitch angle command value "cjref" enables the wind-generated torque to be reduced and excessive rotation of the blades 10 to be avoided.

[00221 Next, the generator/converter section 100 is described in further detail below.

[0023] The generator 101 is a permanent-magnet synchronous generator including two sets of three-phase stator windings, 10012 and 10013. The power converters 31, 32 have the same configuration. This configuration is *intended for standard use of a general power conditioning system and does not mean exclusion of different power converter configurations.

The power converters may also share inverters and capacitors, as described later.

[0 024 The power converter 31 includes a converter 21 connected to the generator 101, more specifically, connected to the three-phase stator winding 10012, an inverter 23 connected to the power grid 2, a smoothing capacitor 3lcdc disposed between the converter 21 and the inverter 23, a voltage sensor 301 that detects a stator winding voltage "vstl", a current sensor 302 that detects a stator winding current "istl", avoltage sensdr 303 that detects a terminal-to-terminal voltage of the smoothing capacitor 3lcdc, and a current sensor 304 that detects a power grid output current "igi". Output signals from these voltage sensors and current sensors are input to the power converter controller 2000. To enable the power converter 31 to receive desired power from the stator winding 10012 of the generator 101 and transmit the power to the power grid 2, the power converter controller 2000 calculates a value of a gate signal Gatel which is a control signal for the converter 21 and the inverter 23, and outputs the calculated gate signal level to the power converter 31.

More specifically, the converter 21 is caused to output a voltage that is the same in frequency as, and lagging in phase behind, the voltage "vstl" of the stator winding 10012, and thus in such a way that active power will be supplied from the stator winding 10012 to the power converter 31 and the smoothing capacitor 3lcdc will have its voltage "vdcl" reaching a predetermined threshold level, the inverter 23 is caused to output a voltage that is leading in phase relative to a voltage "vg" developed at a point of interconnection to the power grid 2. The active power obtained from the stator winding 10012 will be consequently transmitted to the power grid 2.

[00251 The power converter 32 includes a converter 22 connected to the generator 101, more specifically, connected to the three-phase stator winding 10013, an inverter 24 connected to the power grid 2, a smoothing capacitor 32cdc disposed between the converter 22 and the inverter 24, a voltage sensor 306 that detects a stator winding voltage tIvst2II, a current sensor 307 that detects a stator winding current °ist2", a voltage sensor 308 that detects a terminal-to-terminal voltage of the smoothing capacitor 32cdc, and a current sensor 309 that detects a power grid output current "ig2". Output signals from these voltage sensors and current sensors, as with those of the power converter 31, are input to the power converter controller 2000. Ends of the inverters 23 and 24 that lead to the power grid 2 are electrically connected to each other, and after being connected to each other, these inverter ends connect to the power grid 2. The voltage "vg" at the point of interconnection to the power grid 2 is measured by a voltage sensor 305 that detects the interconnection-point voltage. To enable the power converter 32 to receive desired power from the stator winding 10013 of the generator 101 and transmit the power to the power grid 2, the power converter controller 2000 calculates a value of a gate signal Gate2 which is a control signal for the converter 22 and the inverter 24, and outputs the calculated gate signal level to the power converter 32. More specifically, the converter 22 is caused to output a voltage that is the same in frequency as, and lagging in phase behind, the voltage "vst2" of the stator winding 10013, and thus in such a way that active power will be supplied from the stator winding 10013 to the power converter 32 and the smoothing capacitor 32cdc will have its voltage "vdc2" reaching a predetermined threshold level, the inverter 24 is caused to output a voltage that is leading in phase relative to the interconnection-point voltage "vg" of the power grid 2. The active power obtained from the stator winding 10013 will be consequently transmitted to the power grid 2.

[0026] Main circuit composition and principles of operation of the converter 21 and the inverter 23 are described below using Fig. 3. As described above, the power converters 31, 32 in the present embodiment are of the same circuit composition, so the converter and inverter in each of the power converters 31, 32 also have substantially the same circuit composition. Hence, although main circuit composition and principles of operation of the converter 22 and the inverter 24 have their illustration and description omitted herein, the main circuit composition and the principles of operation are substantially the same as those of the converter 21 and the inverter 23.

[00271 The composition of the converter 21 and inverter 23 in the present embodiment is described below taking an IGBT converter of a six-arm configuration as an example. IGBT elements 21m to 21r, 23m to 23r constitute the respective arms of the converter 21 and the inverter 23. A gate driving signal is input from the power converter controller 2000 to a gate that is a control electrode of each IGBT element 21m-21r, 23m-23r. When the gate driving signal has a level of 0, the IGET element is off, and when the gate driving signal has a level of 1, the IGBT element is on.

[0028] When switching of each IGBT element is accomplished by applying a pulsewidth-modulated (PWM) gate driving signal thereto, alternating-current (AC) output power obtained from the stator winding 10012 of the generator 101 will be converted into direct-current (DC) power and then this DC power will be converted into AC power suitable for output to the power grid 2.

[0029] An output current from the stator winding 10012 of the generator 101 is determined by a difference between the generator-induced voltage and the output voltage of the converter 21, and leakage inductance of the stator winding 10012. The stator winding current is converted into DC form by the converter 21, and this direct current charges the smoothing capacitor 3lcdc.

[00301 An output current to the power grid 2 is determined by a difference between the interconnection-point grid voltage of the power grid 2 and the output voltage of the inverter 23, and impedance of a higher-harmonic filter 23fi1. The output current is a result of conversion from direct current to alternating current by switching of the inverter 23, and the inverter 23 outputs active power to the grid, thus discharging the smoothing capacitor 3lcdc.

[0031] The converter outputs a rectangular-wave voltage by the switching of an IGBT element. Since this rectangular-wave voltage could cause insulation deterioration of the generator, the converter 21 interconnects to the generator 101 via a filter 2lfil for limiting a rate of change of the voltage.

As described above, the power converter 32 has the same composition as that of the power converter 31, so that overlapping description of the power converter 32 is omitted herein.

[0032) Next, the generator 101 is described below using Figs. 4 and 5. Fig. 4 is a diagram representing a geometry and layout of the generator elements with certain discrepancies from actual relationships in geometry and layout in order to describe a radial sectional view of the generator, and the actual relationships in geometry and layout between the generator elements are close to those shown in Fig. 5.

[0033] The generator 101 includes a rotor 502 having permanent magnets, and two stators, 501 and 503, that are arranged with the rotor 502 interposed in a radial direction of the generator therebetween. The rotor 502 is mechanically connected to the shaft 14, and as the blades rotate, the rotor 502 rotates counterclockwise between the stators 501 and 503 (however, specifications that cause clockwise rotor rotation are not excluded) [00341 The stator 501 includes a plurality of magnetic pole members and a stator winding 10012 wound around the magnetic pole members. It should be interpreted that for concise description of Fig. 4, the same symbols (Ui, Vi, Wi, Ni, U2, V2, W2, or N2) assigned to the winding terminals in Fig. 4 are used to denote that the terminals are electrically connected to each other.

[0035] The stator 503 includes a plurality of magnetic pole members and a stator winding 10013 wound around the magnetic pole members. While wire connection forms of terminals U2, V2, W2, N2 are not shown, these terminals are connected in substantially the same form as that of terminals Ul, Ill, Wi, Ni.

[00361 Magnetic fluxes generated by the permanent magnets of the stator 502 link to the stator windings 10012, 10013 of both stators, 501 and 503. As the rotor 502 rotates, a voltage is induced in the stator windings 10012, iOOl3.

[00371 When a voltage that is the same in frequency as and lagging in phase behind the induced voltage is applied from the converters 21, 22 to the stator windings 10012, 10013, an active current will flow from the generator 101 through the stator windings 10012, 10013 to the converters 21, 22, thus allowing electricity to be generated. In accordance with these principles of operation, electric power can be generated in both of the stator windings 10012, 10013.

[00381

For the sake of convenience in the description of

composition of the magnetic pole members and stator windings, Fig. 4 shows a generator configuration with a reduced number of magnetic poles. For this reason, a distance from a rotational center of the generator to a surface of each magnetic pole member significantly differs between the stators 501 and 503. This difference produces a significant difference in a rate of change of the magnetic fluxes linking to the stator windings 10012, 10013, and results in a substantial difference in the voltage induced.

[00391 For a wind power generator system with a rated blade speed of nearly 20 rpm, the generator amounts to several meters in radius, for which reason, as shown in Fig. 5, an actual difference in distance from the rotational center of the generator to the surface of each magnetic pole member between the stators 501 and 503 decreases relative to the differential distance in Fig. 4, thus resulting in sizes of the stators 501 and 503 becoming substantially the same.

Hence, a generator having a certain size such as the above size becomes able, in principle, to generate substantially twice as much electricity as can a generator of the same volume that has one stator.

[0040] Operation of the wind power generator system 1 is described below.

[0041] The wind power generator system 1 causes the blades to obtain rotational energy by receiving wind, and this rotational energy rotates the rotor 502 of the generator 101 in the generator/converter section 100 via the shaft 14.

[00421 The rotor 502 includes a plurality of permanent magnets, 520 and 521 (shown in Fig. 6)1 and as the rotor 502 rotates, an AC voltage is induced in the stator windings 10012, 10013 of the generator 101..

0043.] The power converters 31, 32 output an AC voltage having a frequency equal to that of, and lagging in phase behind, the AC voltage induced in the stator windings 10012, 10013 to which the power converters 31, 32 are connected respectively. Thus the power converters 31, 32 receive active power from the generator 101. The power converters 31, 32 convert the active power into power of a frequency equal to that of the power grid 2, and transmit this power to the power grid 2.

[00441 Input torque from wind is controlled through the pitch angle control of the blades 10. The host controller 1000 controls the pitch angle so that the rotational speed of the blades 10 matches a rotational speed command value in accordance with the wind speed.

[00451 Next, the generator configuration and an abnormality detection function of the generator/converter section 100 are detailed below using Figs. 6 and 7. The generator configuration is described per Fig. 6, and the abnormality detection function is described per Fig. 7.

[00461 The power generator system of the present embodiment includes a control system having a detector to detect an.

abnormality of the power converters connected to the stators and an abnormality of the power generator system.

Upon detection of an abnormality, either the power converter in which the abnormality has been detected, or the power converter connected to the stator winding in which the abnormality has been detected serves to cut of f a current flowing through that stator winding, and the generation of power is continued with the healthy stator winding and power converter.

[0047] A method of supporting the rotor 502 and the stator 503 is described below using Fig. 6. Fig. 6 is an axial sectional view of the generator 101.

[0048] The stator 501, constructed so as to shroud the generator 101, abuts via a bearing 506 upon the shaft 14 that transmits the torque of the blades 10 to the rotor 502.

An axle 510 extending through a radial center of the stator 503 and supporting the stator 503 via a spoke is fixed at one end of the axle 510 to the stator 501. The axle 510 abuts at another end thereof upon the rotor 502 via a bearing 505. The rotor 502 is fixed at one end thereof to the shaft 14 and abuts at another end of the rotor upon the axle 510 via a bearing 504.

[00491 With the above configuration, the generator can be formed that includes the rotor 502 and stator 503 supported by the stator 501 or axle 510, respectively, either directly or indirectly via a bearing, the rotor being interposed in a radial direction between the two stators.

[0050] The axle 510 is of cylindrical construction with a cavity in it, and the stator winding 10013 is pulled out from the generator through the cavity. This construction enables the power converter 32 and the stator winding 10013 to be connected to each other. In addition, the permanent magnets 520, 521 are supported by being embedded in the rotor 502, and the generator 101 can support the permanent magnets that generate the fluxes to be linked to the stator windings. The stator windings 10012, 10013 can be fixed by being wound around the magnetic pole members of the stators 501, 503.

[0051] The generator 101 in the present embodiment includes the plurality of stators, and thus can be formed into compact construction, compared with a conventional generator having the same electric power rating.

[0052] In addition, the stator windings 10012, 10013 in the present embodiment are placed at locations spatially kept away from one another in the generator as described above, which yields an advantage in that even if overheating due to short-circuiting, insulation deterioration, or the like occurs in one stator winding, impacts upon the other stator winding are minimized and extension of a fault to the healthy stator winding can be avoided.

[0053] Next, the power converter controller 2000 is described below using Fig. 7.

[0054] The power converter controller 2000 includes: a multiplier 2100 and subtractor 2101 that decompose the generated-power command value "Pref" that has been input from the host controller 1000, into generated-power command values "Prefi" and "Pref2" for the power converters 31 and 32, respectively; a controller 2110 that calculates a value of a gate signal Gate 01 of the power converter 31 so as to control the generated power for the power converter 31 in accordance with the generated-power command value "Pref 1" obtained from the above decomposition; a controller 2111 that calculates a value of a gate signal Gate_02 of the power converter 32 so as to control the generated power for the power converter 32 in accordance with "Pref2"; an abnormality detector 2200 that conducts a computation for detecting an abnormality in the generator/converter section 100, and then outputs a signal indicating whether the abnormality has occurred; and gate signal controllers 2301, 2302 that control gate signals of the power converters 31, 32 according to the particular output signal from the abnormality detector 2200.

[00551 A method of power command distribution by the power converter controller 2000 is described below.

[0056] The generated-power command value "Pref" that has been input from the host controller 1000 is input to the multiplier 2100 and the subtractor 2101. The multiplier 2100 multiplies the generated-power command value "Pref" by a fixed value "k" satisfying a condition of Ockcl, and then outputs a result of the multiplication, k*Pref ", to the controller 2110 and the subtractor 2101.

[0057) The subtractor 2101 receives, as inputs, the generated-power command value "Pref' and the multiplication result by the multiplier 2100, and calculates a difference of the multiplication result with respect to the generated-power command value "Pref". The generated-power command value "Pref2" for the power converter 32, that is, "(1-k)*PrefP, is obtained as a result.

[0058] The fixed value "k' is a design value commensurate with a ratio of generable electric power that is derived from a thermal design of the stator windings 10012, 10013 and the power converters 31, 32. The present embodiment assumes that the fixed value k" is substantially equal to 0.5 since, as described in connection with Fig. 5, the power generated in the stator windings 10012 and 10013 is expected to be substantially of the same level between both thereof. Naturally the fixed value "k' may be changed according to an output rate, anticipated for particular

specifications.

[0059] In order that a calculated active-power value P1 that the power converter 31 receives from the stator winding 10012 will match the power command value "Pref 1" and the DC voltage "vdcl" will reach the predetermined threshold level, the controller 2110 receives, as input signals, the smoothing capacitor voltage Tlvdcln, power grid interconnection-point voltage "vg", grid output current "igl", output voltage "vstl" of the stator winding 10012, and output current rTistll! of the stator winding 10012 that are output from the respective current sensors and voltage sensors, and the power command value ITprefln, and then calculates the value of the gate signal Gate 01 of the power converter 31. The calculated active-power value P1, received from the stator winding 10012, is a value that was calculated as a product of the output voltage!Tvstlu of the stator winding 10012 and the output current "istl" of the stator winding 10012. The power value P1 is output to an adder 2102 in addition to be used for arithmetic operations within the controller 2110.

[0060] In order that a calculated active-power value P2 that the power converter 32 receives from the stator winding 10013 will match the power command value "Pref2" and the DC voltage "vdc2" will reach the predetermined threshold level, the controller 2111 receives, as input signals, the smoothing capacitor voltage "vdc2", power grid interconnection-point voltage "vg", grid output current "ig2", output voltage "vst2" of the stator winding 10013, and output current "ist2" of the stator winding 10013 that are output from the respective current sensors and voltage sensors, and the power command value "Pref2", and then calculates the gate signal Gate 02 of the power converter 32. The calculated active-power value P2, received from the stator winding 10013, is a value that was calculated as a product of the output voltage 1vst2" of the stator winding 10013 and the output current "ist2" of the stator winding 10013. The power value P2 is output to the adder 2102 in addition to be used for arithmetic operations within the controller 2111. In addition to the arithmetic operations within the controller 2110, the controller 2111 calculates a rotational speed & of the generator 101 from the output voltage "vst2" and output current "ist2" of the stator winding 10013, and outputs the calculated speed value to the host controller 1000.

[0061] The adder 2102 adds he calculated active-power values P1, P2 and outputs the total generated-power value P of the generator 101 to the host controller 1000.

[0062] The abnormality detector 2200 and the gate signal controllers 2301, 2302 are described below.

[0063] The abnormality detector 2200 acquires the output currents "isti", "ist2" of the stator windings 10012, 10013, as input signals, and outputs a gate control signal CTRL1 of the power converter 31 and a gate control signal CTRL2 of the power converter 32.

[0064] The abnormality detecting computation in the abnormality detector 2200 is described below.

[0065] If an absolute value of the output currents from the stator windings 10012 and 10013 exceeds a predetermined threshold value, the abnormality detector 2200 determines the abnormality of a stator winding or power converter to have occurred, and changes a value of the corresponding gate control signal from 1 to 0.

[0066] To be more specific, the abnormality detector 2200 includes overcurrent detection arithmetic units 2201, 2202, each of which calculates the absolute value of the stator windings output currents and performs an arithmetic operation to determine magnitude of the absolute value relative to the predetermined threshold value. The predetermined threshold value can be set to be a value greater than a rated current of the stator windings currents Histlil, "ist2", for example a value that is 1.2 times as large as the rated current. In this case, if the calculated absolute value of the stator windings output currents is found to be greater than the predetermined threshold value, then this state is detected as an abnormality such as a short circuit in either of the stator windings 10012, 10013 or an IGET element failure in either of the power converters 31, 32.

[0067] The abnormality detector 2200 outputs the gate control signal CRTL1 of the power converter 31 and the gate control signal CRTL2 of the power converter 32. The gate control signal CRTL1 is input to the gate signal controller 2301, and the gate control signal dRTL2 to the gate signal controller 2302.

[0068] The gate control signal CTRL1 is a binary signal that takes either the value of 0 in case of abnormality detection in the stator winding 10012 or the power converter 31, or the value of 1 in all other cases. If an abnormality is detected, the gate signal Gatel of the power converter 31 is set to be 0, irrespective of the value of the gate signal Gate_al, so that the power converter 31 has all its IGT elements turned off or is gate-blocked, and serves to cut off the current flowing through the stator winding 10012.

[0069] The gate control signal CTRL2 is a binary signal that takes either the value of 0 in case of abnormality detection in the stator winding 10013 or the power converter 32, or the value of 1 in all other cases. If an abnormality is detected, the gate signal Gate2 of the power converter 32 is set to be 0, irrespective of the value of the gate signal Gate_02, so that the power converter 32 has all its IGBT elements turned off, or is gate-blocked, and serves to cut off the current flowing through the stator winding 10013.

[0070] The following describes transmission of an error detection signal from the generator/converter section 100 to the host controller, and an interface for abnormality notification from the generator/converter section 100 to maintenance personnel for the wind power generator system.

[0071] The output signals CTRL1, CTRL2 from the abnormality detector 2200 are sent to an OR arithmetic unit 2303 and a display device 2700. The OR arithmetic unit 2303 conducts an OR operation between CTRL1 and C,TRL2, and outputs an error detection signal L_ERR as an arithmetic result to the host controller 1000.

[0072] As described above, if the error detection signal LERR has a value of 0, the host controller 1000 determines that the maximum blade deceleration torque value obtained from the generator/converter section 100 has decreased by nearly half (since the two stator windings are substantially of the same size and shape, where capacity differs between both windings, the blade speed is reduced at a rate depending upon a capacity ratio which the abnormal stator possesses) . After this determination, the host controller 1000 limits the pitch angle command value "c4ref" and the total generated-power command value "Pref" according to a particular result of the determination. The limitation of the pitch angle command value "tref" enables the wind-generated torque to be reduced and excessive rotation of the blades 10 to be avoided.

[0073] The display device 2700 receives CTRL1 or CTRL2 as an input, and displays a name of the power converter in which the abnormality has been detected, on a (liquid-crystal display) screen mounted outside the power converter.

In other words, the display device 2000 plays a role of switching display, depending upon the output signal from the abnormality detector 2200. More specifically, the display on the (liquid-crystal display) screen may be either conducted by highlighting in red a background of the name of the power converter in which the abnormality was detected, or replaced by activating a lamp that indicates the abnormality of the power converter. In addition, the display device 2700 conveys, by communication via a communication system 2701, the occurrence of the abnormality to a communication terminal of the wind power generator system maintenance personnel present in the distance. In this configuration, the maintenance personnel for the wind power generator system can know the occurrence of the abnormality in the generator/converter section 100 and immediately set up a repair plan.

[0074] In the present embodiment, since two stators are * arranged with a rotor interposed therebetween in the generator, and since each of the stators includes a stator winding, electricity can be generated at both radially outer and inner sections of the rotor, and this advantage improves a spatial utilization ratio of the generator and enables it to generate greater electrical energy with the same volume as that of a conventional generator. This means that the generator volume for obtaining predetermined rated power can be reduced in comparison with the volume of the conventional generator. In addition, the number of stator windings for the stators does not absolutely need to be two and can be even greater. In such a case, there will be a need to dispose a power converter for each stator winding. There will also be a need to dispose a sensor for each stator winding or power converter, in which case the sensor will detect a state of the stator winding or power converter. All other elements required will only be means for detecting an abnormality according to a particular output signal from the sensor.

[0075] Furthermore, if an abnormality is detected in the generator system with the plurality of stator windings and power converters for controlling generated power, gate-blocking the power converter in which the abnormality has been detected enables the generation of power to be continued with the healthy thtator winding and power converter.

[0076] Furthermore, arranging the plurality of stator windings at two different locations (for rotor interposition between the stator windings), that is, at the radially outer and inner sections of the rotor, enables one (healthy) stator winding to be protected from impacts of, for example, unusual heat from the other stator winding that might be suffering an abnormality. Thus the healthy stator winding can be kept free of any impacts of the abnormality. This renders the above stator-windings arrangement further suitable for raising the continuity of power generation.

[0077] Moreover, an error detection signal from the abnormality detection means is also displayed to the maintenance personnel for the wind power generator system, and this display allows formation of a state in which, while the continuity of power generation is being maintained, the maintenance personnel can perform repairs without a delay.

[0078] Besides, providing an interface so that the abnormality detection means in the generator/converter section 100 can transmit the error detection signal to the host controller enables the host controller external to the generator/converter section 100 to calculate the pitch angle command value Tref internally incorporating a decrease in the maximum value of the blade deceleration torque in the generator system, and hence, excessive blade rotation to be avoided.

Second Embodiment [0079] A second embodiment of the present invention is described below using Fig. s. while a stator windings overcurrent has been detected as an abnormality of the generator/converter section 100 in the first embodiment, the abnormality detector 2200 may, as shown in Fig. 8, include negative-phase calculating units 2203 and 2204 that calculate negative-phase components of a current, and comparators 2205 and 2206 that compare an output of at least one of the negative-phase calculating units and a second predetermined threshold value in terms of magnitude and if the output of the negative-phase calculating unit 2203 or 2204 is greater than the second predetermined threshold value, change the value of at least one of the gate control signals CTRL1, CTRL2 from 1 to 0. In this configuration, disconnection of the relevant stator winding 10012, 10013 can be detected and imparting significant torque pulsations to the generator 101 can be avoided. The second predetermined threshold value here is desirably set to nearly 10-20 percent of the rated current of the stator windings 10012, 10013 to avoid erroneous detection of an abnormality, caused by an imbalance of winding resistance or by noise, while at the same time ensuring appropriate detection of an abnormality. Substantially all other characteristics and features of the second embodiment are substantially the same as those of the first embodiment, and overlapping description of these other characteristics and features is omitted herein. The second embodiment can yield substantially the same advantageous effects as those described in the first embodiment.

Third Embodiment £00801 A third embodiment of the present invention is described below using Figs. 9 and 10. While a stator windings overcurrent or negative-phase components of a current have been detected as abnormalities in the above two embodiments, abnormality detection may be based upon an unusual increase in an in-panel temperature of an inverter or converter. In this case, the generator/converter section 100 detects the unusual increase in the in-panel temperature of an inverter or converter and gate-blocks the power converter.

[00811 Inadequate cooling of IGBT elements due to a failure in a cooling fan or the like raises a temperature of the IGET elements and the in-panel temperature. Extensive or serious damage to a module of the IGET elements, such as rupture or short-circuiting, is likely if the IGBT temperature rise exceeds an allowable level. Detecting the unusual increase in the in-panel temperature and then gate-blocking the power converter will suppress further overheating and allow continued safe operation of the generator/converter section 100.

[0082] More specifically, as shown in Fig. 9, the converters 21, 22 and the inverters 23, 24 include temperature sensors 350, 351, 352, 353, respectively, that each detect the in-panel temperature, and respective outputs Tl1, Tl2, T21, T22 from the temperature sensors are input to the power converter controller 2000. As shown in Fig. 10, the abnormality detector 2200 in the power converter controller 2000 includes temperature -discriminators 2207, 2208 and these temperature discriminators are composed to acquire Tl1, T12 as input signals, and if at least one of the two temperature sensor output values is greater than a third predetermined threshold value, gate-block the power converter 31 by changing the value of the gate control signal CTRL1 from 1 to 0. The temperature discriminators are also composed so that if the temperature sensor output value T21 or T22 is greater than the third predetermined threshold value, the relevant temperature discriminator gate-blocks the power converter 32 by changing the value of the gate control signal CTRLI2 from 1 to 0. such circuit composition of the abnormality detector 2200 enables damage to the power converters 31, 32 due to overheating to be avoided. In this case, the temperature sensors may be placed directly close to the IGBT elements to detect an unusual increase in the temperature of the IGBT elements, instead of the unusual increase in the in-panel temperature.

Substantially all other characteristics and features of the third embodiment are substantially the same as those of the first embodiment, and overlapping description of these other characteristics and features is omitted herein. The third embodiment can yield substantially the same advantageous effects as those described in the above embodiments.

Fourth Embodiment [0083] A fourth embodiment of the present invention is described below using Fig. 11. Besides the abnormality detection described in the above embodiments, the generator/converter section 100 may detect an unusual increase in the voltage of a smoothing capacitor. After the detection of the unusual increase, the relevant power converter is gate-blocked. If a cable connecting the inverter 23 or 24 to the power grid 2 becomes disconnected, the particular inverter cannot transmit its own rated electric power to the power grid 2, with the result that the power that has been input from the converter to which the inverter is connected is likely to overcharge the capacitor. The capacitor overcharge could cause damage to the capacitor, damage to the IGBT elements, or any other extensive or serious damage.

[0084] Accordingly, detecting an unusual increase in the voltage of a smoothing capacitor and then gate-blocking the corresponding power converter enables further charging of the smoothing capacitor to be avoided and hence, stable operation of the generator/converter section 100 to be achieved. More specifically, as shown in Fig. 11, the abnormality detector 2200 includes DC overvoltage calculating units 2209, 2210 that each acquire the smoothing capacitor voltages vdcl, vdc2 as inputs, and detect a DC overvoltage of the power converters 31, 32 by comparing at least one of the smoothing capacitor voltages with a fourth predetermined threshold value in terms of magnitude. At least one of the DC overvoltage calculating units 2209, 2210 changes the value of the gate control signal CTRL1 from 1 to 0 if the value of the smoothing capacitor voltage "vdcl"is greater than the fourth predetermined threshold value, and changes the value of the gate control signal CTRL2 from 1 to 0 if the value of the smoothing capacitor voltage "vdc2" is greater than the fourth predetermined threshold value. With these elements, the power converters 31, 32 can be protected from damage due to DC overcharge.

[0085]

The disclosure in the description of the first to

fourth embodiments can be used independently for each of the embodiments or used in combination of the embodiments.

Since each embodiment is based upon different data measurements and detects a different event as an abnormality, the combination of each enables abnormality detection for various unusual patterns, and hence, enhancement of abnormality detection accuracy.

Fifth Embodiment [00861 A fifth embodiment of the present invention is described below using Figs. 12 and 13. while a permanent-magnet synchronous generator has been described as the generator 101 in each of the above embodiments, an electromagnetic generator may instead be used as the generator 101. More specifically, as shown in Fig. 12, if a voltage of the power grid 2 is stepped down with a transformer 55, rectified with a diode rectifier 54, and then an excitation current is supplied to the rotor winding 10020 via brushes 52, 53 and brush rings 50, 51, linked magnetic fluxes can be generated in the stator windings 10012, 10013, as in permanent magnets.

[0087] Additionally as shown in Fig. 13, the generator 101 may include a coil 60 placed in the stator 501 and energized by the power grid 2, a coil 61 placed in the rotor 502 and adapted to obtain AC power from the power grid 2 in non-contact form through linking of AC magnetic fluxes generated in the coil 60, and a diode rectifier 54 placed in the rotor 502 in order to rectify an AC voltage induced by the coil El. The generator 101 may be further composed to supply an excitation current to the rotor winding 10020. This configuration of the generator reduces a maintenance load of the generator. Briefly, with this configuration, an excitation current to an electromagnetic generator can be obtained from a current induced between the non-contact coils 60, 61, so it becomes unnecessary to obtain the excitation current by making (direct) contact through brushes. Hence, brushless generator construction can be provided.

[0088] As in the present embodiment, a generator high in output power density can be constructed even without expensive permanent magnets, and continued generation of power with a healthy stator winding and power converter can be achieved even in case of a failure in the generator system. Additionally in the configuration of Fig. 13, the brushes that require maintenance can be deleted, which, even if an electromagnetic generator is used, eliminates the necessity for the maintenance for brush replacement, thus allowing provision of the wind power generator system improved in the continuity of power generation.

[0089] While an example of disposing an inverter and a converter in each power converter has been described in each of the above embodiments, an inverter and capacitor that may be disposed at the power grid side can be shared as described later herein. That is to say, although each power converter needs to include an inverter and a converter, the power converter does not always need to have the inverter independently.

Sixth Embodiment [0090] A sixth embodiment of the present invention is described below using Figs. 14 and 15. An example of disposing an inverter and a converter in each power converter has been described in each of the above embodiments. However, as shown in Fig. 14, the power converters 31, 32 may be configured to share a DC circuit section and the generator/converter section 100 may be configured to transmit generated electric power to the power grid 2 via a single inverter. In this case, since the DC circuits are unified in specifications, the DC circuit voltages become equal between the converters 21 and 22. The equality of the DC circuit voltages renders inverter control by the controller 2111 unnecessary, whereby the controller 2110 controls the inverter 23 on the basis of the output value of the DC voltage sensor 303 and consequently the generated electric power obtained from the generator 101 can be transmitted to the power grid 2. In addition, the inverter 24 can be dispensed with, which makes unnecessary the current sensor that detects the AC output current of the inverter 24. Hence, this circuit composition of the present embodiment enables deletion of the smoothing capacitor 32cdc from the power converter 32, hence, deletion of the voltage sensor 308 for detecting the voltage of the smoothing capacitor 32cdc, and deletion of the current sensor 309 for detecting the grid current.

[0091] To achieve the configuration shown in Fig. 14, it becomes necessary to configure the power converter controller 2000 so that the controller 2110 outputs Gate 021, a gate signal for driving the gate signal of the converter 21, and Gate 023, a gate signal for driving the gate signal of the converter 23, and so that the controller 2111 outputs Gate 022, a gate signal for driving the gate signal of the converter 22, and controls only the gate signals of the converters 21, 22 according to a particular output of the abnormality detector 2200. The configuration where the controller 2000 can only turn off the IGBTs of the converters according to the particular output of the abnormality detector 2200 is a significant difference from the configurations of the above embodiments, gate blocking in the configuration where the DC circuit section is shared corresponds to controlling the inverter to leave its IGBT turned on and only the converters to turn off all their IGBTs. In this case, if an error is detected, either. the power converter in which the abnormality has been detected, or the power converter connected to the stator winding in which the abnormality has been detected will also serve to cut off the current flowing through that stator winding, and the generation of power will be continued with the healthy stator winding and power converter.

[0092] In accordance with the present embodiment, the voltage sensor for detecting the smoothing capacitor voltage, and the current sensor for detecting the grid current can be deleted and while achieving the correspondingly simplified configuration, abnormality detection can be conducted in substantially the satne way as that of the above embodiments.

Seventh Embodiment [0093] A seventh embodiment of the present invention is described below using Figs. 16 to 19. In the present embodiment, the converters 21, 22 in the generator/converter section 100 are replaced by three-level converters 125, 126. In addition, a stator winding 20013 of a generator 201 is disposed with a shift of nearly 60 degrees in electrical angle with respect to a stator winding 20012.

[00941 The three-level converters, compared with a two-level converter, can output a waveform closer to a sinusoidal waveform, thus reduces dv/dt in an AC output voltage, and hence mitigate stator windings requirements relating to electrical insulation performance. When a power factor in the generator terminals js other than 1. on the other hand, since power fluctuations that are three times as large as the frequency of the AC output voltage arise from a neutral point in the DC circuit, capacitors of a large capacity need *to be mounted so that capacitor voltages of the converters 125, 126 and an inverter 123 fall within a withstand voltage range of the semiconductor switching elements.

10095J In contrast to this, in the present embodiment, the stator windings 20012, 20013 are arranged for a shift of 60 degrees in electrical angle, this layout offsets the voltage fluctuations that change the DC circuit neutral point, and the voltage fluctuations at the DC neutral point are reduced, which in turn enables reduction in the capacitance that needs to be mounted in a power converter 131.

[00961 Further details of the above are described below using Figs. 16 to 19.

[0097] In the power converter of the present embodiment, as shown in Fig. 16, the converters connected to the generator 201 are the three-level converters 125, 126, DC circuits of which are connected to each other.

[0098] In the present embodiment, the converters 125 and 126 are also equal in main circuit composition, and only the composition of the converter 125 is therefore described here using Fig. 17. Clearly, the converters 125 and 126 do not always need to have equal main circuit composition and each may take different composition. The number of kinds of parts needed can be reduced by using substantially the same parts.

[0099] The converter 125 includes six IGET elements, and two diodes connected to the DC nep.tral point, in one arm.

Turn-on/off of the IGET elements enables potentials of three levels to be output to a filter l2lfil: a positive potential of a smoothing capacitor l3ldcp, a DC neutral-point potential, and a negative potential of a smoothing capacitor l3ldcn.

[0100] When the converter 125 outputs the AC voltage to the filter l2lfil, a difference in discharge power occurs between the smoothing capacitors l3ldcp, l3ldcn, resulting in pulsations.

10101] Fig. 18 shows a configuration of the generator 201 in the present embodiment. Compared with the generator 101 described per Fig. 4, the generator 201 has its stator 603 shifted through an electrical angle of 60 degrees in phase relative to a stator 601. The stator windings 20012, 20013 are shifted through 60 degrees in electrical angle, which causes both an output voltage and output current of the converters 125 and 126 to shift through 60 degrees in phase, and hence, electric power pulsations also to shift through degrees in phase on a fundamental-wave equivalent basis.

The electrical angle of 60 degrees of the fundamental wave is equivalent to 180 degrees, three times as large as that of the pulsating power having three times the frequency of the fundamental wave. Hence the above pulsations can be offset by shifting the stator windings 20012, 20013 of the generator 201 by 60 degrees in phase.

[01021 Fig. 19 shows the way the pulsations are offset. As shown in the figure, phases of the pulsating power Pdcnl and pulsating power Pdcn2 flowing from the converter 125 into the DC neutral point shift through 180 degrees, which inverts polarity and thus causes the inf lows of the two sets of pulsating power into the neutral point between the capacitors l3lpdcp, l3ldcn to be added to one another and then offset.

[0103] In accordance with the present embodiment, a generator high in output power density can be configured that provides, even in case of a power generator system failure, the power generation of high continuity that uses a healthy statbr winding and power converter. In addition, a generator/converter section 200 employs a three-level converter arrangement, which facilitates windings insulation design for the generator 201. Furthermore, since the phase of the stator windings 20012, 20013 in the generator 201 is shifted through 60 degrees to enable the offsetting of the pulsating power flowing from the three-level converters 125, 126 into the DC neutral point, and the power converter 31 to be constructed with capacitors of a small capacity.

[0104] While the embodiments described above apply to a wind power generator system, not all sections, except for the characteristic blade-pitch angle control and others of the wind power generator system, have their application limited to the wind power generator system.

Description of Reference Numbers

[0105] 1: Wind power generator system 2: Power grid 10: Blade 11: Hub 14: shaft 31, 32: Power converters 21, 22, 25, 26: Converters 23, 24: Inverters 100: Generator/converter section 101: Generator 501, 503: Stators 502: Rotor 301, 303, 305, 306, 308: Voltage sensors 302, 307, 309; Current sensors 1000: Host controller 2000: Power converter controller 2200: Error detector 10012, 10013: Stator windings 10020: Rotor winding

Claims

CLAIMS1. An electric power generator system, comprising: an electric generator including a rotor, stators facing the rotor, and a plurality of stator windings disposed in the stators; electric power converters each including an inverter disposed at a power grid side, a converter disposed at the generator side, and a capacitor disposed between the inverter and the converter, the power converter being provided for each of the stator windings; sensors each provided for one of the stator windings or power converters, each sensor being adapted to detect a state of the stator windings or power converters; and means that detects an abnormality of the stator windings or power converters according to a particular output of the sensors, wherein: the abnormality detection means is further configured to output a signal that denotes presence/absence of an abnormality for each of the stator windings or power converters; and if any information indicating existence of an abnormality is outut from the abnormality detection means, the power converter in which abnormality was detected or the power converter provided for the stator winding in which abnormality was detected serves to cut off a current f lowing through the stator winding.
2. The power generator system according to claim 1, further comprising: blades that rotate by receiving wind; a shaft that rotates as the blades rotate; and means that controls a pitch angle of the blades, wherein: the rotor rotates as the shaft rotates; and if any information indicating existence of an abnormality is output from the abnormality detection means, the pitch angle control means controls the pitch angle of the blades so as to reduce a swept area.
3. The power generator system according to claim 1 or 2, wherein: the stators have a structure of two separate stators arranged with the rotor interposed between the stators, each stators being provided with one of the stator windings.
4. The power generator system according to claim 3, wherein: the inverter and capacitor in each of the power converters are shared between the power converters, and the converter is a three-level converter; and a voltage induced in the stator windings each disposed for one of the two stators becomes equal between the stator windings, the stator windings being arranged so as to shift from each other through 60 degrees in electrical angle.
5. The power generator system according to any one of claims 1 to 4, wherein: the abnormality detection nieans includes overcurrent detection means for each of the stator windings; the sensor measures a value of the current flowing through the stator winding and outputs the measured current value to the overcurrent detection means; and the overcurrent detection means compares the measured current value with a predetermined threshold value, and if the measured current value is in excess of the predetermined threshold value, outputs information to indicate that an abnormality is occurring.
6. The power generator system according to any one of claims 1 to 4, wherein: the abnormality detection means includes a negative-phase calculating unit that calculates a negative-phase component value of the current, and means that compares, with respect to a predetermined threshold value, the negative-phase component value calculated by the negative-phase calculating unit; the sensor measures a value of the current flowing through the stator winding and outputs the measured current value to the negative-phase calculating unit; and after the comparison between the negative-phase component value calculated by the negative-phase calculating unit and the predetermined threshold value, if the negative-phase component value is in excess of the predetermined threshold value, the comparison means outputs information to indicate that an abnormality is occurring.
7. The power generator system according to any one of claims 1 to 4, wherein: the abnormality detection means includes a temperature discriminator for each of the stator windings; the sensor measures a temperature of the inverter or the converter and outputs the measured temperature to the temperature discriminator; and the temperature discriminator compares the measured temperature with a predetermined threshold value, and if the measured temperature is in excess of the predetermined threshold value, outputs information to indicate that an abnormality is occurring.
8. The power generator system according to any one of claims 1 to 4, wherein: the abnormality detection means includes an overvoltage calculating unit for each of the stator windings; the sensor measures a voltage of the capacitor and outputs the measured voitage to the overvoltage calculating unit; and the overvoltage calculating unit compares the measured voltage with a predetermined threshold value, and if the measured voltage is in excess of the predetermined threshold value, outputs information to indicate that an abnormality is occurring.
9. The power generator system according to any one of claims 1 to 8, further comprising: a first coil placed in one of the stators and energized by a power grid; a second coil placed in the rotor and adapted to obtain alternating-current power from the power grid in non-contact form through linking of alternating-current magnetic fluxes generated in the first coil; a diode rectifier placed in the rotor in order to rectify an alternating-current voltage induced in the second coil; and a rotor winding disposed in the rotor and receiving a supply of an excitation current from the diode rectifier, wherein: a magnetic flux that the excitation current generates while flowing through the rotor winding varies with time as the rotor rotates, and thus the generator system generates an alternating current in the stator windings.
10. The power generator system according to any one of claims 1 to 3 or claims 5 to 9, wherein the inverter and capacitor in each of the power converters are shared between the power converters.
11. The power generator system according to any one of claims 1 to 10, further comprising: a display device for displaying whether an abnormality is occurring; and a communication system connected to the display device, wherein: the abnormality detection means further outputs information to the display device to indicate whether the abnormality is occurring; the display device switches display according to an particular output of the abnormality detection means; and when the abnormality detection means detects the abnormality, the communication system conveys, by communication, the occurrence of the abnormality to a communication terminal external to the wind power generator system.