JP2015070781A - Wind power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve such a problem that, in a wind power generation system comprising a windmill, a permanent magnet synchronous power generator converting a rotation energy of the windmill into an electric energy via a rotor and a stator, and a power converter for supplying the generated power to a power supply system, vibration is generated by a cogging torque caused by change in gap magnetic flux density between a permanent magnet of the rotor of the power generator and a stator iron core, which may cause damages at a bearing part and the like of the windmill.SOLUTION: A wind power generation system is provided that includes cogging torque estimation means 100C. By using a value obtained by subtracting a cogging torque estimation value τcalculated by the estimation means 100C from an original torque command value τof a power generator as a final torque command value τ, a power converter connected to the power generator is controlled. The cogging torque estimation means 100C estimates a cogging torque by combining the plurality of even-numbered harmonic components that are respectively calculated by using an induction voltage angular frequency of the power generator, an order setting value of an even-numbered harmonic wave of a basic frequency, and an amplitude component setting value of the even-numbered harmonic wave.

Description

  The present invention relates to a wind power generation system that suppresses torque pulsations of a permanent magnet synchronous generator connected to a wind turbine.

FIG. 5 is a schematic configuration diagram of a wind power generation system including a windmill, a permanent magnet synchronous generator, and a power converter.
The windmill 1 is of a propeller type or vertical type (Darius type or the like) and converts wind received by the blades into rotational energy. The wind turbine 1 is directly connected to a rotor composed of permanent magnets of a permanent magnet synchronous generator (hereinafter also simply referred to as a generator) 2, and an alternating current output from an armature (stator) coil of the generator 2. The voltage is rectified to a DC voltage by the converter device 3 and then converted to an AC voltage by the converter device 4 via the smoothing capacitor 7. This AC voltage is supplied to the power supply system via an ACL (AC reactor) 5 and a harmonic suppression filter circuit 6.
In addition, 8 is a control device, and 9 and 10 are control circuits for controlling the semiconductor switching elements of the converter devices 3 and 4.

Here, in the permanent magnet synchronous generator 2, two types of torque pulsation components, cogging torque and torque ripple, exist on the operating principle.
The cogging torque is generated by a change in the gap magnetic flux density caused by the positional relationship between the rotor magnet of the permanent magnet synchronous generator and the stator core composed of slots and teeth.

FIG. 6 shows the positional relationship between the stator core and the magnet when the length of the magnet along the rotation direction is an integral multiple of the slot pitch, for example, twice, and the average magnetic flux density of the gap between the two. Yes.
Since the rotor is rotated to move the magnet is positioned M ₁ to M _2, the positional relationship between the stator core and the magnet is changed, the length of the magnet is an integer multiple of the slot pitch, dashed ellipse The increase in area and the decrease in the area surrounded by are equal. For this reason, there is no change in the magnetic flux and magnetic energy in the ranges B ₁ and B ₂ before and after the rotation, and no cogging torque is generated.

On the other hand, FIG. 7 shows the positional relationship between the stator core and the magnet and the average magnetic flux density of the air gap when the length of the magnet is not an integral multiple of the slot pitch, for example, 2.2 times. Yes.
When the rotor rotates and the magnet moves from position M ₁ to M ₂ and the positional relationship between the stator core and the magnet changes, the length of the magnet is not an integral multiple of the slot pitch, so it is surrounded by a dashed ellipse. The increase in area and the decrease in the area are not equal. For this reason, the magnetic flux and magnetic energy in the ranges B ₁ and B ₂ before and after the rotation change, and a cogging torque is generated.

On the other hand, the torque ripple is a torque pulsation component generated by the harmonic component of the gap magnetic flux density and the load current.
When a harmonic component exists in the gap magnetic flux density, a harmonic component appears in the phase voltage in accordance with the harmonic component. For example, when the waveform of the gap magnetic flux density is a trapezoidal wave and the phase voltage includes the fifth harmonic component and the seventh harmonic component, even if the current is a sine wave, 6 times the pulsation component. This pulsation component corresponds to torque ripple (so-called 6f torque ripple), and causes vibration and noise of the generator.

In a wind power generation system, the cogging torque and torque ripple of the permanent magnet synchronous generator increase the starting torque of the windmill, which may interfere with the rotation of the windmill during light winds. It was.
For this reason, for example, Patent Document 1 discloses a startup of a wind turbine in which the operation of the power converter generates a torque that cancels the cogging torque in the armature winding of the permanent magnet synchronous generator, thereby improving the startup characteristics under a slight wind. An assist control device is described.

FIG. 8 is a block diagram of the prior art described in Patent Document 1, and FIG. 9 is a flowchart showing its operation.
In FIG. 8, 31 is a windmill, 32 is a permanent magnet synchronous generator, 33 is a converter circuit, 34 is a smoothing capacitor, 35 is a step-down chopper circuit, 36 is a switching element, 37 is a reactor, 38 is a capacitor, 39 is a storage battery, 40 Is the load. A rotor sensor 51 is installed in the generator 32, and an output signal thereof is input to the magnetic pole position detection circuit 52 and the rotation speed detection circuit 53 in the activation assist control device 50. The magnetic pole position and the rotational speed detected by these detection circuits 52 and 53 are input to the start assist control circuit 54, and the rotational speed is also input to the power generation control circuit 56. The output of the start assist control circuit 54 is input to the PWM gate driver 55 to generate a gate signal for the switching element of the converter circuit 33, and the output of the power generation control circuit 56 is input to the PWM gate driver 57 to be included in the step-down chopper circuit 35. A gate signal for the switching element 36 is generated.

The operation of this prior art will be described with reference to FIG. 9. First, the start assist control circuit 54 determines whether or not the windmill is stopped based on the rotational speed N of the windmill 31 (S101). When stopping of the wind turbine 31 as an activation assist mode (S101Yes, S102), executes the start assist control operation when the wind turbine 31 even after the lapse of a predetermined time _{T 0} is stopped (S103Yes, S104). The start assist control operation is an operation in which an AC voltage is applied to the armature winding of the generator 32 by PWM control of the converter circuit 33 using the storage battery 39 as a power source.
In this control operation, phase control is performed to cancel the cogging torque based on the detected magnetic pole position value, and the starting torque of the generator 32 is reduced. In this state, when the self-starting wind speed is applied to the wind turbine 31 and the rotation speed becomes N ₁ or more, the start assist control is turned off, and the operation mode is shifted to the power generation operation mode (S105 Yes, S107, S101 No, S108).
Also start at a predetermined windless state where the rotation speed _{N 1} can not be obtained even when the assist control operation a predetermined time _{T 1} continues, starting assist control is turned off (S105No, S106Yes, S107).

When the windmill 31 is rotated by wind power, the operation mode is set (S101 No, S108), and the converter circuit 33 is operated as a rectifier circuit by turning off all the gates. In this case, when the rotational speed N is equal to or higher than the rotational speed (power generation start rotational speed) N _{2 at} which power generation output is possible, a command corresponding to the rotational speed is given from the PWM gate driver 57 to the switching element 36 of the step-down chopper circuit 35 and PWM. Control is performed and a power generation control operation is performed (S109 Yes, S110). Thereby, the generated current of the generator 32 is supplied to the storage battery 39 or the load 40.
Thereafter the rotational speed N falls below _{N 2,} the power generation control off and become (S109No, S111), further When the wind speed is lowered windmill 31 is stopped naturally, the process proceeds to again start assist mode (S101Yes, S102).

Japanese Patent No. 4236969 (paragraphs [0023] to [0054], FIGS. 1 to 3 etc.)

As described above, in Patent Document 1, a torque that cancels the cogging torque is generated by the startup assist control operation during a period in which the rotational speed of the generator 32 is less than N ₁ after startup. However, since the start assist control is turned off when the rotational speed of the generator 32 becomes N ₁ or more, there is no effect on the torque pulsation component generated during steady rotation.
For this reason, the generator 32 vibrates due to the torque pulsation component, and in the worst case, there is a problem that the wind turbine tower is vibrated and damages the bearing portion and the like. It was a cause of health problems.

  Therefore, the problem to be solved by the present invention is to suppress the vibration and noise of the generator by giving a torque command value so as to cancel the torque pulsation component not only at the time of starting the permanent magnet synchronous generator but also at the time of steady rotation. Is to provide a wind power generation system.

In order to solve the above-mentioned problem, the invention according to claim 1 includes a windmill, a permanent magnet synchronous generator that converts rotational energy of the windmill into electric energy via a rotor and a stator, and generated power of the generator. A power converter for supplying the power to the power system, and the cogging torque generated by the change in the magnetic flux density of the gap between the rotor magnet and the stator core is estimated by the first estimating means, In the wind power generation system that controls the power converter according to a torque command value that cancels the cogging torque estimated by the first estimating means,
The first estimating means includes a plurality of values calculated using the angular frequency of the induced voltage of the generator, the order setting value of the even harmonic of the fundamental frequency, and the amplitude component setting value of the even harmonic. The cogging torque is estimated by synthesizing even harmonic components.

According to a second aspect of the present invention, there is provided a windmill, a permanent magnet synchronous generator that converts rotational energy of the windmill into electrical energy through a rotor and a stator, and supply of power generated by the generator to a power system. A power converter, and estimating a torque ripple generated by a harmonic component of a magnetic flux density in a gap between the permanent magnet of the rotor and the stator core and a load current by a second estimating means, In the wind power generation system that controls the power converter according to a torque command value that cancels out the torque ripple estimated by the estimating means of 2,
The second estimating means uses the cosine wave signal with respect to a value six times the induced voltage angular frequency of the generator and the amplitudes of the fifth harmonic component and the seventh harmonic component of the induced voltage. The torque ripple is estimated.

  As described in claim 3, by using both the first estimating means in claim 1 and the second estimating means in claim 2, both cogging torque and torque ripple can be suppressed.

According to the present invention, the cogging torque and torque ripple generated from the permanent magnet synchronous generator are estimated, and the torque pulsation of the generator is generated by controlling the power converter by generating a torque command value that cancels these estimated values. Can be suppressed. Thereby, the vibration of the generator is reduced, and it is possible to prevent damage to the bearing portion and the occurrence of noise due to the vibration of the wind turbine tower.
In addition, the calculation of the torque pulsation component in the present invention can be realized by software, and no dedicated hardware is required, so that there is no possibility of increasing the size of the apparatus.

It is a block diagram of the principal part of 1st Embodiment of this invention. It is a wave form diagram which shows an example of the U phase induced voltage of a generator, the even harmonic component of cogging torque, and a cogging torque synthetic value in 1st Embodiment of this invention. It is a block diagram of the principal part of 2nd Embodiment of this invention. It is a block diagram of the principal part of 3rd Embodiment of this invention. It is a schematic block diagram of a wind power generation system. It is explanatory drawing of the generation principle of a cogging torque. It is explanatory drawing of the generation principle of a cogging torque. It is a block diagram of the prior art described in patent document 1. FIG. It is a flowchart which shows the operation | movement of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram showing a main part of the first embodiment, and is a block diagram for generating a final torque command value for canceling the cogging torque of the permanent magnet synchronous generator. The final torque command value is used, for example, in the control circuit 9 on the converter device 3 side in FIG.

In FIG. 1, a generator torque pattern 11 is a torque pattern corresponding to the rotational speed of the permanent magnet synchronous generator, and outputs a torque command value τ _g to be output as a wind power generation system. As described above, since the cogging torque is generated by the change in the gap magnetic flux density between the permanent magnet synchronous generator magnet and the stator core composed of the slots and the teeth, the cogging torque is a fundamental frequency of the generator induced voltage. The waveform is a composite of even harmonic components. Actually, a plurality of waveforms having different orders of magnitude and phase are synthesized. Considering even harmonics up to the sixth order, the second harmonic component, the fourth harmonic component of the cogging torque, The sixth harmonic component is represented by the following Equation 2, Equation 3, and Equation 4, respectively, and these are synthesized as Equation 5.
[Formula 2]
τ _c2 = A ₂ sin (2ωt + φ ₂ )
[Formula 3]
τ _c4 = A ₄ sin (4ωt + φ ₄ )
[Formula 4]
τ _c6 = A ₆ sin (6ωt + φ ₆ )
[Formula 5]
τ _c = τ _c2 + τ _c4 + τ _c6

In Equations 2 to 5,
τ _c : Cogging torque composite value [N · m]
τ _c2 : second harmonic component of cogging torque [N · m]
τ _c4 : fourth harmonic component of cogging torque [N · m]
τ _c6 : sixth harmonic component of cogging torque [N · m]
A ₂ , A ₄ , A ₆ : Amplitude of each even harmonic component [N · m]
ω: angular frequency of the induced voltage [rad / s]
φ ₂ , φ ₄ , φ ₆ : phase of each even harmonic component [rad / s]
It is.

In FIG. 1, a cogging torque estimation means 100C as a first estimation means is a multiplication means 12 for multiplying the induced voltage angular frequency ω of the permanent magnet synchronous generator and the orders 2, 4 and 6 of even harmonic components, respectively. The addition means 13 for adding the phases φ ₂ , φ ₄ , φ ₆ of the even harmonic components to the multiplication result, and the addition result X (addition results X ₂ , X ₄ , X for each even harmonic component) ₆ ) is input and outputs a corresponding sine wave signal sinX (sinX ₂ , sinX ₄ , sinX ₆ ) and an even number of sine wave signals sinX (sinX ₂ , sinX ₄ , sinX ₆ ). a multiplication means 15 for multiplying the amplitude a ₂ of the wave _components, a _4, a _6, respectively, and synthesizing means 16 for calculating the cogging torque estimate tau _c by combining the operation result of each even harmonic components, the Eteiru.
The orders 2, 4, 6, the phases φ ₂ , φ ₄ , φ ₆ and the amplitudes A ₂ , A ₄ , A ₆ are stored in the memory as correction parameters Q for calculating the cogging torque estimated value τ _c. ing.

The cogging torque estimating means 100C calculates mathematical formulas 2 to 5 by the above means 12 to 16, and subtracting the cogging torque estimated value τ _c obtained as a result from the torque command value τ _g by the subtracting means 17, A final torque command value τ ^* that cancels the cogging torque generated by the generator is obtained. Based on this final torque command value τ ^* , for example, the control circuit 9 of FIG. 5 controls the generator 2 via the converter device 3 so that the cogging torque can be canceled.
FIG. 2 is a waveform diagram showing an example of the U-phase induced voltage of the generator, the second harmonic component, the fourth harmonic component, the sixth harmonic component, and the combined value (cogging torque estimated value) of the cogging torque. It is.

Next, FIG. 3 is a block diagram showing a main part of the second embodiment, and is a block diagram for generating a final torque command value for canceling the torque ripple of the permanent magnet synchronous generator.
As explained by Equation 1, when the waveform of the gap magnetic flux density is a trapezoidal wave and the phase voltage includes the fifth harmonic component and the seventh harmonic component, even if the current is a sine wave, the power P is fundamental. A pulsation component of 6 times the frequency is generated, and this pulsation component becomes torque ripple. Therefore, if the induced voltage of the generator can be analyzed to obtain the fifth harmonic component and the seventh harmonic component in advance, the torque ripple τ _{r of the} generator can be estimated.

In FIG. 3, the torque ripple estimation means 100R as the second estimation means is configured based on the mathematical formula 1. The multiplication means 18 for multiplying the induced voltage angular frequency ω by 6 and the multiplication result Y are input to receive the cosine wave. a cosine wave table 19 outputting the signal COZY, and multiplying means 20, 21 for multiplying the amplitude _{V 5} of the fifth harmonic component of the induced voltage in the cosine wave signal COZY, the amplitude _{V 7} of the seventh harmonic components, respectively, which Adding means 22 for calculating a torque ripple estimated value τ _r as a pulsation component of 6 times the fundamental frequency by adding the multiplication results of the multiplication means 20 and 21.
By subtracting the torque ripple estimated value τ _r thus determined from the torque command value τ _g by the subtracting means 23, a final torque command value τ ^* that cancels the torque ripple generated by the generator is obtained. Based on the final torque command value τ ^* , for example, the control circuit 9 in FIG. 5 controls the generator 2 via the converter device 3, thereby canceling out the torque ripple.

FIG. 4 is a block diagram showing the main part of the third embodiment of the present invention.
In this embodiment, the cogging torque estimated value τ _c obtained by the cogging torque estimating means 100C according to the first embodiment is subtracted from the torque command value τ _g by the subtracting means 17, and the result τ _g ′ is used to obtain the second embodiment. Thus, the final torque command value τ ^* is obtained by subtracting the estimated torque ripple value τ _r obtained by the torque ripple estimating means 100R by the subtracting means 23.
According to this embodiment, it is possible to further improve the function of suppressing torque pulsation by canceling both the cogging torque and the torque ripple of the generator.

1: Windmill 2: Permanent magnet synchronous generator 3, 4: Converter device 5: ACL
6: Filter circuit 7: Smoothing capacitor 8: Control device 9, 10: Control circuit 11: Generator torque pattern 12, 15, 18, 20, 21: Multiplication means 13, 22: Addition means 14: Sine wave table 16: Synthesis Means 17, 23: Subtraction means 19: Cosine wave table 100C: Cogging torque estimation means 100R: Torque ripple estimation means Q: Correction parameter

Claims (3)

A windmill, a permanent magnet synchronous generator that converts rotational energy of the windmill into electrical energy via a rotor and a stator, and a power converter for supplying power generated by the generator to a power supply system. The first estimation means estimates the cogging torque generated by the change in the magnetic flux density of the air gap between the rotor magnet and the stator core, and cancels the cogging torque estimated by the first estimation means In a wind power generation system that controls the power converter according to a command value,
The first estimating means includes a plurality of even numbers calculated using the induced voltage angular frequency of the generator, the order setting value of the even harmonic of the fundamental frequency, and the amplitude component setting value of the even harmonic. A wind power generation system characterized in that the cogging torque is estimated by synthesizing harmonic components. A windmill, a permanent magnet synchronous generator that converts rotational energy of the windmill into electrical energy via a rotor and a stator, and a power converter for supplying power generated by the generator to a power supply system. The torque ripple generated by the harmonic component of the magnetic flux density of the air gap between the permanent magnet of the rotor and the stator core and the load current is estimated by the second estimating means, and the torque ripple estimated by the second estimating means In the wind power generation system that controls the power converter according to the torque command value that cancels
The second estimating means uses the cosine wave signal with respect to a value six times the induced voltage angular frequency of the generator and the amplitudes of the fifth harmonic component and the seventh harmonic component of the induced voltage. A wind power generation system characterized by estimating torque ripple.   The power converter according to a torque command value that cancels the cogging torque estimated by the first estimating means according to claim 1 and cancels the torque ripple estimated by the second estimating means according to claim 2. Wind power generation system characterized by controlling

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