JP2009303284A - Flywheel-type uninterruptible power supply device and its controlling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flywheel-type uninterruptible power supply device which can drastically reduce the radius displacement of a rotor occurring on exciting a generator from a non-excitation state to maintain the excitation speed at high, and can prevent contact between the rotor and a magnetic bearing while maintaining the power generator output at high to greatly lower an increase and loss in control current caused by the rotor displacement, and to provide a control method for the same. <P>SOLUTION: The flywheel-type uninterruptible power supply device includes the magnetic bearing device 20 that supports the rotation of the rotor 14a of an induction generator 14 in a non-contact state, wherein a flywheel is maintained in a freely rotating state by inertia while keeping the inductor generator non-excited with an inverter 16. The inverter is allowed to apply an excitation voltage to the inductor generator when a system voltage drop is detected, and simultaneously or in precedence over the application of the excitation voltage, the integration control of the magnetic bearing device is strengthened relative to a normal control characteristic till the generation voltage of the inductor generator is boosted up to a prescribed voltage to enhance the static rigidity thereof. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a flywheel uninterruptible power supply device that accumulates inertial energy in a flywheel and a control method thereof.

A flywheel type uninterruptible power supply is an uninterruptible power supply that accumulates inertial energy in a flywheel and generates electric power using the inertial energy during a power failure. Such an uninterruptible power supply is disclosed in Patent Document 1, for example.
Moreover, the magnetic bearing apparatus applicable to this uninterruptible power supply apparatus is disclosed by patent document 2, 3, for example.

An object of the flywheel uninterruptible power supply of Patent Document 1 is to make the induction motor in a non-excited state in a free rotation state due to inertia of the flywheel, and to perform re-excitation in a short time when necessary.
Therefore, in the apparatus shown in FIG. 6, inertial energy is accumulated in the flywheel 59. In this state, for example, when a power failure occurs, the squirrel-cage induction motor 58 is operated as a generator based on the rotational force of the flywheel 59. The AC energy generated by the squirrel-cage induction motor 58 is supplied to the flywheel inverter 51. The DC voltage converted from AC to DC by the flywheel inverter 51 is supplied to the DC bus 54 while being measured by the DC voltmeter 55. The load inverter 57 converts the generated electric power supplied to the DC bus 54 into an AC of 50 Hz, for example, and supplies it to the load 53. In addition, 52 is a power supply and 56 is a rectifier.

The magnetic bearing device of Patent Document 2 aims to perform good control even during the deceleration period of the rotating shaft.
Therefore, in Patent Document 2, in a magnetic bearing device including at least two magnetic bearing portions that support the rotation shaft in the radial direction and a drive portion that performs rotation acceleration / deceleration of the rotation shaft, the amount of displacement fluctuation in the radial direction of the rotation shaft. Is provided with a PID feedback control circuit that feeds back a PID control value obtained by performing PID control including a proportional element, an integral element, and a differential element to the magnetic bearing unit, and the PID feedback control circuit causes the drive unit to act as a DC brake. In the period during which the rotating shaft is decelerated, the response characteristic similar to that in the non-decelerating period is obtained in the deceleration period by changing the gain of the proportional element during PID control.

The magnetic bearing device of Patent Document 3 aims to increase the load capacity of the electromagnet without increasing the excitation current supplied to the electromagnet.
Therefore, in Patent Document 3, as shown in FIG. 7, the rotating body 63 is supported in a non-contact manner in the axial control axis direction and the radial control axis direction by a plurality of pairs of electromagnets 61 and 62. The magnetic bearing device includes position detection means 64 and 65 for detecting the position of a pair of electromagnets and a rotating body and outputting a position detection signal Zs for each control shaft, and a levitation reference position signal output means for outputting a levitation reference position signal. , Electromagnet control signal output means for outputting electromagnet control signals (Io + Ic) and (Io−Ic) including an integral output based on the levitation reference position signal and the position detection signal, and electromagnet drive for driving the electromagnet based on the electromagnet control signal Means 66 are provided. The levitation reference position signal output means changes the levitation reference position signal so that the integral output is within a preset control system integral output range.

Japanese Patent Application Laid-Open No. 2007-259587, “Power Generation Regeneration Device, Power Generation Regeneration Device Excitation Method, and Power Generation Regeneration Device Power Generation Method” Japanese Patent Application Laid-Open No. 8-219155, “Magnetic Bearing Device” Japanese Patent Application Laid-Open No. 2002-349567, “Magnetic Bearing Device”

In the flywheel uninterruptible power supply of Patent Document 1, the induction motor is de-energized during standby operation to reduce loss. In this state, when a system voltage drop is detected due to a power failure or the like, the induction motor is excited at high speed to operate as a generator, and power generation is performed for several tens of seconds while the flywheel is decelerated.
However, when a system voltage drop is detected and excitation is performed at a high speed (for example, about 100 to 200 μsec), an unbalanced attractive force is generated in the generator, and the unbalanced attractive force causes the generator rotor to be drawn in one direction.
This unbalanced attraction force is caused by non-uniformity in the gap between the rotor and stator of the generator (for example, about 1 mm). The higher the excitation speed and the larger the power generation output, the unbalanced attraction. Strength increases.

On the other hand, when a magnetic bearing is used as a bearing for supporting the rotor of the generator, the electromagnet constituting the magnetic bearing is located close to the rotor (gap 0.3 to 0.4 mm), and the position displacement of the rotor is fed back. Control and hold position.
This feedback control mainly uses proportional control (P control) proportional to position displacement and differential control (D control) proportional to speed in order to enhance the dynamic characteristics of position control.

  Therefore, in the case of a non-contact type bearing such as a magnetic bearing, when the induction motor is excited at a high speed from a non-excited state, the static stiffness of the magnetic bearing is insufficient and the rotor is drawn in one direction. There was a risk that the rotor would contact the auxiliary bearing and be damaged. Further, there is a problem that the control current of the magnetic bearing is extremely increased due to the displacement of the rotor, and the loss is greatly increased.

Therefore, conventionally, for example, the following measures have been taken in order to avoid the above problems.
(1) Considering the static rigidity of the magnetic bearing, slow the excitation speed from the non-excited state.
(2) Reduce the generator output in consideration of the static rigidity of the magnetic bearing.
However, as a result of these countermeasures, the uninterruptible power supply, such as a prolonged power failure time (for example, about 200 to 300 msec) from the detection of the system voltage drop to the start of power generation by the uninterruptible power supply, or the generation output is insufficient. There was a problem that the function of was impaired.

  The present invention has been developed to solve the above-described conventional problems. That is, the object of the present invention is to greatly reduce the radial displacement of the rotor that occurs when the generator is excited from the non-excited state, thereby maintaining the excitation speed at a high speed and increasing the generator output. An object of the present invention is to provide a flywheel uninterruptible power supply apparatus and a control method thereof that can prevent contact between the rotor and the magnetic bearing while maintaining the same, and can greatly suppress an increase and loss in control current due to rotor displacement.

According to the present invention, a flywheel that rotates around an axis and stores inertial energy;
An induction generator that is also connected to the flywheel and that is driven to rotate and that is driven to rotate to generate electricity; and
An inverter that applies excitation voltage to the induction generator for excitation and converts AC voltage generated by the induction generator into DC voltage;
A magnetic bearing device that supports the rotation of the rotor of the induction generator in a non-contact manner,
When applying an exciting voltage to an induction motor in a non-excited state by the magnetic bearing device, the flywheel is characterized in that, at the same time or in advance, the integral control is strengthened with respect to normal control characteristics to increase the static rigidity. A wheel-type uninterruptible power supply is provided.

According to the present invention, a flywheel that rotates around an axis and stores inertial energy;
An induction generator that is also connected to the flywheel and that is driven to rotate and that is driven to rotate to generate electricity; and
An inverter that applies excitation voltage to the induction generator for excitation and converts AC voltage generated by the induction generator into DC voltage;
A magnetic bearing device that supports the rotation of the rotor of the induction generator in a non-contact manner,
The induction motor is de-energized by the inverter and the flywheel is maintained in a free rotating state by inertia,
When the system voltage drop is detected, an excitation command is sent to the inverter, an excitation voltage is applied to the induction motor by the inverter, and at the same time or in advance, until the generated voltage of the induction generator reaches a predetermined voltage, There is provided a control method for a flywheel uninterruptible power supply, characterized in that the integral control of the magnetic bearing device is strengthened to increase the static rigidity.

  According to a preferred embodiment of the present invention, the magnetic bearing device feedback-controls the rotor position of the induction generator by PID control or zero bias control.

  According to the above-described apparatus and method of the present invention, upon detection of a system voltage drop, an excitation command is sent to the inverter and an excitation voltage is applied to the induction motor by the inverter. Until the voltage is reached, the integral rigidity control of the magnetic bearing device is strengthened to increase the static stiffness, so that the static stiffness of the magnetic bearing device can be increased at the same time or prior to the excitation of the induction generator, and no control delay occurs. .

  Therefore, the radial displacement of the rotor that occurs when the generator is excited from the non-excited state can be greatly reduced, thereby maintaining the excitation speed at a high speed and maintaining the generator output high. And magnetic bearing contact can be prevented, and increase and loss of control current due to rotor displacement can be greatly suppressed.

  Further, since the present invention is not limited to PID control, it can be applied to all controllers using integration in various control methods.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

FIG. 1 is an overall configuration diagram of a flywheel uninterruptible power supply according to the present invention.
In this figure, 1 is a system input (for example, AC400V, 3 phase, 50/60 Hz), and 2 is a load side output (for example, AC400V, 3 phase, 50/60 Hz). Further, 3 is an AC / DC converter, 4 is a DC / AC converter, and 5 is a DC bus connecting between them.

  With this configuration, the AC voltage of the system input 1 is converted into a DC voltage (for example, DC 600 V, single phase) by the AC / DC converter 3 and further converted into an AC voltage by the DC / AC converter 4 and supplied to a load device (not shown). be able to. This state is substantially the same as the case where an AC voltage is directly supplied from the system input 1 to the load side output 2.

  In FIG. 1, the flywheel uninterruptible power supply 10 of the present invention further includes a flywheel 12, an induction generator 14 also serving as an electric motor, an inverter 16, a voltage detector 18, and a magnetic bearing device 20. Note that 11 is a capacitor, and 15 is a general controller.

The capacitor 11 is a capacitor or a storage battery, is connected to the DC bus 5, and stores a minimum electric power for operating the inverter 16.
The overall controller 15 outputs a command signal to the inverter 16 and the magnetic bearing device 20 according to the output signal of the voltage detector 18.

  The flywheel 12 is made of, for example, CFRP, and stores inertia energy by rotating at high speed around a vertical axis. The rated rotational speed of the flywheel 12 is, for example, 13000 rpm (210 Hz).

  The induction generator 14 also serving as an electric motor includes a rotor 14 a and a stator 14 b, and the rotor 14 a is connected to the flywheel 12. The induction generator 14 has both functions of an electric motor that rotationally drives the flywheel 12 and a generator that is rotationally driven by the flywheel 12 and generates electric power. Hereinafter, the induction generator 14 also serving as an electric motor is simply referred to as an “induction generator”.

The inverter 16 is located between the DC bus 5 and the induction generator 14 and applies an excitation voltage to the stator 14b of the induction generator 14 to excite it to operate the induction generator 14 as an electric motor. Alternatively, the inverter 16 14 has a function of converting the AC voltage generated at 14 into a DC voltage.
In this example, the voltage detector 18 is a voltmeter attached to the DC bus 5, detects a system voltage that supplies a DC voltage (in this example, the voltage of the DC bus 5), and outputs it to the overall controller 15. The voltage detector 18 may be attached to the system input 1 or the load side output 2.

  The magnetic bearing device 20 includes an electromagnet 20a, a position detector 20b, and a magnetic bearing control device 22, and supports the rotation of the rotor 14a of the induction generator in a non-contact manner. In the following example, the magnetic bearing device 20 is a magnetic bearing that supports the radial direction of the rotor 14a, but may also support the thrust direction in the same manner.

  2 is a partially enlarged view of FIG. 1, and FIG. 3 is a configuration diagram of a magnetic bearing device according to the present invention.

3, the magnetic bearing device 20 of the present invention includes at least a pair of electromagnets 20a, a rotor support portion 14c directly connected to the rotor 14a, a position detector 20b, and a magnetic bearing control device 22. The pair of electromagnets 20a are arranged to face each other.
Reference numeral 21 denotes a power amplifier for driving the pair of electromagnets 20a.

  The rotor support portion 14c is disposed between the pair of electromagnets 20a and is held at an intermediate position. In this example, the rotor support portion 14c is, for example, a vertical axis, and is supported in the left-right direction in the figure by a magnetic bearing, and is not affected by the direction of gravity. The vertical support is performed by another magnetic bearing.

The position detector 20b is a non-contact type position sensor and detects the position x of the rotor support portion 14c.
The radial speed of the rotor support 14c may be detected instead of or in combination with the position x of the rotor support 14c. This sensor may be either a displacement sensor or a speed sensor, but may include both.

FIG. 4 is a block diagram showing a method for controlling the magnetic bearing device 20 according to the present invention. As shown in this figure, the magnetic bearing device 20 feeds back the rotor position x of the induction generator and maintains the rotor position x at a predetermined neutral position.
The magnetic bearing control device 22 feedback-controls the rotor position x of the induction generator by PID control or zero bias control.

FIG. 5 is an explanatory diagram of PID control. In this figure, (A) shows proportional control (P control), (B) shows integral control (I control), (C) shows differential control (D control), and (D) shows each characteristic of PID control. . In each figure, the horizontal axis represents the logarithmic scale angular frequency ω, and the vertical axis represents the gain G [dB].
PID control includes proportional control (P control) that outputs a suction force u proportional to the position displacement x, integration control (I control) that outputs a suction force u proportional to the time integral of the position displacement x, and position displacement x. Control combined with differential control (D control) that outputs a suction force u that is proportional to the time differential (speed).
Proportional control (P control) functions as a spring, differential control (D control) functions as a damper in parallel with the spring, and integral control (I control) functions as a spring (static stiffness) suitable for low frequencies.
Accordingly, the magnetic bearing control device 22 mainly performs proportional control (P control) and differential control (D control) in a normal operation state (non-excited state and excited state) in order to improve the dynamic characteristics of position control.

On the other hand, the zero bias control is to obtain a variable Z that is directly proportional to the acceleration in the control direction from the displacement x and the speed v of the rotor support portion 14c, and to set the control current of one electromagnet to zero according to the sign of this variable. Control means for controlling only the control current of the other electromagnet.
This zero bias control is disclosed in an unpublished patent by the present applicant (Japanese Patent Application No. 2007-090498: filed on Mar. 30, 2007).

  In FIG. 1, the flywheel type uninterruptible power supply 10 of the present invention applies an excitation voltage to an induction generator 14 by an inverter 16 and excites it to accelerate the flywheel 12 in a normal state. For example, after reaching 13000 rpm (210 Hz), the induction motor 14 is brought into a non-excited state by the inverter 16 and the flywheel 12 is maintained in a free rotating state due to inertia.

  In this free rotation state, the magnetic bearing control device 22 feedback-controls the rotor position x of the induction generator by the above-described PID control or zero bias control. Hereinafter, these control characteristics are referred to as “normal control characteristics”.

In this free rotation state, for example, when the voltage detector 18 detects a system voltage drop due to a power failure, the overall controller 15 outputs a command signal to the inverter 16 and the magnetic bearing device 20 simultaneously.
It is also possible to detect a sign of system voltage drop and output a command signal to the magnetic bearing device 20 prior to the inverter 16.
In response to this command signal, an excitation voltage is applied to the induction motor 14 by the inverter 16. At the same time or in advance, the magnetic bearing control device 22 strengthens the integral control (I control) of the magnetic bearing device 20 with respect to normal control characteristics as shown by the broken line in FIG. To increase.
The strength of the integral control (I control) is that this displacement is resisted by the unbalanced attractive force generated in the generator when the induction motor is excited at high speed (for example, about 100 to 200 μsec) and operated as a generator. Is set to be less than the clearance of the magnetic bearing.
The integral control (I control) is preferably continued until the generated voltage of the induction generator reaches a predetermined voltage, and thereafter, it is preferable to return to the normal control characteristics described above.

  According to the apparatus and method of the present invention described above, upon detection of a system voltage drop, an excitation command is sent to the inverter 16 and an excitation voltage is applied to the induction motor 14 by the inverter 16, and simultaneously or in advance, the power generation of the induction generator 14 is performed. Until the voltage reaches a predetermined voltage, the integral control of the magnetic bearing device 20 is strengthened to increase the static stiffness. There is no control delay.

Accordingly, the radial displacement (rotor position) x of the rotor 14a generated when the generator 14 is excited from the non-excited state can be greatly reduced, thereby maintaining the excitation speed at a high speed and reducing the generator output. While maintaining high, the contact between the rotor 14a (rotor support portion 14c) and the magnetic bearing 20 can be prevented, and the increase and loss of control current due to the rotor displacement (rotor position) x can be significantly suppressed.
Further, since the present invention is not limited to PID control, it can be applied to all controllers using integration in various control methods.

  In addition, this invention is not limited to embodiment mentioned above, Of course, a various change can be added in the range which does not deviate from the summary of this invention.

1 is an overall configuration diagram of a flywheel uninterruptible power supply device of the present invention. It is the elements on larger scale of FIG. It is a block diagram of the magnetic bearing apparatus by this invention. It is a block diagram of the control method by this invention. It is explanatory drawing of PID control. It is a schematic diagram of the apparatus of patent document 1. FIG. It is a schematic diagram of the magnetic bearing apparatus of patent document 3.

Explanation of symbols

1 system input, 2 load side output, 3 AC / DC converter,
4 DC / AC converter, 5 DC bus,
10 Flywheel uninterruptible power supply, 11 Capacitor,
12 Flywheel, 14 Induction generator combined with electric motor,
14a rotor, 14b stator, 14c rotor support,
15 general controller, 16 inverter,
18 voltage detector (voltmeter), 20 magnetic bearing device,
20a electromagnet, 20b position detector (position sensor),
21 Power amplifier, 22 Magnetic bearing control device

Claims (3)

A flywheel that rotates around its axis and stores inertial energy;
An induction generator that is also connected to the flywheel and that is driven to rotate and that is driven to rotate to generate electricity; and
An inverter that applies excitation voltage to the induction generator for excitation and converts AC voltage generated by the induction generator into DC voltage;
A magnetic bearing device that supports the rotation of the rotor of the induction generator in a non-contact manner,
When applying an exciting voltage to an induction motor in a non-excited state by the magnetic bearing device, the flywheel is characterized in that, at the same time or in advance, the integral control is strengthened with respect to normal control characteristics to increase the static rigidity. Wheel type uninterruptible power supply. A flywheel that rotates around its axis and stores inertial energy;
An induction generator that is also connected to the flywheel and that is driven to rotate and that is driven to rotate to generate electricity; and
An inverter that applies excitation voltage to the induction generator for excitation and converts AC voltage generated by the induction generator into DC voltage;
A magnetic bearing device that supports the rotation of the rotor of the induction generator in a non-contact manner,
The induction motor is de-energized by the inverter and the flywheel is maintained in a free rotating state by inertia,
When the system voltage drop is detected, an excitation command is sent to the inverter, an excitation voltage is applied to the induction motor by the inverter, and at the same time or in advance, until the generated voltage of the induction generator reaches a predetermined voltage, A control method for a flywheel uninterruptible power supply, characterized in that the integral control of the magnetic bearing device is strengthened to increase the static rigidity.   The method of controlling a flywheel uninterruptible power supply according to claim 2, wherein the magnetic bearing device feedback-controls the rotor position of the induction generator by PID control or zero bias control.

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