JPS62131797A - Controller for induction motor - Google Patents

Abstract

PURPOSE:To suppress a rush current without providing a current limiting reactor by connecting a power factor improving unit combined with a capacitor and a reactor with an output terminal of an induction motor in case of connecting the motor with a system. CONSTITUTION:An electromagnetic contractor 5 is closed in a state that a speed of an induction motor 1 is maintained at synchronizing speed, and a braker 3 is then closed. At this time, a delay rush current IIG flows in the motor 1, and an advancing rush current ISC flows by a phase advancing capacitor 61. However, since the currents IIG, ISG cancel each other out, totalized rush current I0 is suppressed to the minimum by the capacity of the capacitor 61 and a serial reactor 62. A power factor of a system 4 is improved by the capacitor 61 during load operation.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an induction generator that can minimize the inrush current that flows when the induction generator is connected to a grid (hereinafter referred to as connection). This relates to a control device.

[Technical Background of the Invention] Generally, when operating an induction generator, the speed of its rotor is increased to 1 degree of synchronous speed by a prime mover, and then the speed of the rotor is increased to 1 degree of synchronous speed, and then the speed of the rotor is increased to 1 degree of synchronous speed. . However, in this case, even if the input is performed at synchronous speed, an inrush current several times (4 to 7 times) the rated current of the induction generator will flow, and the negative effect on voltage fluctuations (drops) in the grid cannot be ignored. There are many. Therefore, in order to suppress such inrush current, it is recommended to install a current-limiting reactor in series with the output terminal of the induction generator, which is opened when an induction generator is connected [with an i-contactor etc. connected in parallel]. It is being done to

[Problems with the back circle technology] However, although it is possible to suppress inrush current by providing a current limiting reactor, it is not economically necessary because it becomes completely unnecessary after the addition of an induction generator. There is a problem in that not only is it extremely wasteful (initial investment), but also an installation space is required to install it. In particular, as the capacity of the induction generator increases, the ff1ll contactor also needs to have a very large capacity (in some cases, a breaker is used), making the above problem even more serious. becomes.

[Purpose of the Invention] The present invention was made to solve the above-mentioned problems, and its purpose is to minimize the inrush current caused by the addition of an induction generator without providing a current limiting reactor like the conventional one. In addition to minimizing the negative impact on grid voltage fluctuations,
It is an object of the present invention to provide an economical induction generator control device capable of improving the power factor of a system during load operation of an induction generator 11 and requiring less installation space.

[Summary of the Invention] In order to achieve the above object, the present invention provides an induction generator that is provided so as to be connectable to a power grid via a first switch, and is configured to generate an induction generator that is connected to the power grid at approximately the same time as or shortly after the first switch is turned on. Along with being introduced earlier than.

While the first switch is closed, a second switch that is closed is made up of a combination of a capacitor and a reactor, and is connected in parallel to the output terminal of the induction generator Nada through the second switch. The power factor correction device is characterized in that the power factor correction device is comprised of a

[Embodiments of the invention] An embodiment of the present invention shown in the drawings will be described below.

FIG. 1 shows an example of the circuit configuration of a wJ control device for an induction generator according to the present invention, and is shown in a three-line diagram. In Fig. 1, 1 is a three-phase induction generator (IG) driven by a primitive generator (PM>2), and its output terminal is connected to a cable or conductor as a first switch or disconnector 3. It is provided so that it can be connected to the system 4 via.

On the other hand, 5 is an electromagnetic contactor as a second switch that is turned on almost at the same time as or before the breaker 3 is turned on, and is turned on while the breaker 3 is turned on; 6 is a phase advancing Capacitor 61. A series reactor 62 connected in series with this. and a discharge coil 63 connected between each phase.
The power factor correction device is a power factor correction device which is directly connected in parallel to the output terminal of the induction generator 1 via the electromagnetic contactor 5. Further, 7 is a current transformer (CT) that extracts the II current flowing to the phase advance capacitor 61 of the power factor correction device 6, and 8 is an overcurrent relay that responds to the secondary II current of the current transformer 7. When the overcurrent relay 8 operates, the electromagnetic contactor 5 is opened. Furthermore, an instrument transformer (PT) is connected in parallel to the output terminal of the 9G upper penetrating induction generator ll11 and outputs a single peak of the voltage.
), 1 (N) is an overvoltage I! electric appliance that responds to the secondary voltage of the 100-power transformer 9, and this overvoltage [1? Even if you open it, it will come in.

Next, Ill all of the induction generator configured as described above
I will explain the effect of the first position.

Now, with the speed of the induction generator 1 maintained at the synchronous speed by the Hara e Tsuki 2, first turn on the electromagnetic contactor 5, then turn on the breaker 3, and the induction will be as shown in Figure 2. Departure 11
A delayed inrush current 1+c flows due to fil, and an advanced inrush current rsc flows due to the phase advancing capacitor 61. But in this case, each of these rush 1! Since the currents 1ta and IBc have a canceling effect, the combined inrush current Io can be minimized by selecting the phase advancing capacitor 61 and the series reactor 62, and the addition of the induced power generation ^1 Therefore, the voltage drop in system 4 becomes extremely small and its influence can be ignored.

As an example, inrush current I Ia h' i of induction power generation R1
It shall be five times the rated current IO of one lead 111. It is well known that when the capacity of the series reactor 62 is 6% of the capacity of the phase advance capacitor 61, the rush current Isc of the phase advance capacitor 61 is five times the rated current of the phase advance capacitor 61. 1c-1a and the decay time constant T of IC and IO
By selecting the capacitance of the phase advance capacitor 61 so that c-To, the total inrush current 1o can be suppressed to approximately zero. Note that a tap (not shown) is attached to the series reactor 62, and the inrush current Is+ of the phase advance capacitor 61 can be adjusted by selecting this tap.

Next, when the induction generator 1 enters the load operation state by turning on the above-mentioned breaker 3, since the power factor correction device 6 is connected via the electromagnetic contactor 5, the interphase capacitor 61 Since the power factor of the system 4 is improved, it becomes possible to reduce the capacitance of the phase advance capacitor required by the operation of the induction generator 1 by 111.

On the other hand, when the above-mentioned induction generator 'l1111 is in a loaded operation state and the circuit breaker 3 is opened due to a system accident, if the 'l4Ea contactor 5 remains closed, the induction generator will be generated due to the self-excitation phenomenon. The voltages of the IH 111 and the phase advancing capacitor 61 may increase.

However, in this case, there is no problem because the overvoltage generated in the induction generator 1 is detected, the overvoltage relay 10 is activated, and the 'R11fI contactor 5 is opened. In addition, when the element of the phase advancing capacitor 61 deteriorates over time and an overcurrent occurs, this excessive N current is detected, the excessive current relay 8 is operated, and the 1ila contactor 5 is opened. protection will be provided. Furthermore, 'R1! When the contactor 5 is opened, the charge in the phase advance capacitor 61 is rapidly attenuated through the discharge coil 63, so there is no danger to humans or animals.

As mentioned above, in this embodiment, the induced generator 1! ! In 11,
The electromagnetic contactor 5 and the phase advancing capacitor 61. which are turned on almost simultaneously with or before the turning on of the circuit breaker 3, and which are turned on while the circuit breaker 3 is turned on. a power factor correction device 6 which is formed by combining a series reactor 62 and a discharge coil 63 and is directly connected in parallel to the output terminal of the induction power generation 11 via the 1i11 contactor 5;
An overcurrent relay 8 which responds to the current flowing through the phase advance capacitor 61 of the power factor correction device 6 and opens the electromagnetic contactor 5 by its operation, and an overcurrent relay 8 which responds to the output voltage of the induction generator 1 and opens the electromagnetic contactor 5 by its operation. A control device is constituted by an overvoltage relay 10 that opens the electromagnetic contactor 5.

Therefore, while omitting the conventional current limiting reactor, it is possible to minimize the inrush current caused by the addition of the induction generator 1 and to suppress the voltage drop in the system 4 to a practically negligible level. In addition, it is possible to solve the problem of a drop in the power factor of the system 4 due to the installation of the induction generator 1 when the induction generator 1 is running under load. 43 and can be used effectively, making it possible to improve the cost and reduce the installation space. Furthermore, an over-N flow relay i88 and an over-voltage relay 11110 are provided, and the operation of at least one of them opens the electromagnetic contactor 5 that connects the power factor correction device 6 to the induction generator 'amii. Therefore, it is possible to obtain a highly reliable control device with no problems in terms of safety.

In the above embodiment, a case has been described in which a delayed inrush current flows due to the addition of the induction generator 1, but the present invention is not limited to this, and can also be applied to a case where a delayed inrush current flows due to the addition of the induction generator 1. can be similarly applied.

In addition, the present invention can be modified and implemented in various ways without changing the gist thereof.

[Effects of the Invention] As explained above, according to the present invention, the induction generator 1! is provided so as to be connectable to the grid via the first switch! In the machine, a capacitor and a reactor are combined with a second switch that is closed at approximately the same time as or before the first switch is closed, and that is closed while the first switch is closed. and a power factor correction device connected in parallel with the output terminal of the induction generator via the second switch, the induction generator can be operated without providing a current limiting reactor. An extremely economical and easy-to-install design that minimizes the inrush current caused by the addition of electricity, eliminates the negative effect on voltage fluctuations in the grid, and improves the power factor of the grid during load operation of the induction generator. The control system can provide induction power generation with less space.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, and FIG. 2 is a curve diagram for explaining the effects of the embodiment. 1...Induction 1! machine, 2... prime mover, 3... breaker, 4... system, 5...'R magnetic contactor, 6...
Power factor correction device, 61... Phase advance capacitor, 62...
・Series reactor, 63...Discharge coil, 7...Current transformer, 8...Overcurrent relay, 9...Instrument transformer,
10...Overvoltage relay. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (4)

[Claims] (1) In an induction generator that is provided so as to be connectable to the grid via a first switch, the induction generator is turned on at approximately the same time as or earlier than the turning on of the first switch, and the first When the switch is closed, the second switch, which is closed, is combined with a capacitor and a reactor, and the second switch is closed.
A control device for an induction generator, comprising a power factor correction device connected in parallel to the output terminal of the induction generator via a switch. (2) The control device for an induction generator according to claim 1, wherein the power factor correction device is directly connected to the induction generator shaft and connected in parallel with the output terminal. (3) Claim (1) characterized in that an overvoltage relay is provided that responds to the output voltage of the induction generator, and the second switch is opened when the overvoltage relay operates. A control device for the induction generator described above. (4) Power factor correction device An overcurrent relay that responds to the flowing current is provided, and when the overcurrent relay operates, the second switch is opened. ) A control device for an induction generator as described in item 2.