JPS61106099A - Generator - Google Patents

Abstract

PURPOSE:To simplify a generator by connecting a frequency converter between the primary circuit and the secondary circuit of an induction machine, and connecting a synchronous machine with the primary or secondary circuit. CONSTITUTION:When a prime mover 6 is driven, and a switch 20 is closed to supply a DC current from a DC power source 21 to the secondary circuit of an induction machine 1, an AC voltage of frequency f3 is output to the primary circuit 7 of the machine 1. Thus, a synchronous machine 9 is operated without load at the rotating speed corresponding to the frequency f3 to apply reactive power, i.e., exciting current to the machine 1. Simultaneously, a frequency converter 4 supplies the power of the frequency f2 to the secondary circuit of the machine 1. Thus, an AC voltage of the frequency of f2+f3 is output from the primary circuit of the machine 1. The switch 20 is opened when becoming the normal state to stop supplying the DC current.

Description

[Detailed description of the invention] A wound induction machine is driven by a prime mover, and the rotation of the rotating magnetic field of the induction machine is determined in relation to the number of poles of the induction machine and the frequency of the three-phase AC excitation current flowing through its primary winding. The secondary rotor of the induction machine is driven to rotate by the prime mover in the same direction as the rotating magnetic field, and a rectifier and an inverter are connected to the circuit output from the secondary output terminal of the induction machine, A method of creating a circuit in which the AC obtained from the AC output terminal of the inverter is used as the primary winding excitation current of the induction machine, thereby achieving self-excitation of the induction generator, is disclosed in Japanese Patent No. 540293. This method is known from Japanese Patent No. 556553, Japanese Patent No. 727416, and the like.

Such an invention has the advantage that the frequency of the output of the generator supplied to the load can be controlled regardless of the rotational speed of the generator driven by the prime mover. For example, it is possible to supply power at a constant frequency to the load even if the rotational speed of the prime mover changes to some extent, or it is possible to maintain the output frequency of the generator supplied to the load while keeping the rotational speed of the prime mover approximately constant. Its advantage is that it can be controlled within a certain range.

Although having such advantages, the above-mentioned known examples have the following drawbacks. In other words, the synchronous rotational speed n [rpm] corresponding to the number of poles p [number] of the induction machine and the frequency f [Hz] of the three-phase AC excitation current flowing through the primary winding is 120 f/p. For example, in a two-pole machine, the frequency In order to correspond to 60 [Hz], it is necessary to rotate at a speed faster than the synchronous rotation speed of 3600 [rpm]. However, if the prime mover is a windmill or waterwheel, its rotational speed is 1000 [rpm].
] In many cases, the speed is as low as below. In that case, the number of poles of the rotating machine becomes large, such as 10 or 12 poles, making the structure complicated and expensive. In order to overcome this drawback, Patent Application No. 88258 issued in 1988 proposes a system in which power is supplied from the primary winding terminal of an induction machine having a primary winding and a secondary winding that are electromagnetically coupled to each other. An output terminal of a frequency converter having an electrically connected input terminal is electrically connected so as to supply power to the secondary winding of the induction machine, and the rotor of the induction machine is driven by a prime mover to generate the induction machine. The relationship between the rotational speed n [rpm], the number of poles p [numbers] multiplicative product np, and the power frequency f1 [Hz] generated in the primary winding is pn<1
20f1, and by supplying power from the frequency converter to the secondary winding of the induction machine, the supplied power frequency f2 is added to f3 of pn=120f3, resulting in f2+f3.
The electrical connection phase sequence from the output terminal of the frequency converter to the secondary winding of the induction machine is arranged so that = f1.

There are considered to be three problems with such Patent Application No. 88258 of 1988. First, since the output of the generator must be supplied to the load using a self-excited inverter, the generator output waveform does not become a sine wave. The closest self-excited inverter to obtaining a sine wave output is a PWM type inverter, but it is not a perfect sine wave output. Furthermore, it is difficult to supply adequate reactive power.

Furthermore, there are difficulties in manufacturing and controlling self-excited inverters themselves.

Eliminating such drawbacks in the inventions of the previous application, the motor output waveform in these devices is made close to a sine wave, appropriate reactive power can be supplied, and a simple separately excited inverter is used. Patent Application No. 143132 filed in 1982 was developed in order to be able to control the output frequency of a generator using an induction machine by keeping the number of poles to a relatively small number while dealing with a relatively low-speed prime mover. Now, the induction machine has a primary winding and a secondary winding that are electromagnetically coupled to each other, and the induction machine is connected to the output terminal of the frequency converter, which has an input terminal that is electrically connected so that power is supplied from the primary winding terminal of the induction machine. Electrical connection is made so that power can be supplied to the secondary winding, and the rotor of the induction machine is driven by a prime mover, so that the multiplicative product of the rotation speed n [rpm] of the induction machine and the number of poles p [pieces] is made. np
Power is supplied from the frequency converter to the secondary winding of the induction machine so that the relationship between the power frequency f1 [Hz] generated in the primary winding is pn<120f1, and the supplied power frequency f2 is is added to f3 of pn=120f3 to become f2+f1, and a synchronous machine is connected to the main circuit, that is, the primary or secondary circuit of the induction machine, and a device is provided to control the excitation current of the synchronous machine. . However, in order to concretely operate this synchronous machine under no load, Patent Application No. 143132 of 1981 provides an electric motor separate from the synchronous machine. A speed control device for the generator must also be provided, resulting in a complex overall device.

The present invention eliminates the drawbacks of Patent Application No. 143132 of 1982, reduces the rotational speed of the rotary drive prime mover of a generator using an induction machine, and simplifies the entire device in an arrangement that allows the use of a simple separately excited inverter. purpose.

In order to achieve such an object, the present invention provides a primary winding of an induction machine 1 having a primary winding and a secondary winding that are electromagnetically coupled to each other, as shown in FIG. 1 of the specific electrical connection diagram. an output terminal 5 of a frequency converter 4 having an input terminal 3 electrically connected to be supplied with power from the line terminal 2; When the rotor of the induction machine 1 is driven by the prime mover 6, the rotational speed n [rpm] of the induction machine 1, the multiplicative product np of the number of poles p [number], and the power frequency f1 [Hz] generated in the primary winding.
] so that pn<120f1, and power is supplied from the frequency converter 4 to the induction machine secondary winding, and the supplied power frequency f2 is added to f3 of pn=120F3, resulting in f2+f3. = f1, a synchronous machine 9 or 10 is connected to the main circuit of the induction machine 1, that is, the primary 7 or secondary circuit 8 of the induction machine 1, and the no-load loss of the synchronous machine 9 or 10 is is balanced by the power supplied from the main circuit 7 or 8 of the induction machine 1 through the terminal 11 of the synchronous machine 9 to cause the synchronous machine 9 to operate with no load, and the main circuit of the induction machine 1 from the synchronous machine 9 or 10 is balanced. 7 or 8 to supply reactive power.

The first frequency conversion device 4 is composed of a forward conversion device 12, a reactor 13, and an inverse conversion device (inverter) 14 connected together. The forward conversion device 12 and the inverse conversion device 14 each consist of rectifiers 17 and 18 with control elements, and are arranged so that the control element circuits can be controlled by control devices 16 and 15. In this case, the inverse converter 14 is separately excited, has a simple structure, and is arranged so that its control device 15 can control the control elements of the rectifier 18 to control its lead angle. Although the synchronous machine 9 is connected to the primary circuit 7 of the induction machine 1, an arrangement in which the synchronous machine 10 is connected to the secondary circuit 8 of the induction machine 1 may also be used. Now consider the case where the synchronous machine 9 is connected to the primary circuit 7 of the induction machine 1. The synchronous machine 9 continues to rotate if the no-load loss can be compensated for, but as shown in FIG. 2, the no-load loss increases as the rotation speed increases. FIG. 2 shows an example of a synchronous machine; the horizontal axis shows its rotational speed in rpm, and the vertical axis correspondingly shows its no-load loss. The no-load loss is in watts [w
], and in this example, 450W corresponds to 1800 rpm at point B, and 3W corresponds to 1500 rpm at point A.
It becomes 50W.

On the other hand, if the input of one phase of the synchronous motor is P1 [W], then P1
=VIcos■ (1) Tazushi,
V is the supply voltage of the synchronous motor, I is the current, ■ is the phase angle between V and I, and cos is the power factor. The output P2 [W] of one phase of the synchronous motor is P2 = VIcos - raI2 (2) where the copper loss of one phase is raI2
=(Vcos - raI)I (3) ra is the resistance of one phase of the synchronous motor armature circuit. (
What can be considered from equations 2) and (3) is that the control element of the rectifier 17 of the forward converter 12 shown in FIG. The circuit 8, that is, the voltage of one of the main circuits of the induction machine 1, is controlled to control the voltage supplied to the synchronous machine 9 in no-load operation, and the electric power P1 generated in the synchronous machine 9, that is, the voltage of the synchronous machine 9 in no-load operation, is controlled. This means that the synchronous machine output P2 can be controlled to balance the loss. Controlling the voltage of the secondary circuit 8 of the induction machine 1 also means controlling the voltage of the primary circuit 7 of the induction machine 1. In this way, controlling the voltage supplied to the synchronous machine 9, The rotational speed can be controlled by power supply balanced with the losses shown in Figure 2. A case in which a synchronous machine is connected to the secondary circuit 8 of the induction machine 1 as shown at 10 is also considered similarly. In FIG. 1, the frequency or voltage of the primary circuit 7 of the induction machine 1 or the rotation speed of the synchronous machine 9 is detected by a frequency detection device 19 (which detects the rotation speed of the primary circuit 7 of the induction machine 1 or the rotation speed of the synchronous machine 9). , the frequency is detected and if it is high or low compared to the set frequency value, it acts on the control device 16 depending on the height, thereby controlling the control angle by acting on the control element of the rectifier 17 of the forward converter 12. The main circuit voltage of the induction machine 1, which is the output circuit of the frequency converter 4, is controlled to make the frequency of the primary circuit 7 constant.

Think about when you start now. The prime mover 6 is driven to rotate the induction machine 1. When the switch 20 is closed and DC is supplied from the DC power supply 21 to the induction machine 1, an AC voltage with a frequency of f3 is supplied to the primary circuit 7 of the induction machine 1, AC power is supplied to the synchronous machine 9, and the synchronous machine 9 is operated without load at a rotational speed corresponding to frequency f3 [Hz]. As a result, the synchronous machine 9 generates reactive power, that is, excitation current, to the induction machine 1.

At the same time, power at a frequency of f2 is supplied from the primary circuit of the induction machine 1 to the secondary circuit of the induction machine 1 through the frequency converter 4, and AC voltage at a frequency of f2 + f3 = f1 is supplied to the primary circuit. It becomes like this. The same applies when the periodic machine 10 is connected to the secondary circuit of the induction machine 1. When the steady state is reached in this way, the switch 20 is opened and the supply of the DC power source 21 is stopped.

When the steady state is reached in this way, synchronous machine 9 or 1
0 adjusts its excitation current and supplies excitation power or reactive power to the primary circuit 7 or secondary circuit 8 of the induction machine 1 to supply the reactive part of this power generation system, but on the other hand, the synchronous machine 9 or 10 The applied voltage is controlled by the forward converter 12, and electric power corresponding to the voltage is applied from the induction machine 1 to perform no-load operation.

The features of the operation and effect of the device of the present invention described above can be summarized as follows.

(1) Regardless of the rotational speed of the prime mover that drives the generator,
A device that can output power at a set frequency can be easily implemented using a device with a relatively low motor rotational speed. In particular, it is possible to easily make the generator output waveform close to a sine wave.

(2) Appropriate reactive power can be easily supplied to the grid in such a device. In particular, this allows the inverter to be made into a separately excited type that is simple and reliable in operation, and the drive rotation of such a reactive power-supplied synchronous machine can be controlled by controlling the AC voltage applied to the synchronous machine itself. It can be made simple and reliable in operation.

[Brief explanation of drawings]

FIG. 1 is an example of a specific electrical connection diagram of the present invention. FIG. 2 shows an example of a characteristic diagram of a synchronous machine used during the connection of the present invention. Further, in the drawings, explanations of the symbols representing main parts are as follows. 1: induction machine, 2: primary winding terminal of induction machine, 3: input terminal of frequency converter 4, 4: frequency converter, 5: output terminal of frequency converter 4, 6: prime mover, 7: induction machine 1 Primary circuit, 8: Secondary circuit of induction machine 1, 9, 10: Synchronous machine, 11: Terminal of synchronous machine, 12: Forward conversion device, 13: Reactor, 14: Inverse conversion device, 15: Control device, 16 : Control device, 17: Rectifier with control element, 18: Rectifier with control element, 19: Frequency detection device, 20: Switch, 21
:DC power supply.

Claims (1)

[Claims] from the output terminal of a frequency converter having an input terminal electrically connected to receive power from the primary winding terminal of the induction machine having a primary winding and a secondary winding that are electromagnetically coupled to each other. An electrical connection is made so that power can be supplied to the secondary winding, and the rotor of the induction machine is driven by a prime mover, so that the multiplicative product np of the induction machine's rotational speed n [rpm] and the number of poles p [pieces] and the power frequency f_1 [Hz] generated in the primary winding
Supplying power from the frequency converter to the induction machine secondary winding so that the relationship between pn<120f_1,
f_ whose supply power frequency f_2 is pn=120f_3
In addition to 3, in an arrangement such that f_2 + f_3 = f_1, a synchronous machine is connected to the main circuit of the induction machine, that is, the primary or secondary circuit of the induction machine, and the no-load loss of the synchronous machine is calculated as the above induction A power generating device arranged so as to balance the power supplied from the main circuit of the machine through the terminals of the synchronous machine to cause the synchronous machine to operate without load, and to supply reactive power from the synchronous machine to the main circuit of the induction machine.