JPH0837800A - Stable poser supply equipment of power system for closed circuit - Google Patents

Abstract

PURPOSE:To provide a stable power supply equipment for a closed circuit power system where no equipment of special construction or function is provided, or the response of the control function need not be improved. CONSTITUTION:An induction machine 4 is connected to a drive shaft of a generator 1, and the induction machine 4 is connected to a specified AC power source circuit 5 separated from an output circuit of the generator 1. The induction machine 4 is functioned as the generator when the load is below the reference, level, while the induction machine 4 is functioned as a motor when the load exceeds the reference level, and the output is superposed on the output of a prime engine 2 so as to drive the generator 1. In this case, the generated power by the induction machine 4 to be functioned as the generator when the load is below the reference level is preferably regenerated to the AC power source circuit 5. The above-mentioned induction machine 4 may be replaced by a DC machine, and the AC power source circuit 5 may be replaced by a DC power source circuit so as to be functioned in the similar manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device in a closed-circuit power system in which power is supplied by a generator driven by a prime mover such as a diesel engine or a gas turbine, and more particularly, it relates to load fluctuation. Stable power supply for a closed-circuit power system that does not require a large-capacity power generation function that corresponds to the maximum load while stable supply of high-quality power is possible even when an excessive amount of power is required. Regarding the device.

[0002]

2. Description of the Related Art In factory facilities, construction sites, etc., there is a closed-circuit power system in which AC power is supplied by a generator driven by a diesel engine or an internal combustion engine of a gas turbine as a prime mover. In such a power system, a closed circuit is formed in which power is supplied only by the equipped generator. In such a closed-circuit power system, it corresponds to the maximum load amount predicted in advance so that the load power is not required to exceed the maximum capacity of the generator or prime mover equipped in this system and the quality of the power does not deteriorate. The capacity of the generator to be installed, the prime mover for driving the generator, and the control function thereof are determined. In order to obtain the required electric power, there is a case where a means for connecting a plurality of generators in parallel and controlling the number of generators driven according to the load amount is taken. Equipped with an inverter and a battery, the battery can be charged during low load, or by solar battery during daytime, resulting in a heavy load, or at night, the power stored in the battery can be used by the generator. Means for using in addition to generated power are also being implemented.

In the case of a power generator driven by a prime mover, the output power fluctuates because the voltage is not constant due to a response delay of the prime mover that drives the generator against a sudden change in load power, and the alternator changes. In this case, the frequency may fluctuate. That is, in factories, there are also electric power systems with large load fluctuations, such as rolling mills, welding machines, fusing machines, cutting machines, and press machines, which rapidly require excessive loads. A flywheel connected to the rotating shaft of a load machine such as a press machine, that is, the drive shaft of an electric motor, equipped with a large-capacity generator capable of instantaneously covering the load required under such load conditions. It is designed to withstand sudden loads.

[0004]

By the way, in the conventional electric power system as described above, in order to withstand a steep load change, a generator capable of withstanding a load about twice the steady load is required. become. In addition, as described above, a power system of poor quality in which the frequency is momentarily lowered or the voltage is lowered due to a response characteristic of a prime mover corresponding to a load change, a delay in a control function, or the like may be a problem. Installing a flywheel on the rotating shaft of a load machine is not necessarily an appropriate means other than a machine in which the load fluctuates under regularly defined conditions such as a press, and is not mechanical such as a welding machine or a fusing machine. It cannot be used for electrical loads.
In addition, when equipping the drive shaft of the generator with a flywheel, it is inevitable that the inertial force must have a margin, which increases the torsional vibration of the drive shaft as the flywheel is installed, and increases the torsional vibration. A means for coping with the increase of the axial load and the weight of the flywheel is required to set the rotating shaft to withstand, and the resonance frequency such as torsional vibration is lowered, and a countermeasure against it is also necessary. The present invention solves the above-described problems (problems) of conventional power systems, improves the response characteristics to load fluctuations without providing a generator and a prime mover for driving the generator corresponding to the maximum load amount. It is an object of the present invention to provide a stable power supply device for a closed circuit power system that can supply high-quality power to a load.

[0005]

In order to solve the above problems, in a stable power supply system for a closed circuit power system according to the present invention, an induction machine is connected to a drive shaft of a generator, and the induction machine is connected to the generator. The output circuit is connected to a separate AC power supply circuit, and when the load is below the reference level, the induction machine functions as a generator, and when the load exceeds the reference level, the induction machine functions as an electric motor. The output is superimposed on the output of the prime mover to drive the generator. In this case, when the induction machine is made to function as a generator, it is desirable to regenerate the generated power to the AC power supply circuit. Also, connect a DC machine to the drive shaft of the generator, connect the DC machine to a specified DC power supply circuit separated from the output circuit of the generator, and use the DC machine as a generator when the load is below the reference level. Let
When the load exceeds the reference level, the DC machine can be made to function as an electric motor, and its output can be superimposed on the output of the prime mover to drive the generator. Also in this case, when the DC machine is made to function as a generator, it is desirable to regenerate the generated power to the DC power supply circuit.

[0006]

Since the present invention is configured and functions as described above, the power generation load of the generator driven by the prime mover is leveled, and the output of the prime mover is increased even when the load is rapidly increased. The function of the induction machine or the DC machine as a motor compensates for the response delay due to the increase, and drives the generator. Therefore, even in a power system with large load fluctuations, high-quality power with few frequency fluctuations can be stably supplied. When the induction machine or the DC machine functions as a generator, an efficient power stabilizer can be obtained by regenerating the generated power to the AC power circuit or the DC power circuit.

[0007]

Embodiments 1 and 2 of a stable power supply apparatus for a closed circuit power system according to the present invention will be described in detail with reference to FIGS. Embodiment 1 In FIG. 1, 1 is a generator, 2 is a prime mover for driving the generator 1, and the prime mover 2 is an internal combustion engine such as a diesel engine or a gas turbine. The power generated by the generator 1 is supplied to a predetermined power load (not shown) by the generator output circuit 3. Induction machine 4 is attached to the rotating shaft of generator 1.
, And the armature circuit of the induction machine 4 is connected to a predetermined AC power supply circuit 5, for example, a power distribution circuit such as a commercial power supply. In the figure, 21 is a coupling that couples the rotating shafts of the generator 1 and the prime mover 2, and 14 is the generator 1
And a coupling for connecting the respective rotating shafts of the induction machine 4. For example, when the prime mover has a high rotation speed like a gas turbine, or when the induction machine 4 and the AC power supply circuit meet the conditions, etc. Use a transmission that converts speed. If the generator 1, the prime mover 2 and the induction machine 4 are configured to rotate integrally with each other at an appropriate rotation speed, the mutual coupling of the rotating shafts is not limited to that shown in FIG. It goes without saying that it may be configured as or. In addition,
In the figure, illustrations of control and operation functions of the prime mover 2, the generator 1 and the like are omitted.

The operation of the device according to the present invention will be described with reference to FIGS. 2 and 3 with reference to the first embodiment. FIG. 2 shows the outline characteristics of the induction machine 4, in which the horizontal axis represents the rotational speed of the induction machine and the upper half of the vertical axis represents the output torque of the induction machine.
The lower half of the vertical axis is the input (absorption) torque of the induction machine. The vertical line shown in the middle of the horizontal axis in FIG. 2 represents the frequency of the AC power supplied to the induction machine, that is, the synchronous speed of the induction machine 4 determined by the frequency of the AC power supply circuit 5 shown in FIG. hand,
The left side of the synchronous speed shows the motor area corresponding to the sliding speed that is determined by the mechanical load, and the right side of the synchronous speed is the sliding speed that is determined by mechanically forcibly rotating the induction machine at a rotation speed faster than the synchronous speed. The generator area corresponding to is shown. That is, in the induction machine, a mechanical load is coupled to the rotating shaft of the induction machine, and when electric power is supplied, the induction machine drives the mechanical load as an electric motor. On the contrary, when the rotation speed becomes faster than the synchronous speed by being forcibly rotated by the mechanical part connected to the rotating shaft of the induction machine, the induction machine functions as a generator.
It supplies power to the connected electrical circuits. That is, the regenerative operation is performed. In the present invention, it is the prime mover 2 whose load is the generator 1 that regulates the rotation of the induction machine 4, and the generator 1 supplies electric power to a load equal to or less than a predetermined amount, and its rotation speed The rotation speed of the induction machine 4 determined is higher than the synchronous speed determined by the frequency of the AC power supply circuit 5, for example, the induction machine 4
Is rotated at the slip speed indicated by point g in FIG.
Functions as a generator and regenerates generated power to the AC power supply circuit 5. In the above-mentioned state, if the load of the generator 1 suddenly increases and the speed control function of the prime mover 2 cannot cope with it, or if the load constantly increases to fall below the rated rotation speed, the induction machine 4
2 also decreases and becomes slower than the synchronous speed described above, and for example, when the induction machine 4 rotates at a slip speed indicated by point m in FIG. 2, the induction machine 4 receives the AC power supplied from the AC power supply circuit 5. Acting as an electric motor, the induction machine 4 drives the generator 1 by superposing it on the driving force of the prime mover 2.

FIG. 3 shows an example of the operating state of the above-described electric power system. In FIG. 3A, the horizontal axis shows the time transition, and the vertical axis shows the load amount corresponding to the time transition of the electric power system. The horizontal line indicates the load amount at which the induction machine 4 rotates at the synchronous speed determined by the frequency of the AC power supply circuit 5 as a reference load level. That is, the load of the generator 1 is small, and the line a indicating the load amount is below the reference load level, that is, the induction machine 4 operates at a speed faster than the synchronous speed determined by the AC frequency supplied from the AC power supply circuit 5. When driven, the induction machine 4 is driven by the prime mover 2 and functions as a generator. The load a of the generator 1 increases and the line a indicating the load amount is above the reference load level, that is, the rotational speed of the prime mover 2 is lower than the synchronous speed determined by the AC frequency supplied from the AC power supply circuit 5. When the induction machine 4 is driven at a very low speed, the induction machine 4 is driven by the electric power supplied from the AC power supply circuit 5 and functions as an electric motor, and its output is superimposed on the rotational force of the prime mover 2 to generate the electric power of the prime mover 2. It compensates the reduction of rotation and helps drive the generator 1.

FIG. 3B shows the rotation speed of the generator 1 corresponding to FIG. 3A in an enlarged scale on the vertical axis. FIG. 3 (B)
At line A, the generator 1 when the induction machine 4 is not connected
The change in rotation speed of the prime mover 2 is shown. That is, the rotation speed greatly changes with the change of the load amount, and therefore the output voltage and the power generation frequency greatly change when the generator 1 is an AC generator. Further, it can be seen that the line B is a function of the induction machine 4 according to the present invention and the speed fluctuation of the generator is small. If the control function of the prime mover cannot be tracked due to a sudden change in the load of the generator 1, unless the present invention is applied, the rotation speed of the generator 1 fluctuates instantaneously and the quality of the generated power deteriorates. When the present invention is applied, the functions of the generator and the electric motor are converted without inertia in the induction machine 4 with the characteristics shown in FIG. 2, so that the induction machine 4 bears a sudden load fluctuation that affects the prime mover 2. Therefore, the reduction of the rotation speed of the generator 1 is prevented, and the quality deterioration of the generated power of the generator 1 is prevented. In the above description, in the generator region of the induction machine 4, the generated power is regenerated to the AC power supply circuit 5, but an appropriate resistor circuit is connected so that the generated power is consumed by this resistor circuit. Is also good.

Second Embodiment In the first embodiment shown in FIG. 1, an example in which the induction machine 4 stabilizes the operation of the prime mover 2 and the generator 1 in the case of a load change has been described. by the way,
Although not shown, a second embodiment is conceivable in which the induction machine 4 is replaced with a DC machine and the AC power supply circuit 5 is replaced with a DC power supply circuit in the structure of the first embodiment of FIG. Also in the case of the second embodiment configured as described above, when the load exceeds the reference level, that is, when the rotation speed is slower than the reference rotation speed, the DC machine functions as an electric motor, and the load is below the reference level. When that is the case, that is, when the rotation speed becomes higher than the reference rotation speed, the same operation as in the first embodiment can be performed by causing the DC motor to function as a generator similar to regenerative braking. In the case of the present embodiment, the torque due to the increase in the rotation speed applied to the rotating shaft of the DC machine becomes higher than that in the electric motor state determined by the current value due to the applied voltage, and it can be realized by strengthening the field. Further, even when a DC machine is used, the generated power may be consumed by a resistor having an appropriate resistance value in the generator region.

The above description shows the basic method and configuration for realizing the technical idea of the present invention, in which an induction machine or a DC machine having appropriate characteristics corresponding to the characteristics of the load and its necessary conditions. It should be selected and configured appropriately.

[0013]

Since the present invention is constructed and operated as described above, it has the following excellent effects. It is not necessary to equip a load device having a large load fluctuation with a prime mover or a generator having a large rated load and having a function required to absorb the maximum load. When the load is light, the surplus of the prime mover can be regenerated. The induction machine or the DC machine need only have the ability to absorb only the fluctuations with respect to the average load amount. The maximum capacity of the generator and prime mover corresponds to the maximum capacity of the induction machine or DC machine, and it is sufficient if it has the capacity to absorb the average load amount, so the cost of the power generator can be reduced. Since it is possible to cope with a sharp load change, it is possible to supply high-quality power with little frequency change to the load.

[Brief description of drawings]

FIG. 1 is a schematic block diagram illustrating a first embodiment of a stable power supply device for a closed circuit power system according to the present invention.

FIG. 2 is a schematic characteristic diagram showing a slip velocity characteristic of the induction machine shown for explaining the function of the present invention.

3A and 3B are characteristic explanatory diagrams corresponding to a time transition for explaining the function of the embodiment of the present invention, in which FIG. 3A shows a load variation example, and FIG. 3B shows the same FIG. 3 is a rotational speed fluctuation diagram of a generator (motor) corresponding to FIG.

[Explanation of symbols]

 1: Generator 2: Motor 3: Generator output circuit 4: Induction motor 5: AC power supply circuit

Claims (4)

[Claims] 1. A closed circuit power system for supplying required power by a generator driven by a prime mover, wherein an induction machine is connected to a drive shaft of the generator and the induction machine is separated from an output circuit of the generator. When the load is below the reference level, the induction machine functions as a generator, and when the load exceeds the reference level, the induction machine functions as an electric motor and superimposes it on the output of the prime mover. A stable power supply device for a closed circuit power system, characterized in that the generator is driven by a power generator. 2. In a closed circuit power system in which required power is supplied by a generator driven by a prime mover, an induction machine is connected to a drive shaft of the generator and the induction machine is separated from an output circuit of the generator. When the load is below the reference level, the induction machine functions as a generator to regenerate excess energy to the predetermined AC power circuit, and when the load exceeds the reference level. 2. The stable power supply device for a closed circuit power system according to claim 1, wherein the induction machine functions as an electric motor to superimpose on the output of the prime mover to drive the generator. 3. In a closed circuit power system for supplying required power by a generator driven by a prime mover, a DC machine is connected to a drive shaft of the generator and the DC machine is separated from an output circuit of the generator. When the load is below the reference level, the DC machine functions as a generator, and when the load exceeds the reference level, the DC machine functions as an electric motor. A stable power supply device for a closed circuit power system. 4. In a closed circuit power system for supplying required power by a generator driven by a prime mover, a DC machine is connected to a drive shaft of the generator and the DC machine is separated from an output circuit of the generator. When the load is below the reference level, the DC machine functions as a generator to regenerate excess energy to the predetermined DC power supply circuit, and when the load exceeds the reference level. 4. The stable power supply device for a closed circuit power system according to claim 3, wherein the DC machine functions as an electric motor and is superimposed on the output of the prime mover to drive the generator.