JPH0415384B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for controlling an engine-driven generator.

(Prior art) When starting loads such as lamps or induction motors, an inrush current of about 5 to 10 times the rated current flows, so in order to start these heavy loads with an engine-driven generator, it is necessary to The output capacitance is required to be about 2 to 3 times the load capacitance.
Therefore, when using a generator with a small capacity or a capacity comparable to the load capacity, the engine speed will drop significantly due to the inrush current when the load is applied, and the engine will stall or the engine speed will remain balanced at low speed. If it does not rise, problems will occur. For example, even if a generator has a capacity of 35 KVA (28 KW), simultaneous starting can only start loads (motors) up to 11 KW, and the generator cannot fully utilize its capacity.

Further, since conventional generators are configured to always operate in a rated state, for example, when a motor is used as a load, it is not possible to arbitrarily set the rotation speed of the motor. For this reason, the temperatures of ventilation and cooling fans used in underground mines, etc. are sufficiently lowered, and the generator maintains its rated state even though it does not require much power, which reduces energy consumption. So it was wasted.

(Objective of the Invention) The present invention was proposed in view of the above points, and it is possible to easily start up to a load with a rated capacity equivalent to that of a generator, even if the load has a large inrush current, and furthermore, if necessary, the load can be started. The purpose of this invention is to provide an engine-driven generator control method that can achieve optimal operating conditions depending on usage conditions.

That is, in the present invention, when the load is applied, the engine speed is minimized, and the setting circuit is set as the lowest minimum value such that the output voltage of the generator becomes a value corresponding to the load characteristics at the minimum engine speed. Then, this lowest value is given to the comparator as a reference voltage for engine speed setting, and the set value is given to an automatic voltage regulator as a reference voltage for generator voltage control. The voltage from the conversion circuit is input to a comparator and compared, the engine rotation speed and the output voltage of the generator are reduced, the output voltage of the generator is detected by the voltage detection circuit, and the load current value is detected by the I/V conversion circuit. detects that the output voltage of the I/V conversion circuit is within the reference voltage of the reference voltage generation circuit,
If the output voltage of the voltage detection circuit exceeds the reference voltage input to the automatic transformer regulator, there is a surplus in the output of the generator, so the U/D counter outputs an incremented binary signal, The D/A conversion circuit outputs a reference voltage boosted from the initial reference voltage, and the comparator compares the output voltage of the F/V conversion circuit with the reference voltage, and if the reference voltage is larger, the actuator is turned off. The above objective is achieved by driving the engine, increasing the rotational speed of the engine, increasing the output voltage of the generator, and shifting to rated operation.

(Structure of the Invention) FIG. 1 is a circuit configuration diagram showing an embodiment embodying the present invention. In the figure, reference numeral 1 denotes an alternator (hereinafter simply referred to as "generator") driven by an engine (not shown), and its output terminal is connected to a load 2 such as an induction motor. Further, W ₁ and W ₂ are excitation windings of the generator 1 that are in a differential relationship with each other, and a current transformer CT ₀ , a reactor RT, a diode D, and an AVR (automatic voltage regulator) 15 are the excitation windings of the generator 1. An excitation circuit is configured that operates to maintain the output voltage at a predetermined voltage. on the other hand,
The current transformer CT provided on the load line, the I/V conversion circuit 3, the reference voltage generation circuit 4, and the comparator 5 constitute a circuit that determines whether the load current has settled down to a predetermined value. The transformer PT, voltage detection circuit 7, and comparator 8 connected to the output terminal of the generator 1 constitute a circuit that determines whether the voltage drop amount of the generator 1 is within an allowable range. Next, the output signals of these comparators 5 and 8 are both input to an AND circuit 9, and an oscillation circuit 10 is operated by the output of this AND circuit. Further, the U/D counter (up-down counter) 12 counts the pulses generated by the oscillation circuit 10 (in this embodiment, only up-counting is performed) and sends out a binary output.
The initial value is preset by the setting circuit 11, the count output is given to the D/A conversion circuit 13 and also given to the setting circuit 11 at the same time, and the output of the U/D counter 12 is applied to the generator 1. When the value reaches the rating, the U/D counter 12 is stopped by the setting circuit 11.

Next, the analog output of the D/A conversion circuit 13 is provided to the AVR 15 as a reference voltage for voltage control via the function generation circuit 14, and is also input to the comparator 16 as a reference voltage for setting the engine speed. Also, comparator 1
A signal corresponding to the rotational speed of the generator 1 is applied from the transformer PT via the F/V conversion circuit 6 to the other input terminal of the comparator 16, and the output of the comparator 16 is applied to the engine via the amplifier 17. It is given as a control signal to the actuator 18 that drives the governor.

FIG. 2 shows an example of a relay sequence circuit for giving a start signal to the setting circuit 11, and the start signal is obtained from the contact _MCa3 of the contactor MC operated by the start switch _S1 . Note that _S2 is a stop switch, _MCa1 is another contact for turning on the load 2, and _MCa2 is a self-holding contact for maintaining the operation of the start switch _S1 .

In FIG. 1, when a start signal is given to the setting circuit 11 when a load is applied, the U/
The D counter 12 is preset to the lowest value at which the engine speed is the minimum value that can drive the engine and the output voltage of the generator 1 is a value corresponding to the load characteristics at that speed. /A conversion circuit 13 converts the value into an analog value and supplies it to the comparator 16 as a reference voltage for setting the engine speed as described above, and to the function generation circuit 1.
AVR15 as reference voltage for voltage control via 4
given to. Note that the initial value of the U/D counter 12 is preset to a low value by first lowering the engine speed and generator output voltage.
This is to reduce the rush current when the load is applied, and to lighten the load on the engine. In addition, function generation circuit 1
4 is for setting the relationship between the engine speed and the generator output voltage according to the load characteristics (constant torque load, square reduced torque load, etc.).

Therefore, the comparator 16 detects the engine speed at that time from the F/V conversion circuit 6 and converts it into a D/A converter.
Compare with the reference voltage given from the conversion circuit 13,
The engine governor is feedback-controlled by the actuator 18 so that the two match. Similarly, the AVR 15 also controls the excitation current of the generator 1 based on the reference voltage applied via the function generation circuit 14 so that the generator output voltage becomes a predetermined voltage. That is, the engine speed and generator output voltage are unilaterally controlled by the output value of the U/D counter 12.

On the other hand, the output current (negative liquid current) and output voltage of the generator 1 detected by the current transformer CT and the transformer PT are outputted to the output voltage from the I/V conversion circuit 3 and the reference voltage generated by the comparators 5 and 8, respectively. The reference voltage of the circuit 4 and the output voltage from the voltage detection circuit 7 are output from the function generation circuit 14.
It is determined whether the output voltage is normal or not by comparing it with the AVR reference voltage, and the output voltage from the I/V conversion circuit 3 is within the reference voltage of the reference voltage generation circuit 4, and the The output voltage
If it exceeds the AVR reference voltage, it is normal;
It is determined that the generator 1 has a margin, and in this case, a signal is output from the comparators 5 and 8 to the AND circuit 9, and the oscillation circuit 10 operates via the AND circuit 9, causing the U/D counter 12 to step forward. The engine speed and generator output voltage are gradually increased. In other words, in the case of a load such as an induction motor, when the rotation of the motor approaches the synchronous speed and becomes normal rotation, the inrush current will decrease, so if the load current is below a predetermined value, load 2 will become a generator. In addition, by monitoring the amount of drop in generator output voltage, it is possible to determine whether the load on generator 1 is excessive, so that the load current is equal to the predetermined value. It is determined that the generator 1 and the load 2 are in a normal matching state when two conditions are satisfied: the amount of drop in the generator output voltage is within a predetermined value, and the amount of drop in the generator output voltage is within a predetermined value.

While confirming that the load 2 is properly matched with the generator 1, the engine speed and the generator output voltage are increased to bring the engine to the rated state. When the output of the U/D counter 12 reaches the rated value, the setting circuit 11 stops the U/D counter 12. Therefore, even under a heavy load with a rated capacity comparable to the generator capacity, the engine driving the generator 1 will not be overloaded, and the engine will not stall or run at low speeds as in the past. The inconvenience caused when the rotational speed does not increase while remaining balanced will be resolved. In addition, in the function generation circuit 14, in the case of a constant torque load, T = k ₁ (V/) ² = constant ... (1) In the case of a square-law reduction torque load, since the torque T is proportional to the square of the frequency, The relationship between the frequency (engine speed) and the generator output voltage V is set so that T=k ₂ (V/) ² =k ₃ ² ...(2), and the D/A conversion circuit 1
Add correction to one of the analog values given from 3. In addition, in order to further reduce the load on the engine when a load is applied, the generator output voltage V determined by the above equations (1) and (2) can be multiplied by a coefficient of 1 or less (variable depending on the type of load). You can set it to .

Figure 3 shows a working space A in a mine etc. using the present invention.
The rotation speed of the fan F for ventilation is controlled. In the figure, fan F is driven by an induction motor with load 2, while a temperature sensor 19 is provided in work space A, and the detection signal of temperature sensor 19 is sent to comparator 21. By comparing it with the set value of the temperature setting circuit 20, an up-down signal is given to the setting circuit 11. In addition, the other configurations are as follows:
It is similar to that of FIG.

The operation at the time of starting the load 2 is the same as that shown in FIG.
When the set temperature of 0 is exceeded, an up signal is given from the comparator 21 to the setting circuit 11, the output value of the U/D counter 12 is increased, the rotation of the fan F is accelerated, and the temperature of the work space A is lowered. . Further, when the temperature of the work space A decreases, the opposite operation is performed, and as a result, the work space A is maintained at a constant temperature. In the case of a fluid device such as a fan, the load is a square reduction torque load, so the function generating circuit 14 is adapted to the load characteristics of the square reduction torque, and therefore the fan F can be operated efficiently.

(Effects of the Invention) As described above, in the engine-driven generator control method of the present invention, the engine speed is minimized when the load is applied, and the output voltage of the generator is adjusted to the load at the minimum engine speed. Set the lowest value in the setting circuit as the lowest value that corresponds to the characteristics, give this lowest value to the comparator as the reference voltage for engine speed setting, and use the set value as the reference voltage for generator voltage control. On the other hand, the voltage from the F/V conversion circuit that detects the engine speed is input to a comparator and compared, and the engine speed and generator output voltage are reduced. is detected by the voltage detection circuit, and the load current value is detected by the I/V conversion circuit, and the output voltage of the I/V conversion circuit is within the reference voltage of the reference voltage generation circuit, and the output voltage of the voltage detection circuit is If the reference voltage input to the automatic voltage regulator is exceeded, there is a margin in the output of the generator, so the U/D counter outputs a counted-up binary signal, and the D/A conversion circuit outputs an incremented binary signal. outputting a reference voltage boosted from a reference voltage, the comparator compares the output voltage of the F/V conversion circuit with the reference voltage, and drives the actuator if the reference voltage is larger;
This system increases the engine speed and the output voltage of the generator to bring it up to rated operation.Even if the load has a large inrush current, it can easily reach a load with the same rated capacity as the generator. It has the effect of being able to start and, if necessary, realizing optimal operating conditions depending on the usage status of the load.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention;
FIG. 2 is a circuit diagram showing an example of a circuit for generating a start signal, and FIG. 3 is a configuration diagram showing an example of application of the present invention. 1... Generator, 2... Load, 3... I/V conversion circuit, 4... Reference voltage generation circuit, 5, 8, 16...
...Comparator, 6...F/V conversion circuit, 7...
Voltage detection circuit, 9...AND circuit, 10...Oscillation circuit, 11...Setting circuit, 12...U/D counter, 13...D/A conversion circuit, 14...Function generation circuit, 15...AVR , 17...amplifier, 18...
...actuator, CT...current transformer, PT...transformer.

Claims (1)

[Claims] 1. A start signal when applying a load is given to the setting circuit, and a binary signal is generated from the U/D counter using an initial value preset so that the engine rotation speed reaches the minimum rotation speed. It outputs to the D/A conversion circuit and also outputs it to the setting circuit to apply feedback, and outputs the initial reference voltage converted to an analog value from the D/A conversion circuit to the comparator and function generation circuit, and the rotation of the engine is performed. Compare the output voltage of the F/V conversion circuit that detects the number with the initial reference voltage, and if the initial reference voltage is small, drive the actuator with the output from the comparator to reduce the engine rotation speed, an I/I converting the initial reference voltage into an initial reference output voltage corresponding to the minimum rotational speed of the engine and outputting it from the function generating circuit to an automatic voltage regulator to lower the output voltage of the generator and detecting the load current; When the output voltage of the V conversion circuit is within the reference voltage of the reference voltage generation circuit, and the output voltage of the voltage detection circuit that detects the output voltage of the generator exceeds the reference output voltage input to the automatic voltage regulator. Since there is a margin in the output of the generator, the U/D counter outputs a counted up binary signal, the D/A conversion circuit outputs a reference voltage boosted from the initial reference voltage, and the comparator outputs a reference voltage boosted from the initial reference voltage. compares the output voltage of the F/V conversion circuit with the reference voltage, and if the reference voltage is large, drives the actuator to increase the engine rotation speed, and the automatic voltage regulator is connected to the function generating circuit. A method for controlling an engine-driven generator, characterized in that the output voltage of the generator is increased by a reference output voltage that is boosted from the initial reference output voltage inputted through the generator, and the output of the generator is shifted to rated operation.