JP3356348B2 - Automatic voltage regulator for engine generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic voltage regulator for an engine generator for controlling an output voltage of an AC generator driven by an engine to a predetermined target voltage.

[0002]

2. Description of the Related Art Conventionally, in this type of automatic voltage regulator for an engine generator, the output voltage of the AC generator is detected and the AC generator is controlled so that the detected output voltage becomes a predetermined target voltage. The excitation current flowing through the field winding is controlled.

When an engine generator is used for driving a motor, a large current flows at the time of starting the motor as compared with the time of normal operation. When the voltage is controlled, there is a problem that the output power from the AC generator becomes extremely large and the engine that drives the AC generator stalls.

[0004] Conventionally, in this type of automatic voltage regulator, as disclosed in, for example, Japanese Patent Application Laid-Open No. 58-49097, the decrease in engine speed due to the start of a motor is controlled by the output of an engine generator. Detect from frequency,
It has been proposed that as the output frequency decreases, the detected value of the output voltage used for voltage control increases. In other words, if the engine speed and, consequently, the output frequency of the alternator decrease with the start of the motor, the detected value of the output voltage is increased in accordance with the decrease, thereby increasing the field of the alternator. By reducing the exciting current flowing through the windings, the engine load is reduced and engine stall is prevented.

[0005]

However, in such a conventional automatic voltage regulator, the excitation current, which is a control amount, is corrected after the rotation of the engine actually starts to decrease by starting the motor. Therefore, the responsiveness is poor, and depending on the magnitude of the load applied to the engine when the motor is started, a decrease in the engine rotation cannot be prevented, and the engine may stall.

On the other hand, in order to reliably prevent engine stall, it is only necessary to greatly reduce the exciting current when a decrease in the engine speed is detected, but this makes it impossible to supply a current for starting to the motor. I will. Therefore, when the load power increases at the time of starting the motor or the like, the correction amount when the detection voltage is increased and the excitation current is reduced is determined by subtracting the engine load from the load applied to the engine due to the increase in the load power. It is desirable to set the value to be reduced.

That is, when an excessive load is applied to the engine by starting the motor, not only the output voltage of the AC generator is reduced, but also the power supplied from the AC generator to the motor by the operation of the engine. It is desirable to make the maximum power that can be supplied from the AC generator.

In the above-described conventional device which corrects (increases) the detected voltage in response to a decrease in the engine speed, in order to realize such control, an excessive load applied to the engine at the time of starting the motor is determined by determining the engine speed. , The amount of correction (increase) of the detected voltage and, in turn, the amount of correction (reduction) of the excitation current may be set in accordance with the detection result.

However, in order to detect the decreasing speed of the engine speed as described above, it is necessary to detect the output frequency of the AC generator at least twice at predetermined time intervals and calculate the difference. In such a case, when such control is realized, the response becomes worse.

The present invention has been made in view of such a problem, and can prevent a decrease in engine rotation caused when an excessively large load is temporarily applied to an engine generator, such as when starting a motor, without any delay in response. Moreover, it is an object of the present invention to provide an automatic voltage regulator for an engine generator that can control the output power from the AC generator at that time to the maximum feasible power.

[0011]

According to the first aspect of the present invention, there is provided a voltage detecting means for detecting an output voltage of an AC generator driven by an engine, and the voltage detecting means. Control means for controlling the exciting current flowing through the field winding of the AC generator, so that the output voltage detected at becomes a predetermined target voltage. Current detecting means for detecting a load current flowing from the alternator to the load; and calculating the power consumption of the load from the output voltage detected by the voltage detecting means and the load current detected by the current detecting means. Power consumption calculating means, frequency detecting means for detecting the frequency of the output voltage of the alternator, frequency of the output voltage detected by the frequency detecting means, and output characteristics of the engine in advance. Maximum power calculation means for calculating the maximum power that can be supplied from the AC generator by operating the engine based on the calculation data set in advance, and power consumption and maximum power calculated by the calculation means. Power deviation calculating means for calculating a deviation of each power when the power consumption is greater than the maximum power, and a deviation between the power consumption and the maximum power calculated by the power deviation calculating means. Accordingly, the control means includes a control amount correction means for reducing an exciting current flowing through a field winding of the AC generator.

According to a second aspect of the present invention, in the automatic voltage regulator for an engine generator according to the first aspect, the control amount correction means is configured to control the AC voltage in accordance with a deviation between the power consumption and the maximum power. It is characterized in that the target voltage of the generator is reduced. Next, according to a third aspect of the present invention, in the automatic voltage control apparatus for an engine generator according to the first aspect, the control amount correction means is configured to control the voltage in accordance with a deviation between the power consumption and the maximum power. The output power detected by the detection means
It is characterized by increasing the pressure .

[0013]

In the automatic voltage regulator for an engine generator according to the first aspect of the present invention, the voltage detector detects the output voltage of the AC generator driven by the engine, and the controller controls the output voltage of the AC generator. The excitation current flowing through the field winding of the AC generator is controlled so that the detected output voltage becomes a predetermined target voltage.

In the present invention, the current detecting means detects a load current flowing from the AC generator to the load, and the power consumption calculating means detects the output voltage detected by the voltage detecting means and the output voltage detected by the current detecting means. The power consumption of the load is calculated from the obtained load current. Still further, in the present invention, the frequency detecting means detects the frequency of the output voltage of the AC generator, and the maximum power calculating means is set in advance according to the detected frequency of the output voltage and the output characteristics of the engine. Based on the calculated data, the maximum power that can be supplied from the AC generator by operating the engine is calculated.

The power deviation calculating means compares the power consumption calculated by each of these calculating means with the maximum power, and calculates a deviation between these powers when the power consumption is larger than the maximum power. The correction means reduces the exciting current flowing through the field winding of the AC generator by the control means according to the deviation between the calculated power consumption and the maximum power.

That is, in the automatic voltage regulator for an engine generator according to the present invention, the power consumption of the load is calculated from the output voltage of the AC generator and the load current, and the power consumption is set in advance according to the output characteristics of the engine. Using the data for calculation, calculate the maximum power that can be supplied from the AC generator by operating the engine, and when the power consumption is greater than the maximum power, reduce the excitation current of the AC generator according to the deviation of each of these powers By doing so, engine stall caused by an increase in load is prevented.

Next, in the automatic voltage regulator for an engine generator according to the second aspect, the control amount correction means reduces the target voltage of the AC generator according to a deviation between the power consumption and the maximum power. . That is, according to the present invention, when the power consumption of the load is larger than the maximum power that can be supplied from the AC generator by operating the engine, the target voltage is reduced in accordance with the deviation, whereby the AC power generation controlled by the control unit is controlled. Reduce the exciting current of the machine.

[0018] In the automatic voltage regulator of the engine generator according to claim 3, the control amount correction means, according to the difference between the power consumption and the maximum power, detection by the voltage detecting means
Increase the output voltage output . That is, in the present invention,
When the power consumption of the load is greater than the maximum power that can be supplied from the AC generator by operating the engine, control is performed by increasing the output voltage of the AC generator detected by the voltage detecting means according to the deviation. The means reduces the exciting current of the alternator controlled.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 2 is a schematic configuration diagram showing the configuration of the entire engine generator of the present embodiment. As shown in the figure, in the engine generator of the present embodiment, a transformer 10 for detecting an output voltage of an AC generator 12 and a load current for detecting a load current flowing from the AC generator 12 to a load such as a motor. Detector 1
1 and an automatic voltage regulator (hereinafter simply referred to as AVR) that outputs a control signal for controlling the output voltage from the AC generator 12 to a target voltage based on the output signals from the transformer 10 and the detector 11. ) 14 and a power MOSFET 1 switched by a control signal from AVR 14
6, an exciting device 18 for controlling an exciting current flowing through the field winding 12L of the AC generator 12 is provided. Further, the excitation device 18 is provided with the engine 2 that drives the AC generator 12.
The starter 22 is connected to a battery 24 via a switch SW together with the starter 22, and the power is supplied from the battery 24 to supply an exciting current to the field winding 12L.

Although not shown, the AVR 14 is also connected to the battery 24 via the switch SW, and receives power from the battery 24 to generate a control signal. Further, the starting device 22 receives the power supply from the battery 24 at the time of starting the engine and starts the engine 20, and after starting the engine, generates a DC voltage by the rotation of the engine 20 to charge the battery 24.

Next, as shown in FIG. 1, the AVR 14 generates a voltage signal VACj corresponding to the output voltage of the AC generator 12 by converting an AC voltage obtained through the transformer 10 into a DC voltage. A voltage detection circuit 26 as voltage detection means, and an output signal VAC from the voltage detection circuit 26
j and an AC generator 12 output from a subtraction circuit 50 described later.
And a filter circuit 28 for removing a signal component (that is, a noise component) of a signal having a frequency equal to or higher than a certain frequency of an output signal from the differential amplifier circuit 27. A comparator 30 for comparing the output of the filter circuit 28 with a carrier wave (sawtooth wave) output from the pulse generation circuit 29;
Power MOSFET 16
And a gate drive circuit 32 for switching the power MOSFET 16 of the excitation device 18 so that the voltage signals VACj and VACO match (that is, the output voltage of the AC generator 12 becomes the target voltage). Note that the differential amplifier circuit 27 and the filter circuit 2
8, the comparator 30, and the gate drive circuit 32 correspond to control means of the present invention.

The AVR 14 has a frequency detection circuit as frequency detection means for converting the input signal from the transformer 10 into a voltage to generate a voltage signal Vfj representing the frequency f of the output voltage of the AC generator 12. 34, AC generator 1
2, a reference voltage generating circuit 44 for generating a reference voltage VO representing a target voltage (rated voltage) to be output from the alternator 12, a voltage signal Vi corresponding to the load current based on an output signal from the detector 11. , The voltage signals VACj and Vi output from the current detection circuit 52, the voltage detection circuit 26, and the current detection circuit 52, respectively.
FIG. 3 shows a power calculation circuit 54 as a power consumption calculation means for calculating the power consumption of the load (motor) from the phase difference and the power factor of each of the signals, and the output characteristics of the engine 20. Power data storage unit 56 storing such power data, and output frequency f of AC generator 12 output from frequency detection circuit 34 from power data storage unit 56.
The power value corresponding to the voltage signal Vfj representing the maximum power is read, and this is output as the maximum power value (that is, the maximum power) that can be supplied from the AC generator 12 at the present time. The power value (maximum power) output from the power generation unit 58 and the actual power consumption calculated by the power calculation circuit 54 are compared in magnitude, and when the power consumption is larger than the maximum power, the difference between these powers is calculated. And a correction voltage calculation unit 60 as a power deviation calculation means for calculating a correction amount ΔVO of the reference voltage VO according to the difference.
And the reference voltage V output from the reference voltage generation circuit 44
A correction signal ΔVO is subtracted from O, and a voltage signal VAC input to the differential amplifier circuit 27 as a target voltage of the AC generator 12 is obtained.
A subtraction circuit 50 as a control amount correction means for generating O 2 is provided.

The power data shown in FIG. 3 is for calculating the maximum power that can be supplied from the AC generator 12 based on the output frequency of the AC generator 12 corresponding to the engine speed. Are set in advance based on the torque characteristics of That is, the maximum power that can be supplied from the AC generator 12 changes according to the engine torque at that time, and the engine torque changes according to the engine speed. The power data for obtaining the maximum power that can be supplied by the AC generator 12 is set in advance from the output frequency of the generator 12, and the upper limit power generation unit 58 directly searches for the power data, thereby The maximum power corresponding to the twelve output frequencies is determined.

In the engine generator of the present embodiment configured as described above, when the switch SW is turned on, AV
The battery 2 is connected to the R14, the exciting device 18, and the starting device 22.
4 is connected. Then, first, the starting device 22 operates to start the engine 20, and the engine 20 starts driving the AC generator 12. Then, when the rotation of the engine 20 increases and reaches the rated frequency, the starter 22 stops operating, and the engine 20 enters autonomous operation.

On the other hand, on the AVR 14 side, when the frequency of the output voltage of the AC generator reaches the rated frequency with the start of the engine 20, the target voltage of the AC generator 12 is set as
The rated voltage is set. For this reason, a control signal for controlling the output voltage of the AC generator 12 to the rated voltage is output from the AVR 14, whereby the power MOSFET 16 of the exciter 18 is switched. Then, the exciting current is supplied from the battery 24 to the field winding 12L of the AC generator 12 by this switching operation, and the output voltage of the AC generator 12 is controlled to the rated voltage.

When the rated voltage, which is the intended target voltage, is output from the alternator 12 in this manner, this state is maintained thereafter, and a constant voltage is supplied to the load connected to the alternator 12. However, when a motor is connected as a load to the alternator 12, a large current flows through the motor when the motor is started.
When the load applied to the engine 20 becomes excessive, the engine rotation decreases, and in some cases, the engine 20 stalls.

However, in the AVR 14 of the present embodiment, the power calculation circuit 54 calculates the power consumption of the load based on the voltage signals VACj and Vi output from the voltage detection circuit 26 and the current detection circuit 52, and generates an upper limit power generation. Based on the power data stored in the power data storage unit 56 and the voltage signal Vfj representing the output frequency f of the AC generator 12 output from the frequency detection circuit 34, the unit 58 operates the engine 20 to operate the AC generator 12 And when the power consumption is larger than the maximum power, the correction voltage calculation unit 60 calculates the reference voltage VO according to the difference between these powers.
Is calculated, and the subtraction circuit 50 generates a voltage signal VACO representing the target voltage by subtracting the correction amount ΔVO from the reference voltage VO.

Therefore, when the load current increases when the motor is started and its power consumption exceeds the maximum power that can be supplied from the engine generator, the output voltage becomes equal to the reference voltage VO.
The excitation current of the AC generator 12 is controlled so that the voltage becomes lower than the rated voltage obtained by subtracting the correction amount ΔVO from the above.

For this reason, according to the present embodiment, when the load supplied with the electric power from the AC generator 12 becomes excessive, such as when the motor is started, and the rotation of the engine 20 decreases, the engine 20 Can be reduced to prevent the rotation of the engine 20 from decreasing.

Further, in the present embodiment, the increase of the load at the time of starting the motor or the like is determined not by the output frequency of the AC generator 12 but by the power consumption of the load as in the conventional device, and the excitation of the AC generator 12 is performed. Since the current is reduced, the engine load can be reduced before the engine rotation actually starts to decrease, and engine stall can be reliably suppressed without a response delay.

Further, a reference voltage V for determining the exciting current
O is reduced and corrected in accordance with the deviation between the power consumption of the load and the maximum power that can be supplied from the AC generator 12 by the operation of the engine 20. Therefore, the AC generator 12 is Can be driven. Therefore, the maximum power that can be supplied from the engine generator can be supplied to a load such as a motor connected to the AC generator 12.

In this embodiment, when the power consumption of the load exceeds the maximum power, the reference voltage VO representing the target voltage to be output from the AC generator 12 is reduced. Even if the voltage signal VACj representing the actual output voltage output from 26 is increased,
The same effects as in the present embodiment can be obtained.

In the present embodiment, when calculating the maximum power corresponding to the engine rotation, the power data set in advance according to the output characteristics of the engine 20 is used. Alternatively, the output characteristic of the engine 20 may be stored, and the maximum power may be calculated using the output characteristic.

[0034]

As described above, in the automatic voltage regulator for an engine generator according to the first aspect, the power consumption of the load is calculated from the output voltage of the AC generator and the load current, and the engine power is calculated in advance. Calculate the maximum power that can be supplied from the AC generator by operating the engine using the calculation data set in accordance with the output characteristics of the power supply, and when the power consumption is larger than the maximum power, Reduce the exciting current of the alternator.

For this reason, according to the device of the first aspect,
When the load that receives the power supply from the AC generator becomes excessive, such as when starting the motor, and the rotation of the engine is reduced, the load applied to the engine is reduced to prevent the rotation of the engine from decreasing. Can be prevented.

Further, according to the present invention, the increase in the load at the time of starting the motor or the like is determined not from the output frequency of the AC generator but from the power consumption of the load as in the conventional device, and the exciting current of the AC generator is reduced. Therefore, the engine load can be reduced before the engine rotation actually starts to decrease due to the increase in power consumption, and the engine stall can be reliably suppressed without a response delay.

Further, since the exciting current is corrected to be reduced in accordance with the difference between the power consumption of the load and the maximum power that can be supplied from the AC generator by operating the engine, the AC power is generated by making full use of the engine output. Machine can be driven.
Therefore, the maximum power that can be supplied from the engine generator can be supplied to a load such as a motor connected to the AC generator.

Next, in the automatic voltage regulator for an engine generator according to the present invention, when the power consumption of the load is larger than the maximum power that can be supplied from the AC generator by the operation of the engine, the load is adjusted according to the deviation. Then, the exciting current of the AC generator is reduced by reducing the target voltage when the control means controls the exciting current of the AC generator. In the automatic voltage regulator for an engine generator according to the third aspect, when the power consumption of the load is larger than the maximum power that can be supplied from the AC generator by operating the engine, the voltage detection is performed in accordance with the deviation. The exciting current of the AC generator controlled by the control means is reduced by increasing the output voltage detected by the means. For this reason, according to the apparatus described in claim 2 and claim 3, similarly to the apparatus described in claim 1, it is possible to reliably suppress a decrease in engine speed with an increase in load without a response delay. Moreover, the maximum power that can be supplied from the engine generator can be supplied to a load such as a motor connected to the AC generator.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an automatic voltage regulator according to an embodiment.

FIG. 2 is a schematic configuration diagram illustrating a configuration of an entire engine generator of the embodiment.

FIG. 3 is an explanatory diagram illustrating power data stored in a power data storage unit according to the embodiment.

[Explanation of symbols]

10 Transformer 11 Detector 12 Alternator
12L: Field winding 18: Excitation device 20: Engine 22: Starting device 24: Battery 26: Voltage detection circuit 27: Differential amplification circuit 28:
Filter circuit 29 ... Pulse generation circuit 30 ... Comparator 32
... Gate drive circuit 34 ... Frequency detection circuit 44 ... Reference voltage generation circuit
50: subtraction circuit 52: current detection circuit 54: power calculation circuit 56:
Power data storage unit 58: Upper limit power generation unit 60: Correction voltage calculation unit

Claims (3)

(57) [Claims] 1. A voltage detecting means for detecting an output voltage of an AC generator driven by an engine, and a voltage detecting means for the AC generator so that the output voltage detected by the voltage detecting means becomes a predetermined target voltage. Control means for controlling an exciting current flowing through a field winding; and an automatic voltage regulator for an engine generator, comprising: a current detecting means for detecting a load current flowing from the AC generator to a load; and the voltage detecting means. Power consumption calculating means for calculating the power consumption of the load from the output voltage detected by the above and the load current detected by the current detecting means; and frequency detecting means for detecting the frequency of the output voltage of the AC generator. And the frequency of the output voltage detected by the frequency detecting means,
Maximum power calculation means for calculating the maximum power that can be supplied from the alternator by operating the engine based on calculation data set in advance according to the output characteristics of the engine; Power deviation calculating means for comparing the calculated power consumption with the maximum power, and calculating a deviation of each power when the power consumption is larger than the maximum power; and the power consumption calculated by the power deviation calculating means. And control amount correction means for reducing the exciting current flowing through the field winding of the alternator in accordance with the deviation between the maximum power and the maximum power. Adjustment device. 2. The engine generator according to claim 1, wherein the control amount correction means decreases the target voltage of the AC generator according to a deviation between the power consumption and the maximum power. Voltage regulator. 3. A control amount correction means which is detected by said voltage detection means according to a deviation between said power consumption and said maximum power.
2. The automatic voltage regulator for an engine generator according to claim 1, wherein the output voltage is increased.