JP2003047296A - Inverter apparatus for engine generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter apparatus for an engine generator which can detect the number of revolutions of an engine accurately at all times, regardless of the rectifying motion of a rectifying circuit. SOLUTION: A revolution detector 35a includes a comparator 351 which compares the AC output Vout of a control power source 34a with reference voltage Vref, a reference pulse generator 354, a cycle measuring instrument 352 which measures the cycle of AC output Vout, and a switching circuit 355 which switches the reference voltage Vref into 0 V or specified minus voltage. A CPU 30a energizes an SCR driver 37a and controls the angle of conductivity of each thyristor so that the output voltage of a thyristor bridge circuit 311a may be kept stably, based on the output voltage detected by a voltage detecting circuit 3111. The CPU 30a turns on a switching transistor Tr, synchronizing with the energization timing of an SCR driver 37a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine generator inverter device, and more particularly, to an engine generator inverter device capable of accurately detecting an engine speed.

[0002]

2. Description of the Related Art In an engine generator in which an AC generator is rotated by an engine to generate AC power having a commercial frequency, the engine is rotated in a relatively high rotation range so that the AC generator outputs high-output AC power. After being converted into direct current by the rectifier circuit, it is converted into alternating current of commercial frequency by the inverter device and output.

Variations in output voltage due to load variations and other external factors are suppressed by appropriately controlling the engine speed. Further, in order to approximate the output waveform to a sine wave, it is necessary to suppress the output fluctuation of the rectifier circuit. A thyristor bridge circuit is widely used as a rectifier circuit, and its output fluctuation is performed by dynamically controlling the conduction angle of a thyristor forming the bridge.

[0004]

In the conventional engine generator, in order to detect the engine speed based on the output of the AC generator, the output of the AC generator is transformed into a low voltage, and the cycle of this AC output is changed. The engine speed is obtained by measurement.
However, in such a measuring method, when the conduction angle of the thyristor is controlled in the rectifier circuit, the waveform of the AC output Vout is distorted in the vicinity of the zero cross, as shown in FIG. Therefore, if the cycle of the AC output Vout is measured at the timing of zero cross, the measurement result includes an error corresponding to the distortion, and there is a technical problem that the engine speed cannot be accurately detected.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide an inverter device for an engine generator capable of always accurately detecting the engine speed regardless of the rectifying operation of a rectifying circuit.

[0006]

In order to achieve the above-mentioned object, the present invention provides an inverter unit for an engine generator for controlling an output of an AC generator driven by an engine to a predetermined AC voltage. Means for detecting the engine speed based on the AC output of the generator, means for controlling the engine speed, means for rectifying the AC output, and rectification of the rectifying means based on output fluctuations of the rectifying means. A means for controlling the operation, wherein the means for detecting the engine speed detects the engine speed based on the rectangular pulse and means for comparing the AC output with a reference voltage to generate a rectangular pulse. And a means for displacing the reference voltage, wherein the means for displacing the reference voltage determines whether or not the means for controlling the rectification operation by the rectification means is in operation. According to the above-mentioned characteristic of differentiating the reference voltage according to the above, since the reference voltage compared with the AC output is variable, even if a certain level of the AC output is distorted in synchronization with the rectifying operation in the rectifying means, By displacing the reference voltage to a level where no distortion occurs, a rectangular pulse accurately synchronized with the AC output can be obtained. Therefore, the engine speed can be accurately obtained by measuring the period of the rectangular pulse.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a multiplex inverter device for an engine generator that is an embodiment of the present invention.

The engine generator 2 includes two systems of three-phase main windings 2A and 2B and is driven by the engine 1.
The output of the engine 1 is controlled by a throttle (not shown) whose opening is adjusted by the step motor 5. An inverter circuit 3a is provided at the output stage of the main windings 2A and 2B.
(Master) and 3b (slave) are respectively connected. The output stages of the master 3a and the slave 3b are connected to the series / parallel switching unit 4.

A primary coil 71 of the transformer 7 is connected to the output stage of the three-phase main winding 2B. Transformer 7
On the secondary side of the three sub-coils 72 (72a, 72b,
72c) is coupled as a secondary coil. The subcoils 72a and 72b are inverter power supply coils, and supply drive power to the control power supply 34a of the master 3a and the control power supply 34b of the slave 3b, respectively. Sub coil 72
c is a charging coil for supplying a charging current to an internal battery (not shown), or an external DC power supply coil for supplying a DC voltage to an external socket (not shown).

As described above, in this embodiment, a part of the output of the generator 2 is taken out through the transformer 7 and used as an internal power source such as an inverter power source or a battery charging power source. By setting the turn ratio between the primary coil 71 and the secondary coil 72 of the transformer 7, only the required power can be taken out from the main output of the generator 2 and the power generation efficiency can be improved.

Further, in the present embodiment, the secondary side of the transformer 7 is composed of a plurality of subcoils 72a, 72b, 72c, so the number of turns of each subcoil is determined according to the power consumption of the plurality of electric loads driven by the internal power supply. If set, it will be possible to accurately extract the power required for the internal power supply from the main output of the alternator.

In the master 3a, the three-phase main winding 2A
Output of the rectification smoothing circuit 31a, the inverter circuit 32a
And the serial / parallel switching unit 4 via the filter circuit 33a. The rectifying / smoothing circuit 31a includes a thyristor bridge circuit 311a and a smoothing circuit 312a. The inverter circuit 32a includes a field effect transistor (FET) bridge 321a and a smoothing circuit 322a.

The SCR driver 37a controls the conduction angle of the thyristor which constitutes the thyristor bridge circuit 311a. The rotation detector 35a detects the engine speed based on the AC output of the control electrode 34a. The governor control unit 36a, based on the detected engine speed,
The step motor 5 is controlled.

Since the configuration of the slave 3b is the same as that of the master 3a except that the rotation detector 35a and the governor controller 36a are not mounted, its description is omitted.

A communication line 8 is provided between the inverter circuits 3a and 3b.
, And control signals and synchronous signals for synchronously operating each other are transmitted and received via the communication line 8.
The slave 3b transmits the result of conduction angle control by the SCR driver 37b of itself to the master 3a. The master 3a
The optimum rotation speed of the engine is determined based on the track record of conduction angle control by its own SCR driver 37a and the track record of conduction angle control by the SCR driver 37b of the slave 3b, and this is notified to the governor control section. Switching between serial connection and parallel connection of two inverter circuits will be described. Figure 2
FIG. 3 is a circuit diagram showing details of the serial / parallel switching unit 4. The serial / parallel switching unit 4 can be configured by a toggle switch, and when the switch is switched to the contact a side, the output voltage (for example, 120V) of the master 3a is output between the output terminals T1 and T2. , Between the output terminals T2 and T3, the output voltage of the slave 3b (for example, 120
V) is output, and as a result, an output voltage (240 V) that is twice the output voltage of the master 3a and the slave 3b is obtained between the output terminals T1 and T3. That is, the master 3a
And the slave 3b are connected in series.

When the switch is switched to the contact b side, no voltage is output between the output terminals T1 and T2, and the master 3 is connected only between the output terminals T2 and T3.
a and the output voltage by the slave 3b (for example, 120
V) is output. As a result, the output voltage (120 V) of each of the master 3a and the slave 3b is output without change between the output terminals T2 and T3, and the output (for example, 2
kW) appears twice as much (4 kW). That is, the master 3a and the slave 3b are connected in parallel.

Next, the rotation speed detection unit 3 of the master 3a
The operation of detecting the engine speed by 5a will be described. Figure 3
FIG. 4 is a block diagram showing a circuit configuration of the rotation speed detection unit 35a, the thyristor bridge circuit 311a, and the smoothing circuit 312a, and the same symbols as those used above represent the same or equivalent portions.

The rotation speed detector 35a is provided with the control power source 34.
Based on the AC output Vout and the reference pulse, a comparator 351 that compares the AC output Vout of a with a reference voltage Vref, a reference pulse generator 354 that generates a reference pulse that is sufficiently faster than the output pulse of the comparator 351. Cycle measuring unit 35 for measuring the cycle of the AC output Vout
2 and a switching circuit 355 for switching the reference voltage Vref to 0V or a predetermined negative voltage.

In the above configuration, the measurement result by the cycle measuring unit 352 becomes the information representative of the engine speed. The thyristor bridge circuit 311a includes a voltage detection unit 3111 that detects the output voltage of the thyristor bridge circuit 311a, and the detection result is provided to the CPU 30.

The CPU 30a of the master 3a energizes the SCR driver 37a based on the output voltage detected by the voltage detection circuit 3111 so that the output voltage of the thyristor bridge circuit 311a is stably maintained. Feedback control the conduction angle of. The CPU 30
a is a switching transistor T of the switching circuit 355 in synchronization with the energizing timing of the SCR driver 37a.
Conduct r.

In such a configuration, when the output of the thyristor bridge circuit 311a is stable and the SCR driver 37a is not energized, the switching transistor Tr of the switching circuit 355 remains cut off. Therefore, since the non-inverting input (reference voltage Vref) of the comparator is maintained at 0V as shown in FIG. 4, the output of the comparator 351 is inverted at the zero-cross timing of the AC output Vout as in the conventional technique.

On the other hand, when the SCR driver 37a is energized and the conduction angle of the thyristor of the thyristor bridge circuit 311a is controlled, the AC output Vout is distorted near 0V as shown in FIG.

However, in this embodiment, since the switching transistor Tr of the switching circuit 355 becomes conductive in synchronization with the conduction angle control of the thyristor, the non-inverting input (Vref) of the comparator causes the collector current flowing through the resistor R1 and the switching. The voltage corresponding to VBE of the transistor (in this embodiment, about 12 to 13% of the amplitude) is shifted to the negative side from 0V.

Therefore, the output of the comparator 351 is inverted at a timing without distortion, which is deviated from the vicinity of the zero cross of the AC output Vout. As a result, the AC output Vou
Even if the waveform of t is distorted near 0 V under the influence of the conduction angle control of the thyristor, a rectangular pulse accurately synchronized with the AC output can be obtained.

[0025]

According to the present invention, since the reference voltage compared with the AC output is variable, even if a certain level of the AC output is distorted in synchronism with the rectifying operation of the rectifying means, the reference voltage becomes a level at which no distortion occurs. By displacing, a rectangular pulse accurately synchronized with the AC output can be obtained. Therefore, the engine speed can be accurately obtained by measuring the period of the rectangular pulse.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a multiplex inverter device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing details of a serial / parallel switching unit 4.

FIG. 3 is a block diagram showing a circuit configuration of a rotation speed detector, a thyristor bridge circuit, and a smoothing circuit.

FIG. 4 is a signal waveform diagram of a main part of FIG.

5 is a signal waveform diagram of a main part of FIG.

FIG. 6 is a waveform diagram for explaining problems of the conventional technique.

[Explanation of symbols]

1 ... Engine, 2 ... Engine generator, 3a (master) ...
Inverter circuit, 3b (slave) ... Inverter circuit,
4 ... Series / parallel switching section, 5 ... Step motor, 7 ... Transformer, 31a, 31b ... Rectifying and smoothing circuit, 32a, 32b
... Inverter circuit, 33a, 33b ... Filter circuit, 3
4a, 34b ... Control power supplies 34a, 34b ..., 35a ... Rotation detector, 36a ... Governor controller, 37a, 37b ... SC
R driver, 71 ... Primary coil, 72 (72a, 72
b, 72c) ... Sub coil

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3G093 AA16 AB05 BA27 DA01 DB19                       DB28 EA03 EB09 EC02                 5H590 AA22 CA07 CC01 CC24 CD01                       CD03 EB07 FC14 FC15 HA27                       HB02 JA02 JB08 JB18

Claims (4)

[Claims] 1. An inverter device for an engine generator that controls the output of an AC generator driven by an engine to a predetermined AC voltage, and means for detecting an engine speed based on the AC output of the AC generator. The engine rotation speed is detected by: a means for controlling the engine speed; a means for rectifying the AC output; and a means for controlling a rectification operation of the rectification means based on an output fluctuation of the rectification means. The means includes means for comparing the AC output with a reference voltage to generate a rectangular pulse, means for detecting an engine speed based on the rectangular pulse, and means for displacing the reference voltage, The means for displacing the reference voltage changes the reference voltage according to whether or not the means for controlling the rectifying operation of the rectifying means is operating. Power generator inverter device. 2. The engine generator according to claim 1, wherein the rectifying means is a thyristor bridge circuit, and the means for controlling the rectifying operation controls a conduction angle of a thyristor of the thyristor bridge circuit. Inverter device. 3. The transformer further comprising a transformer having a primary winding connected to the alternating current output of the alternator, wherein the means for detecting the engine speed is an alternating current induced in the secondary winding of the transformer. The engine generator inverter device according to claim 1 or 2, wherein the engine speed is detected based on the output. 4. A system comprising a first inverter device including the engine speed control unit and a second inverter device not including the engine speed control unit, wherein the first inverter device has its own rectification. 4. The inverter device for an engine generator according to claim 1, wherein the engine speed is controlled based on the rectifying operation of the second inverter device and the rectifying operation of the second inverter device.