JP5130143B2 - Inverter generator - Google Patents

Description

  The present invention relates to an inverter generator, and more particularly to an inverter generator that includes a power generation unit that is driven by an engine and that controls the engine speed in accordance with load power.

  The alternating current output from the power generation unit driven by the engine is once converted into direct current by a converter composed of a thyristor bridge, and switched based on a PWM signal generated using a reference sine wave of a target output voltage waveform and a carrier. An inverter generator that drives an element to convert the direct current into alternating current of a predetermined frequency (commercial frequency) and outputs the alternating current is well known. As an example, the technique described in Patent Document 1 below can be cited. .

In the technique described in Patent Document 1, the conduction angle of the thyristor is detected, and the engine speed is controlled so that the conduction angle becomes the target conduction angle.
JP-A-11-308896

  In the technique described in Patent Document 1, as described above, the estimated value of the load power is obtained from the conduction angle of the thyristor of the converter, and the engine speed is controlled based on the estimated value. However, when the alternator output voltage changes transiently, Since the engine rotation fluctuation is transmitted as it is, it is difficult to accurately estimate the load power particularly in a light load. Therefore, the responsiveness of the engine speed control is not always sufficient.

  Accordingly, an object of the present invention is to solve the above-described problems, calculate an estimated value of load power from a power factor or the like instead of a thyristor conduction rate, and calculate a target engine speed based on the estimated value to control the engine speed. It is an object to provide an inverter generator that improves the responsiveness of the inverter.

  In order to solve the above-described problem, in claim 1, an engine including a throttle valve that is opened and closed by an actuator, a power generation unit driven by the engine, and an alternating current output from the power generation unit is converted into a direct current. In an inverter generator comprising a converter for converting to a converter, an inverter for converting a direct current output from the converter into an alternating current and outputting it to a load, and an actuator control means for controlling the operation of the actuator. Voltage / current detection means for detecting AC voltage and current output from the inverter, power factor calculation means for calculating a power factor based on the detected voltage and current, at least the detected current and the Load power estimated value calculating means for calculating an estimated value of load power supplied to the load based on the calculated power factor; And a target speed determining means for determining a target speed of the engine based on the calculated estimated value of the load power, and the actuator control means is configured so that the actuator reaches the determined target speed. The operation was controlled.

  In the inverter generator according to claim 2, the load power estimated value calculation means multiplies the detected current, the calculated power factor, and a rated output voltage, and the product is estimated for the load power. Configured to be value.

  In the inverter generator according to claim 1, the AC voltage and current output from the inverter are detected, the power factor is calculated based on the detected voltage and current, and at least the detected current is calculated. The estimated value of the load power supplied to the load is calculated based on the calculated power factor, the target engine speed is determined based on the calculated estimated load power value, and the determined target engine speed is obtained. The actuator is configured to control the operation of the actuator that opens and closes the throttle valve at the same time. By calculating the estimated load power from the power factor instead of the thyristor conductivity, the load power can be estimated even for light loads. The value can be calculated with high accuracy, and the target engine speed is calculated based on the calculated value to control the actuator, thereby improving the response of the engine speed control.Further, since the estimated value of the load power is calculated including the power factor, the engine speed is not increased unnecessarily, and the fuel efficiency can be improved.

  The inverter generator according to claim 2 is configured to multiply the detected current, the calculated power factor, and the rated output voltage, and to set the product as an estimated value of the load power. In addition, the estimated value of the load power can be calculated with higher accuracy.

  The best mode for carrying out an inverter generator according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a block diagram generally showing an inverter generator according to an embodiment of the present invention.

  In FIG. 1, reference numeral 10 denotes an inverter generator. The generator 10 includes an engine (internal combustion engine) 12 and has a rated output of about 2.6 kW (26 A at AC 100 V). The engine 12 is an air-cooled engine and is a spark ignition type, and its throttle valve 12a is opened and closed by a throttle motor (actuator) 12b comprising a stepping motor and is started by a recoil starter (not shown).

  A circular stator (not shown) is fixed near the cylinder head of the engine 12, and there are three-phase output windings (main windings) composed of U, V, and W phases that constitute the engine power generation unit 14. 14a and three single-phase windings 14b, 14c, and 14d are wound.

  A rotor (not shown) that also serves as a flywheel of the engine 12 is arranged outside the stator, and a permanent magnet (not shown) is attached in the radial direction so as to face the winding 14a and the like. A plurality of pairs are attached while alternating the magnetized magnetic poles.

  By rotating the permanent magnet of the rotor around the stator, three-phase (U, V, W-phase) AC power is output (generated) from the three-phase output winding 14a, and the single-phase output winding Single-phase AC power is output from 14b, 14c, and 14d.

  The three-phase AC power output (power generation) from the output winding 14a of the engine power generation unit 14 is input to the control board (print board) 16 via the U, V, and W terminals 14e, and the converter 20 mounted thereon. Is input. The converter 20 includes three thyristors (SCR) and three diodes DI that are bridge-connected, and converts the three-phase alternating current output from the engine power generation unit 14 into direct current by controlling the conduction angle of the thyristor. To do.

  An RCC (Ringing Choke Converter) power supply (DC stabilized power supply) 22 is connected to the positive and negative outputs of the converter 20, and the rectified DC power is supplied to the three thyristors as operating power. Supply. A smoothing capacitor 24 for smoothing the direct current output from the converter 20 is connected to the subsequent stage of the RCC power supply 22.

  An inverter 26 is connected to the subsequent stage of the smoothing capacitor 24. The inverter 26 includes a circuit in which four FETs (field effect transistors, switching elements) are bridge-connected, and is output from the converter 20 by controlling conduction / non-conduction of the four FETs as will be described later. Direct current is converted into alternating current of a predetermined frequency (specifically, a commercial frequency of 50 Hz or 60 Hz).

  The output of the inverter 26 is output from an output terminal 34 through a choke coil 30 composed of an LC filter for removing harmonics and a noise filter 32 for removing noise, and is supplied to an electric load 36 through a connector (not shown). It is made free.

  The control board 16 includes a CPU (Central Processing Unit) 40. The CPU 40 is composed of 32 bits, and controls the conduction angle of the thyristor of the converter 20 through a thyristor (SCR) driver (drive circuit) 40a, and controls conduction / non-conduction of the FET of the inverter 26 through a gate driver 40b. The operation of the throttle motor 12b is controlled via the motor driver 40c. The CPU 40 includes an EEPROM (nonvolatile memory) 40d.

  The output of the single-phase first output winding 14b is sent to the control board 16 via the sub terminals 14b1 and 14b2, and is input to the control power generation unit 14b3, where the operating power 5V of the CPU 40 is generated. The output of the sub terminal 14b1 is sent to the NE detection circuit 14b4, where it is converted into a pulse signal and sent to the CPU 40. The CPU 40 counts the output of the NE detection circuit 14b4 and detects the rotational speed NE of the engine 12.

  The output of the second output winding 14c is sent to the full-wave rectifier circuit 14c1, where it is full-wave rectified to generate an operating power source such as the throttle motor 12b. The output of the third output winding 14d is sent to the ignition circuit 12c of the engine 12 and used as an ignition power source for the spark plug 12d.

  The CPU 40 includes first and second voltage sensors 40e and 40f. The first voltage sensor 40e generates an output corresponding to the DC voltage output from the converter 20 at the subsequent stage of the RCC power supply 22, and the second voltage. The sensor 40 f generates an output corresponding to the AC voltage output from the inverter 26 at the subsequent stage of the inverter 26. The outputs of the first and second voltage sensors 40e and 40f are input to the CPU 40.

  Further, the CPU 40 includes a current sensor 40g, and the current sensor 40g generates an output corresponding to the current output from the inverter 26, in other words, when the electrical load 36 is connected.

  The output of the current sensor 40g is input to the CPU 40 and also input to the overcurrent limiter 40h. The overcurrent limiter 40h is composed of a logic circuit (hardware circuit) independent of the CPU 40. When the current detected by the current sensor 40g exceeds the allowable limit value, the output of the gate driver 40b is stopped and the output of the inverter 26 is stopped. Temporarily set to zero.

  The CPU 40 inputs the outputs of the first and second voltage sensors 40e and 40f and the current sensor 40g, and based on them, performs PWM control of the FET of the inverter 26, controls the operation of the throttle motor 12b, and further controls overcurrent. Restrict.

  FIG. 2 is a waveform diagram for explaining the PWM control performed by the CPU 40.

  The PWM control of the FET of the inverter 26 will be described with reference to FIG. 2. The CPU 40 has a reference sine wave at a predetermined frequency (that is, commercial frequency 50 Hz or 60 Hz) of a target AC output voltage waveform (indicated by a broken line below). The PWM signal (PWM waveform), that is, the duty ratio (= on time) according to PWM (Pulse Width Modulation) compared with a carrier (for example, 20 kHz carrier) by a comparator (not shown) based on the signal wave) (t / cycle T) A variable pulse train is generated and output via the gate driver 40b.

  In FIG. 2, the lower broken line shows the target output voltage waveform. The period T (step) of the PWM signal (PWM waveform) is actually much shorter, but is exaggerated in FIG. 2 for convenience of understanding.

  Further, the CPU 40 determines the opening degree of the throttle valve 12a so that the target rotational speed is determined according to the AC output determined by the electric load 36, and outputs the A-phase and B-phase output pulses of the throttle motor 12b. The calculated value is supplied from the output terminal 40c1 to the throttle motor 12b via the motor driver 40c, and its operation is controlled.

  FIG. 3 is a flowchart showing the operation of the CPU 40. The illustrated program is executed every control period (step) defined from the carrier frequency, more specifically, every 50 μsec, assuming that the frequency of the target output voltage waveform is 50 Hz, for example.

  In the following, based on the outputs of the second voltage sensor 40f and the current sensor 40g in S10, the AC voltage and current output from the inverter 26 (current that is passed through the electrical load 36 when the electrical load 36 is connected). ) Is detected.

  Next, in S12, the detected voltage and current phase difference θ is calculated, and in S14, the power factor cos θ is calculated from the calculated phase difference.

Next, in S16, an estimated load power (an estimated value of load power) is calculated. The estimated load power is calculated according to the following formula.
Estimated load power = Rated output voltage (V) × Detected current (A) × Power factor (cos θ)
In the above, the rated output voltage is AC 100 (V).

  Next, the process proceeds to S18, and the target rotational speed of the engine 12 is determined based on the calculated estimated load power. More specifically, the table value indicating the characteristic in FIG. 4 is searched from the calculated estimated load power, and the target engine speed is determined.

  Next, in S20, the operation of the throttle motor 12b is controlled so that the determined target engine speed is reached. More specifically, the operation of the throttle motor 12b is feedback-controlled so that the engine speed detected by the NE detection circuit 14b4 becomes the target engine speed.

  FIG. 5 is a time chart for explaining the processing of FIG.

  In the illustrated example, the load is a mercury lamp. Since the power factor of the mercury lamp is as low as 0.3 until the current is stabilized, the work of the engine 12 indicated by the product of the voltage, current and power factor is small, so the engine speed is low at the beginning. Then, as the current supplied to the load decreases with time, the power factor gradually increases toward 1.0.

  In this embodiment, the estimated load power including the power factor is calculated, and the target engine speed is determined and controlled based on the estimated load power. Therefore, as shown in FIG. The speed can be increased or decreased in proportion to the rate, thereby improving the response of the engine speed control.

  Further, since the estimated value of the load power is calculated including the power factor, when the power factor is as low as 0.3, the engine speed is also controlled to a low value. In other words, since the engine speed is not increased unnecessarily, fuel efficiency can be improved.

  As described above, in this embodiment, the engine 12 having the throttle valve 12a that is opened and closed by the actuator (throttle motor) 12b, the power generation unit 14 driven by the engine 12, and the power generation unit are output. A converter 20 that converts alternating current into direct current, a switching element (FET), an inverter 26 that converts direct current output from the converter 20 into alternating current and outputs it to a load, and an actuator that controls the operation of the actuator 12b In the inverter generator 10 provided with a control means (CPU 40), voltage / current detection means (voltage sensor 40f, current sensor 40g, CPU 40, S10) for detecting the alternating voltage and current output from the inverter, Power factor calculation to calculate the power factor cos θ based on the detected voltage and current Means (CPU 40, S12, S14) and a load power estimated value for calculating an estimated value (estimated load power) of load power supplied to the load based on at least the detected current and the calculated power factor cos θ Calculation means (CPU 40, S16) and target rotation speed determination means (CPU 40, S18) for determining a target rotation speed of the engine 12 based on the calculated estimated value of load power, and the actuator control means Is configured to control the operation of the actuator so as to achieve the determined target rotational speed (CPU 40, S20). In other words, instead of the thyristor conductivity of the converter 20, the load power is calculated from the power factor or the like. By calculating the estimated value, it is possible to accurately calculate the estimated value of the load power even at light loads, etc. By controlling the actuator 12b calculates a target engine rotational speed, it is possible to improve the responsiveness of the engine speed control. Further, since the estimated value of the load power is calculated including the power factor, the engine speed is not increased unnecessarily, and the fuel efficiency can be improved.

  Further, the load power estimated value calculating means is configured to multiply the detected current, the calculated power factor and the rated output voltage, and to set the product as the estimated value of the load power. In addition, the estimated value of the load power can be calculated with higher accuracy.

  In the above description, the FET is used as the switching element of the inverter. However, the present invention is not limited to this, and an IGBT (insulated gate bipolar transistor) or the like may be used.

1 is a block diagram generally showing an inverter generator according to an embodiment of the present invention. It is a wave form diagram explaining the PWM control which CPU shown in FIG. 1 performs. 3 is a flowchart showing processing of output voltage restriction control performed by a CPU shown in FIG. 1. 3 is an explanatory diagram showing a table characteristic of the target engine speed used in the processing of the flowchart of FIG. It is a time chart explaining the process of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Inverter generator, 12 Engine (internal combustion engine), 12a Throttle valve, 12b Throttle motor (actuator), 14 Engine power generation part, 14a Three-phase output winding, 20 Converter, 26 Inverter, 36 Electric load, 40 CPU, 40a Thyristor (SCR) driver, 40b gate driver, 40c motor driver, 40d EEPROM, 40e, 40f voltage sensor, 40g current sensor

Claims (2)

  An engine including a throttle valve that is opened and closed by an actuator, a power generation unit driven by the engine, a converter that converts alternating current output from the power generation unit into direct current, and a switching element, and is output from the converter Voltage / current for detecting AC voltage and current output from the inverter in an inverter generator including an inverter that converts direct current to alternating current and outputs it to a load, and actuator control means for controlling the operation of the actuator Detection means; power factor calculation means for calculating a power factor based on the detected voltage and current; and load power supplied to the load based on at least the detected current and the calculated power factor. A load power estimated value calculating means for calculating an estimated value, and the engine based on the calculated load power estimated value. Together with and a target rotational speed determining means for determining a target rotational speed, said actuator control means, inverter generator and controls the operation of the actuator such that the target rotational speed said determined.   The load power estimated value calculation means multiplies the detected current, the calculated power factor, and a rated output voltage, and uses the product as an estimated value of the load power. Inverter generator.

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