JP2003056377A - Engine controlling method in cogeneration system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controlling method for realizing accurate high-speed response of the number of revolutions of an engine in compliance with a power load and preventing unnecessary power supply such as causing a reverse current. SOLUTION: A pulse signal is obtained from teeth cut in the circumference of a flywheel disc 2 in the engine 1 by means of a solenoid type rotation speed detector 7. In an output regulation circuit 6, the pulse signal is converted into a direct-current voltage proportional to a pulse frequency by means of a rotational speed converter, and the direct-current voltage is compared with a previously given voltage equivalent to an engine rotational speed command position by means of an engine rotational speed control circuit. A throttle 5 of the engine 1 is regulated so that a difference obtained from this comparison is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cogeneration system for obtaining electric power by rotating an electric generator by an engine and at the same time extracting heat energy from the cooling water, and more particularly to a method for controlling the engine.

[0002]

2. Description of the Related Art Such a conventional cogeneration system attempts to effectively utilize what has been abandoned as waste heat in commercial electric power by extracting the thermal energy of fuel as electric power and hot water. This is a known technique. Further, a hybrid type in which solar power generation is combined is also known.

In the method of using the electric power generated by the normal cogeneration system, the load power supply switch is switched to the commercial power system to cope with the power load that exceeds the output limit of the generator. Type) and the commercial power system, which is always linked to the power demand without output switching for output limits.

In the case of this interconnection type, reverse power flow to commercial power occurs when power is generated beyond the power load. However, in the case of low power generation cost such as solar power generation, reverse power flow occurs and power is sold. Is also acceptable. However, in a cogeneration system in which fuel is burned to generate electricity by an engine, it is not a good idea to have a reverse flow when considering the purchase price of electricity on the commercial power side.

Further, in the case where it is not linked with the commercial power system like the self-sustaining type, the electric power generated by the AC generator can be directly used without passing through the power interconnection type inverter. In that case, in order to keep the frequency of the alternator constant, it is necessary to control the engine speed to be constant even if the electric power load changes. Although a method of utilizing electric power by a commercial power system and a change-over switch has been put to practical use even in a self-sustaining demand type, there is a drawback that an instantaneous blackout occurs at the time of changeover.

As a method for controlling the number of revolutions of the engine to be constant, for example, a constant speed operation system is known which keeps the vehicle speed constant even in an automobile. This counting of the number of revolutions of the engine is detected from the generator output voltage, and is detected as a voltage fluctuation in each cycle of the generator, and its control accuracy and high-speed response characteristics need to be so high from the practicality of the automobile. There is no.

[0007]

In the power interconnection type as described above, the power interconnection type inverter used in the photovoltaic power generation system completely satisfies the electrical requirements necessary for the power interconnection and is used in many cases. Therefore, its price is relatively low. However, if this is used in a cogeneration system that generates power from an engine, the inverter for photovoltaic power generation operates to always generate maximum power in the generator by maximum power tracking control (MPPT), which causes reverse power flow. Supply the required power.

Further, in order not to supply unnecessary electric power so as not to generate reverse power flow, it is necessary to make the engine speed respond with high accuracy and high speed in accordance with the electric power load. Such a control method is known. Has not been done.

When the electric power generated by the AC generator is directly used without passing through the power interconnection type inverter like the self-sustaining demand type, the engine speed is varied in order to keep the frequency constant. Even so, it is necessary to control with high accuracy and constant.

Further, the engine in the cogeneration system is required to have a function of automatically starting and stopping in response to fluctuations in the electric power load in order to save fuel, but in a normal engine including an automobile, a user starts and stops the engine. Since the operation can be performed by a human sense, the control of the engine of the cogeneration system is required to be performed by a simpler method.

Therefore, the present invention relates to a cogeneration system that automatically operates by a simple method in which the engine speed is made to respond with high accuracy and high speed in accordance with the electric power load, and unnecessary electric power that causes reverse power flow is not supplied. An object is to provide an engine control method.

[0012]

According to a first aspect of the present invention, there is provided a method for controlling an engine in a cogeneration system, wherein a pulse is generated from a tooth carved on a circumference of a flywheel disc 2 of an engine 1 by an electromagnetic speed detecting device 7. A signal is obtained, and in the output adjusting circuit 6, the pulse signal is converted into a DC voltage proportional to the pulse period by the rotation speed conversion device, and the DC voltage is compared with the voltage corresponding to the engine rotation speed command position given in advance by the engine rotation speed control circuit. However, the throttle 5 of the engine 1 is adjusted so as to reduce the difference.

In the engine control method in the cogeneration system according to the second aspect of the present invention, the output adjusting circuit 6 reverses the commercial power to the maximum power tracking control (MPPT) of the power interconnection type inverter 23. The output of the engine 1 is adjusted according to the load current so as not to generate a tidal current.

In the engine control method in the cogeneration system according to the third aspect of the present invention, the starter circuit 4 detects the voltage generated by the generator 21 connected to the engine 1, and the rotation speed of the engine 1 increases to detect a predetermined voltage. Then, the starter motor 3 is turned off.

An engine control method in a cogeneration system according to a fourth aspect of the present invention is an auto choke circuit.
When the thermistor 13 detects that the temperature of the engine 1 is lower than a predetermined temperature when the engine 1 is started by 12, the choke valve 11 closes the air intake port of the engine 1 and gradually opens the choke valve 11 after a certain period of time. Is.

[0016]

According to the first aspect of the invention, a pulse signal is obtained from the teeth carved on the circumference of the flywheel disc 2 of the engine 1 by the electromagnetic rotation speed detecting device 7, and the output adjusting circuit 6 Since the pulse signal is converted into a DC voltage proportional to the pulse period by the rotation speed conversion device, the number of revolutions of the engine 1 is counted as a voltage variation for each pulse period from the teeth engraved on the circumference of the flywheel disc 2. Detected by fast response.

Further, the engine speed control circuit compares the direct current voltage with a voltage corresponding to the engine speed command position given in advance and adjusts the throttle 5 of the engine 1 so as to reduce the difference. Then, the engine speed is controlled according to the power load, and is controlled to a constant engine speed when not linked with the commercial power system.

According to the second aspect of the invention, in consideration of the operation of the maximum power follow-up control (MPPT) of the power interconnection type inverter 23, the output current adjusting circuit 6 prevents the reverse flow of the commercial power from the load current. Since the output of the engine 1 is adjusted in accordance with the above, the rotation speed of the engine 1 is controlled according to the electric power load, and unnecessary electric power is not supplied.

According to the third aspect of the present invention, the starter circuit 4 detects the voltage generated by the generator 21 connected to the engine 1. When the rotation speed of the engine 1 increases and a predetermined voltage is detected, the starter motor 3 is turned off. Therefore, the starter motor 3 is turned off by automatically confirming the start of the engine 1 by the indispensable generator 21 without requiring any special confirmation means.

According to a fourth aspect of the invention, an auto choke circuit is provided.
When the thermistor 13 detects that the temperature of the engine 1 is lower than a predetermined temperature when the engine 1 is started by 12, the choke valve 11 closes the air intake port of the engine 1, and after a certain period of time, the choke valve 11 is gradually opened. Even when the engine 1 is cold, the fuel mixture ratio is increased to start the engine reliably, and the choke valve 11 is automatically opened to prevent a decrease in fuel consumption.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

The engine control method in the cogeneration system of the present invention is shown in the schematic circuit diagram of FIG. 1, in which the engine 1 rotates the generator 21 to generate electric power, and at the same time, heat energy is taken out as hot water from the cooling water or exhaust gas. Is. The power system is an interconnected type that is always linked with the commercial power system and can meet the power demand without switching the switch with respect to the output limit.

The engine 1 is a three-cylinder reciprocating type engine,
The flywheel disc 2 is directly connected to the engine 1,
A large number of metal carved teeth are provided on the circumference of the flywheel disc 2, and the starter motor 3 bites and rotates the teeth to start the engine 1 when the engine 1 is started.

The starter motor 3 is controlled and driven by the starter circuit 4, and the starter circuit 4 turns on the starter motor 3 by a start signal and detects the voltage generated by the generator 21 connected to the engine 1 to detect the voltage of the engine 1. When the rotation speed increases and a predetermined voltage is detected, the starter motor 3 is turned off.

A relay for turning off the starter motor 3 is provided in the starter circuit 4, and a generator is connected to a drive terminal of this relay.
When the power generation circuit 21 is connected, the rotation speed of the engine 1 increases, the voltage increases, and the minimum relay drive current flows, the relay operates to open the contact, thereby turning off the starter motor 3. The relay operating current differs depending on the type of relay used, and it is necessary to make adjustments such as inserting a series resistor if necessary.

The fuel for the engine 1 is shown as LPG (LPG), but the fuel is assumed to be gas fuel such as city gas, wood-based gas or biogas, and liquid fuel such as light oil or alcohol. .

The LP gas is supplied to the engine 1 after being mixed with air by the gas mixer 5 as a throttle, and the LP gas supply amount of the gas mixer 5 is controlled by the output adjusting circuit 6 to adjust the output of the engine 1.

A pulse signal is input to the output adjusting circuit 6 from an electromagnetic rotation speed detecting device 7 provided in the vicinity of the circumference of the flywheel disc 2.

The electromagnetic type rotation speed detecting device 7 is an electromagnetic pickup mounted with a slight distance to the teeth on the circumference of the flywheel disk 2, and the magnetic circuit constant is changed every time the metal teeth approach. The pulse signal is electrically output by changing, and a pulse signal of the number of teeth is generated by one rotation of the flywheel disc 2.

For example, the pulse number pn is given by the following expression when the engine 1 has a rotational speed of 1,800 rpm and the number of teeth is 100. pn = 1800/60 × 100 = 3kHz

In the output adjusting circuit 6, the pulse signal as the value of the rotation speed from the electromagnetic rotation speed detecting device 7 is converted into a DC voltage (Nr) signal by the rotation speed converting device. The rotation speed conversion device is commonly called FV conversion, and is a circuit that generates a DC voltage (Nr) proportional to the pulse period of the pulse signal.

Further, in consideration of the operation of the maximum power follow-up control (MPPT) of the power interconnection type inverter 23, that is, the maximum current at the rotation speed of the generator 21 is expected to flow, the output adjusting circuit 6 The output of the engine 1 is adjusted according to the load current so as not to generate reverse power flow to commercial power.

Therefore, the current sensor 8 is provided in the circuit of the power load 30, and the current value i of the current sensor 8 is input to the output adjusting circuit 6. This current value i is converted into a voltage Nc corresponding to the engine speed command position by the correlation as shown in FIG.

In the engine speed control circuit of the output adjusting circuit 6, the voltage (Nr) as the value of the actual speed from the electromagnetic speed detecting device 7 and the engine given in advance obtained from the current sensor 8 are given. The gas mixer 5 of the engine 1 is adjusted so as to reduce the difference by comparing with the voltage Nc corresponding to the rotation speed command position.

A choke valve 11 is provided in front of the gas mixer 5 of the engine 1. The choke valve 11 has a low ignition capacity at a normal mixture ratio concentration of LP gas and air when the cooling water of the engine 1 is at a low temperature. In order to prevent the rotation speed of No. 1 from rising smoothly, the air intake of the engine 1 is closed to increase the mixing ratio of LP gas and air to improve the ignition performance.

The choke valve 11 is controlled by an auto choke circuit 12, and in order to ensure the operation reliability, a small servomotor converts the rotational movement into a linear movement using a screw to open and close the air intake port.

A temperature signal is input to the auto choke circuit 12 from the thermistor 13 attached to the engine 1. The thermistor 13 detects the cooling water temperature of the engine 1.

In the auto choke circuit 12, when the engine 1 is started, the temperature of the engine 1 is a predetermined temperature (6 degrees Celsius in this embodiment).
When the thermistor 13 detects that the temperature is lower than 0 degree, the air intake port of the engine 1 is closed by the choke valve 11, and after a lapse of a certain time (about 3 minutes), the servo motor is intermittently reversed and the choke valve 11 is gradually opened. Open.

A generator 21 is connected to the engine 1 via a flywheel disc 2.

The generator 21 is a PM type three-phase AC generator (AC
In G), unlike other types of generators, it is optimal for the present invention because it has a high operating efficiency at a light load. The generator 21 may be directly connected to the engine 1 and rotated at the same number of revolutions, but in consideration of the fuel efficiency of the engine 1 and the power generation characteristics of the generator 21, it is preferable to reduce the speed of the generator 21 and connect the same.

The rectifier 22 is connected to the generator 21. The rectifier 22 rectifies the AC voltage from the generator 21 into three-phase full-wave rectification and converts it into a DC voltage (AC / DC converter).

A power interconnection type inverter 23 is connected to the rectifying device 22. The power interconnection type inverter 23 is widely used in a photovoltaic power generation system for converting a DC voltage into a single-phase three-wire system 100V / 200V, and completely satisfies the electrical requirements necessary for commercial power interconnection. However, the maximum power tracking control (MPPT) causes a reverse flow when the amount of power generated is greater than that of the power load 30, and sells the power. Generator 21
When is connected, it operates so that the maximum current at that rotation speed flows.

The rectifier 22 and the power interconnection type inverter
The reference numeral 23 allows the frequency fluctuation of the generator 21, and it is necessary to convert the alternating current into the direct current and convert it again into the alternating current matched with the frequency of the commercial power system.

The power interconnection type inverter 23 is connected to the commercial power and the power load 30 via a distribution board or the like. The power load 30 is power consumption for private use, and the load changes suddenly.

When not connected to the commercial power system, the rectifier 22 and the power interconnection type inverter 23 are omitted and the power load 30 is connected to the generator 21, so that the facility cost is reduced. Further, the current sensor 8 is also omitted, and the voltage Nc corresponding to the engine speed command position given in advance by the predetermined frequency of the generator 21 is input to the output adjusting circuit 6 to directly control the frequency of the generator 21 to be constant.

[0046]

According to the invention of claim 1, a pulse signal is obtained from the teeth carved on the circumference of the flywheel disk of the engine by the electromagnetic type rotation speed detecting device, and the output adjusting circuit
The pulse signal is converted to a DC voltage proportional to the pulse period by the rotation speed converter, and the engine speed is detected as a voltage change at each pulse period from the teeth engraved on the circumference of the flywheel disk with a fast response. Therefore, the power generation cost is reduced by detecting the engine speed with high accuracy according to the electric power load and not supplying unnecessary electric power that causes reverse power flow.

Further, the engine speed control circuit compares the DC voltage with the voltage corresponding to the engine speed command position given in advance, and adjusts the engine throttle to reduce the difference. The power generation cost is reduced by making the engine respond to the engine speed corresponding to the above and not supplying unnecessary electric power that causes reverse power flow. Further, when the engine is not linked with the commercial power system, the engine speed is controlled to be constant, so that the frequency of the generator can be directly controlled to be constant with high speed response.

According to the second aspect of the present invention, in consideration of the operation of the maximum power tracking control (MPPT) of the power interconnection type inverter, the output current adjusting circuit prevents the reverse flow of the commercial power from the load current. The power generation cost is reduced by adjusting the engine output in accordance with the above, controlling the engine speed according to the power load, and supplying no unnecessary power.

According to the invention of claim 3, the voltage generated by the generator connected to the engine is detected by the starter circuit, and when the engine speed increases and a predetermined voltage is detected, the starter motor is turned off and a special confirmation is made. Without requiring any means, the starter motor is turned off by automatically checking the start of the engine by the indispensable generator, so that the automatic operation can be performed by a simple method.

According to the fourth aspect of the invention, when the thermistor detects that the temperature of the engine is lower than the predetermined temperature at the time of starting the engine by the auto choke circuit, the choke valve closes the air intake port of the engine to cool the engine. Even if it is, increase the fuel mixture ratio and start it securely,
It can be operated automatically by a simple method. Also, after a certain period of time has passed, the choke valve is gradually opened, and the choke valve is automatically opened to prevent a reduction in fuel consumption.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram showing an embodiment of an engine control method in a cogeneration system.

FIG. 2 is a graph showing a correlation between a current value of a current sensor in the output adjustment circuit and a voltage corresponding to an engine speed command position.

[Explanation of symbols]

1 engine 2 Flywheel disc 3 Starter motor 4 Starter circuit 5 Gas mixer as a throttle 6 Output adjustment circuit 7 Electromagnetic rotation speed detection device 11 Choke valve 12 Auto choke circuit 13 Thermistor 21 generator 23 Power interconnection type inverter

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/06 310 F02D 41/06 310 41/14 320 41/14 320B F02M 21/02 F02M 21/02 L 301 301C 301G 301L 21/04 21/04 AF terms (reference) 3G093 AA16 AB03 BA15 BA19 BA21 CA01 CA05 DA01 DA05 DA06 DA12 DA14 EA09 EA10 EB08 EC02 FA04 3G301 HA22 HA27 JA03 KA01 KA10 LA02 LC03 ND01 NE03 PA11A08Z PE01A08 PA12Z

Claims (4)

[Claims] 1. A pulse signal is obtained from teeth engraved on a circumference of a flywheel disk of an engine by an electromagnetic rotation speed detecting device, and in an output adjusting circuit, the pulse signal is proportional to a pulse period by a rotation speed converting device. An engine control method in a cogeneration system in which a DC voltage is used, a DC voltage is compared with a voltage corresponding to an engine speed command position given in advance by an engine speed control circuit, and an engine throttle is adjusted so as to reduce the difference. 2. The engine output is adjusted according to the load current so as not to generate reverse power flow to the commercial power by the output adjusting circuit in anticipation of the operation of the maximum power tracking control (MPPT) of the power interconnection type inverter. Control method for cogeneration system. 3. An engine control method in a cogeneration system in which a starter circuit detects a voltage generated by a generator connected to an engine, and when the engine speed increases and a predetermined voltage is detected, the starter motor is turned off. 4. The auto choke circuit closes the air intake port of the engine with a choke valve when the thermistor detects that the temperature of the engine is lower than a predetermined temperature at the time of starting the engine, and gradually opens the choke valve after a certain period of time. Engine control method in cogeneration system.