JP5314476B2 - Cogeneration system - Google Patents

Description

  The present invention relates to a co-generation system.

Highly efficient private power generators have been developed. As a kind of such a private power generator, a small-sized generator is driven by a gas engine (hereinafter simply referred to as engine) using city gas or LP gas as fuel, and hot water is supplied using the exhaust heat of the engine. A household cogeneration system has been put to practical use.
In the engine power generator used in this cogeneration system, a generator is mechanically connected to an engine that burns and rotates gas.
In this engine power generation device, at the time of activation, the engine is activated by causing the generator to function as an electric motor. In a state where the engine starts to rotate, an air-fuel mixture is supplied to the engine and ignition control is performed by an ignition device. As a result, the engine completes explosion and starts to rotate spontaneously. After starting to rotate spontaneously, the rotational drive of the engine by the generator (functioning as an electric motor) is stopped.

Normally, when the engine is completely detonated, the engine speed is increased to a rated speed (for example, 1600 rpm) while controlling the opening of the throttle and adjusting the amount of air-fuel mixture supplied to the engine. When the engine rotates spontaneously at the rated speed, it starts operation of the grid-connected inverter and supplies generated power as household power.
On the other hand, the cooling medium is circulated through the engine and heated, and the cooling medium is further heated by high-temperature exhaust gas discharged from the engine and supplied to a domestic water heater.

  Such a cogeneration system is configured to automatically start the engine when an operation command is sent from the water heater. At the time of starting the engine, for example, Patent Document 1 starts a stable engine by increasing the fuel concentration by providing a fuel valve.

Japanese Patent No. 3724634

When a cogeneration system is used at home, it is desired that the cost is low. Therefore, a lean burn engine that uses an air-fuel mixture having a low fuel concentration is preferable because it has high thermal efficiency and can reduce operating costs. However, since the lean burn engine has a low fuel concentration, the rotation immediately after start-up is difficult to stabilize, so the generated power is also unstable. If such unstable power is supplied to a power usage device in the home, the device is adversely affected.
Therefore, the present invention makes effective use of the power immediately after starting even if the power is unstable and cannot be supplied to the home, such as a lean burn engine. It aims at providing the cogeneration system which can supply stably toward the electric power usage apparatus (it may be hereafter called the outside).

The present invention relates to an engine that outputs rotational force, a generator that outputs electric power by being driven by the rotational force output from the engine, a power supply line that supplies electric power output from the generator to the outside, and a cooling medium The cooling medium circulation path for supplying the engine to the engine, the heater disposed on the cooling medium circulation path downstream from the engine, and water heated by heat exchange with the cooling medium flowing through the cooling medium circulation path A cogeneration system with a tank that stores water. The cogeneration system of the present invention is characterized by comprising control means for instructing to supply power output from the generator to one or both of the feeder line and the heater. The electric power output from the machine is instructed to be supplied to the heater for a predetermined period from the start of the engine, and the electric power line is instructed to be supplied after the predetermined period has elapsed.
From the start of the engine until the rotation stabilizes, in other words, until the power stabilizes, the power is not output to the outside. Can supply. And it is efficient to use the electric power generated until it becomes stable. Here, the cogeneration system includes a hot water supply system that heats water using exhaust heat of the engine, but the electric power generated until it is stabilized can be used to heat water (cooling medium). .

The control means according to the present invention can specify the predetermined period based on determining that the generated power has reached a predetermined value.
In the cogeneration system according to the present invention, the heater is preferably functioned as a surplus power heater. The cogeneration system is equipped with a surplus power heater that heats the water using surplus generated power when the power used in the power usage equipment in the home is less than the rated power of the cogeneration system or during a power failure May have. Therefore, a heater that is supplied with electric power for a predetermined period from the start of the engine is provided with a function as the surplus electric power heater. By giving two functions to one heater means, an increase in cost is suppressed.

  The cogeneration system of the present invention supplies the electric power output from the generator to the heater for a predetermined period from the start of the engine, and supplies the electric power line after the predetermined period. Therefore, even if the rotation at the time of starting is unstable like a lean burn engine, stable electric power can be output to the outside from the beginning. In addition, since the heater is supplied to the heater for a predetermined period from the start of the engine, the cooling medium can be heated using the power generated during that period without waste.

It is a figure which shows the structure outline | summary of the cogeneration apparatus which concerns on this Embodiment. It is a figure which shows the electric power feeding part of the cogeneration apparatus which concerns on this Embodiment. In the cogeneration apparatus which concerns on this Embodiment, it is a flowchart which shows the supply procedure of the electric power at the time of engine starting. In the cogeneration apparatus which concerns on this Embodiment, it is a graph which shows the fluctuation | variation of the electric power for every power supply destination at the time of engine starting.

Hereinafter, the cogeneration apparatus 1 according to the present invention will be described with reference to FIGS.
The cogeneration apparatus 1 includes a power feeding unit 3 that generates power and a hot water supply unit 5 that supplies hot water.
<Power supply unit 3>
The power feeding unit 3 is provided with a generator 7 and a gas engine 9 that drives the generator 7. The rotating shaft of the generator 7 and the rotating shaft of the gas engine 9 are mechanically connected. When the gas engine 9 is driven to rotate and the generator 7 is rotated, the generator 7 generates power. The electric power generated by the generator 7 is adjusted by the inverter device 11 for grid connection so that the voltage and the frequency coincide with those of the commercial system 39 as an external power source, and are supplied to the home via the feeder 13 and the distribution board 45. To the power usage apparatus 47.
On the other hand, when electric power is supplied to the generator 7 from the start inverter (AC / DC converter) 37 connected to the commercial system 39, the generator 7 functions as an electric motor and can generate a rotational force to start the gas engine 9. It has become.

  The generator 7 is an AC generator including a rotor connected to a rotating shaft and a stator around which a three-phase output winding is wound. The rotor includes permanent magnets such as ferrite magnets and rare earth magnets as main components, and the generator 7 generates electric power having a voltage proportional to the rotational speed. The output terminal of the three-phase output winding is connected to the inverter device 11. The inverter device 11 converts the alternating current output from the generator 7 into alternating current having the same quality (with respect to voltage, frequency, noise, etc.) as that of the commercial system 39, and synchronizes with the phase of the commercial system 39.

The gas engine 9 is adjusted so that the power generation output is operated at a rated output (for example, 1 kW) during driving, and is set so that vibration noise is minimized during this rated operation. In the present invention, the type of the gas engine 9 is not limited. By using a lean burn engine, it is possible to perform efficient power generation with low fuel consumption.
The mixer 69 is supplied with air sucked from the outside via the air cleaner 71 and also supplied with gas via the gas line 73, and the air is mixed with the gas in the mixer 69 to form a mixture.
A gas shut-off valve (shut-off valve) 75 and a governor 77 are interposed in the gas line 73. The governor 77 adjusts the pressure of the gas supplied to the mixer 69.
The air-fuel mixture obtained by mixing air and gas in the mixer 69 is sucked into the gas engine 9 through the throttle 79. At this time, the supply amount of the air-fuel mixture to the gas engine 9 can be adjusted by adjusting the opening of the throttle 79.

  The gas engine 9 is supplied with an air-fuel mixture and ignites by generating a spark from an ignition plug of the ignition device 65 and is driven to rotate. Note that the ignition timing control of the ignition device 65 is performed by the first control unit 51. Exhaust gas discharged from the gas engine 9 is discharged to the outside through the exhaust gas heat exchanger 17 and a muffler (not shown).

  The power feeding unit 3 is provided with a cooling medium circulation path 15 that passes through the gas engine 9 so that the cooling medium circulates in order to use the exhaust heat of the gas engine 9. Heat is also given to the cooling medium in the cooling medium circulation path 15 from the exhaust gas heat exchanger 17 and the surplus power heater 19.

The surplus power heater 19 is not supplied with power during rated operation, but the load on the commercial system 39 is suddenly cut off (typically during a power failure) when the generator 7 is generating power, or at home The generated power is supplied to the surplus power heater 19 when the power used by the power usage device 47 is less than the power generated by the generator 7. In this way, the cooling medium in the cooling medium circulation path 15 is heated using the electric power supplied to the surplus power heater 19 and supplied.
In the present embodiment, the surplus power heater 19 performs other functions. That is, the cogeneration system 1 supplies the power generated within a predetermined period from the start of the gas engine 9 to the surplus power heater 19 to heat the coolant in the coolant circulation path 15.

<Hot water supply section 5>
In the hot water supply section 5, the heated cooling medium in the cooling medium circulation path 15 is converted into water stored in the hot water storage tank 25 by the heat exchangers 21 and 23, and heating equipment (for example, a household device not shown) Warm the water supplied to the floor heating equipment. Further, the hot water supply section 5 is provided with heat exchangers 27 and 29 for heating water to be supplied into the home, and an auxiliary heat source device 31 when the heat source is insufficient.

Next, the control system of the power feeding unit 3 will be described with reference to FIG.
An AC / DC converter 37 and a DC / AC inverter 41 are provided on the inverter board 35 provided in the power feeding unit 3. In the commercial system 39, the voltage and frequency hardly change. However, the voltage and frequency of the electric power generated by the generator 7 are likely to fluctuate depending on the rotational fluctuation of the gas engine 9 or the usage state of the electric power. Therefore, the voltage and frequency of the electric power generated by the generator 7 are matched with those of the commercial system 39 by the AC / DC converter 37 and the DC / AC inverter 41. Among them, the AC / DC converter 37 converts, for example, 270 V and 213 Hz alternating current generated by the generator 7 into about 380 V direct current. The DC / AC inverter 41 converts the converted direct current of about 380V into alternating current of 100V / 200V and 50Hz / 60Hz which is the same as the voltage and frequency in the commercial system 39. The AC / DC converter 37 functions as the above-described startup inverter when the gas engine 9 is started.

  The inverter board 35 is provided with a second control unit 53 that controls the AC / DC converter 37 and the DC / AC inverter 41. The second control unit 53 sends an instruction to the semiconductor switch 59 that controls the amount of power supplied to the surplus power heater 19 provided outside the inverter board 35. This instruction is based on PWM (Pulse Width Modulation) control.

The inverter board 35 is provided with a control power supply 55 that supplies electric power to the ECU board 49.
The inverter board 35 is provided with a relay 61. In the cogeneration apparatus 1, if power is supplied to the commercial system 39 at the time of a power failure, it will interfere with the maintenance work of the electrical system corresponding to the power failure. Therefore, at the time of a power failure, the power supply to the commercial system 39 can be cut off by opening the relay 61 (OFF, state of FIG. 2).

  The power feeding unit 3 is provided with an ECU (Engine Control Unit) board 49 that controls the gas engine 9, the throttle 79, the gas shielding valve 75, the ignition device 65, and the like. A first control unit 51 is provided on the ECU board 49. The first control unit 51 is notified of the engine speed detected by the speed sensor 81.

  Further, the power feeding unit 3 is provided with a current sensor 43 between the commercial system 39 and the switchboard 45. The current sensor 43 detects the power used by the commercial system 39. Since the rated power output is about 1 kW, when the power used by the power usage device 47 in the home exceeds 1 kW, power is supplied from the commercial system 39 to the power usage device 47 via the switchboard 45.

  However, if the power usage of the power usage device 47 is less than 1 kW, surplus power flows backward to the commercial grid 39. In order to prevent this, the detection result detected by the current sensor 43 is always sent to the second control unit 53 provided on the inverter board 35. When the second control unit 53 detects that the current flowing from the commercial system 39 to the switchboard 45 has decreased based on the sent detection result, the second control unit 53 determines that a reverse power flow may occur. Then, the second control unit 53 sends a PWM control signal to the semiconductor switch 59 that controls the power used by the surplus power heater 19 so that the power corresponding to the surplus power is consumed.

The second control unit 53 switches the supply destination of the electric power generated by the generator 7 when the gas engine 9 is started. The procedure for switching the power supply destination will be described with reference to FIG.
By turning on a main switch (not shown) provided on the control panel 83, the cogeneration apparatus 1 is requested to start (S101 in FIG. 3). The main switch can be turned on by the user's operation when hot water supply is required, but can also be turned on automatically by learning the user's operation.

  When the start request is made, next, a sequence of whether or not to start power generation is executed (S103 in FIG. 3). In this sequence, when an abnormality has occurred and the cogeneration apparatus 1 is stopped, processing is performed such as displaying the fact on the control panel 83 and notifying the user. In this case, the cogeneration apparatus 1 cannot be started.

  If it is confirmed in S103 that the cogeneration apparatus 1 can be started normally, a power generation start command is issued. The second control unit 53 causes the AC / DC converter 37 to function as a start inverter for the generator 7 and outputs an instruction signal for operating the generator 7 as a motor to the AC / DC converter 37. At this time, the relay 61 is closed (ON). Following the rotation of the generator 7, the gas engine 9 is rotated. When the gas engine 9 reaches the start preparation completion rotation speed (for example, 200 rpm), the first control unit 51 starts engine start control. That is, the gas engine 9 is started by operating the throttle 79 and the ignition device 65. Thus, power generation is started by the power generator 7 (S105 in FIG. 3). Here, the AC / DC converter 37 is released from its function as a startup inverter. Also, the relay 61 is opened (OFF, FIG. 3 S107). By doing so, the power generated by the generator 7 is stopped from being supplied to the power usage apparatus 47 outside, that is, in the home.

  Next, the second control unit 53 sends a PWM control signal to the semiconductor switch 59 so that the power generated by the generator 7 is consumed by the surplus power heater 19. The surplus power heater 19 is heated by the supplied electric power and warms the cooling medium in the cooling medium circulation path 15.

  The second control unit 53 determines whether or not the generator 7 is stably generating the rated power (S111 in FIG. 3). There are at least two methods for this determination. One is a method in which rated power is considered to be stably generated according to elapsed time. The generator 7 is experimentally driven by the gas engine 9 to generate power, and the time until the rated power is stably obtained is measured. Based on the measurement result, the predetermined time T is set in the second controller 53. To do. And the 2nd control part 53 considers that the generator 7 is generating the rated power stably after the predetermined time T has passed since the start of power generation. The other is a method of obtaining the actual generated power of the generator 7. This can be obtained by detecting the voltage [V] and current [A] of AC power between the generator 7 and the AC / DC converter 37. Any method may be used in this embodiment, but a sensor for measuring voltage [V] and current [A] is unnecessary, and when priority is given to cost reduction, a predetermined time is set in advance. From T, it is determined that the rated power is stably obtained. On the other hand, when priority is given to determining whether the rated power is being stably generated with high accuracy, the generated power is actually obtained.

  If the second control unit 53 determines that the generator 7 is stably generating the rated power, the second control unit 53 closes the relay 61 (FIG. 3, S113, ON). As a result, the electric power generated by the generator 7 can be supplied to the household electric power usage apparatus 47 via the feeder 13 connected to the end of the relay 61.

  After the relay 61 is closed, the second control unit 53 sends a PWM control signal to the semiconductor switch 59 so as to reduce power consumption in the surplus power heater 19. Thereby, the supply destination of the electric power generated by the generator 7 is switched from the surplus power heater 19 to the power usage device 47 (S115 in FIG. 3). Thereafter, the rated power of 1 kW is stably supplied to the power usage device 47.

  FIG. 4 shows power fluctuations in the process of switching the power supply destination from the surplus power heater 19 to the power usage device 47. As shown in FIG. 4, the power supplied to the surplus power heater 19 approaches 1 kW which is the rated power while increasing or decreasing unstable. When this power reaches 1 kW, the power supplied to the surplus power heater 19 is reduced and finally becomes 0 (zero). At the same time as the power supplied to the surplus power heater 19 starts to be reduced, the supply of power to the power usage device 47 is started via the inverter device 11, the relay 61 and the switchboard 45. As shown in FIG. 4, this power reaches 1 kW, which is the rated power while showing a smooth monotonous increase, and is thereafter stably supplied to the power usage device 47.

As described above, the present embodiment circulates in the hot water supply unit 5 by consuming it with the surplus power heater 19 until the rotation of the gas engine 9 is stabilized and the power obtained by the generator 7 reaches the rated power. The cooling medium to be heated is heated. When the generator 7 can stably obtain the rated power, the power is supplied to the power usage device 47 in the home. Therefore, since rated power can be supplied to the power usage apparatus 47 from the beginning, the power usage apparatus 47 does not have a problem. Further, since the surplus power heater 19 consumes the power until the power reaches the rated power and is supplied to the power usage device 47, the power up to that time can be used effectively.
In the present embodiment, the rotational speed of the gas engine 9 is controlled only by the throttle 79. When a lean burn engine is used as the gas engine 9, it is not necessary to provide an oxygen concentration meter and a three-way catalyst. Therefore, power generation can be performed simultaneously with the start of the gas engine 9. Therefore, even if power is consumed by the surplus power heater 19 until the power reaches the rated power, supply of power to the power usage device 47 can be started relatively early.

In the present embodiment, it is recommended to use a lean burn engine as the gas engine 9, but the present invention is not limited to this.
Further, the surplus power heater 19 is used as a target to consume the power generated until the rated power is reached. However, a heater is provided separately from the surplus power heater 19, and the power generated until the rated power is reached there. It can also be consumed.
The surplus power heater 19 is often arranged on the cooling medium circulation path downstream from the engine, but can be realized even if arranged on the upstream side.
Other than this, as long as the gist of the present invention is not deviated, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

  DESCRIPTION OF SYMBOLS 1 ... Cogeneration apparatus, 7 ... Generator, 9 ... Gas engine, 51 ... 1st control part, 53 ... 2nd control part, 19 ... Surplus electric power heater

Claims (3)

An engine that outputs rotational force;
A generator that outputs electric power by being driven by the rotational force output by the engine;
A power supply line for supplying power output from the generator to the outside;
A coolant circulation path through which the coolant circulates through the engine;
A heater disposed on the cooling medium circulation path downstream of the engine to heat the cooling medium;
A tank for storing water heated by heat exchange with the cooling medium flowing through the cooling medium circulation path;
Control means for instructing to supply the power output from the generator to one or both of the feeder and the heater;
With
The control means includes
The power output from the generator is
Instructed to supply the heater for a predetermined period from the start of the engine,
A cogeneration system that instructs to supply the power supply line after the predetermined period has elapsed. The control means includes
The cogeneration system according to claim 1, wherein the predetermined period is determined based on determining that the electric power generated by the generator has reached a predetermined value.   The cogeneration system according to claim 1 or 2, wherein the heater functions as a surplus power heater.

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