JP6541100B2 - Power system using external combustion engine - Google Patents

Description

  The present invention relates to an electric power system that improves power generation efficiency, use efficiency of electric power, and the like using an external combustion engine including a Stirling engine.

  In recent years, a Stirling engine, which is a type of external combustion engine, has attracted attention in order to effectively use waste heat, solar heat, and the like of a woody biomass boiler and the like.

  The Stirling engine is a type of external combustion engine that externally heats and cools a gas such as helium in the working space, and obtains an output by changing its volume and pressure.

  This Stirling engine can expect high thermal efficiency and heat the working fluid (gas) from the outside, so it can utilize various heat sources such as wood biomass combustion heat, solar heat, geothermal heat, waste heat regardless of the heat source, and it can be used for renewable energy There is an advantage that it can contribute to utilization and energy saving.

  Various techniques related to the Stirling engine have been proposed (for example, Patent Document 1 etc.).

JP, 2006-118430, A

  However, when solar heat or the like is used as the heat source, the heat energy of the heat source is likely to fluctuate due to conditions such as weather or time zone, and there is a problem that the output of the Stirling engine is unstable. That is, solar heat and the like easily cause variation in thermal energy collected due to changes in conditions such as the weather, and when the generator is driven by a Stirling engine operated by such a heat source, the generated power is stable There was a disadvantage of not doing.

  In addition, when the Stirling engine is operated by the heat source as described above and the generator is driven to obtain the power, the output power is also fluctuated according to the fluctuation of the heat energy of the heat source. There may be a shortage or excess of power on the side (load).

  Therefore, there is a disadvantage that the operation of the electric product or the like may become unstable or the surplus power may be wasted.

  As described above, the power system using the conventional external combustion engine has a drawback that the generated power is not stable and the power generation efficiency and the utilization efficiency of the power are relatively low.

  An object of the present invention is to provide an electric power system using an external combustion engine which can stabilize generated power and improve power generation efficiency and utilization efficiency of electric power in view of the above-mentioned circumstances.

  In order to solve the above problems, an electric power system using an external combustion engine according to the invention of claim 1 comprises a heat source means for generating heat and a Stirling engine operated by thermal energy of a predetermined temperature supplied from the heat source means An external combustion engine including: power generation means driven by the external combustion engine as a motive power source; AC / DC conversion means for converting AC power generated by the power generation means into DC power; and the AC / DC conversion means Provided between the DC bus and the load through which the direct current converted by the DC current passes and which has a DC / AC conversion unit, a first voltage detection unit for detecting the voltage of the DC bus, and the first voltage The generator control inverter increases / decreases the frequency of the power generation means according to the detection result of the detection unit, and the generator control inverter is configured such that the detection voltage by the first voltage detection unit is the upper limit set voltage When it exceeds, the frequency is reduced to reduce the output of the external combustion engine, and when the detection voltage by the first voltage detection unit is less than the lower limit setting voltage, the frequency is increased to reduce the external combustion engine. Load tracking control is performed to increase the output.

  The electric power system using the external combustion engine according to the invention of claim 2 stores the surplus electric power in the DC bus according to the invention of claim 1 through the DC / DC converter and the charge / discharge control device. The secondary battery is further provided with a charge degree detection unit for detecting the charge degree in the secondary battery, and charging is performed to control allocation of power to the secondary battery according to the detection result of the charge degree detection unit. A discharge control device is connected to the DC bus, and the charge / discharge control device performs charge / discharge control so as to increase the power supply to the secondary battery when the detection result of the charge degree detection unit is less than or equal to a predetermined threshold. It is characterized by doing.

The power system using the external combustion engine according to the invention of claim 3 relates to the invention according to claim 2, wherein the secondary battery includes at least a lithium ion battery, an electric double layer capacitor, a lithium ion capacitor and a lead storage battery. It is characterized by including one.

The power system using the external combustion engine according to the invention of claim 4 according to the invention of claim 2 or claim 3 further comprises a second voltage detection unit for detecting the voltage of the DC bus, and The discharge control device charges the secondary battery if the detection voltage of the second voltage detection unit is higher than the set voltage and the detection result of the charge degree detection unit is less than or equal to a predetermined threshold value. If the detection voltage of the voltage detection unit is higher than the set voltage and the detection result of the charge degree detection unit exceeds a predetermined threshold, the frequency is reduced by the generator control inverter and the external combustion is performed. The output of the engine is lowered, and the secondary battery is discharged if the detection voltage of the second voltage detection unit is lower than the set voltage and the detection result of the charge degree detection unit exceeds a predetermined threshold. The detection voltage of the second voltage detection unit If the voltage is lower than a constant voltage and the detection result of the charge degree detection unit is equal to or less than a predetermined threshold value, the generator control inverter is controlled to increase the frequency to increase the output of the external combustion engine It is characterized by

The power system using the external combustion engine according to the invention of claim 5 is characterized in that, in the invention according to any one of claims 1 to 4 , the predetermined temperature is 600 ° C. or less. .

  The power system using the external combustion engine according to the invention of claim 6 relates to the invention according to any one of claims 1 to 5, wherein the heat source means comprises a solar heat collector and a combustor of biomass fuel. It is characterized by including.

  According to the present invention, it is possible to provide a power system using an external combustion engine that can improve the power generation efficiency and the utilization efficiency of power.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows schematic structure of the electric power system using the external combustion engine which concerns on 1st Embodiment. It is a block diagram which shows schematic structure of the electric power system using the internal combustion engine as a comparative example. It is a block diagram which shows schematic structure of the electric power system using the external combustion engine which concerns on 2nd Embodiment. BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram which shows the Example of the low temperature difference type Stirling engine applied to the electric power system using the external combustion engine which concerns on embodiment.

  Hereinafter, an embodiment as an example of the present invention will be described in detail based on the drawings. Here, in the attached drawings, the same members are denoted by the same reference numerals, and redundant descriptions are omitted. The present invention is not limited to the above-described embodiment, as the description herein is the best mode for carrying out the present invention.

First Embodiment
The configuration of a power system S1 using the external combustion engine according to the first embodiment will be described with reference to the block diagram of FIG.

  As shown in FIG. 1, a power system S1 using an external combustion engine according to the present embodiment includes a heat source means 1 constituted by a solar heat collector generating heat, a combustor of biomass fuel, etc., and a heat source means 1. A Stirling engine 2 as a type of external combustion engine operated by thermal energy of a predetermined temperature supplied from 1, a power generation unit (generator) 3 driven by the Stirling engine 2 as a power source, and power generation by the power generation unit 3 AC / DC conversion means (AC / DC converter) 4 for converting the AC power into DC power, and a DC bus 200 through which direct current converted by the AC / DC conversion means 4 passes and a load 100, According to the detection results of the free standing inverter 5 having the DC / AC conversion unit 5a, the first voltage detection unit V1 for detecting the voltage of the DC bus 200, and the first voltage detection unit V1. The generator control inverter 6 increases or decreases the wave number, and the generator control inverter 6 reduces the frequency when the voltage detected by the first voltage detection unit V1 exceeds the upper limit set voltage, and the output of the Stirling engine 2 The load follow-up control is performed to lower the frequency and raise the output of the Stirling engine 2 when the detection voltage of the first voltage detection unit V1 is lower than the lower limit set voltage.

  Although omitted in the present embodiment, an interconnection inverter may be separately provided for interconnection with an external power supply.

  According to the power system S1 using the external combustion engine according to the first embodiment, the Stirling engine can be controlled by simple control to increase or decrease the frequency of the power generation unit 3 according to the detection result of the first voltage detection unit V1. By adjusting the output of 2, load following control can be realized.

 In the actual device, when converting the AC power of the generator 3 to direct current by the generator control inverter 6, the rotational frequency of the generator 3 can be changed by changing the conversion frequency.

  Further, the AC / DC conversion means (AC / DC converter) 4 may be configured such that the inverter element itself constituting the generator control inverter 6 doubles as well.

(Power system according to comparative example)
Here, with reference to FIG. 2, a power system S100 according to a comparative example will be described.

  As shown in FIG. 2, an electric power system S100 according to the comparative example includes an internal combustion engine 20 such as a gasoline engine provided with an output control device 40, and power generation means (generator) 3 driven with the internal combustion engine 20 as a power source. The controller 300 includes a controller 300 that controls the generator 3, a voltage detection unit V10 that detects a voltage output from the controller 300, and an RPM detector 302 that is located between the output control device 40 and the generator 3 and detects the number of revolutions.

  Note that, instead of the RPM detector 302, a speed arithmetic device capable of detecting the rotational speed (for example, a speed arithmetic device in vector control) may be used.

  The controller 300 further includes a generator control inverter 30 for controlling the output of the generator 3 and an AC / DC converter (AC / DC converter) 4 for converting AC power generated by the power generation means 3 into DC power. Prepare.

  Further, the output control device 40 includes, for example, various control units such as a fuel control unit 40a and an intake control unit 40b.

  Then, the controller 300 and the output control device 40 set the optimum values of the fuel supply amount and the air amount with respect to the rotational speed of the internal combustion engine 20 corresponding to the load in advance, for example, in accordance with the rotational speed controlled by the controller 300 It is necessary to control the output of the internal combustion engine 20 by a relatively complicated control process of adjusting the fuel supply amount and the air amount. As a result, the device configuration of the control system becomes complicated and the cost increases.

  In addition, when only the rotational speed of the internal combustion engine 20 is controlled according to the load, the amount of fuel supplied or the amount of air deviates from the optimum value, causing incomplete combustion and increasing harmful components of exhaust gas. There was also a drawback that it occurred.

  On the other hand, according to the power system S1 using the external combustion engine according to the first embodiment, as described above, the frequency of the power generation unit 3 is increased or decreased according to the detection result of the first voltage detection unit V1. The output of the Stirling engine 2 can be controlled by relatively simple control. Further, unlike the internal combustion engine 20, the Stirling engine 2 does not have to adjust the amount of supplied fuel or the amount of air directly to control the output because of the characteristics thereof, and the output control device 40 itself in the comparative example is unnecessary. is there. Also, as a matter of course, complicated control processing for controlling the output control device 40 is not necessary. Therefore, the configuration of the entire system can be simplified, and the cost can be reduced.

Second Embodiment
The configuration of a power system S2 using an external combustion engine according to the second embodiment will be described with reference to the block diagram of FIG.

  As shown in FIG. 3, the power system S2 using the external combustion engine according to the present embodiment is the same as the power system S1 according to the first embodiment, and the solar heat collector and the biomass fuel that generate heat And a Stirling engine 2 operated by heat energy of a predetermined temperature supplied from the heat source means 1, and a power generation means (generator) driven by the Stirling engine 2 as a power source 3 and an AC / DC converter (AC / DC converter) 4 as AC / DC conversion means for converting AC power generated by the generator 3 into DC power, provided between the DC bus 200 and the load 100 , A self-sustaining inverter 5 having a DC / AC conversion unit 5a, a first voltage detection unit V1 detecting a voltage output from the self-sustaining inverter 5, and a detection result of the first voltage detection unit V1 And a generator control inverter 6 to increase or decrease the frequency of the generator 3 in response.

  In addition, secondary battery 12 storing surplus power through AC / DC converter 4 via DC / DC converter 10 and charge / discharge control device 11 detects the degree of charge in secondary battery 12 A charge / discharge control device 11 further provided with a detection unit (charge degree sensor) 13 and controlling the allocation of power to the secondary battery 12 according to the detection result of the charge degree sensor 13 is connected to the DC bus 200, The discharge control device 11 performs load following control so as to increase the power supply to the secondary battery 12 when the detection result of the charge degree sensor 13 is less than or equal to a predetermined threshold.

  The secondary battery 12 can include at least one of batteries such as a lithium ion battery, an electric double layer capacitor, a lithium ion capacitor, and a lead storage battery.

  Further, power system S2 according to the present embodiment further includes a second voltage detection unit V2 that detects a voltage between DC / DC converter 10 and charge / discharge control device 11. The charge / discharge control device 11 charges the secondary battery 12 if the detection voltage of the second voltage detection unit V2 is higher than the set voltage and the detection result of the charge degree detection unit 13 is less than or equal to a predetermined threshold. If the detection voltage of the second voltage detection unit V2 is higher than the set voltage and the detection result of the charge degree detection unit 13 exceeds a predetermined threshold, the frequency is reduced by the generator control inverter 6 If the output of the Stirling engine 2 is lowered, the detection voltage of the second voltage detection unit V2 is lower than the set voltage, and the detection result of the charge degree detection unit 13 exceeds a predetermined threshold, the secondary battery 12 is selected. If the voltage detected by the second voltage detection unit V2 is lower than the set voltage and the detection result of the charge degree detection unit 13 is equal to or less than the predetermined threshold, the generator control inverter 6 raises the frequency to perform Stirling. engine To increase the output of the controls, respectively.

  As a result, it is possible to improve the power generation efficiency and the power utilization efficiency according to the load 100 in the entire system.

  The advantage that the output of the Stirling engine 2 can be controlled by a relatively simple control of increasing or decreasing the frequency of the power generation means 3 according to the detection result of the first voltage detection unit V1 is the first embodiment. Is the same as the power system S1 according to

  In addition, in electric power system S2 which concerns on this Embodiment, although voltage detection part V1 and V2 are provided as another apparatus, you may make it serve as voltage detection part V1 and V2 by one voltage detection apparatus.

  Although omitted in the present embodiment, an interconnection inverter may be separately provided for interconnection with an external power supply.

(Example of low temperature difference type Stirling engine)
An embodiment of a heat engine using a low temperature difference type Stirling engine 2 applicable to the power systems S1 and S2 using the external combustion engine according to the embodiment will be described with reference to FIG.

  FIG. 5 is an overall configuration diagram of the low temperature difference type Stirling engine 2 according to the first embodiment.

  The engine main body 201 constituting the Stirling engine includes a cooling device 203, a heat source device 205 as a heat source means, and a heat medium cooling device 206 as a cooling means for cooling a heat transfer fluid flowing through the heat source device 205. The cooling device 203, the heat source device 205, and the heat medium cooling device 206 will be described later.

  The Stirling engine body 201 is provided with a cover 209 at the top in the drawing of the housing 207 and a crankcase 211 at the bottom. A heat exchanger unit 213 is disposed substantially at the center in the vertical direction in the housing 207, and this heat exchanger unit 213 converts the heater 15, the regenerator 17 and the cooler 19 into the working gas flow from the top in FIG. They are arranged side by side.

  The heat source device 205 and the heat medium cooling device 206 described above are connected to the heater 15 described above, and the cooling device 203 and the heat medium cooling device 206 are connected to the cooler 19 respectively.

  The high temperature side piston 21 is accommodated in the housing 207 on the upper side of the heater 15, and the low temperature side piston 23 is accommodated movably in the vertical direction in FIG. 5 in the housing 207 on the lower side of the cooler 19. ing.

  The high temperature side piston 21 is connected to the crank pin 27 a of the crankshaft 27 via the piston rod 25 penetrating through the heat exchanger unit 213 and the low temperature side piston 23 so as to be movable relative to the heat exchanger unit 213. It is connected to the crank pin 27 b of the crank shaft 27 via a piston rod 29 of a book.

  The high temperature side piston 21 and the low temperature side piston 23 are connected to the crankshaft 27 such that the phase difference between the high temperature side piston 21 and the low temperature side piston 23 when reciprocating is a predetermined phase difference of, for example, 90 degrees.

  A region surrounded by the housing 207 and the high temperature side and low temperature side pistons 21 and 23 is a working gas space in which a working gas such as helium is sealed in a sealed state, and of these, the heater 15 and the high temperature side piston 21 Is the high temperature working space 31 where the working gas heated in the heater 15 expands, and the working gas released in the cooler 19 is compressed between the cooler 19 and the low temperature side piston 23 Low temperature operating space 33. Between the high temperature working space 31 and the low temperature working space 33, heat and power are converted by moving the working gas to each other to repeat expansion and compression of the working gas.

  The high-temperature side piston 21 and the low-temperature side piston 23 described above constitute a power piston that causes the volume change of the working gas to the high temperature working space 31 and the low temperature working space 33 respectively, and transmits the power upon receiving the pressure change of the working gas. doing.

  Further, a generator 41 is connected to the crankshaft 27 via a pulley 35, a belt 37 and a pulley 39 outside the housing 207, and the generator 41 is driven by driving the Stirling engine main body 201 described above, which is a Stirling engine. Generate electricity. That is, in the present heat engine, the crankshaft 27 takes out the reciprocating motion of each of the pistons 21 and 23 based on the pressure change of the working gas as the rotational motion to the outside.

  The heater 15 has a heater portion 43a of a portion of the heat medium fluid piping 43 serving as a heat medium fluid passage inserted in the vicinity of the regenerator 17 side of the high temperature working space 31 described above. The heat medium fluid piping 43 is formed in a closed loop, and the heat source portion 43b as an extended portion drawn out from the heater 15 (the Stirling engine main body 201) constitutes the heat source device 205 described above.

  The heat source device 205 here constitutes an exhaust gas heat source means using exhaust gas E from a boiler as a combustion device, that is, waste heat. The boiler uses biomass fuel such as wood pellets, and may use gas fuel or liquid fuel. The heat source device 205 may be an exhaust gas heat source means using exhaust gas of a combustion engine such as an internal combustion engine which is a combustion device other than a boiler.

  Further, as the heat medium fluid here, it is preferable to use a liquid or vapor such as oil or a borate.

  A pump 45 and a reservoir tank 47 are respectively installed at one intermediate portion 43 c between the heater portion 43 a and the heat source portion 43 b in the heat medium fluid piping 43.

  Further, one end of a pipe 103 is connected to the other intermediate portion 43d of the heat medium fluid pipe 43 between the heater portion 43a and the heat source portion 43b via a flow rate adjusting valve 101 as a flow rate adjusting means. The other end of the heat medium fluid pipe 43 is connected to one end of the heat medium cooling portion 105 which is an extension portion of the heat medium fluid piping 43 to the outside of the heater 15 (the Stirling engine main body 201). The heat medium cooling portion 105 is disposed in the water 107 which is a cooling medium in the heat medium cooling device 206 described above.

  The other end of the heat medium cooling portion 105 described above is connected to one end of the pipe 109, and the other end of the pipe 109 is connected to the heat medium fluid pipe 43 between the heater 15 and the reservoir tank 47.

  That is, the heater 15 and the heat medium cooling device 206 as the cooling means are connected in parallel by the heat medium fluid passage.

  On the other hand, the cooler 19 inserts a cooler portion 49 a of a part of the cooling water pipe 49 serving as a cooling medium passage in the vicinity of the regenerator 17 side of the low temperature working space 33 described above. A pipe 49 b drawn to the outside on the downstream side from the cooler 19 of the cooling water pipe 49 is connected and opened in the above-described heat medium cooling device 206.

  Further, one end of a pipe 49c is separately connected to the heat medium cooling device 206, and the other end of the pipe 49c is one end of a cooling medium cooling portion 49d disposed in the cooling water tank 51 of the cooling device 203 described above. Connected to The other end of the cooling medium cooling portion 49d connects one end of the pipe 49e, and the other end of the pipe 49e connects to the cooler portion 49a described above.

  The cooling water in the cooling water tank 51 is supplied from the outside through the inlet pipe 111 and is discharged from the outlet pipe 113 and can be used, for example, for a boiler (not shown).

  The pump 52 is installed in the above-mentioned piping 49e, and the reservoir tank 119 is connected to the piping 49e between the pump 52 and the cooling medium cooling portion 49d.

  In the Stirling engine configured in this manner, heat and power are repeatedly transferred by moving the working gas between the high temperature working space 31 and the low temperature working space 33 in the stirling engine main body 201 to repeat expansion and compression of the working gas. Conversion is performed. At this time, the flow control valve 101 is set so that the heat medium fluid flows to the heater 15.

  At this time, in the present embodiment, the heat transfer fluid heated by the heat source portion 43b of the heat source device 205 flows through the heat transfer fluid pipe 43 by the operation of the pump 45 and passes through the flow rate adjustment valve 101 and the heater portion 43a of the heater 15. The working gas exchanges heat with the heat transfer fluid to receive heat. Thereafter, the heat transfer fluid that has dissipated heat and is lowered in temperature flows through one of the middle portions 43 c of the heat transfer fluid pipe 43 and returns to the pump 45.

  On the other hand, in the cooler 19, the cooling water 107 in the heat medium cooling device 206 is sent to the cooler portion 49a of the cooling water pipe 49 by the operation of the pump 52, whereby the working gas exchanges heat with the cooling water for cooling Be done. Thereafter, the cooling water whose temperature has been increased by receiving heat flows through the pipe 49 b of the cooling water pipe 49 and returns to the heat medium cooling device 206.

  At the time of such operation of the Stirling engine, for example, when the operation of the Stirling engine main body 201 is stopped due to failure or nonuse, the flow control valve 101 is switched so that the heat medium fluid flows toward the pipe 103. As a result, the heat transfer fluid flowing out of the heat source portion 43 b flows into the heat transfer device 206 and is cooled by the cooling water 107. The cooled heat medium fluid returns to the heat medium fluid piping 43 through the piping 109, is heated again by the heat source device 205, and flows into the heat medium cooling device 206.

  When the operation of the Stirling engine main body 201 is restarted, the flow control valve 101 is switched so that the heat medium fluid flows to the heater 15.

  As described above, in the present embodiment, when the Stirling engine main body 201 stops operation due to failure or nonuse, for example, during operation of the Stirling engine, the heat transfer fluid constantly heated by the heat source device 205 is heated. Since the heat medium cooling device 206 is cooled without flowing into the vessel 15, an excessive temperature rise of the heat medium fluid can be suppressed, and the deterioration of the heat medium fluid can be prevented.

  Further, even during operation of the Stirling engine, the control means (not shown) controls the opening degree of the flow rate adjustment valve 101 according to the operation state of the Stirling engine main body 201 constituting the Stirling cycle, thereby the heat medium of the heat medium fluid By adjusting the amount flowing to the cooling device 206 and the amount flowing to the heater 15, the temperature of the heat transfer fluid can be appropriately adjusted according to the operating state of the Stirling engine main body 201.

  Moreover, in the above-mentioned Example, since the waste heat of a boiler is utilized as a heat source in the heat-source apparatus 205, the effective use of energy can be achieved. Furthermore, using biomass as fuel for the boiler can contribute to the reduction of carbon dioxide that is believed to affect global warming.

  Although the invention made by the inventor has been specifically described based on the embodiment, the embodiment disclosed in the present specification is illustrative in all points and limited to the disclosed technology. It should not be considered. That is, the technical scope of the present invention is not to be interpreted restrictively based on the description in the above embodiment, and should be interpreted in accordance with the description of the claims only. It includes all modifications within the scope of the claims and the technical equivalents to the described art.

S1, S2: Power system 1 ... Heat source means 2 ... Stirling engine (external combustion engine)
3 ... Generator (generation means)
DESCRIPTION OF SYMBOLS 4 ... AC / DC converter 5 ... Self-supporting inverter 5a ... DC / AC conversion part 6 ... Generator control inverter 10 ... DC / DC converter 11 ... Charge / discharge control apparatus 12 ... Secondary battery 13 ... Charge degree sensor (The charge degree Detection unit)
DESCRIPTION OF SYMBOLS 30 ... Generator control inverter 15 ... Heater 17 ... Regenerator 19 ... Cooler 21 ... High temperature side piston 23 ... Low temperature side piston 25 ... Piston rod 27 ... Crankshaft 27a, 27b ... Crank pin 29 ... Piston rod 31 ... High temperature operation Space 33 Low temperature working space 35 Pulley 37 Belt 39 Pulley 41 Generator 43 Heat transfer medium fluid piping 43a Heater portion 43b Heat source portion 43c, 43d Intermediate portion 43e Bypass passage 45 Pump 47 Reservoir Tank 49 ... cooling water piping 49a ... cooler portion 49b, 49c, 49d, 49e ... piping 49d ... cooling medium cooling portion 50 ... controller 51 ... cooling water tank 52 ... pump 53 ... hot water heater 55 ... connection piping 57 ... switching Valve 59: Pump 100: Load 101: Flow control valve 103: Piping 10 5 Heat medium cooling portion 107 Cooling water 109 Piping 111 Inlet piping 113 Outlet piping 119 Reservoir tank 200 DC bus bar 201 Stirling engine main body 203 Cooling device 205 Heat source device 206 Heat medium cooling device 207 Housing 209 ... Cover 211 ... Crankcase 300 ... Controller 301 ... DC / AC converter 302 ... RPM detector E ... Exhaust gas V1 ... First voltage detector V2 ... Second voltage detector

Claims (6)

Heat source means for generating heat;
An external combustion engine including a Stirling engine operated by heat energy of a predetermined temperature supplied from the heat source means;
Power generation means driven by the external combustion engine as a power source;
AC / DC conversion means for converting AC power generated by the power generation means into DC power;
A self-sustaining inverter provided between a DC bus and a load through which direct current converted by the AC / DC conversion means passes and having a DC / AC conversion unit,
A first voltage detection unit that detects a voltage of the DC bus;
A generator control inverter that increases or decreases the frequency of the power generation unit according to the detection result of the first voltage detection unit;
The generator control inverter reduces the frequency to lower the output of the external combustion engine when the voltage detected by the first voltage detection unit exceeds the upper limit setting voltage, thereby reducing the frequency by the first voltage detection unit. An electric power system using an external combustion engine, wherein load follow-up control is performed so as to raise the output of the external combustion engine by raising the frequency when the detected voltage is less than the lower limit setting voltage. In the DC bus, a secondary battery for storing surplus power via a DC / DC converter and a charge / discharge control device,
The secondary battery is further provided with a charge degree detection unit for detecting the charge degree,
A charge and discharge control device that controls allocation of power to the secondary battery according to the detection result of the charge degree detection unit is connected to the DC bus,
The charge and discharge control device performs charge and discharge control so as to increase the power supply to the secondary battery when the detection result of the charge degree detection unit is less than or equal to a predetermined threshold value. Power system using the external combustion engine described. The power system using the external combustion engine according to claim 2, wherein the secondary battery includes at least one of a lithium ion battery, an electric double layer capacitor, a lithium ion capacitor, and a lead storage battery. And a second voltage detection unit that detects a voltage of the DC bus.
The charge / discharge control device is
If the detection voltage of the second voltage detection unit is higher than the set voltage and the detection result of the charge degree detection unit is less than or equal to a predetermined threshold, the secondary battery is charged;
If the detection voltage of the second voltage detection unit is higher than the set voltage and the detection result of the charge degree detection unit exceeds a predetermined threshold, the frequency is reduced by the generator control inverter. Reduce the output of the external combustion engine,
If the detection voltage of the second voltage detection unit is lower than the set voltage and the detection result of the charge degree detection unit exceeds a predetermined threshold, the secondary battery is discharged;
If the detection voltage of the second voltage detection unit is lower than the set voltage and the detection result of the charge degree detection unit is less than or equal to a predetermined threshold, the generator control inverter raises the frequency to perform the external combustion. As you raise the output of the engine,
The electric power system using the external combustion engine according to claim 2 or 3 characterized by controlling each. The said predetermined temperature is 600 degrees C or less, The electric power system using the external combustion engine in any one of the Claims 1-4 characterized by the above-mentioned.   The power source system using an external combustion engine according to any one of claims 1 to 5, wherein the heat source means includes a solar heat collector and a combustor of biomass fuel.

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