Engine generator system, control method thereof and cogeneration system
阅读说明：本技术 引擎发电机系统和其控制方法以及热电联供系统 (Engine generator system, control method thereof and cogeneration system ) 是由 日野德昭 木村守 岛田敦史 于 2018-11-28 设计创作，主要内容包括：提供在使用可变速引擎发电机的引擎发电机系统中使电力转换器的保护电路变小并实现转换器的小型、低成本的引擎发电机系统和其控制方法以及热电联供系统。引擎发电机系统具备引擎、被引擎驱动的发电机以及具有直流电路且进行交流-交流变换的转换器,转换器以一端连接于发电机的转子或者定子且另一端连接于电力系统的方式被运用,引擎发电机系统的特征在于,具备：第1部件,在电力系统的事故时对转换器的直流电路并联连接电阻；以及第2部件,在电力系统的事故时减少对引擎供给的燃料量。(Provided are an engine generator system, a control method thereof, and a cogeneration system, wherein a protection circuit of a power converter is reduced and the size and cost of the converter are reduced in the engine generator system using a variable speed engine generator. An engine generator system including an engine, a generator driven by the engine, and a converter having a dc circuit and performing ac-ac conversion, the converter being operated such that one end is connected to a rotor or a stator of the generator and the other end is connected to a power system, the engine generator system comprising: a 1 st component for connecting a resistor in parallel to a direct current circuit of a converter in the event of an accident in a power system; and a 2 nd component that reduces the amount of fuel supplied to the engine in the event of an accident of the power system.)
1. An engine generator system including an engine, a generator driven by the engine, and a converter having a dc circuit and performing ac-ac conversion, the converter being operated such that one end is connected to a rotor or a stator of the generator and the other end is connected to a power system, the engine generator system comprising:
a 1 st component for connecting a resistor in parallel to the dc circuit of the converter in the event of an accident in the power system; and
and a 2 nd component for reducing the amount of fuel supplied to the engine in the event of an accident of the power system.
2. The engine generator system of claim 1,
the condition for connecting a resistance in parallel to the direct-current circuit at the time of an accident in the power system or/and the condition for reducing the amount of fuel to be supplied to the engine at the time of an accident in the power system are selected from phenomena accompanying the voltage drop in the power system due to the occurrence of an accident in the power system.
3. The engine generator system of claim 1 or 2,
the condition for connecting a resistor in parallel to the dc circuit in the event of an accident in the power system is a rise in dc voltage of the dc circuit, a drop in voltage of the power system, and an output of a protective relay for detecting the accident.
4. The engine generator system of claim 1 or 2,
the condition for reducing the amount of fuel supplied to the engine in the event of an accident in the power system is a rise in the dc voltage of the dc circuit, a rise in temperature associated with parallel connection of resistors, and a rise in the dc current of the dc circuit.
5. An engine generator system of any one of claims 1 to 4,
one end of the converter is connected to the rotor of the generator, and the other end of the converter and the stator of the generator are connected to a power system.
6. An engine generator system of any one of claims 1 to 4,
one end of the converter is connected to the stator of the generator, and the other end of the converter is connected to the power system.
7. An engine generator system of any one of claims 1 to 6,
the 2 nd element is set to a reduction amount corresponding to the rotation speed of the engine when the amount of fuel supplied to the engine is reduced in the event of an accident in the power system.
8. An engine generator system of any one of claims 1 to 7,
the engine generator system is provided with a 3 rd component, the 3 rd component controls the amount of fuel supplied to the engine according to the rotation speed command of the engine and the rotation speed of the engine,
the 1 st component decouples the resistance connected in parallel with the direct current circuit after the amount of fuel is reduced by the 2 nd component, and then shifts to the control of the amount of fuel by the 3 rd component after a predetermined time elapses.
9. An engine generator system of any one of claims 1 to 8,
the converter connects the direct current circuit between a generator-side converter and an electric power system-side converter, changes a power factor of a stator terminal of the generator by the generator-side converter, and controls reactive power of an electric power system side by the electric power system-side converter, thereby controlling a voltage of an output terminal of the generator.
10. An engine generator system of any one of claims 1 to 9,
the condition for connecting a resistor in parallel to the dc circuit at the time of an accident of the power system is a voltage rise of the dc circuit, and the condition for reducing the amount of fuel supplied to the engine at the time of an accident of the power system is heat generation caused by the resistor connected in parallel to the dc circuit.
11. A cogeneration system, characterized in that,
the engine generator system according to any one of claims 1 to 10, further comprising an exhaust heat recovery device for recovering exhaust heat from the engine.
12. A method for controlling an engine generator system including an engine, a generator driven by the engine, and a converter having a DC circuit and performing AC-AC conversion, the converter being operated so that one end thereof is connected to a rotor or a stator of the generator and the other end thereof is connected to a power system,
a resistor is connected in parallel to the DC circuit in the event of an accident in the power system, and the amount of fuel supplied to the engine is reduced in the event of an accident in the power system.
13. The control method of an engine generator system according to claim 12,
when the amount of fuel supplied to the engine is reduced in the event of an accident in the power system, the amount of fuel is reduced in accordance with the number of revolutions of the engine.
14. The control method of an engine generator system according to claim 12 or 13,
a 3 rd member for controlling the amount of fuel supplied to the engine based on the rotational speed command of the engine and the rotational speed of the engine,
the control method includes the steps of splitting a resistor connected in parallel with the direct current circuit after the amount of fuel is reduced, and further shifting to control of the amount of fuel corresponding to a difference between a rotational speed command of the engine and a rotational speed of the engine after a predetermined time has elapsed.
Technical Field
The present invention relates to an engine generator system (engine generator system) for supplying electric power by a variable speed engine generator, a control method thereof, and a cogeneration system (co-generation system), and more particularly, to an engine generator system, a control method thereof, and a cogeneration system, in which an excessive current protection converter generated at the time of a system accident is protected in a system requiring a frequency conversion converter for changing the speed of a generator, and a generator is continuously operated without disconnecting the generator from the system.
Background
The engine generator system according to the present invention can also be used as a cogeneration system that uses exhaust heat and also supplies heat. Therefore, in the following description of the present invention, a cogeneration system will be described as an example.
The cogeneration system using the engine generator can effectively use the exhaust heat of the engine, and therefore has excellent overall energy efficiency. However, since the cogeneration system is generally operated at a rated output with good electrical conversion efficiency of the engine, the amounts of heat and electric power supplied are constant. When power is generated in accordance with demand, the heat supply capacity also changes, but the thermoelectric ratio cannot be changed, and either one of the two is increased or decreased.
Therefore, as shown in patent document 1, a method of using an ac excitation generator in an engine generator to enable variable speed is proposed. This makes use of the following principle: even with the same electrical output, the amount of heat removed by the engine varies by varying the ratio of torque to speed of the engine.
The ac-excited generator supplies ac to the rotor using a converter, and by changing the ac frequency thereof, the rotational speed of the engine is made variable while the power generation frequency is kept constant in a manner matching the system. For example,
On the other hand, in order to make the prime mover variable in speed, a frequency conversion converter is required in the generator. However, the converter is prone to malfunction with respect to overcurrent, so protection against overcurrent is essential. This is a common problem in asynchronous power generation devices using converters such as solar power generation, wind power generation, and batteries, and the initial asynchronous power generation device is disconnected from the system to be protected in the event of a system failure.
In recent years, due to rapid spread of renewable energy sources such as solar power generation and wind power generation, the proportion of these asynchronous power generation devices has increased and has become non-negligible compared to synchronous generators, which are the main power sources of the related art. If all the asynchronous power generation devices are disconnected at the same time for self-protection in the event of a system accident, the system accident is expanded due to the chain disconnection, which may lead to a large-scale power failure.
Therefore, in order to stabilize the system, the asynchronous generator device using the converter requires a function of FRT (Fault Ride Through) or LVRT (Low Voltage Ride Through) as a system interconnection requirement. Specifically, the following must be specified: the voltage drop rate and the duration thereof are specified, and the operation is continued in the case of a system accident that is less than the specified value.
Disclosure of Invention
The FRT specification is not applicable because the conventional engine generator used for cogeneration uses a synchronous generator, but a converter is required when a variable speed engine is used, and the FRT function is essential for such an asynchronous power generation device. Patent document 1 does not describe any countermeasure.
Since the overcurrent consumption device is specifically a resistor, the larger the consumed energy, the larger the volume. That is, the overcurrent consumption device is required to have a larger output for a generator and a longer time to overcome the voltage drop, and consumes a larger amount of energy, resulting in a larger volume. This is a factor that hinders cost reduction and size reduction of the entire converter. In addition, in the society where renewable energy sources increase in the future, as a system interconnection requirement, the time for overcoming the voltage drop may be long but not short.
In addition, even if a system accident does not occur, the voltage of the system becomes unstable due to the fluctuating output of the renewable energy source. In this case, a function of maintaining voltage is required as a cogeneration power generation system. Conventionally, the voltage at the power generation end can be controlled by field current control of a synchronous generator, but a control method for stabilizing the voltage in this system is not shown.
The present invention has been made in view of the above problems, and an object thereof is to provide a small-sized and low-cost engine generator system and a control method thereof, and a cogeneration system, in which a protection circuit of a power converter is reduced and the converter is realized in an engine generator system using a variable speed engine generator.
As described above, the present invention provides "an engine generator system including an engine, a generator driven by the engine, and a converter having a dc circuit and performing ac-ac conversion, the converter being operated such that one end is connected to a rotor or a stator of the generator and the other end is connected to a power system, the engine generator system including: a 1 st component for connecting a resistor in parallel to a direct current circuit of a converter in the event of an accident in a power system; and a 2 nd component that reduces the amount of fuel supplied to the engine at the time of an accident of the power system.
The present invention is also directed to a cogeneration system including an exhaust heat recovery device that recovers exhaust heat from an engine.
Further, the present invention provides "a method of controlling an engine generator system including an engine, a generator driven by the engine, and a converter having a dc circuit and performing ac-ac conversion, the converter being operated such that one end is connected to a rotor or a stator of the generator and the other end is connected to a power system", the method being characterized in that a resistor is connected in parallel to the dc circuit at the time of an accident of the power system, and an amount of fuel supplied to the engine is reduced at the time of the accident of the power system ".
According to the present invention, in an engine generator system using a variable speed engine device, a short-circuit (overcurrent consuming device) of a field power converter for protecting an ac field generator from an overcurrent at the time of a system abnormality can be reduced. In addition, the system can be stabilized by controlling the voltage at the generator end.
Drawings
Fig. 1 is a diagram showing a configuration example of a cogeneration system according to embodiment 1 of the present invention.
Fig. 2 is a graph showing the lapse of time during which the voltage drops in the event of a power system accident.
Fig. 3 is a graph showing temporal changes in the remaining output and the remaining energy at the time of a system accident.
Fig. 4 is a graph showing a temporal change in the temperature of the resistor at the time of a system accident.
Fig. 5 is a diagram showing states of respective parts in a normal FRT operation.
Fig. 6 is a diagram showing a control flow of the present invention.
Fig. 7 is a diagram showing a relationship between the rotation speed and the fuel after the occurrence of the power system accident in the flowchart of fig. 6.
Fig. 8 is a diagram showing states of respective portions based on the control flow of fig. 6.
Fig. 9 is a diagram showing a configuration example of the cogeneration system according to
(symbol description)
1: an engine; 2: a converter; 3: an AC excitation generator; 3B: a magnet excited generator; 4: a cogeneration system; 5: a waste heat recovery device; 6: a comprehensive control device; 7: a protection circuit; 8: a throttle valve; 9: a shutter; 10: air; 11: a fuel; 12: exhausting; 13: water; 14: steam; 20A: a voltmeter; 20B: a voltmeter; 21: a power meter; 30: a tachometer; 40: a comprehensive control device; 50: a shutter; 51: a resistor; 52: a cutter; 53: a filter circuit; 71: a switching element; 80: FRT regulation; 81: an example of a power generation terminal voltage at the time of a system accident; 82: FRT specifies the duration of the lowest voltage; 83: FRT specifies the minimum voltage; 84: FRT specifies an allowable range for voltage convergence; 85: FRT stipulates the system accident end time; 86: residual output; 87: accumulating the residual energy; 90A: temperature rise curve of the resistor, number of parallel circuits 1; 90B: temperature rise curve of the resistor, number of
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings for explaining the embodiments, the same components are denoted by the same reference numerals in principle, and overlapping descriptions are appropriately omitted.
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