JP6967995B2 - Engine generator system and its control method as well as cogeneration system - Google Patents

Description

The present invention relates to an engine generator system in which electric power is simultaneously supplied by a variable speed engine generator, its control method, and a cogeneration system, and particularly in a system in which a frequency conversion converter is indispensable for increasing the variable speed of the generator. The present invention relates to an engine generator system, a control method thereof, and a cogeneration system that protect the converter against an excessive current generated at the time of an accident and continue the operation without disconnecting the generator from the system.

The engine generator system according to the present invention can be used as a cogeneration system that also supplies heat by utilizing the waste heat thereof. Therefore, in the following description of the present invention, a cogeneration system will be described as an example.

A cogeneration system using an engine generator has good total energy efficiency because the waste heat of the engine can be effectively used. However, since the cogeneration system generally operates at the rated output with good electric conversion efficiency of the engine, the amount of heat and electric power supplied is constant. If electricity is generated according to demand, the heat supply capacity will change, but the thermoelectric ratio cannot be changed, and there will be excess or deficiency in either.

Therefore, as shown in Patent Document 1, a method has been proposed in which an AC excitation generator is used as an engine generator to achieve a variable speed. This utilizes the fact that the amount of exhaust heat of the engine changes by changing the ratio of the torque and the rotation speed of the engine even with the same electric output.

The AC excitation generator supplies AC to the rotor using a converter, and by changing the AC frequency, the rotation speed of the engine is made variable and the power generation frequency is kept constant so as to match the system. Such an AC excitation generator is described in, for example, Patent Document 2.

Patent Document 2 relates to a technique for protecting a converter when a voltage drop such as a power failure occurs in a power system in a wind power generation system using an AC excitation generator. The main power source in the past was a synchronous generator directly connected to the grid, and the speed of the prime mover was constant. Synchronous generators are designed so that they will not fail due to overcurrent caused by a momentary voltage drop that occurs during an abnormality such as a system accident.

On the other hand, in order to make the prime mover variable speed, a frequency conversion converter is indispensable for the generator. However, converters are prone to overcurrent failure, so protection against them is essential. This is a common issue for asynchronous power generation devices that use converters such as solar power generation, wind power generation, and batteries, and early asynchronous power generation devices were disconnected from the grid and protected in the event of a grid accident.

In recent years, due to the rapid spread of renewable energies such as solar power generation and wind power generation, the proportion of these asynchronous power generation devices has increased, and it cannot be ignored compared to the conventional main power source, synchronous generators. If all asynchronous power generators are disconnected for self-protection at the same time in the event of a system accident, the chain disconnection may spread the system accident and lead to a large-scale power outage.

Therefore, in order to stabilize the system, an asynchronous generator device using a converter is indispensable to have a function called FRT (Fault Ride Through) or LVRT (Low Voltage Ride Through) as a system interconnection requirement. Specifically, the rate of voltage drop and its duration are specified, and in the case of a system accident that is minor than the specified, it is obligatory to continue operation.

Patent No. 5868170 Japanese Unexamined Patent Publication No. 2010-21363

Since the conventional engine generator used for cogeneration used a synchronous generator, the FRT regulation was not applied, but when using a variable speed engine, a converter is indispensable, and for such an asynchronous power generator. The FRT function is indispensable. Patent Document 1 does not describe this measure.

Patent Document 2 discloses an FRT-compatible technology relating to a wind power generation device. According to this, the converter has a DC circuit between the system side converter and the rotor side converter, detects the voltage rise of the DC circuit, and realizes continuous operation by the overcurrent consumption device installed in parallel there. How to do it is shown.

Since this overcurrent consuming device is specifically a resistor, the larger the energy consumption, the larger the physique. That is, the overcurrent consuming device consumes a large amount of energy as it is used for a generator having a large output and the time required for withstanding a voltage drop is longer, so that the physique becomes larger. This is a cause that hinders the cost reduction and miniaturization of the entire converter. Moreover, in a society where renewable energy is increasing in the future, the time to withstand a voltage drop may be longer but not shortened as a grid interconnection requirement.

Moreover, even if a system accident does not occur, the voltage of the system becomes unstable due to the variable output of renewable energy. At this time, the function of maintaining the voltage is required as a cogeneration power generation system. In the past, it was possible to control the power generation end voltage by controlling the exciting current of a synchronous generator, but in this system, a control method for stabilizing the voltage has not been shown.

The present invention has been made in view of the above problems, and an object thereof is to reduce the protection circuit of the power converter in an engine generator system using a variable speed engine generator, and to make the converter compact and low cost. The purpose is to provide an engine generator system, a control method thereof, and a cogeneration system that realize the above.

From the above, in the present invention, "an engine, a generator driven by the engine, and a converter having a DC circuit to perform AC-AC conversion are provided, and the converter is a rotor or a stator of the generator. An engine generator system in which one end is connected to either end and the other end is connected to the power system, and the first means for connecting a resistor in parallel to the DC circuit of the converter in the event of a power system accident. The engine generator system is characterized by being provided with a second means for reducing the amount of fuel supplied to the engine in the event of an accident in the power system. "

Further, in the present invention, it is a "cogeneration system provided with an exhaust heat recovery device for recovering exhaust heat from an engine".

Further, in the present invention, "an engine, a generator driven by the engine, and a converter having a DC circuit to perform AC-AC conversion are provided, and the converter is either a rotor or a stator of the generator. It is a control method of an engine generator system that is operated by connecting one end to the power system and connecting the other end to the power system. It is a control method of an engine generator system characterized by reducing the amount of fuel supplied to the engine.

According to the present invention, in an engine generator system using a variable speed engine machine, a short circuit circuit (overcurrent consuming device) for protecting the exciting power converter of the AC excitation generator from overcurrent is reduced in the event of a system abnormality. can do. Further, by controlling the voltage at the end of the generator, the system can be stabilized.

The figure which shows the structural example of the cogeneration system which concerns on Example 1 of this invention. The figure which shows the time lapse of the voltage drop at the time of a power system accident. The figure which shows the time change of surplus output and surplus energy at the time of a system accident. The figure which shows the time change of the temperature of a resistor at the time of a system accident. The figure which shows the state of each part during a normal FRT operation. The figure which shows the control flow of this invention. The figure which shows the relationship between the rotation speed and fuel after the occurrence of the electric power system accident in the flow of FIG. The figure which shows the state of each part by the control flow of FIG. The figure which shows the structural example of the cogeneration system which concerns on Example 2 of this invention.

Hereinafter, examples of the present invention will be described with reference to the drawings. In addition, in all the drawings for explaining Examples, the same members are designated by the same reference numerals in principle, and overlapping description will be omitted as appropriate.

A configuration example of the cogeneration system according to the first embodiment of the present invention will be described with reference to FIG.

The cogeneration system 4 includes an engine 1, an AC excitation generator 3, a converter 2, and an exhaust heat recovery device 5 as main elements. Further, as a controller, it has an integrated control device 6, an engine control unit 601 (hereinafter referred to as an ECU), and a converter control device 602.

The integrated control device 6 is given an active power command p ^* , an reactive power command q ^*, and a thermal command Q ^* as a command signal CMD, and also receives power of the power system (active power command p and the reactive power command q). Obtained from the power meter 21, the rotation speed command ω ^* of the engine is determined and sent to the ECU 601 along with these, and the power command (active power command p ^* and reactive power command q ^* ) is given to the converter control device 602.

The engine 1 controls the shaft output by adjusting the intake amount of the air-fuel mixture 11 and the air 10 with the throttle valve 8. The ECU 601 receives feedback of the rotation speed ω of the engine from the speedometer 30 and controls the throttle valve 8 so as to ^{set the rotation speed target value ω * given by the integrated control device 6.}

The exhaust 12 of the engine is heat-exchanged by the exhaust heat recovery device 5, and the water 13 is heated to the steam 14 to supply heat to the heat load (not shown).

The shaft output of the engine 1 is converted into electric power through the AC excitation generator 3. Normally, when an engine generator controls electric power, heat cannot be controlled independently, but as described in Patent Document 1, the amount of heat supplied can be increased by increasing the rotation speed of the engine.

The AC excitation generator 3 outputs electricity from the stator 302 when the rotor 301 is driven by the engine 1. The electric output end of the stator 302 is connected to the power system 100 via the switch 50 and the breaker 52.

In the converter 2, the rotor side converter 201 and the system side converter 202 are connected by a DC circuit 203, and a capacitor 204 for absorbing voltage fluctuations in the portion of the DC circuit 203 and a protection circuit 7 are further connected. The converter 2 having such a configuration performs AC-AC conversion as a whole of the converter 2. As described above, the converter 2 is a converter having a DC circuit 203 and having a function of performing AC-AC conversion.

The protection circuit 7 is composed of a resistor 51 and a switching element 71. The rotor side converter 201 energizes the rotor 301 by energizing an alternating current. The system side converter is connected to the system via the filter circuit 53. Therefore, the generated power of the AC excitation generator 3 is the total output of the output of the stator 302 and the power input to / from the system side converter 202.

The operation of the AC excitation generator at variable speed will be described. A rotating magnetic field is generated when the rotor side converter 201 energizes the three-phase winding of the rotor 301, but since the rotor 301 itself is also rotating, the rotational speed of the magnetic field is as seen from the stator 302. It will be the total.

Assuming that the direction of rotation of the shaft and the direction of the rotating magnetic field generated by the rotor 301 match, the AC frequency of the rotor 301 is set to _rotor , the speed of the rotor is N (r / min), and the number of pole pairs is P / 2. _{The frequency fstator of the} AC magnetic field received by the stator 302 can be expressed by the following equation (1).
[Number 1]
f _stator = N / 60 * (P / 2) + _rotor : ... (1)
If the AC frequency _{rotor is set} to zero, that is, DC is supplied, the operation is the same as that of the synchronous generator. The rotor side converter 201 can apply alternating current of any voltage, phase, and alternating current frequency _forward. As a result, even if the rotation speed N of the engine 1 changes, it is possible to generate power at the same frequency as the alternating current of the external power system 100 and in synchronization.

Such an AC excitation generator 3 can control the torque, that is, the active power p of the AC excitation generator 3 by changing the energization phase of the rotor 301. Further, it is also possible to change the exciting magnetic flux by changing the current value of the rotor 301 and change the voltage of the stator 302, that is, to control the reactive power q. The rotor side converter 201 controls the AC side to an arbitrary frequency and voltage, but it is premised that the voltage of the DC circuit unit 203 in that case is constant.

On the other hand, the system side converter 202 controls to input / output power to / from the system side by switching so that the voltage Vdc of the DC circuit unit 203 becomes constant. At this time, the system-side converter 202 can independently change the system-side voltage, that is, control the reactive power q.

In this way, the reactive power q of the generator can be adjusted by the rotor side converter, and the reactive power q can be adjusted by the system side converter as well. Therefore, the system using the AC excitation generator 3 supplies a larger reactive power q than before. can do.

The converter control device 602 appropriately controls the rotor side converter 201 and the system side converter 202 in order to achieve the given power commands (active power command p ^* and reactive power command q ^*). In this case, the control target is the energization phase to the rotor 301, the current value of the rotor 301, the voltage on the system side in the system side converter 202, and the like.

Next, the FRT operation at the time of a system accident in the configuration of FIG. 1 will be described.

The rotor side converter 201 and the system side converter 202 constituting the converter 2 are generally composed of semiconductor devices such as IGBTs, but since there is an upper limit to the amount of energization and the withstand voltage thereof, the limits set in normal operation are set. I'm driving below. This is to prevent the semiconductor device from having dielectric breakdown exceeding the withstand voltage and being damaged due to temperature rise due to overcurrent. The resistance of converters to overcurrent and overvoltage is extremely low compared to generators, which are the main players in conventional system power supplies. Therefore, it is essential to protect the converter in the event of an abnormality such as a system short circuit.

Therefore, the AC excitation generator 3 using the converter 2 is often designed so as to be easily disconnected in the event of a system accident. However, if the number of power sources that use converters, such as solar power generation, wind power generation, and storage batteries, increases in the future, there is a possibility that power outages will spread in a chain reaction if all of them are disconnected at the time of the accident. In order to avoid this, the system operator has come to set a stipulation for continuation of operation (Fault Ride Through: FRT) for each generator against an instantaneous voltage drop.

FIG. 2 shows the passage of time (horizontal axis) of the voltage drop (vertical axis) at the time of a power system accident. This example shows an example in which the voltage 81 drops due to the occurrence of a power system accident at time t0, the accident is eliminated at time t10, and then the voltage is restored to the original voltage at time t20. The AC excitation generator 3 using the converter 2 shown in FIG. 1 is expected to continue the operation of the converter 2 until the voltage is recovered.

In FIG. 2, the FRT regulation for continuation of operation is shown by the dotted line 80. The FRT regulation of the dotted line 80 defines the minimum voltage 83 and its duration 82 after the system accident, the allowable range 84 of the voltage drop after the accident has converged, the convergence time of the system accident, and the like. If the voltage at the time of the actual system accident is, for example, the voltage waveform 81, it should be regarded as a system accident minorer than the FRT regulation shown by the dotted line 80, and the operation should be able to be continued for the voltage drop within this range.

At the time of a system accident, the voltage at the accident point drops, but the voltage of the stator 302 is high, so an overcurrent flows in the power system. Further, an overcurrent tends to flow from the rotor 301 to the converter 2. In both cases, the energy received from the shaft of the engine 1 is about to be converted into electric power, so that the current must increase as the voltage decreases, but the converter 2 cannot pass an overcurrent.

In such a state, when a protective relay device (not shown) opens the breaker 52 to eliminate an accident in the power system, the circuit of the electric system is cut off, so that the energy loses its place and the rotation speed ω of the rotor 301 is lost. Will rise and be converted into kinetic energy, or energy will be stored in the capacitor 204 of the DC circuit unit 203 and will explode if the capacity of the capacitor is exceeded. There is also a concern that the rotating machine will be damaged due to over-rotation. Further, there is a concern that the semiconductor element constituting the converter 2 may be destroyed.

In normal operation, the system side converter 202 controls the alternating current on the system side so as to keep Vdc constant. However, since the converter has an upper limit of the current capacity, when the voltage drops, the power cannot be released to the system, and the voltage of the DC circuit 203 rises. In order to avoid this, the protection circuit 7 is installed in parallel with the DC circuit section. The protection circuit 7 detects the voltage of the DC circuit with the voltmeter 20A, and consumes energy when this voltage exceeds a predetermined voltage. The protection circuit 7 includes a resistor and a switching element 71. Normally, the switching element 71 is turned off, and in the case of overvoltage, the switch is turned on, and the resistor 51 consumes energy.

However, the temperature of the resistor 51 rises by the amount of energy consumed. Resistors also have a heat resistance limit. A short-time temperature rise of several seconds at the longest, such as FRT, can only be absorbed by the heat capacity of the device, which increases the size of the resistor. This is costly and has the problem that the equipment cannot be miniaturized. In the future, as the number of power supplies with converters connected to the grid increases, the requirements for FRT will become more stringent, and the resistors will increase as the voltage drop time during which operation can be continued increases.

Therefore, in the present invention, in order to make the resistor of the protection circuit 7 smaller, the protection circuit 7 is also combined with the fuel control of the engine so as to reduce the energy input from the shaft of the engine to the generator 3 during the FRT operation. It reduces energy consumption in Japan. A specific operation example will be described below.

FIG. 3 shows the time change of the surplus output and the surplus energy at the time of the system accident. The surplus output 86 has a shape in which the power generation end voltage of FIG. 2 is substantially upside down. Normally, the mechanical input from the shaft is output as the product of the current and voltage of the generator and is in a steady state, but when the voltage of the generator drops, the current does not suddenly increase due to inductance etc. Cannot output. This will be called surplus power. The sum of the surplus output 86 over time is the surplus energy 87.

The surplus energy 87 is directly converted into the heat of the resistor 51, the average temperature thereof is equal to the surplus energy curve in terms of short-time adiabatic approximation, and the temperature of the resistor is the temperature rise curve 90A shown in FIG. .. FIG. 4 shows the time change of the temperature of the resistor at the time of a system accident. The temperature rise curves 90B and 90C have these resistors in two parallels and three parallels, and the temperature decreases as the number of parallels increases. However, this increases the size of the protection circuit and hinders the miniaturization of the converter itself.

FIG. 5 shows the state of each part during normal FRT operation. Specifically, it shows the time change of the temperature rise curve 90A of the resistor, the DC voltage 95A, the rotation speed 93A, the mixer flow 92A, and the power generation end voltage 81 at the time of a system accident.

In this example, it is assumed that the output is not adjusted by the throttle valve 8 of the engine 1 at the time of a system accident and the air-fuel mixture amount 92A input to the engine is constant. In this case, when the AC end voltage waveform drops as 81 due to a system accident, the voltage Vdc of the DC circuit unit 203 rises as shown in 95A, and is a protection circuit so that it becomes constant when it rises to a threshold of 105%, for example. 7 operates the switching element 71. During that time, energy is consumed by the resistor 51 and the temperature rises like 90A. Since all the excess energy is consumed by the protection circuit 7, the rotation speed can be kept constant as shown in 93A. When the system accident is settled, the surplus energy disappears, so the DC voltage Vdc drops and returns to steady operation.

On the other hand, the control flow of the present invention is shown in FIG. In the first processing step S1 of FIG. 6, it is confirmed that the DC voltage Vdc rises at the time of a system accident and exceeds a threshold value of, for example, 105%, and when the threshold value is exceeded, the protection circuit 7 is started to be energized in the processing step S2. The energization of the protection circuit 7 means that the resistor 51 is connected to the DC circuit 203 by the switching element 71 of FIG. 1, and heat is generated due to the power consumption of the resistor. In the processing step S3, the temperature of the protection circuit 7 is monitored, and when the temperature exceeds the threshold value T7 of 60 ° C., the throttle valve 8 is once closed in the processing step S4 to make the fuel of the air-fuel mixture almost zero. Since the input from the engine shaft to the generator 3 is lost due to the fuel cut, the DC voltage drops, so that the energization to the protection circuit 7 is stopped in the processing step S5, and at the same time, the rotation speed starts to drop. The energization stop of the protection circuit 7 means that the resistor 51 is disconnected from the DC circuit 203 by the switching element 71 of FIG.

In the processing step S6, the rotation speed is continuously observed, and in the determination of the processing steps S7 and S8, the control according to the magnitude of the rotation speed is executed.

First, in the processing step S7, when the rotation speed does not drop to 100%, the process proceeds to the processing step S12, and thereafter, the fuel cut in the processing steps S4 and S5 and the stop processing of the protection circuit 7 are repeatedly executed. In this way, when the rotation speed exceeds 100%, the protection circuit 7 is operated, the fuel is cut, and the rotation speed is controlled.

When it is confirmed that the rotation speed is 100% or less in the processing step S7, it is further confirmed in the processing step S8 whether or not the rotation speed is 95% or more. If the rotation speed is in the range of 95 to 100%, the fuel is set to 50% in the processing step S9, and if the rotation speed is 95% or less, 100% of the fuel is instructed in the processing step S10.

Further, in the processing step S11, the time ΔT after the energization of the protection circuit 7 is completed is measured, and if the protection circuit 7 does not operate for 2 seconds, for example, it is considered that the system accident has ended and the FRT mode is terminated. After that, as usual, the output of the engine is controlled to a constant rotation speed by droop control.

FIG. 7 shows the relationship between the rotation speed and the fuel after the occurrence of the power system accident in the flow of FIG. 6, for example, in the first stage st1 where the rotation speed is 100% or more, the fuel is 0% and the rotation speed is 100%. In the second stage st2 in the range of 95% to 95%, the fuel is 50%, and in the third stage st3 where the rotation speed is 95% or less, the fuel is 100%. Further, the decrease in the rotation speed after the control causes a delay depending on the case, but after the time ΔT after the energization to the protection circuit 7 is completed, the control shifts to the control determined by the ECU 601.

In the flow of FIG. 7, in short, in the event of an AC system accident, the converter 2 is continued to operate by connecting a resistor to the DC circuit 203 to consume heat, and the AC excitation generator is cut or reduced in fuel. The difference between the mechanical input and the electric output of No. 3 is suppressed.

FIG. 6 exemplifies an increase in the DC voltage Vdc of the DC circuit 203 as a condition for connecting a resistor to the DC circuit 203, but this can be appropriately selected from the events that occur in response to the occurrence of an accident in the power system. It is possible. For example, the voltage drop of the power system directly, the output of the protective relay for detecting an accident, and the like. Further, as a condition for stopping or reducing the supply of fuel, the fact that the temperature of the protection circuit 7 exceeds the threshold value T7 of 60 ° C. is used, but in addition to this, the DC voltage rise of the DC circuit 203 and the protection circuit 7 are used. Events such as a temperature rise due to operation and a DC current rise in the DC circuit 203 can be used. It should be noted that the temperature is adopted in the embodiment of FIG. 6 because the temperature is information that can be detected inside the engine generator system and does not require an interlock to be taken in from the outside.

In short, the condition for connecting a resistor to the DC circuit 203 or the condition for reducing the fuel supply is appropriately selected from the events that occur incidentally when the voltage of the power system drops due to the occurrence of an accident in the power system. do it. In the present invention, the energy consumption by connecting a resistor to the DC circuit 203 at the time of an accident and the suppression of the mechanical input in order to reduce the difference between the mechanical input and the electric output in the engine and the generator are executed together. It enables stable operation continuation after an accident.

FIG. 8 shows the state of each part according to the control flow of FIG. Here, the DC voltage 95B, the rotation speed 93B, the protection circuit temperature 90D, the fuel flow rate 92B, and the power generation end voltage 81 at the time of a system accident are illustrated to show the time change.

First, when the system voltage 81 drops at time t0, the DC voltage Vdc 95B rises and the protection circuit 7 starts to be energized, so that the temperature of the protection circuit 7 rises like 90D. When the temperature of the protection circuit 7 reaches the threshold value of 60 ° C. at time t1, the fuel flow rate 92B is set to zero by the processing of the processing step S3 of FIG. As a result, since there is no shaft input to the generator, the DC voltage 95B and the rotation speed 93B decrease.

According to the determination process in the process step S8 of FIG. 6, when the rotation speed is 95% or more and 100% or less, the process step S9 operates to set the fuel to 50% at time t2. As a result, the shaft input exceeds the electric output, so that the rotation speed increases.

According to the determination process in the process step S7 of FIG. 6, when the rotation speed exceeds 100% at time t3, the protection circuit 7 is started to be energized (process step S12), and the fuel is squeezed at the same time (process step S4). This reduces the rotation speed. This operation is repeated.

After time t3, when the system voltage 81 is restored, the energy that can be output to the system increases, so the engine output needs to be restored. This is because the time from the end of the last energization of the protection circuit 7 is measured in the processing step S11 of FIG. 6, and if the protection circuit does not operate even after 2 seconds have passed, the system accident has converged. It is regarded as, and the FRT mode is terminated. As a result, the engine performs droop control with respect to the frequency so that the normal rotation speed is controlled to be constant.

In the above example, the temperature of the protection circuit 7 is determined to control the throttle valve, but it is easy to estimate the temperature by time integration of the current value of the circuit 7, and the same can be achieved by measuring this. The effect can be obtained.

FIG. 9 shows a configuration example of the cogeneration system according to the second embodiment of the present invention. The difference from FIG. 1 is that the generator 3B connected to the engine is not an AC excitation generator but a magnet field generator. In this case, the converter capacity of the converter 2 needs to be the same as the maximum output of the engine, and since all the outputs of the generator pass through the converter 2, there is a drawback that the loss of the converter becomes large. However, also in this case, the overcurrent protection circuit 7 is also installed in the circuit that protects the converter 2. The operation is the same as that shown in the first embodiment.

The generator 3 of the first and second embodiments is a generator 3 in which the rotor 301 is driven by an engine, and either the rotor 301 or the stator 302 has a DC circuit 203 and is an alternating current. It is connected to the power system 100 via a converter 2 having a function of performing AC conversion. The converter 2 is a converter provided with a DC circuit 203 between the two sets of converters 201 and 202.

1: Engine 2: Converter 3: AC excitation generator 3B: Magnet field generator 4: Cogeneration system 5: Exhaust heat recovery device 6: Integrated control device 7: Protection circuit 8: Throttle valve 9: Switch:
10: Air 11: Fuel 12: Exhaust 13: Water 14: Steam 20A: Voltmeter 20B: Voltmeter 21: Power meter 30: Rotation speed meter 40: Integrated control device 50: Switch 51: Resistor 52: Breaker 53 : Filter circuit 71: Switching element 80: FRT regulation 81: Example of power generation end voltage at the time of system accident 82: Duration of FRT regulation minimum voltage 83: FRT regulation minimum voltage 84: Allowable range at FRT regulation voltage convergence 85: FRT regulation System accident convergence time 86: Surplus output 87: Surplus energy cumulative 90A: Resistor temperature rise curve, number of parallel circuits 1
90B: Resistor temperature rise curve, number of parallel circuits 2
90C: Resistor temperature rise curve, number of parallel circuits 1
90D: Temperature rise curve of resistor according to the present invention 92A: Fuel flow rate during FRT of conventional engine generator 92B: Fuel flow rate during FRT of engine according to the present invention 93A: Rotation speed of engine during conventional FRT 93B: This Engine rotation speed 95A during FRT of the present invention: Vdc voltage curve 95B during conventional FRT: Vdc voltage curve 100 during FRT of the present invention: Power system 201: Rotor side converter 202: System side converter 203: DC circuit 204 : DC condenser 301: AC excitation generator rotor 302: AC excitation generator stator 601: Engine control unit (ECU)
602: Converter controller

Claims (14)

It comprises an engine, a generator driven by the engine, and a converter having a DC circuit to perform AC-AC conversion, the converter having one end connected to either the rotor or the stator of the generator. It is an engine generator system that is operated by connecting the other end to the power system.
It is characterized by including a first means for connecting a resistor in parallel to the DC circuit of the converter in the event of a power system accident, and a second means for reducing the amount of fuel supplied to the engine in the event of a power system accident. Engine generator system. The engine generator system according to claim 1.
The condition for connecting a resistor in parallel to the DC circuit in the event of a power system accident, or / or the condition for reducing the amount of fuel supplied to the engine in the event of a power system accident, is that the voltage of the power system drops due to the occurrence of a power system accident. An engine generator system characterized in that it is selected from the events that accompany it. The engine generator system according to claim 1 or 2.
The conditions for connecting a resistor in parallel to the DC circuit in the event of an accident in the power system are an increase in the DC voltage of the DC circuit, a decrease in the voltage of the power system, and the output of a protective relay that detects the accident. .. The engine generator system according to claim 1 or 2.
The conditions for reducing the amount of fuel supplied to the engine in the event of a power system accident are an increase in the DC voltage of the DC circuit, a temperature increase due to parallel connection of resistors, and an increase in the DC current of the DC circuit. Generator system. The engine generator system according to any one of claims 1 to 4.
The converter is an engine generator system, characterized in that one end is connected to the rotor of the generator, and the other end of the converter and the stator of the generator are connected to the power system. The engine generator system according to any one of claims 1 to 4.
The converter is an engine generator system, characterized in that one end is connected to the stator of the generator and the other end of the converter is connected to the power system. The engine generator system according to any one of claims 1 to 6.
The second means is an engine generator system characterized in that when the amount of fuel supplied to the engine in the event of an accident in the power system is reduced, the amount is reduced according to the rotation speed of the engine. The engine generator system according to any one of claims 1 to 7.
A third means for controlling the rotation speed command of the engine and the amount of fuel supplied to the engine from the rotation speed of the engine is provided.
The first means disconnects the resistance connected in parallel to the DC circuit after the fuel amount is reduced by the second means, and further controls the fuel amount by the third means after a predetermined time elapses. An engine generator system characterized by the transition to. The engine generator system according to any one of claims 1 to 8.
In the converter, the DC circuit is connected between the converter on the generator side and the converter on the power system side, and the converter on the generator side changes the power factor of the stator end of the generator, and the converter on the power system side. An engine generator system characterized in that the voltage at the output end of the generator is controlled by controlling the reactive power on the power system side. The engine generator system according to any one of claims 1 to 9.
The condition for connecting a resistor in parallel to the DC circuit in the event of a power system accident is a voltage rise in the DC circuit, and the condition for reducing the amount of fuel supplied to the engine in the event of a power system accident is connected in parallel to the DC circuit. An engine generator system characterized by heat generated by resistance. A cogeneration system in which the engine generator system according to any one of claims 1 to 10 is provided with an exhaust heat recovery device for recovering waste heat from the engine. It comprises an engine, a generator driven by the engine, and a converter having a DC circuit to perform AC-AC conversion, the converter having one end connected to either the rotor or the stator of the generator. It is a control method of an engine generator system that is operated by connecting the other end to the power system.
A control method for an engine generator system, which comprises connecting a resistor in parallel to the DC circuit in the event of an electric power system accident and reducing the amount of fuel supplied to the engine in the event of an electric power system accident. The control method for the engine generator system according to claim 12.
A control method for an engine generator system, characterized in that when the amount of fuel supplied to the engine in the event of an accident in the power system is reduced, the amount is reduced according to the rotation speed of the engine. The control method for the engine generator system according to claim 12 or 13.
A third means for controlling the rotation speed command of the engine and the amount of fuel supplied to the engine from the rotation speed of the engine is provided.
After the fuel amount is reduced, the resistance connected in parallel to the DC circuit is disconnected, and after a predetermined time elapses, the fuel amount is controlled according to the difference between the engine rotation speed command and the engine rotation speed. A control method for an engine generator system, characterized in that it does.

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