JP2010220450A - Engine power generation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine power generation device advantageous to inhibit the engine rotary speed from excessively rising for stopping the power supply to a system related part comprising commercial power and load. <P>SOLUTION: The engine power generation device 1 includes: an engine 2; a power generation device 3; a resistor 4; and an inverter 5 having a converter 501that converts the AC power of the power generation device to the DC power and an inverter output circuit 504 that converts the DC power to the AC power of predetermined frequency to supply the power to the system related part 60. A control means controls the energization amount to the resistor 4 per unit time and controls resistance energization to start energization to the resistor 4 before the gate of the inverter output circuit 504 is blocked or at the same time when the gate is blocked for stopping the power supply to the system related part 60. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an engine power generator that feeds power generated by rotating a generator with an engine to a grid interconnection unit.

  The engine power generator includes an engine, a generator that is rotated by the engine to generate AC power, and an inverter. The inverter includes a converter that converts the AC power of the generator into DC power, and an inverter output circuit that converts the DC power into AC power having a predetermined frequency. The inverter output circuit feeds electric power to a grid interconnection unit including a local load and a commercial power source.

  The technique according to Patent Document 1 discloses the engine power generator described above. According to this, the engine set rotational speed is set to a lower predetermined rotational set value at the timing when the system disconnection occurs, and engine overshoot is prevented. According to this, when a malfunction occurs on the commercial power supply side, the inverter disconnects (turns off) the breaker and stops power feeding. At this time, the fuel supply to the engine is stopped, the mechanical brake is operated, and the like based on the disconnection signal obtained by disconnecting the inverter from the system. However, the engine and the brake are mechanical parts, and the control response is slow compared to the electric parts. For this reason, as a result, the engine rotation speed becomes excessively high as the power supply is stopped, and the upper limit value of the engine rotation speed may be easily exceeded. In this case, the normal operation of the engine or the generator may be impaired.

Japanese Patent No. 3689313

  The present invention has been made in view of the above circumstances, and suppresses a rapid and excessive increase in engine rotation speed when stopping power supply to the grid interconnection while maintaining engine rotation. It is an object of the present invention to provide an engine power generator that is advantageous to the above.

  The present inventor has been diligently developing an engine power generator that feeds power to a grid interconnection unit including a commercial power source and a power load. When the gate block of the inverter output circuit of the inverter is stopped due to the situation of the grid connection, etc., and the power supply to the grid connection section is stopped, before the gate block is performed or simultaneously with the gate block, to the resistor If energization is started, an engine load is generated based on the energization of the resistor before or at the same time as the gate block, so that the engine speed is prevented from increasing rapidly and excessively. The present invention was completed.

  In other words, the engine power generator according to the present invention is an engine power generator that feeds power to a grid interconnection unit composed of a commercial power source and a power load, and includes (i) an engine driven by fuel combustion, and (ii) rotation by the engine. A generator for generating AC power, (iii) a resistor capable of passing a current based on the electric power generated by the generator, and (iv) a converter and DC power for converting AC power of the generator into DC power An inverter having an inverter output circuit that converts AC power into a predetermined frequency and supplying power to the grid interconnection unit, and (v) controlling the energization amount per unit time of energizing the resistor, When stopping the power supply to the grid interconnection by performing the gate block, the resistor is connected to the resistor before the gate block of the inverter output circuit or simultaneously with the gate block. Characterized by comprising a control means for performing resistance energization control to start.

  The inverter converts AC power of the generator into DC power by a converter, converts the DC power into AC power of a predetermined frequency by an inverter output circuit, and feeds power to the grid interconnection unit. In order to stop the power supply to the grid interconnection unit composed of the commercial power source and the load due to circumstances related to the grid interconnection, the control means stops the power feed by performing the gate block of the inverter output circuit of the inverter. At this time, as the power supply to the grid interconnection unit is stopped, the engine load is drastically reduced, and therefore the engine rotation speed may be increased rapidly and excessively.

  With respect to this point, according to the present invention, when stopping power feeding to the grid interconnection part due to circumstances relating to grid interconnection, the control means performs power supply to the grid interconnection part by performing a gate block of the inverter output circuit of the inverter. Stop. In this case, the control means performs resistance energization control for starting energization of the resistor before or simultaneously with the gate block of the inverter output circuit.

  Thereby, the big fluctuation | variation of an engine load is suppressed before and behind the stop which stops the electric power feeding to a grid connection part. As a result, the possibility that the engine speed rapidly and excessively increases after power supply is stopped is suppressed. In this way, large fluctuations in engine speed are suppressed. A gate block means that the inverter output circuit of an inverter stops the electric power feeding from an inverter to a grid connection part.

  In the resistance energization control described above, the current energized to the resistor may be direct current, alternating current, or pulse energization. Here, the current value can be controlled, for example, by the current value itself or by duty control. In the duty control, the current value can be set based on the duty value. If the duty value is high, the current value supplied to the resistor increases. If the duty value is low, the current value supplied to the resistor is reduced.

  As described above, according to the present invention, when a malfunction that stops power supply to the grid interconnection unit is detected, the control means controls the resistance energization before the gate block of the inverter output circuit or simultaneously with the gate block. To implement. Here, “simultaneously performing the gate block” means simultaneously with the timing at which the command to perform the gate block is output. “Before a gate block” means within a predetermined time before the timing at which a command to perform a gate block is output. Examples of the predetermined time include 3 seconds, 2 seconds, 1 second, 500 milliseconds, and 300 milliseconds. However, it is not limited to these.

  Preferably, in the resistance energization control, the control unit can start energization to the resistor and, after the start, can decrease the current value to energize the resistor with time. In this case, during the resistance energization control, it is preferable that the engine rotation speed is controlled to gradually decrease as time elapses while the engine rotation is maintained as power supply to the power load or the commercial power source is stopped. . In this case, since the rotation of the engine is maintained, it is possible to quickly resume the power supply to the grid interconnection unit.

  Preferably, when the resistance energization control is performed, the control means can determine that the resistor is abnormal when the number of engine times exceeds a predetermined engine speed. If the resistor is abnormal due to disconnection, etc., the power generated by the generator is not consumed as thermal energy by the resistor. As a result, the engine frequency becomes excessively high and easily exceeds the predetermined engine speed. End up. Thus, it is not preferable that the number of engine increases excessively from the viewpoint of extending the life of the engine.

  Preferably, the control means can perform control so that the engine rotation speed during execution of the resistance energization control does not exceed the number of engine times immediately before the resistance energization control is performed (immediately before the power supply is stopped). When resistance energization control is performed in this manner, the number of engines (corresponding to the engine rotation speed) is suppressed so as not to be excessive, which is preferable from the viewpoint of extending the life of the engine. The engine speed immediately before the resistance energization control is performed is, for example, an engine speed within 2 seconds or within 1 second before the time when the resistance current control is performed.

  According to the present invention, when the electric power generated by the engine power generator is supplied to the grid interconnection unit, the control means is configured to stop the power supply from the inverter to the grid interconnection unit before the gate block of the inverter output circuit. Or, simultaneously with the gate block, resistance energization control for starting energization of the resistor is performed. As a result, the part of the electric power with the reduced engine load is consumed as thermal energy. For this reason, the engine load is suppressed from greatly fluctuating before and after the power supply to the grid interconnection unit is stopped. For this reason, when stopping the electric power feeding from an inverter to a grid connection part, it is suppressed that an engine load is reduced rapidly, and a possibility that an engine speed may rise rapidly and excessively is suppressed.

  According to the present invention as described above, an engine power generation device that is advantageous for suppressing an abrupt and excessive increase in the engine rotation speed when stopping the power supply to the grid interconnection unit including the commercial power source and the power load. Can be provided.

FIG. 3 is a block diagram related to the cogeneration system according to the first embodiment. It is a block diagram related to an inverter. It is a flowchart related to the power supply stop control at the time of grid connection operation. It is a timing chart which shows the relationship between time, electric power feeding, etc. It is a graph which shows the relationship between the setting rotational speed of engine rotational speed, and electric power. 6 is a timing chart according to the second embodiment and related to power supply stop control. 10 is a timing chart according to the third embodiment and related to power supply stop control.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. As shown in FIG. 1, the cogeneration system includes an engine power generation device 1 that generates power by driving an engine, and a hot water storage system 9 that collects exhaust heat in the engine power generation device 1 and stores it as hot water. As shown in FIG. 1, the engine power generator 1 includes an engine 2, a generator 3 that is rotated by the engine 2 to generate AC power, a resistor 4 that can be energized, an inverter 5, a control unit 6, A remote controller 7 from which a user outputs a user command related to power generation to the control unit 6 and an exhaust heat recovery unit 8 that recovers exhaust heat of the engine 2 are provided. The control unit 6 controls the inverter 5, the engine 2, and the generator 3.

  The engine 2 is provided with a sensor 2s for detecting the engine rotation speed. The engine 2 is connected to a fuel passage 21 that supplies fuel to the combustion chamber of the engine 2 and an intake passage 22 that supplies air to the combustion chamber of the engine 2. A throttle valve 25 controlled by the control unit 6 is provided in the intake passage 22. A fuel valve 26 is provided in the fuel passage 21. Basically, the intake flow rate supplied to the engine 2 is determined by the opening degree of the throttle valve 25, and the fuel supply amount of the fuel passage 21 is determined by the opening degree of the fuel valve 26. The throttle valve 25 and the fuel valve 26 are mainly mechanical elements, and generally have lower responsiveness than electric parts or electronic parts. The fuel for driving the engine 2 may be gaseous fuel, liquid fuel, or powder fuel. Examples of the gaseous fuel include city gas, LP gas, and biogas. The resistor 4 may be installed in the ventilation flow passage of the engine 2 or may be installed in the engine coolant circuit. Thereby, it is easy to release the heat energy generated by the resistor 4.

  As shown in FIG. 1, the exhaust heat recovery unit 8 of the engine power generator 1 stores the exhaust heat of the engine 2 as hot water in a hot water storage tank 90, and an outlet 2 p of a cooling water passage provided in the engine 2. The engine cooling water circuit 80 that returns to the inlet 2i of the engine 2 after being discharged from the engine 2, the heat exchanger 81 provided on the outlet 2p side of the engine cooling passage 2w in the engine cooling water circuit 80, and the heat radiation action A radiator 82, a blower 83 that blows air to the radiator 82 and promotes heat dissipation of the radiator 82, a first pump 84 that circulates engine coolant (engine coolant) in the engine coolant circuit 80, and a control valve And a three-way valve 85.

  The three-way valve 85 has a function of adjusting the amount of water supplied to the radiator 82 and the amount of water not supplied to the radiator 82. When the temperature of the engine cooling water becomes high, the three-way valve 85 is operated, and the amount of water supplied to the radiator 82 is increased in order to increase the heat radiation amount in the radiator 82.

  The hot water storage system 9 includes a hot water storage tank 90, a hot water supply passage 91 for flowing hot water stored in the hot water storage tank 90 to the hot water supply section, a water supply passage 92 for supplying water to the hot water storage tank 90, and engine cooling water in the heat exchanger 81. A heat exchange passage 93 for exchanging heat with the passage 80 and a second pump 94 provided in the heat exchange passage 93 are provided. When the second pump 94 is driven, the water in the hot water storage tank 90 flows through the heat exchange passage 93, is heated by exchanging heat with the heat exchanger 81, and returns to the hot water storage tank 90. In this way, the engine exhaust heat is stored as hot water energy in the hot water storage tank 90 via the heat exchanger 81.

  Here, when the first pump 84 of the engine coolant circuit 80 is driven, the engine coolant flows from the inlet 2i to the cooling passage 2w of the engine 2 and is warmed by receiving heat from the engine 2. The engine coolant warmed by the engine 2 flows from the outlet 2p to the heat exchanger 81, exchanges heat with the water in the heat exchange passage 93 of the hot water storage system 9 to warm the water in the heat exchange passage 93, and then as necessary. Then, it flows into the radiator 82 and dissipates heat, and then the engine cooling water flows from the inlet 2i to the cooling passage 2w of the engine 2. In this way, the exhaust heat of the engine 2 is recovered in the hot water storage tank 90 as hot water.

  FIG. 2 is a block diagram related to the inverter 5 according to the present embodiment. As shown in FIG. 2, the inverter 5 includes a converter 501 (converter) having a rectifier that converts AC power of the generator 3 into DC power, and a DC having a diode and a switching element and converted by the converter 501. An inverter output circuit 504 for converting electric power into AC power of a predetermined frequency, a circuit breaker 505 for cutting off the supply of the output power of the inverter output circuit 504 to the local load 600 (electric power load) and the commercial power source 610, and a cutoff function Circuit breaker 506, system interconnection protection function unit 507 for interrupting and connecting circuit breaker 505, and power output from inverter output circuit 504 is detected by sensor 508a, and power output from inverter output circuit 504 is controlled. An output control function unit 508 for controlling the resistor 4 and a resistor control unit 509 for controlling the resistor 4. The output control function unit 508 and the resistor control unit 509 constitute a control unit.

  The resistor control unit 509 is controlled by a command S1 from the output control function unit 508, and controls a duty value related to a current value to be supplied to the resistor 4, thereby controlling a current value flowing through the resistor 4 per unit time. The resistor control unit 509 is connected between the converter 501 and the inverter output circuit 504, and supplies the DC power from the converter 501 to the resistor 4.

  The grid interconnection protection function unit 507 is an overvoltage relay 507a (over voltage relay) that operates when an overvoltage occurs with respect to the voltage of the commercial power supply as a device for improving the grid interconnection. Over-frequency relay 507b (over frequency relay) that operates when an over-frequency occurs, under-frequency relay 507c (under frequency relay) that operates when the frequency is insufficient with respect to the frequency of the commercial power supply, and operates when reverse power is generated Reverse power relay 507d (reverse power relay), undervoltage relay 507e (under voltage relay) that operates when the peripheral voltage is insufficient with respect to the voltage of the commercial power supply, isolated operation detector 507e (active method), isolated operation detection Unit 507h (passive method) and a DC component detection unit 5 for detecting a DC current component included in the output current of the generator 3 with a current sensor 507i 07g.

  The breaker 506 of the inverter 5 is connected to the on-site load 600 and supplies power to the on-site load 600 to operate the on-site load 600. Here, the on-site load 600 that functions as a power load can be operated by the power supplied from the inverter 5 and the power supplied from the commercial power source 610. Therefore, the local load 600 (electric power load) and the commercial power source 610 constitute the grid interconnection unit 60.

  FIG. 3 shows a flowchart for performing control to stop power supply to the grid interconnection unit 60 when the engine power generator 1 is grid-connected to the grid interconnection unit 60 and supplies power to the grid interconnection unit 60. . As shown in FIG. 3, in starting the power supply stop control for stopping power supply from the inverter 5 of the engine power generator 1 to the on-site load 600 or the commercial power source 610, first, the engine power generator 1 is immediately stopped (stop of the engine 2). It is determined whether an immediate stop condition that needs to be included is satisfied (step S102). In this case, if a serious failure or the like occurs in the cogeneration system including the engine power generator 1, the immediate stop condition is satisfied.

  If the immediate stop condition is satisfied in this way (Yes in step S102), the gate block of the inverter output circuit 504 is performed, and the power supply from the inverter output circuit 504 to the grid interconnection unit 60 side is stopped (step S104). Further, the circuit breaker 505 is disconnected (turned off) (step S106). Thereby, the power supply from the inverter 5 to the local load 600 or the commercial power source 610 is stopped. Here, the gate block means that the switching operation of the switching elements constituting the inverter output circuit 504 is stopped. The power supply from the inverter output circuit 504 to the grid interconnection unit 60 is stopped by the gate block.

  When the engine power generator 1 is immediately stopped, the control unit 6 controls the throttle valve 25 and the fuel valve 26 to cut off the fuel supply to the engine 2 and the ignition cut operation of the engine 2. And the rotational drive of the engine 2 is immediately stopped.

  If the result of determination in step S102 is that the immediate stop condition is not satisfied (No in step S102), it is determined whether or not the system is normally stopped (step S110). If the system is normally stopped (Yes in step S110), the feed power fed from the inverter output circuit 504 to the grid interconnection unit 60 is reduced at a predetermined rate (Pdown [W / sec]) per unit time ( Step S112). Pdown [W / sec] is set to a value that does not cause a problem in the engine 2 and the inverter 5 even if the output of the engine 2 is reduced at a rate of reduction per unit time. Here, if Pdown [W / sec], which is the rate of decrease, is too small, the time until power supply is stopped unnecessarily increases, leading to fuel consumption. On the other hand, if Pdown [W / sec], which is the rate of decrease, is too large, the engine load decreases rapidly, which may cause the engine speed to rapidly increase to high speed or cause an inverter overvoltage. . In consideration of such matters, it is preferable to set Pdown [W / sec], which is a decrease rate.

  It is determined whether or not the output power from the inverter output circuit 504 gradually decreases and is less than Pdown [W / sec] (step S114). If the output power from the inverter output circuit 504 decreases and is less than the threshold value Pstop [W / sec] (Yes in step S114), the inverter output circuit 504 is gate-blocked, and the output from the inverter output circuit 504 is output. Stop (step S116). Further, the circuit breaker 505 is disconnected (turned off) (step S118). Thereby, the power supply from the inverter 5 to the grid interconnection unit 60 is stopped.

  In the case of the above-described normal stop of the system, the control unit 6 causes the engine 2 to perform a cooling operation for a predetermined time, then closes the throttle valve 25 and the fuel valve 26, and further performs an ignition cut operation of the engine 2. Then, the rotational drive of the engine 2 is promptly stopped.

  And although the situation which stops the electric power feeding to the grid connection part 60 is detected, it does not satisfy the immediate stop condition (No in step S102), and if the condition for normally stopping the system is not satisfied (step) In step S110, resistance energization control, which is a feature of the present embodiment, is performed while maintaining the rotational drive of the engine 2, that is, without stopping the drive of the engine 2. Therefore, the process proceeds from step S110 to step S122. That is, although power supply from the inverter 5 to the grid interconnection unit 60 is stopped, it is not necessary to stop the engine 2, and the engine 2 is maintained in a low rotation speed region (for example, idling operation state). An example of such a case is when a grid fault is detected by the grid interconnection protection function unit 507. Specifically, the case where the overvoltage relay 507a, the overfrequency relay 507b, the underfrequency relay 507c, the reverse power relay 507d, the undervoltage relay 507e, the single operation detection unit 507e, the single operation detection unit 507f, etc. are activated.

  Here, in step S122, the rotational speed of the engine 2 at that time is recorded as Nset. This is to save the rotational speed Nset when a system malfunction is detected by the system interconnection protection function unit 507. Next, the duty value of the current flowing through the resistor 4 is set. In this case, the duty value is preferably set in consideration of factors such as the engine speed Nset and the generated power.

  The duty value can be set as a high value (for example, 100%). Then, energization of the resistor 4 with the current defined by the duty value is started (step S124). As a result, the output power supplied from the inverter output circuit 504 is consumed as thermal energy in the resistor 4, and it is avoided that the engine load is rapidly reduced. Here, the duty value is 80, which is substantially equal to the power supplied immediately before the resistance energization control is performed (immediately before the power supply is stopped) (for example, 80% of the power supplied immediately before the resistance energization control is performed (just before the power supply is stopped). It is preferable that the flow rate is set to flow through the resistor 4 within a range of ˜120% and within a range of 90% to 110%. This is because the engine load can be prevented from greatly fluctuating before and after the resistance energization control is performed.

  Thereafter, the gate block of the inverter output circuit 504 is performed, and the power supply from the inverter output circuit 504 to the grid interconnection unit 60 is stopped (step S126). As described above, according to the present embodiment, energization of the resistor 4 is started before the gate block is performed.

  In this case, although the output power of the inverter output circuit 504 is stopped from being fed to the grid interconnection unit 60 side, the resistance energization control is performed. It is preferable that a current is passed through the resistor 4 so that the resistor 4 consumes it as heat energy. In this case, large fluctuations in engine load are suppressed. As a result, the output of the inverter output circuit 504 is stopped from being supplied to the grid interconnection unit 60, but the engine speed is suppressed from increasing rapidly and excessively.

  Of course, the resistor 4 may be energized so that less power than the power just before the resistance energization control is performed is consumed as thermal energy by the resistor 4. In this case, the engine speed slightly increases as compared to immediately before the resistance energization control is performed, but it is preferable to set a duty value that does not cause an abnormal increase in the engine speed or an inverter overvoltage.

  Alternatively, the resistor 4 may be energized so that a larger amount of power than the power just before the resistance energization control is performed is consumed as thermal energy by the resistor 4. In this case, electric power is consumed as thermal energy by resistance energization control, and the engine load increases rapidly. Therefore, the engine rotation speed tends to decrease rapidly, but it is effective when it is desired to decrease the engine rotation speed rapidly. is there. However, it is preferable to set a duty value so that the engine does not stop.

  In the above-described resistance energization control, it is preferable that power is supplied again from the engine power generator 1 to the grid interconnection unit 60 when the grid malfunction that has caused the power feed stop is resolved. Considering this, in the resistance energization control, it is preferable to maintain the engine 2 in a low rotation speed region (for example, idling state). For this reason, it is preferable that the control part 6 controls the opening degree of the throttle valve 25 and the fuel valve 26 so as not to stop the rotational drive of the engine 2.

  Further, after the inverter output circuit 504 is gate-blocked (step S126), it is determined whether the circuit breaker 505 needs to be disconnected (step S128). If it is necessary to disconnect the circuit breaker 505 (Yes in step S128), the circuit breaker 505 is disconnected (step S130), and the connection between the inverter 5 and the grid interconnection unit 60 is disconnected. The connection to the grid interconnection unit 60 is mechanically cut off. Thereafter, the process proceeds to step S134. Even if it is not necessary to disconnect (turn off) the circuit breaker 505 (No in step S128), the process proceeds to step S134. Here, when the independent operation passive of the interconnection protection function occurs, the gate block of the inverter output circuit 504 is implemented (step S126), but the circuit breaker 505 is not disconnected (OFF) (No in step S128). It is preferable.

  In step S134, PWM control is performed, and the duty value of the current supplied to the resistor 4 is decreased with time. As a result, the amount of current flowing through the resistor 4 is linearly decreased with time. Here, as the amount of current flowing through the resistor 4 decreases, the control unit 6 controls the throttle valve 25 and the fuel valve 26 so as to interlock with this, and gradually decreases the engine speed. For this reason, even if the duty value of the current flowing through the resistor 4 is decreased, an excessive increase in the engine speed is suppressed.

  When the resistance energization control is performed as described above (step S134, step S136, step S138), it is determined whether or not the engine speed exceeds the threshold value, that is, Nset + ΔN and is in a high speed state. (Step S136). If the engine speed is not high (No in step S136), the engine speed is good, and it is determined whether the current duty value is less than a threshold value Dend for the duty value (step S138). ). If the current duty value is equal to or greater than the threshold value Dend (No in step S138), the duty value is further decreased (step S134). According to the present embodiment, the control unit 6 controls the throttle valve 25 and the fuel valve 26 so as to interlock with the duty value of the current flowing through the resistor 4 as the time decreases, and the engine speed is increased. Reduce gradually. For this reason, even if the duty value of the current flowing through the resistor 4 is decreased, an excessive increase in the engine speed is suppressed.

  Here, if the duty value becomes less than the threshold value Dend (Yes in step S138), the duty value is set to zero and the current supply to the resistor 4 is stopped (step S140). When the energization of the resistor 4 is stopped, the heat energy consumed by the resistor 4 is lost, but there is no problem because the engine rotational speed is reduced accordingly.

  As an example of decreasing the duty value, the duty value of the current flowing through the resistor 4 is decreased by a predetermined percentage (10%) every predetermined time (for example, 0.5 seconds), and the current flowing through the resistor 4 is gradually decreased. When the duty value becomes smaller than 10%, the energization of the resistor 4 can be stopped. Thereby, the power supply stop operation of the inverter 5 is completed. The duty value may be decreased by 5% every 0.5 seconds or may be decreased by 20%.

  When the engine speed exceeds Nset + ΔN and becomes a high rotation state while the duty value is being decreased (Yes in step S136), the resistor 4 or the wiring connected to the resistor 4 is abnormal ( The failure is determined (step S144), and the abnormality is notified to the control unit 6 (step S146). In addition, since the probability of abnormality of the resistor 4 is extremely low, there is virtually no adverse effect. Thereafter, the energization of the resistor 4 is stopped (step S140). Here, when the engine rotation speed exceeds Nset + ΔN and becomes a high rotation state while the duty value is being lowered, this corresponds to a case where no electric power is consumed as thermal energy by the resistor 4. It is presumed that there is a “resistor abnormality” such as disconnection.

  In addition, according to such this embodiment, at the time of the start-up operation before the engine power generator 1 starts the rated operation of the power generation operation, the control means checks whether there is an abnormality such as disconnection of the resistor 4 It is preferable to carry out the operation. In the inspection operation of the resistor 4, the generator 2 generates power while rotating the engine 2 at a constant rotation speed (determination value) in the low rotation speed region. In this case, the resistor 4 is energized with a current having a predetermined duty value based on the power generated by the generator 3. Next, the output circuit 504 is gate-blocked. In this case, if there is an abnormality such as disconnection of the resistor 4, no current is passed through the resistor 4, and as a result, no electric power is consumed as thermal energy by the resistor 4. For this reason, the engine rotation speed becomes higher than the constant rotation speed (determination value). Thereby, an abnormality such as disconnection of the resistor 4 is determined. If there is no abnormality such as disconnection of the resistor 4, that is, if the resistor 4 is normal, the electric power is consumed as thermal energy in the resistor 4, so the engine rotation speed is a constant rotation speed (determination value). Lower than.

  FIG. 4 shows an example of a timing chart of the above control. FIG. 4A shows the state of the feed power that is fed from the inverter 5 to the grid interconnection unit 60. FIG. 4B shows a state of current flowing through the resistor 4. FIG. 4C shows the state of the engine rotation speed. FIG. 4D shows the presence or absence of a gate block in the inverter output circuit 504. FIG. 4 (E) shows the circuit breaker 505 being disconnected and connected. In FIG. 5, the horizontal axis indicates time. As time advances from t1, t2, t3, t4.

  As shown in FIG. 4A, at time t1, power is supplied from the inverter 5 to the grid interconnection unit 60 (rated operation 100%). In the rated operation of the engine power generator 1, the gate block of the inverter output circuit 504 is not performed, and the engine rotation speed is maintained at Nhigh. At time t <b> 3, the grid connection protection function unit 507 is activated due to a problem related to grid connection and the like, and a command for stopping power supply from the inverter 5 to the grid connection unit 60 is output. Here, at time t2 and time t1 prior to time t3 when power supply to the grid interconnection unit 60 is stopped, the circuit breaker 505 is electrically connected, and the engine rotation speed is maintained at Nhigh.

  At time t3, as shown in FIG. 4D, the gate block of the inverter output circuit 504 is performed, and the power supply from the inverter 5 to the grid interconnection unit 60 is stopped. In this way, current supply to the resistor 4 has already started from time t2 before time t3 when power supply to the grid interconnection unit 60 is stopped by the gate block of the inverter output circuit 504. As a result, the power (DC power) output from the converter 501 is passed through the resistor 4 and is consumed as thermal energy in the resistor 4.

  Here, when the power supply to the grid interconnection unit 60 is stopped, the resistor 4 is energized. From time t2 to time t3, as shown in FIG. 4B, the duty of the current energized to the resistor 4 is as shown in FIG. It is preferable to gradually increase the value. As a result, the rate at which the electric power generated by the generator 3 is consumed as thermal energy by the resistor 4 gradually increases. If the rate at which the electric power generated by the generator 3 is consumed as thermal energy by the resistor 4 increases rapidly, the engine load increases rapidly, and the engine speed may decrease rapidly. In some cases, the engine 2 may stop due to engine stall.

  Therefore, according to the present embodiment, in order to suppress a sudden increase in engine load, the resistor function control unit 509 supplies power to the grid interconnection unit 60 through a gate block as shown in FIG. The resistor function control unit 509 gradually increases the duty value of the current supplied to the resistor 4 linearly with a predetermined gradient from time t2 to time t3, starting from time t2 prior to stopping the current. . Here, when gradually increasing the duty value, the rate of change (inclination) per unit time of the duty value is α1. It should be noted that the duty value may be increased stepwise instead of linearly from time t2 to time t3.

  Note that the time t2 at which the resistance energization control is started can be, for example, within 3 seconds, within 2 seconds, within 1 second, or within 500 milliseconds with respect to the time t3 when the gate block is performed. . However, it is not limited to these. This is appropriately set according to the type of the engine 2, the control responsiveness of the engine 2, the engine rotational speed, the type of cause for stopping the power supply to the grid interconnection unit 6, the type of the cogeneration system and the engine power generator 1, and the like.

  When the time t3 at which the duty value is the highest elapses, the resistor function control unit 509 gradually decreases the duty value of the current supplied to the resistor 4. When the duty value is decreased with time, the rate of change per unit time (down slope) of the duty value is α2. The change rate α2 per unit time is smaller than the change rate α1 per unit time (α2 <α1). This is because, in the resistance energization control described above, the duty value of the current energized to the resistor 4 is gradually decreased with time, and the heat energy consumed by the resistor 4 is gradually decreased. Further, although the control unit 6 controls the throttle valve 25 and the fuel valve 26 so that the rotational speed of the engine 2 gradually decreases, the throttle valve 25 and the fuel valve 26 are mechanical parts. Responsiveness is slow compared. Therefore, this is to cope with this slow response.

  As described above, after the time t3, the gate block of the inverter output circuit 504 is performed, and the power supply from the inverter 5 to the grid interconnection unit 60 is stopped. At the time t3 when the power supply to the grid interconnection unit 60 is stopped, the engine load may change suddenly. Therefore, the duty value of the current flowing to the resistor 4 is increased, and in particular, may be the highest value (100%). preferable. As a result, even immediately after the power supply from the inverter 5 to the grid interconnection unit 60 is stopped, the engine load is suppressed from being rapidly reduced, and as a result, the engine speed can be rapidly and excessively increased. It is suppressed. Thereafter, at time t4 after time t3, the circuit breaker 505 is disconnected and turned off, and the inverter output circuit 504 and the grid interconnection unit 60 are mechanically disconnected. In this case, the engine rotation speed is maintained in a low rotation speed state (for example, an idling state). That is, at time t3 when the gate block is generated, the duty value for energizing the resistor 4 is increased. When the maximum value of the duty value is displayed relative to 100, it can be in the range of 80-100.

  A characteristic line CX indicated by a broken line in FIG. 4C corresponds to a comparative example, and shows the state of the engine speed when the resistor 4 is not energized. When the resistor 4 is not energized, surplus power is not consumed as thermal energy in the resistor 4. Therefore, immediately after time t3 when power supply from the inverter 5 to the grid interconnection unit 60 is stopped, that is, immediately after the gate block, the engine load is drastically reduced by the gate block. In addition, the engine speed tends to increase rapidly and excessively. In order to prevent this, the control unit 6 controls the throttle valve 25 and the fuel valve 26, which are mechanical parts, to reduce the degree of opening, and conversely, the engine speed tends to decrease rapidly.

  In the case where the resistor 4 is not energized in this way, when the opening degree of the throttle valve 25 and the fuel valve 26 is controlled, when the power supply from the inverter 5 to the grid interconnection unit 60 is stopped, the characteristic line CX As shown in the graph, the engine speed may increase rapidly due to overshooting, or may subsequently decrease rapidly due to undershooting, resulting in large fluctuations in engine rotation speed and improving the durability of the engine 2. It is not preferable from the aspect. When the resistor 4 is not energized as described above, the engine rotational speed is basically decreased by the control of the throttle valve 25 and the fuel valve 26, so that there is a problem that the fluctuation of the engine rotational speed becomes large. Furthermore, there is a problem that it takes a long time until the engine speed converges to Nlow, which is Tlong.

  In this regard, before the gate block of the inverter output circuit 504 is implemented as in this embodiment, the resistor 4 is energized to consume power as thermal energy. Thereby, it is possible to suppress the engine load from being rapidly reduced due to the gate block. As a result, after the gate block is implemented, the engine speed is prevented from increasing rapidly and excessively. As a result, the engine speed is prevented from rapidly and excessively decreasing thereafter, and as shown by the solid line in FIG. 5C, large fluctuations in the engine speed are suppressed.

  Note that, according to the present embodiment, in order to rotate the engine 2 in an efficient state, as shown in FIG. 5, the set rotational speed of the engine rotational speed is set in advance according to the power supply power, and the power It is set by the control unit 6 according to the amount. As a result of the gate block of the inverter output circuit 504, when the amount of power to be fed to the grid interconnection unit 60 becomes 0 kW (0% with respect to the amount of power of the rated operation), the target speed of the set engine speed of the engine speed is It is lowered from Nhigh to Nlow by the control unit 6. If resistance energization control that consumes electric power as thermal energy of the resistor 4 is performed before the gate block of the inverter output circuit 504 is implemented as in the present embodiment, the engine rotation speed is converged from Nhigh to Nlow. Is shortened.

  As described above, according to the present embodiment, when power is supplied from the inverter 5 to the grid interconnection unit 60, the inverter output circuit 504 of the inverter 5 is stopped when power supply from the inverter 5 to the grid interconnection unit 60 is stopped. The power supply from the inverter 5 to the grid interconnection unit 60 is stopped, and resistance energization control for energizing the resistor 4 is performed. In this resistance energization control, energization to the resistor 4 is started with a current value based on the duty value set by the resistor control function unit 509, and after the start, the duty value is gradually decreased to obtain a current based on the duty value. Decrease the value gradually.

  In particular, according to the present embodiment, the resistance energization control for energizing the resistor 4 before the gate block of the inverter output circuit 504 is performed, that is, immediately before the power supply from the inverter 5 to the grid interconnection unit 60 is stopped. The resistor 4 is energized with a current value based on the set duty value, and surplus power is consumed as heat energy in the resistor 4. As a result, the engine rotation speed can be suppressed immediately before the gate block is implemented, that is, immediately before the power supply to the grid interconnection unit 60 is stopped. For this reason, it is possible to effectively suppress the engine rotation speed from rapidly and excessively increasing with the gate block.

  Furthermore, according to the present embodiment, as shown in FIG. 4C, the engine rotational speed during the above-described resistance energization control is controlled so as not to exceed the engine number Nhigh immediately before the resistance energization control is performed. Is done. As a result, the engine speed is prevented from increasing rapidly and excessively, and the durability of the engine 2 is ensured over a long period of time. In the present embodiment, for the portion indicated as the change rate α2, the duty value may be reduced stepwise or exponentially.

  The reason why the current can flow through the resistor 4 at a timing before the gate block is disconnected (off) is as follows. In other words, the grid connection provision JEAC9701-2006 (edited by the NEC Corporation) presents the detection time when the protective relay is activated, and within this time, the gate block and disconnection (off) from the protective relay operation are presented. It is common to complete. In the grid connection rules, it is listed as a condition that the system is not disconnected from instantaneous grid fluctuations. The reason for this is that if there is an instantaneous fluctuation of the system power supply that can occur on a daily basis, the system side power supply frequently bears all the on-site load power covered by the generator if the disconnection and power supply are stopped each time. This is to prevent the system power supply from becoming unstable.

  In recent years, the installation of distributed generators such as cogeneration has rapidly increased as a measure against global warming, and it has become even more important not to make such a system power supply unstable. Therefore, as a countermeasure against instantaneous system power fluctuation, even if one of the judgment conditions (voltage or frequency becomes an abnormal value) is established in the protective relay, if the judgment condition does not continue for a certain period of time, the system malfunction In general, it is not determined that the gate block and the disconnection are not performed. In this embodiment, a certain time (= time lag) from when one of the determination conditions for a system failure is established to when it is determined that the system is abnormal is used effectively.

(Embodiment 2)
FIG. 6 shows a second embodiment. Since this embodiment basically has the same configuration and the same function and effect as those of the first embodiment, FIGS. 1 to 4 can be applied mutatis mutandis. As shown in FIG. 6, also in the present embodiment, the gate block of the inverter output circuit 504 is implemented to stop the power supply from the inverter 5 to the grid interconnection unit 60 (time t3). The surplus power is energized and consumed by the resistor 4 as heat energy. However, the duty value of the current supplied to the resistor 4 is raised at time t2 before the time t3 when the gate block is performed after the system failure is detected. After the time t3 when the gate block is performed, as in the first embodiment, the duty value of the current flowing through the resistor 4 is gradually decreased with time.

(Embodiment 3)
FIG. 7 shows a third embodiment. Since this embodiment basically has the same configuration and the same function and effect as those of the first embodiment, FIGS. 1 to 4 can be applied mutatis mutandis. Also in the present embodiment, by performing the gate block of the inverter output circuit 504, when the power supply from the inverter 5 to the grid interconnection unit 60 is stopped (time t3), the resistor 4 is energized and surplus power is supplied. It is consumed by the resistor 4 as heat energy. However, after the grid fault is detected by the grid interconnection protection function unit 507, the resistor 4 is energized to stop the power supply to the grid interconnection unit 60, but at the execution time t3 when the gate block is started, The duty value of the current flowing through the resistor 4 is increased. After time t3, as in the first embodiment, the duty value of the current supplied to the resistor 4 is gradually decreased with time.

(Other embodiments)
According to the above-described embodiment, in the resistance energization control, the amount of current to be supplied to the resistor 4 is controlled by the duty value. However, the present invention is not limited to this, and the current amount itself is controlled while energizing the current amount. Anyway. The current passed through the resistor 4 may be direct current or alternating current. As shown in FIG. 4, the duty value is set to be the highest at time t3, but the present invention is not limited to this. For example, at time t1 or time t2, the duty value corresponding to the amount of power supplied to the resistor 4 can be made highest (100%). In addition, the present invention is not limited to the embodiment described above and shown in the drawings, and can be implemented with appropriate modifications without departing from the scope of the invention. Structures and functions specific to one embodiment can be applied to other embodiments.

  1 is an engine generator, 2 is an engine, 3 is a generator, 4 is a resistor, 5 is an inverter, 6 is a control unit, 7 is a remote control, 8 is an exhaust heat recovery unit, 81 is a heat exchanger, and 501 is a converter 504 is an inverter output circuit, 505 is a circuit breaker, 507 is a grid connection protection function unit, 508 is an output control function unit, 509 is a resistor function control unit, 60 is a grid connection unit, and 600 is a local load (power load). ), 610 indicates a commercial power source.

Claims (4)

An engine power generator that feeds power to a grid interconnection unit composed of a commercial power source and a power load,
An engine driven by fuel combustion,
A generator that is rotated by the engine to generate AC power;
A resistor capable of energizing a current based on the power generated by the generator;
An inverter having a converter that converts AC power of the generator into DC power and an inverter output circuit that converts the DC power into AC power of a predetermined frequency and supplies power to the grid interconnection unit;
Controlling the energization amount per unit time for energizing the resistor, and performing the gate block of the inverter output circuit of the inverter to stop the power feeding to the grid interconnection unit, the gate of the inverter output circuit An engine power generator comprising: control means for performing resistance energization control for starting energization of the resistor before the block or simultaneously with the gate block.   2. The engine power generator according to claim 1, wherein, in the resistance energization control, the control unit starts energization of the resistor and, after the start, starts decreasing the value of the current energized to the resistor. 3. The engine power generator according to claim 1, wherein the control unit determines that the resistor is abnormal when the number of engine times exceeds a predetermined engine rotation speed when performing the resistance energization control. 4. . 4. The control unit according to claim 1, wherein the control means is configured to prevent the engine rotation speed during execution of the resistance energization control from exceeding an engine frequency immediately before the resistance energization control is performed. An engine power generator that controls energization to a battery.

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