JP4348630B2 - Cogeneration equipment - Google Patents

Description

  The present invention relates to a cogeneration apparatus that generates electric power and thermal energy, and more particularly to a technique for preventing reverse power flow to a commercial power system when generated power is connected to the commercial power system.

  In recent years, development of a cogeneration apparatus that performs power generation using a fuel cell, a gas engine, and the like and simultaneously supplies hot water using exhaust heat generated by the power generation has been actively promoted. In such a cogeneration apparatus, when the power supplied to the private power load is insufficient, a configuration is adopted in which the shortage is compensated by purchasing power from a commercial power system linked to the system.

  In general, it is difficult for the cogeneration apparatus to change the generated power suddenly due to the characteristics of the power generation unit. Therefore, when the power consumption of the private power load is drastically reduced, the decrease in the power output cannot catch up, resulting in a reverse power flow in which surplus power flows into the commercial power system. In the case of a small-capacity cogeneration device, so-called power sale that reversely flows surplus power to the commercial power system is often not economical because of the balance between the power sale price and fuel costs for power generation. Therefore, it is often connected to a commercial power system under the condition that even if surplus power is generated, no reverse power flow is made to the commercial power system in accordance with the power system linkage technical requirement guidelines established by the Agency for Natural Resources and Energy, Ministry of International Trade and Industry.

  As a countermeasure against reverse power flow in a small-capacity cogeneration system, there is a method of preventing the generation of surplus power by providing a plurality of dummy power loads, and when surplus power is likely to be generated, they are consumed. It is taken. Since the energy generated by the dummy power load is normally used for heating hot water, not all of it is wasted. However, it is not preferable to consume a large amount of power in the dummy power load from the viewpoint of the device's purpose of performing both the energy efficiency of the entire device and the balance between power supply and hot water supply.

Speaking of power efficiency, adjustment of power consumption by switching dummy power load is gradual and the resolution of control is rough, so it is necessary to allow extra power to be consumed by dummy power load with a margin, reducing energy efficiency . Increasing the number of dummy power loads to increase the resolution increases the number of load switching power switches and the control circuit, resulting in an increase in equipment cost and an increase in failure probability. In addition, switching for preventing reverse power flow requires a high-speed response, and it is also necessary to reduce noise generated in the power supply line when switching loads.
JP 2000-320401 A JP 2004-297905 A

  The present invention has been made to solve such problems of the prior art, and its problem is to control the timing for consuming surplus power in the cogeneration apparatus to the dummy power load and the energization time with high accuracy. The purpose is to prevent reverse power flow.

The invention according to claim 1 for solving the above-mentioned problem is a cogeneration apparatus that supplies generated power to a private power load (6) in cooperation with a commercial power system (5), A dummy power load (11) connected in parallel to the private power load and a control means for ON / OFF control of power supply to the dummy power load are provided, and the control means adds and subtracts clock pulses to perform addition / subtraction time measurement. A power measuring device (14) for measuring an addition / subtraction time timer and a reverse flow power (P) flowing to the commercial power system side is provided, and the measurement power (P) of the power measuring device is a first predetermined power ( The addition count is less than the first predetermined power, and the subtraction count to the minimum value zero is less than the second predetermined power (P2) smaller than the first predetermined power. Na In such a case, the counter is reset to zero, and for the dummy power load, the power is added for the second predetermined time (T2) from the time when the time measured by the addition / subtraction time timer exceeds the first predetermined time (T1). An average value or measured power (P) of measured power (P) from the time when the time measured by the addition / subtraction time timer finally leaves zero until the first predetermined time (T1) is reached. An average value of the difference power between P) and the first predetermined power (P1) is calculated, and the second predetermined time T2 is determined in proportion to the average value .

The determination that the reverse power flow has occurred is generally made based on the fact that the reverse power flow over a certain amount of power has continued for a certain time. According to the cogeneration apparatus of the present invention, the time when the reverse flow power exceeds the first predetermined power is counted as a time obtained by subtracting the non-exceeded period, and if the measured time exceeds the first predetermined time, the dummy power load In addition, power is supplied for the second predetermined time to increase power consumption. Accordingly, since the reverse power flow is reduced by the power consumption of the dummy power load, it is possible to avoid the situation where it is determined that the reverse power flow occurs. Further, since power supply to the dummy power load is continued for the second predetermined time, frequent ON / OFF operations of power supply to the dummy power load are avoided. Then, during such an ON / OFF operation period, it is possible to return to a state in which no reverse power flow occurs even if the dummy power load does not consume power due to an increase in power consumption of the private power load or a decrease in generated power.
On the other hand, the average value of the measured power (P) or the difference power between the measured power (P) and the first predetermined power (P1) until the first predetermined time is reached is reverse. It means that the value of tidal power is large. Therefore, it is possible to effectively avoid a situation where it is determined that the reverse power flow occurs when the power supply time to the dummy power load is increased in proportion to the average value.

  The invention according to claim 2 is the cogeneration apparatus according to claim 1, wherein the time of the second predetermined time (T2) is the time of the addition / subtraction time timer after the start of power supply to the dummy power load. It is characterized by starting from a point of time less than the first predetermined time (T1).

  If the power consumption rating of the dummy power load is set to a large value, the reverse power flow disappears simultaneously with the start of power supply to the dummy power load. However, a situation in which reverse power flow does not sufficiently decrease due to some abnormality occurring, delay in starting power supply to the dummy power load, or 100% of the supplied power being consumed is not generated. Not necessarily. In consideration of such a case, it is more effective to prevent the reverse power flow when the timing of the second predetermined time is started from the time when the time of the addition / subtraction time timer falls below the first predetermined time.

  The invention according to claim 3 is the cogeneration apparatus according to claim 1 or 2, wherein the control means has a third predetermined time (T3) in which the time measured by the addition / subtraction time timer is longer than the first predetermined time. When it exceeds, the power generation of the cogeneration system is stopped, or disconnection from the commercial power system is performed.

  According to such a configuration, even if the reverse power flow exceeding the first predetermined power continues due to some abnormality even after the power supply to the dummy power load is started, the time measured by the addition / subtraction time timer reaches the third predetermined time. At this point, the power generation of the cogeneration device is stopped or the commercial power system is disconnected. Therefore, it is possible to avoid the situation where it is finally determined that the reverse power flow occurs.

  According to a fourth aspect of the present invention, in the cogeneration apparatus according to any one of the first to third aspects, the power consumption of the dummy power load is greater than or equal to the rated generated power of the cogeneration apparatus.

  If the power consumption of the dummy power load is greater than or equal to the rated generated power of the cogeneration device, the dummy power load can consume all of the generated power, and therefore the reverse power flow can be reliably reduced to zero or less.

Further, the invention according to claim 5 is the cogeneration apparatus according to claim 1 or 2, wherein the dummy power load is connected in parallel with a plurality of pipe heaters having substantially the same rating when the generated power is a single-phase alternating current. The pipe heaters are mounted symmetrically about the pipe (8a) through which the heat recovery water for recovering the exhaust heat generated in the power generation process passes.

  Thus, if the energy generated by the dummy power load is used for heating the heat recovery water, the energy efficiency of the entire apparatus can be improved. Further, if the divided pipe heaters are connected in parallel, even if a part of them is disconnected, the remaining heater can consume electric power. Moreover, if the divided | segmented piping heater is attached to the circumference of piping symmetrically, piping can be heated uniformly.

The invention according to claim 6 is the cogeneration apparatus according to claim 1 or 2, wherein the control means performs an operation of supplying and stopping power to the dummy power load using a power semiconductor switch. And
Thus, if the power semiconductor switch is used, not only a high-speed ON / OFF operation can be performed, but also the reliability of the apparatus can be enhanced with respect to a frequent ON / OFF operation.

According to a seventh aspect of the present invention, in the cogeneration apparatus according to the sixth aspect , the control means starts supplying power to the dummy power load at a timing of zero crossing when the voltage applied to the power semiconductor switch becomes zero. The supply stop is also performed at the zero cross timing after the supply stop condition is satisfied.

  If the ON / OFF operation at the timing of zero crossing is performed in this way, the current waveform flowing through the dummy power load becomes a sine wave, thereby reducing the influence of harmonics on the commercial power system caused by the ON / OFF operation. be able to.

  Hereinafter, an embodiment of a cogeneration apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the cogeneration apparatus 1. In the present embodiment, a type using a fuel cell for power generation as a cogeneration device will be described as an example.

  In the cogeneration apparatus 1 of FIG. 1 that uses a fuel cell for power generation, the reformer 2, the fuel cell 3, and the inverter 4 constitute a power generation unit. A raw material gas such as natural gas is supplied to the reformer 2 and heated in a steam atmosphere to be reformed into a hydrogen-rich reformed gas. The generated reformed gas is supplied to the fuel cell 3. In the fuel cell 3, the reformed gas and an oxidizing gas such as air supplied from the outside cause an electrochemical reaction to generate DC power. The generated DC power is sent to the inverter 4 and converted into single-phase or three-phase AC power connected to the commercial power system 5. Then, it is supplied to the private power load 6. The reason why the output line of the inverter 4 is connected to the commercial power system 5 is to supplement the shortage of the generated power with power purchase.

  The cogeneration apparatus 1 performs hot water supply using exhaust heat generated in the power generation process at the same time as generating power. The exhaust heat gas generated in the power generation process in the fuel cell 3 and the exhaust heat gas generated in the reformer 2 are guided to the heat exchanger 7. The exhaust heat gas exchanges heat with circulating water passing through the circulation path 8 in the heat exchanger 7 to change cold water into hot water. The circulating water is taken out from the bottom of the hot water tank 10 by the circulation pump 9, is warmed while passing through the circulation path 8 passing through the heat exchanger 7, and returns to the hot water tank 10. Hot water collected in the upper part of the hot water tank 10 is supplied to a hot water supply load for heating or the like. The water reduced by the hot water supply is replenished with city water from the outside.

  As described in the “Background Art” section, there are many small cogeneration apparatuses that do not perform reverse power flow that causes surplus power to flow from the cogeneration apparatus to the commercial power system. It is assumed that the cogeneration apparatus 1 of the present embodiment also imposes a condition that reverse power flow is not permitted. However, it is assumed that the reverse power flow is not allowed instantaneously, and the reverse power flow in which the reverse power flow exceeding the predetermined power continues for a predetermined time is not allowed. For example, it is assumed that the condition that the reverse flow exceeding 0.5% of the rated generated power of the cogeneration apparatus 1 is not continued for 0.5 seconds or more is imposed. The present invention is effective when applied to a cogeneration apparatus in which a constraint condition of such a definition (hereinafter referred to as a power reverse flow determination condition when this definition is used for determination) is imposed. It is.

  The cogeneration device 1 is controlled by a control device (not shown) so as to generate slightly less power than the power consumed by the private power load 6 so as not to cause reverse power flow. If the power consumption of the private power load 6 rapidly decreases during such power control, the generated power exceeds the power consumption. At that time, the reverse power flow can be prevented if the generated power can be reduced rapidly accordingly. However, in the case of power generation using the fuel cell 3, since the responsiveness of the reformed gas generation capability in the reformer 2 and the responsiveness of power generation in the fuel cell 3 are not good, the generated power can be changed abruptly. Have difficulty.

  In the cogeneration apparatus 1, the electric heater 11 is provided as a dummy power load that consumes surplus power in such a case. A pipe heater is used as the electric heater 11 and is attached around the pipe of the hot water circulation path 8 returning to the hot water tank 10. Thereby, surplus electric power is changed into heat energy and used effectively for heating of hot water.

  The electric heater 11 is connected to the private power load 6 in parallel. The electric heater 11 is turned ON / OFF by a power open / close switch 12, and its open / close control is performed by a reverse power flow prevention control device 13. A power measuring instrument 14 for measuring the reverse power flowing to the commercial power system 5 is attached to the connection between the cogeneration apparatus 1 and the commercial power system 5, and the measured value is input to the reverse power prevention control device 13. Is done. In the case of this embodiment, the control means described in the claims comprises the reverse power flow prevention control device 13, the power meter 14, and the power open / close switch 12.

  The reverse power flow prevention control device 13 includes a control circuit 13a and a clock pulse generation circuit 13b. The control circuit 13a is mainly composed of a microcomputer, and includes a CPU, a RAM, a ROM, a bus line connecting them, an I / O interface, a power supply device, and the like, which are not shown. The control circuit 13a has a timer configured by software that counts the clock pulses generated by the clock pulse generation circuit 13b and counts the clock pulses. The measured value of the power meter 14 is input to the control circuit 13a.

  Next, the operation of the reverse power flow prevention control device 13 for preventing the reverse power flow with such a configuration will be described with reference to FIGS. FIG. 2 is a diagram for explaining the concept of control, and FIGS. 3 and 3 are control flows executed by the control circuit 13a in order to execute the concept.

  The software timer provided in the control circuit 13a for performing the above-described addition / subtraction time measurement is called an addition / subtraction timer, and the time measurement is represented by UDT. In the control circuit 13a, another software timer for performing only addition time counting is provided. The timer is called an addition timer, and the addition time is represented by UT. These two timers are reset when the control circuit 13a is powered on. Moreover, the value of the measured power measured by the power meter 14 is represented by P, and the value of P is positive for the reverse power flow flowing from the cogeneration device 1 toward the commercial power system 5.

  The control flow in FIG. 3 starts executing as an interrupt process each time a clock pulse is input from the clock pulse generation circuit 13b. When the clock pulse is input, the value of the measured power (reverse power flow) P measured by the power meter 14 in the first step S1 is read. In the subsequent step S2, the read reverse power flow P is compared with the first predetermined power P1.

  Hereinafter, description will be given with reference to FIG. (1) of FIG. 2 exemplifies the change of the reverse flow power P with a curve on the vertical axis, the reverse flow power P measured by the power meter 14 on the vertical axis, the time t on the horizontal axis. The first predetermined power P1 is set to a considerably high value, and in this embodiment, when the value of the reverse flow power P exceeds the first predetermined power P1, the addition timer is added to the addition time. If it does not exceed, subtract time is made.

  Therefore, when the value of the reverse power flow P exceeds the first predetermined power P1 in step S2, the process proceeds to step S3, and the clock pulse period Δt is added to the addition / subtraction time UDT of the addition / subtraction timer. Move on. When it does not exceed, addition is not performed, and the process proceeds to step S12 in FIG. Therefore, when the reverse flow power P changes as illustrated in (1) of FIG. 2, as shown in (3) of FIG. 2, between the time t1 to t2 and t3 to t4, the adjustment time of the adjustment timer UDT goes up.

  As will be described later, when the value of the reverse power flow P does not exceed the first predetermined power P1, the addition / subtraction timer performs subtraction timing (however, it is not negative). Accordingly, the addition / subtraction time UDT held by the addition / subtraction timer is deducted from the time when the reverse flow power P has exceeded the first predetermined power P1 after the time has started from zero in the forward direction. Represents the time spent.

  Therefore, a large value of the addition / subtraction time UDT indicates that the period during which the reverse power flow P is high has continued for a long time, which increases the risk of occurrence of the situation where the power reverse flow determination condition described above is satisfied. Means that That is, it can be said that the value of the addition / subtraction time UDT represents the risk of occurrence of a situation where the power reverse power flow determination condition is satisfied.

  In the present embodiment, when this addition / subtraction time UDT exceeds a third predetermined time T3, which is a large value, it is determined that there is an imminent risk that a situation in which the reverse power flow determination condition is satisfied is generated. Or to disconnect the connection with the commercial power system 5.

  For this determination, in step S4, the addition / subtraction time UDT of the addition / subtraction timer is compared with a third predetermined time T3. If the addition / subtraction time UDT exceeds the third predetermined time T3, power generation is stopped in step S5, or disconnection from the commercial power system 5 is performed and the power reverse flow determination condition is satisfied. Avoid being satisfied. Power generation can be stopped instantaneously by stopping the switching operation of the inverter 4. Disconnection from the commercial power system 5 can be performed instantaneously by operating a circuit breaker or an electromagnetic switch (not shown).

  After the power generation is stopped or disconnected so as to avoid the situation where the power reverse flow determination condition is satisfied, the addition / subtraction time UDT is reset to zero in step S6. In the subsequent step S7, the addition time UT of the aforementioned addition timer, whose role will be described later, is also reset to zero.

  When it is determined in step S4 that the addition / subtraction time UDT does not exceed the third predetermined time T3, the process proceeds to step S8. In step S8, the value of the addition / subtraction time UDT is compared with the first predetermined time T1. The first predetermined time T1 is shorter than the above-mentioned third predetermined time T3 as shown in (3) of FIG. Although the situation is not so imminent that power generation must be stopped or disconnected, there is an increasing risk of occurrence of a situation that satisfies the conditions for judging the reverse power flow, so it is necessary to take precautionary measures. is there.

  Therefore, when the addition / subtraction time UDT exceeds the first predetermined time T1, power is supplied to the electric heater 11 which is a dummy power load to increase power consumption, thereby eliminating the state of reverse power flow. . In step S9, it is checked whether the electric heater 11 is energized. If it is not energized, power supply is started in step S10, and the addition time UT of the aforementioned addition timer is reset to zero in step S11 and the process ends. The resetting to zero is preparation for measuring the energization time of the electric heater 11 from the subsequent clock pulse by adding time.

  When power supply to the electric heater 11 is started in step S10, the reverse power flow P immediately becomes a negative value and the reverse power flow is eliminated. This state is shown before and after time t4 in FIG. The larger the power consumption of the electric heater 11, the better. Preferably, the power generation power is rated or higher. This is because the electric heater 11 consumes all of the generated power, and a reverse power flow cannot occur.

  If the electric heater 11 is being energized in step S9, the process proceeds to step S11, where the addition time UT is reset to zero and the process ends. The reason for setting the addition timing time UT to zero even during energization is to allow the addition timer to count the energization time of the electric heater 11 after the addition / subtraction time UDT falls below the first predetermined time T1. The energization is performed only for the second predetermined time T2. However, the time measurement of the second predetermined time T2 is started after the addition / subtraction time UDT is less than the first predetermined time T1, rather than starting simultaneously with the start of energization. This is because it works in the safe direction in the case of delay in energization start of the electric heater 11, power consumption abnormality, or the like.

  If the addition / subtraction time UDT does not exceed the first predetermined time T1 in step S8, the process ends without doing anything. This is because the reverse flow power P exceeds the first predetermined power P1, but the addition / subtraction time UDT has not yet reached the first predetermined time T1, and the reverse flow does not exceed the first predetermined time T1. This is because energization for prevention is not started. This state corresponds to, for example, the period from time t1 to t2 and the period from time t3 to t4 in FIG.

If the value of the reverse flow power P does not exceed the first predetermined power P1 in step S2, the process proceeds to step S12 in FIG. In step S12, the value of the reverse flow power P is compared with the second predetermined power P2. The value of the second predetermined power P2 is a value determined so as to reset the value of the addition / subtraction time UDT to zero when the value of the reverse flow power P is less than that value. The second predetermined power P2 may be a negative value or zero. In short, if the value of the reverse power flow P is less than that value, it is determined to be a value at which it is expected that a situation where the above-described power reverse flow determination condition is satisfied will not occur at an early stage. Therefore, when the reverse flow power P is less than the value of the second predetermined power P2, the value of the addition / subtraction time UDT is reset to zero in step S14. Then, the process proceeds to step S17. If exceeded, the process proceeds to step S14 without resetting.

  In step S14, the clock pulse period Δt is subtracted from the addition / subtraction time UDT. In subsequent step S15, it is checked whether the UDT value after subtraction is negative or not. If negative, the UDT value is reset to zero in step S16 and the process proceeds to step S17. If not negative, the process proceeds to step S17.

  In step S17, it is checked whether the electric heater 11 is energized. If it is not energized, the process ends. This is because the reverse power flow P does not exceed the first predetermined power P1 and is not energized.

  If power is being supplied in step S17, the process proceeds to step S18. Step S18 is executed when the reverse flow power P does not exceed the first predetermined power P1 and the electric heater 11 is energized. Such a state occurs after the addition / subtraction time UDT of the addition / subtraction timer exceeds the first predetermined time T1 and the energization is started in step S9 as described above. In this embodiment, when energization is started, the reverse flow power P becomes a negative value, and a reverse flow cannot occur. At that time, if the energization is stopped immediately, the reverse power flow power P again exceeds the first predetermined power P1. Then, hunting in which ON / OFF of the electric heater 11 is repeated at short time intervals may occur. Accordingly, in the present embodiment, once energization is started, hunting is prevented by continuing energization at least for the second predetermined time T2 after the addition / subtraction time UDT falls below the first predetermined time T1 due to the energization. To do. The addition timer is for measuring the time from the start of energization and determining whether or not the second predetermined time T2 has elapsed.

  Therefore, if it is determined in step S17 that energization is being performed, the period Δt is added to the addition time UT of the addition timer in step S18. Then, in the next step S19, it is determined whether or not the added time time UT after the addition exceeds the second predetermined time T2. If not, the process ends as it is, that is, with energization continued. When it has exceeded, it moves to step S20 and stops energization to the electric heater 11. Then, in step S21, the addition time UT is returned to zero and the process ends.

  In this way, since the electric heater 11 is made to consume power for at least the second predetermined time T2 from the time when the addition / subtraction time UDT exceeds the first predetermined time T1, the reverse power flow is prevented during that time, so It is expected that there will be no large reverse power flow immediately after the increase in power consumption and the decrease in generated power. Moreover, even if the reverse flow power P again exceeds the first predetermined power P1 immediately after the power supply to the electric heater 11 is stopped, the addition / subtraction time UDT of the adjustment timer is the first predetermined time. Energization is not resumed until T1 is exceeded. Therefore, hunting in which the electric heater 11 repeats ON / OFF at short time intervals is prevented. At the same time, a situation where the power reverse flow determination condition is satisfied is also prevented.

  By executing such a control flow, the value of the addition / subtraction time UDT increases when the value of the reverse flow power P exceeds the first predetermined power P1, and then decreases when the value becomes equal to or less than the first predetermined power P1. To do. When the reverse flow power P changes as shown by the curve in FIG. 2 (1), the reverse flow power P is equal to or lower than the first predetermined power P1 between times t0 and t1, and therefore (3) in FIG. As shown in FIG. 4, the addition / subtraction time UDT remains zero. Between times t1 and t2, since the first predetermined power P1 is exceeded, the addition / subtraction time UDT rises as the addition time increases. Between time t2 and t3, since it is below 1st predetermined electric power P1, the addition / subtraction time UDT falls by subtraction time measurement.

  If the time between times t2 and t3 is long, the addition / subtraction time UDT may become zero due to the subtraction time. In that case, no further subtraction is performed. If a moment occurs when the value of the reverse flow power P becomes equal to or lower than the second predetermined power P2 between the times t2 and t3, the addition / subtraction time UDT is reset to zero by the process of step S13.

  When the reverse flow power P exceeds the first predetermined power P1 again at time t3, the addition / subtraction time UDT starts increasing again. If the period exceeding the first predetermined power P1 continues for a long time, the addition / subtraction time UDT of the adjustment timer exceeds the first predetermined time T1 at time t4. When the first predetermined time T1 is exceeded, energization of the electric heater 11 is started immediately, and the reverse flow power P becomes a negative value as in the period from time t4 to t5. Thereby, the situation where the power reverse flow determination condition is satisfied is prevented.

Once energization is started at time t4, energization is continued for at least the second predetermined time T2. Accordingly, it is expected that the reverse power flow is unlikely to occur during this period, such as an increase in power consumption of the private power load 6 and a decrease in generated power. However, if the expected power is not met, the reverse flow power P exceeds the first predetermined power P1 as soon as the energization is stopped at time t5. More than the acceleration measured time UDT to start the summing timekeeping.

The summing clocking continues energization of the electric heater 11 exceeds the first predetermined time T1 at the time t6 again measured time is started again. Then, energization is performed only for the second predetermined time T2. While the energization is repeatedly turned ON / OFF, the power consumption increases, the generated power decreases, and even if the energization is stopped, the reverse power flow P does not exceed the first predetermined power P1, The situation determined as the occurrence of reverse power flow is avoided.

  Once energization of the electric heater 11 is started, the energization is continued only for the second predetermined time T2, and before the energization of the electric heater 11 is started, the energization stop time exists for at least the first predetermined time T1. To do. Therefore, occurrence of hunting in which the electric heater 11 is repeatedly turned on and off at short time intervals is also prevented. In this way, the cogeneration apparatus 1 of the present embodiment has an effect of avoiding a situation where it is determined that a reverse power flow occurs.

The second predetermined time T2 for supplying power to the electric heater 11, acceleration measurement time UDT is better to adjust depending on the value of reverse power flow P before reaching the first predetermined time T1. When the value of the reverse power flow P is large, the ON / OFF hunting of the electric heater 11 can be reduced by increasing the second predetermined time T2, and a situation where the power reverse flow determination condition is satisfied is generated. The effect that is prevented can be enhanced. Therefore, the average value of the reverse flow power P during the period of time T1 before the addition / subtraction time UDT reaches the first predetermined time T1, or the average value of the difference power between the reverse flow power P and the first predetermined power P1. And the second predetermined time T2 may be proportional to the average value .

  In addition, since the electric heater 11 as a dummy power load consumes surplus power and prevents the occurrence of reverse power flow, it is necessary to consume power reliably when receiving power supply. Therefore, it is necessary to prevent a situation in which power cannot be consumed due to disconnection of the heater or the like despite receiving power supply. Therefore, when the generated power is a single-phase alternating current, for example, as shown in FIG. 5, the heating portion of the electric heater 11 may be divided into a plurality (for example, 4) and connected in parallel. This is because, even if a disconnection occurs in a part of the divided heat generating parts, the power is still consumed only by reducing the power consumption in that part.

  Moreover, the divided heat generating portions 11a to 11d are preferably arranged symmetrically around the pipe 8a of the circulation path 8 as shown in FIG. This is because the pipe 8a can be heated uniformly if arranged in this way. When the generated power is a three-phase alternating current, the heat generating portion of the electric heater 11 is divided into three and Δ-connected or Y-connected, and arranged axially symmetrically around the pipe 8a as illustrated in FIG.

  In other words, a power semiconductor switch such as a thyristor or a triac may be used as the power opening / closing switch 12 for turning on / off the power supply to the electric heater 11. This is because if the power semiconductor switch is used, not only high-speed ON / OFF operation can be performed, but also the reliability of the apparatus can be improved against frequent ON / OFF operation.

  Further, the supply of power may be started at the zero cross timing when the voltage applied to the power semiconductor switch becomes zero, and the supply stop may be performed at the zero cross timing after the supply stop condition is satisfied. If the ON / OFF operation is performed at the timing of the zero cross in this way, the current waveform flowing through the electric heater 11 can be made a sine wave, and therefore the influence of harmonics on the commercial power system due to the ON / OFF operation. It is because it can reduce.

It is a structural example of the cogeneration apparatus 1 which concerns on this invention. It is a figure explaining the view of electric power reverse power flow prevention in the present invention. It is a control flow executed by the control circuit 13a. It is a continuation part of the control flow of FIG. This is a connection example of the electric heater 11. It is an arrangement example of the electric heater 11. It is another example of arrangement | positioning of the electric heater 11. FIG.

Explanation of symbols

In the drawings, 1 is a cogeneration device, 5 is a commercial power system, 6 is a private power load, 8a is piping, 11 is an electric heater (dummy power load), 12 is a power open / close switch, 13 is a reverse power flow prevention control device, 13a Is a control circuit, 13b is a clock pulse generation circuit, 14 is a power meter, P is reverse power flow (measured power), P1 is a first predetermined power, P2 is a second predetermined power, and T1 is a first predetermined time. , T2 indicates a second predetermined time, and T3 indicates a third predetermined time.

Claims (7)

A cogeneration apparatus that supplies generated power to a private power load (6) in cooperation with a commercial power system (5),
A dummy power load (11) connected in parallel to the private power load of the cogeneration apparatus, and a control means for ON / OFF control of power supply to the dummy power load,
The control means includes an addition / subtraction time timer that adds / subtracts clock pulses and adds / subtracts time and an electric power meter (14) that measures the reverse power (P) flowing to the commercial power system, While the measured power (P) of the power meter exceeds the first predetermined power (P1), the addition count is calculated. When the measured power is less than the first predetermined power, the subtraction count to the minimum value zero is calculated. When the second predetermined power (P2) is smaller than the first predetermined power, the counter is reset to zero, and the timing time of the addition / subtraction time timer is set to the first for the dummy power load. It is configured to supply power only for a second predetermined time (T2) from the time when the predetermined time (T1) is exceeded ,
The average value of the measured power (P) or the measured power (P) and the measured power (P) from the time when the time measured by the addition / subtraction timekeeping timer finally leaves zero until the first predetermined time (T1) is reached. A cogeneration apparatus that calculates an average value of the difference power from the first predetermined power (P1) and determines the second predetermined time T2 in proportion to the average value .   2. The cogeneration apparatus according to claim 1, wherein the second predetermined time (T <b> 2) is measured after a first predetermined time (T <b> 1) after the start of power supply to the dummy power load. A cogeneration system, which starts from the time when it falls below   3. The cogeneration apparatus according to claim 1, wherein the control means is a cogeneration apparatus when a time measured by the time adjustment timer exceeds a third predetermined time (T3) longer than the first predetermined time. The cogeneration apparatus is characterized in that the generation of electricity is stopped or the disconnection from the commercial power system is performed.   The cogeneration apparatus according to any one of claims 1 to 3, wherein the power consumption of the dummy power load is set to be equal to or higher than a rated generated power of the cogeneration apparatus. 3. The cogeneration apparatus according to claim 1, wherein when the generated power is a single-phase alternating current, a plurality of pipe heaters having substantially the same rating are connected in parallel, and the pipe heaters are generated during the power generation process. A cogeneration apparatus, which is mounted symmetrically about a pipe (8a) through which heat recovery water for recovering exhaust heat is passed . 3. The cogeneration apparatus according to claim 1, wherein the control means performs an operation of supplying and stopping power to the dummy power load using a power semiconductor switch . 7. The cogeneration apparatus according to claim 6 , wherein the control means starts supplying power to the dummy power load at a zero-cross timing at which the voltage applied to the power semiconductor switch becomes zero, and supply stop and supply stop conditions are satisfied. A cogeneration system that is performed at the timing of zero crossing after it is established .

Images