JPH03142512A - Power generation system - Google Patents

Abstract

PURPOSE:To switch the load mode and to attain the no-break supply of power to a single load in a power plant by switching the target value for the output capacity control via an AC/DC converter to the value of the single load in the plant from the command value and separating an AC system when the output capacity is equal to its target value. CONSTITUTION:A load mode switch command signal 14 is sent to an AC/DC converter 2 to switch a system linking mode to an intra-plant single load mode. Thus the output capacity given from the converter 2 and excluding the auxiliary equipment motive power load 8 is obtained from PT 12 and CT 17. Then the electric power of an intra-plant single load 6 obtained from the PT 12 and CT 18 is defined as the new target value in place of the hitherto target value obtained from an output capacity command signal 15 for output capacity control. Thus this control is carried on based on the new target value. When the output capacity given from the converter 2 is coincident with the electric power of the load 6 serving as the target value, the converter 2 opens a load mode switching breaker 16 and controls the output voltage to a fixed level via the intra-plant single load mode. Thus the no-break supply of power is secured to the load 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power generation system using a fuel cell or the like, and particularly relates to a load mode switching method thereof.

[Conventional technology]

Figure 2 shows, for example, Fuji Jiho Vo1.61 No. 2 P.
128 (published in February 1988) is a block circuit diagram showing a simplified conventional fuel cell power generation system of this type. In the figure, (1) is a fuel cell that is a DC power generation device, ('2: J is an orthogonal conversion device that converts the output of DC power generated by the fuel cell (1) into output of AC power,
At the same time, load mode switching control is also performed. (3) is a step-up transformer that boosts the output voltage of the orthogonal converter (2) to the voltage of the AC system (4). The synchronous circuit breaker (6) for interconnection is a single load within the plant that is required in the building, equipment, etc. in the power plant of the fuel cell power generation system, and is connected to the synchronous circuit breaker (5) via the open circuit (7). step-up transformer +31 ff
! ! Connected to 1. (8) is the auxiliary power load such as the fuel f[battery (1)] of the fuel cell power generation system, and is connected to the AC system A) side of the synchronous breaker (5) via the 31X disconnector (9). .

00) and (11) are CT and PT, respectively, for detecting the output t of the orthogonal transformer (2), and (12) is P for detecting the voltage of the AC system (4) when connected to the system.
T, (13) is an operation panel for issuing operation commands to the orthogonal transformation device (2).

Next, the operation, especially the load mode switching operation, will be explained. First, the operation when starting up the fuel cell power generation system and entering grid connection mode will be described. In this case, the synchronous circuit breaker (5) is in an open state and the circuit breaker (9) is closed to supply power from the AC system (4) to the auxiliary power load (8). As a result, the auxiliary equipment of each device of the fuel cell power generation system becomes operational. Here, when the operation panel (13) sends the load mode switching command signal (14) to the grid connection mode to the orthogonal conversion device (21), the output voltage of the fuel cell (1) starts to rise, and the PT When the output voltages of (11) and PT (12) are the same and synchronized, the synchronous circuit breaker is turned on. As a result, the fuel cell power generation system enters grid-connected mode operation, and the orthogonal converter (21 is the control panel (1
Output capacity control is performed by using the output capacity command signal (15) from 3) to control the output capacity using the command value as a target value.

In addition, after the synchronous circuit breaker (51) is turned on, the switch (7) is turned on and the in-house independent load (6) becomes operational.

That is, in the grid connection mode, the orthogonal transformation device (2)
operates under output capacity control, and does not have the ability to compensate for a constant voltage for the variable load (6) within the station, and can only operate when it is possible to receive power from the AC system (4). It becomes a posture.

Next, when shifting from the grid-connected mode to the in-house independent load mode, first the fuel cell (1) is stopped and the orthogonal conversion device ( 2), the synchronous circuit breaker (51) and switch (7) are opened to disconnect the AC system (4), and at the same time, the isolated load (6) in the station is also
Stop it once.

Thereafter, the fuel cell (1) and the orthogonal converter (21) are restarted, and the switch (7) is turned on when the output voltage of P ).In this in-station single load mode, the orthogonal converter (21) operates under constant output voltage control to maintain its output voltage at the rated voltage, which is a predetermined setting value. Therefore, the in-house independent load (6) is supplied with power at a constant voltage regardless of load fluctuations.

Note that power is supplied to the auxiliary power load (8) from the AC system (4) even in this in-house single load mode.

Next, when returning to the grid connection mode from the station single load mode, after checking the synchronization conditions from the output voltages of P T (11) and P T (12), the synchronous breaker (
5) and shift to grid connection mode. Along with this, the orthogonal conversion device (2) changes its control method from constant output voltage control to output capacity control again.

[Problem to be solved by the invention]

Since the conventional fuel cell power generation system is configured as described above, it is necessary to stop the fuel cell (1) and the orthogonal converter (2) especially when switching from the grid connection mode to the in-house single load mode. In addition, since the power supply to the individual station load (6) is stopped, it takes a long time to switch the mode and the amount of fuel consumed increases.
However, there was a problem in that it was not possible to select a load that required continuous operation.

In addition, since the auxiliary power load (8) receives power from the AC system (4) even in the station single load mode, if the AC system (4) experiences a power outage during this period, the fuel cell power generation system will also have to stop. First, there was the problem that it could not be said to be a truly independent power source.

This invention was made to solve the above-mentioned problems, and provides a power generation system that is capable of switching load modes without stopping output and that also enables uninterrupted power supply to a single load within a station. The purpose is to

Another object of the present invention is to obtain a power generation system that can continue supplying power to a single station load even if a power outage occurs in the AC system during operation in the station single load mode.

[Means and effects for solving the problem] The power generation system according to the present invention changes the target value of the output capacity control by the orthogonal conversion device from the previous command value when transitioning from the grid-connected mode to the station isolated load mode. The load amount is replaced with the load amount of the individual load within the station, and the AC system is disconnected when the amount matches.

In this case, when the target value of output capacity control matches the load amount of the station's single load, the output from the power generation system to the AC system is zero, so even if the AC system is disconnected, there will be no load fluctuation, and the station's Stable transition to single load mode is possible.

Furthermore, it includes a first switch whose one end is connected to the orthogonal conversion device, and a second switch which is connected between the other end of the first switch and the AC system, and both of the switches are connected to each other. In the case where the auxiliary power load and the station independent load are connected to the mutually connected parts, and the system is started by opening the first switch and closing the second switch, the station independent load In the mode, the first switch is closed and the second switch is opened, so that the auxiliary power load is supplied with power from the power generation system itself, and operation continues regardless of the AC system.

〔Example〕

FIG. 1 is a block circuit diagram showing a fuel cell power generation system according to an embodiment of the present invention. In the figure, (1) to 15) are the same or equivalent parts as in the conventional one, and their explanation will be omitted. However, in addition to the synchronous breaker (51) as the first switch, this synchronous breaker (51 and the AC system (4
) is installed between the load mode switching circuit breaker (16) as a second switch, and the double-way circuit breaker (51 (16) constitutes a switching device. The auxiliary power load (8) is connected to the part that interconnects the synchronous circuit breaker (51) and the load mode switching circuit breaker (16). CT (18) inserted between the branch point to the auxiliary power load (8)
is a CT that detects the current to the in-house independent load (6), (I9
) is a PT that detects the voltage of the AC system (4).

Next, the operation will be explained. When starting up the fuel cell power generation system and entering the grid connection mode, first turn on the load mode switching circuit breaker (16) and switch from the AC system (7) to the station independent load (6) and the auxiliary power load (8). ).

As a result, each device in the fuel cell power generation system becomes operational. After that, the conditions for synchronization are confirmed from the output voltages of P T (11) and P T (+2) in the same way as before, and the conditions are met. When the condition is satisfied, the synchronous circuit breaker (131) is turned on and operation begins in grid connection mode.

Next, when the load mode switching command signal (14) from the grid connection mode to the in-house independent load mode is sent to the orthogonal conversion device (2), the output capacity from the orthogonal conversion device (21) minus the auxiliary power load (8) is P T (12) and CT (1
7), and in place of the target value based on the output capacity command signal (15) in output capacity control,
2) and CT (+8>)
) continues output capacity control using the load power as the new target value. Eventually, when the output capacity of the above-mentioned orthogonal converter (2) matches the target value of the load power of the individual load (6) in the station, the orthogonal converter (2) issues a command to the load mode switching circuit breaker (16). This is then opened to switch to constant output voltage control using in-house single load mode.

In other words, the transition from the grid-connected mode to the in-house independent load mode occurs without stopping the output of the fuel cell power generation system, so there is no increase in fuel consumption due to the stoppage of the fuel cell (1), or an increase in the in-house independent load (6). Power supply stoppage is avoided and mode switching time is also significantly shortened.

In addition, when operating in the station single load mode, the auxiliary power load (8)
receives power from the orthogonal transformer (2), so during this time,
Even in the event of a power outage in the AC system (4), the fuel cell power generation system can continue operating without any problems, and the isolated load within the station (
6) constant operation is a distant relative.

Next, when returning from in-house isolated load mode to grid-connected mode, check the synchronization conditions from the output voltage of PT (12) and PT (1) as before, and then switch the load mode. The circuit breaker (16) is turned on to shift to grid connection mode. Along with this, the control method of the orthogonal conversion device (■) is changed from constant output voltage control to output capacity control again.

In the above embodiments, the DC power generation device is a fuel cell, but it may be a solar cell or other type of device that generates DC output.

〔Effect of the invention〕

As described above, in this invention, the target value for output capacity control in the grid connection mode is replaced with the load amount of the individual station load from the command value, and when the values match, the AC system is disconnected and the output capacity control is switched to the individual station load mode. As a result, it is possible to shift from grid-connected mode to on-site isolated load mode without stopping the output of the power generation system.As a result, the mode switching time is significantly shortened, and the on-site isolated load mode can be switched at all times. Operation becomes possible.

Furthermore, in a system in which a predetermined first and second switch is provided, and the auxiliary power load and the station independent load are connected to the connection point of both switches to start the system in a predetermined sequence, When operating in single load mode, the auxiliary power load receives power from the orthogonal converter, so even if the AC system is out of power, the power generation system can continue operating without any problems, providing independent power that does not depend on the AC system. Functions as a power source.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing a fuel cell power generation system according to an embodiment of the present invention, and FIG. 2 is a block circuit diagram showing a conventional system. In the figure, (1) is a fuel cell as a DC power generation device;
(2) is an orthogonal conversion device, (4) is an AC system, (51 is a synchronous circuit breaker as the first switch, (6) is an independent station load, (8) is an auxiliary power load, (16) is This is a load mode switching circuit breaker as a second switch. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A DC power generation device, an orthogonal conversion device that converts the output of this DC power generation device into AC output, and a switchgear that opens and closes the connection between this orthogonal conversion device and the individual load in the power plant and the AC system. In the grid-connected mode, the above-mentioned in-house isolated load and the AC system are connected to an orthogonal converter, and the output capacity of the orthogonal converter is controlled using its command value as a target value. In the load mode, the above-mentioned AC system is disconnected, the above-mentioned in-house independent load is connected to the orthogonal conversion device, and output voltage constant control is performed to maintain the output voltage of the above-mentioned orthogonal conversion device at a predetermined set value. By replacing the control target value from the command value with the load amount of the station single load and disconnecting the AC system when the values match, the system continuously transitions from the grid connection mode to the station single load mode. A power generation system characterized by: (2) The switchgear is composed of a first switch whose one end is connected to the orthogonal converter, and a second switch which is connected between the other end of the first switch and the AC system. , an auxiliary power load and an in-house independent load are connected to the part where both of the switches are connected to each other, and the first switch is opened and the second switch is closed to start the system. The power generation system according to claim 1, characterized in that: