KR20100074985A - Method and apparatus for controlling of power in grid connected type fuel cell system - Google Patents

Abstract

PURPOSE: A power control method of a system interlinked fuel cell system and an apparatus thereof are provided to improve the reliability of a system by reducing unnecessary time, fuel, and power consumption caused by system down and rebooting of a system. CONSTITUTION: An electric power converting unit(110) interlinks a part of the DC power supply outputted from a fuel battery(102) with an electric power system(120). The electric power system is supplied with the electrical energy generated in the electric power converting unit. An instantaneous voltage drop compensation unit(124) is connected with the power converter during the restoration period of the malfunctioning time.

Description

Method and Apparatus for Controlling Power in Grid Connected Fuel Cell System

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system, and more particularly, to a power control method and apparatus for a grid-connected fuel cell system, which enables the fuel cell system to stably supply power in the event of a power failure.

Due to the depletion of fossil fuels and the crisis of energy, global demands and interests on renewable energy are increasing, and fuel cells are at the center. The fuel cell has a very high power generation efficiency for directly converting chemical energy of a hydrocarbon-based fuel such as natural gas, naphtha and methanol into electrical energy. In addition, due to the very low pollution, it can be installed near electric power demands or distributed in areas where electric power demands are close, and can be used from small capacity power generation facilities to large power generation facilities.

1 is a block diagram of a typical grid-connected fuel cell system. 1, an oxygen supply unit 10 and a fuel gas supply unit 12 are provided. In addition, the fuel cell 20 is configured to generate a DC power supply DC by reacting the oxygen supplied from the oxygen supply unit 10 and the fuel gas supplied from the fuel gas supply unit 12.

A part of the DC power generated by the fuel cell 20 is supplied as a system operating power for operating the fuel cell system.

The remaining part of the DC power generated by the fuel cell 20 is used in the load 50 in connection with the power system 40. To this end, a power conversion unit (PCS: Power Conditioning System) 30 for converting the DC power generated in the fuel cell into AC power is provided. The power converter 30 includes a DC-DC converter 32 for converting a DC power output from the fuel cell 20 to a predetermined level and a DC power obtained from the DC-DC converter 32. It includes a DC-AC inverter 34 to convert to an AC power source that can be used in the power system 40.

Such a grid-connected fuel cell system determines whether the power system is abnormal in the DC-AC inverter 34 and operates normally when there is no error.

At this time, since the grid-connected fuel cell system does not receive DC power from the fuel cell 20 at the time of initial driving, the fuel cell system receives power from the power system 40 as an initial driving power source of the fuel cell system. Will be used.

In addition, when a failure occurs in the power system 40 during the driving, the power converter 30 disconnects the power system 40 and stops the operation of the fuel cell system.

However, the fuel cell system and the power system 40 are indiscriminately shut off even in the case of a momentary failure such as instantaneous voltage drop, instantaneous voltage rise, and instantaneous power failure. Most of the failures are those that can be automatically recovered within 1 to 2 seconds. If the failure causes separation of the system and the power system, it does not help the power generation efficiency.

That is, when the system and the power system are separated due to the momentary failure, a considerable time is required for restarting the grid-connected system later, and fuel and power are unnecessarily consumed.

In addition, when the system is stopped due to the momentary failure, time, fuel, and power are consumed.

Therefore, there is a problem in that the power of the grid-connected fuel cell system is not stably supplied and power quality is deteriorated.

Therefore, an object of the present invention is to solve the above problems, the power supply control method and apparatus for a grid-connected fuel cell system that allows the system to continue to operate even if a power failure in the grid-associated system occurs. To provide.

Another object of the present invention is to improve the power quality of the grid connection system.

According to a feature of the present invention for achieving the above object, a fuel cell; A power conversion unit for connecting a portion of the DC power output from the fuel cell with a power system; A power system receiving electric energy generated by the power conversion unit; And, when a momentary failure occurs in the power system is connected to the power conversion unit during the time the momentary failure is recovered, the instantaneous voltage drop compensation unit for compensating the power of the power system required for the power conversion unit; is configured to include .

The compensation unit charging unit for charging the instantaneous voltage drop compensation unit is further included, and the compensation unit charging unit charges the instantaneous voltage drop compensation unit using the system voltage of the power system.

An auxiliary power supply unit for supplying power so that the fuel cell system is stably stopped when an emergency stop of the fuel cell system occurs; The auxiliary power charging unit may further include an auxiliary power charging unit for charging the auxiliary power unit by receiving DC power from the fuel cell when the auxiliary power unit is discharged.

According to another aspect of the invention, the step of checking whether the instantaneous failure occurred in the power system for supplying power to the power converter in the grid-connected fuel cell system; And, as a result of the check, if the instantaneous failure occurs in the power system, controlling to continue to supply to the power conversion unit as much as the system voltage supplied from the power system until the momentary failure recovery.

According to another feature of the invention, the step of checking whether the instantaneous failure in the power system in the grid-connected fuel cell system; As a result of the check, when an instantaneous failure occurs in the power system, the power converter and the power system are separated from each other. step; Continuously compensating power of the power system to the power converter while the instantaneous voltage drop compensation unit is discharged; And reconnecting the power converter and the power system when the momentary failure is restored to control the power system to continuously supply power.

When the power system is connected again, the step further comprises the step of charging the voltage drop compensation unit.

If the momentary failure is not recovered, the operation of the power converter is stopped, and the system-associated fuel cell system is emergency stopped.

According to the present invention, when an instantaneous failure such as instantaneous voltage drop (Sag), instantaneous voltage rise (Swell), instantaneous power failure, etc. related to the power quality occurs in the grid system, the system and the power system are separated for a predetermined time. Since the power supply can be supplied at the same level as supplied by the power system, the system can be supplied stably without stopping the system.

In addition, even if the instantaneous failure occurs, it is not necessary to stop the operation of the system, thereby reducing unnecessary time, fuel, and power consumption due to the stop and restart of the system. This improves the reliability of the system.

Hereinafter, a configuration of a preferred embodiment of a power control method and apparatus for a grid-connected fuel cell system according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram of a grid-connected fuel cell system according to a preferred embodiment of the present invention.

2, a fuel supply unit 100 is provided to supply oxygen and fuel so that the fuel cell generates a DC power source.

A fuel cell 102 for generating a DC power source by reacting oxygen and fuel gas supplied from the fuel supply unit 100 is provided. A first switch sw1 is connected to an output terminal of the fuel cell 102. The first switch sw1 serves to supply or cut off the generated DC power.

A DC-DC converter 104 is provided to convert some of the DC power generated by the fuel cell 102 into a driving power of a BOP 130. The BOP 130 is a peripheral device for driving a fuel cell system. Examples include pumps, blowers, various valves and sensors.

When the auxiliary power supply 106 for supplying driving power to the BOP 130 and the auxiliary power supply 106 is discharged in case of emergency stop of the fuel cell system, it is for charging with DC power output from the fuel cell 102. An auxiliary power charging unit (hereinafter referred to as a 'first charging unit') 108 is provided. The input terminal of the first charging unit 108 is provided with a second switch sw2 connected to one end of the first switch sw1. In addition, a third switch sw3 is installed between the auxiliary power supply 106 and the BOP 130. The third switch sw3 is shorted when the fuel cell system is in an emergency stop.

The power conversion unit 110 is provided to associate the rest of the DC power generated by the fuel cell 102 with the power system 120 to be described below. The power conversion unit 110 powers the DC-DC converter 112 for converting the DC power output from the fuel cell 102 to a predetermined level and the DC power obtained from the DC-DC converter 112. It includes a DC-AC inverter 114 to convert to an AC power source that can be used in the system 120.

A power system 120 that receives the electric energy generated by the power converter 110 is provided.

An AC-DC converter 122 for converting the AC power generated by the power converter 110 into the drive power of the BOP 130 by a system linkage method of the power system 120 is provided. The AC-DC converter 122 serves to supply a system voltage to the operating power of the fuel cell system at the initial startup of the fuel cell system. A fourth switch sw4 is installed between the power converter 110 and the AC-DC converter 122. The fourth switch sw4 should be shorted when the fuel cell system is initially driven.

A momentary voltage drop compensator (hereinafter, referred to as a “compensator”) 124 connected to the output of the power system 120 at the moment of failure of the power system 120 is provided. Although not shown, the compensation unit 124 includes a storage unit such as a capacitor and an inverter. The inverter serves to convert a grid voltage into an AC power source because the power stored in the storage unit is a DC power source.

The compensator 124 should be in a state in which the fuel cell system is separated from the power converter 110 in a normal operation state. Thus, the power converter 110 should be selectively connected to the power system 120 or the compensation unit 124. Accordingly, the switching unit 128 having two contacts is provided at the intersection of the power converter 110, the power system 120, and the compensator 124. The switching unit is composed of a 'a' contact and a 'b' contact. When the switching unit 128 is located at the 'a' contact point, the power conversion unit 110 and the power system 120 are connected. When the switching unit 128 is located at the 'b' contact point, the power conversion unit 110 and the compensation unit ( 124 is connected. A compensation part charging part (hereinafter referred to as a 'second charging part') 126 for charging the compensation part 124 is provided. The second charger 126 receives power from the power system 120 to charge the compensator 124. A fifth switch sw5 is installed between the power system 120 and the second charging unit 126.

The voltage detection sensor 129 for measuring the system voltage of the power system 120 is provided.

The switching operation of the first to fifth switches sw1 to sw5 and the switching unit 128 is controlled according to the operation mode of the fuel cell system, so that the operation continues without stopping the operation of the fuel cell system even during a momentary failure. It is provided with a control unit for controlling to be. In this embodiment, the controller is divided into a first controller 116 and a second controller 132. The first control unit 116 is provided in the power conversion unit 110 to control the switching operation of the switching unit 128, the second control unit 132 is the first to fifth switches (sw1 ~ sw5). Control the switching operation. However, the first control unit 116 and the second control unit 132 may not be configured separately. One control unit may control both the switching unit 128 and the first to fifth switches sw1 to sw5 in the state provided to the power conversion unit 110, the BOP 130, or a predetermined location of the fuel cell system. have.

Next, the power control method of the grid-connected fuel cell system of the present embodiment having the above configuration will be described in detail.

For convenience of description, in describing the present embodiment, an operation mode of the fuel cell system is divided into a start mode, a normal operation mode, a momentary failure mode, and a stop mode.

Startup mode

The grid-connected fuel cell system is started by receiving power from the power system 120. That is, the fuel cell system is supplied from the power system 120 because the DC power source for the first start cannot be supplied by itself. To this end, when the fuel cell system starts to be driven, the first control unit 116 maintains the contact point of the switching unit 128 as the 'a' contact point, and the second control unit 132 operates the fourth switch sw4. The short circuit causes the system voltage to be supplied from the power system 120 to the AC-DC converter 122. The AC-DC converter 122 converts the grid voltage into a DC power required to drive the BOP 130 and supplies the converted DC voltage.

The start mode is a state before the fuel cell system operates stably. Thus, the second control unit 132 maintains the first to third switches sw1 to sw3 in the open state until the DC power is stably output from the fuel cell 102. However, if it is determined that the charging of the compensation unit 124 is necessary by checking the charging state of the compensation unit 124, the second control unit 132 moves the fifth switch sw5 from the open state to the short state. Switch. Then, the grid voltage is supplied to the second charger 126 through the path of the fifth switch sw5, and the second charger 126 is charged by supplying the grid voltage to the compensator 124. When the charging process is completed, the second control unit 132 opens the fifth switch sw5.

Normal operation mode

The normal operation mode is a mode in which the fuel cell system is generated.

The normal operation mode is from the time point at which the DC power is stably generated from the fuel cell 102 by the start mode. Once the DC power is stably output from the fuel cell 120, the second controller 132 shorts the first switch sw1 in an open state to supply the DC power to the BOP 130. When the first switch sw1 is shorted, some of the DC power generated by the fuel cell 102 is converted into a voltage of a predetermined level by the DC-DC converter 104 and supplied to the BOP 130.

The rest of the DC power output of the fuel cell 102 is supplied to the power converter 110. The power converter 110 serves to convert the DC power into AC power that is commercial power. In this case, since the driving power of the BOP 130 is supplied through the DC-DC converter 104, the second control unit 132 opens the fourth switch sw4 to open the fourth switch sw4 from the power conversion unit 110. Blocking the supply of power to the BOP 130.

In the normal operation mode, the first controller 116 keeps the contact of the switching unit 128 connected to the 'a' contact. In addition, the second control unit 132 checks the state of charge of the auxiliary power supply unit 106, and when the auxiliary power supply unit 106 is discharged, short-circuits the second switch sw2 to output power from the fuel cell 102. As a result, the second charging unit 108 charges the auxiliary power supply unit 106. The second control unit 132 opens the second switch sw2 when the charging of the auxiliary power supply unit 106 is completed.

Instantaneous failure Generation Mode

The instantaneous failure mode will be described with reference to FIG. 3. 3 is a flowchart illustrating a power control method of a grid-connected fuel cell system according to an exemplary embodiment of the present invention.

The first control unit 116 monitors the operating state of the grid-connected fuel cell system (S100). Thus, when the fuel cell system is in normal operation, and instantaneous failures such as instantaneous voltage drop (Sag), instantaneous voltage rise (Swell), and instantaneous power failure in the power system 120 occur (s102), The first controller 116 moves the 'a' contact of the switching unit 128 to the 'b' contact to separate the output of the power converter 110 from the power system 120, and instead, the power converter ( 110 and the compensation unit 124 is connected (s104).

Then, the compensator 124 is discharged to compensate for the power of the power system 120 required by the power converter 110, so that the power converter 110 can continue to operate ( s106).

The first controller 116 monitors the detected value of the voltage sensor 129. Thus, when the system voltage detected from the voltage sensor 129 is in a normal state within 1 to 2 seconds after the occurrence of the instantaneous failure (s108), that is, when the momentary failure is restored, the first control unit 116 switches the switching unit ( 128, the 'b' contact is moved back to the 'a' contact to connect the power converter 110 and the power system 120 (s110), and the normal operation state (s112). In other words, since the failure usually has a characteristic of automatically recovering from failure within 1 to 2 seconds, the first controller 116 controls the switching unit 128 approximately 1 to 2 seconds after the failure occurs. The power is supplied from the compensator 124 only within the time when the momentary failure is recovered.

In addition, since the power supply of the compensator 124 is discharged during the recovery operation due to the instantaneous failure, the second controller 132 shorts the fifth switch sw5 when the grid voltage returns to the normal state. The compensation unit 124 is charged by the second charging unit 126. When charging of the compensator 124 is completed, the second controller 132 opens the fifth switch sw5.

That is, in the instantaneous failure generation mode, the fuel cell system is continuously operated by connecting the power converter 110 and the compensation unit 124 during the instantaneous failure occurrence time. This can prevent unnecessary shutdown and restart.

However, when the instantaneous failure is not restored, for example, if the grid voltage detected by the voltage sensor 129 is not restored to the normal state within 1 to 2 seconds, the operation of the power converter 110 is stopped and the fuel cell is stopped. Emergency stop the system (s114).

Stop mode

When the fuel cell system is normally stopped, the second control unit 132 cuts off the fuel supplied from the fuel supply unit 100 to the fuel cell 102 and opens the first switch sw1. In addition, the second controller 132 shorts the fourth switch sw4 to supply a system voltage to the AC-DC converter 122, and the AC-DC converter 122 converts the system voltage to the BOP. To 130. As a result, the fuel cell system is normally stopped.

However, when the instantaneous failure does not recover as described above, the second controller 132 cuts off the fuel supplied to the fuel cell 102 and opens the first switch sw1. In this case, the BOP 130 may not be supplied from the power system 120. That is, because a failure occurs in the power system 120, the fuel converter 110 and the power system 120 is separated. Accordingly, the second controller 132 shorts the third switch sw3 to supply the auxiliary power from the auxiliary power supply 106 to the BOP 130. Thus, the fuel cell system is stably stopped by the auxiliary power of the auxiliary power supply 106.

As described in the normal operation mode, the second controller 132 checks the state of charge of the auxiliary power supply 132, and if the auxiliary power supply 132 is discharged, shortens the second switch sw2 to supply the fuel. The auxiliary power supply 106 is charged by the power output from the battery 100. The second control unit 132 opens the second switch sw2 when the charging of the auxiliary power supply unit 106 is completed.

As described above, the present invention allows the fuel cell system to continue to operate even in the event of an instantaneous failure such as instantaneous voltage drop (Sag), instantaneous voltage rise (Swell), and instantaneous power failure.

The scope of the present invention is not limited to the embodiments described above, but is defined by the claims, and various changes and modifications can be made by those skilled in the art within the scope of the claims. It is self evident.

That is, the present invention can be applied to all types of fuel cell systems, for example, polymer electrolyte type (PEMFC), solid oxide type (SOFC), direct methanol (DMFC), and overall system-linked fuel cell systems regardless of capacity. have.

1 is a block diagram of a typical grid-connected fuel cell system

2 is a block diagram of a system-associated fuel cell system according to a preferred embodiment of the present invention.

3 is a flowchart of a power control method of a grid-connected fuel cell system according to an exemplary embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

102 fuel cell 104 DC-DC converter

106: auxiliary power supply unit 108: auxiliary power supply charging unit

110: power conversion unit 116: first control unit

120: power system 122: AC-DC converter

124: voltage drop compensation unit 126: compensation unit charging unit

130: peripheral device (BOP) 132: second control unit

Claims (7)

Fuel cell; A power conversion unit for connecting a portion of the DC power output from the fuel cell with a power system; A power system receiving electric energy generated by the power conversion unit; And, And a momentary voltage drop compensator for compensating for power of the power system required for the power converter by being connected with the power converter during the time when the momentary failure occurs in the power system. A power control device for a grid-connected fuel cell system. The method of claim 1, Further comprising a compensation charging unit for charging the instantaneous voltage drop compensation unit, And the compensation charging unit charges the instantaneous voltage drop compensation unit by using the grid voltage of the power system. The method of claim 1, An auxiliary power supply unit for supplying power so that the fuel cell system is stably stopped when an emergency stop of the fuel cell system occurs; And, And a secondary power charging unit configured to receive DC power from the fuel cell to charge the auxiliary power unit when the auxiliary power unit is discharged. Checking whether an instantaneous failure occurs in a power system supplying power to a power conversion unit in a grid-connected fuel cell system; And, If the check results, when the instantaneous failure occurs in the power system, the step of controlling to continue to supply as much as the system voltage supplied from the power system to the power converter until the momentary failure recovery; Method for controlling power of a fuel cell system. Checking whether a power failure occurs in the power system in the grid-connected fuel cell system; As a result of the check, when an instantaneous failure occurs in the power system, the power converter and the power system are separated from each other. step; Continuously compensating for power of a power system required by the power converter while the instantaneous voltage drop compensation unit is discharged; And, And reconnecting the power converter and the power system to control the continuous supply of power from the power system when the momentary failure is restored. The method of claim 5, And recharging the instantaneous voltage drop compensator when the power system is connected again. The method of claim 5, And stopping the operation of the power converter and emergency stopping the system-associated fuel cell system when the momentary failure is not restored.

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