WO2010090402A2

WO2010090402A2 - Combined heat and power cogeneration system for a fuel cell, and control method thereof

Info

Publication number: WO2010090402A2
Application number: PCT/KR2010/000323
Authority: WO
Inventors: 김호석; 홍병선; 신미남
Original assignee: (주)퓨얼셀 파워
Priority date: 2009-02-09
Filing date: 2010-01-18
Publication date: 2010-08-12
Also published as: KR20100091023A; WO2010090402A3; KR101022011B1; CN102308420A; CN102308420B

Abstract

A combined heat and power cogeneration system for a fuel cell according to the present invention comprises: a fuel cell that produces direct current power using fuel gas containing hydrogen and air containing oxygen; a power converter which converts the direct current power produced by the fuel cell into alternating current power; a power divider which selects commercial power from an electric power system and power produced by the fuel cell and divides the selected power into loads; a waste heat recovery unit for recovering heat generated by the fuel cell; and a fuel cell controller which controls the fuel cell, the power converter, the power divider, and the waste heat recovery unit, and controls the commercial power such that the price of the commercial power and the price of the produced power coincide with each other at a preset level.

Description

Fuel cell cogeneration system and control method

The present invention relates to a fuel cell cogeneration system, and more particularly, to a fuel cell cogeneration system having an economical efficiency by resolving a power imbalance difference between a production power of a fuel cell and a load power of a user, and a control method thereof.

For example, a fuel cell uses a hydrocarbon-based power source (LNG, LPG, etc.) to replace a reformer gas rich in hydrogen in a fuel processing device, and supplies the reformed gas together with oxygen in the air to the fuel cell stack, thereby providing electrochemistry. Reaction produces DC power, converts DC power into AC power using a power converter, and recovers heat generated in the power production process and stores the water in the heat storage tank.

Korean Patent No. 0661920 discloses a fuel cell system that can operate in response to a load. The fuel cell system includes a fuel supply unit for controlling the supply amount of power generation materials, an air supply unit for controlling the supply amount of air, an electrical output unit for converting power from the fuel cell stack to supply the load, and an electrical output unit for supplying the load. And a power meter for detecting the remaining power remaining and the supplementary power supplied through the commercial power supply, and a controller for calculating the difference between the residual power and the supplementary power detected by the power meter and controlling the power output of the fuel cell stack. do.

However, this fuel cell system does not judge the economic feasibility of comparing the price of electricity produced by the fuel cell stack to the price of power raw materials used. Therefore, the fuel cell system uses the power generated from the commercial power and renewable energy (e.g., wind, solar, etc.) of a system power source having a low power generation price when generating power using a fuel cell cogeneration system. Makes driving difficult. Therefore, in operation of the fuel cell system, economic efficiency may be limited.

One aspect of the present invention is to use the commercial power of the system power source to which the progressive charge system is applied in the low-cost area, while eliminating the power imbalance between the fuel cell production power and the load power of the user fuel cell cogeneration It is to provide a system and a control method thereof.

In a fuel cell cogeneration system according to an embodiment of the present invention, a fuel cell for producing direct current power using fuel gas containing hydrogen and air containing oxygen, and the direct current power produced by the fuel cell as alternating current power A power converter for converting, a power divider for selecting commercial power of a system power source and production power of the fuel cell and distributing it to load power of a load, a waste heat recovery unit for recovering heat generated from the fuel cell, and the fuel cell and the power And a fuel cell controller for controlling the converter, the power distributor, and the waste heat recovery device, and controlling the amount of commercial power so that the commercial power price and the production power price coincide at the set values.

The fuel cell controller may further include an economic recognizer that recognizes economic efficiency by comparing the commercial power price and the production power price.

The fuel cell controller may further include a load follower that determines an increase or decrease in the direction of power generation according to an imbalance difference between the production power and the load power.

The fuel cell controller includes a data storage RAM for storing the commercial power amount and the commercial power price WP calculated in real time by the load follower, and a power generation step corresponding to the rated power generation in consideration of the variation of the load power. It may include an operation controller for controlling in multiple stages.

In the fuel cell cogeneration system control method according to an embodiment of the present invention, the first calculation step of calculating the production power price (MWP) of the production power produced by the fuel cell, commercial power price using the commercial power of the system power ( A second calculation step of calculating WP, and comparing the MWP and the commercial power price (WP) to determine whether the economic index (EW) that recognizes the economics of the production power is positive or negative And supplying commercial power when the economic index is positive, and supplying production power when the economic index is negative.

In the first calculation step, it is possible to calculate the production power price (MWP) from the consumption of the power raw material (F), the raw material price (FP, price / Nm ³ ) and the amount of power produced.

The second calculating step includes an imbalance difference calculation step of calculating an imbalance difference (ΔP = P2-P1) between the production power P1 and the load power P2, and the imbalance difference (ΔP = P2-P1). A range determination step of determining whether the deviation is out of the preset range, the production power (P1) is reduced if the imbalance difference falls within the preset value range, and increases the production power (P1) if out of the preset range And an integration step of integrating (∫ΔP) the commercial power amount of the commercial power supplied by the unbalanced difference, and calculating the commercial power price by comparing the accumulated commercial power amount with the progressive charge system. have.

In the power production step, a commercial power amount coinciding with the commercial power price and the production power price is referred to as coincidence commercial power amount Pe, and when the used commercial power amount is within a range of Pe / 3, the power imbalance difference is rated. The first power generation stage, which produces less than the actual load power to produce 3/10 of the power generation, if the commercial power used is in the range of Pe / 3 or more and less than 2Pe / 3, the power imbalance difference is 2/10 of the rated power generation. In the second power production stage, which produces less than the actual load power, if the commercial power used is in the range of 2Pe / 3 or more and less than Pe, the power unbalance difference is less than the actual load power so that it becomes 1/10 of the rated power generation. The third electric power producing step of producing the electric power, and the fourth electric power producing the electric power, in which the power imbalance difference is eliminated when the amount of commercial power used is in the range of Pe or more. It may include the production phase.

As described above, according to an embodiment of the present invention, since the fuel cell controller is used to control the amount of commercial power used so that the commercial power price and the production power price coincide at the set values, the commercial power to which the progressive rate system is applied is preferentially used in the low cost area. This has the effect of improving economics. In addition, since the production power of the fuel cell is increased or decreased according to the range of the power imbalance between the production power of the fuel cell and the load power of the user, there is an effect of improving the economic efficiency even in the process of resolving the unbalance difference.

1 is a configuration diagram schematically showing a fuel cell cogeneration system according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a control method of the fuel cell cogeneration system of FIG. 1.

3 is a graph comparing the amount of electricity and the price of power of the commercial power of the system power and the production power of the fuel cell.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like elements throughout the specification.

1 is a configuration diagram schematically showing a fuel cell cogeneration system according to an embodiment of the present invention. Referring to FIG. 1, a fuel cell cogeneration system 100 (hereinafter, simply referred to as a “system”) of an embodiment includes a fuel cell 10, a power converter 20, a power distributor 30, and a waste heat recovery 40. ) And a fuel cell controller 50.

The fuel cell 10 includes, for example, a fuel processor 11 for converting a hydrocarbon-based raw material into a reformed gas rich in hydrogen, a fuel cell stack 12 for producing direct current power using hydrogen and oxygen in the air; Balance of Plant (BOP) 13 necessary for producing electric power, and a heat exchanger 14 for recovering heat generated by the fuel processing device 11 and the fuel processing stack 12.

The power converter 20 converts the DC power produced by the fuel cell 10 into AC power. For example, the power converter 20 includes a DC-DC converter 21 for converting DC power into DC power, an inverter 22 for converting DC power into AC power, and a first power for measuring the converted AC power. Meter 23. For example, the first power meter 23 includes a current sensor and a voltage sensor.

The second power meter 24 may be formed in the same structure as the first power meter 23, and supply the commercial power and the production power P1 from the grid power supply and the power converter 20 to the load 25 of the user. Is installed in the load line 241 to measure the load power (P2) used by the user. Therefore, the fuel cell controller 50 is configured between the production power P1 of the fuel cell 10 measured by the first power meter 23 and the load power P2 of the user measured by the second power meter 24. The power imbalance difference (ΔP = P2-P1) may be compared for a set time or more.

The system 100 of one embodiment is linked to the fuel cell 10 and the system power source (eg, commercial power source), and is selectively operated by the production power P1 and the commercial power source. That is, the system 100 is operated at the commercial power of the system power source at the start of the fuel cell 10, and during the operation of the fuel cell 10 producing electric power, the production power P1 of the fuel cell 10. Is driven.

To this end, the power divider 30 is disposed between the fuel cell 10 and the system power source to supply commercial power to the fuel cell 10. That is, the power divider 30 selectively supplies the commercial power and the production power P1 to other components of the system 100 according to the start-up or operation of the fuel cell 10.

The waste heat recovery 40 includes, for example, a heat storage tank 41, a water pump 42, an air-cooled heat exchanger 43, a three-way valve 44, an auxiliary burner 45, and a temperature sensor 46. The heat storage tank 41 stores the waste heat recovered from the fuel cell 10 through the heat exchanger 14 connected to the fuel cell stack 12 and the fuel processor 11 of the fuel cell 10 in water. When the heat storage tank 41 is filled with heat, the water pump 42 and the air-cooled heat exchanger 43 circulate the water in the heat storage tank 41 to remove the heat contained in the water in the heat storage tank 41. The auxiliary burner 45 replenishes heat to the heat storage tank 41. The temperature sensor 46 measures the temperature of the heat storage tank 41. The heat storage tank 41 has a direct inlet 411 for supplying direct water, a hot water outlet 412 for discharging hot water, a heating water outlet 413 for discharging and supplying heating water, and a heating water recovery port 414 for recovering heating water. It is provided.

The fuel cell controller 50 is electrically connected to the fuel cell 10, the power converter 20, the second power meter 24, the power distributor 30, the waste heat recovery 40, and various components provided therein. Thus, the system 100 is operated and controlled in an optimized state for various situations of the system 100.

The fuel cell controller 50 improves the economics of the system 100 by eliminating the power imbalance difference ΔP = P2-P1 between the production power P1 of the fuel cell 10 and the load power P2 of the user. . In addition, the fuel cell controller 50 allows the commercial power of the system power to be used first in consideration of the fact that the progressive charge system is applied to the commercial power of the system power source.

To this end, the fuel cell controller 50 includes a load follower 51, an economic recognizer 52, an operation controller 53, and a data storage RAM 54. The load follower 51 determines the direction of power production according to the power imbalance difference ΔP = P2-P1 between the production power P1 and the load power P2. The economic recognizer 52 recognizes economic feasibility by comparing the production power price MWP of the fuel cell 10 and the commercial power price WP of the system power source. The operation controller 53 controls the power production step of the fuel cell 10 in multiple stages in response to the rated power generation in consideration of the change in the load power P2, and generates the raw materials according to the production power of the fuel cell 10. Linearly control the flow rate of air and coolant. More specific operational effects of the fuel cell controller 50 will be described together with the control method.

FIG. 2 is a flowchart illustrating a control method of the fuel cell cogeneration system of FIG. 1. Referring to FIG. 2, the control method of the fuel cell cogeneration system according to an embodiment (hereinafter, referred to as a “control method”) includes first and second calculation steps ST10 and ST20, an economic determination step ST30, and a power supply step. (ST40).

The first calculation step ST10 calculates the price of the production power P1 produced by the fuel cell 10, that is, the production power price MWP. That is, the first calculation step ST10 detects the amount of power used (F), the raw material price per unit (FP, price / Nm ³ ), and the amount of power produced (ST11), and calculates the production power price (MWP) from this data. (ST12).

For example, if the fuel cell 10 uses F (Nm ³ ) as the power source to generate P kWh of electricity for 1 hour, and the power source price per unit is FP (R / Nm ³ ), the fuel cell 10 ) MWP is F × FP / P (KRW / kWh).

The second calculation step ST20 calculates the price of the commercial power of the used system power source, that is, the commercial power price WP. That is, in the second calculation step ST20, an unbalance difference calculation step ST21 for calculating the power unbalance difference (ΔP = P2-P1) between the production power P1 and the load power P2 of the fuel cell 10 is performed. A range judging step (ST22) for determining whether the unbalanced difference (△ P) is out of the preset range, and if the power unbalance difference (△ P) is in the preset range, the production power (P1) is reduced and out of the preset range. A power production step ST23 that increases the surface production power P1, an integration step ST24 that integrates (∫ΔP) the commercial power amount of the commercial power supplied by the power imbalance difference (ΔP), and the accumulated commercial power amount. And a calculation step (ST25) for comparing the progressive tariff system with the one to calculate the commercial power price (WP).

In the economic judgment stage (ST30), the production power price (MWP) is compared with the commercial power price (WP) (ST31), and the economic index (EW = MWP-WP) that recognizes the economics of production power is positive (+) or negative. It is determined whether or not it is negative (ST32).

The data storage RAM 54 stores the accumulated commercial power amount ∫ΔP of the grid power used in real time and the commercial power price WP for each progressive section of the grid power as in the example of the progressive charge system. Therefore, the economic recognizer 52 calculates the commercial power price (WP) in real time from the accumulated commercial power amount (∫ΔP) and compares it with the production power price (MWP) of the fuel cell 10, thereby determining the economic index (EW). ) Is transmitted to the operation controller 53.

In the power supply stage (ST40), if the economic index (EW) is positive (+), commercial power is supplied to the load 25 (ST41). If the economic index (EW) is negative, the production power (P1) is loaded. It supplies to 25 (ST42). That is, the amount of economic index (EW) means that the production power price (MWP) of the fuel cell 10 is more expensive than the commercial power price (WP) of the system power supply, thereby supplying the relatively low commercial power to the load 25. In addition, the economic index (EW) negative (-) means that the production power price (MWP) of the fuel cell 10 is cheaper than the commercial power price (WP) of the system power supply, and thus, loads relatively low production power (P1). Supply to (25). This makes the system 100 economical.

3 is a graph comparing the amount of electricity and the price of power of the commercial power of the system power and the production power of the fuel cell. Referring to FIG. 3 as an example, in the second calculation step ST20, the power generation step ST23 includes first to fourth power generation steps ST231, ST232, ST233, and ST234.

For convenience of description, the commercial power amount in which the commercial power price (WP) and the production power price (MWP) coincide at the set value is referred to as the coincidence commercial power amount (Pe). For example, a predetermined time for determining occurrence of the power unbalance difference ΔP is set to 5 to 10 minutes.

In the first power production step ST231, when the amount of commercial power used is in the range of less than Pe / 3, the power unevenness difference ΔP is 3/10 of the rated power generation. do.

In the second power generation step ST232, when the amount of commercial power used is in the range of Pe / 3 or more and less than 2Pe / 3, the production power less than the actual load power so that the power unbalance difference ΔP is 2/10 of the rated power generation ( To produce P1).

In the third power production step (ST 233), if the commercial power used is in the range of 2Pe / 3 or more and less than Pe, the production power (P1) less than the actual load power so that the power unbalance difference (ΔP) is 1/10 of the rated power generation. To produce).

In the fourth power production step ST234, when the amount of commercial power used is in the range of Pe or more, the production power P1 to which the power imbalance difference ΔP is eliminated is produced.

That is, in the power generation step ST23, in controlling the usage of the commercial power, the control is moved to the optimal stage such that the commercial power price WP and the fuel cell production power price MWP are matched to each other. do. Considering the heat production price (HP) produced by the fuel cell (10), the production power price (MWP) can be raised, so that the matched commercial power (Pe) of the grid power supply to the new matched commercial power (Phe) It moves (see FIG. 3). As a result, the system 100 of the exemplary embodiment may have economic efficiency while eliminating the power imbalance difference between the production power P1 of the fuel cell 10 and the load power P2 of the user.

In another example, the power production stage ST23 may include nine stages of rated power generation (for example, 200W, 300W, 400W, 500W, 600W, 700W, in consideration of the load power variation of the user). Divided into 800W, 900W and 1,000W) it is possible to produce the production power (P1) in the fuel cell (10). In the power generation step ST23, when the power unbalance difference ΔP between the predetermined amount of production power and the load power amount is greater than 1/10 of the rated power generation for more than a predetermined time, the power generation step ST23 moves to the next step to produce the production power P1. . At this time, the flow rate of air and cooling water supplied to the power generating material and the fuel cell stack 12 is linearly changed according to the amount of power produced by the fuel cell 10.

In the following description, the amount of commercial power used from a grid power source to which a progressive tariff system (eg, Korea Electric Power Corporation) is applied and the commercial power price by progressive section are described as an example.

Table 1

Commercial power and commercial power price (KRW / kWh)
0 to 100 kWh	55.1
100 to 200 kWh	113.8
From 200 to 300 kWh	168.3
From 300 to 400 kWh	248.6
400 to 500 kWh	366.4
Over 500 kWh	643.9

As shown in Table 1, when producing 4 kWh of production power (P1) using 1Nm ³ of generation raw materials (for example, city gas), assuming the city gas price of 670 won / Nm ³ from 0kWh to 200kWh (MWP = 670 × 200/4 = 33500Won), the commercial power price of the grid power supply (WP = 55.1 × 100 + 113.8 × 100 = 16890Won) is much cheaper. That is, in FIG. 3, the power amount kWh is in the range of 0 to Pe.

As such, the control method of the embodiment can minimize energy costs by using the commercial power of the grid power supply until the monthly commercial power price (WP) and the fuel cell production power price (MWP) coincide with each other. In addition, it allows the use of commercial power within the range of 0.5 × Pe to 0.9Pe in the monthly usage of the grid power.

In addition, the system 100 and the control method of one embodiment may be calculated from the production power price (MWP) calculated from the power generation raw material price, the commercial power price (WP) and renewable energy (for example, wind power, solar light, etc.) of the system power source Compared with the production power price of the, it is possible to use renewable energy, and the application of renewable energy can further improve the economics.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

Claims

A fuel cell for producing direct current power using a fuel gas including hydrogen and air containing oxygen;

A power converter converting the DC power produced by the fuel cell into AC power;

A power divider for selecting a commercial power of a grid power supply and a production power of the fuel cell and distributing them to load power of a load;

A waste heat recovery unit for recovering heat generated from the fuel cell; And

A fuel cell cogeneration system comprising a fuel cell controller for controlling the fuel cell, the power converter, the power divider, and the waste heat recovery unit, and controlling the amount of commercial power so that the commercial power price and the production power price coincide at a set value.
According to claim 1,

The fuel cell controller,

A fuel cell cogeneration system further comprising an economic recognizer that recognizes economic efficiency by comparing the commercial power price and the production power price.
The method of claim 2,

The fuel cell controller,

And a load follower for determining an increase or decrease in the direction of power generation according to an imbalance difference between the production power and the load power.
The method of claim 3, wherein

The fuel cell controller,

A data storage RAM for storing the commercial power amount and the commercial power price calculated in real time by the load follower;

A fuel cell cogeneration system comprising an operation controller for controlling a power generation step in multi-stage corresponding to the rated power generation in consideration of the variation of the load power.
A first calculating step of calculating a production power price of the production power produced by the fuel cell;

A second calculating step of calculating a commercial power price using the commercial power of the grid power supply;

An economic determination step of comparing the production power price with the commercial power price to determine whether an economic index for recognizing economics of production power is positive (+) or negative (-); And

And a power supply for supplying commercial power if the economic index is positive and supplying production power if the economic index is negative.
The method of claim 5,

The first calculation step,

A method of controlling a fuel cell cogeneration system that calculates a production power price from power consumption, raw material price, and power generation.
The method of claim 5,

The second calculation step,

An imbalance difference calculation step of calculating an imbalance difference between the production power and the load power,

A range determination step of determining whether the unbalance difference is out of a preset range,

A power production step of reducing the production power when the imbalance difference falls within a preset value range and increasing the production power when outside the preset value range;

An integration step of integrating the amount of commercial power of the commercial power supplied by the disparity difference, and

And a calculating step of calculating the commercial power price by comparing the accumulated commercial power amount with the progressive charge system.
The method of claim 7, wherein

The power production step,

The amount of commercial power in which the commercial power price and the production power price coincide at a set value is referred to as coincidence commercial power amount (Pe),

The first power production step of producing less than the actual load power so that the power unbalance difference is 3/10 of the rated power generation when the amount of commercial power used is less than Pe / 3,

A second power generation step of producing less than the actual load power so that the power unbalance difference is equal to 2/10 of the rated power generation when the used power amount is in the range of Pe / 3 or more and less than 2Pe / 3,

A third power generation step of producing less than the actual load power so that the power unbalance difference is 1/10 of the rated power generation when the amount of commercial power used is in the range of 2Pe / 3 or more and less than Pe, and

And a fourth power generation step of producing a production power in which a power disparity difference is eliminated when the amount of commercial power used is in the range of Pe or more.