A mixed combustion flexible peak shaving power supply

Abstract

The application discloses a mixed combustion flexible peak-shaving power supply, and relates to the technical field of gas turbine peak-shaving, which comprises a coal-fired power generation boiler, a coal-fired heat and power boiler, a coal-fired heat supply boiler, a load servo system and an electric-thermal conversion device. The electric-thermal conversion device is arranged at the furnace and flue of the coal-fired power generation boiler, the coal-fired heat and power boiler and the coal-fired heat supply boiler respectively to realize mixed combustion. The load servo system is installed on the coal-fired power generation boiler, the coal-fired heat and power boiler and the coal-fired heat supply boiler to make the modified boiler combust coal and electricity in the working process, and the ratio of coal combustion to electricity combustion is adjusted according to the change of electricity and heat load. The peak-shaving is realized according to the downward peak-shaving capacity of the boiler stable combustion load level and the increased system electricity load of electricity combustion when the load is low. The boiler becomes the load of the system when the electric-thermal conversion device works. The application solves the problems of high cost, insufficient capacity, abandoned wind and abandoned light of the traditional flexible peak-shaving.

Description

[0001] This invention is a divisional application entitled “Hybrid Flexible Peak-Shaving Power Supply”, wherein the parent application number is 201810236537.6 and the application date is 2018.03.21. Technical Field

[0002] This invention relates to the field of gas turbine peak shaving technology, and in particular to a hybrid flexible peak shaving power source. Background Technology

[0003] Wind power and photovoltaic (PV) power generation are effective ways to achieve large-scale development and utilization of wind and solar energy. To reduce the consumption of non-renewable energy in the entire power generation system and to reduce corresponding greenhouse gas and pollutant emissions, it is often desirable for the existing power grid to accommodate as much wind and solar power as possible, making full grid connection of wind and solar power a key objective of grid dispatch. However, under normal operating conditions, increasing the capacity of wind and solar power grid connections will cause fluctuations in wind and solar power generation, impacting the power grid and increasing the system's power generation costs.

[0004] For power grids dominated by thermal power units, the main measures to increase the integration of wind and solar power include: increasing the number of flexible dispatchable power sources such as oil-fired units, gas-fired units, and pumped storage hydroelectric power; constructing energy storage facilities; and converting coal-to-electricity heating. These measures all require additional investment. In addition, moderately curtailing wind power to address its anti-peak-shaving characteristics is another measure, but curtailment will result in economic losses. Utilizing hybrid power generation and cogeneration units to mitigate the shortcomings of the above measures is of great significance for improving the wind and solar power absorption capacity of the existing power grid and reducing the overall system's power generation costs. However, measures such as increasing the scale of electricity load, improving wind power forecasting technology, coordinating demand response, constructing inter-regional power grids, and increasing local wind and solar power consumption cannot replace the role of hybrid power generation and cogeneration units in improving the absorption of wind and solar power. Summary of the Invention

[0005] This invention provides a hybrid flexible peak-shaving power source that solves the problems of high cost and insufficient capacity of traditional flexible peak-shaving technologies, as well as the problems of wind and solar power curtailment.

[0006] To achieve the above objectives, this application provides the following solution:

[0007] A hybrid flexible peak-shaving power source includes a coal-fired power generation boiler, a coal-fired thermal power boiler, a coal-fired heating boiler, a load servo system, and an electrothermal conversion device;

[0008] The electrothermal conversion device is installed in the furnace and flue of the coal-fired power generation boiler, the coal-fired thermal power boiler, and the coal-fired heating boiler respectively to achieve co-combustion;

[0009] A load servo system is installed on the coal-fired power generation boiler, the coal-fired cogeneration boiler, and the coal-fired heating boiler so that the modified boilers can burn both coal and electricity during operation, and the ratio of coal to electricity is adjusted according to the changes in electricity and heat loads; and during off-peak hours, peak shaving is achieved based on the boiler's downward peak shaving capacity at the stable combustion load level and the increased system electricity load due to electricity.

[0010] When the electrothermal conversion device is in operation, the boiler becomes the load of the system.

[0011] Optionally, it also includes oil-fired boilers and gas-fired boilers;

[0012] The electrothermal conversion device is installed in the furnace and flue of the oil-fired boiler and the gas-fired boiler, respectively, to achieve co-combustion.

[0013] Optionally, during work,

[0014] A certain independent power grid is not connected to wind and solar power, and also lacks traditional flexible peak-shaving capabilities; the system is in a state of power generation and load balance. If wind and solar power (P) are connected, the power output will be... WG And P WG <P Gmax If the mixed combustion mode is activated, the sum of the fuel-electric power consumption P of multiple mixed combustion units will be used. WG The power output of the fuel cell is αP WG At the same time, coal-fired power output decreased by αP WG This ensures that the total output of the combined-fuel generator units remains constant, maintaining a balance between power generation and electricity demand; α is the fuel-electric efficiency, α < 1; P Gmax This indicates the maximum power generation load of the hybrid power unit;

[0015] If the wind and solar power grid connection power is reduced to P WG If -ΔP, then the power consumption of electricity will decrease by ΔP, and the power consumption of coal will increase by αΔP, so that the system maintains a balance between power generation and power consumption.

[0016] If the system's electrical load increases by ΔP, the combined-fuel unit's power consumption decreases by ΔP, while its coal-fired power increases by αΔP, and the system is in a balance between power generation and power consumption.

[0017] If the system's electrical load increases by ΔP while the system also receives wind and solar power, the power output will be affected by P. WG Increase to P WG +ΔP WG Then the power consumed by the gas-fired generator set will be adjusted to P. WG +ΔP WG -ΔP, while increasing coal-fired power α(ΔP-ΔP) WG The system's power generation and consumption loads are also in a balanced state;

[0018] If the system's electrical load decreases by ΔP, then the sum of the power consumption of each mixed-use unit increases by ΔP, while the sum of the power consumption of each mixed-use unit decreases by αΔP, and the system still maintains a balance between power generation and electrical load.

[0019] If the system's electrical load decreases by ΔP M The increase is relatively large, resulting in a rise in the system's fuel and electricity consumption power by ΔP. M Then, each unit in the system meets the boiler stable combustion load P. iMin Constraint: The sum of the reductions in coal-fired power output of each mixed-use unit is αΔP M And each unit P iMin The sum of > P WG The system still maintains a balance between power generation and power consumption load;

[0020] If the system's electrical load reaches a low point and then rises by ΔP, the sum of the power consumption of each mixed-use unit will decrease by ΔP, while the power consumption of coal will increase by αΔP, thus satisfying the balance between the system's power generation and electrical load.

[0021] Optionally, during work,

[0022] If a co-fired thermal power unit or co-fired boiler is used for heating in the heating network, the co-fired thermal power unit and co-fired boiler will generate electricity as much as possible during the off-peak hours of the system's electricity load. As a result, the system's electricity load increases, the degree of constraint on the load increase rate of the relevant boilers is reduced, and the system's ability to absorb wind power is enhanced.

[0023] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0024] This invention discloses a flexible peak-shaving power source for co-firing. Electrothermal conversion devices are installed in the furnace and flue of existing coal-fired power generation boilers, coal-fired combined heat and power boilers, and coal-fired heating boilers to achieve co-firing, transforming them into co-firing boilers. A load servo system is installed on the coal-fired boiler, enabling the modified boiler to burn both coal and electricity during operation, with the coal-to-electricity ratio adjusted according to changes in electricity and heat loads. During off-peak hours, peak shaving is achieved based on the boiler's downward peak-shaving capacity at its stable combustion load level and the increased system electricity load from electricity generation. This allows for corresponding adjustments to coal and electricity power output for different situations such as wind power integration, solar power integration, and varying electricity loads, achieving a balance between power generation and electricity load. This invention, by implementing co-firing retrofits for large coal-consuming systems such as heating networks, not only increases the scale of electricity load but also mitigates losses caused by wind curtailment.

[0025] This invention belongs to the technical fields of new energy, fossil energy conservation, greenhouse gas emission reduction, power systems, and boilers. It involves retrofitting existing coal-fired power plants and cogeneration units with co-firing technology. Co-firing enables the adjustment of system load, thereby addressing the randomness, instability, and anti-peak-shaving characteristics of wind and solar power. It increases the proportion of wind and solar power by using marginal cost to approach marginal revenue. This is far more cost-effective than investing in traditional flexible peak-shaving power sources such as pumped storage, oil and gas-fired power plants, energy storage facilities, or electric boilers to increase the proportion of wind and solar power. Clearly, incorporating the heating network into the system further enhances the suppression of wind curtailment. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In this invention, "fuel-to-electricity" specifically refers to the conversion of electrical energy into thermal energy, and "co-combustion" specifically refers to the conversion of fossil fuels into thermal energy simultaneously with fuel-to-electricity conversion. To date, coal-fired power plants and combined heat and power units convert the chemical energy of fossil fuels into the thermal energy of steam within their boilers.

[0028] This invention relates to a co-fired boiler for power generation and cogeneration units. The increase or decrease of coal-fired power generation can adjust the system's electrical load, while the increase or decrease of coal-fired power generation can adjust the system's power generation load. This enables the system to form a flexible peak-shaving capability, thereby balancing the impact of fluctuations in wind power and solar power on the system. Increasing the flexible peak-shaving capacity is crucial for improving the absorption capacity of wind power and solar power. If the heating boilers in the heating network are also modified to co-fired power generation, the wind curtailment caused by the reverse peak-shaving characteristics of wind power will be effectively alleviated.

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0030] 1. Existing coal-fired power generation boilers, coal-fired combined heat and power boilers, and coal-fired heating boilers should be modified to become co-fired boilers. Similar modifications can be implemented for oil-fired and gas-fired boilers. Electrothermal conversion devices should be installed in the furnace, flue, and other parts of the power generation, combined heat and power, and heating network boilers to improve combustion efficiency and normal boiler operation, enabling co-fired combustion. However, co-fired combustion between different types of coal, coal and oil, and coal and gas are chemical energy mixtures, and in these cases, the boiler should not become a load on the system.

[0031] Coal combustion involves blowing in fine coal particles, which then boil and burn. Switching from coal to electricity involves reducing the amount of coal powder introduced while increasing the power consumption for electricity. Conversely, electricity combustion raises the furnace temperature significantly higher than the ignition point of coal; switching back to coal combustion involves reducing power consumption for electricity while correspondingly increasing the amount of coal powder introduced. During these conversions, it is crucial to maintain the normal operation of equipment such as the boiler water-cooled walls, superheater, reheater, steam drum, economizer, and air preheater.

[0032] Gas-fired power generation involves converting electrical energy into heat energy, which is then converted back into electrical energy through a steam turbine and generator. This conversion from electrical energy to electrical energy results in an efficiency loss. Is it worthwhile? This small percentage of efficiency loss can overcome the randomness and volatility of wind and solar power, alleviate wind and solar curtailment, and increase the proportion of wind and solar power.

[0033] The modified boiler can burn both coal and electricity, and the ratio of coal to electricity can be adjusted to follow changes in electricity and heat loads. When the electrothermal conversion device is working, the boiler becomes the load of the system. In order to make the ratio of coal to electricity follow changes in electricity and heat loads, the boiler also needs to be equipped with a corresponding load servo system, and the time scale of following the load also needs to be gradually refined accordingly.

[0034] The peak-shaving capacity of a mixed-fuel unit during off-peak hours is calculated bidirectionally. One part is the downward peak-shaving capacity based on the boiler's stable combustion load level, and the other part is the increased system electrical load from the coal-fired power plant. Peak shaving can be achieved simply by switching between coal and electricity, but this peak shaving is not constrained by the rate of load increase or decrease. In other words, units converted to mixed-fuel operation are truly flexible peak-shaving power sources.

[0035] Pumped storage power stations can also pump water and store energy during peak wind power output to achieve flexible peak shaving, but they require a large initial investment. Gas-fired and oil-fired units also have similar drawbacks. If electric boilers and other similar units cannot be co-fired, heating will further amplify the peak electricity load during peak system electricity demand.

[0036] 2. For situations where wind power and solar power have different access capacities and different power loads, implement corresponding power conversion between coal and electricity to achieve a balance between power generation and power load. At the same time, carry out co-firing transformation for major coal consumers such as heating networks. This will not only increase the scale of the system's power load, but also alleviate the losses caused by wind curtailment.

[0037] Assumption 1: A certain independent power grid is not connected to wind or solar power and lacks traditional flexible peak-shaving capabilities. The system is in a state of power generation and load balance, and the power consumption load remains constant. This power grid contains some mixed-use turbine units, and the sum of their maximum power generation loads is P. Gmax If wind power and solar power P are connected... WG And P WG <P GmaxIn this situation, the mixed-fuel generator sets start in mixed-fuel mode, and the sum of the power consumption P of multiple mixed-fuel generator sets... WG The power generation capacity of gas-fired power is αP WG (α is the combustion efficiency, α < 1), while the coal-fired power output decreases by αP. WG This ensures that the total output of the combined-use turbine units remains constant, maintaining a balance between power generation and electricity load. As a result, gas-fired power replaces coal-fired power, unaffected by load fluctuation rates. Therefore, an increase in gas-fired power output is equivalent to both an increase in system electricity load and a corresponding increase in system power generation load; similarly, a decrease in gas-fired power output is equivalent to both a decrease in system electricity load and a corresponding decrease in system power generation load. If the wind and solar power input is reduced to P... WG If the power output of the gas-fired power plant decreases by ΔP and the power output of the coal-fired power plant increases by αΔP, the system will still maintain a balance between power generation and power consumption. In this case, the conversion between the power output of the gas-fired power plant and the power output of the coal-fired power plant is essentially a way to address the instability of wind power and solar power, and to realize the system's flexible peak-shaving capability.

[0038] Assumption 2: A certain independent power grid is connected to wind power and photovoltaic power P. WG The system still lacks traditional flexible peak-shaving capabilities, and the sum of the power consumption P of multiple hybrid turbine units in the system is... WG The system is currently in a state of power generation and load balance. If the system's power load increases by ΔP, the combined-fuel turbine's power consumption decreases by ΔP, while its coal-fired power consumption increases by αΔP. The system remains in power generation and load balance, and the increase or decrease in coal-fired power consumption acts as a backup power source, unaffected by load fluctuation rates. If the system's power load increases by ΔP simultaneously with the connection of wind and solar power, the power consumption will be reduced by P. WG Increase to P WG +ΔP WG At this point, it is only necessary to adjust the power consumption of the hybrid power unit to P. WG +ΔP WG -ΔP, while increasing coal-fired power α(ΔP-ΔP) WG The system's power generation and consumption loads are also in a balanced state and are not constrained by the rate of load increase or decrease.

[0039] Assumption 3: A certain independent power grid is connected to wind power and solar power P. WG The system lacks traditional flexible peak-shaving capabilities. The sum of the fuel and electricity consumption power of the mixed-use units in the system, P WG The power grid is in a state of balance between power generation and power consumption. If the system's power consumption decreases by ΔP, the sum of the power consumption of each mixed-use turbine unit increases by ΔP, while the sum of the power consumption of each mixed-use turbine unit decreases by αΔP. The system still maintains a balance between power generation and power consumption. M The system's power generation load decreases by ΔP significantly. MAt this point, as long as each unit in the system meets the boiler stable combustion load P iMin Constraint: The sum of the reductions in coal-fired power output of each mixed-use unit is αΔP M And each unit P iMin The sum of > P WG The system still maintains a balance between power generation and consumption load, but the stable combustion load P of the co-fired boiler... iMin This is no longer the stable combustion load of a coal-fired boiler, and it has a stronger downward peak-shaving capability. If the system's electrical load reaches a certain low point and then rises by ΔP, the sum of the power consumption of each mixed-use unit decreases by ΔP, while the coal-fired power increases by αΔP, which can satisfy the system's power generation and load balance. At this time, if the boiler's output load increases or decreases, the load increase / decrease rate constraints of each boiler must be met.

[0040] If a co-fired thermal power unit or co-fired boiler is used for heating in the heating network, the co-fired thermal power unit and co-fired boiler will generate electricity as much as possible during the off-peak hours of the system's electricity load. As a result, the system's electricity load increases, the degree of constraint on the load increase rate of the relevant boilers is reduced, and the system's ability to absorb wind power is enhanced.

[0041] 3. Determine the installed capacity of wind power and solar power in the power grid based on the boundary that marginal cost equals marginal revenue.

[0042] (1) Principles for determining wind and solar power installed capacity. The increase in revenue from adding one unit of wind and solar power installed capacity to an independent power grid is called the marginal revenue (MB) of the increased installed capacity, where MB = ΔB / ΔG, ΔG is the newly added wind and solar power installed capacity, and ΔB is the revenue increased by the newly added ΔG. The increase in cost from adding one unit of wind and solar power installed capacity to an independent power grid is called the marginal cost (MC) of the increased installed capacity, where MC = ΔC / ΔG, ΔG is the newly added wind and solar power installed capacity, and ΔC is the cost increased by the newly added ΔG. When the marginal revenue equals the marginal cost (MB = MC), the power grid's efficiency is highest, thus determining the wind and solar power installed capacity of the power grid. Currently, the cost of wind and solar power is decreasing rapidly, while the cost of environmental load is increasing significantly, which is conducive to increasing the proportion of wind and solar power installed capacity.

[0043] (2) Data Acquisition

[0044] The following parameters were obtained: operating technical parameters of thermal power units (minimum output, rated output, coal consumption rate, and equivalent CO2 emission coefficient per unit of standard coal during peak shaving and deep peak shaving); energy price parameters (wind power, solar power costs, coal price, diesel price, and CO2 emission permit price); and system operating data (load level, wind power output, self-characteristics of wind and solar power, output of each thermal power unit, and number of thermal power units). Various parameters of the co-fired power unit were obtained through experiments.

[0045] Compared with the prior art, the present invention also has the following advantages:

[0046] 1. This invention incorporates an electrothermal conversion device in the furnace and flue of coal-fired power generation boilers, coal-fired thermal power boilers, and coal-fired heating boilers to achieve co-combustion, thereby transforming these boilers into flexible peak-shaving power sources. This will create conditions for increasing the percentage of wind and solar power in the regional power grid. This invention is key to increasing the proportion of wind and solar power.

[0047] 2. Traditional flexible peak-shaving power sources include pumped hydro storage, oil-fired power generation, and gas-fired power generation. The cost of a hybrid flexible peak-shaving power source converted from a coal-fired boiler is significantly lower than that of a newly built traditional flexible peak-shaving power source, energy storage facilities, or electric boiler.

[0048] 3. Since the flexible peak-shaving power supply of mixed combustion can adjust the power load of the system, it can also include the energy consumption of the heating network, including the mixed combustion boiler, into the power load of the system, which can effectively alleviate the problem of wind curtailment.

[0049] 4. Hybrid flexible peak-shaving power sources can integrate thermal power, wind power, photovoltaic power, and heating networks into one, reducing the differences between different stakeholders and facilitating cooperation among them.

[0050] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0051] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A hybrid flexible peak-shaving power supply, characterized in that, This includes coal-fired power generation boilers, coal-fired combined heat and power boilers, coal-fired heating boilers, load servo systems, and electrothermal conversion devices; The electrothermal conversion device is installed in the furnace and flue of the coal-fired power generation boiler, the coal-fired thermal power boiler, and the coal-fired heating boiler respectively to achieve co-combustion; A load servo system is installed on the coal-fired power generation boiler, the coal-fired cogeneration boiler, and the coal-fired heating boiler so that the modified boilers can burn both coal and electricity during operation, and the ratio of coal to electricity is adjusted according to the changes in electricity and heat loads; and during off-peak hours, peak shaving is achieved based on the boiler's downward peak shaving capacity at the stable combustion load level and the increased system electricity load due to electricity. When the electrothermal conversion device is working, the boiler becomes the load of the system; During operation, a certain independent power grid is not connected to wind and solar power, and lacks traditional flexible peak-shaving capabilities; the system is in a state of power generation and load balance. If wind and solar power (P) are connected... WG And P WG <P Gmax If the mixed combustion mode is activated, the sum of the fuel-electric power consumption P of multiple mixed combustion units will be used. WG The power output of the fuel cell is P WG At the same time, coal-fired power output decreased P WG This ensures that the total output of the combined-fuel generator units remains constant, maintaining a balance between power generation and electricity consumption. For fuel efficiency, <1; P Gmax This indicates the maximum power generation load of the hybrid power unit; If the wind and solar power grid connection power is reduced to P WG - P, then the power consumption of gas-fired power plants will be further reduced. P, coal-fired power further increased to P ensures that the system maintains a balance between power generation and power consumption loads. If the system's electrical load increases P, then the power consumption of the combined combustion unit is reduced. P, while increasing coal-fired power. P, the system is in a state of power generation and power consumption load balance; If the system's electrical load increases At the same time as P, the system connects to wind power and photovoltaic power, which is generated by P. WG Increase to P WG + P WG Then the power consumed by the gas-fired generator set will be adjusted to P. WG + P WG - P, while increasing coal-fired power. ( P- P WG The system's power generation and consumption loads are also in a balanced state; If the system's electrical load decreases P then increases the sum of the fuel and electricity consumption of each hybrid unit. P, at the same time, the sum of the coal-fired power outputs of each mixed-use unit is reduced. P, the system still maintains a balance between power generation and power consumption load; If the system's electrical load decreases P M The power consumption of the system is relatively large, resulting in an increase in fuel and electricity consumption. P M Then, each unit in the system meets the boiler stable combustion load P. iMin Constraints, the sum of the reductions in coal-fired power output of each mixed-use unit P M And each unit P iMin The sum of > P WG The system still maintains a balance between power generation and power consumption load; If the system's electrical load reaches a low point and then rises... P represents the sum of the reductions in power consumption of each hybrid turbine unit. P, while coal-fired power increases P satisfies the system's power generation and consumption load balance.

2. The hybrid flexible peak-shaving power supply according to claim 1, characterized in that, This also includes oil-fired boilers and gas-fired boilers; The electrothermal conversion device is installed in the furnace and flue of the oil-fired boiler and the gas-fired boiler, respectively, to achieve co-combustion.

3. The hybrid flexible peak-shaving power supply according to claim 1, characterized in that, At work, If a co-fired thermal power unit or co-fired boiler is used for heating in the heating network, the co-fired thermal power unit and co-fired boiler will generate electricity as much as possible during the off-peak hours of the system's electricity load. As a result, the system's electricity load increases, the degree of constraint on the load increase rate of the relevant boilers is reduced, and the system's ability to absorb wind power is enhanced.

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