CN110738393A - Method and system for evaluating power generation benefits of natural gas of comprehensive energy systems - Google Patents

Method and system for evaluating power generation benefits of natural gas of comprehensive energy systems Download PDF

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CN110738393A
CN110738393A CN201910869411.7A CN201910869411A CN110738393A CN 110738393 A CN110738393 A CN 110738393A CN 201910869411 A CN201910869411 A CN 201910869411A CN 110738393 A CN110738393 A CN 110738393A
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任核权
胡宇晴
张坤
莫俊雄
徐恩
张丙垒
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SHAOXING DAMING ELECTRIC POWER DESIGN INSTITUTE Co Ltd
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Abstract

The invention provides an comprehensive energy system natural gas power generation benefit evaluation method which comprises the steps of obtaining financial related data of a system, calculating financial evaluation indexes according to the financial related data, evaluating the profit capacity of natural gas power generation by using the calculated financial evaluation indexes, obtaining operation related data of the system, calculating system benefit indexes according to the operation related data, evaluating benefits of a natural gas power generation unit on an electric power system by using the calculated system benefit indexes, obtaining environment related data of the system, calculating environment benefit indexes according to the environment related data, and evaluating benefits of the natural gas power generation system on environment protection by using the calculated environment benefit indexes.

Description

Method and system for evaluating power generation benefits of natural gas of comprehensive energy systems
Technical Field
The invention relates to the field of power generation benefit evaluation, in particular to a power generation benefit evaluation method and system for natural gas of comprehensive energy systems.
Background
The traditional benefit evaluation method for the natural gas power plant of the comprehensive energy system mainly comprises power plant economy evaluation and reliability evaluation. Wherein traditional power plant economic assessments focus on financial economic analysis of the power plant; in the traditional power grid reliability evaluation, forced outage rates of power plants need to be considered, and Probability indexes represented by LOLP (Loss of Load Probability) are mainly calculated. However, unlike other types of power plants, natural gas power plants generate electricity in power systems with characteristics of cleanliness, environmental friendliness, rapid start and stop, and flexible operation. The traditional power plant economic assessment method and the traditional power grid reliability assessment method do not deeply consider the operation mode and the environmental factors of the natural gas power generating set, so that the characteristics of natural gas power generation cannot be well reflected by the traditional economic assessment method and the traditional reliability assessment method, and the guiding significance of the traditional economic assessment method and the traditional reliability assessment method on the evaluation of the natural gas power generation benefits of the comprehensive energy system is not great.
Disclosure of Invention
The invention aims to solve the technical problem that natural gas power generation benefit evaluation methods and systems for an integrated energy system are provided, and the problems that the characteristics of natural gas power generation cannot be well reflected by the traditional economic efficiency evaluation method and the traditional reliability evaluation method, and the guiding significance of the traditional economic efficiency evaluation method and the traditional reliability evaluation method on natural gas power generation benefit evaluation for the integrated energy system is not large are solved.
The invention is realized in the way that the natural gas power generation benefit evaluation method of comprehensive energy systems comprises the following steps in no sequence:
step S1, acquiring financial related data of the system, calculating a financial evaluation index according to the financial related data, and evaluating the profitability of natural gas power generation by using the calculated financial evaluation index; the financial evaluation indexes at least comprise net present value, internal rate of return and investment recovery period;
s2, obtaining operation related data of the system, calculating a system benefit index according to the operation related data, and evaluating the benefit of the operation mode of the natural gas generator set on the power system by using the calculated system benefit index; the system benefit index at least comprises capacity benefit, fuel benefit, peak shaving benefit and reliability benefit;
s3, acquiring environment-related data of the system, calculating an environment benefit index according to the environment-related data, and evaluating the benefit of the natural gas power generation system on environmental protection by using the calculated environment benefit index; the environmental benefit indicators include at least pollutant emissions and environmental costs.
Further , in the step S1, the calculation formula of the net present value is as follows (1):
Figure BDA0002202304130000021
wherein NPV represents the net present value; t denotes cash flow occurred in the t year; CI represents the cash inflow for the year; CO represents cash out for the year; i represents a discount rate; n represents a survey period;
the internal rate of return is calculated as follows:
the internal yield is the discount rate when the current value accumulation of the net cash flow of each year is equal to 0 in the construction and production operation years of the investment project, and the calculation formula is as follows (2):
Figure BDA0002202304130000022
the IRR is solved approximately using interpolation, the calculation formula is as follows (3):
Figure BDA0002202304130000023
wherein IRR represents an internal rate of return; i.e. i1、i2Respectively representing the lowest and highest discount rates obtained by trial calculation; NPV (i)1)、NPV(i2) Respectively represent a discount rate of i1、i2Net present value of time;
the return on investment period is calculated as follows:
the investment recovery period is the time required for the net income recovery project investment of the investment project, and the calculation formula is as follows (4):
the method comprises the following steps of (1) obtaining an investment recovery period by using accumulated net cash flow in a financial cash flow table, wherein a calculation formula is as follows:
Figure BDA0002202304130000025
wherein, PtRepresenting an investment recovery period; n ispThe year that the cumulative net cash flow begins to appear positive;
Figure BDA0002202304130000033
represents the absolute value of the cumulative net cash flow of the last year;
Figure BDA0002202304130000034
representing the net cash flow in the year.
Further , in the step S2, the calculation formula of the capacity benefit is as follows (6):
Bcapacity＝(IT-IES)+(CT-CES) (6)
wherein, BcapacityRepresenting the capacity benefit of the natural gas power plant; i isTRepresents the investment cost of other types of power plants; i isESRepresents the investment cost of the gas power plant; cTRepresents a fixed operating cost for other types of power plants; cESRepresents a fixed operating cost of the gas power plant;
the fuel efficiency is calculated as follows:
the fuel benefit is represented by the reduction of the average coal consumption rate and the average gas consumption rate, and the calculation formulas of the average coal consumption rate and the average gas consumption rate are respectively as shown in formula (7) and formula (8):
Figure BDA0002202304130000031
wherein, Cave-coalRepresenting the average coal consumption rate of the system; cave-gasRepresents the average gas consumption rate of the system; ccoalAnd CgasRepresenting the total coal and gas consumption in the system; pcoalAnd PgasRespectively representing the total output of all coal-electric units and the total output of all gas-electric units in the system;
after the average coal consumption rate and the average gas consumption rate of the system are obtained, the fuel benefit calculation formula of the natural gas power plant is as shown in the formula (9) and the formula (10):
Bcoal-saving＝Cave-coal-C'ave-coal(9)
Bgas-saving＝Cave-gas-C'ave-gas(10)
wherein, Bcoal-savingAnd Bgas-savingRespectively showing the coal saving benefit and the gas saving benefit of the natural gas power plant; cave-coalAnd Cave-gasRespectively representing the average coal consumption rate and the average gas consumption rate of the actual system; c'ave-coalAnd C'ave-gasRespectively representing the average coal consumption rate and the average gas consumption rate of the replacement system;
the calculation formula of the peak shaving benefit is as follows (11):
Bpeak-shaving＝Ftotal-F'total(11)
wherein, Bpeak-shavingThe peak shaving benefit of the natural gas power plant is shown; ftotalRepresenting the fuel cost and start-stop cost of the actual system; f'totalRepresenting fuel costs and start-stop costs of the replacement system;
the reliability benefit is measured by a system power shortage time expected value LOLE and a power shortage expected value EENS;
in a certain time period, the probability that the outage capacity of the unit is equal to or greater than the reserve capacity is the expected value of the power shortage time of the system, and the calculation formula is as follows (12):
Figure BDA0002202304130000041
wherein L isjRepresents daily spike load on day j; n represents the number of days during the study; csIndicating the installed capacity of the system in the time period; p [ X is more than or equal to Cs-Lj]Representing the probability that the outage capacity is more than or equal to the spare capacity on the j th day in the time period; x represents the outage capacity;
the calculation formula of the annual load power failure time expectation value is as follows (13):
Figure BDA0002202304130000042
wherein m represents the number of study sessions in years, i represents the number of days in the ith session, and LijRepresents the peak load at day j within the ith time period; ciIndicating the installed capacity of the system in the ith time slot,
Figure BDA0002202304130000044
representing the probability that the outage capacity of the jth day is more than or equal to the spare capacity in the ith time period;
the expected electric power shortage EENS is an expected electric power shortage caused by the fact that the capacity of a generator set provided by the power system is smaller than the load demand capacity, and for a certain known outage capacity, the expected electric power shortage EENS is equal to the probability that the insufficient capacity is multiplied by the outage capacity, and the calculation formula is as shown in the formula (14):
EENS＝(X-R)×P(X) (14)
wherein R represents the spare capacity of the system;
the expected value of the electricity shortage in years is calculated according to the formula (15):
wherein, Pijk(X) represents the probability that the k-th hour outage capacity of the j day in the i-th time period is equal to or greater than X, m represents the number of time periods in years, njTo representDays in the j-th time period, LijkRepresents the hour load of the kth hour on the jth day during the ith time period.
, in the step S3, the calculation of the pollutant discharge amount includes calculating the pollutant discharge amount of the three power plants, namely a conventional coal-fired power plant, a coal-fired power plant with a desulfurizer and a natural gas power plant during operation respectively;
the calculation of the environmental cost includes: and (4) according to a pollution discharge charging system, calculating the total pollution discharge charging of the power plant and the compensation degree for pollutant loss to obtain the total environmental cost.
The invention is realized by the following steps that natural gas power generation benefit evaluation systems of the comprehensive energy system comprise a financial index evaluation module, a system benefit evaluation module and an environmental benefit evaluation module;
the financial index evaluation module is used for acquiring financial related data of the system, calculating a financial evaluation index according to the financial related data, and evaluating the profit capacity of the natural gas power generation by using the calculated financial evaluation index; the financial evaluation indexes at least comprise net present value, internal rate of return and investment recovery period;
the system benefit evaluation module is used for acquiring operation related data of the system, calculating a system benefit index according to the operation related data, and evaluating the benefit of the operation mode of the natural gas generator set on the power system by using the calculated system benefit index; the system benefit index at least comprises capacity benefit, fuel benefit, peak shaving benefit and reliability benefit;
the environmental benefit evaluation module is used for acquiring environmental related data of the system, calculating an environmental benefit index according to the environmental related data, and evaluating the benefit of the natural gas power generation system on environmental protection by using the calculated environmental benefit index; the environmental benefit indicators include at least pollutant emissions and environmental costs.
Further , in the financial index evaluation module, the calculation formula of the net present value is as follows:
wherein NPV represents the net present value; t denotes cash flow occurred in the t year; CI represents the cash inflow for the year; CO represents cash out for the year; i represents a discount rate; n represents a survey period;
the internal rate of return is calculated as follows:
the internal yield is the discount rate when the current value accumulation of the net cash flow of each year is equal to 0 in the construction and production operation years of the investment project, and the calculation formula is as follows (2):
Figure BDA0002202304130000052
the IRR is solved approximately using interpolation, the calculation formula is as follows (3):
Figure BDA0002202304130000053
wherein IRR represents an internal rate of return; i.e. i1、i2Respectively representing the lowest and highest discount rates obtained by trial calculation; NPV (i)1)、NPV(i2) Respectively represent a discount rate of i1、i2Net present value of time;
the return on investment period is calculated as follows:
the investment recovery period is the time required for the net income recovery project investment of the investment project, and the calculation formula is as follows (4):
Figure BDA0002202304130000061
the method comprises the following steps of (1) obtaining an investment recovery period by using accumulated net cash flow in a financial cash flow table, wherein a calculation formula is as follows:
Figure BDA0002202304130000062
wherein, PtIndicating the recovery period of investment；npThe year that the cumulative net cash flow begins to appear positive;
Figure BDA0002202304130000063
represents the absolute value of the cumulative net cash flow of the last year;
Figure BDA0002202304130000064
representing the net cash flow in the year.
, in the system benefit evaluation module, the calculation formula of the capacity benefit is as follows:
Bcapacity＝(IT-IES)+(CT-CES) (6)
wherein, BcapacityRepresenting the capacity benefit of the natural gas power plant; i isTRepresents the investment cost of other types of power plants; i isESRepresents the investment cost of the gas power plant; cTRepresents a fixed operating cost for other types of power plants; cESRepresents a fixed operating cost of the gas power plant;
the fuel efficiency is calculated as follows:
the fuel benefit is represented by the reduction of the average coal consumption rate and the average gas consumption rate, and the calculation formulas of the average coal consumption rate and the average gas consumption rate are respectively as shown in formula (7) and formula (8):
Figure BDA0002202304130000065
Figure BDA0002202304130000066
wherein, Cave-coalRepresenting the average coal consumption rate of the system; cave-gasRepresents the average gas consumption rate of the system; ccoalAnd CgasRepresenting the total coal and gas consumption in the system; pcoalAnd PgasRespectively representing the total output of all coal-electric units and the total output of all gas-electric units in the system;
after the average coal consumption rate and the average gas consumption rate of the system are obtained, the fuel benefit calculation formula of the natural gas power plant is as shown in the formula (9) and the formula (10):
Bcoal-saving＝Cave-coal-C'ave-coal(9)
Bgas-saving＝Cave-gas-C'ave-gas(10)
wherein, Bcoal-savingAnd Bgas-savingRespectively showing the coal saving benefit and the gas saving benefit of the natural gas power plant; cave-coalAnd Cave-gasRespectively representing the average coal consumption rate and the average gas consumption rate of the actual system; c'ave-coalAnd C'ave-gasRespectively representing the average coal consumption rate and the average gas consumption rate of the replacement system;
the calculation formula of the peak shaving benefit is as follows (11):
Bpeak-shaving＝Ftotal-F'total(11)
wherein, Bpeak-shavingThe peak shaving benefit of the natural gas power plant is shown; ftotalRepresenting the fuel cost and start-stop cost of the actual system; f'totalRepresenting fuel costs and start-stop costs of the replacement system;
the reliability benefit is measured by a system power shortage time expected value LOLE and a power shortage expected value EENS;
in a certain time period, the probability that the outage capacity of the unit is equal to or greater than the reserve capacity is the expected value of the power shortage time of the system, and the calculation formula is as follows (12):
wherein L isjRepresents daily spike load on day j; n represents the number of days during the study; csIndicating the installed capacity of the system in the time period; p [ X is more than or equal to Cs-Lj]Representing the probability that the outage capacity is more than or equal to the spare capacity on the j th day in the time period; x represents the outage capacity;
the calculation formula of the annual load power failure time expectation value is as follows (13):
Figure BDA0002202304130000072
wherein m represents the number of study sessions in years, i represents the number of days in the ith session, and LijRepresents the peak load at day j within the ith time period; ciRepresents the installed capacity of the system in the ith time slot, Pi[X≥Ci-Lij]Representing the probability that the outage capacity of the jth day is more than or equal to the spare capacity in the ith time period;
the expected electric power shortage EENS is an expected electric power shortage caused by the fact that the capacity of a generator set provided by the power system is smaller than the load demand capacity, and for a certain known outage capacity, the expected electric power shortage EENS is equal to the probability that the insufficient capacity is multiplied by the outage capacity, and the calculation formula is as shown in the formula (14):
EENS＝(X-R)×P(X) (14)
wherein R represents the spare capacity of the system;
the expected value of the electricity shortage in years is calculated according to the formula (15):
Figure BDA0002202304130000081
wherein, Pijk(X) represents the probability that the k-th hour outage capacity of the j day in the i-th time period is equal to or greater than X, m represents the number of time periods in years, njDenotes the number of days in the j-th time period, LijkRepresents the hour load of the kth hour on the jth day during the ith time period.
, in the environmental benefit evaluation module, the calculation of the pollutant discharge amount includes calculating the pollutant discharge amount of three types of power plants, namely a conventional coal-fired power plant, a coal-fired power plant with a desulphurization device and a natural gas power plant in the operation process respectively;
the calculation of the environmental cost includes: and (4) according to a pollution discharge charging system, calculating the total pollution discharge charging of the power plant and the compensation degree for pollutant loss to obtain the total environmental cost.
The invention has the advantages that the comprehensive evaluation is carried out on the natural gas power generation benefit of the comprehensive energy system by adopting three parts of financial evaluation index, system benefit index and environmental benefit index, wherein the financial evaluation index reflects the profitability of natural gas power generation, including financial net present value, internal profitability and investment recovery period, the system benefit index reflects the benefits of the operation mode of the natural gas power generator set on the power system, including capacity benefit, fuel benefit, peak regulation benefit and reliability benefit, and the environmental benefit index reflects the benefits of natural gas as clean and environment-friendly fossil energy sources and environmental protection, including pollutant discharge amount and environmental cost.
Detailed Description
The invention discloses a preferred embodiment of an comprehensive energy system natural gas power generation benefit evaluation method, which comprises the following steps in no sequence:
step S1, acquiring financial related data of the system, calculating a financial evaluation index according to the financial related data, and evaluating the profitability of natural gas power generation by using the calculated financial evaluation index; the financial evaluation indexes at least comprise net present value, internal rate of return and investment recovery period;
s2, obtaining operation related data of the system, calculating a system benefit index according to the operation related data, and evaluating the benefit of the operation mode of the natural gas generator set on the power system by using the calculated system benefit index; the system benefit index at least comprises capacity benefit, fuel benefit, peak shaving benefit and reliability benefit;
s3, acquiring environment-related data of the system, calculating an environment benefit index according to the environment-related data, and evaluating the benefit of the natural gas power generation system on environmental protection by using the calculated environment benefit index; the environmental benefit indicators include at least pollutant emissions and environmental costs.
According to the technical scheme, -grade indexes for evaluation comprise three parts, namely a financial evaluation index, a system benefit index and an environmental benefit index, the secondary indexes are subdivision and deepening of -grade indexes, the financial evaluation index reflects the profitability of natural gas power generation and comprises a financial net present value, an internal profitability and an investment recovery period, the system benefit index reflects benefits of an operation mode of a natural gas generator set on an electric power system and comprises capacity benefits, fuel benefits, peak regulation benefits and reliability benefits, and the environmental benefit index reflects natural gas as clean and environment-friendly green fossil energy and has great guiding significance on natural gas power generation evaluation of a comprehensive energy system.
The financial evaluation indexes are rings indispensable in the economic evaluation indexes and are used for measuring the economic level from the financial aspect, specifically, the financial evaluation indexes can be divided into financial evaluation indexes reflecting the profitability and financial evaluation indexes reflecting the debt paying capacity, the financial evaluation indexes reflecting the profitability mainly adopt dynamic cash flow analysis and static financial ratio analysis, the financial profitability of the electric power engineering project can be comprehensively and objectively evaluated, specifically, the financial profitability comprises net present value, internal earning rate, investment recovery period, total investment earning rate, net profit rate of capital fund and the like, the debt paying capacity analysis analyzes and judges the debt paying capacity of the financial main body by calculating indexes such as interest spare rate, debt spare rate, asset liability rate and the like, and the three financial evaluation indexes reflecting the profitability, namely the net present invention mainly considers the net present value, the internal earning rate and the investment recovery period.
In the technical solution of the present invention, in the step S1, the calculation formula of the net present value is as follows:
Figure BDA0002202304130000101
wherein NPV represents net present value, t represents cash flow occurring in the t-th year, CI represents cash inflow of the year, CO represents cash outflow of the year, i represents discount rate, i represents reference discount rate (8% as ) in financial evaluation, and represents social discount rate in national economic evaluation, and n represents investigation period;
the Net Present Value (NPV) represents the sum of generations at a point of time "0" (defined as the beginning of the construction period, i.e., the 0 point of the time axis) when cash inflow and cash outflow at different points in the project plan calculation period are reduced under the condition of interest rates.
The internal rate of return is calculated as follows:
the internal rate of return is the discount rate when the current value accumulation of net cash flow of each year is equal to 0 within the construction and production operation years of the investment project, the internal rate of return is an important dynamic evaluation index reflecting the profitability of the engineering scheme (namely the investment project), and the calculation formula is as follows (2):
Figure BDA0002202304130000102
the IRR is solved approximately using interpolation (i.e., dichotomy), the calculation formula is as in equation (3):
wherein IRR represents an internal rate of return; i.e. i1、i2Respectively representing the lowest and highest discount rates obtained by trial calculation; NPV (i)1)、NPV(i2) Respectively represent a discount rate of i1、i2Net present value of time;
when evaluating with the internal rate of return, it is necessary to judge whether the internal rate of return IRR is larger than the rate of return i set inside the company0If yes, the engineering scheme is determined to be in the channelEconomically feasible; otherwise, the project is deemed to be economically infeasible; and the larger the internal rate of return IRR, the better the solution is considered.
The return on investment period is calculated as follows:
the investment recovery period is the time required by the net income recovery project investment of the investment project, is year as unit, the calculation formula of the investment recovery period from the beginning year of the project is as follows (4):
Figure BDA0002202304130000111
the method comprises the following steps of (1) obtaining an investment recovery period by using accumulated net cash flow in a financial cash flow table, wherein a calculation formula is as follows:
wherein, PtRepresenting an investment recovery period; n ispThe year that the cumulative net cash flow begins to appear positive;
Figure BDA0002202304130000113
represents the absolute value of the cumulative net cash flow of the last year;
Figure BDA0002202304130000114
representing the current year net cash flow;
when the evaluation is performed by using the payback period, the payback period P is requiredtAnd the electric power industry investment benchmark recovery period P0By comparison, and when Pt≤P0Then, the engineering scheme is considered financially feasible; otherwise, the engineering solution is deemed to be financially infeasible.
The natural gas power plant has the advantages of being high in automation degree and few in operating personnel, F-cascade circulation unit power plants with millions of kilowatts have the fixed personnel of about 160 persons and are greatly less than the fixed personnel of conventional thermal power plants, so that the natural gas power plants replace the coal-fired power plants with the same installed capacity in the power system, the installed capacity requirement of the power system on the thermal power plants is reduced, the investment cost of the whole system is reduced, the capacity benefit brought by natural gas power generation is related to the factors of the same size as the installed capacity of the natural gas, the capacity of the replaced scheme, the fixed operation cost and the system investment structure, and the like according to an equivalent replacement principle, the specific size of the capacity brought by natural gas power generation is the same as the construction condition of the natural gas, the capacity of the replaced scheme, the fixed operation cost of the system, the equivalent operation cost of the natural gas power plants is provided as the natural gas power plant capacity replacement scheme, and the natural gas power plant capacity replacement scheme is the equivalent to the natural gas power plant.
In the technical solution of the present invention, in the step S2, the calculation formula of the capacity benefit is as follows:
Bcapacity＝(IT-IES)+(CT-CES) (6)
wherein, BcapacityRepresenting the capacity benefit of the natural gas power plant; i isTRepresents the investment cost of other types of power plants; i isESRepresents the investment cost of the gas power plant; cTRepresents a fixed operating cost for other types of power plants; cESRepresents a fixed operating cost of the gas power plant;
in the evaluation of the capacity benefit, if the value of the capacity benefit is larger, the investment cost and the fixed cost of the natural gas power plant are lower than those of other types of power plants, and the evaluation is more economically advantageous.
The natural gas power plant generates electricity by taking natural gas as fuel, and in a power system mainly based on coal electricity, the addition of the natural gas power plant can improve the overall unit operation efficiency; the operation efficiency is improved mainly because the natural gas unit has higher generating efficiency, the coal-fired unit takes a supercritical 600MW steam turbine generator unit as an example, the generating efficiency is about 40 percent, and the generating efficiency of the conventional coal-fired unit is hardly improved in a breakthrough manner due to the limitation of the circulation and equipment of the conventional coal-fired unit; the natural gas unit, especially the gas-steam combined cycle generating set, combines the gas turbine and the steam turbine according to the principle of heat gradient utilization, and improves the generating efficiency to 52-60 percent, which is far higher than that of the conventional coal-fired unit. The improvement of the power generation efficiency reduces the fuel consumption of the power system in the operation process, so the fuel benefit of the natural gas power generation is the fuel consumption saved for the system operation because the natural gas unit is adopted to generate the power.
The fuel efficiency is calculated as follows:
the fuel benefit is represented by the reduction of the average coal consumption rate and the average gas consumption rate, and the calculation formulas of the average coal consumption rate and the average gas consumption rate are respectively as shown in formula (7) and formula (8):
Figure BDA0002202304130000121
Figure BDA0002202304130000122
wherein, Cave-coalRepresenting the average coal consumption rate of the system; cave-gasRepresents the average gas consumption rate of the system; ccoalAnd CgasRepresenting the total coal and gas consumption in the system; pcoalAnd PgasRespectively representing the total output of all coal-electric units and the total output of all gas-electric units in the system;
after the average coal consumption rate and the average gas consumption rate of the system are obtained, the fuel benefit calculation formula of the natural gas power plant is as shown in the formula (9) and the formula (10):
Bcoal-saving＝Cave-coal-C'ave-coal(9)
Bgas-saving＝Cave-gas-C'ave-gas(10)
wherein, Bcoal-savingAnd Bgas-savingRespectively showing the coal saving benefit and the gas saving benefit of the natural gas power plant; cave-coalAnd Cave-gasRespectively representing the average coal consumption rate and the average gas consumption rate of the actual system; c'ave-coalAnd C'ave-gasRespectively representing the average coal consumption rate and the average gas consumption rate of the replacement system;
when the fuel benefit is used for evaluation, if the fuel benefit is higher, the higher the degree of reduction of the average coal consumption rate and the average gas consumption rate of the system caused by the participation of the natural gas power plant is, the more fuel consumption is saved for the operation of the system.
In a unit power generation plan, units with high economy and small load regulation range such as wind power, nuclear power and large coal power units are used for bearing system base load, generator sets with large load regulation range, strong adaptability to load change and flexible operation such as natural gas generator sets and hydroelectric generator sets can be used as peak regulation power supplies of the system and used for bearing peak load, but most areas in China lack of peak regulation water resources, a power grid faces larger peak regulation requirements along with the grid connection of new energy such as wind power and the like, dispatches each unit according to an equivalent micro-increment rate method in random production simulation of a power system, the unit with low fuel consumption is dispatched preferentially, then the unit with high fuel consumption is dispatched, in a power generation system taking coal power as a main part, the peak output is usually small thermal power plants, the operation is flexible but the coal consumption is large, the natural gas unit is high in load regulation speed, the start-stop cost of the natural gas unit is lower than that of a coal-fired unit, the natural gas unit participates in peak regulation, the coal-fired power generation system small peak regulation coal-fired power generation system with high coal consumption and expensive power generation cost can be reduced.
The calculation formula of the peak shaving benefit is as follows (11):
Bpeak-shaving＝Ftotal-F'total(11)
wherein, Bpeak-shavingThe peak shaving benefit of the natural gas power plant is shown; ftotalRepresenting the fuel cost and start-stop cost of the actual system; f'totalRepresenting fuel costs and start-stop costs of the replacement system;
when the peak shaving benefit is used for evaluation, if the peak shaving benefit is higher, the fuel cost and the start-stop cost of the natural gas unit reduced by participating in peak shaving are more, so that the running cost of the system is lower.
The method is characterized in that short-time load fluctuation and unplanned load increase or decrease are inevitable in the operation process of a power system, the fluctuation has randomness of and cannot be predicted in advance, if the power generation power of the system cannot be adjusted timely to the load fluctuation, the frequency of the system is fluctuated, the quality of power supply is influenced, therefore, parts of load spare capacity need to be reserved in the system, the output of a generator set is adjusted when the load fluctuates, and the real-time balance between the power generation power and the power utilization power is kept.
In the technical scheme of the invention, the reliability benefit is measured by a system power shortage time expected value LOLE and a power shortage expected value EENS;
in a certain time period, the probability that the outage capacity of the unit is equal to or greater than the reserve capacity is the expected value of the power shortage time of the system, and the calculation formula is as follows (12):
wherein L isjRepresents daily spike load on day j; n represents the number of days during the study; csIndicating the installed capacity of the system in the time period; p [ X is more than or equal to Cs-Lj]Representing the probability that the outage capacity is more than or equal to the spare capacity on the j th day in the time period; x represents the outage capacity;
the calculation formula of the annual load power failure time expectation value is as follows (13):
Figure BDA0002202304130000142
wherein m represents the number of study sessions in years, i represents the number of days in the ith session, and LijRepresents the peak load at day j within the ith time period; ciIndicating the installed capacity of the system in the ith time slot,
Figure BDA0002202304130000144
representing the probability that the outage capacity of the jth day is more than or equal to the spare capacity in the ith time period;
when the expected value of the power shortage time of the system is used for evaluation, if the expected value of the power shortage time of the system is lower, the probability that the outage capacity of the unit is equal to or larger than the spare capacity is lower, and the reliability is higher.
The expected electric power shortage EENS is an expected electric power shortage caused by the fact that the capacity of a generator set provided by the power system is smaller than the load demand capacity, and for a certain known outage capacity, the expected electric power shortage EENS is equal to the probability that the insufficient capacity is multiplied by the outage capacity, and the calculation formula is as shown in the formula (14):
EENS＝(X-R)×P(X) (14)
wherein R represents the spare capacity of the system;
the expected value of the electricity shortage in years is calculated according to the formula (15):
Figure BDA0002202304130000143
wherein, Pijk(X) represents the probability that the k-th hour outage capacity of the j day in the i-th time period is equal to or greater than X, m represents the number of time periods in years, njRepresents days in the j-th time periodNumber, LijkRepresents the hour load of the kth hour of the jth day during the ith time period;
when the expected power shortage value is used for evaluation, if the expected power shortage value is lower, the lower the power shortage value is, the lower the power shortage caused by the fact that the capacity of the generator set is smaller than the load demand capacity is, and the higher the reliability of the system is.
In step S3, the calculation of the pollutant emission includes calculating the pollutant emission of the conventional coal-fired power plant, the coal-fired power plant with the desulfurizer, and the natural gas power plant during the operation, that is, in order to directly reflect the influence of the conventional coal-fired power plant, the coal-fired power plant with the desulfurizer, and the natural gas power plant on the environment during the specific implementation, simple examples are adopted to calculate the specific pollutant emission of the three power plants during the operation, and a table is established for comparison and analysis, wherein the pollutant emission corresponding to each kWh is used in the invention.
In the operation process of the power system, each type of power plant meets the balance between the power and the electric quantity of the system through dispatching and distribution, and the total pollutant discharge amount generated in the period is which is an environmental benefit index of the whole system and reflects the influence degree of the natural gas unit and the coal-fired unit on the environment after the natural gas unit and the coal-fired unit are operated in a combined mode.
The lower the pollutant discharge amount is, the smaller the influence of power plant power generation on the environment is, and in the process that a power system meets load requirements, all power plants cooperate to output power and the pollutant discharge is carried out according to corresponding national policies; the lower the amount of pollutants discharged by a power plant in the system, the less the system will damage the environment.
In step S3, the calculation of the environmental cost includes calculating the total environmental cost of the power plant by charging the total amount of the power plant ' S emissions and compensating for the loss of the pollutant according to the pollution discharge charging system, and since the environmental cost in environmental accounting is defined as the cost of taking measures to manage the environmental impact of the enterprise ' S activities and other costs due to the enterprise ' S environmental objective and requirements, the environmental cost can be described as the environmental load of the thermal power plant for reducing the production and management processes or the costs of taking series of environmental protection activities for executing the national environmental policy and regulation, and the cost of the thermal power plant ' S monetary calculation includes the costs of paying the pollution discharge fee, pollution and the like to the relevant department for avoiding or controlling the environmental impact of the pollutant or for reducing the pollutant emission, the costs of equipment and management, such as the cost of desulfurization, denitrification, dust removal, and the like, and the cost of the discharged pollutant is calculated to the relevant department , the former is the cost of the environmental equipment cost, the equipment cost of the power plant ' S operation and the loss management cost of the latter is calculated directly, and the cost of the environmental protection is calculated as the cost.
The technical scheme of the invention adopts the quantitative calculation of the environmental cost brought by natural gas power generation, wherein sets of standards are required to evaluate the environmental cost, the common method is that the environmental cost is evaluated by calculating the total pollution discharge charge of a power plant and the compensation degree of pollutant loss according to a pollution discharge charging system, the compensation degree of the pollutant loss in China is 25 percent according to the ratio of the pollution discharge treatment cost charged in China to the loss cost caused by environmental pollution, the loss compensation degrees of various pollutants are assumed to be equal, and the SO compensation degrees of Beijing city (1500 yuan/t) and southern city (2000 yuan/t) are referred to2The total emission charge standard is used for reference of corresponding environmental cost data in the United states, and the environmental cost standard of each pollutant in the power industry in China can be calculated, as shown in Table 1:
TABLE 1 environmental cost Standard of pollutants for the Electrical industry (Yuan/kg)
Contaminants SO2 NOX CO CO2 TSP Ash and slag
Environmental cost 9.20 12.27 1.53 0.037 3.37 0.18
Similarly, by using the environmental cost standards of each pollutant, the total pollution emission of the power system analyzed before can be converted into the total environmental cost of the power system, the economic loss caused by pollution can be monetized, and the monetized economic loss can be used as a second index of the environmental benefit of the natural gas power generation on the system.
When the environmental cost is used for evaluation, if the environmental cost is lower, the lower the cost of the power plant to the society caused by pollution emission is, and the higher the environmental benefit generated by the participation of the natural gas unit to the power system is.
Corresponding to the method, the invention also provides an comprehensive energy system natural gas power generation benefit evaluation system, which comprises a financial index evaluation module, a system benefit evaluation module and an environmental benefit evaluation module;
the financial index evaluation module is used for acquiring financial related data of the system, calculating a financial evaluation index according to the financial related data, and evaluating the profit capacity of the natural gas power generation by using the calculated financial evaluation index; the financial evaluation indexes at least comprise net present value, internal rate of return and investment recovery period;
the system benefit evaluation module is used for acquiring operation related data of the system, calculating a system benefit index according to the operation related data, and evaluating the benefit of the operation mode of the natural gas generator set on the power system by using the calculated system benefit index; the system benefit index at least comprises capacity benefit, fuel benefit, peak shaving benefit and reliability benefit;
the environmental benefit evaluation module is used for acquiring environmental related data of the system, calculating an environmental benefit index according to the environmental related data, and evaluating the benefit of the natural gas power generation system on environmental protection by using the calculated environmental benefit index; the environmental benefit indicators include at least pollutant emissions and environmental costs.
In the financial index evaluation module, the calculation formula of the net present value is as follows (1):
Figure BDA0002202304130000171
wherein NPV represents the net present value; t denotes cash flow occurred in the t year; CI represents the cash inflow for the year; CO represents cash out for the year; i represents a discount rate; n represents a survey period;
the internal rate of return is calculated as follows:
the internal yield is the discount rate when the current value accumulation of the net cash flow of each year is equal to 0 in the construction and production operation years of the investment project, and the calculation formula is as follows (2):
Figure BDA0002202304130000172
the IRR is solved approximately using interpolation, the calculation formula is as follows (3):
Figure BDA0002202304130000173
wherein IRR represents an internal rate of return; i.e. i1、i2Respectively representing the lowest sum of trial calculationsThe highest discount rate; NPV (i)1)、NPV(i2) Respectively represent a discount rate of i1、i2Net present value of time;
the return on investment period is calculated as follows:
the investment recovery period is the time required for the net income recovery project investment of the investment project, and the calculation formula is as follows (4):
the method comprises the following steps of (1) obtaining an investment recovery period by using accumulated net cash flow in a financial cash flow table, wherein a calculation formula is as follows:
Figure BDA0002202304130000175
wherein, PtRepresenting an investment recovery period; n ispThe year that the cumulative net cash flow begins to appear positive;
Figure BDA0002202304130000176
represents the absolute value of the cumulative net cash flow of the last year;representing the net cash flow in the year.
In the system benefit evaluation module, the calculation formula of the capacity benefit is as follows (6):
Bcapacity＝(IT-IES)+(CT-CES) (6)
wherein, BcapacityRepresenting the capacity benefit of the natural gas power plant; i isTRepresents the investment cost of other types of power plants; i isESRepresents the investment cost of the gas power plant; cTRepresents a fixed operating cost for other types of power plants; cESRepresents a fixed operating cost of the gas power plant;
the fuel efficiency is calculated as follows:
the fuel benefit is represented by the reduction of the average coal consumption rate and the average gas consumption rate, and the calculation formulas of the average coal consumption rate and the average gas consumption rate are respectively as shown in formula (7) and formula (8):
Figure BDA0002202304130000181
Figure BDA0002202304130000182
wherein, Cave-coalRepresenting the average coal consumption rate of the system; cave-gasRepresents the average gas consumption rate of the system; ccoalAnd CgasRepresenting the total coal and gas consumption in the system; pcoalAnd PgasRespectively representing the total output of all coal-electric units and the total output of all gas-electric units in the system;
after the average coal consumption rate and the average gas consumption rate of the system are obtained, the fuel benefit calculation formula of the natural gas power plant is as shown in the formula (9) and the formula (10):
Bcoal-saving＝Cave-coal-C'ave-coal(9)
Bgas-saving＝Cave-gas-C'ave-gas(10)
wherein, Bcoal-savingAnd Bgas-savingRespectively showing the coal saving benefit and the gas saving benefit of the natural gas power plant; cave-coalAnd Cave-gasRespectively representing the average coal consumption rate and the average gas consumption rate of the actual system; c'ave-coalAnd C'ave-gasRespectively representing the average coal consumption rate and the average gas consumption rate of the replacement system;
the calculation formula of the peak shaving benefit is as follows (11):
Bpeak-shaving＝Ftotal-F'total(11)
wherein, Bpeak-shavingThe peak shaving benefit of the natural gas power plant is shown; ftotalRepresenting the fuel cost and start-stop cost of the actual system; f'totalRepresenting fuel costs and start-stop costs of the replacement system;
the reliability benefit is measured by a system power shortage time expected value LOLE and a power shortage expected value EENS;
in a certain time period, the probability that the outage capacity of the unit is equal to or greater than the reserve capacity is the expected value of the power shortage time of the system, and the calculation formula is as follows (12):
Figure BDA0002202304130000183
wherein L isjRepresents daily spike load on day j; n represents the number of days during the study; csIndicating the installed capacity of the system in the time period; p [ X is more than or equal to Cs-Lj]Representing the probability that the outage capacity is more than or equal to the spare capacity on the j th day in the time period; x represents the outage capacity;
the calculation formula of the annual load power failure time expectation value is as follows (13):
Figure BDA0002202304130000191
wherein m represents the number of study sessions in years, i represents the number of days in the ith session, and LijRepresents the peak load at day j within the ith time period; ciRepresents the installed capacity of the system in the ith time slot, Pi[X≥Ci-Lij]Representing the probability that the outage capacity of the jth day is more than or equal to the spare capacity in the ith time period;
the expected electric power shortage EENS is an expected electric power shortage caused by the fact that the capacity of a generator set provided by the power system is smaller than the load demand capacity, and for a certain known outage capacity, the expected electric power shortage EENS is equal to the probability that the insufficient capacity is multiplied by the outage capacity, and the calculation formula is as shown in the formula (14):
EENS＝(X-R)×P(X) (14)
wherein R represents the spare capacity of the system;
the expected value of the electricity shortage in years is calculated according to the formula (15):
Figure BDA0002202304130000192
wherein, Pijk(X) represents the probability that the k-th hour outage capacity of the j day in the i-th time period is equal to or greater than X, m represents the number of time periods in years, njDenotes the number of days in the j-th time period, LijkRepresents the hour load of the kth hour on the jth day during the ith time period.
In the environmental benefit evaluation module, the calculation of the pollutant discharge amount includes: respectively calculating pollutant discharge amounts of three types of power plants, namely a conventional coal-fired power plant, a coal-fired power plant with a desulphurization device and a natural gas power plant in the operation process;
the calculation of the environmental cost includes: and (4) according to a pollution discharge charging system, calculating the total pollution discharge charging of the power plant and the compensation degree for pollutant loss to obtain the total environmental cost.
In summary, the invention has the advantages that the comprehensive evaluation is carried out on the natural gas power generation benefit of the comprehensive energy system by adopting three parts of a financial evaluation index, a system benefit index and an environmental benefit index, wherein the financial evaluation index reflects the profitability of natural gas power generation, including a financial net present value, an internal profitability and an investment recovery period, the system benefit index reflects the benefits of the operation mode of the natural gas power generation unit on the power system, including capacity benefits, fuel benefits, peak regulation benefits and reliability benefits, and the environmental benefit index reflects the benefits of natural gas serving as clean and environment-friendly green fossil energy sources and environmental protection, including pollutant discharge and environmental cost.
Although specific embodiments of the invention have been described above, it will be understood by those skilled in the art that the specific embodiments described are illustrative only and are not limiting upon the scope of the invention, and that equivalent modifications and variations can be made by those skilled in the art without departing from the spirit of the invention, which is to be limited only by the appended claims.

Claims (8)

  1. The method for evaluating the power generation benefit of the natural gas of the comprehensive energy system is characterized by comprising the following steps in no sequence:
    step S1, acquiring financial related data of the system, calculating a financial evaluation index according to the financial related data, and evaluating the profitability of natural gas power generation by using the calculated financial evaluation index; the financial evaluation indexes at least comprise net present value, internal rate of return and investment recovery period;
    s2, obtaining operation related data of the system, calculating a system benefit index according to the operation related data, and evaluating the benefit of the operation mode of the natural gas generator set on the power system by using the calculated system benefit index; the system benefit index at least comprises capacity benefit, fuel benefit, peak shaving benefit and reliability benefit;
    s3, acquiring environment-related data of the system, calculating an environment benefit index according to the environment-related data, and evaluating the benefit of the natural gas power generation system on environmental protection by using the calculated environment benefit index; the environmental benefit indicators include at least pollutant emissions and environmental costs.
  2. 2. The evaluation method for natural gas power generation benefits of kinds of integrated energy systems according to claim 1, wherein in the step S1, the calculation formula of the net present value is as follows (1):
    Figure FDA0002202304120000011
    wherein NPV represents the net present value; t denotes cash flow occurred in the t year; CI represents the cash inflow for the year; CO represents cash out for the year; i represents a discount rate; n represents a survey period;
    the internal rate of return is calculated as follows:
    the internal yield is the discount rate when the current value accumulation of the net cash flow of each year is equal to 0 in the construction and production operation years of the investment project, and the calculation formula is as follows (2):
    Figure FDA0002202304120000012
    the IRR is solved approximately using interpolation, the calculation formula is as follows (3):
    Figure FDA0002202304120000021
    wherein IRR represents an internal rate of return; i.e. i1、i2Respectively representing the lowest and highest discount rates obtained by trial calculation; NPV (i)1)、NPV(i2) Respectively represent a discount rate of i1、i2Net present value of time;
    the return on investment period is calculated as follows:
    the investment recovery period is the time required for the net income recovery project investment of the investment project, and the calculation formula is as follows (4):
    the method comprises the following steps of (1) obtaining an investment recovery period by using accumulated net cash flow in a financial cash flow table, wherein a calculation formula is as follows:
    Figure FDA0002202304120000023
    wherein, PtRepresenting an investment recovery period; n ispThe year that the cumulative net cash flow begins to appear positive;
    Figure FDA0002202304120000024
    represents the absolute value of the cumulative net cash flow of the last year;
    Figure FDA0002202304120000025
    representing the net cash flow in the year.
  3. 3. The method for evaluating the power generation benefits of comprehensive energy systems based on natural gas according to claim 1, wherein in step S2, the formula for calculating the capacity benefits is as follows (6):
    Bcapacity＝(IT-IES)+(CT-CES) (6)
    wherein, BcapacityRepresenting the capacity benefit of the natural gas power plant; i isTRepresents the investment cost of other types of power plants; i isESRepresents the investment cost of the gas power plant; cTRepresents a fixed operating cost for other types of power plants; cESRepresents a fixed operating cost of the gas power plant;
    the fuel efficiency is calculated as follows:
    the fuel benefit is represented by the reduction of the average coal consumption rate and the average gas consumption rate, and the calculation formulas of the average coal consumption rate and the average gas consumption rate are respectively as shown in formula (7) and formula (8):
    Figure FDA0002202304120000031
    Figure FDA0002202304120000032
    wherein, Cave-coalRepresenting the average coal consumption rate of the system; cave-gasRepresents the average gas consumption rate of the system; ccoalAnd CgasRepresenting the total coal and gas consumption in the system; pcoalAnd PgasRespectively representing the total output of all coal-electric units and the total output of all gas-electric units in the system;
    after the average coal consumption rate and the average gas consumption rate of the system are obtained, the fuel benefit calculation formula of the natural gas power plant is as shown in the formula (9) and the formula (10):
    Bcoal-saving＝Cave-coal-C'a've-coal(9)
    Bgas-saving＝Cave-gas-C′ave-gas(10)
    wherein,Bcoal-savingand Bgas-savingRespectively showing the coal saving benefit and the gas saving benefit of the natural gas power plant; cave-coalAnd Cave-gasRespectively representing the average coal consumption rate and the average gas consumption rate of the actual system; c'ave-coalAnd C'ave-gasRespectively representing the average coal consumption rate and the average gas consumption rate of the replacement system;
    the calculation formula of the peak shaving benefit is as follows (11):
    Bpeak-shaving＝Ftotal-F′total(11)
    wherein, Bpeak-shavingThe peak shaving benefit of the natural gas power plant is shown; ftotalRepresenting the fuel cost and start-stop cost of the actual system; f'totalRepresenting fuel costs and start-stop costs of the replacement system;
    the reliability benefit is measured by a system power shortage time expected value LOLE and a power shortage expected value EENS;
    in a certain time period, the probability that the outage capacity of the unit is equal to or greater than the reserve capacity is the expected value of the power shortage time of the system, and the calculation formula is as follows (12):
    Figure FDA0002202304120000033
    wherein L isjRepresents daily spike load on day j; n represents the number of days during the study; csIndicating the installed capacity of the system in the time period; p [ X is more than or equal to Cs-Lj]Representing the probability that the outage capacity is more than or equal to the spare capacity on the j th day in the time period; x represents the outage capacity;
    the calculation formula of the annual load power failure time expectation value is as follows (13):
    Figure FDA0002202304120000041
    wherein m represents the number of study sessions in years, i represents the number of days in the ith session, and LijRepresents the peak load at day j within the ith time period; ciRepresenting systems in the ith time periodThe capacity of the machine is installed,representing the probability that the outage capacity of the jth day is more than or equal to the spare capacity in the ith time period;
    the expected electric power shortage EENS is an expected electric power shortage caused by the fact that the capacity of a generator set provided by the power system is smaller than the load demand capacity, and for a certain known outage capacity, the expected electric power shortage EENS is equal to the probability that the insufficient capacity is multiplied by the outage capacity, and the calculation formula is as shown in the formula (14):
    EENS＝(X-R)×P(X) (14)
    wherein R represents the spare capacity of the system;
    the expected value of the electricity shortage in years is calculated according to the formula (15):
    Figure FDA0002202304120000043
    wherein, Pijk(X) represents the probability that the k-th hour outage capacity of the j day in the i-th time period is equal to or greater than X, m represents the number of time periods in years, njDenotes the number of days in the j-th time period, LijkRepresents the hour load of the kth hour on the jth day during the ith time period.
  4. 4. The method of evaluating the power generation efficiency of comprehensive energy systems according to claim 1, wherein in step S3, the calculation of the emission of pollutants includes calculating the emission of pollutants during the operation of a conventional coal-fired power plant, a coal-fired power plant with a desulfurizer, and a natural gas power plant, respectively;
    the calculation of the environmental cost includes: and (4) according to a pollution discharge charging system, calculating the total pollution discharge charging of the power plant and the compensation degree for pollutant loss to obtain the total environmental cost.
  5. 5, kinds of comprehensive energy system natural gas power generation benefit evaluation system, wherein the system includes the evaluation module of financial index, system benefit evaluation module and environmental benefit evaluation module;
    the financial index evaluation module is used for acquiring financial related data of the system, calculating a financial evaluation index according to the financial related data, and evaluating the profit capacity of the natural gas power generation by using the calculated financial evaluation index; the financial evaluation indexes at least comprise net present value, internal rate of return and investment recovery period;
    the system benefit evaluation module is used for acquiring operation related data of the system, calculating a system benefit index according to the operation related data, and evaluating the benefit of the operation mode of the natural gas generator set on the power system by using the calculated system benefit index; the system benefit index at least comprises capacity benefit, fuel benefit, peak shaving benefit and reliability benefit;
    the environmental benefit evaluation module is used for acquiring environmental related data of the system, calculating an environmental benefit index according to the environmental related data, and evaluating the benefit of the natural gas power generation system on environmental protection by using the calculated environmental benefit index; the environmental benefit indicators include at least pollutant emissions and environmental costs.
  6. 6. The comprehensive energy system natural gas power generation benefit evaluation system according to claim 5, wherein in the financial index evaluation module, the calculation formula of the net present value is as follows (1):
    Figure FDA0002202304120000051
    wherein NPV represents the net present value; t denotes cash flow occurred in the t year; CI represents the cash inflow for the year; CO represents cash out for the year; i represents a discount rate; n represents a survey period;
    the internal rate of return is calculated as follows:
    the internal yield is the discount rate when the current value accumulation of the net cash flow of each year is equal to 0 in the construction and production operation years of the investment project, and the calculation formula is as follows (2):
    Figure FDA0002202304120000052
    the IRR is solved approximately using interpolation, the calculation formula is as follows (3):
    Figure FDA0002202304120000053
    wherein IRR represents an internal rate of return; i.e. i1、i2Respectively representing the lowest and highest discount rates obtained by trial calculation; NPV (i)1)、NPV(i2) Respectively represent a discount rate of i1、i2Net present value of time;
    the return on investment period is calculated as follows:
    the investment recovery period is the time required for the net income recovery project investment of the investment project, and the calculation formula is as follows (4):
    Figure FDA0002202304120000061
    the method comprises the following steps of (1) obtaining an investment recovery period by using accumulated net cash flow in a financial cash flow table, wherein a calculation formula is as follows:
    Figure FDA0002202304120000062
    wherein, PtRepresenting an investment recovery period; n ispThe year that the cumulative net cash flow begins to appear positive;
    Figure FDA0002202304120000063
    represents the absolute value of the cumulative net cash flow of the last year;
    Figure FDA0002202304120000064
    representing the net cash flow in the year.
  7. 7. The comprehensive energy system natural gas power generation benefit evaluation system according to claim 5, wherein in the system benefit evaluation module, the calculation formula of the capacity benefit is as follows (6):
    Bcapacity＝(IT-IES)+(CT-CES) (6)
    wherein, BcapacityRepresenting the capacity benefit of the natural gas power plant; i isTRepresents the investment cost of other types of power plants; i isESRepresents the investment cost of the gas power plant; cTRepresents a fixed operating cost for other types of power plants; cESRepresents a fixed operating cost of the gas power plant;
    the fuel efficiency is calculated as follows:
    the fuel benefit is represented by the reduction of the average coal consumption rate and the average gas consumption rate, and the calculation formulas of the average coal consumption rate and the average gas consumption rate are respectively as shown in formula (7) and formula (8):
    Figure FDA0002202304120000066
    wherein, Cave-coalRepresenting the average coal consumption rate of the system; cave-gasRepresents the average gas consumption rate of the system; ccoalAnd CgasRepresenting the total coal and gas consumption in the system; pcoalAnd PgasRespectively representing the total output of all coal-electric units and the total output of all gas-electric units in the system;
    after the average coal consumption rate and the average gas consumption rate of the system are obtained, the fuel benefit calculation formula of the natural gas power plant is as shown in the formula (9) and the formula (10):
    Bcoal-saving＝Cave-coal-C′ave-coal(9)
    Bgas-saving＝Cave-gas-C′ave-gas(10)
    wherein, Bcoal-savingAnd Bgas-savingRespectively represent the dayCoal saving benefit and gas saving benefit of the gas power plant; cave-coalAnd Cave-gasRespectively representing the average coal consumption rate and the average gas consumption rate of the actual system; c'ave-coalAnd C'ave-gasRespectively representing the average coal consumption rate and the average gas consumption rate of the replacement system;
    the calculation formula of the peak shaving benefit is as follows (11):
    Bpeak-shaving＝Ftotal-F′total(11)
    wherein, Bpeak-shavingThe peak shaving benefit of the natural gas power plant is shown; ftotalRepresenting the fuel cost and start-stop cost of the actual system; f'totalRepresenting fuel costs and start-stop costs of the replacement system;
    the reliability benefit is measured by a system power shortage time expected value LOLE and a power shortage expected value EENS;
    in a certain time period, the probability that the outage capacity of the unit is equal to or greater than the reserve capacity is the expected value of the power shortage time of the system, and the calculation formula is as follows (12):n
    LOLE ≧ SIGMA P [ X ≧ Cs-Lj](12)
    Wherein L isjRepresents daily spike load on day j; n represents the number of days during the study; csIndicating the installed capacity of the system in the time period; p [ X is more than or equal to Cs-Lj]Representing the probability that the outage capacity is more than or equal to the spare capacity on the j th day in the time period; x represents the outage capacity;
    the calculation formula of the annual load power failure time expectation value is as follows (13):
    Figure FDA0002202304120000071
    wherein m represents the number of study sessions in years, i represents the number of days in the ith session, and LijRepresents the peak load at day j within the ith time period; ciRepresents the installed capacity of the system in the ith time slot, Pi[X≥Ci-Lij]Indicating the probability that the outage capacity of the jth day is more than or equal to the spare capacity in the ith time period；
    The expected electric power shortage EENS is an expected electric power shortage caused by the fact that the capacity of a generator set provided by the power system is smaller than the load demand capacity, and for a certain known outage capacity, the expected electric power shortage EENS is equal to the probability that the insufficient capacity is multiplied by the outage capacity, and the calculation formula is as shown in the formula (14):
    EENS＝(X-R)×P(X) (14)
    wherein R represents the spare capacity of the system;
    the expected value of the electricity shortage in years is calculated according to the formula (15):
    Figure FDA0002202304120000081
    wherein, Pijk(X) represents the probability that the k-th hour outage capacity of the j day in the i-th time period is equal to or greater than X, m represents the number of time periods in years, njDenotes the number of days in the j-th time period, LijkRepresents the hour load of the kth hour on the jth day during the ith time period.
  8. 8. The comprehensive energy system natural gas power generation benefit evaluation system according to claim 5, wherein in the environmental benefit evaluation module, the calculation of the pollutant discharge amount comprises calculating the pollutant discharge amount of three types of power plants, namely a conventional coal-fired power plant, a coal-fired power plant with a desulphurization device and a natural gas power plant, in the operation process respectively;
    the calculation of the environmental cost includes: and (4) according to a pollution discharge charging system, calculating the total pollution discharge charging of the power plant and the compensation degree for pollutant loss to obtain the total environmental cost.
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