CN110061499B - Operation method of grid-connected micro-grid under differentiated power price - Google Patents
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Abstract
The invention discloses an operation method of a grid-connected micro-grid under differentiated power price, which comprises the following steps: (1) determining the electricity price at the current time t, and then calculating whether the combined cooling heating and power system can be profitable; (2) under the condition that the combined cooling heating and power system cannot be profitable, comparing the sum of the load demand and the combined cooling, heating and power demand with the magnitude of photovoltaic output, and if the sum is greater than or equal to the magnitude of the photovoltaic output, discharging the energy storage battery or purchasing electricity from a large power grid; if the current value is less than the preset value, charging the energy storage battery or selling electricity to a large power grid; (3) and (3) comparing the load demand with the sum of the photovoltaic output and the combined cooling, heating and power under the condition that the combined cooling, heating and power system can be profitable, wherein the principle is the same as the step (2). The method analyzes the aggregation load characteristics of the grid-connected point, obtains the output strategies and state change ways of various power supplies in different scenes, establishes an optimized operation model on the basis, analyzes the output characteristics of the grid-connected micro-grid, and lays a foundation for planning and designing the grid-connected micro-grid.
Description
Technical Field
The invention belongs to the field of operation and control of power systems, and particularly relates to an operation method of a grid-connected micro-grid under a differentiated power price.
Background
The micro-grid is a small-sized power generation and distribution system organically integrating renewable energy sources, loads, energy storage devices and the like, can improve the utilization rate of distributed energy sources, realizes effective distributed energy source scheduling, and gradually becomes a main means for solving the grid connection problem of distributed power sources. The grid-connected microgrid is used as a mainly propelled microgrid form, and compared with an island microgrid, the requirement of the microgrid on autonomy is reduced, so that the construction and operation costs are saved, and the microgrid has certain feasibility in China at the present stage.
The grid-connected point aggregated load characteristic is that the microgrid optimizes and controls the exchange power formed by controllable energy sources in the microgrid and a power distribution network according to the change of an external electricity price mechanism, loads and renewable energy sources. Because the grid-connected micro-grid is in grid-connected operation in most of time, the degree of dependence on the grid is high, and the aggregation load characteristic of a grid-connected point of the grid-connected micro-grid is bidirectional uncertainty, so that the grid-connected micro-grid has certain influence on the operation of the grid. Therefore, the research on the micro-grid operation strategy and the load aggregation characteristic of the grid-connected point under the existing policy mechanism has important significance for planning and operating the power distribution network at the present stage and adjusting the future market mechanism.
The load characteristics of the commercial micro-grid have an obvious rule of day, peak and night, which is caused by the working time of workers, electricity is mainly concentrated in the working peak period of the morning and the afternoon, the distributed energy types are the most, the distributed energy types generally comprise photovoltaic, energy storage batteries and combined production of cold, heat and power, and the loads are mainly electricity loads such as illumination, air conditioning, power and the like. At present, two modes of economic operation and market bidding are assumed to be presented in the micro-grid in research, and internal regulation and transaction are carried out along with information of external electricity prices on the assumption that the electricity price for buying and selling is interacted with the power grid. However, at the present stage, the domestic market mechanism is not sound, the price of the on-line electricity is independently checked according to various power supplies, and the comprehensive price of the micro-grid is not available, so that the research on the power generation and optimized scheduling method of various power supplies in the commercial grid-connected micro-grid is of great significance.
Disclosure of Invention
In order to overcome the above defects, the present invention provides a method for operating a grid-connected microgrid with a differentiated power price.
In order to achieve the purpose, the invention adopts the following technical scheme:
an operation method of a grid-connected micro-grid under a differentiated power price comprises the following steps:
(1) determining the electricity price at the current time t, then calculating whether the combined cooling heating and power system can be profitable, if not, the combined cooling heating and power system is equivalent to the electric equipment, using the electric refrigerator and the electric boiler, otherwise, the combined cooling heating and power system is equivalent to the electric power generation equipment, and using the combined cooling heating and power system;
(2) under the condition that the combined cooling heating and power system cannot be profitable, comparing the sum of the load demand and the combined cooling and power demand with the magnitude of photovoltaic output, if the sum is more than or equal to the photovoltaic output, the supply is not in demand at the moment, and the energy storage battery discharges (outputs) or purchases electricity from a large power grid; if the output is less than the photovoltaic output, the supply is greater than the demand, and the energy storage battery is charged or the electricity is sold to a large power grid;
(3) under the condition that the combined cooling heating and power system can be profitable, comparing the load demand with the sum of the photovoltaic output and the combined cooling and power, if the load demand is more than or equal to the sum of the photovoltaic output and the combined cooling and power, the demand is not met at the moment, discharging the energy storage battery (output) or purchasing power from the large power grid, and if the load demand is less than the sum of the photovoltaic output and the combined cooling, power, the demand is greater at the moment, and the energy storage battery is charged or the power is sold to the large power grid.
Preferably, the calculation formula of whether the combined cooling heating and power system in step (1) can achieve profit is as follows:
Vt GT·λGT-pGT·λt g＜(pgheat+pgcool)·λt g，
(Vt GT·λGT–pGT·λt g) Represents the operating cost of the gas turbine to supply the cold and hot loads during the period t, (p)gheat +pgcool)·λt gThe electric charge which is generated by heat generation of an electric boiler and refrigeration of an electric refrigerator and is equal to the heating capacity and the refrigerating capacity required by combined cooling, heating and power generation of a gas turbine in the t-time section is represented; when the former is smaller than the latter, the combined cooling, heating and power system is profitable.
Preferably, in the step (2), the relation between the energy storage cost and the electricity price is considered in the selection of charging and discharging of the energy storage battery and the electricity selling and purchasing to the large power grid, the principle of low energy storage and high power generation is followed, and the state of charge (SOC) of the energy storage battery is also considered.
Preferably, the low-storage high-emission principle is as follows: in a given time slice t, the electricity prices λ at the time t are first comparedt gAnd the unit generating capacity cost lambda of the energy storage batteryESWhen the magnitude of (d) is λES＞λt gAnd if not, discharging the energy storage battery under the condition of meeting the discharge power constraint.
Preferably, the upper charge limit and the lower discharge limit of the state of charge SOC of the energy storage battery are 80% and 20%, respectively.
Preferably, when the combined cooling heating and power system cannot gain a profit, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is less than the photovoltaic output, if the energy storage remaining power does not reach the charging limit value, and the current electricity price is lower than the energy storage and power generation cost, the energy storage battery is charged with the maximum charging power, and the external characteristics of the microgrid and the power generation cost are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cPower consumed by combined cooling, heating and power system at time t, pt chmCharging power for the energy storage battery at time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at the time t of the power company;
meanwhile, the power generation cost of the energy storage battery is increased to:
λt ESfor the cost of the energy storage battery at time t, EtFor the voltage of the energy-storing cell at time t, λt gThe price of electricity from the electric power company at time t.
Preferably, when the combined cooling heating and power system cannot gain a profit, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is less than the photovoltaic output, if the energy storage remaining power does not reach the charging limit value, and the current electricity price is higher than the energy storage and power generation cost, the energy storage battery is charged by only utilizing the photovoltaic power generation allowance, and the external characteristics of the microgrid and the power generation cost are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cPower consumed by combined cooling, heating and power system at time t, pt chmCharging power for the energy storage battery at time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at time t for the utility company.
Preferably, when the combined cooling, heating and power cannot be profitable, the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is less than the photovoltaic output, and the energy storage residual capacity reaches the charging limit value, the energy storage battery is not charged, and the external characteristics of the microgrid and the power generation cost are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cThe power consumed by the combined cooling, heating and power system at the moment t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at time t for the utility company.
Preferably, when the combined cooling heating and power system cannot gain a profit, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is greater than or equal to the photovoltaic output, if the current electricity price of the large power grid is the valley hour electricity price, the current time is mostly midnight and midnight, if the energy storage residual capacity at the time reaches the charging limit value, the energy storage battery is not charged, and the appearance and the power generation cost of the micro power grid are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cThe power consumed by the combined cooling, heating and power generation at the time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at time t for the utility company.
Preferably, when the combined cooling heating and power system cannot gain a profit, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is greater than or equal to the photovoltaic output, if the current electricity price of the large power grid is the electricity price at the valley time, if the remaining energy storage capacity at this time does not reach the charging limit value, the energy storage battery is charged, and the external characteristics of the micro power grid and the power generation cost are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cPower consumed for combined cooling, heating and power at time t, pt chmCharging power for the energy storage battery at time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at time t for the utility company.
Meanwhile, the power generation cost of the energy storage battery is increased to:
λt ESfor the cost of the energy storage battery at time t, EtFor the voltage of the energy-storing cell at time t, λt gThe price of electricity at time t for the power company.
Preferably, when the combined cooling heating and power system cannot be profitable, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is greater than or equal to the photovoltaic output, if the current electricity price of the large power grid is not the electricity price at the valley time, the stored energy residual electric quantity has reached the discharge limit value, or the stored energy residual electric quantity has not reached the discharge limit value and the current electricity price of the power grid is lower than the stored energy power generation cost, the stored energy is not discharged, and the external characteristics of the micro power grid and the power generation cost are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor photovoltaic output at time t，pt LLoad at time t, pt h-cThe power consumed by the combined cooling, heating and power generation at the time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at time t for the utility company.
Preferably, when the combined cooling heating and power system cannot gain a profit, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is greater than or equal to the photovoltaic output, if the current electricity price of the large power grid is not the electricity price at valley time, the energy storage residual capacity does not reach the discharge limit value, and the current electricity price of the power grid is higher than the energy storage power generation cost, the energy storage is discharged, and the external characteristics of the micro power grid and the power generation cost are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cPower consumed for combined cooling, heating and power at time t, pt dismIs the discharge power of the energy storage battery at time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tt ESThe power generation cost of the energy storage battery at the time t.
Preferably, when the combined cooling heating and power system can obtain a profit and the load demand is less than the sum of the photovoltaic output and the combined cooling, heating and power, if the remaining energy does not reach the charging limit and the current electricity price is lower than the energy storage and power generation cost, the energy storage battery is charged with the maximum charging power, and the external characteristics of the microgrid and the power generation cost are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, pt chmFor charging the energy storage cell at time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at the time t of the power company;
meanwhile, the power generation cost of the energy storage battery is increased to:
λt ESfor the cost of the energy storage battery at time t, EtFor the voltage of the energy storage cell at time t, pt chmCharging power, lambda, of the energy storage cell at time tt gThe price of electricity at time t for the utility company.
Preferably, when the combined cooling heating and power system can be profitable and the load demand is less than the sum of the photovoltaic output and the combined cooling, heating and power, if the remaining energy storage capacity does not reach the charging limit and the current electricity price is higher than the energy storage and power generation cost, the energy storage battery is charged by using only the photovoltaic power generation allowance, and the external characteristics of the microgrid and the power generation cost are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, pt chmFor charging the energy storage cell at time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTIs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system.
Preferably, when the combined cooling heating and power system can gain a profit, the load demand is less than the sum of the photovoltaic output and the combined cooling, heating and power, and the energy storage battery is not charged when the energy storage remaining capacity reaches the charging limit value, the external characteristics of the microgrid and the power generation cost are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTAs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system.
Preferably, when the combined cooling heating and power system can obtain a profit and the load demand is greater than or equal to the sum of the photovoltaic output and the combined cooling, heating and power, if the current electricity price of the large power grid is the electricity price at the valley hour, the current time is mostly at midnight, if the remaining energy of the stored energy at the moment reaches the charging limit, the energy storage battery is not charged, and the external characteristics of the micro power grid and the power generation cost are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTAs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system.
When the combined cooling heating and power system can be profitable, the load demand is more than or equal to the sum of photovoltaic output and combined cooling, heating and power, if the current electricity price of the large power grid is the electricity price at the valley time, if the energy storage residual capacity does not reach the charging limit value at the moment, the energy storage battery is charged, and the external characteristics and the power generation cost of the micro power grid are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, pt chmFor charging the energy storage cell at time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTIs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system;
meanwhile, the power generation cost of the energy storage battery is increased to:
λt ESfor the cost of the energy storage battery at time t, EtFor the voltage of the energy storage cell at time t, pt chmCharging power, lambda, of the energy storage cell at time tt gThe price of electricity at time t for the utility company.
When the combined cooling heating and power system can be profitable, the load demand is more than or equal to the sum of the photovoltaic output and the combined cooling heating and power, if the current large power grid electricity price is not the electricity price at the valley time and the stored energy residual electricity quantity reaches the discharge limit value, or the stored energy residual electricity quantity does not reach the discharge limit value and the current power grid electricity price is lower than the stored energy power generation cost, the stored energy is not discharged, and the external characteristics of the micro power grid and the power generation cost are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor photovoltaic at tForce of etching, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTAs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system.
Preferably, when the combined cooling heating and power system can obtain a profit and the load demand is greater than or equal to the sum of the photovoltaic output and the combined cooling, heating and power, if the current electricity price of the large power grid is not the electricity price at valley time, the energy storage residual capacity does not reach the discharge limit value and the current electricity price of the power grid is higher than the energy storage and power generation cost, the energy storage and power discharge are performed, and the external characteristics of the micro-power grid and the power generation cost are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, pt dismDischarge power of the storage battery at time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tt ESThe unit generating capacity cost, lambda, of the energy storage battery at the time tGTAs unit gas cost, Vt GTNatural gas consumption for the combined cooling heating and power system.
The invention has the following positive beneficial effects: 1. the domestic market mechanism is not sound at the present stage, the on-line electricity price is independently checked according to various power supplies, the invention takes the existing power supply and load model as the basis, comprehensively considers the factors such as the on-line electricity price, the photovoltaic power generation cost, the photovoltaic on-line electricity price and the like and the operation characteristics of various distributed energy sources, takes the minimum operation cost of the micro-grid as the target, respectively analyzes the output strategies of the power supplies under different operation conditions of different grid-connected micro-grids, obtains 14 scheduling operation strategies of the micro-grid through optimization, covers all the conditions of actual operation, can carry out effective economic scheduling aiming at different operation modes, not only can reflect the real characteristics of grid-connected load of the micro-grid, but also can reflect the coordination part of various electricity prices, and has important significance for guiding relevant electricity price regulations in the future.
2. The method is based on the difference of the power price and the power generation cost of the power supply in the commercial grid-connected micro-grid, comprehensively considers the power price and the power generation cost of various power supplies in the commercial grid-connected micro-grid, provides different cost models aiming at the common power supply types contained in the commercial micro-grid, perfects the power supply configuration in the micro-grid, develops an optimized scheduling method of power supply output in different operation scenes of the grid-connected micro-grid, analyzes the aggregate load characteristic of grid-connected points, obtains output strategies and state change ways in different scenes of various power supplies, establishes an optimized operation model on the basis, analyzes the output characteristic of the grid-connected micro-grid, and lays a foundation for planning and designing the grid-connected micro-grid.
Drawings
FIG. 1 is a diagram of a commercial grid-connected microgrid system;
FIG. 2 is a schematic view of the operating principle of a gas turbine;
fig. 3 is a schematic diagram of a commercial grid-connected microgrid control strategy.
Detailed Description
The invention will be further illustrated with reference to some specific examples.
Fig. 1 is a structural diagram of a commercial grid-connected microgrid system, which is an integral part of an external power grid and is connected with a substation of a higher-level power grid through a static switch. The microgrid comprises a photovoltaic Power supply, an energy storage battery and a Combined Cooling, Heating and Power system, and the Combined Cooling, Heating and Power system (CCHP) consisting of a micro Gas Turbine (GT) simultaneously supplies heat (cold) energy and electric energy to users, so that the utilization efficiency of the Combined Cooling, Heating and Power system is improved.
The independent operation mode of the micro-grid carries out power supply control by aiming at the maximization of the self profit of the micro-grid, so that the micro-grid operation objective function is designed to be the minimum operation cost of the micro-grid, and the function is as follows:
in the formula: c is the daily running comprehensive cost; cprSelling electricity for the microgrid to obtain revenue; ccoIs a power supply power generation assembly; p is a radical oft ES、pt PVAnd pt GTThe output of the energy storage, photovoltaic and combined cooling heating and power system in the microgrid at the moment t is Vt GTConsuming natural gas quantity, lambda, for combined cooling, heating and power systemESAnd λPVLambda being the unit energy production cost of energy storage and photovoltaicsGTIs the unit gas cost; lambda [ alpha ]t gFor the electricity price of the power company at time t, LgThe utility grid charge purchased from the utility company for the microgrid.
A combined cooling, heating and power system, which is developed on the basis of a combined heat and power system, can be used for meeting the building energy requirements, is a total energy system for expanding and strengthening the traditional combined heat and power system in the aspects of application occasions, scale and the like, and the working principle of the system is shown in fig. 2.
According to different requirements, the system is generally divided into two operation modes of 'heating and power' and 'heating and power' according to the priority; the 'ordering electricity by heat' means that the system preferentially meets the requirement of heat energy load, electric energy is regarded as auxiliary, and if the requirement of electric energy load cannot be met, the electric energy can be supplemented by other ways (such as other power generation units or power purchasing from a power grid); in contrast, the "electric heating" mode preferentially ensures that the power load demand is met, while the thermal energy is used as an accessory, and if the thermal energy load demand is not met, the accessory can be supplemented by a thermal energy output device (such as a boiler).
The heat production or cold production of the combined cooling heating and power system should meet the following conditions:
wherein Q ishdem、QcdemRespectively, the hot and cold load requirements; qGTh、QGTcHeating and cooling capacity, Q, for combined production of cold and heat and electricity of gas turbinegridh、QgridcThe heating capacity and the refrigerating capacity of an electric boiler and an electric refrigerator are as follows:
in the above formula, pgheat、pgcoolThe power consumption power when the electric boiler and the electric refrigerator meet the cold and hot load is adopted respectively; cgh、CgcHeating coefficient and cooling coefficient of the electric boiler and the electric refrigerator respectively;
meanwhile, the output of the combined cooling heating and power system also meets the relationship between the consumed fuel cost and the power output of the unit shown in the formulas (4) to (7):
Qgt-co＝QGT×COPco (5)
Qgt-hs＝QGT×COPhe (6)
wherein Q isGTThe residual heat of the flue gas of the gas turbine; peOutputting power for the gas turbine; etaeThe power generation efficiency of the gas turbine is 27%; etaLThe heat dissipation loss coefficient of the gas turbine is 3 percent; qgt-co、Qgt-heRespectively providing refrigerating capacity and heating capacity for the waste heat of the flue gas of the gas turbine; COPco、COPheThe refrigeration coefficient and the heating coefficient of the bromine refrigerator are respectively; vGTThe amount of natural gas consumed by the gas turbine for runtime; Δ t1Is the operating time of the gas turbine; LHVNGIs the low heat value of natural gas.
The photovoltaic array is composed of a plurality of photovoltaic modules in series or parallel, wherein the output power of a single photovoltaic module can be expressed as:
in the above formula, psIs the maximum test power under standard test conditions, G is the actual illumination intensity, GSTThe solar illumination intensity under the standard test condition is 1000W/m2，ηTIs a temperature coefficient, TsFor the actual temperature of the component operation, an estimate can be made of the ambient temperature T and the illumination intensity G, TSTTaking the temperature as a reference temperature and taking the temperature as 25 ℃; wherein,
wherein T is the ambient temperature, TNThe temperature is the rated working temperature of the component in unit ℃; output power of the solar module as a function of illumination intensity G and ambient temperature T:
thus, the average output power of the photovoltaic array is:
the energy storage has the capability of stabilizing the electric energy supply in the system and plays a role in enhancing the schedulable performance of the distributed power generation unit, and the model of the energy storage battery can be controlled by a controllable voltage source EbConnected in series with a constant internal resistance, controlled source EbThe expression can be expressed as:
wherein E isbIs the no-load voltage of the energy storage battery, E0Is the constant voltage of the energy storage battery, K is the polarization voltage, Q is the capacity of the energy storage battery, a is the exponential gain voltage, B is the time gain capacity. The above parameters are calculated from the discharge characteristics of the energy storage cell.
Because the micro-grid comprises users with various energy requirements and can be operated in an isolated island mode, the scheduling operation of the micro-grid has to give priority to scheduling economy during grid connection on the condition of meeting the internal load requirements of the micro-grid. The economic operation problem when the micro-grid is connected to the grid needs to consider not only the output scheduling strategy of each micro-source, but also the influence of the electric energy transaction of the micro-grid and an external network on the benefit of the micro-grid system.
For a photovoltaic power supply, the photovoltaic power supply needs to continuously output power, and the photovoltaic cell can generate power as much as possible in any time section of the microgrid so as to reduce the output of other power supplies and reduce the power generation cost. Meanwhile, the energy storage battery should comply with a strategy of low energy storage and high energy generation, and in a given time section t, the electricity price lambda at the moment t is firstly comparedt gAnd the unit generating capacity cost lambda of the energy storage batteryESWhen the magnitude of (d) is λES＞λt gAnd if not, the energy storage battery is discharged under the condition of meeting the discharge power constraint. In addition, whether the combined cooling heating and power system can be profitable is taken as a criterion for starting and stopping, and when the operation cost is lower than the cost of electric heating/cooling, the combined cooling and power unit operates when the formula (13) is met.
Vt GT·λGT-pGT·λt g＜(pgheat+pgcool)·λt g (13)
In the formula (V)t GT·λGT–pGT·λt g) Represents the operating cost of the gas turbine to supply the cold and hot loads during the period t, (p)gheat+pgcool)·λt gThe expression that the heat produced by an electric boiler and the refrigeration produced by an electric refrigerator in the t time section is equivalent to the fuel gasThe electricity fee required by the heating capacity and the refrigerating capacity generated by the combined cooling, heating and power of the turbine; when the former is smaller than the latter, the combined cooling heating and power mode is more economical, otherwise, the electric boiler or the electric refrigerator is used to meet the load demand.
The power output strategy diagram of a commercial grid-connected microgrid power supply is shown in fig. 3, and in 14 modes in total, the photovoltaic power output does not consider light abandon and is full power, which is specifically as follows:
1. when the combined cooling heating and power system cannot be profitable, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is less than the photovoltaic output, if the residual energy storage capacity does not reach the charging limit value, and the current electricity price is lower than the energy storage and power generation cost, the energy storage battery is charged with the maximum charging power, corresponding to the mode C1, in which the external characteristics and the power generation cost of the microgrid are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cPower consumed by combined cooling, heating and power system at time t, pt chmCharging power for the energy storage battery at time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at the time t of the power company;
meanwhile, the power generation cost of the energy storage battery is increased to:
λt ESfor the cost of the energy storage battery at time t, EtFor the voltage of the energy-storing cell at time t, λt gThe price of electricity from the electric power company at time t.
2. When the combined cooling heating and power system cannot be profitable, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is less than the photovoltaic output, if the residual energy does not reach the charging limit value, and the current electricity price is higher than the energy storage and power generation cost, the energy storage battery is charged by only utilizing the photovoltaic power generation allowance, corresponding to a mode C2, in which the external characteristics and the power generation cost of the microgrid are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cPower consumed by combined cooling, heating and power system at time t, pt chmCharging power for the energy storage battery at time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at time t for the utility company.
3. When the combined cooling, heating and power cannot be profitable, the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is less than the photovoltaic output, and the residual energy storage capacity reaches the charging limit value, the energy storage battery is not charged, corresponding to the operation mode C3, the external characteristics of the microgrid and the power generation cost in the mode are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cThe power consumed by the combined cooling, heating and power system at the moment t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at time t for the utility company.
4. When the combined cooling heating and power system can not be profitable, the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is more than or equal to the photovoltaic output, if the current electricity price of the large power grid is the electricity price at valley time, the current time is mostly at midnight, if the energy storage residual capacity reaches the charging limit value at the moment, the energy storage battery is not charged, and the mode C4 corresponds to the mode in which the external characteristics and the power generation cost of the micro power grid are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cThe power consumed by the combined cooling, heating and power generation at the time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at time t for the utility company.
5. When the combined cooling heating and power system cannot be profitable, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is larger than or equal to the photovoltaic output, if the current electricity price of the large power grid is the electricity price at the valley time, and if the remaining energy storage capacity at the moment does not reach the charging limit value, the energy storage battery is charged, corresponding to a mode C5, the external characteristics and the power generation cost of the micro-power grid in the mode are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cPower consumed for combined cooling, heating and power at time t, pt chmCharging power for the energy storage battery at time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at the time t of the power company;
meanwhile, the power generation cost of the energy storage battery is increased to:
λt ESfor the cost of the energy storage battery at time t, EtFor the voltage of the energy-storing cell at time t, λt gThe price of electricity at time t for the power company.
6. When the combined cooling heating and power system cannot be profitable, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is greater than or equal to the photovoltaic output, if the current electricity price of the large power grid is not the electricity price at valley time, the stored energy residual quantity reaches the discharge limit value, or the stored energy residual quantity does not reach the discharge limit value and the current electricity price of the power grid is lower than the stored energy power generation cost, the stored energy is not discharged, and corresponding to a mode C6, the external characteristics and the power generation cost of the micro power grid in the mode are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cThe power consumed by the combined cooling, heating and power generation at the time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at time t for the utility company.
7. When the combined cooling heating and power system cannot be profitable, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is greater than or equal to the photovoltaic output, if the current electricity price of the large power grid is not the electricity price at valley time, the residual energy storage amount does not reach the discharge limit value, and the current electricity price of the power grid is higher than the energy storage and power generation cost, the energy storage and power discharge correspond to a mode C7, and the external characteristics and the power generation cost of the micro power grid in the mode are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cPower consumed for combined cooling, heating and power at time t, pt dismIs the discharge power of the energy storage battery at time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tt ESThe power generation cost of the energy storage battery at the time t.
8. When the combined cooling heating and power system can be profitable, and the load demand is less than the sum of the photovoltaic output and the combined cooling, heating and power, if the energy storage residual capacity does not reach the charging limit value, and the current electricity price is lower than the energy storage power generation cost, the energy storage battery is charged with the maximum charging power, corresponding to the mode C8, in which the external characteristics and the power generation cost of the microgrid are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, pt chmFor charging the energy storage cell at time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at the time t of the power company;
meanwhile, the power generation cost of the energy storage battery is increased to:
λt ESfor the cost of the energy storage battery at time t, EtFor the voltage of the energy storage cell at time t, pt chmCharging power, lambda, of the energy storage cell at time tt gThe price of electricity at time t for the utility company.
9. When the combined cooling heating and power system can be profitable, and the load demand is less than the sum of the photovoltaic output and the combined cooling, heating and power, if the energy storage residual capacity does not reach the charging limit value, and the current electricity price is higher than the energy storage and power generation cost, the energy storage battery is charged by only utilizing the photovoltaic power generation allowance, corresponding to a mode C9, in which the external characteristics of the microgrid and the power generation cost are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, pt chmFor charging the energy storage cell at time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTIs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system.
10. When the combined cooling heating and power system can gain a profit, the load demand is less than the sum of the photovoltaic output and the combined cooling, heating and power, and the energy storage residual capacity reaches the charging limit value, the energy storage battery is not charged, corresponding to the operation mode C10, the external characteristics and the power generation cost of the micro-grid in the mode are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTAs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system.
11. When the combined cooling heating and power system can be profitable, the load demand is more than or equal to the sum of the photovoltaic output and the combined cooling, heating and power, if the current electricity price of the large power grid is the electricity price at the valley, the current time is midnight, if the residual energy of the stored energy reaches the charging limit value, the stored energy battery is not charged, and the mode C11 corresponds to the mode in which the external characteristics and the power generation cost of the micro power grid are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTAs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system.
12. When the combined cooling heating and power system can be profitable, the load demand is more than or equal to the sum of the photovoltaic output and the combined cooling, heating and power, if the current electricity price of the large power grid is the electricity price at the valley time, if the energy storage residual capacity does not reach the charging limit value at the moment, the energy storage battery is charged, and corresponding to the mode C12, the external characteristics and the power generation cost of the micro power grid in the mode are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, pt chmFor charging the energy storage cell at time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTIs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system;
meanwhile, the power generation cost of the energy storage battery is increased to:
λt ESfor the cost of the energy storage battery at time t, EtFor the voltage of the energy storage cell at time t, pt chmCharging power, lambda, of the energy storage cell at time tt gThe price of electricity at time t for the utility company.
13. When the combined cooling heating and power system can be profitable, and the load demand is greater than or equal to the sum of the photovoltaic output and the combined cooling, heating and power, if the current electricity price of the large power grid is not the electricity price at valley time and the stored energy residual electricity reaches the discharge limit value, or the stored energy residual electricity does not reach the discharge limit value and the current electricity price of the power grid is lower than the stored energy power generation cost, the stored energy is not discharged, corresponding to the mode C13, the external characteristics and the power generation cost of the micro power grid in the mode are as follows:
pt eqfor microgrid external characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTAs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system;
14. when the combined cooling heating and power system can be profitable, the load demand is greater than or equal to the sum of the photovoltaic output and the combined cooling, heating and power, if the current electricity price of the large power grid is not the electricity price at valley time, the energy storage residual capacity does not reach the discharge limit value, and the current electricity price of the power grid is higher than the energy storage and power generation cost, the energy storage and discharge correspond to a mode C14, and the appearance and the power generation cost of the micro power grid in the mode are as follows:
pt eqis a littleExternal grid characteristics (i.e. microgrid power), pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, pt dismDischarge power of the storage battery at time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tt ESThe unit generating capacity cost, lambda, of the energy storage battery at the time tGTAs unit gas cost, Vt GTNatural gas consumption for a combined cooling heating and power system;
finally, the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting, and other modifications or equivalent substitutions made by the technical solutions of the present invention by those of ordinary skill in the art should be covered within the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.
Claims (5)
1. An operation method of a grid-connected microgrid under a differentiated power price is characterized by comprising the following steps:
(1) determining the electricity price at the current time t, then calculating whether the combined cooling heating and power system can be profitable, if not, using the electric refrigerator and the electric boiler, otherwise, using the combined cooling heating and power system;
(2) under the condition that the combined cooling heating and power system cannot be profitable, comparing the sum of the load demand and the combined cooling and power demand with the magnitude of photovoltaic output, and if the sum is more than or equal to the photovoltaic output, discharging the energy storage battery or purchasing electricity from a large power grid; if the output is less than the photovoltaic output, charging the energy storage battery or selling electricity to a large power grid;
(3) under the condition that the combined cooling heating and power system can be profitable, comparing the load demand with the sum of the photovoltaic output and the combined cooling, heating and power, if the load demand is more than or equal to the sum of the photovoltaic output and the combined cooling, heating and power, discharging the energy storage battery or purchasing electricity from the large power grid, and if the load demand is less than the sum of the photovoltaic output and the combined cooling, heating and power, charging the energy storage battery or selling electricity to the large power grid;
the calculation formula of profit of the combined cooling heating and power system in the step (1) is as follows:
wherein, Vt GTConsuming natural gas quantity, lambda, for combined cooling, heating and power systemGTAs cost per unit gas, pGTFor the combined production of cold, heat and electricity,
for the electricity rate of the electric power company at time t,
represents the operating cost of using the gas turbine to supply the cold and hot loads during time t,
the electric charge which is generated by heat generation of an electric boiler and refrigeration of an electric refrigerator and is equal to the heating capacity and the refrigerating capacity required by combined cooling, heating and power generation of a gas turbine in the t-time section is represented; when the former is smaller than the latter, the combined cooling, heating and power system is profitable;
the relation between the energy storage cost and the electricity price is considered in the selection of the charging and discharging of the energy storage battery and the electricity selling and purchasing to the large power grid, the principle of low energy storage and high power generation is followed, and the SOC state of the energy storage battery is also considered; the principle of low storage and high emission is as follows: in a given time slice t, the electricity prices λ at the time t are first comparedt gAnd the unit generating capacity cost lambda of the energy storage batteryESWhen the magnitude of (d) is λES＞λt gIf the energy storage battery meets the constraint condition of charging power, the energy storage battery is charged, otherwise, the energy storage battery is discharged under the constraint condition of discharging power; the upper charging limit of the SOC of the energy storage battery is 80%, and the lower discharging limit of the SOC of the energy storage battery is 20%.
2. The method according to claim 1, wherein when the combined cooling heating and power system cannot be used for profit and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is less than the photovoltaic output, if the remaining energy storage capacity does not reach the charging limit and the current power price is lower than the energy storage and power generation cost, the energy storage battery is charged with the maximum charging power, and the external characteristics of the microgrid and the power generation cost are as follows:
pt eqfor microgrid power, pt PVFor photovoltaic output at time t, pt LLoad at time t, pt h-cPower consumed by combined cooling, heating and power system at time t, pt chmCharging power for the energy storage battery at time t, Ct eqIn order to achieve the cost of electricity generation,
the price of electricity at the time t of the power company;
meanwhile, the power generation cost of the energy storage battery is increased to:
λt ESfor the cost of the energy storage battery at time t, EtFor the voltage of the energy storage cell at time t,
the price of electricity of the power company at the moment t;
when the combined cooling heating and power system cannot be profitable, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is smaller than the photovoltaic output, if the residual energy storage capacity does not reach the charging limit value, and the current electricity price is higher than the energy storage power generation cost, the energy storage battery is charged by only utilizing the photovoltaic power generation allowance, and the external characteristics of the microgrid and the power generation cost are as follows:
pt eqfor microgrid power, pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cPower consumed by combined cooling, heating and power system at time t, pt chmCharging power for the energy storage battery at time t, Ct eqIn order to achieve the cost of electricity generation,
the price of electricity at the time t of the power company;
when the combined cooling, heating and power cannot be profitable, the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is less than the photovoltaic output, and the residual energy storage capacity reaches the charging limit value, the energy storage battery is not charged, and the external characteristics and the power generation cost of the micro-grid are as follows:
pt eqfor microgrid power, pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cThe power consumed by the combined cooling, heating and power system at the moment t, Ct eqIn order to achieve the cost of electricity generation,
the price of electricity at time t for the utility company.
3. The method according to claim 1, wherein when the combined cooling heating and power system cannot be used for profit, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is greater than or equal to the photovoltaic output, if the current power price of the large power grid is the valley time power price, the current time is midnight, if the remaining energy of the stored energy reaches the charging limit, the energy storage battery is not charged, and the external characteristics and the power generation cost of the micro-grid are as follows:
pt eqfor microgrid power, pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cThe power consumed by the combined cooling, heating and power generation at the time t, Ct eqIn order to achieve the cost of electricity generation,
the price of electricity at the time t of the power company;
when the combined cooling heating and power system cannot gain a profit, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is greater than or equal to the photovoltaic output, if the current electricity price of the large power grid is the electricity price at the valley time, if the remaining energy storage capacity at the moment does not reach the charging limit value, the energy storage battery is charged, corresponding to the mode C5, the external characteristics and the power generation cost of the micro power grid in the mode are as follows:
pt eqto be i.e. microgrid power, pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cPower consumed for combined cooling, heating and power at time t, pt chmCharging power for the energy storage battery at time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at the time t of the power company;
meanwhile, the power generation cost of the energy storage battery is increased to:
λt ESfor the cost of the energy storage battery at time t, EtFor the voltage of the energy-storing cell at time t, λt gThe price of electricity at the time t of the power company;
when the combined cooling heating and power system cannot be profitable, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is greater than or equal to the photovoltaic output, if the current electricity price of the large power grid is not the electricity price at valley time, the stored energy residual electricity reaches the discharge limit value, or the stored energy residual electricity does not reach the discharge limit value and the current electricity price of the power grid is lower than the stored energy power generation cost, the stored energy is not discharged, and the external characteristics of the micro power grid and the power generation cost are as follows:
pt eqfor microgrid power, pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cThe power consumed by the combined cooling, heating and power generation at the time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at the time t of the power company;
when the combined cooling heating and power system can not be profitable, and the sum of the load demand and the power consumption of the electric boiler or the electric refrigerator is more than or equal to the photovoltaic output, if the current electricity price of the large power grid is not the electricity price at valley time, the residual energy storage capacity does not reach the discharge limit value, and the current electricity price of the power grid is higher than the energy storage power generation cost, the energy storage is discharged, and the external characteristics of the micro power grid and the power generation cost are as follows:
pt eqfor microgrid power, pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt h-cPower consumed for combined cooling, heating and power at time t, pt dismFor discharging energy storage battery at time tElectric power, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tt ESAnd the power generation cost of the energy storage battery at the moment t is calculated.
4. The method according to claim 1, wherein when the combined cooling heating and power system can be used to obtain a profit and the load demand is less than the sum of the photovoltaic output and the combined cooling heating and power system, if the remaining energy does not reach the charging limit and the current power price is lower than the energy storage and power generation cost, the energy storage battery is charged with the maximum charging power, and the external characteristics and the power generation cost of the microgrid are as follows:
pt eqfor microgrid power, pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, pt chmCharging power for the energy storage battery at time t, Ct eqLambda being the cost of electricity generationt gThe price of electricity at the time t of the power company;
meanwhile, the power generation cost of the energy storage battery is increased to:
λt ESfor the cost of the energy storage battery at time t, EtFor the voltage of the energy storage cell at time t, pt chmCharging power, lambda, of the energy storage cell at time tt gThe price of electricity at the time t of the power company;
when the combined cooling heating and power system can be profitable, the load requirement is less than the sum of the photovoltaic output and the combined cooling, heating and power, if the residual energy does not reach the charging limit value, and the current electricity price is higher than the energy storage and power generation cost, the energy storage battery is charged only by utilizing the photovoltaic power generation allowance, and the external characteristics and the power generation cost of the microgrid are as follows:
pt eqfor microgrid power, pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, pt chmCharging power for the energy storage battery at time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTAs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system;
when the combined cooling heating and power system can gain a profit, the load demand is less than the sum of the photovoltaic output and the combined cooling heating and power, and the energy storage battery is not charged when the energy storage residual capacity reaches the charging limit value, the external characteristics of the micro-grid and the power generation cost are as follows:
pt eqfor microgrid power, pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTAs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system.
5. The method according to claim 1, wherein when the combined cooling heating and power system can be used for profit and the load demand is greater than or equal to the sum of the photovoltaic output and the combined cooling heating and power system, if the current large grid power rate is the valley power rate, the current time is midnight, if the remaining energy of the stored energy reaches the charging limit, the energy storage battery is not charged, and the external characteristics of the micro-grid and the power generation cost are as follows:
pt eqfor microgrid power, pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTAs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system;
when the combined cooling heating and power system can be profitable, the load demand is more than or equal to the sum of photovoltaic output and combined cooling, heating and power, if the current electricity price of the large power grid is the electricity price at the valley time, if the energy storage residual capacity does not reach the charging limit value at the moment, the energy storage battery is charged, and the external characteristics of the micro power grid and the power generation cost are as follows:
pt eqfor microgrid power, pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, pt chmCharging power for the energy storage battery at time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTAs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system;
meanwhile, the power generation cost of the energy storage battery is increased to:
λt ESfor the cost of the energy storage battery at time t, EtFor the voltage of the energy storage cell at time t, pt chmCharging power, lambda, of the energy storage cell at time tt gThe price of electricity at the time t of the power company;
when the combined cooling heating and power system can be profitable, the load demand is more than or equal to the sum of the photovoltaic output and the combined cooling heating and power, if the current large power grid electricity price is not the valley time electricity price, the stored energy residual electricity quantity reaches the discharge limit value, or the stored energy residual electricity quantity does not reach the discharge limit value and the current power grid electricity price is lower than the stored energy power generation cost, the stored energy is not discharged, and the external characteristics of the micro power grid and the power generation cost are as follows:
pt eqfor microgrid power, pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tGTAs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system;
when the combined cooling heating and power system can be profitable, the load demand is more than or equal to the sum of photovoltaic output and combined cooling, heating and power, if the current electricity price of the large power grid is not the electricity price at valley time, the energy storage residual electricity quantity does not reach the discharge limit value, the current electricity price of the power grid is higher than the energy storage power generation cost, the energy storage is discharged, and the external characteristics of the micro power grid and the power generation cost are as follows:
pt eqfor microgrid power, pt PVFor the photovoltaic output at time t, pt LLoad at time t, pt GTThe combined cooling, heating and power output at the time t, pt dismIs the discharge power of the energy storage battery at time t, Ct eqLambda being the cost of electricity generationt gIs the electricity price, lambda, of the utility at time tt ESThe unit generating capacity cost, lambda, of the energy storage battery at the time tGTAs unit gas cost, Vt GTNatural gas is consumed for a combined cooling heating and power system.
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