Example 1
In the embodiment, a user-side distributed energy system is established, including an energy production unit model, an energy conversion unit model and a hybrid energy storage unit model, and the user-side distributed energy system is integrally described based on a universal bus model.
The established energy production unit model comprises the following steps: gas boiler model, combined cooling heating and power unit model and photovoltaic power generation device model specifically do:
1) gas Boiler (GB)
The gas boiler uses natural gas as fuel and liquid as medium to transmit heat energy, and is a common heating device in a distributed energy system, and a model of the gas boiler can be represented by formula (1):
Ht GBΔt=Ft GBηGB (1)
wherein Ht GBIndicating the thermal power provided to the load by the gas boiler at the time t; ft GBRepresenting the fuel heat energy consumed by the gas boiler burning natural gas; etaGBIs the working efficiency of the gas boiler. Meanwhile, the gas boiler output power level limit may be expressed as formula (2), where HR GBIs the rated power of the gas boiler:
2) combined cooling, heating and power units (CCHP)
The CCHP unit mainly comprises a generator and a bromine cooling machine. Firstly, natural gas is combusted in a micro gas turbine to do work, the released high-grade energy is used for producing electric energy, and simultaneously, waste heat recovery and utilization are carried out on the discharged high-temperature flue gas in a bromine refrigerator to supply cold and heat load requirements of a user side. The cold/heat coupling relation of the combined cold and heat and power supply unit can be expressed as a mathematical function relation of the power supply quantity and the heat supply/cold quantity of the unit with respect to the fuel consumption quantity. To simplify the problem, the present disclosure uses a simplified linear model, assuming that the amount of cooling and heating is constant for each amount of power produced by the cogeneration unit, using αCCHP1Expressing the heating coefficient of the bromine refrigerator by using alphaCCHP2Expressing the heating coefficient of the bromine refrigerator, and using etaCCHPRepresents a gas-to-electric conversion ratio:
meanwhile, the output power level limit of the unit during operation can be expressed as formula (4):
wherein, Pmin CCHPRepresenting the lower limit of the output power of the combined supply unit; pmax CCHPRepresents the upper limit of the output power of the cogeneration unit.
3) Photovoltaic power generation (PV)
The photovoltaic output is mainly determined by the comprehensive intensity of the light irradiated on the photovoltaic surface, the system operation condition, the photovoltaic physical parameters and the like. In general, the output characteristic of a photovoltaic device can be described by a P-G curve, where P represents the output power of the photovoltaic device and G represents the illumination intensity.
In the formula (f)PVThe power derating factor of the photovoltaic is used for representing the reduction of the output power caused by the factors such as dust and dirt on the surface of the photovoltaic, aging and the like, and is generally 0.9; pPV,RIs the photovoltaic peak capacity (kWp), GTIs the actual illuminance (kW/m)2),GT,STCThe illuminance under standard test conditions is generally 1kW/m2;αpAs power temperature coefficient (%/deg.C), TcellSurface temperature (. degree. C.) for the current photovoltaic system, Tcell,STCFor photovoltaic temperature under standard test conditions, 25 ℃ is typically taken.
As can be seen from the formula (5), the photovoltaic surface temperature has a certain influence on the photovoltaic output, and under the normal condition, the photovoltaic operation efficiency can be increased along with the photovoltaic surface temperatureHigh and low. Photovoltaic surface temperature TcellDepending on the ambient temperature, it can be calculated by:
in the formula, TaIs the ambient temperature (. degree. C.), Tcell,NOCTThe photovoltaic surface temperature under the standard operation condition is generally 45-48 ℃, wherein the standard operation condition refers to standard illuminance GT,NOCT(generally 0.8kW/m is taken2) Standard ambient temperature Tα,NOCTThe temperature is 20 ℃, and the wind speed is 1 m/s; etaMPP,STCIs the photovoltaic efficiency under standard test conditions, τ being the solar energy transmittance of the photovoltaic covering, αSIs the solar absorptance of the photovoltaic, i.e. the ratio of the photovoltaic surface capable of absorbing solar energy,. tau.alpha.SIs 0.9.
The established energy conversion unit model comprises the following steps: the heat pump model, the electric refrigerator model and the absorption refrigerator model are specifically as follows:
1) heat Pump (HP)
The ground source heat pump exchanges heat with soil, so that the exchange efficiency is higher than that of air exchange equipment such as an air conditioner. The heat pump can be driven to work by a small amount of electric energy, and the heat pump utilizes the shallow geothermal heat energy to transfer the heat energy from the low-temperature source to the high-temperature source, so that the energy utilization efficiency is high. The input-output relationship can be expressed as:
wherein, Pt HPThe electric power is input to the ground source heat pump at the moment t; ht HPThe heat power provided by the ground source heat pump to the load; etaHPThe heating coefficient of the ground source heat pump. Meanwhile, the limitation of the input electric power of the ground source heat pump can be expressed as formula (8):
2) electric refrigerator (EC)
The electric refrigerator uses electric energy to refrigerate and provides cold load for users of the system, and the energy exchange medium is air, so the efficiency of the electric refrigerator is lower than that of a ground source heat pump. The input-output relationship can be expressed as:
wherein, Ct ECCold energy provided to the load by the electric refrigerator; etaECIs the refrigeration coefficient; pt ECThe electric refrigerators input electric energy respectively. Meanwhile, the limit of the input electric power of the electric refrigerator can be expressed as formula (10):
wherein,
the rated input electric power of the electric refrigerator.
3) Absorption refrigerator (EC)
The absorption refrigerator provides cold energy by consuming heat energy, and the input and output energy relation of the absorption refrigerator is as follows:
wherein, Ct AC,outRepresents the cold power supplied to the load by the absorption chiller; ht AC,inIs the input thermal power; hR AC,inRepresenting the upper limit of the heat input power of the absorption refrigerator; etaACSystem for indicating absorption refrigeratorAnd (4) cooling efficiency.
The established hybrid energy storage unit model comprises the following steps: storage battery energy storage unit model and heat accumulation unit model specifically do:
1) storage battery energy storage unit model
In this embodiment, the lead-acid battery is used, and the function of the battery is similar to that of a container capable of storing energy, the charging process of the battery, namely the process of injecting electric energy into the container, and the discharging process of the battery, namely the process of outputting electric energy from the container, are reversible. The interior of the battery is not ideal, ohmic internal resistance and polarization internal resistance exist, and side reactions occur near the electrode along with the progress of the chemical reaction of the battery in the charging and discharging processes of the battery, which causes the energy loss of the battery in the charging and discharging processes, and how much energy can be output without inputting how much energy, in the embodiment, eta is adoptedech、ηedisThe process is expressed by respectively representing the charge and discharge efficiency of the battery.
The storage battery can generate energy loss when not put into use and still stand, because a small amount of electrons exist in the battery, partial short circuit is formed as a result of electrotransport operation, the phenomenon is the self-discharge phenomenon of the battery, and the self-discharge phenomenon of the battery mainly occurs in the cathode of the battery and the PbSO of the anode of the lead-acid battery because the active substance of the cathode material of the battery is active4Is a strong oxidant, so that the self-discharge phenomenon of the anode is very little. If metal impurities exist on the surface of the negative electrode of the storage battery, when the potential of the metal impurities is lower than that of hydrogen, a corrosive microbattery is formed at the negative electrode of the storage battery, the negative electrode material is dissolved for a long time, and the capacity of the lead-acid battery is attenuated for a long timeESThis process is shown.
In this embodiment, a linear model is used to process a storage battery energy storage unit model, the energy loss of the energy storage device is considered in the model, and the model expression is obtained as formula (13) when the charging and discharging energy loss is in use:
wherein E ist ESRepresenting the stored electrical energy at time t; pt ES,chRepresents the charging power of the power storage device at time t; pt ES,disRepresents the discharge power of the power storage device at time t; etaechIndicating the charging efficiency of the power storage device; etaedisIndicating a discharge efficiency of the electrical storage device; mu.sESRepresents the electric energy dissipation rate of the electric storage device, i.e., the self-discharge rate of the battery; Δ t represents the time period of charge and discharge. The upper and lower limits of the charge and discharge power of the battery can be expressed by equation (14):
wherein, Pmax ES,chRepresents a maximum value of the energy storage device charging power; pmax ES,disThe maximum value of the discharge power of the energy storage device is shown, except that the energy storage device is constrained in output, and the energy storage state, namely the charge state, is correspondingly constrained. State of charge σt ESIs defined as follows, QESThe rated capacity, i.e., the mounting capacity, of the battery is expressed:
there is a state of charge constraint:
wherein σES min、σES maxThe minimum and maximum state of charge of the storage battery. For convenience of description, the ratio of the maximum charge/discharge power to the rated energy storage capacity is defined as the charge/discharge rate (h-1)。ξES,ch maxIndicating storage batteryMaximum charge and discharge rate (h-1),ξES,dis maxRepresents the minimum charge-discharge rate (h-1) Namely:
the capacity fading phenomenon can occur in the process of recycling the battery, and the capacity fading caused by frequent charging and discharging is particularly obvious. In order to avoid this, the number of times the battery is charged and discharged must be limited, and the battery is not allowed to be charged and discharged frequently during the use period:
in summary, the constraints of the battery model are as follows:
because the charging and discharging states of the energy storage equipment can not occur simultaneously, the parameter chi is usedES,disHexix-ES,chIndicating the operating state of the battery. Chi shape ES,dis1 represents the discharge state of the battery, χES,chA 1 indicates that the battery is in a charged state, and both cannot be 1 at the same time. Parameter YES,disAnd YES,chRepresenting the battery discharge transition state variable and the charge transition state variable. A value of 1 indicates that the battery state is switched, and both cannot be 1 at the same time. N is the total number of charging interconversion in the planning period.
2) Heat storage system (HS)
Sensible heat energy storage is typical cold/heat energy storage mode, and sensible heat energy storage low cost, the operation is maintained simply, and the vertical cylindrical storage tank of a tape button head that the embodiment chose the heat storage tank to be sold as hot energy storage equipment on the market, and the water tank adopts 20 centimetres flexible polyurethane foam insulation, and coefficient of heat conductivity is 0.04W/m K. The external working characteristics of the heat storage tank are similar to those of the storage battery, and the energy dissipation of the energy storage device and the charging and discharging processes in the using process also need to be considered. The model can be represented as:
the heat storage tank model is constrained as follows:
wherein S is
t HSRepresenting the thermal energy stored at time t; h
t HS,chRepresenting the charging power of the heat storage equipment at the moment t;
represents the heat release power of the heat storage device at time t; eta
hchRepresents the charging efficiency of the thermal storage device; eta
hdisIndicating the heat release efficiency of the thermal storage device; mu.s
HSRepresents the dissipation rate of the thermal energy, i.e. the self-heat release rate; Δ t represents the length of time of heat charge and discharge; sigma
HS min、σ
HS maxRepresenting the minimum and maximum energy storage states of the heat storage tank; xi
HS,ch maxIndicates the maximum heat charge and discharge rate (h) of the heat storage tank
-1);ξ
HS,dis maxIndicates the minimum heat charging and discharging rate (h) of the heat storage tank
-1)。
The established universal bus model comprises the following steps: the electric bus power balance model, the hot bus power balance model, the cold bus power balance model and the flue gas bus power balance model specifically are as follows:
the distributed energy system is described by using a general bus type structure, and buses can be divided into the following parts according to energy transfer media: types of electricity, flue gas, steam, hot water, air, etc.; the devices can be divided into 4 types according to the functions of the devices in the energy conversion process of the system: source, conversion device, energy storage and load. Fig. 1 is a typical bus-type structure diagram of a user-side distributed energy system, and it can be seen from the diagram that the application of the universal bus-type structure clearly shows the connection mode of each device, and visually reflects the energy flow direction in the whole system and the coupling relationship of various types of energy, thereby effectively ensuring the universality and flexibility of system modeling and being helpful for analyzing the energy balance constraint of the system. The intra-system energy flow balance relationship is expressed as follows:
1) electric bus power balance equation:
Pt grid+Pt CHP+Pt PV+Pt ES,dis=Pt EL+Pt ES,ch+Pt EC (24)
wherein, each item in the equation is sequentially power grid power, output of the combined supply unit, photovoltaic power, battery discharge power, electric load, battery charging power and electric refrigerator power consumption power from left to right.
2) Thermal bus power balance equation:
wherein, each item in the equation is boiler heat production power, heat storage tank heat release power, exhaust-heat boiler heat release power, heat load power, heat storage tank heat absorption power from left to right in proper order.
3) Cold bus power balance equation:
wherein, each item in the equation is the refrigeration power of the electric refrigerator, the cold discharge power of the ice storage device and the cold load power from left to right in sequence.
4) Flue gas bus power balance equation:
wherein, each item in the equation is the flue gas power of the CHP unit, the flue gas power of the absorption refrigerator and the flue gas power of the waste heat recoverer from left to right in sequence.
In order to realize simultaneous optimal scheduling of the operation mode and the capacity configuration of a user-side distributed energy system, a hybrid energy storage optimal configuration method of the user-side distributed energy system is provided, which specifically comprises the following steps:
collecting energy cost of a user side distributed energy system and physical parameters and economic parameters of each unit device in the system;
solving the constructed double-layer optimization configuration model to obtain the optimal scheduling scheme of the system operation mode and the capacity configuration;
the double-layer optimization configuration model comprises an inner-layer scheduling optimization model and an outer-layer planning model, wherein the inner-layer scheduling optimization model takes the minimum daily economic operation cost of the system as a target, takes the system energy cost, the physical parameters and the economic parameters of each unit device in the system and the system capacity configuration output by the outer-layer planning model as input and outputs the optimization scheduling and the daily economic operation cost of the system operation mode, the outer-layer planning model takes the minimum equal-year-value cost in the whole life cycle of the system as a target, takes the physical parameters and the economic parameters of each unit device in the system and the output of the inner-layer scheduling optimization model as input and outputs a system capacity configuration scheme and the equal-year-value cost.
The double-layer optimization configuration model comprises an inner-layer scheduling optimization model and an outer-layer planning model, and specifically comprises the following steps:
and aiming at the economic index of the system, and determining the optimal hybrid energy storage configuration of the system under the condition of comprehensively considering various constraints of the system. In the process of optimization, since the scheduling strategy will have an important influence on the optimization result, the economy of the full life cycle of the device needs to be considered, and the mathematical expression is obtained as follows:
wherein, F is an objective function of the double-layer model, X is a scheduling optimization vector, Y is a planning optimization vector, A is an equality constraint set, B is an inequality constraint set, and the main constraints considered by the distributed energy system are as follows:
1) and (3) bus power balance constraint: formulas (24) - (27);
2) and (3) constraint of the equipment model: formulas (1) - (23);
decomposing the planning operation double-layer optimization problem into a combination of two optimization problems, and regarding the operation optimization problem as a sub-problem of the planning optimization problem to obtain a double-layer optimization configuration model comprising an inner-layer scheduling optimization model and an outer-layer planning model, wherein the mathematical expression of the model is as follows:
the objective function of the inner-layer scheduling optimization model is that the daily economic operation cost of the system is minimum, and the mathematical form of the objective function is expressed as follows:
wherein, X represents a scheduling decision vector, F represents an objective function, omega represents a value range of the scheduling decision vector, A is an equality constraint set, and B is an inequality constraint set, and the inequality constraint set comprises various constraints of system equipment and a system. Te e {1,2,3, …,24} in the following equation.
1) Objective function
The scheduling optimization model takes the lowest daily economic operation cost as an objective function of the model:
min F(x)=cfuel+com+cgrid (31)
wherein, cfuelRepresents the daily fuel cost; c. ComRepresents daily operating maintenance costs; c. CgridShowing dayAnd (5) the electricity purchasing cost. The units are all yuan.
The daily fuel cost refers to the daily consumption natural gas cost of the CHP combined supply unit and the gas boiler, wherein CfFor the price of natural gas:
the daily operation and maintenance cost relates to all equipment in the system, including not only the newly installed energy storage equipment, but also the existing equipment operation and maintenance cost in the system, wherein omegai,t omThe output at the moment t of the ith device; omegai omThe unit output operation and maintenance cost of the ith device is as follows:
when the local energy of the system is not enough to meet the energy demand of the system load, the commercial power needs to be bought to the power distribution network, and the electricity purchasing cost is positive at the moment; when the distributed energy of the system is sufficient and has surplus, the electric energy can be sold through the connecting line of the commercial power grid to obtain income, the electricity purchasing cost at the moment is negative, and the cost is expressed as:
wherein
Respectively the electricity purchasing quantity and the electricity price to the power grid at the moment t.
2) Equality constraint
The equality constraint conditions of the distributed energy system inner-layer scheduling optimization model based on the general bus model comprise power balance constraints of buses of the formulas (24) to (27) and equality constraints in the equipment model. In addition, the periodicity and the time interval coupling characteristic of the energy storage of the hybrid energy storage device are ensured, and the addition of an equation constraint (35) indicates that the energy storage state of the energy storage device is unchanged at the beginning and the end of the scheduling cycle:
wherein, E, S, t0、tNRespectively representing the electricity storage energy, the heat storage energy, the initial time of the scheduling period and the end time of the scheduling period.
3) Inequality constraint condition
The inequality constraint conditions of the distributed energy system inner-layer scheduling optimization model based on the universal bus model comprise inequality constraints of equipment models in formulas (1) to (23), and specifically comprise the following steps: the output of the energy production unit is within the upper and lower limit ranges of the output; the input power of the energy conversion unit does not exceed the upper limit of the allowable input power; the stored energy of the hybrid energy storage unit is between the maximum and minimum allowed stored energy, and the charge and discharge power or the heat and discharge power does not exceed the maximum allowed charge and discharge power or the heat and discharge power. In addition, power constraints of the system and the tie lines of the distribution network need to be considered, and the constraints are caused by line construction and other reasons:
wherein,
represents the maximum value of tie-line let-through power;
and the minimum value of the tie line power is represented, wherein the minimum value can be negative, and the positive and negative of the tie line power respectively represent the purchase of electricity and the sale of electricity.
4) Optimizing variables
Optimization variable X of scheduling period tnThe method comprises the following steps of purchasing and selling electric quantity for the output of various devices in the system and the power grid:
and carrying out dimension reduction simplification on the variables by using independent equality constraints in the equality constraint set. Considering the device model, the input and output variables of the energy conversion device may be eliminated, and then the optimal variable at the final scheduling time t is:
in conclusion, an inner-layer scheduling optimization model can be obtained, and the specific expression of the scheduling optimization of the single-target distributed energy system is as follows:
the above problem is expressed as a general form of a 0-1 mixed integer linear programming model:
in optimizing vector XnIn (1), the energy storage amount [ E ] in the t period is increasedt ES,St HS]With the convenient model programming, the final optimization variables can be obtained as:
the objective function of the outer layer planning model is a single-objective optimization model constructed with minimum equal-annual-value cost in the whole life cycle of the system.
The objective function with the minimum equal-year-number cost in the whole life cycle of the system is as follows:
min F(z)=Ccap+Cfuel+Com+Cgrid (42)
wherein, CcapRepresenting the equal annual value investment cost of the energy storage equipment; cfuelIndicating annual fuel compositionThen, the process is carried out; comRepresents the annual operating maintenance cost; cgridThe unit represents the annual electricity purchasing cost.
The equal-year-number investment cost is the cost for purchasing and installing the storage battery and the heat storage tank in the system, and the investment cost can be changed into the equal-year-number according to the service life of the system, wherein the storage battery investment cost comprises the cost of the converter. The investment cost is a function of the installation capacity and the cost per unit capacity, which can be expressed as:
wherein psiiA capital recovery rate for the energy storage device; gamma is the discount rate; liExpected value of the operating life of the energy storage device is year; qi is the installation capacity of the energy storage device; omegai capIs the cost per unit capacity of the energy storage device.
The annual fuel costs are expressed as follows:
the annual operating maintenance costs are as follows:
the annual electricity purchase cost is expressed as:
the constraints of the outer planning model include:
(1) the daily economic operation cost of the system obtained by the inner-layer scheduling optimization model is the minimum.
(2) There is a constraint on energy storage investment capacity, limited by the system site, where Q represents the installed capacity of the energy storage:
the inner-layer scheduling optimization model and the outer-layer planning model are combined to form a double-layer optimization configuration model, the relation between the inner-layer scheduling optimization model and the outer-layer planning model is shown in fig. 2, the optimized scheduling and daily economic operation cost of the system operation mode output by the inner-layer scheduling optimization model serves as the input of the outer-layer planning model, and the system capacity configuration output by the outer-layer planning model serves as the input of the inner-layer scheduling optimization model.
Solving the outer layer planning model by adopting a genetic algorithm, wherein the genetic algorithm is an intelligent algorithm, and the specific flow is shown in figure 3:
the method comprises the following steps: data initialization: the method comprises the input of system composition and structure parameters, equipment model parameters and genetic algorithm parameters.
Step two: population initialization: an initial population is randomly generated, wherein each individual corresponds to a dispatch plan within a dispatch period.
Step three: and calculating the fitness of the population individuals according to various groups of individuals, wherein the fitness of each individual corresponds to the economic cost of one scheduling period.
Step four: and transferring the individual fitness of the population to an optimization module, and obtaining the offspring population through championship selection, single-point crossing and uniform variation operation.
Step five: and returning to the step three until the requirement of the maximum genetic algebra is met. And outputting a final scheduling optimization scheme and the optimal economic cost.
In the embodiment, a user-side distributed energy system model is established, and comprises an energy production unit, a conversion unit and a hybrid energy storage unit model; the hybrid energy storage optimization configuration method for the user-side distributed energy system for the renewable energy consumption is provided, the electricity/heat hybrid energy storage system is optimally configured in the whole life cycle, under the condition of high-proportion renewable energy access, the electricity/heat hybrid energy storage of the user-side distributed energy system is optimally configured, the hybrid energy storage capacity and the system operation mode are simultaneously optimized by using a double-layer optimization configuration method, the electricity/heat hybrid energy storage cooperative optimization configuration is realized, and the important application value is realized for improving the system economy and the renewable energy consumption level.
The optimal configuration method for the hybrid energy storage of the user-side distributed energy system is applied to the planning of the hybrid energy storage of the user-side distributed energy system shown in fig. 4, load data is obtained from a medium-scale user distributed energy system, the system adopts an operation mode of cooling in summer and heating in winter, and the load types comprise three loads of cold, heat and pure electricity. Wherein, the pure electric load comprises the loads of laboratory electricity, fire-fighting electricity, office building illumination and the like; the heat load is a heating load in winter; the cooling load mainly includes the summer system building refrigeration. The bus-type structure of the system is shown in FIG. 5. The CCHP combined supply unit supplies cold and power in summer; heat supply and power supply in winter. The photovoltaic system, the CCHP system, the heat pump system and the electric refrigerator system are existing devices of the system, the capacity of the existing devices is known, the heat storage tank and the storage battery are devices which need to be newly installed and configured, and the capacity of the existing devices is unknown. The heat storage tank can store heat in winter and cool in summer.
For the convenience of system analysis, the project year is selected to be 10 years, and the annual interest rate is selected to be 0.06. The maximum photovoltaic output can reach 500kW, and the system has high renewable energy permeability. The population size of the genetic algorithm is set to 40 individuals, the maximum iteration number is set to 20 generations, and the crossover and mutation probabilities of genetic operators are set to 0.9 and 0.4 respectively. The example divides a year into three quarters: summer, winter, spring/autumn. Each quarter is divided into a working day and a rest day, each typical day takes one hour as the data sampling length, 24-6 groups of data represent the data conditions of the whole year, and fig. 6 to 8 show the load conditions and photovoltaic output conditions of three quarters. The economic and physical parameters of the equipment in the system are shown in tables 1 and 2, respectively.
TABLE 1 economic parameters of the plant
TABLE 2 physical parameters of the devices
TABLE 3 time of use price
In this case, the connection power of the distributed energy system and the power grid is set to be incapable of being delivered reversely, namely, the system is not allowed to sell electricity to the power grid, and the price of natural gas is 3.45 yuan/m3The price per heating value is 0.349 (yuan/kWh), and the electricity rate scheme adopts time-of-use electricity rates, as shown in table 3.
The outer layer of the constructed model is used for planning the capacity of the system for installing the electricity/heat mixed energy storage, the optimization variable is the capacity of the electricity storage and the heat storage, the time scale is the full life cycle, and the objective function is the minimum equal-year-value total cost of the distributed energy system after the energy storage equipment is installed. The inner-layer model is combined scheduling and is used for optimizing scheduling values of the energy storage equipment and other equipment in a typical scene of the system, the optimization variables are output of the stored energy of the electric power storage and the scheduling values of the other equipment, the time scale is a typical day, and the objective function is to minimize daily scheduling cost of the system after the energy storage equipment is installed. i ∈ {1,2,3,4,5,6} respectively 6 devices in the system, the device type is shown in fig. 4; d e {1,2,3} represents three quarters, respectively, m e {1,2} represents weekday, respectively, Nd,m,Days representing a typical season:
in order to research the internal relation and influence factors of the electricity/heat energy storage configuration, various scene analyses are carried out, and different scenes represent different original configuration conditions of the system. The CCHP unit selects an internal combustion engine with the rated capacity of 250 kW. The capacities of the CCHP, the heat pump and the electric refrigerator in the data table are the existing data of the system, and the capacities of the storage battery and the heat storage tank are the energy storage capacity optimization configuration results. The economics of the configuration scheme were evaluated using "cost savings" as an indicator. It is defined as: the cost saving is initial energy storage investment + total operation cost of the system after energy storage investment for 10 years-total operation cost of the system before energy storage investment for 10 years. As can be seen from table 4, light abandoning phenomena occur in summer, spring and autumn before the system is configured to store energy, and the renewable energy consumption capability of the system under the configuration scheme is evaluated by using the light abandoning rate as an index, which is defined as: the light rejection rate is (photovoltaic power generation amount-load actually consumed photovoltaic power amount)/photovoltaic power generation amount. The energy storage configuration results under different scenarios are shown in table 4.
Table 4 hybrid energy storage configuration results
As can be seen from fig. 9 and 10:
1. the whole hybrid energy storage works in a mode guided by electricity price, namely, the charging and discharging states of electricity price valley period, peak period and flat period are determined by the electricity price and the load condition at the front moment and the back moment, so that the effect of reducing the difference between the peak period and the valley period of the electric heating load is achieved, and the hybrid energy storage participates in the joint cooperative scheduling of the system. The system adopts an electric power storage and heat storage coordination energy storage strategy, so that the system can work in a thermoelectric decoupling state, and the flexibility of system scheduling is improved. The coordinated electrical/thermal configuration also facilitates the complementary energy flow of the system. Thus, the configuration of hybrid energy storage can effectively improve the ability of the system to consume renewable energy.
2. The surplus photovoltaic electric quantity in summer is preferentially utilized by the electric refrigerator for cold accumulation, and the surplus photovoltaic electric quantity is stored by the storage battery according to the load and the electricity price. The energy conversion device in the distributed energy system facilitates the cooperative configuration of electricity storage and heat storage/cold storage. The heat pump/refrigerator electric heating/cooling realizes energy conversion, and the heat storage tank can store heat energy. Since the heat/cold storage cost is lower than the electricity storage cost, the heat/cold storage uses renewable energy and low-priced electricity in preference to electricity storage. However, the process is a process of converting high-quality energy into low-quality energy, and cannot be performed without limitation, the heat/cold self-loss is larger than the power storage self-loss, and the system can avoid the situation that the stored energy is kept still after the energy storage equipment is charged as far as possible, and selects a mode of charging and discharging, so that the stored energy needs to be comprehensively determined according to the conditions such as the electricity price and the load condition at the previous moment and the next moment. The storage battery can directly store redundant photovoltaic power generation, but the storage capacity is mainly limited by economy due to high cost of electric energy storage.
3. The energy stored in the heat storage tank comes from low price purchase and electric heating/cold storage by utilizing photovoltaic power generation and CCHP heat/cold direct storage. In summer, when the photovoltaic output is large and the photovoltaic electric quantity is residual, the electric refrigerator works to preferentially utilize the photoelectricity to perform electric refrigeration, and the renewable energy is consumed to store energy.
4. The storage battery energy storage comes from direct storage of low-price electricity and photovoltaic output elimination, and the storage battery is charged in a time period of 5:00-7:00 and 16:00-18:00 with lower electricity price and then discharged in a time period of 7:00-9:00 and 18:00-20:00 with higher electricity price and higher load. In summer and spring/autumn, the storage battery can absorb surplus photovoltaic electric quantity for storage in the middle and middle time period of the rest photovoltaic electric quantity. The output of the storage battery in summer is higher than that of the storage battery in other seasons.