Two-stage economic dispatch method for islanded microgrid with multiple types of loads

Abstract

The application discloses a two-stage economic dispatching method for an island micro-grid containing multiple types of loads, and designs a two-stage optimization control algorithm composed of a power generation unit dispatching and load dispatching, the micro-grid contains renewable energy, traditional energy, a battery, important loads, transferable loads, interruptible loads, and considers wind and light abandonment operation under oversupply condition, in the first stage (power generation unit dispatching stage), important loads, transferable loads, interruptible loads and wind and light abandonment amount are normalized into power supply gap amount (or power amount overflow amount), a dynamic model formed by augmented states such as state of charge and power supply gap is established, the total operation cost of each device of the micro-grid is dynamically optimized, the traditional energy power generation amount, the battery charging and discharging amount and the power supply gap amount are calculated, in the second stage (load dispatching stage), the power supply gap value calculated in the first stage is distributed to the transferable loads, the interruptible loads and the wind and light abandonment amount through static optimization.

Description

TECHNICAL FIELD

[0001] The present application relates to an island micro-grid economic dispatch method, and particularly relates to a two-stage economic dispatch method for an island micro-grid containing multiple types of loads. BACKGROUND

[0002] With renewable energy and distributed power continuously accessing the power grid, power quality and reliability of power supply have been widely concerned. Micro-grid, as an effective way of consumption, realizes high-reliable supply of multiple energy forms of loads, making the access of distributed power more flexible and efficient. Micro-grid is usually composed of micro-sources, energy storage units and loads, and is an autonomous system with self-control and self-energy management, which can realize self-sufficient operation mode of generation, distribution and consumption, and can flexibly switch between grid-connected operation and island operation.

[0003] For the island micro-grid containing multiple types of loads, considering the influence of optimal allocation of multiple load resources on micro-grid economic optimization, the problem that it is difficult to balance different power demands of multiple types of loads and abandoned wind and light operation of renewable energy can be solved. At present, the energy management of micro-grid containing renewable energy, traditional energy, battery, important load, transferable load and interruptible load usually has the technical problems of high computational complexity and long calculation time. SUMMARY

[0004] This section is intended to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, the abstract and the title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0005] In view of the above problems of the existing two-stage economic dispatch method for island micro-grid containing multiple types of loads, the present application is proposed.

[0006] Therefore, the purpose of the present application is to provide a two-stage economic dispatch method for island micro-grid containing multiple types of loads.

[0007] To solve the above technical problems, the present application provides the following technical solutions: comprising the following steps,

[0008] constructing an island micro-grid model containing multiple types of loads, and describing an optimization problem;

[0009] In the first stage, based on the power supply gap augmented state model, real-time tracking and calculation of power supply gap value are performed; and

[0010] In the second stage, the power supply gap value calculated in the first stage is allocated to the electricity transfer amount of the transferable load, the operation state of the interruptible load and the wind and light abandoned amount through static optimization, so as to obtain the allocation scheme of various loads and the wind and light abandoned amount of the renewable energy.

[0011] As a preferred scheme of the two-stage economic dispatching method of the island micro-grid with multiple types of loads according to the application, the island micro-grid with multiple types of loads comprises a dynamic model formed by the state of charge and the power supply gap, which is established by normalizing the important load, the transferable load, the interruptible load and the wind and light abandoned amount into the power supply gap or overflow amount.

[0012] As a preferred scheme of the two-stage economic dispatching method of the island micro-grid with multiple types of loads according to the application, the first stage comprises the comprehensive objectives of real-time tracking of user load and minimization of total operation cost of micro-grid devices, and the total operation cost of the micro-grid system is dynamically optimized by adopting the predictive control idea, and the amount of traditional energy generation, the amount of battery charging and discharging are optimized, and the power supply gap value of the micro-grid is calculated.

[0013] As a preferred scheme of the two-stage economic dispatching method of the island micro-grid with multiple types of loads according to the application, the two-stage economic dispatching method of the island micro-grid with multiple types of loads is characterized in that: the island micro-grid with multiple types of loads comprises the following unit models:

[0014] Emt(t): the power generation of the traditional energy at time t;

[0015] Eb(t): the charging and discharging power of the battery at time t;

[0016] Ub(t): the charging and discharging state of the battery at time t, Ub(t)=1 indicates charging, and Ub(t)=0 indicates discharging;

[0017] Eimpt(t): the electricity demand of the important load at time t;

[0018] Eint(t): the electricity demand of the interruptible load at time t;

[0019] Umt(t): the start-stop state of the traditional energy generator set at time t, Umt(t)=1 indicates the start state, and Umt(t)=0 indicates the stop state;

[0020] Uint(t): the running state of interruptible load at time t, Uint(t) = 1 represents normal running, Uint(t) = 0 represents interrupting running;

[0021] Eshft(t): the electricity demand of transferable load at time t;

[0022] Eshftnum(t): the electricity transfer amount of transferable load at time t;

[0023] Erenew(t): the predicted value of power supply output of renewable energy at time t;

[0024] Espill(t): the amount of wind and light abandoned by renewable energy at time t;

[0025] Egap(t): the power supply gap inside the microgrid at time t;

[0026] Renewable energy power supply

[0027] The range of the amount of wind and light abandoned by renewable energy Espill(t) is:

[0028] 0≤E spill (t)≤E renew (t)

[0029] From the perspective of resource utilization, the main punishment for renewable energy is the behavior of abandoning wind and light, so the cost of abandoning wind and light is taken as the cost of renewable energy power supply, as follows:

[0030] C spill (t)=K spill E spill (t)

[0031] Where: K spill is the unit penalty cost coefficient of abandoned wind and light after conversion;

[0032] Controllable generator set power supply

[0033] In actual operation, the power generation of gas turbine or diesel generator has upper and lower limits, and meets certain climbing rate, and its constraint is:

[0034] U mt E mt,min ≤E mt (t)≤U mt E mt,max

[0035] ΔE mt,min ≤ΔE mt (t)≤ΔE mt,max

[0036] Wherein: Emt,min(t) and Emt,max(t) are the lower limit and upper limit of the traditional energy power generation, respectively, U mt (t) is the start-stop state, ΔEmt(t) is the ramp rate of the traditional energy power generation at time t, ΔEmt,min and ΔEmt,max are the lower limit and upper limit of the traditional energy power generation ramp rate, respectively,

[0037] The function relationship between the traditional energy generation cost and the unit output is

[0038] C mt1 (t) = K q (E mt (t)) 2 + K l E mt (t) + K c E mt (t)

[0039] Wherein: K q is the quadratic term cost coefficient, K l is the linear term cost coefficient, and K c is the constant term cost coefficient.

[0040] The start-stop cost of the traditional energy generator

[0041] C mt2 (t) = K s U mt (t)(1-U mt (t-1)) + K d (1-U mt (t))U mt (t-1)

[0042] Wherein: K s and K d are the start-stop cost, respectively.

[0043] Battery

[0044] The state of charge of the battery at time t is denoted as S(t), and the state of charge model of the battery is:

[0045]

[0046] E b (t) = E d (t) - E c (t)

[0047] S min ≤ S(t) ≤ S max

[0048] U b (t)Ec,min ≤E c (t)≤U b (t)E c,max

[0049] (1-U b (t))E d,min ≤E d (t)≤(1-U b (t))E d,max

[0050] where δ is the self-discharge rate of the battery, Ec(t) and Ed(t) are the charging and discharging power of the battery at time t, ηc and ηd are the charging and discharging efficiencies of the battery, Smin and Smax are the lower and upper limits of the state of charge of the battery, Ec,min and Ec,max are the lower and upper limits of the charging power of the battery, and Ed,min and Ed,max are the lower and upper limits of the discharging power of the battery;

[0051] To ensure the sustainability of the daily optimization process of the battery and the economic efficiency of the battery operation, the state of charge S(t) of the battery needs to return to the initial state of charge S0 at each iteration of the optimization process 0, and the state of the battery at the initial time and the terminal time is consistent, i.e.,

[0052] S 0时 =S0

[0053] S0=S end

[0054] The relationship between the operation and maintenance cost of the battery and the charging and discharging power is:

[0055] C b (t)=K b (η c E c (t)+E d (t) / η d )

[0056] where K b is the converted unit charging and discharging cost;

[0057] Let Eref(t) be the power demand of the user load at time t, and the total user load of the microgrid includes important load, transferable load and interruptible load, which satisfies the following equation:

[0058] E ref (t)=E impt (t)+E shft (t)+E int (t)

[0059] The transferable load satisfies two constraint conditions: 1) in a cycle, the total power consumption of the user is unchanged, i.e. the transferred-in load and the transferred-out load need to reach a balance; 2) the transferable load has certain uncontrollable basic load, only part of the load can be regulated, i.e. the power consumption regulation amount Eshftnum(t) has certain limitation;

[0060]

[0061] E shftnum,min ≤E shftnum shftnum,min(t)≤Eshftnum(t)≤Eshftnum,max(t) shftnum,max

[0062] In the formula, Eshftnum,min and Eshftnum,max are respectively the lower limit and the upper limit of the power consumption transfer amount of the transferable load;

[0063] When the load is transferred or interrupted, the power consumption plan will be changed, the micro-grid needs to give proper compensation, and the load transfer cost is generated:

[0064] C shft shftnum(t)=K4|Eshftnum(t)| shftnum

[0065] And the load interruption cost:

[0066] C int int(t)=K5(1-U int (t))E int int(t).

[0067] As a preferred scheme of the two-stage economic dispatching method of the island micro-grid with multiple types of loads, in the construction of the island micro-grid model with multiple types of loads, the economic objective function of the micro-grid optimization problem is:

[0068]

[0069] As a preferred scheme of the two-stage economic dispatching method of the island micro-grid with multiple types of loads, in the construction of the island micro-grid model with multiple types of loads, a dynamic model formed by the state of charge and the power supply gap is established; the total power generation of the micro-grid includes renewable energy generation, traditional energy generation and battery charging and discharging; E(t) is the total power generation of the micro-grid at t, satisfying the following equation:

[0070] E(t)=E mt (t)+E b (t)+E renew (t)

[0071] ​The power supply gap Egap(t) of the micro-grid at time t is defined as the difference between the user load and the total power generation of the micro-grid, i.e.:

[0072] E gap (t)=E ref (t)-E(t)

[0073] Subsequently, an incremental dynamic model of the power supply gap Egap(t) is established:

[0074] At time t+1, according to the expression of the power supply gap Egap(t) and the total power generation E(t), it can be known that

[0075] E gap (t+1)=E ref (t+1)-E(t+1)

[0076] E(t+1)=E mt (t+1)+E b (t+1)+E renew (t+1)

[0077] Therefore

[0078] E gap (t+1)-E gap (t)=[E ref (t+1)-E ref (t)]-[E(t+1)-E(t)]

[0079] E(t+1)-E(t)=E mt (t+1)-E mt (t)+E b (t+1)-E b (t)+E renew (t+1)-E renew (t)

[0080] The incremental power generation of the conventional energy, the incremental power generation of the storage battery, the incremental power generation of the renewable energy and the incremental user load are defined as:

[0081] ΔE mt (t)=E mt (t+1)-E mt (t)

[0082] ΔE b (t)=E b (t+1)-E b (t)

[0083] ΔE renew (t)=E renew (t+1)-E renew (t)

[0084] ΔE ref (t) = E ref (t+1) - E ref (t)

[0085] The above six formulas are integrated to obtain a dynamic model of power supply gap increment of micro-grid:

[0086] E gap (t+1) = E gap (t) + ΔE ref (t) - (ΔE mt (t) + ΔE b (t) + ΔE renew (t)).

[0087] As a preferred solution of the two-stage economic dispatch method of the micro-grid with multiple types of loads, in the first stage, a power supply gap augmented state model is designed, and an economic cost of gap amount is introduced into the original performance index of the micro-grid as a penalty term to construct a new performance index, and on this basis, an economic dispatch optimization strategy is designed to solve the optimal dispatch scheme. First, the original economic objective function of the micro-grid, i.e., the (*) formula, is converted into two-stage objective functions, which are respectively a performance index of generation unit dispatching:

[0088]

[0089] and a performance index of load dispatching:

[0090]

[0091] The performance index of the micro-grid generation unit dispatching can be further converted as follows:

[0092]

[0093] Wherein, R1 is a power supply gap cost penalty coefficient of the micro-grid.

[0094] In order to eliminate the absolute value term in the above formula, auxiliary variables Egap1(t) and Egap2(t) are introduced in this paper, and auxiliary constraint conditions are added as follows:

[0095] E gap (t) + E gap1 (t) - E gap2 (t) = 0, t = 1, 2, …, T

[0096] E gap1 (t) ≥ 0, E gap2 (t) ≥ 0

[0097] The formula can be converted into the following linear form:

[0098]

[0099] In summary, the objective function of the generation unit optimization scheduling problem of the micro-grid can be described as:

[0100]

[0101] Since the operation constraints of each unit need to be met during the operation of the micro-grid, which includes the dynamic equation of energy storage, the generation unit optimization scheduling problem belongs to a dynamic optimization problem.

[0102] As a preferred solution of the two-stage economic dispatch method of the island micro-grid with multiple types of loads according to the present application, in the second stage, the second stage load scheduling is considered. The supply-demand balance equation between the generation units of the micro-grid and the user loads is:

[0103] E(t)-E spill (t)=E impt (t)+U int (t)E int (t)+E shft (t)+E shftnum (t)

[0104] Wherein the left side of the formula represents the actual power generation of the micro-grid when the micro-grid performs the wind and light abandonment operation (if there is no wind and light abandonment operation, Espill(t) = 0 can be used), and the right side represents the actual power consumption of the micro-grid when the load interruption and load transfer are performed. The E(t) obtained in the step S1 is substituted into the supply-demand balance equation as follows:

[0105] E gap (t)=E ref (t)-E(t)

[0106] Substituting the supply-demand balance equation can obtain:

[0107]

[0108] When the transferable load is included in the micro-grid, the micro-grid can flexibly adjust the power consumption plan of the transferable load; however, the transferable load causes inconvenience to the user load due to the advance power consumption or delayed power consumption of the transferable load, and therefore, the micro-grid needs to give appropriate compensation to the user. The power consumption transfer cost Cshft(t) required in the period t has been given in the island micro-grid model with multiple types of loads in the description of the optimization problem, and for the convenience, it is shown as follows:

[0109] C shft (t)=R4|E shftnum (t)|

[0110] To eliminate the absolute value term in the above formula, auxiliary variables Eshftnum1(t), Eshftnum2(t) are introduced, and the auxiliary constraint conditions

[0111] E shftnum (t) + E shftnum1 (t) - E shftnum2 (t) = 0

[0112] E shftnum1 (t) ≥ 0, E shftnum2 (t) ≥ 0

[0113] It can be converted into the following linear form:

[0114] C shft (t) = R4(E shftnum1 (t) + E shftnum2 (t))

[0115] In summary, the micro-grid load scheduling problem can be converted into:

[0116]

[0117] In the load scheduling optimization problem of the above formula, there is no expression of energy storage dynamic equation, which belongs to a static optimization problem. Solving this static optimization problem can obtain a variety of load distribution schemes and renewable energy curtailment.

[0118] As a preferred solution of the two-stage economic dispatch method of the island micro-grid with multiple types of loads according to the present application, wherein: through the first stage of the generation unit optimization scheduling, the optimal values of the variables such as the traditional energy output E mt (t), the battery charging and discharging state U b (t), the battery charging and discharging power E b (t), the power supply gap value E gap (t) and the like are preferably selected, and are respectively marked as Then, the traditional energy output, the battery charging and discharging state and the charging and discharging power are executed according to the guidance of the optimization solution; and the classification operation is performed according to whether the gap value is 0 or not:

[0119] If , the second stage optimization is not needed, and the electricity transfer amount Eshftnum(t) = 0 of the transferable load, the operation state Uint(t) = 1 of the interruptible load and the renewable energy curtailment Espill(t) = 0 are directly assigned.

[0120] If , further load scheduling needs to be taken for the gap value The distribution is performed among the transferable load electricity transfer amount Eshftnum(t), the operation state of the interruptible load Uint(t), and the wind and light abandoned amount Espill(t).

[0121] The beneficial effects of the present application are as follows: in the first stage, the user load is tracked in real time, the operation cost of each power generation device is dynamically optimized, and the specific value of the power supply gap of the micro-grid is calculated explicitly; in the second stage, based on the power supply gap value obtained in the previous stage, the transferable load electricity transfer amount, the operation state of the interruptible load, and the wind and light abandoned amount are statically optimized, the calculation burden is effectively reduced, and the different electricity demand of various types of loads is met. BRIEF DESCRIPTION OF DRAWINGS

[0122] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor. Among them:

[0123] Figure 1 The figure is a flowchart of the two-stage economic dispatching method of the island micro-grid with multiple types of loads according to the present application.

[0124] Figure 2 The figure is a schematic diagram of the island micro-grid structure with multiple types of loads according to the two-stage economic dispatching method of the island micro-grid with multiple types of loads according to the present application.

[0125] Figure 3 The figure is a simulation result diagram of the battery state of charge in the embodiment of the two-stage economic dispatching method of the island micro-grid with multiple types of loads according to the present application.

[0126] Figure 4 The figure is a simulation result diagram of the battery state of charge in the embodiment of the two-stage economic dispatching method of the island micro-grid with multiple types of loads according to the present application.

[0127] Figure 5 The figure is a simulation result diagram of the battery state of charge in the embodiment of the two-stage economic dispatching method of the island micro-grid with multiple types of loads according to the present application.

[0128] Figure 6 The figure is a simulation result diagram of the battery state of charge in the embodiment of the two-stage economic dispatching method of the island micro-grid with multiple types of loads according to the present application.

[0129] Figure 7The simulation result chart of the abandoned wind power and abandoned light power in the embodiment of the two-stage economic dispatch method of the island micro-grid with multiple types of loads.

[0130] Figure 8 The simulation result chart of the electricity transfer amount of the transferable load in the embodiment of the two-stage economic dispatch method of the island micro-grid with multiple types of loads (positive value means early electricity use, negative value means delayed electricity use).

[0131] Figure 9 The simulation result chart of the operation state of the interruptible load in the embodiment of the two-stage economic dispatch method of the island micro-grid with multiple types of loads (0 represents load interruption, and 1 represents normal operation). DETAILED DESCRIPTION

[0132] In order to make the above objectives, characteristics and advantages of the present application more apparent, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0133] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced without the specific details given herein, that the present application can be practiced with other than the described embodiments, and that variations from the particular embodiments described herein can be made and still be within the scope of the present application.

[0134] Secondly, the "one embodiment" or "embodiment" referred to herein means that a specific feature, structure or characteristic can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an embodiment that is independent or alternative to other embodiments.

[0135] Thirdly, the present application is described in detail in conjunction with the schematic diagram. In the detailed description of the embodiments of the present application, the cross-sectional view of the device structure is locally enlarged without the general proportion for the convenience of description, and the schematic diagram is only an example, which should not limit the scope of protection of the present application herein. In addition, the three-dimensional spatial dimensions of length, width and depth should be included in actual manufacture.

[0136] Embodiment 1

[0137] Reference Figure 1 , provides a schematic diagram of the overall structure of a two-stage economic dispatch method of an island micro-grid with multiple types of loads, as Figure 1 A two-stage economic dispatch method of an island micro-grid with multiple types of loads includes the following steps,

[0138] Constructing an island micro-grid model with multiple types of loads, describing the optimization problem;

[0139] The first stage is based on the power supply gap extended state model to track in real time and calculate the power supply gap value; and

[0140] The second stage is to distribute the power supply gap value calculated in the first stage to the electricity transfer amount of the transferable load, the operation state of the interruptible load and the wind and light abandoned amount, that is, to obtain the distribution scheme of various loads and the wind and light abandoned amount of renewable energy.

[0141] Specifically, the island micro-grid model containing multiple types of loads specifically includes establishing a dynamic model formed by the state of charge and the power supply gap by normalizing the important load, the transferable load, the interruptible load and the wind and light abandoned amount into the power supply gap or overflow; the first stage includes taking real-time tracking of user load and minimizing the total operation cost of micro-grid devices as the comprehensive goal, dynamically optimizing the total operation cost of micro-grid system devices by using the predictive control idea, and optimizing the traditional energy generation amount, the battery charging and discharging amount, and explicitly calculating the power supply gap value of the micro-grid.

[0142] The island micro-grid model containing multiple types of loads is as follows:

[0143] Provisions:

[0144] Emt(t): the power generation of traditional energy at time t;

[0145] Eb(t): the charging and discharging power of the battery at time t;

[0146] Ub(t): the charging and discharging state of the battery at time t, Ub(t)=1 indicates charging, and Ub(t)=0 indicates discharging;

[0147] Eimpt(t): the electricity demand of important load at time t;

[0148] Eint(t): the electricity demand of interruptible load at time t;

[0149] Umt(t): the start-stop state of traditional energy generator set at time t, Umt(t)=1 indicates start state, and Umt(t)=0 indicates stop state;

[0150] Uint(t): the operation state of interruptible load at time t, Uint(t)=1 indicates normal operation, and Uint(t)=0 indicates interrupt operation;

[0151] Eshft(t): the electricity demand of transferable load at time t;

[0152] Eshftnum(t): the electricity transfer amount of transferable load at time t;

[0153] Erenew(t): the predicted value of renewable energy supply output at time t;

[0154] Espill(t): the amount of curtailed renewable energy at time t;

[0155] Egap(t): the supply gap within the microgrid at time t;

[0156] Renewable energy supply

[0157] The range of the amount of curtailed renewable energy Espill(t) is:

[0158] 0≤E spill (t)≤E renew (t)

[0159] From the perspective of resource utilization, the main punishment for renewable energy is curtailed wind and light, so the cost of curtailed wind and light is taken as the cost of renewable energy supply, which is as follows:

[0160] C spill (t)=K spill E spill (t)

[0161] Where: K spill is the unit penalty cost coefficient of curtailed wind and light after conversion;

[0162] Controllable generator supply

[0163] In actual operation, the power generation of gas turbine or diesel generator has upper and lower limits, and meets certain ramp rate, which is constrained as:

[0164] U mt E mt,min ≤E mt (t)≤U mt E mt,max

[0165] ΔE mt,min ≤ΔE mt (t)≤ΔE mt,max

[0166] In the formula: Emt,min(t) and Emt,max(t) are the lower limit and upper limit of the power generation of traditional energy, respectively, U mt (t) is the start-stop state, and ΔEmt(t) is the ramp rate of the power generation of traditional energy at time t, ΔEmt,min and ΔEmt,max are the lower limit and upper limit of the ramp rate of the power generation of traditional energy, respectively,

[0167] The functional relationship between the cost of traditional energy generation and the unit output is

[0168] Cmt1 (t) = K q (E mt (t)) 2 + K l E mt (t) + K c E mt (t)

[0169] wherein: K q is the quadratic term cost coefficient, K l is the linear term cost coefficient, and K c is the constant term cost coefficient.

[0170] Conventional energy generator set start-stop cost

[0171] C mt2 (t) = K s U mt (t)(1-U mt (t-1))+ K d (1-U mt (t))U mt (t-1)

[0172] wherein: K s and K d are start-stop machine costs, respectively.

[0173] Battery

[0174] The state of charge of the battery at time t is denoted as S(t), and the state of charge model of the battery is:

[0175]

[0176] E b (t) = E d (t) - E c (t)

[0177] S min ≤ S(t) ≤ S max

[0178] U b (t)E c,min ≤ E c (t) ≤ U b (t)E c,max

[0179] (1-U b (t))E d,min ≤ E d (t) ≤ (1-U b (t))E d,max

[0180] In the formula: δ is the self-discharge rate of the battery, Ec(t) and Ed(t) are the charging and discharging power of the battery at time t, respectively, ηc and ηd are the charging and discharging efficiencies of the battery, respectively, Smin and Smax are the lower and upper limits of the battery state of charge, respectively, Ec,min and Ec,max are the lower and upper limits of the battery charging power, respectively, and Ed,min and Ed,max are the lower and upper limits of the battery discharging power.

[0181] To ensure the sustainability and economic efficiency of the battery's daily optimized operation, the battery's state of charge S(t) needs to return to the initial state of charge S0 at the end of each optimization iteration, and the battery's state at the initial and final moments must be consistent, i.e.:

[0182] S 0时 =S0

[0183] S0 = S end

[0184] The relationship between the maintenance cost of a battery and its charging / discharging power is as follows:

[0185] C b (t)=K b (η c E c (t)+E d (t) / η d )

[0186] Where: K b This is the converted unit charge / discharge cost;

[0187] Let Eref(t) be the power demand of the user load at time t. The total user load of the microgrid includes critical loads, transferable loads, and interruptible loads, satisfying the following equation:

[0188] E ref (t)=E impt (t)+E shft (t)+E int (t)

[0189] The transferable load satisfies the following two constraints: 1) Within a cycle, the total electricity consumption of the user remains unchanged, that is, the amount of load transferred in and the amount of load transferred out must be balanced; 2) The transferable load has a certain uncontrollable base load, and only part of the load can be controlled, that is, the electricity consumption adjustment amount Eshftnum(t) has certain limitations.

[0190]

[0191] E shftnum,min ≤E shftnum (t)≤Eshftnum,max

[0192] where Eshftnum,min and Eshftnum,max are the lower and upper limits of the transferable load power shift amount, respectively;

[0193] When the load is shifted or interrupted, the power consumption plan will be changed, and the microgrid needs to give appropriate compensation, resulting in a load shift cost:

[0194] C shft (t) = K4|E shftnum (t)|

[0195] And the load interruption cost:

[0196] C int (t) = K5(1-U int (t))E int (t).

[0197] In the construction of an island microgrid model containing multiple types of loads, the economic objective function of the microgrid optimization problem is:

[0198]

[0199] In the construction of an island microgrid model containing multiple types of loads, a dynamic model is established by the state of charge and power supply gap, etc. The total power generation of the microgrid includes renewable energy generation, traditional energy generation, and battery charging and discharging. Let E(t) be the total power generation of the microgrid at time t, which satisfies the following equation:

[0200] E(t) = E mt (t) + E b (t) + E renew (t)

[0201] Define the power supply gap Egap(t) of the microgrid at time t as the difference between the user load and the total power generation of the microgrid, i.e.:

[0202] E gap (t) = E ref (t) - E(t)

[0203] Subsequently, an incremental dynamic model of the power supply gap Egap(t) is established:

[0204] At time t+1, according to the expressions of the power supply gap Egap(t) and the total power generation E(t), we have

[0205] E gap (t+1) = E ref (t+1) - E(t+1)

[0206] E(t+1) = Emt (t+1)+E b (t+1)+E renew (t+1)

[0207] Therefore

[0208] E gap (t+1)-E gap (t)=[E ref (t+1)-E ref (t)]-[E(t+1)-E(t)]

[0209] E(t+1)-E(t)=E mt (t+1)-E mt (t)+E b (t+1)-E b (t)+E renew (t+1)-E renew (t)

[0210] The incremental increase of conventional energy power generation, battery charge and discharge, renewable energy power generation, and user load are defined as:

[0211] ΔE mt (t)=E mt (t+1)-E mt (t)

[0212] ΔE b (t)=E b (t+1)-E b (t)

[0213] ΔE renew (t)=E renew (t+1)-E renew (t)

[0214] ΔE ref (t)=E ref (t+1)-E ref (t)

[0215] The above six formulas are integrated to obtain the dynamic model of the power supply gap increment of the microgrid:

[0216] E gap (t+1)=E gap (t)+ΔE ref (t)-(ΔE mt (t)+ΔE b (t)+ΔE renew (t));

[0217] In the first stage, the power gap extended state model is designed, and the gap amount economic cost is introduced into the original performance index of the micro-grid as a penalty term to construct a new performance index, on the basis of which the economic dispatch optimization strategy is designed, and the optimization dispatch scheme is solved. Firstly, the original economic objective function of the micro-grid, i.e. formula (*) is converted into two-stage objective functions, which are the performance index of the power generation unit scheduling:

[0218]

[0219] and the performance index of the load scheduling:

[0220]

[0221] The performance index of the micro-grid power generation unit scheduling can be further converted as follows:

[0222]

[0223] Wherein, R1 is the power gap cost penalty coefficient of the micro-grid.

[0224] In order to eliminate the absolute value term in the above formula, auxiliary variables Egap1(t) and Egap2(t) are introduced in this paper, and the auxiliary constraint condition is:

[0225] E gap (t) + E gap1 (t) - E gap2 (t) = 0, t = 1, 2, …, T

[0226] E gap1 (t) ≥ 0, E gap2 (t) ≥ 0

[0227] The formula can be converted into the following linear form:

[0228]

[0229] In summary, the objective function of the power generation unit optimization scheduling problem of the micro-grid can be described as:

[0230]

[0231] Since the operation constraints of each unit need to be met in the operation of the micro-grid, which contains the dynamic equation of the energy storage, the power generation unit optimization scheduling problem belongs to the dynamic optimization problem.

[0232] In the second stage, the second stage load scheduling. The supply and demand balance equation between the micro-grid power generation unit and the user load is considered as:

[0233] E(t) - E spill (t) = E impt (t) + U int(t) + E int (t) + E shft (t) + E shftnum (t)

[0234] Where the left side of the equation represents the actual power generation of the microgrid when the microgrid performs the wind and light curtailment operation (if there is no wind and light curtailment operation, Espill(t) = 0), and the right side represents the actual power consumption of the microgrid when the load interruption and load shifting are performed. The actual power consumption of the microgrid in step S1 is substituted into the supply and demand balance equation as follows:

[0235] E gap (t) = E ref (t) - E(t)

[0236] Substituting the supply and demand balance equation can obtain:

[0237]

[0238] When the microgrid contains transferable loads, the microgrid can flexibly adjust the power consumption plan of the transferable loads; however, the transferable loads cause inconvenience to the user load due to their own advance power consumption or delayed power consumption, and therefore the microgrid needs to give appropriate compensation to the user. The power consumption shifting cost Cshft(t) required in the t period is given in the island microgrid model containing multiple types of loads described in the optimization problem, and for convenience, it is shown as follows:

[0239] C shft (t) = R4|E shftnum (t)|

[0240] In order to eliminate the absolute value term in the above formula, auxiliary variables Eshftnum1(t) and Eshftnum2(t) are introduced, and the auxiliary constraint condition is as follows:

[0241] E shftnum (t) + E shftnum1 (t) - E shftnum2 (t) = 0

[0242] E shftnum1 (t) ≥ 0, E shftnum2 (t) ≥ 0

[0243] It can be converted into the following linear form:

[0244] C shft (t) = R4(E shftnum1 (t) + E shftnum2 (t))

[0245] In summary, the microgrid load scheduling problem can be converted into:

[0246]

[0247] In the load scheduling optimization problem of the above formula, the expression of the energy storage dynamic equation is not contained, which belongs to a static optimization problem. Solving this static optimization problem can obtain the allocation scheme of various loads and the amount of renewable energy curtailment.

[0248] Through the first-stage optimization scheduling of the power generation unit, the optimal values of the variables such as the output of the traditional energy E mt (t), the state of charge and discharge of the battery U b (t), the charging and discharging power of the battery E b (t), the supply gap value E gap (t) and the like are preferably selected, which are respectively marked as Subsequently, the output of the traditional energy, the state of charge and discharge of the battery and the charging and discharging power are executed with reference to the guidance of the optimization solution; and the gap value is classified according to whether the numerical value is 0:

[0249] If E shftnum(t) = 0, Uint(t) = 1 and Espill(t) = 0, the second-stage optimization is not required, and the direct assignment of the electricity shifting amount of the transferable load E

[0250] If E shftnum(t) > 0, Uint(t) < 1 and Espill(t) > 0, the load scheduling needs to be further taken, and the electricity shifting amount of the transferable load E shftnum(t), the running state of the interruptible load Uint(t) and the amount of renewable energy curtailment Espill(t) are allocated.

[0251] The specific work flow is as follows:

[0252] The two-stage economic scheduling method of the island micro-grid with multiple types of loads includes the following specific steps

[0253] (1) First stage: scheduling of the power generation unit

[0254] Step 1: At the starting time t = 0, the initial state of charge of the battery S0, the optimization time domain P, the initial value of the state variable x0, the costs R1, R2, R3, R4, R5 and R6, the initial values of the traditional energy generation power and the battery charging and discharging power Emt,0 and Eb,0 are initialized.

[0255] Step 2: The power generation prediction value of the renewable energy E

[0256] Step 3: Solve according to formula (**) under the constraint condition of meeting the micro-grid power supply equipment, to obtain the current time gap Conventional energy power generation Battery charging and discharging power Battery charging and discharging state flag logical variable The electricity transfer amount Eshft(t) of the transferable load, the operation state Uint(t) of the interruptible load, and the wind and light abandoned amount Espill(t).

[0257] Step 4: Determine whether the gap If the value is 0, if Step 5 is executed (that is, the second stage of load scheduling is executed); if Step 6 is jumped to.

[0258] (2) The second stage: load scheduling

[0259] Step 5: Refer to the power supply gap obtained by the first stage micro-grid optimization scheduling model Solve the optimization calculation (***) to update the electricity transfer amount Eshft(t) of the transferable load, the operation state Uint(t) of the interruptible load, and the wind and light abandoned amount Espill(t).

[0260] Step 6: The conventional energy power generation Battery charging and discharging power increment The electricity transfer amount Eshft(t) of the transferable load, the operation state Uint(t) of the interruptible load, and the wind and light abandoned amount Espill(t) drive the micro-grid to run.

[0261] Example 2

[0262] Referring to Figure 2 , the island micro-grid structure model researched by the present application is as shown in Figure 2 , which includes renewable energy power generation, conventional energy power generation, battery, important load, transferable load and interruptible load. The operation parameters of each power generation device of the micro-grid are shown in Table 1, the optimization time domain P is 24h, and the time interval is 15min as a short time scale rolling optimization period, so the optimization length is 96 time points. The battery state of charge S0=40, x0=[0; S0; 0; 0], Emt,0=0, Eb,0=0, δ=0.001, ηc=0.95, ηd=1.053, Smin=10, Smax=100, R1=max{R2, R3}×103, R2=0.67, R3=0.38, R4=2, R5=3, R6=1.

[0263] Table 1: Operation parameters of each device of the micro-grid system

[0264]

[0265] From the simulation results:

[0266] In the time period of 2:15-3:00 and 22:45-24:00, the output power of renewable energy is 0, and the load in the microgrid is completely supplied by traditional energy and energy storage, and the power supply gap value is greater than 0 (see Figure 5 ), that is, the total amount of power supply in the microgrid in this time period cannot meet the demand of user load. In order to reduce the economic loss caused by the power supply gap, the microgrid guides the traditional energy to supply power to the load with the maximum output, and coordinates the operation of energy storage, transferable load and interruptible load and other devices:

[0267] 1) The energy storage is discharged in the time period of 2:15-3:00 and 22:45-24:00 (see Figure 5 ).

[0268] 2) The transferable load is delayed in the time period of 2:15-2:30, 2:45-3:00 and 23:00-24:00, and is advanced in the time period of 2:30-2:45 and 22:45-23:00 (see Figure 8 ).

[0269] 3) The interruptible load stops running in the time period of 2:30-2:45 and 22:45-24:00 (see Figure 9 ), so as to reduce the power supply gap and reduce the operation cost of the microgrid.

[0270] In addition, in the time period of 11:15-12:00, the output power of renewable energy is greater than the demand value of user load, and the power supply gap value is less than 0 (see Figure 6 ). At this time, the microgrid guides the output power of traditional energy to be 0, and the load demand is completely supplied by renewable energy. In order to consume the surplus power of renewable energy, the microgrid coordinates and guides the operation of energy storage, transferable load and wind and light abandonment:

[0271] 1) The battery is charged in the time period of 11:15-11:30 (see Figure 5 ), and the battery is in a full capacity state in the time period of 11:30-12:00 (see Figure 4 ), so the battery cannot consume all the remaining power of the microgrid.

[0272] 2) In the time period of 11:15-12:00, the transferable load is further guided to use electricity in advance (see Figure 8 ).

[0273] 3) Except for the energy storage charging and the transferable load advanced electricity, there is surplus of renewable energy generation in this time period, so the wind and solar curtailment is performed simultaneously in 11:30-12:00 time period (see Figure 7 ), so as to reduce the power supply gap of microgrid and reduce the operation cost.

[0274] The calculation time and performance of the present application and the currently optimal microgrid dynamic optimization scheduling strategy based on the prediction control rolling mechanism for processing multiple types of loads are compared, and the comparison results are shown in Table 2.

[0275] Table 2 Comparison of calculation time and performance of different optimization methods

[0276]

[0277] As can be seen from Table 2, the two-stage optimization method proposed in this paper achieves almost the same economic performance as the microgrid dynamic optimization scheduling strategy based on the prediction control rolling mechanism (the performance difference is only 0.64%), and the calculation efficiency is improved by 84.3%, which significantly improves the calculation efficiency and efficiently realizes the optimization scheduling of the microgrid with lower optimization calculation amount

[0278] Importantly, it should be noted that the constructions and arrangements of the present application shown in the various exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described in this application. For example, elements shown as integrally formed can be constructed of multiple parts or elements, the position of elements can be reversed or otherwise varied, and the nature or number of elements or positions can be modified or changed. Accordingly, all such modifications are intended to be included within the scope of the application. The order or sequence of any process or method steps can be changed or re-sequenced without departing from the generality of the application. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions can be made in the design, operating conditions and arrangements of the exemplary embodiments without departing from the scope of the application. Accordingly, the present application is not limited to particular embodiments described but extends to various modifications, combinations and permutations of the described embodiments, falling within the scope of the appended claims.

[0279] Furthermore, in the interest of providing a concise description of illustrative embodiments, not all features of an actual implementation can be described (that is, not all

[0280] It will be appreciated that in the development of any actual embodiment, as in any engineering or design project, numerous implementation-specific decisions can be made. Such development efforts might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

[0281] It should be noted that the above examples are merely used to illustrate the technical solutions of the present application, not limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced, without departing from the spirit and scope of the technical solutions of the present application, and all should be covered in the scope of the claims of the present application.

Claims

1. A two-stage economic dispatch method for a microgrid containing multiple types of load islanding, characterized in that: Includes the following steps, Construct an islanded microgrid model containing various types of loads and describe the optimization problem; The first stage involves real-time tracking and calculation of the power supply gap value based on the power supply gap augmented state model, and; In the second stage, the power supply gap value calculated in the first stage is statically optimized and allocated to the transfer amount of transferable loads, the operating status of interruptible loads, and the amount of wind and solar curtailment, so as to obtain various load allocation schemes and the amount of wind and solar curtailment of renewable energy. The unit models of an islanded microgrid containing various types of loads are as follows: Regulation: Emt(t): Power generation capacity of conventional energy sources at time t; Eb(t): The charging and discharging power of the battery at time t; Ub(t): The charging and discharging state of the battery at time t. Ub(t) = 1 indicates charging, and Ub(t) = 0 indicates discharging. Eimpt(t): The electricity demand of critical loads at time t; Eint(t): The power demand of the interruptible load at time t; Umt(t): The start-up and shutdown status of the traditional energy generator set at time t. Umt(t) = 1 indicates the start-up state, and Umt(t) = 0 indicates the shutdown state. Uint(t): The operating state of the load that can be interrupted at time t. Uint(t) = 1 indicates normal operation, and Uint(t) = 0 indicates interrupted operation. Eshft(t): The electricity demand of the load that can be transferred at time t; Eshftnum(t): The amount of electricity transferred from the load that can be transferred at time t; Erenew(t): The predicted power output of renewable energy at time t; Espill(t): The amount of wind and solar power curtailed at time t; Egap(t): The power supply gap inside the microgrid at time t; Renewable energy supply The range of variation for the amount of wind and solar power curtailment (Espill(t)) is as follows: 0≤E spill (t)≤E renew (t) From a resource utilization perspective, the main penalties for renewable energy are wind and solar curtailment. Therefore, the cost of wind and solar curtailment is used as the cost of renewable energy power supply, as detailed below: C spill (t)=K spill E spill (t) Where: K spill This is the converted unit penalty cost coefficient for wind and solar power curtailment; Controllable generator set power supply In actual operation, the power output of gas turbines or diesel generators has upper and lower limits, and must meet a certain ramp rate. The constraints are as follows: U mt E mt,min ≤E mt (t)≤U mt E mt,max ΔE mt,min ≤ΔE mt (t)≤ΔE mt,max In the formula: Emt,min(t) and Emt,max(t) are the lower and upper limits of the power generation capacity of traditional energy sources, respectively, and U mt (t) represents the start-up and shutdown state, ΔEmt(t) represents the ramp-up rate of conventional energy power generation at time t, and ΔEmt,min and ΔEmt,max represent the lower and upper limits of the ramp-up rate of conventional energy power generation, respectively. The functional relationship between the cost of traditional energy power generation and the output of the generating unit is as follows: C mt1 (t)=K q (E mt (t)) 2 +K l E mt (t)+K c E mt (t) Where: K q K is the quadratic cost coefficient. l K is the cost coefficient for a primary term. c The cost coefficient is a constant term. Start-up and shutdown costs of traditional energy generator sets C mt2 (t)=K s U mt (t)(1-U mt (t-1))+K d (1-U mt (t))U mt (t-1) Where: K s K d These are the start-up and shutdown costs, respectively; Storage battery Let S(t) be the state of charge of the battery at time t. Then the state of charge model of the battery is: E b (t)=E d (t)-E c (t) S min ≤S(t)≤S max U b (t)E c,min ≤E c (t)≤U b (t)E c,max (1-U b (t))E d,min ≤E d (t)≤(1-U b (t))E d,max In the formula: δ is the self-discharge rate of the battery, Ec(t) and Ed(t) are the charging and discharging power of the battery at time t, respectively, ηc and ηd are the charging and discharging efficiencies of the battery, respectively, Smin and Smax are the lower and upper limits of the battery state of charge, respectively, Ec,min and Ec,max are the lower and upper limits of the battery charging power, respectively, and Ed,min and Ed,max are the lower and upper limits of the battery discharging power. To ensure the sustainability and economic efficiency of the battery's daily optimized operation, the battery's state of charge S(t) needs to return to the initial state of charge S0 at the end of each optimization iteration, and the battery's state at the initial and final moments must be consistent, i.e.: S 0时 =S0 S0=S end The relationship between the maintenance cost of a battery and its charging / discharging power is as follows: C b (t)=K b (or c E c (t)+E d (t) / h d ) Where: K b This is the converted unit charge / discharge cost; Let Eref(t) be the power demand of the user load at time t. The total user load of the microgrid includes critical loads, transferable loads, and interruptible loads, satisfying the following equation: E ref (t)=E impt (t)+E shft (t)+E int (t) The transferable load satisfies the following two constraints: 1) Within a cycle, the total electricity consumption of the user remains unchanged, that is, the amount of load transferred in and the amount of load transferred out must be balanced; 2) The transferable load has a certain uncontrollable base load, and only part of the load can be controlled, that is, the electricity consumption adjustment amount Eshftnum(t) has certain limitations. E shftnum,min ≤E shftnum (t)≤E shftnum,max Where: Eshftnum,min and Eshftnum,max are the lower and upper limits of the transferable load electricity transfer amount, respectively; When load shifting or interruption occurs, electricity usage plans will change, and the microgrid needs to provide appropriate compensation, resulting in load shifting costs. C shft (t)=K4|E shftnum (t)| And load interruption costs: C int (t)=K5(1-U int (t))E int (t); In the constructed islanded microgrid model containing multiple types of loads, the economic objective function of the microgrid optimization problem is:

2. The two-stage economic dispatch method for islanded microgrids containing multiple types of loads as described in claim 1, characterized in that: The islanded microgrid model containing multiple types of loads specifically includes establishing a dynamic model formed by normalizing important loads, transferable loads, interruptible loads, and wind and solar curtailment into power supply gaps or overflows, and then using augmented states such as state of charge and power supply gaps.

3. The two-stage economic dispatch method for islanded microgrids containing multiple types of loads as described in claim 2, characterized in that: The first stage includes taking real-time tracking of user load and minimizing the total operating cost of each device in the microgrid as the comprehensive objectives. By adopting predictive control, the total operating cost of each device in the microgrid system is dynamically optimized, the power generation of traditional energy sources and the charging and discharging of batteries are selected, and the power supply gap of the microgrid is explicitly calculated.

4. The two-stage economic dispatch method for islanded microgrids containing multiple types of loads as described in claim 3, characterized in that: In the construction of the islanded microgrid model containing multiple types of loads, a dynamic model is established based on augmented states such as state of charge and power supply gap. The total power generation of the microgrid is considered to include renewable energy generation, traditional energy generation, and battery charging and discharging. Let E(t) be the total power generation of the microgrid at time t, satisfying the following equation: E(t)=E mt (t)+E b (t)+E renew (t) The power supply gap Egap(t) of the microgrid at time t is defined as the difference between the user load and the total power generation of the microgrid, i.e.: E gap (t)=E ref (t)-E(t) Subsequently, an incremental dynamic model of the power supply gap Egap(t) is established: At time t+1, according to the expressions for the power supply gap Egap(t) and the total power generation E(t), we know that E gap (t+1)=E ref (t+1)-E(t+1) E(t+1)=E mt (t+1)+E b (t+1)+E renew (t+1) Therefore E gap (t+1)-E gap (t)=[E ref (t+1)-E ref (t)]-[E(t+1)-E(t)] E(t+1)-E(t)=E mt (t+1)-E mt (t)+E b (t+1)-E b (t)+E renew (t+1)-E renew (t) The incremental generation of traditional energy, the incremental charging and discharging of batteries, the incremental generation of renewable energy, and the incremental user load are defined as follows: ΔE mt (t)=E mt (t+1)-E mt (t) ΔE b (t)=E b (t+1)-E b (t) ΔE renew (t)=E renew (t+1)-E renew (t) ΔE ref (t)=E ref (t+1)-E ref (t) Integrating the above six equations, we can obtain the dynamic model for the incremental power supply gap in microgrids: E gap (t+1)=E gap (t)+ΔE ref (t)-(ΔE mt (t)+ΔE b (t)+ΔE renew (t))。 5. The two-stage economic dispatch method for islanded microgrids containing multiple types of loads as described in claim 4, characterized in that: In the first stage, an augmented power supply gap state model is designed, and the economic cost of the gap is introduced as a penalty term into the original performance index of the microgrid to construct a new performance index. Based on this, an economic dispatch optimization strategy is designed, and the optimal dispatch scheme is solved. First, the original economic objective function of the microgrid, i.e., equation (*), is transformed into a two-stage objective function, which consists of the performance index of the generation unit dispatch: And the performance indicators of load scheduling: The performance indicators for microgrid generation unit scheduling can be further transformed as follows: Where R1 is the power supply gap cost penalty coefficient of the microgrid; To eliminate the absolute value term in the above equation, this paper introduces auxiliary variables Egap1(t) and Egap2(t), and uses auxiliary constraints... E gap (t)+E gap1 (t)-E gap2 (t)=0,t=1,2,…,T E gap1 (t)≥0,E gap2 (t)≥0 This expression can be transformed into the following linear form: In summary, the objective function of the microgrid generation unit optimization scheduling problem can be described as follows: Since the operation of a microgrid requires meeting the operational constraints of each unit, including the dynamic equations of energy storage, the optimal scheduling problem of this power generation unit is a dynamic optimization problem.

6. The two-stage economic dispatch method for islanded microgrids containing multiple types of loads as described in claim 5, characterized in that: In the second stage, the load dispatching process considers the supply and demand balance between microgrid generation units and user loads, as expressed in the equation: E(t)-E spill (t)=E impt (t)+U int (t)E int (t)+E shft (t)+E shftnum (t) The left-hand side of the formula represents the actual power generation of the microgrid when it performs wind and solar curtailment operations, while the right-hand side represents the actual power consumption of the microgrid when it performs load interruption and load transfer operations. If there is no wind or solar power curtailment, then Espill(t) = 0, and the result obtained in step S1 can be used as the reference. E gap (t)=E ref (t)-E(t) Substituting into the supply and demand balance equation, we get: When a microgrid contains transferable loads, the microgrid can flexibly adjust the power consumption plans of these loads. However, transferable loads may cause inconvenience to users due to their early or delayed power consumption. Therefore, the microgrid needs to provide appropriate compensation to users. The power transfer cost Cshft(t) for time period t has been given in the optimization problem description of the islanded microgrid model with multiple types of loads, and is shown below for convenience: C shft (t)=R4|E shftnum (t)| To eliminate the absolute value term in the above equation, auxiliary variables Eshftnum1(t) and Eshftnum2(t) are introduced, and auxiliary constraints are applied. E shftnum (t)+E shftnum1 (t)-E shftnum2 (t)=0 E shftnum1 (t)≥0,E shftnum2 (t)≥0 It can be transformed into the following linear form: C shft (t)=R4(E shftnum1 (t)+E shftnum2 (t)) In summary, the microgrid load dispatching problem can be transformed into: The load scheduling optimization problem in the above equation does not contain the dynamic equation expression for energy storage, and belongs to the static optimization problem. Solving this static optimization problem can yield various load allocation schemes and the amount of wind and solar curtailment of renewable energy.

7. The two-stage economic dispatch method for islanded microgrids containing multiple types of loads as described in claim 6, characterized in that: Through the first phase of optimized scheduling of power generation units, the output E of traditional energy sources was selected. mt (t), battery charge / discharge state U b (t), Battery charging and discharging power E b (t), power supply gap value E gap The optimal values ​​of variables such as (t) are respectively labeled as Subsequently, guided by the optimized solution, the output of traditional energy sources, the charging and discharging status of the battery, and the charging and discharging power were implemented; and based on the gap... Classification operation based on whether the value is 0: like Then there is no need to perform the second stage of optimization. Directly assign the following values: power transfer amount of transferable load Eshftnum(t) = 0, operating status of interruptible load Uint(t) = 1, and wind and solar curtailment amount Espill(t) = 0. if Further load scheduling is needed to address the load gap. The allocation is made among the transferable load electricity transfer amount Eshftnum(t), the interruptible load operating status Uint(t), and the wind and solar curtailment amount Espill(t).

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