Energy management method for wind-solar-diesel-storage island micro-grid system

Abstract

The invention provides an energy management method for a wind-solar-diesel-storage island micro-grid system. The energy management method comprises the following steps: S1, acquiring meteorological information of an environment where the micro-grid system is located in a set time in the future and micro-grid system information at a previous moment; s2, establishing a wind power generation unit power model and a photovoltaic power generation unit power model, and determining the wind power generation power and the photovoltaic power generation power in the future set time based on the meteorological information; s3, constructing an energy management objective function, and solving a minimum value of the objective function; and S4, constructing an energy balance equation of the micro-grid system, determining the charging and discharging power of the energy storage battery and the output power of the diesel power generation unit in the future set time based on the energy balance equation and the charge state and the fuel quantity corresponding to the minimum value of the target function, and controlling the energy storage battery and the diesel power generation unit to work according to the determined power.

Description

Technical Field

[0001] The present invention relates to an energy management method, and in particular to an energy management method for a wind-solar-diesel-storage isolated island microgrid system. Background Art

[0002] In more remote areas, due to the distance from conventional large-scale power grids, it is difficult to achieve a good electricity supply.

[0003] In the existing technology, diesel generators are often used as the source of electricity, but diesel engine power generation has disadvantages such as high cost and high pollution. Therefore, considering that these areas are rich in clean and renewable resources such as wind energy and solar energy, making full use of wind energy and solar energy to establish an island microgrid can achieve self-sufficiency in electricity. However, wind energy and solar energy depend on natural conditions and cannot provide stable power output. They have strong randomness and volatility. In addition, the energy management strategy of the existing wind, solar, diesel and storage island microgrid system mainly adopts a rule-based control method, and the formulation of rules depends on subjective experience, and the improvement of economy and energy efficiency is limited. The wind, solar, diesel and storage coordinated control method using the instantaneous optimization method cannot achieve global optimization of economy and energy efficiency.

[0004] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide an energy management method for an isolated island microgrid system of wind, solar, diesel and energy storage, which takes the environmental parameters of the isolated island microgrid, the power of the wind power generation unit and the photovoltaic power generation unit as the state quantity, and dynamically predicts the power of the diesel power generation unit and the energy storage battery at a future time point, and then based on the power, the charging and discharging of the energy storage battery and the operation of the diesel power generation unit are controlled, which can effectively and reasonably control the energy of the isolated island microgrid, reduce the operation and maintenance cost of the diesel power generation unit, and make the SOC change of the energy storage battery always maintain near the initial value, which plays an environmental protection role while extending the service life of the energy storage battery.

[0006] The present invention provides an energy management method for a wind-solar-diesel-storage isolated island microgrid system, comprising the following steps:

[0007] S1. Obtain the meteorological information of the environment where the microgrid system is located within the future set time and the microgrid system information at the previous moment;

[0008] S2. Establish a wind power generation unit power model and a photovoltaic power generation unit power model, and determine the wind power generation power and photovoltaic power generation power within a set time in the future based on meteorological information;

[0009] S3. Construct an energy management objective function and solve the minimum value of the objective function; wherein the objective function is:

[0010] L=αm fuel (t)+β(SOC(t)-SOC ref ) 2 +γF(P(t));

[0011] α, β, γ are the weighting coefficients of the corresponding parameters, m fuel (t) is the fuel consumption of the diesel generator unit, SOC(t) is the state of charge of the energy storage battery of the microgrid system at time t, SOC ref is the reference state of charge of the energy storage battery; F(P(t))=ξP c (t), ξ is the operation and maintenance cost coefficient, P c (t) is the output power of the diesel generator unit;

[0012] S4. Construct the energy balance equation of the microgrid system, determine the charging and discharging power of the energy storage battery and the output power of the diesel generator unit within the future set time based on the energy balance equation and the corresponding charge state and fuel quantity when the objective function is minimized, and control the energy storage battery and diesel generator unit to work according to the determined power.

[0013] Furthermore, the meteorological information of the environment in which the microgrid system is located includes wind speed, light intensity and ambient temperature;

[0014] The microgrid system information includes wind power generation power, solar power generation power, SOC of the energy storage battery and load demand power.

[0015] Furthermore, the wind power generation unit power model is:

[0016]

[0017] Where: v(t) represents the wind speed at time t, P r represents the rated power of the wind power generation unit of the microgrid system, v r represents the rated wind speed, a and b are constant coefficients, v min and v max are the lower and upper limits of the wind speed range, and the wind turbine can only output electrical energy within this wind speed range.

[0018] Furthermore, the photovoltaic power generation unit power model is:

[0019]

[0020] Where: f p is the derating factor of the photovoltaic array of the photovoltaic power generation unit, P stc is the rated power of the photovoltaic array under standard test conditions, G stcis the light intensity of the photovoltaic array under standard test conditions, G(t) is the light intensity at time t, k is the power temperature coefficient, and T(t) is the surface temperature of the photovoltaic panel.

[0021] Furthermore, the surface temperature T(t) of the photovoltaic panel is determined by the following method:

[0022] T(t)=T a (t)+0.0138[1+0.031T a (t)](1-0.042v(t))G(t)

[0023] Where: T a (t) is the ambient temperature at time t.

[0024] Further, step S4 specifically includes:

[0025] Establish the energy balance equation of the microgrid system:

[0026] P w (t)+P p (t)+P bat (t)+P c (t) = P l (t);

[0027] P w (t) is the output power of the wind power generation unit at time t, P p (t) is the output power of the photovoltaic power generation unit, P bat (t) is the charging and discharging power of the energy storage battery, P c (t) is the output power of the diesel generator unit, P1(t) is the load demand power;

[0028] Discretize the future set time period T into n time points, and time t corresponds to time point k;

[0029] Determine the battery state of charge at time k+1:

[0030]

[0031] I bat (t) is the current of the energy storage battery, V oc is the open circuit voltage of the energy storage battery, R bat is the internal resistance of the energy storage battery, Q bat is the capacity of the energy storage battery, η is the efficiency of the energy storage battery;

[0032] Under the condition of the energy balance equation of the microgrid system, the objective function is solved to obtain the energy storage battery charging and discharging power and the output power of the diesel generator unit when the objective function reaches the minimum value at time k+1, and then the difference between the energy storage battery charging and discharging power at time k+1 and time k is made, and the output power of the diesel generator unit is made, and then the energy storage battery and the diesel generator unit are controlled by the difference in the energy storage battery charging and discharging power and the output power of the diesel generator unit.

[0033] Beneficial effects of the present invention: Through the present invention, the environmental parameters of the isolated microgrid, the power of the wind power generation unit and the photovoltaic power generation unit are used as state quantities to dynamically predict the power of the diesel power generation unit and the energy storage battery at a future time point, and then the charging and discharging of the energy storage battery and the operation of the diesel power generation unit are controlled based on the power, so that the energy of the isolated microgrid can be effectively and reasonably controlled, and the operation and maintenance cost of the diesel power generation unit can be reduced, and the SOC change of the energy storage battery can be always maintained near the initial value, which plays an environmental protection role while extending the service life of the energy storage battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0035] Figure 1 It is a flow chart of the present invention.

[0036] Figure 2 It is a schematic diagram of the structure of the isolated island microgrid system of the present invention.

[0037] Figure 3 The graph is a curve showing the relationship between the wind turbine output power and wind speed of the wind power generation system of the present invention.

[0038] Figure 4 This is a schematic diagram of the global optimal control algorithm of the present invention. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below:

[0040] The present invention provides an energy management method for a wind-solar-diesel-storage isolated island microgrid system, comprising the following steps:

[0041] S1. Obtain the meteorological information of the environment where the microgrid system is located within the future set time and the microgrid system information at the previous moment;

[0042] S2. Establish a wind power generation unit power model and a photovoltaic power generation unit power model, and determine the wind power generation power and photovoltaic power generation power within a set time in the future based on meteorological information;

[0043] S3. Construct an energy management objective function and solve the minimum value of the objective function; wherein the objective function is:

[0044] L=αm fuel (t)+β(SOC(t)-SOC ref ) 2 +γF(P(t));

[0045] α, β, γ are the weighting coefficients of the corresponding parameters, m fuel (t) is the fuel consumption of the diesel generator unit, SOC(t) is the state of charge of the energy storage battery of the microgrid system at time t, SOC ref is the reference state of charge of the energy storage battery; F(P(t))=ξP c (t), ξ is the operation and maintenance cost coefficient, P c (t) is the output power of the diesel generator unit;

[0046] S4. Construct the energy balance equation of the microgrid system, determine the charging and discharging power of the energy storage battery and the output power of the diesel generator unit within the future set time based on the energy balance equation and the corresponding charge state and fuel quantity when the objective function is minimized, and control the energy storage battery and diesel generator unit to work according to the determined power.

[0047] like Figure 2 As shown, the wind-solar-diesel-storage isolated island microgrid involved in the present invention is composed of a wind power generation unit, a photovoltaic power generation unit, a diesel power generation unit and an energy storage battery;

[0048] The wind power generation unit includes a wind turbine, an AC-DC converter, and a motor controller. The motor controller calculates the optimal wind turbine speed based on the optimal blade tip speed ratio and the real-time wind speed to achieve maximum power generation tracking of the wind turbine.

[0049] The photovoltaic power generation unit includes a photovoltaic panel, a DC-DC converter, and a photovoltaic controller. The photovoltaic controller always keeps tracking of the maximum photovoltaic power generation according to external factors such as temperature and light intensity.

[0050] The diesel power generation unit includes a diesel generator, a fuel tank, a starter motor, an AC-DC converter, and a diesel generator controller, and its output end is connected to the DC bus to replenish energy for the energy storage battery pack and compensate for the power of the wind and solar power generation system.

[0051] The energy storage battery is connected to the DC-DC converter and then to the DC bus to supply power to the debt equipment and store the electric energy generated by the wind and solar power generation system and the diesel generator system.

[0052] Through the present invention, the environmental parameters of the isolated island microgrid, the power of the wind power generation unit and the photovoltaic power generation unit are used as state quantities to dynamically predict the power of the diesel power generation unit and the energy storage battery at a future time point. Then, based on the power, the energy storage battery is charged and discharged and the diesel power generation unit is operated. This can effectively make the energy of the isolated island microgrid reasonably controlled, reduce the operation and maintenance cost of the diesel power generation unit, and make the SOC change of the energy storage battery always maintain near the initial value, which plays an environmental protection role while extending the service life of the energy storage battery.

[0053] In this embodiment, the meteorological information of the environment where the microgrid system is located includes wind speed, light intensity and ambient temperature;

[0054] The microgrid system information includes wind power generation power, solar power generation power, SOC of the energy storage battery and load demand power.

[0055] In this embodiment, the wind power generation unit power model is:

[0056]

[0057] Where: v(t) represents the wind speed at time t, P r represents the rated power of the wind power generation unit of the microgrid system, v r represents the rated wind speed, a and b are constant coefficients, v min and v max are the lower and upper limits of the wind speed range, and the wind turbine generator can only output electrical energy within this wind speed range. Among them, the output power curve of the wind power generation unit is as follows Figure 3 As shown;

[0058] The photovoltaic power generation unit power model is:

[0059]

[0060] Where: f p is the derating factor of the photovoltaic array of the photovoltaic power generation unit, P stc is the rated power of the photovoltaic array under standard test conditions, G stc is the light intensity of the photovoltaic array under standard test conditions, G(t) is the light intensity at time t, k is the power temperature coefficient, and T(t) is the surface temperature of the photovoltaic panel.

[0061] Among them, the surface temperature T(t) of the photovoltaic panel is determined by the following method:

[0062] T(t)=T a (t)+0.0138[1+0.031T a (t)](1-0.042v(t))G(t)

[0063] Where: T a (t) is the ambient temperature at time t.

[0064] In this embodiment, step S4 specifically includes:

[0065] Establish the energy balance equation of the microgrid system:

[0066] P w (t)+P p (t)+P bat (t)+P c (t) = P l (t);

[0067] P w (t) is the output power of the wind power generation unit at time t, P p (t) is the output power of the photovoltaic power generation unit, P bat (t) is the charging and discharging power of the energy storage battery, P c (t) is the output power of the diesel generator unit, and P1(t) is the load demand power; the island microgrid system needs to meet the following power constraints:

[0068]

[0069] P w_max , P p_max , P c_max The output power limit of the wind-solar-diesel power generation system; S max is the maximum state of charge of the energy storage battery, P bat_min The upper limit of battery charging power, P bat_max The upper limit of battery discharge power;

[0070] Discretize the future set time period T into n time points, with time t corresponding to time point k; determine the battery charge state at time point k+1:

[0071]

[0072] I bat (t) is the current of the energy storage battery, V oc is the open circuit voltage of the energy storage battery, R bat is the internal resistance of the energy storage battery, Q bat is the capacity of the energy storage battery, η is the efficiency of the energy storage battery;

[0073] Under the condition of the energy balance equation of the microgrid system, the objective function is solved to obtain the energy storage battery charging and discharging power and the output power of the diesel generator unit when the objective function reaches the minimum value at time k+1, and then the energy storage battery charging and discharging power at time k+1 and time k are subtracted, and the output power of the diesel generator unit is subtracted, and then the energy storage battery and the diesel generator unit are controlled by the difference in the energy storage battery charging and discharging power and the output power difference of the diesel generator unit. Among them, when solving the objective function, a two-dimensional dynamic programming algorithm is used for solution, including inverse solution and forward recovery, which is an existing technology, such as Figure 4 As shown: reverse solution, starting from time t+n to time t, record the minimum objective function value at each moment through parameter traversal, and record the energy storage battery charging and discharging power and diesel engine generating power at the corresponding moment, and obtain the global optimal battery charging and discharging power and diesel engine generating power in the future T time; forward recovery, restore the optimal control trajectory from the starting step. This specific process is an existing technology and will not be described in detail here. When the entire microgrid system runs to time t+1 or time k+1, repeat the process of step S4.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A wind-solar-diesel-storage island microgrid system energy management method, characterized by: The following steps are involved: S1. Obtain the meteorological information of the environment where the microgrid system is located within the future set time and the microgrid system information at the previous moment; S2. Establish a wind power generation unit power model and a photovoltaic power generation unit power model, and determine the wind power generation power and photovoltaic power generation power within a set time in the future based on meteorological information; S3. Construct an energy management objective function and solve the minimum value of the objective function; wherein the objective function is: L=αm fuel (t)+β(SOC(t)-SOC ref ) 2 +γF(P(t)); α, β, γ are the weighting coefficients of the corresponding parameters, m fuel (t) is the fuel consumption of the diesel generator unit, SOC(t) is the state of charge of the energy storage battery of the microgrid system at time t, SOC ref is the reference state of charge of the energy storage battery; F(P(t))=ξP c (t), ξ is the operation and maintenance cost coefficient, P c (t) is the output power of the diesel generator unit; S4. Construct the energy balance equation of the microgrid system, determine the charging and discharging power of the energy storage battery and the output power of the diesel generator unit within the future set time based on the energy balance equation and the corresponding charge state and fuel quantity when the objective function is minimized, and control the energy storage battery and diesel generator unit to work according to the determined power.

2. The energy management method for wind-solar-diesel-storage isolated island microgrid system according to claim 1 is characterized by: The meteorological information of the environment where the microgrid system is located includes wind speed, light intensity and ambient temperature; The microgrid system information includes wind power generation power, solar power generation power, SOC of the energy storage battery and load demand power.

3. The energy management method of wind-solar-diesel-storage isolated island microgrid system according to claim 1 is characterized by: The wind power generation unit power model is: Where: v(t) represents the wind speed at time t, P r represents the rated power of the wind power generation unit of the microgrid system, v r represents the rated wind speed, a and b are constant coefficients, v min and v max are the lower and upper limits of the wind speed range, and the wind turbine can only output electrical energy within this wind speed range.

4. The energy management method for wind-solar-diesel-storage isolated island microgrid system according to claim 1 is characterized by: The photovoltaic power generation unit power model is: Where: f p is the derating factor of the photovoltaic array of the photovoltaic power generation unit, P stc is the rated power of the photovoltaic array under standard test conditions, G stc is the light intensity of the photovoltaic array under standard test conditions, G(t) is the light intensity at time t, k is the power temperature coefficient, and T(t) is the surface temperature of the photovoltaic panel.

5. The energy management method for wind-solar-diesel-storage isolated island microgrid system according to claim 4 is characterized by: The surface temperature T(t) of the photovoltaic panel is determined by the following method: T(t)=T a (t)+0.0138[1+0.031T a (t)](1-0.042v(t))G(t) Where: T a (t) is the ambient temperature at time t.

6. The energy management method for wind-solar-diesel-storage isolated island microgrid system according to claim 1 is characterized by: Step S4 specifically includes: Establish the energy balance equation of the microgrid system: P w (t)+P p (t)+P bat (t)+P c (t)=P l (t); P w (t) is the output power of the wind power generation unit at time t, P p (t) is the output power of the photovoltaic power generation unit, P bat (t) is the charging and discharging power of the energy storage battery, P c (t) is the output power of the diesel generator unit, P1(t) is the load demand power; Discretize the future set time period T into n time points, and time t corresponds to time point k; Determine the battery state of charge at time k+1: I bat (t) is the current of the energy storage battery, V oc is the open circuit voltage of the energy storage battery, R bat is the internal resistance of the energy storage battery, Q bat is the capacity of the energy storage battery, η is the efficiency of the energy storage battery; Under the condition of the energy balance equation of the microgrid system, the objective function is solved to obtain the energy storage battery charging and discharging power and the output power of the diesel generator unit when the objective function reaches the minimum value at time k+1, and then the difference between the energy storage battery charging and discharging power at time k+1 and time k is made, and the difference between the output power of the diesel generator unit is made, and then the energy storage battery and the diesel generator unit are controlled by the difference in the energy storage battery charging and discharging power and the difference in the output power of the diesel generator unit.

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