KR102319625B1 - Microgrid operation method and device to provide operational flexibility in main grid operation - Google Patents

Abstract

The present invention relates to a microgrid operating method and apparatus capable of providing flexibility to large-scale power system operation, and the operating method according to an embodiment of the present invention includes characteristic information of facilities in the microgrid and the microgrid and large-scale power system. Based on the objective function for collecting transaction information between It may include determining the operating cost of the microgrid.

Description

MICROGRID OPERATION METHOD AND DEVICE TO PROVIDE OPERATIONAL FLEXIBILITY IN MAIN GRID OPERATION

The present invention relates to a method and apparatus for operating a microgrid that can provide flexibility to the operation of a large-scale power system, and more particularly, a small-scale distributed resource and an energy storage device, which are flexible resources in a microgrid, can be effectively used in a large-scale power system. It's about technology that makes it possible.

In line with the recent renewable energy promotion policy, the capacity of new and renewable energy sources in the power system is increasing significantly. The increase in renewable energy has various advantages, such as a decrease in electricity prices, reduction of environmental pollutants by reducing the amount of thermal power generation, and creation of new business models. However, renewable energy, which is intermittent, characterized by large volatility and uncertainty, has a great influence on the power system in various time zones and areas such as power quality, voltage management, frequency stability, transmission congestion, reserve power, and power configuration. It causes short-term supply shortage, which causes supply-demand imbalance or significantly increases the volatility of real-time energy prices in the electricity market. In particular, as the grid-connected capacity of renewable energy increases, the frequency of occurrence of “scarcity price” is increasing due to the increase in output volatility in units of minutes and hours, resulting in imbalance between supply and demand.

As such, for the large-scale acceptance of renewable energy sources, it is becoming important to secure an appropriate level of system flexibility, and the required amount is also increasing. Existing studies to respond to the uncertainty and volatility of renewable energy sources focus on securing additional system reserve capacity or utilizing various resources that can provide reserve capacity. However, the method using the reserve resource is economically inefficient and has limitations in that it may cause a problem of lack of energy resources in the system. For this reason, the existing power system calculated the ramping requirement of the generator with the goal of securing flexible resources, and established a power generation plan considering this as a constraint. This ramp-up capacity was named a ramping product and a market was introduced to secure it.

With the introduction of the incremental capacity market and the spread of microgrids to the power system, how to optimize and operate the enlarged power system is emerging as a major concern. A large-scale power system including a conventional microgrid is operated in consideration of only the energy price of power exchanged with the microgrid as a single entity by a power system operator. However, this operation method does not take into account the characteristics of each microgrid's facility characteristics and the variables according to energy use, so it cannot secure the flexibility of new and renewable energy sources, and it causes significant losses in terms of cost in the incremental capacity market. can only do it For example, in the case of a microgrid, small-scale distributed resources and energy storage devices, which are controllable facilities to prevent load shedding in the event of an accident, are widely distributed. There is a problem in that it cannot be used to operate a large-scale power system.

Republic of Korea Patent Publication No. 10-2019-0050318 (2019.05.13)

The present invention is to solve the above-described problems, and by allowing each microgrid to reflect various constraints and participate independently in the increase/decrease capacity market opened in a large-scale power system, the flexibility of the power system is secured and An object of the present invention is to provide a method and apparatus for enabling efficient operation of the entire system.

A microgrid operation method capable of providing flexibility to large-scale power system operation according to an embodiment of the present invention includes the steps of collecting characteristic information of facilities in the microgrid and transaction information between the microgrid and the large-scale power system, within the microgrid Determining ramping capability based on collected information in consideration of facility constraints and determining the operating cost of microgrid based on the objective function for participation in the microgrid's ramping capacity market may include the step of

A microgrid operating apparatus capable of providing flexibility to large-scale power system operation according to an embodiment of the present invention includes a memory for storing at least one instruction and at least one processor executing at least one instruction stored in the memory. Including, by executing one or more instructions, the processor collects characteristic information of equipment in the microgrid and transaction information between the microgrid and the large-scale power system, and based on the collected information in consideration of the constraints on the equipment in the microgrid It is possible to determine the incremental capacity, and the operating cost of the microgrid can be determined based on the objective function for the participation in the microgrid's incremental capacity market.

The constraint according to an embodiment of the present invention may include a constraint regarding the maximum capacity of a line associated with a large-scale power system expressed by the following equations.

,

,

In this case, P _t ^buy is the amount of electricity the microgrid purchases from the large-scale power system at time t, P _t ^sell is the amount of electricity sold by the microgrid to the large-scale power system at time t, and mur _gt is the small-scale distributed resource of the microgrid at time t. where g is the capacity in the increasing direction that can be contributed to the large-scale power system, mur _et is the capacity in the increasing direction that the energy storage device e of the microgrid can contribute to the large-scale power system at time t, mdr _gt is the small-scale distributed resource g at time t is the capacity in the decreasing direction that can contribute to the large-scale power system, mdr _et is the capacity in the decreasing direction that the energy storage device e can contribute to the large-scale power system at time t, and F is the capacity that can be transmitted and received through the connected line.

In addition, the constraint according to an embodiment of the present invention may include a constraint regarding the output of a small-scale distributed resource of the microgrid expressed by the following equations.

,

,

Here, P _g ^min is the minimum output of the small distribution resource g, P _g ^max is the maximum output of the small distribution resource g, p _gt is the output of the small distribution resource g at time t, ur _gt is the small distribution resource g at time t The capacity in the increasing direction that can be contributed to the distribution system and dr _gt are the capacity in the decreasing direction that the small distributed resource g can contribute to the distribution system.

Meanwhile, the objective function according to an embodiment of the present invention may include the following equation.

In this case, C _g ^NL is the no-load cost of the small distributed resource g of the microgrid, C _g ^LP is the generation cost of the small distributed resource g, λ _t ^buy is the electricity price that the microgrid purchases from the large-scale power system at time t, λ _t ^sell is the electricity price that the ^{microgrid sells} to the large-scale power system at time t , λ _t ^{upramp is the resource price in the increasing direction provided from the large-scale power system to the microgrid} at time t, and λ _t dnramp is the electricity price in the large-scale power system at time t It is the resource price in the direction of reduction provided by the microgrid.

According to the microgrid operating method and system provided as an embodiment of the present invention, it is possible to secure and utilize the flexibility of small-scale distributed resources and energy storage devices in the microgrid in large-scale power system operation compared to the conventional microgrid operation method, The operating cost of the microgrid can be greatly reduced, and the welfare of the society as a whole can be increased by establishing an efficient power system control system.

1 is a flowchart of a microgrid operating method according to an embodiment of the present invention.
2 and 3 are graphs showing comparative verification results of a conventional microgrid operating method and a microgrid operating method according to an embodiment of the present invention.
4 is a block diagram of a microgrid operating device according to an embodiment of the present invention.

Terms used in this specification will be briefly described, and the present invention will be described in detail.

The terms used in the present invention have been selected as currently widely used general terms as possible while considering the functions in the present invention, but these may vary depending on the intention or precedent of a person skilled in the art, the emergence of new technology, and the like. In addition, in a specific case, there is a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the corresponding invention. Therefore, the term used in the present invention should be defined based on the meaning of the term and the overall content of the present invention, rather than the name of a simple term.

When a part "includes" a certain element throughout the specification, this means that other elements may be further included, rather than excluding other elements, unless otherwise stated. In addition, the term "processor" described in the specification means a unit for processing at least one function or operation, which may be implemented as hardware or a combination of hardware and software.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart of a microgrid operating method according to an embodiment of the present invention.

The microgrid operating method according to an embodiment of the present invention relates to an optimal scheduling method of the microgrid itself capable of providing flexible ramping capability (FRC) to the main grid of a large-scale power system. In other words, in the proposed microgrid operation method, unlike the conventional one, the microgrid does not depend only on the main grid of a large-scale power system to supply energy to the main system. make it possible

For example, referring to FIG. 1 , the microgrid operating method may include an information collection step ( S10 ), an increase/decrease capacity determination step ( S20 ), and an operation cost determination step ( S30 ). In the information collection step (S10), energy price information is collected as characteristic information of facilities linked to the microgrid and transaction information between the microgrid and the large-scale power system. At this time, the characteristic information of the facilities related to the microgrid includes the amount of renewable energy generation per hour, the load, the physical constraints of the facilities in the microgrid, such as a small-scale distributed resource or energy storage device.

In the step of determining the increase/decrease capacity ( S20 ), a process of estimating the increase/decrease capacity of the microgrid based on the information collected in real time is performed. At this time, assuming that the small-scale distributed resource g and the energy storage device e are included in the microgrid, the constraint expressed by the following equations can be considered to determine the increase/decrease capacity. That is, in the step of determining the increase/decrease capacity (S20), the microgrid reflects the physical constraints due to the characteristics of its own facilities and determines the increase/decrease capacity for the active participation in the increase/decrease capacity market, thereby to ensure flexibility.

[Equation 1]

[Equation 2]

[Equation 3]

[Equation 4]

[Equation 5]

[Equation 6]

[Equation 7]

[Equation 8]

[Equation 9]

[Equation 10]

[Equation 11]

[Equation 12]

[Equation 1] shows the power balance equation, and [Equation 2] and [Equation 3] show the upward and downward flexible capacity for the microgrid. [Equation 4] and [Equation 5] represent the operational limit (ie facility output) for the small-scale distributed resource g, which is an energy generating unit, and [Equation 6] is the energy storage state (State-of-energy) of the energy storage device e. indicates [Equation 7] shows all the constraint conditions (e.g. output limit of the energy storage device e, etc.) of the small-scale distributed resource g, which is an energy generating unit, and the energy storage device e.

Binary variables such as r _t ^buy or r _t ^sell expressed in [Equation 8] and [Equation 9] have a value of 1 when the microgrid operator decides to purchase (sell) energy from the grid. The parameter marked M represents a large positive number in the constraint. [Equation 10] represents a constraint that prevents the microgrid from purchasing or selling energy in the same time period.

[Equation 11] and [Equation 12] are the limiting conditions representing the maximum capacity of the line connected to the large-scale power system, and are conditions that limit the amount of power flow between the microgrid and the large-scale power system. Here, it is assumed that the maximum allowable power flow represented by F is predefined. However, the determination of the F value may be included in the optimization process considering constraints.

Among the above-mentioned constraints, the constraint on small-scale distributed resources expressed in [Equation 4] and [Equation 5] and the capacity constraint of the linkage line expressed in [Equation 11] and [Equation 12] participate in the increasing/decreasing capacity market. This corresponds to a new constraint that microgrid operators must consider. That is, unlike the prior art, in the step of determining the increase/decrease capacity according to an embodiment of the present invention, the capacity constraint of the linked line and the constraint on small-scale distributed resources are considered together, so that the self-regulating capacity of the microgrid can be estimated. have.

In the operation cost determination step (S30), a process of estimating the operating cost of the microgrid itself to participate in the increase/decrease capacity market opened in a large-scale power system based on the increase/decrease capacity estimated through the above-described process (S20) is performed. do. At this time, assuming that the small-scale distributed resource g and the energy storage device e are included in the microgrid, the objective function expressed by the following [Equation 13] can be used to determine the operating cost. That is, in the operation cost determination step (S30), the microgrid calculates the operation cost using an objective function based on the increase/decrease capacity determined by reflecting the physical constraints due to the characteristics of its own facilities, thereby reducing the overall cost of the large-scale power system. to ensure flexibility.

[Equation 13]

The objective function is a function for minimizing the operating cost, and allows to calculate the difference by subtracting the sales revenue of the variable-capacity product from the total energy cost. Here, the total energy cost means the sum of the generation cost of the microgrid and the net cost associated with the energy transaction with the main grid. The load of the microgrid can be supplied by the power generation resource of the microgrid or by the main grid.

2 is a graph showing a change in power output of a thermal power plant (CHP #2) selected for simulation of the present invention, and FIG. 3 is a graph showing a change in an energy storage state of an energy storage device.

Simulations of the present invention were performed on a microgrid equipped with a photovoltaic installation (PV), a gas turbine generator (GT), two types of combined cycle power plants (CHP #1, CHP #2) and electrical energy storage. The scheduling period was set to 24 hours per day based on the time interval. The optimization problem was solved using GAMS/GUROBI software with winter weekday data and the optimal difference was set to 0.1%. In the conventional approach, the price of the incremental capacity product is set to zero, leaving the microgrid indifferent to providing flexible incremental capacity to the main grid. The transmission power limit between the microgrid and the main grid is assumed to be 200 kW, which is 17.6% of the peak load.

[Table 1] shows the cost-effectiveness of the proposed method under the price conditions of various incremental capacity products (i.e. flexible resources). As shown in [Table 1], microgrids can provide flexible resources to the main grid, reducing operating costs. It can be seen that the savings increase rapidly as the price of the flexible resource increases, which is because the scheduling of the microgrid is optimized in such a way that not only the price of the flexible resource changes, but also the price of the flexible resource increases, extending the benefits. Because. The advantage of supplying flexible resources to the main grid can be clearly seen in [Table 2], which summarizes the components of operating costs together with FIGS. 2 and 3 . It can be seen that in the proposed method, the microgrid can provide a flexible resource and generate a revenue of about $147. In addition, it can be seen that the total energy cost increases by about $31 through the optimization of the scheduling of the microgrid in the proposed method. However, it can be seen that the profit from the sale of the incremental capacity product is much greater than the increase in the total energy cost.

[Table 1]

[Table 2]

Table 3 summarizes the total amount of energy generated by each energy generating unit during the entire scheduling period. If it is possible for the microgrid to provide flexible resources to the main grid, it can be seen that less energy is generated in the microgrid and therefore less energy is sold to the main grid. The reason for the decrease in energy production is the flow limitation of the line connecting the microgrid and the main grid. According to the proposed method, a part of the line transmission capacity is reserved for the provision of flexible resources, which can reduce the amount of transactional energy available through the line.

[Table 3]

As can be seen from the simulation results described above. The microgrid operation model proposed in the present invention can enable the microgrid to perform operation scheduling according to the price of the product of increasing/decreasing capacity in consideration of various constraints of the microgrid by itself. Therefore, the microgrid operation model proposed in the present invention can reduce the operating cost of the microgrid, and has the advantage of securing operational flexibility in a large-scale power system.

4 is a block diagram of a microgrid operating device according to an embodiment of the present invention.

Referring to FIG. 4 , the microgrid operating apparatus 100 that can provide flexibility in operating a large-scale power system according to an embodiment of the present invention includes a memory 110 and a memory 110 for storing at least one instruction. ), including at least one processor 120 executing at least one instruction stored in, and the processor 120 executing one or more instructions, thereby providing characteristic information of facilities in the microgrid and transaction information between the microgrid and the large-scale power system. The operating cost of the microgrid based on the objective function for participation in the microgrid's incremental capacity market can be decided

With respect to the apparatus according to an embodiment of the present invention, the above-described method may be applied. Accordingly, with respect to the apparatus, descriptions of the same contents as those of the above-described method are omitted.

Meanwhile, according to an embodiment of the present invention, it is possible to provide a computer-readable recording medium in which a program for executing the above-described method is recorded in a computer. In other words, the above-described method can be written as a program that can be executed on a computer, and can be implemented in a general-purpose digital computer that operates the program using a computer-readable medium. In addition, the structure of the data used in the above-described method may be recorded in a computer-readable medium through various means. A recording medium for recording an executable computer program or code for performing various methods of the present invention should not be construed as including temporary objects such as carrier waves or signals. The computer-readable medium may include a storage medium such as a magnetic storage medium, an optically readable medium, and the like.

The above description of the present invention is for illustration, and those of ordinary skill in the art to which the present invention pertains can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a dispersed form, and likewise components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. .

100: microgrid operating device
110: memory
120: processor

Claims (8)

In a microgrid operation method that can provide flexibility to large-scale power system operation,
Collecting characteristic information of facilities in the microgrid and transaction information between the microgrid and the large-scale power system;
determining a ramping capability based on the collected information in consideration of constraints on facilities in the microgrid; and
Determining the operating cost of the microgrid based on an objective function for participation in the increase/decrease capacity market of the microgrid,
The constraint includes a constraint on the maximum capacity of the line associated with the large-scale power system expressed by the following equations,

,

,
The P _t ^buy is the amount of electricity the microgrid purchases from the large-scale power system at time t, P _t ^sell is the amount of electricity the microgrid sells to the large-scale power system at time t, mur _gt is the microgrid at time t The capacity in the increasing direction that the small distributed resource g of can contribute to the large-scale power system, mur _et is the capacity in the increasing direction that the energy storage device e of the microgrid can contribute to the large-scale power system at time t, mdr _gt is At time t, the capacity in the decreasing direction that the small-scale distributed resource g can contribute to the large-scale power system, mdr _et is the capacity in the decreasing direction at which the energy storage device e can contribute to the large-scale power system at time t, and F is the A method, characterized in that it is a capacity that can be sent and received through a connected line.
delete The method of claim 1,
The constraint includes a constraint on the output of the small-scale distributed resource of the microgrid expressed by the following equations,

,

,
wherein P _g ^min is the minimum output of the small distribution resource g, P _g ^max is the maximum output of the small distribution resource g, p _gt is the output of the small distribution resource g at time t , ur _{gt is the small distribution resource g at time t} A method, characterized in that g is the capacity in the increasing direction that can contribute to the distribution system and dr _gt is the capacity in the decreasing direction that the small-scale distributed resource g can contribute to the distribution system.
The method of claim 1,
The objective function includes the following formula,

,
The C _g ^NL is the no-load cost of the small distributed resource g of the microgrid, C _g ^LP is the power generation cost of the small distributed resource g, λ _t ^buy is the electricity price the microgrid purchases from the large-scale power system at time t , λ _t ^sell is the power price sold by the ^microgrid to the large-scale power system at time t, λ _t upramp is the resource price in the increasing direction provided from the large-scale power system to the microgrid at time t, and λ _t ^dnramp is A method, characterized in that it is a resource price in a decreasing direction provided from the large-scale power system to the microgrid at time t.
In the microgrid operating device that can provide flexibility for large-scale power system operation,
a memory for storing at least one instruction; and
at least one processor executing the at least one instruction stored in the memory;
The processor by executing the one or more instructions,
Collecting characteristic information of facilities in the microgrid and transaction information between the microgrid and the large-scale power system,
Determine the ramping capability based on the collected information in consideration of the constraints on the facilities in the microgrid,
Determining the operating cost of the microgrid based on the objective function for participation in the increase/decrease capacity market of the microgrid,
The constraint includes a constraint on the maximum capacity of the line associated with the large-scale power system expressed by the following equations,

,

,
The P _t ^buy is the amount of electricity the microgrid purchases from the large-scale power system at time t, P _t ^sell is the amount of electricity the microgrid sells to the large-scale power system at time t, mur _gt is the microgrid at time t The capacity in the increasing direction that the small distributed resource g of can contribute to the large-scale power system, mur _et is the capacity in the increasing direction that the energy storage device e of the microgrid can contribute to the large-scale power system at time t, mdr _gt is At time t, the capacity in the decreasing direction that the small-scale distributed resource g can contribute to the large-scale power system, mdr _et is the capacity in the decreasing direction at which the energy storage device e can contribute to the large-scale power system at time t, and F is the A device, characterized in that it has a capacity that can be exchanged through a connected line.
delete 6. The method of claim 5,
The constraint includes a constraint on the output of the small-scale distributed resource of the microgrid expressed by the following equations,

,

,
wherein P _g ^min is the minimum output of the small distribution resource g, P _g ^max is the maximum output of the small distribution resource g, p _gt is the output of the small distribution resource g at time t , ur _{gt is the small distribution resource g at time t} Device, characterized in that g is the capacity in the increasing direction that can contribute to the distribution system and dr _gt is the capacity in the decreasing direction that the small-scale distributed resource g can contribute to the distribution system.
6. The method of claim 5,
The objective function includes the following formula,

,
The C _g ^NL is the no-load cost of the small distributed resource g of the microgrid, C _g ^LP is the power generation cost of the small distributed resource g, λ _t ^buy is the electricity price the microgrid purchases from the large-scale power system at time t , λ _t ^sell is the power price sold by the ^microgrid to the large-scale power system at time t, λ _t upramp is the resource price in the increasing direction provided from the large-scale power system to the microgrid at time t, and λ _t ^dnramp is Apparatus, characterized in that the resource price in the decreasing direction provided from the large-scale power system to the microgrid at time t.

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