KR20190042349A - Power capacity calculation system of distributed generator - Google Patents

Abstract

The present invention provides a capacity calculation system of a distributed generator which is applicable to a direct current (DC) distribution system having various types of grid structures. According to an embodiment of the present invention, the capacity calculation system comprises: a maximum capacity calculation unit individually calculating a maximum capacity of a plurality of distributed generators individually connected to a plurality of buses of a DC distribution system; and a maximum capacity restriction unit restricting the maximum capacity of the distributed generator to a capacity of an inverter of the DC distribution system.

Description

{POWER CAPACITY CALCULATION SYSTEM OF DISTRIBUTED GENERATOR}

The present invention relates to a capacity estimation system of a distributed generator.

There has been an increasing demand for direct supply of direct current power with the emergence of direct current such as direct current (DC) Internet data center (IDC). As a result, a direct current distribution capable of directly supplying a direct current power source to a consumer has been developed. In order to increase the usability of DC distribution, it is necessary to connect distributed generators such as solar power, wind power, and battery to the DC distribution system.

Recently, in designing and operating the DC distribution system in the urban area, the capacity of the distributed generator connected to the DC distribution system is estimated from the economic view through the investment cost analysis. However, distributed generators operating as separate generators can affect the voltage that determines the power quality of the DC distribution system. Only from an economic point of view, when estimating the capacity of the distributed generator, an additional device such as a voltage regulator is required to stabilize the voltage of the system of the DC distribution, which rather lowers the economical efficiency of DC distribution Which can lead to problems. Therefore, in estimating the capacity of the distributed generator, it is necessary to calculate the capacity of the distributed generator so that the DC distribution system can be operated not only in economy but also in a constant voltage range.

In addition, currently, in the AC power distribution system, the appropriate capacity of the distributed generator is calculated through the total power consumption of the customer and the minimum / maximum load. However, this is not suitable for utilization in designing and operating the DC distribution system have. Therefore, there is a need for a method for estimating the maximum power generation capacity of a distributed generator capable of being used in a DC power distribution system and capable of operating a DC power distribution system stably in various types of power network structures.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a system for calculating the capacity of a distributed generator which is applicable to DC distribution systems of various types of power network structures.

The capacity calculation system according to an embodiment of the present invention includes a maximum capacity calculation unit for calculating maximum capacities of a plurality of distributed generators connected to a plurality of buses of a DC power distribution system, respectively; And a maximum capacity limiting unit that limits the maximum capacity of the distributed generator to the capacity of the inverter of the DC power distribution system; . ≪ / RTI >

The capacity calculation system according to an embodiment of the present invention can be applied to a DC distribution system having various types of power network structures, but it can prevent an overvoltage condition of a DC distribution system.

1 is a configuration diagram of a DC distribution system according to an embodiment of the present invention.
2 is a diagram showing an equivalent model of the DC distribution system according to the embodiment of FIG. 1
3 is a block diagram illustrating a capacity determination system of a distributed generator according to an embodiment of the present invention.
4 is a flowchart illustrating a method of calculating a capacity of a distributed generator according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the present invention, examples of which are illustrated in the accompanying drawings, wherein specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with an embodiment. It is also to be understood that the position or arrangement of individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is to be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if properly explained. In the drawings, like reference numbers may refer to the same or similar functions throughout the several views.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily carry out the present invention.

FIG. 1 is a configuration diagram of a DC power distribution system according to an embodiment of the present invention, and FIG. 2 is an equivalent model of a DC power distribution system according to the embodiment of FIG. 1

1, the DC power distribution system includes an AC / DC inverter 101 connected to an AC power source 100 and an AC power source 100 to convert the AC power source 100 into a DC power source, And a DC load 110-113 which receives the DC power supplied from the inverter 101 through the DC power distribution line (Line 1 - Line).

1 and 2, the DC power source, the DC power distribution line (Line 1-4), and the DC load 110-113 of the AC / DC inverter 101 of the DC power distribution system of FIG. Can be equivalent to the DC power source Vdc, the line admittances g12, g23, g34 and g45, and the slave current sources (Unit2 to Unit5). In FIG. 2, it is assumed that voltages V1-V5 are formed on the buses Bus1-5 to which the slave current sources Unit2-5 according to the DC power source Vdc and the DC loads 110-113 are connected. A plurality of distributed generators can be individually connected to each of the plurality of buses Bus2-5 to which the DC load 110-113 and the slave current sources Unit2-Unit5 shown in Fig. 1 and Fig. 2 are connected.

3 is a block diagram illustrating a capacity determination system of a distributed generator according to an embodiment of the present invention. Referring to FIG. 3, the capacity calculation system of the distributed generator may include a maximum capacity calculation unit 201 and a maximum capacity limitation unit 202.

The maximum capacity calculating unit 201 may calculate the maximum capacity that can be generated by the distributed generator and the maximum capacity limiting unit 202 may limit the maximum capacity of the distributed generator that is calculated by the maximum capacity calculator 210. [

4 is a flowchart illustrating a method of calculating a capacity of a distributed generator according to an embodiment of the present invention. Hereinafter, the capacity calculation method of the capacity calculation system will be described in detail with reference to FIG. 3 and FIG.

Referring to FIG. 4, a method of calculating the capacity of a distributed generator according to an embodiment of the present invention starts with calculating a voltage sensitivity matrix (4201). The voltage sensitivity matrix can be calculated from the inverse matrix of the Jacobian matrix according to the established power equation by establishing the power equation according to the power network configuration of the DC power distribution system. Assuming that the power network is composed of n + 1 busses, the bus connected to the dc power supply can be omitted, so that the Jacobian matrix and the voltage sensitivity matrix can be represented by a square matrix of n rows and n columns.

Referring to FIG. 2, the power equation for each bus can be expressed as Equation 1 below.

From the equation (1), a Jacobian matrix can be calculated through a partial derivative of the voltage of each bus, and a Jacobian matrix can be expressed by the following equation (2).

Referring to Equation (2), in order to calculate a Jacobian matrix, a voltage value per bus must be substituted. However, the maximum capacity of the distributed generators that can be used can be estimated by assuming the worst situation at the time when the distributed generators are charged. Therefore, for bus-specific voltage values, it is assumed that the load is not connected to the DC distribution system. When the load is not connected to the DC distribution system, since the voltage per bus is the same, the equation (2) can be expressed as the following equation (3).

The line admittance was selected as shown in Table 1 below under the condition of one example of calculating the voltage sensitivity matrix.

When the inverse matrix is calculated after substituting the line admittance into the Jacobian matrix, the voltage sensitivity matrix S can be expressed by Equation (4).

After calculating the voltage sensitivity matrix, the maximum voltage sensitivity of the power network per bus from the voltage sensitivity matrix can be determined (S402). The maximum voltage sensitivity of each bus in a power network composed of a plurality of buses can be calculated from the maximum value of the column of the voltage sensitivity matrix. Since the voltage sensitivity matrix is a square matrix of n rows and n columns, there can be n maximum values in each column.

After the maximum voltage sensitivity for each bus is determined, the maximum capacity at which the distributed generator can develop from the maximum voltage sensitivity per bus can be calculated (S403). For example, the maximum capacity of the distributed generator connected to the j-th bus may be determined by the maximum voltage sensitivity of the j-th bus, the voltage of the i-th bus corresponding to the maximum voltage sensitivity of the j-th bus, and the allowable voltage per bus. Specifically, the maximum capacity of the distributed generator connected to the j-th bus can be calculated according to the following equation (5). Where Vi is the voltage of the ith bus corresponding to the maximum voltage sensitivity of the jth bus, Pj is the capacity of the distributed generator that is applied to the jth bus, The minimum allowable voltage, Vmax, represents the maximum allowable voltage per bus.

In the case of inputting the distributed generator, since the power change increases, the equation concerning the minimum permissible voltage Vmin for each bus is removed, and the equation (5) can be expressed as shown in equation (6).

Assuming that Vi is 1500V and the maximum allowable voltage is 1600V, corresponding to the nominal voltage of the DC distribution system, the maximum voltage sensitivity component according to the column voltage sensitivity matrix S of Equation (4) The maximum capacity of distributed generators for each bus is shown in Table 2 below.

After the maximum capacity of the distributed generator is calculated, the calculated maximum capacity of the distributed generator can be limited to the capacity of the AC / DC inverter of the DC distribution system (S204). If the distributed generators generate more power than the AC / DC inverter can accommodate in situations where the load on the DC distribution system is minimal, equipment failure and overvoltage conditions in the DC distribution system may result. Therefore, the maximum capacity of the distributed generators estimated needs to be limited to the capacity of the AC / DC inverter.

For example, the rated capacity of the AC / DC inverter may be 110 kW. If the maximum capacity of the distributed generator is limited to the AC / DC inverter capacity, the capacity of the distributed generator in Table 2 can be limited as shown in Table 3 below. As shown in Table 3, distributed generators can be installed for the AC / DC inverter capacity for Bus 2 and 3, and distributed generators can be installed for Bus 4 and 5 smaller than the AC / DC inverter capacity.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but many variations and modifications may be made without departing from the scope of the present invention. It will be understood that the invention may be practiced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Therefore, the spirit of the present invention should not be construed as being limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the following claims, I will say.

200: capacity calculation system
201: maximum capacity calculating section
202: Maximum Capacity Limit

Claims (6)

A maximum capacity calculating unit for respectively calculating a maximum capacity of a plurality of distributed generators connected to the plurality of buses of the DC power distribution system; And
A maximum capacity limiter for limiting the maximum capacity of the distributed generator to the capacity of the inverter of the DC power distribution system; The capacity calculation system comprising:
The apparatus according to claim 1,
Wherein the maximum capacity of the distributed generator of the one bus is calculated according to the voltage sensitivity between one bus of the plurality of distributed generators and the remaining bus.
3. The method of claim 2,
Wherein the voltage sensitivity is determined according to a line impedance of a plurality of buses.
The apparatus according to claim 1,
Establishing a power equation according to the power grid configuration of the DC distribution system and calculating a voltage sensitivity matrix from the inverse matrix of the Jacobian matrix according to the established power equation.
5. The apparatus according to claim 4,
The maximum sensitivity of the jth bus among the plurality of buses determined from the maximum value of the j columns of the voltage sensitivity matrix, the voltage of the i < th > bus corresponding to the maximum voltage sensitivity of the j & And calculates the maximum capacity of the distributed generator connected to the j-th bus.
6. The apparatus according to claim 5,
And calculates a maximum capacity of the distributed generator connected to the j-th bus according to the following equation.
[Mathematical Expression]

(Pj: Capacity of the distributed generator connected to the jth bus, Vmax: Maximum allowable voltage per bus, Vi: Voltage of the ith bus corresponding to the maximum voltage sensitivity of the jth bus, Max (j) Voltage sensitivity)

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