KR101997439B1 - Method for predicting voltage based on part measurement for controlling voltage and reactive power, program for the same - Google Patents

Abstract

The present invention relates to a method for predicting, based on partial measurements, a voltage profile in a bus line used for voltage and reactive power control in a distribution system. The method predicts a range of voltages which can be the voltage profile of the interval between measurement points, thereby minimizing a voltage violation situation in accordance with a prediction error.

Description

METHOD FOR PREDICTING VOLTAGE BASED ON PART MEASUREMENT FOR CONTROLLING VOLTAGE AND REACTIVE POWER, PROGRAM FOR THE SAME BACKGROUND OF THE INVENTION 1. Field of the Invention < RTI ID = 0.0 > [0001] <

The present invention relates to a method and a program for predicting a voltage on a bus line used for voltage and reactive power control in a distribution system based on a partial measurement.

Consumer loads of consumers mainly consist of heating, lighting, motors, electronic devices providing various services, computers and controllers, battery charging devices of mobile devices, and electrochemical devices mainly used in industry. All these loads are designed to be used reliably at the nominal supply voltage. Therefore, electric power companies must supply electric power of a certain voltage range to the customers by voltage regulation. However, recently, there is a tendency to reduce the use of fossil fuels, and at the same time, interest in Distributed Generation (DG) using renewable energy is increasing worldwide.

The introduction of distributed power sources that distribute small- and medium-scale power sources such as renewable energy wind power generation, solar power generation, and small cogeneration power generation has been greatly increased, and a typical power distribution system infrastructure and operation method has a limit to accommodate large-capacity distributed power sources . As a result, voltage problems such as deviation of the specified voltage and deterioration of the electrical quality are caused by the technical problems that can occur. However, it is difficult to add equipment to maintain power quality whenever distributed power is added to the distribution grid. Therefore, it is necessary to study the system to control the reactive power or to install the voltage regulating equipment because the most important limitation in connection with the renewable energy system is the voltage problem in the connection standard. At present, KEPCO is carrying out an empirical test on appropriate solutions and technological measures for the problem of proper voltage deviation of distribution system due to the connection of distributed power. To meet these trends, it is necessary to develop a voltage control technology for the distribution system considering distributed power sources in order to expand the distributed power supply linkage. In the past, a voltage control method using partial measurement has been proposed. However, the prior art has assumed that the load between the sections is concentrated at the central point. Such an assumption causes an error in voltage prediction and causes a voltage violation. The following technologies have been proposed as partial measurement based voltage and reactive power control technology.

Prior Art Document 1 Korean Patent Registration No. 10-1132107 discloses a voltage calculating unit for calculating a voltage of a node corresponding to a point where a distributed power source is connected to a power system by using at least one of a voltage, A control variable calculating unit for calculating a value of the control variable such that the objective function becomes a minimum value by using an objective function including at least one control variable for controlling the applied voltage; And a control unit for controlling at least one of a voltage and a reactive power of the power system by controlling the distributed power source together with the other control apparatus as the control variable according to the value of the control variable, wherein the voltage of the node corresponding to the point where the distributed power source is connected is calculated by using the formula calculated by applying constants of four terminals to the voltage / reactive power control system of the power system connected to the distributed power source. Lt; / RTI >

Prior Art Document 2 Korean Patent Laid-Open No. 10-2013-0011163 discloses a control for controlling a phase angle input to the stationary reactive power compensation device so that the reactive current output from the stationary reactive power compensating device coincides with the command value for the reactive current An instruction calculating unit for calculating a command value for the phase angle and a command value for a state variable output from the stationary reactive power compensation apparatus by using a command value for the reactive current; A feedback control signal generator for generating a feedback control signal using an error between the command value for the state variable and the state variable; And a phase angle calculating unit for calculating the phase angle using the command value for the phase angle, the command value for the state variable, the error, and the feedback control signal, A reactive current, and a DC voltage output from the reactive power compensating unit, the reactive current, the reactive current, and the DC voltage output from the reactive power compensating unit.

1. Korea registered patent No. 10-1132107 (public announcement date: April 04, 2012) 2. Korean Patent Publication No. 10-2013-0011163 (Publication date: 2013.01.30)

Accordingly, it is an object of the present invention to provide a voltage profile prediction method and a program capable of minimizing a voltage violation according to a prediction error of a voltage profile.

A method for predicting a voltage in a bus for a partial measurement based voltage and reactive power control according to a preferred embodiment of the present invention includes the steps of: acquiring a measured value on an essential measurement point for predicting a voltage profile of a system; And predicting a voltage profile using the obtained measurement value.

Here, the voltage profile may be a maximum value and a minimum value of the voltage drop of the measurement point section bus line.

Then, the following equation

From here,

: 구간 임피던스

: Section impedance

: 구간 부하전류 및 전압

: Section load current and voltage

Predicts the range of the voltage in each section,

The two constraints of the objective function are

Lt; / RTI >

Further, the following equation

From here,

: 구간 임피던스

: Section impedance

: 구간 부하전류 및 전압

: Section load current and voltage

Predicts the voltage range in each section,

The two constraints of the objective function are

Lt; / RTI >

Further, the following equation

From here,

: 구간 임피던스

: Section impedance

: 구간 부하전류 및 전압

: Section load current and voltage

Predicts the range of the voltage in each section,

The three constraint conditions of the objective function are

Lt; / RTI >

According to another aspect of the present invention, there is provided a computer readable medium storing a computer readable program for performing a voltage predicting method on a bus for controlling a voltage and a reactive power based on a partial measurement, You can provide more.

Further, the present invention provides a computer program product for storing a voltage prediction program in a bus for controlling a partial measurement-based voltage and a reactive power and transmitting the voltage estimation program in a bus for the partial measurement based voltage and reactive power control via a communication network System can be further provided.

According to another aspect of the present invention, there is provided a voltage predicting program for a voltage-controlled and reactive power control device, comprising: a voltage predicting program for a partial measurement-based voltage and a reactive power; A Smart Distribution Management System (SDMS), a Distribution Management System (DMS), and a Distribution Automation System (DAS), which perform voltage prediction on a bus for reactive power control. can do.

The present invention predicts a range of voltage that can be a voltage profile of a section between measurement points, so that a voltage violation situation according to a prediction error can be minimized.

1 is a diagram for explaining application of a method for selecting a peak voltage measurement point;
2 is a diagram for explaining application of the lowest voltage measurement point selection method;
3 is a diagram for explaining the voltage calculation (voltage prediction 1) of the measurement point section bus line
Fig. 4 is a diagram for explaining the voltage calculation (voltage prediction 1) of the measurement point section bus line
FIG. 5 is a graph showing the voltage prediction result by the voltage prediction 1
6 is a diagram for explaining a predicted voltage range according to application of a range of load current
7 is a diagram for explaining derivation of a current constraint condition in a load current pattern;
Fig. 8 is a diagram for explaining that the range of the lower current is reflected as the upper zone constraint condition
9 is a diagram for explaining the voltage calculation (voltage prediction 2) of the measurement point section bus line
Fig. 10 shows a case system for comparison of load pattern application and non-use
Fig. 11 is a graph showing the comparison between the application of the load pattern and the unpredictable voltage prediction (0 to 0.5 MVA)
Fig. 12 is a graph showing the comparison of the application of the load pattern and the unpredictable voltage prediction (0.3 to 0.7 MVA)
13 is a graph showing the voltage prediction result by the voltage prediction 2
FIG. 14 is a graph showing the voltage prediction result by the voltage prediction 3

end. Positioning the instrument for voltage and reactive power control

Select the required measurement points to predict the voltage profile of the system. Since the voltage of the system should be operated within the operating voltage range, it is necessary to measure the point required for the maximum and minimum voltage prediction, or directly measure the maximum and minimum voltage. The data required to select the measurement points are topology data and system load or voltage history data. Measuring elements are voltage magnitude (V) and current magnitude (I).

The present invention selects an essential metrology point on the system to predict the voltage profile of the system. Then, the voltage profile is predicted using the measured values on the required measurement points. The voltage profile is in the form of a maximum voltage value and a minimum voltage value in the prediction period.

1) Selecting the point where the peak voltage can occur

The point at which the highest voltage occurs in a typical power distribution system can be divided into several cases. In the radial system, the top point of the system can be the highest voltage in the system. The best voltage can be generated at the point where the equipment that changes the voltage profile and raises the voltage of the system is connected. The equipment for transforming the voltage profile of the power distribution system is a distributed power source or a reactive power control device. The following is summarized. FIG. 1 shows an example in which a point at which a maximum voltage can be generated is selected as a measurement point.

- Output point on topology: M.tr secondary (V, I), SVR secondary (V, I)

- Point where voltage rise occurs: Distributed power connection point (V, I), reactive power control device connection point (V, I)

2) Selection of the point where the lowest voltage can occur

The point at which the lowest voltage is generated in the general front distribution system is the radial end point. Therefore, the lowest voltage generation point can be selected at the end of the grid line. Fig. 2 shows an example of applying the proposed measurement point selection method.

  - main feeder end and branch line end point (V, I)

  - SVR primary (V, I)

3) Branch point of the branch line

The measurement of the branch line is important for the measurement because the current flow is separated due to the characteristics of the power distribution system voltage. The system measures the voltage at the point where the branch line starts and the current measures the current going out to each branch line. However, a branch line is a very short line segment or a branch line with a very small load is negligible if the voltage drop is not so small that the voltage control is not affected.

I. Partial metrology based voltage profile prediction

Since the existing voltage and reactive power are controlled based on the global measurement, the number of measuring instruments is increased, communication equipment is required, and a large cost is incurred. In order to overcome these shortcomings, we proposed a voltage estimation method which can achieve similar effects to global measurement by partial measurement.

When the distributed power supply is operated in conjunction with the power distribution system, the influence of the distributed power supply is considered to be essential for the voltage prediction because it modifies the voltage drop characteristics of the power distribution system. The voltage fluctuation caused by the distributed power supply or the reactive power control apparatus which changes the voltage drop characteristic of the grid voltage is distinguished from the principle of superposition. Using the voltage variation due to the divided load, the following voltage prediction can be performed.

1) Measurement Prediction of Measurement Point and Measurement Point Interval (Voltage Prediction 1) (First Embodiment)

)과 전류(

)를 계측한다. 계측지점 구간 모선의 전압 강하는 식 4.1과 같이 나타낼 수 있다. 각 모선의 전압강하는 시작 모선 전압(

)과 각 모선의 전압의 차이이다.The voltage drop of each bus line in the measurement voltage section can be expressed as shown in FIG. FIG. 3 is a schematic diagram for obtaining the voltage between measurement intervals. The voltage at the measuring point (

) And current (

). The voltage drop of the bus line at the measurement point can be expressed as Eq. 4.1. The voltage drop of each bus line is the starting bus voltage (

) And the voltage of each bus line.

(4.1)

(4.1)

From here,

: 구간 임피던스

: Section impedance

: 구간 부하전류 및 전압

: Section load current and voltage

From the derived equation (4.1), the objective function can be derived as in (4.2).

(4.2)

(4.2)

)와 나가는 전류(

)로부터 구간 부하 전류의 합을 구할 수 있다. 전류 법칙에 의해 유입되는 전류에서 나가는 전류를 빼면 구간 부하 전류의 합과 같아진다. 그러므로 계측된 전류로부터 식 (4.3)과 같이 전류 제약 조건을 도출한다.Current flowing into the section (

) And outgoing current (

The sum of the section load currents can be obtained. Subtracting the outgoing current from the current drawn by the current law is equal to the sum of the section load current. Therefore, the current constraint is derived from the measured current as shown in Eq. (4.3).

(4.3)

(4.3)

 From here,

: 계측 전류

: Measurement current

)과 끝 모선의 전압(

)으로부터 구간 말단 모선의 전압 강하를 구할 수 있다. 식 (4.1)의 전압 강하 식에 적용하면, 시작 모선의 전압과 끝 모선 전압 차이는 말단 모선의 전압강하와 같다. 그러므로 계측된 전압으로부터 식 (4.4)과 같이 전압 제약 조건을 도출한다.Start bus voltage (

) And the voltage of the end bus (

The voltage drop of the terminal end bus line can be obtained. Applying to the voltage drop equation in Eq. (4.1), the difference between the voltage at the start bus and the voltage at the end bus is the same as the voltage drop at the terminal bus. Therefore, the voltage constraint is derived from the measured voltage as shown in Eq. (4.4).

(4.4)

(4.4)

From here,

: 계측 전압

: Measurement voltage

Applying the current and voltage conditions as an equation constraint allows optimization of the current. Linear optimization can yield the highest possible voltage and the lowest possible voltage for each busbar. The voltage range of the bus line of the measurement point section is determined by the derived maximum and minimum voltages. The linear optimization standard is Equation (4.5) as follows.

(4.5)

(4.5)

The objective function of the linear optimization by applying the derived optimization condition is as follows. Since the maximum voltage and the minimum voltage are obtained for each bus, the optimization objective function is represented by two equations (4.6) and (4.7).

(4.6)

(4.6)

(4.7)

(4.7)

In the derived condition, the equation constraint can be expressed as follows (4.8) and (4.9).

(4.8)

(4.8)

(4.9)

(4.9)

Using the simulation system shown in FIG. 4, the voltage profile was predicted in a system including a distributed power source.

The voltage between the measurement point and the measurement point is expressed as a range, and the result is shown in FIG. As a result of the estimation of the voltage, the maximum error range was found to be 0.47% (0.0047p.u) difference on bus 12.

2) When the current measurement can not be made Voltage Prediction (Voltage Prediction 2) (Second Embodiment)

If the current can not be measured, the prediction method is different. If only the voltage is measured, there is no current restriction condition, and the highest minimum voltage range is determined in a right triangular shape as shown on the left side of FIG. However, if the range of the load current is known as shown in Equation (4.10) through analysis of the past load data, the range of voltage prediction can be narrowed.

(4.10)

(4.10)

From here,

: 최저 부하 전류

: Minimum load current

: 최대 부하 전류

: Maximum load current

Load current analysis can be used as a constraint through past load data analysis. 7, the maximum load current was set to the maximum value and the minimum load current was set to the minimum value in the pattern of the load current. From Fig. 7, the final constraint condition is represented by equation (4.11).

(4.11)

(4.11)

The load current range can be determined from the lower section of the system topology to the lower current range. 8 shows the outgoing current of each section and the outgoing current at the end is zero. Since the outgoing current can be set to 0 in the terminal section, the current range can be derived from the terminal section in order. Fig. 9 schematically illustrates the prediction method. The range of the current is derived while deriving the range of the voltage for the terminal section, so that the obtained section current range is reflected in the upper range voltage prediction constraint. In this way, we derive from end to top. The range current range can be expressed as Eq. (4.12).

(4.12)

(4.12)

here,

: 구간에서 나가는 최소 전류 크기

: Minimum current size out of range

: 구간에서 나가는 최대 전류 크기

: Maximum current out of range

Using the measured voltage and load pattern, predict the voltage between measurement points. The prediction is made using the same linear optimization method as the voltage prediction 1 scheme.

The voltage drop is expressed as an objective function as in (4.13).

(4.13)

(4.13)

 Equation (4.12) is included as a constraint. Apply the current range of the subsection to the voltage drop equation (4.4) to obtain additional inequality constraints. The current range of the subdivision is represented by the voltage constraint and is given by the following equations (4.14) and (4.15).

(4.14)

(4.14)

(4.15)

(4.15)

Add the load current range as an inequality constraint. And the lower current range is added as an inequality constraint. Linear optimization determines the voltage range of the measurement point interval bus.

The linear optimization standard is equation (4.16) as follows.

(4.16)

(4.16)

The objective function of the linear optimization by applying the derived optimization condition is as follows. Since the maximum voltage and the minimum voltage in each bus are obtained, the optimization objective function is represented by two equations as shown in Eq. (4.17).

(4.17)

(4.17)

Equation constraints and inequality constraints in derived conditions can be expressed by Equation (4.18) as follows.

(4.18)

(4.18)

In order to confirm the influence of the application and non-use of the load pattern on the voltage prediction, a case study was conducted with a simple system as shown in FIG. Load and line impedance were arbitrarily selected.

When the load pattern is not applied, the constraint is not applied to Fig. 11, so that the voltage is predicted in a triangular shape. Therefore, since the voltage range error is large as shown in Fig. 11, the applicability becomes low. When the load pattern is applied, the voltage prediction range is narrowed as shown in FIG. Fig. 11 shows the voltage range when the load range is 0 to 0.5 MVA, and Fig. 12 shows the voltage range when the load range is 0.3 to 0.7 MVA. A simple case study confirms that the error of voltage prediction is considerably reduced when the load pattern is applied.

Using the simulation system of FIG. 4, the voltage between the measurement points was predicted. At the measurement points, only the voltage was measured, the range of the load current was derived from the load pattern, and the voltage was predicted by applying the linear optimization. Figure 13 shows the prediction results and the maximum voltage range error is 0.48% (0.0048p.u) on bus # 3.

3) Voltage Prediction Using Measurement and Load Pattern (Voltage Prediction 3) (Third Embodiment)

This method is used when the current can be measured and past load data analysis is possible. Apply equality constraints and inequality constraints at the same time. Linear optimization determines the voltage range of the bus at the measurement point. We add the current constraint of Eq. (4.19) to Eqs. (4.3) and (4.4).

(4.19)

(4.19)

The linear optimization standard is Equation (4.20) as follows.

(4.20)

(4.20)

The objective function of the linear optimization obtained by applying the derived voltage drop equation is as follows. Since the maximum voltage and the minimum voltage at each bus are obtained, the optimization objective function is represented by two equations (4.21).

(4.21)

(4.21)

In the derived condition, the inequality constraint and the equality constraint can be expressed as (4.22).

(4.22)

(4.22)

Using the simulation system of FIG. 4, the voltage between the measurement points was predicted. At the measurement points, voltage and current were measured, the range of load current was deduced from the load pattern, and linear optimization was applied to predict the voltage. Fig. 14 shows the prediction result. The maximum voltage range error of 0.44% (0.0044p.u) occurred on bus 11. Compared to the other two methods, the prediction error is relatively small.

From the simulation results of the three voltage prediction methods, the voltage range was predicted for each method and it was confirmed that the actual voltage value is within the predicted range. It can be seen that voltage prediction error 3, which is a method to utilize all information, has the smallest voltage prediction error range.

In addition, the voltage predicting method in the bus for the partial measurement-based voltage and reactive power control according to an embodiment of the present invention can be practically applied to a computer system equipped with a voltage predicting program on the bus for the partial measurement based voltage and reactive power control Lt; / RTI >

That is, the present invention may be provided in the form of a computer, a smart distribution operation system, a distribution operation system or a distribution automation system in which a voltage prediction program in a bus for the partial measurement based voltage and reactive power control is stored.

The voltage predicting program in the bus for the partial measurement-based voltage and reactive power control is stored in a server system, and the computer system receives the voltage estimation in the bus for the partial measurement-based voltage and reactive power control from the server system After the program is downloaded and installed, voltage prediction (voltage profile calculation in the measurement point interval) can be performed.

In addition, the voltage prediction program in the mother bus for the partial measurement-based voltage and reactive power control may be separately stored in a recording medium, and the recording medium may be provided specially designed for the present invention, For example, a magnetic medium such as a hard disk, a floppy disk and a magnetic tape, an optical recording medium such as a CD and a DVD, a magnetic recording medium such as a magneto- An optical recording medium, a ROM, a RAM, a flash memory, or the like, or a hardware device specially configured to store and execute program instructions by a combination thereof.

In addition, the voltage prediction program on the bus for the partial measurement-based voltage and reactive power control may be a program consisting of a program command, a local data file, a local data structure, or the like, Code, as well as a program organized into high-level language code that can be executed by a computer using an interpreter or the like.

Claims (7)

Obtaining a measured value on an essential metrology point for predicting the voltage profile of the system; And
And estimating a voltage profile using the obtained measured value,
The following objective function

From here,

: Section impedance

: Section load current and voltage
Predicts the range of the voltage in each section,
The three constraint conditions of the objective function are

And a voltage predicting method in a bus for a partial measurement based voltage and reactive power control. The method according to claim 1,
Wherein the voltage profile is a maximum value and a minimum value of the voltage drop of the measurement point section bus line. A program for predicting voltage in a bus for controlling voltage and reactive power based on partial measurement stored in a medium for performing the voltage prediction method according to any one of claims 1 and 2 in combination with a computer. The server system according to claim 3, wherein the voltage prediction program is stored and the voltage prediction program can be transmitted through a communication network. A Smart Distribution Management System (SDMS) that stores the voltage prediction program of claim 3 and predicts a voltage profile at a measurement point section by the voltage prediction program. A Distribution Management System (DMS) that stores the voltage prediction program of claim 3 and predicts a voltage profile at a measurement point section by the voltage prediction program. A distribution automation system (DAS) that stores the voltage prediction program of claim 3 and predicts a voltage profile at a measurement point section by the voltage prediction program.

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