JP2012191779A - Voltage controller of power distribution system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that a high-speed arithmetic unit and a number of voltage sensors and detection voltage transmission means are required for tap switching by LRT and SVR because distributed power supplies are connected to a distribution system.SOLUTION: A second voltage/current measuring instrument is provided downstream of a virtual load center point of a distribution line. By using a line impedance Zfrom the measuring instrument to the load center point, measurement information V, Iby the measuring instrument, measurement information V, Iby a first voltage/current measuring instrument installed near the secondary side of LRT and SVR, a line impedance Zto the load center point, and a weighting coefficient α, an estimated voltage V of the load center point is calculated by the following equation: V=|{(1-α)V+αV}-{(1-α)ZI-αZI}|.

Description

  The present invention relates to a voltage control device for a power distribution system, and more particularly to a voltage control device that allows a voltage distribution of a power distribution system to fall within a management range.

  Voltage control methods for distribution systems include on-load tap switching transformers (hereinafter referred to as LRT) and automatic voltage regulators on distribution lines (hereinafter referred to as SVR) in distribution substations. Many methods are employed in which the tap position is calculated based on the measured value and the tap position is determined according to the calculated value.

  In SVR or LRT, a target point called a load center point is determined on the terminal side from the installation point of SVR or LRT, the voltage value at the load center point is estimated using the voltage / current measurement value at its own end, and the voltage value is The position of the transformer tap is controlled to be within the proper range.

  In recent years, since many distributed power sources represented by photovoltaic power generation are connected to the distribution system, the error voltage increases only by using the center point voltage calculated based on the measured voltage and current at its own end. There is a possibility that a proper tap selection cannot be performed because the voltage deviates from the voltage management range. As a voltage control method for preventing this, Patent Document 1 and Patent Document 2 are known.

JP2009-65788 JP 2004-56931 A

  Patent Document 1 proposes a method of optimal control by performing optimization using a power flow calculation simulation and a genetic algorithm from the viewpoint of optimally controlling the voltage of the entire distribution system. The method of Patent Document 1 requires a large number of measuring instruments and many computing resources at all times to grasp the entire distribution system, and requires a highly reliable measurement network and a high-speed computing device as a voltage management system. Has a point.

  Patent Document 2 proposes that voltage sensors are installed at a number of positions in the jurisdiction of the SVR, and the line voltage is controlled within the management value while taking into account the voltage distribution of each part and the voltage width of one tap of the SVR. . This Patent Document 2 also requires a large number of voltage sensors and detection voltage transmission means.

  Accordingly, an object of the present invention is to provide a voltage control device for a distribution system that reduces the number of components and enables tap switching with high accuracy without departing from the voltage management range.

The present invention relates to measurement information V ₀ , I ₀ by the first voltage / current measuring instrument installed on the distribution line near the secondary side of the load tap switching transformer or the automatic voltage regulator, and the voltage / current measurement. In the tap switching control according to the calculated voltage using the line impedance Z ₀ to the virtual load center point provided downstream of the installation point of the device,
A second voltage / current measuring device is provided on the downstream side of the distribution line from the virtual load center point, and detection information V ₁ , I ₁ by the voltage / current measuring device and a second voltage / current measurement from the load center point are provided. The estimated voltage V at the load center point is calculated by the following equation using the line impedance Z ₁ up to the installation point, and tap switching control is performed using the difference voltage between the calculated estimated voltage and a preset reference voltage. It is characterized by doing.
V = | {(1-α) V ₀ + αV ₁ } − {(1-α) Z ₀ I ₀ −αZ ₁ I ₁ } |
However, α is a weighting factor. The present invention is characterized in that the weighting factor α and the line impedances Z ₀ and Z ₁ are obtained so that the error of the calculated estimated voltage V at the load center point is minimized. is there.

Furthermore, the present invention provides the weighting factor α, the line impedances Z ₀ and Z _1, and the target value of the calculated estimated voltage V at the load center point with respect to various load patterns of the distribution line, The optimum value after simulation is used.

As described above, according to the present invention, in addition to the voltage / current on the secondary side of the conventional device, the load can be obtained with simple information using the voltage / current information at an arbitrary point downstream from the virtual load center point and the three parameters. The voltage at the center point is estimated, and tap switching control is performed based on the deviation between the estimated value and the reference voltage.
This makes it possible to estimate the voltage at the center point of the load regardless of “light load” and “heavy load + power generation” with a simple control device, and to perform tap switching control with high accuracy without departing from the management range voltage. Is.

The block diagram which shows embodiment of this invention. The block diagram of the control apparatus of this invention. The control flow figure of this invention. Comparison chart by simulation.

  FIG. 1 is a partial system diagram of a distribution line showing an embodiment of the present invention. 1 is a distribution line, 2 is an automatic voltage regulator (or a load-tap switching transformer) installed in the distribution line, and a voltage / current measuring device 3 is installed inside or adjacent to the secondary side. Measure the voltage and current. 4 is a virtual load center point located on the distribution line 1 downstream from the installation point of the voltage / current measuring device 3, 5 is a voltage / current measuring device, and this measuring device 5 is further downstream from the load center point 4. It is provided on the distribution line 1 on the side. Of course, the voltage / current measuring instrument 5 may be installed in a switch installed at an arbitrary point of the distribution line without being newly installed.

Reference numeral 6 denotes a communication device, and the voltage / current detected by the voltage / current measuring instrument 5 is transmitted to the control device 10 via the communication device 6. The control device 10 receives the voltages V ₀ and I ₀ measured by the voltage / current measuring instrument 3 and the voltages V ₁ and I ₁ measured by the voltage / current measuring instrument 5 and inputs the estimated voltage V at the load center point 4. Is calculated.

FIG. 2 shows a schematic functional configuration diagram of the control device 10, and the estimated voltage value V is calculated by the estimated voltage calculation unit 11 based on the equation (1).
V = | {(1−α) V ₀ + αV ₁ } − {(1−α) Z ₀ I ₀ −αZ ₁ I ₁ } | (1)
Here, Z ₀ is the line impedance from the automatic voltage regulator 2 to the load center 4, Z ₁ is the line impedance from the load center 4 to the voltage / current measuring instrument 5, and α is the weight of the voltage / current measuring instrument 5. Thus, α = L ₀ / (L ₀ + L ₁ ) (where L ₀ is the distance from the measuring device 3 to the load center point 4 and L ₁ is the distance from the load center point 4 to the measuring device 5). .

  A deviation calculator 12 calculates a deviation voltage ΔV between the calculated estimated value V and a reference voltage Vref preset as a target voltage at the load center point. A determination unit 13 outputs a tap lowering command after a certain operation time if the deviation voltage ΔV exceeds a preset dead band, and outputs a tap raising command after a certain operation time if negative. Reference numeral 14 denotes a voltage adjustment relay unit, which executes a tap changing operation according to whether the deviation voltage ΔV is positive or negative. The functions from 12 to 14 are the same as those in the conventional SVR control.

FIG. 3 shows an operation flow of the control device shown in FIG.
In step S1, the estimated voltage calculation unit 11 takes in the voltage / current V ₀ , I ₀ , V ₁ , I ₁ measured by the voltage / current measuring devices 3 and 5 at a predetermined sampling interval.
In step S2, the voltage V of the virtual load center point 4 is estimated by executing the calculation of the equation (1) using the acquired voltage / current value and three preset parameters α, Z ₀ and Z _1. .

In step S3, the deviation voltage ΔV is obtained by calculating ΔV = V−Vref using the estimated voltage V and the reference voltage Vref input to the deviation calculator 12. The determination unit 13 counts the tap-up and tap-down time limit counters in the addition or subtraction direction using the value of ΔV input in step S4. At that time, the count amount varies depending on the difference in the counting method of time integration or time integration, but when the absolute value of ΔV exceeds the dead zone, the dead time zone is added by adding the time count of tap down or tap up by the positive or negative of ΔV. When entering, the timed count is subtracted.

  In step S5, it is determined whether or not the time count has exceeded the set value. If it has exceeded, tap lowering or tap raising control is performed via the voltage adjusting relay unit 14 in step S6 to change the tap. Reset timed count after operation. In step S7, the next cycle is waited. When the next cycle is reached, the operation is restarted from step 1.

FIG. 4 is a voltage distribution diagram of the simulation result.
Lines A and B are voltage distribution curves according to the present invention. Line A is a light load, line A is a heavy load + power generation, and lines A 'and A' are voltages when conventional appropriate tap selection cannot be performed. In the distribution curve, line A ′ is selected when the same tap as line A is selected at light load, and line A ′ is when the same tap as line A is selected at heavy load + power generation. UL is the upper limit of the voltage management range, and LL is the lower limit of the voltage management range. The simulation was performed with the parameters of the present invention being α = 0.5, the line impedances Z ₀ and Z ₁ being 2% each, α = 0 in the conventional case, and the reference voltage being 6660V.

As is apparent from FIG. 4, in the conventional case, both the “light load” pattern with a light load and the “heavy load + power generation” in which the load is heavy but the power generation that compensates for it is in the system. Since the currents detected at the installation point L1 of 3 are almost the same, the two patterns cannot be distinguished. However, in the case of the voltage of about 6700 V in the line A ′ pattern at the time of “light load” at the time of L1 and the voltage of about 6800 V in the line A ′ at the time of “heavy load + power generation”, the light load curve curve “ In the range exceeding the distance L3 from the vicinity of the load center point L0, the upper limit UL is exceeded near the installation point L4 of the voltage / current measuring instrument 5 in the heavy load + line A during power generation. Deviates.
On the other hand, in the case of the line a and b according to the present invention, the voltage is within the voltage management range UL and LL.

FIG. 4 is obtained by the equation (1) with the weight α = 0.5 obtained from the ratio of the reciprocal of the distance between the measurement point 3 and the measurement point 5 and the load center point, and the line impedances Z ₀ and Z ₁ being 2%, respectively. The estimated value is used. In order for the voltage distribution curve to fall within the control ranges UL and LL with high accuracy regardless of whether the voltage distribution curve is “light load” or “heavy load + power generation”, the above three parameters are set so that the error of the estimated value is minimized. Alternatively, the power flow of the entire system is simulated with respect to various load patterns, and optimum set values are used for the weight coefficient α and the line impedances Z ₀ and Z ₁ so that the voltage deviation of the system is minimized. You may do it. In this case, an optimum set value for calculating the reference voltage at the same time is used.

As described above, the present invention estimates the voltage at the load center point based on the conventional SVR method using simple information using voltage / current information at the downstream of the load center point and three parameters, and the estimated value and the reference Tap switching control is performed based on the deviation from the voltage.
This makes it possible to estimate the voltage at the load center point regardless of “light load” or “heavy load + power generation” with a simple control device, and tap switching can be performed accurately without departing from the management range voltage. is there.

1 ... Distribution line 2 ... Automatic voltage regulator (or load tap change transformer)
DESCRIPTION OF SYMBOLS 3 ... 1st voltage and current measuring device 4 ... Virtual load center point 5 ... 2nd voltage and current measuring device 6 ... Communication apparatus 10 ... Control apparatus 11 ... Estimated voltage calculating part 12 ... Deviation calculating part 13 ... Judgment part 14 ... Voltage adjustment relay

Claims (3)

Measurement information V ₀ , I ₀ by the first voltage / current measuring device installed on the distribution line near the secondary side of the tap-switching transformer or automatic voltage regulator, and the installation point of this voltage / current measuring device In the tap switching control according to the calculated voltage using the line impedance Z ₀ to the virtual load center point provided downstream of
A second voltage / current measuring device is provided on the downstream side of the distribution line from the virtual load center point, and detection information V ₁ , I ₁ by the voltage / current measuring device and a second voltage / current measurement from the load center point are provided. The estimated voltage V at the load center point is calculated by the following equation using the line impedance Z ₁ up to the installation point, and tap switching control is performed using the difference voltage between the calculated estimated voltage and a preset reference voltage. A voltage control device for a distribution system characterized by
V = | {(1-α) V ₀ + αV ₁ } − {(1-α) Z ₀ I ₀ −αZ ₁ I ₁ } |
Where α is the weighting factor 2. The voltage control apparatus for a distribution system according to claim ₁ , wherein the weighting coefficient α and the line impedances Z ₀ and Z ₁ are obtained so that the error of the calculated estimated voltage V at the load center point is minimized. Optimum after simulation of the overall power flow of the distribution line with respect to various load patterns of the distribution line to the target values of the weight coefficient α, the line impedances Z ₀ and Z ₁ and the calculated estimated voltage V of the load center point The voltage control device for a distribution system according to claim 1, wherein a value is used.

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