JP2005080457A - Electric power system synchronously paralleling method and synchronously making device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power system synchronously paralleling method and a synchronously making device that can expand system making conditions while securing the accuracy of synchronous making and that can parallel systems speedily without missing the timing of synchronous paralleling. <P>SOLUTION: In the electric power system synchronously paralleling method in which a plurality of the electric power systems are synchronously paralleled, a frequency difference Δf and a phase difference Δδ of power supplies of two systems to be synchronously paralleled are detected. Using the frequency difference Δf and phase difference Δδ, a value of energy function: U shown in the figure, where M: unit inertial constant (sec) of a single system, Δω: an angular frequency difference of two systems 2πΔf(rad/sec), X: impedance of a single system (p, u based on system capacity), Δδ: a radian value of the phase difference of the two systems 2πΔθ(° )/360(rad/sec), is calculated. On condition that the value of the energy function: U has come into a preset permissible range, a synchronously inputting command is output to a breaker 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power system synchronous parallel method and a synchronization input device for synchronously paralleling a plurality of power systems, and more particularly to a method for quickly paralleling separated power systems in an emergency.

  When a single system occurs due to a grid fault while the supply-demand balance in a large-scale power system is unbalanced, measures are taken to maintain a single system by cutting off some loads. In such a case, if it takes time to synchronize and reconnect the single system again, the power outage in the partly loaded area becomes longer and adversely affects social activities.

When two separated power systems (or generators) are to be connected in parallel, it is desirable that the following conditions are satisfied. (1) Both voltages should be as equal as possible. (2) Both frequencies should be as equal as possible. (3) Both phases should be as equal as possible. Therefore, for example, the voltage difference ΔV, frequency difference Δf, and phase difference Δφ of the separated power system (or generator) are equal to or less than the set voltage difference SV, the set frequency difference Sf, and the set phase difference Sφ. In this case, a technique is adopted in which a closing instruction is issued to the circuit breaker and the two are synchronized and paralleled (see Patent Document 1 and FIGS. 7A and 7B).
Japanese Patent Laid-Open No. 9-130978

  In this method, the mere instantaneous value of the voltage, frequency, or phase is evaluated. Even if the voltage, frequency, or phase falls below the set value, the circuit breaker actually operates after a delay time required for the operation of the circuit breaker. However, there is a case where the set value may be exceeded before the parallel operation is started, and there is a problem that the accuracy of the synchronization input is lacking.

  Therefore, a method of performing a predictive control in which a sample of the voltage, frequency, or phase is periodically taken and a closing command is output to the circuit breaker so that parallel operation can be performed with zero phase difference using the change over time of the sample. However, because this method performs predictive control on the assumption that the phase difference becomes zero, there may be a case where the phase difference cannot reach zero due to the temporal change of the sample. In this case, the standby time is often redundant and the system cannot be turned on in many cases.

  In order to solve such a problem, not only the instantaneous values are compared as in the previous method, but also the voltage difference ΔV, the frequency difference Δf, and the two separated power systems (or generators), and When the phase difference Δφ stays within a predetermined range for a certain period of time, a method has been adopted in which a closing command is issued to the circuit breaker to perform synchronous charging.

  However, in this method, since it is necessary to stay for a certain period of time, there is a problem that if the staying time is short, the system cannot be turned on, the system separation state continues for a long time, and there is a great risk of power failure. In addition, since control is performed while paying attention to individual requirements such as voltage, frequency, or phase, there is also a problem that includes a factor that narrows the condition setting that can be normally turned on and prolongs the state of system separation.

  An object of the present invention is to solve the problems of the above-described conventional method, expand the system input conditions while ensuring the accuracy of the synchronization input, and perform synchronous parallel of the power system that can be quickly synchronized in parallel without missing the timing of synchronization input It is in providing a method and apparatus.

ここで、Ｍ ：単独系統の単位慣性定数（sec）
Δω：二系統の角周波数差２πΔｆ（rad/sec）
Ｘ ：単独系統のインピーダンス（系統容量ベースのp.u）
Δδ：二系統の位相差のラジアン値：２πΔθ（°）/360（rad/sec）
の値を算出し、当該エネルギー関数：Ｕの値が予め設定した許容範囲内になったことを条件として遮断器に対し同期投入指令を出力する電力系統の同期並列方法である。 Means for solving the above-described problem is based on the power supply frequency difference Δf and the phase difference Δδ between the two systems that are synchronously paralleled.

Here, M: Unit inertia constant of single system (sec)
Δω: Angular frequency difference between two systems 2πΔf (rad / sec)
X: Impedance of single system (system capacity based pu)
Δδ: Radian value of phase difference between two systems: 2πΔθ (°) / 360 (rad / sec)
This is a synchronous parallel method of a power system that calculates the value of the energy function and outputs a synchronous input command to the circuit breaker on condition that the value of the energy function U is within a preset allowable range.

  The condition that the value of the energy function: U is within a preset allowable range is, for example, that the value is synchronized with the circuit breaker when the value of the energy function: U is within a preset allowable range. An input command may be output, or the energy function: the energy function is calculated from the power supply frequency difference Δf and the phase difference Δδ of the two systems to be synchronized in parallel on condition that the value of U is within a preset allowable range. : Calculate the value of U by 3 samples or more, and derive each approximate energy function: U (t) from the calculated energy function: U value and derive an approximate expression U (t) of the quadratic function indicating temporal change of U : It is also possible to calculate an estimated time at which U (t) takes the minimum value, and output a synchronous input command to the circuit breaker at a timing that is synchronously parallel to the estimated time.

  In addition, as a device that embodies the synchronous parallel method, the current calculation means for calculating the value of the energy function: U, and whether the value of the energy function: U is within a preset allowable range are determined. A power system comprising: a current state determination unit; and a command output unit that outputs a synchronous input command to the circuit breaker on condition that the value of the energy function U is within a preset allowable range by the current state determination unit. A synchronous input device may be mentioned.

  Then, the condition for performing the synchronous input is specifically determined, for example, the synchronous input command output means for outputting a synchronous input command to the circuit breaker when the value of the energy function: U falls within a preset allowable range. And the power function frequency difference Δf and the phase difference Δδ of the two systems to be synchronously paralleled on the condition that the value of the energy function: U is within a preset allowable range, and each sample In the energy function: U, the estimation calculation means for calculating the value of U for three samples or more, and each energy function: an approximate expression of a quadratic function indicating a temporal change of the energy function: U from the value of U: U ( t), and at the same time, the approximate equation: U (t) calculates the estimated time at which the estimated value takes the minimum value, and the circuit breaker at the timing synchronously parallel to the estimated time Forms with said command output means for outputting the synchronous closing command against the possible is employed.

  According to the synchronous parallel method and apparatus of the power system according to the present invention, the system can be switched on without missing the timing suitable for synchronous switching, so that the power failure time can be shortened and adverse effects caused by the power failure can be minimized. It becomes possible.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a power system synchronous parallel method according to the present invention will be described below with reference to the drawings.
The power system synchronous parallel method shown below is based on the condition that even if the frequency difference Δf or phase difference Δδ between the two systems to be synchronized in parallel does not become zero, the fluctuations generated after the system parallel are within the allowable range. It creates an opportunity for appropriate system introduction.

ここで、Ｍ ：単独系統の単位慣性定数（sec）
Δω：二系統の角周波数差２πΔｆ（rad/sec）
Ｘ ：単独系統のインピーダンス（系統容量ベースのp.u）
Δδ：二系統の位相差のラジアン値：２πΔθ（°）/360（rad/sec） The permissible range is defined by the following energy function U (Δω, Δδ) that represents the degree of generator oscillation (hereinafter referred to as system oscillation) of the power system when the system is turned on.

Here, M: Unit inertia constant of single system (sec)
Δω: Angular frequency difference between two systems 2πΔf (rad / sec)
X: Impedance of single system (system capacity based pu)
Δδ: Radian value of phase difference between two systems: 2πΔθ (°) / 360 (rad / sec)

ここで、ω_ｎ＝２πｆ The system fluctuation increases when the phase difference angle Δδ ₀ and the frequency difference Δf ₀ when a different system is turned on are large, and may cause an excessive voltage drop or step-out in some cases. Here, consider the system fluctuation after the switch is turned on in FIG. If the braking effect is ignored for the sake of simplification, the system oscillation equation is given by the following equation (2).

Where ω _n = 2πf

を掛けると、

となる。 sinΔδ ≒ Δδ, and on both sides of the above (Formula 2)

Multiply

It becomes.

であるから、

となる。 Also,

Because

It becomes.

となる。尚、ここで、ｔ＝０時のΔω及びΔδは、Δω_０及びΔδ_０であって、ｔ＝ｔ時のΔω及びΔδは、Δωt及びΔδtである。 If this is integrated from t = 0 to t,

It becomes. Here, Δω and Δδ at t = 0 are Δω ₀ and Δδ ₀ , and Δω and Δδ at t = t are Δωt and Δδt.

  From this, during the system oscillation, if the attenuation of the oscillation is ignored, the magnitude of the system oscillation before and after the system is turned on is kept constant at the value of the energy function: U described as (Equation 1). . That is, the system fluctuation after the synchronous parallel can be reduced by introducing the system at the timing when the value of the energy function U becomes as small as possible.

  The energy function U is an elliptic orbit function centered on (Δω, Δδ) = (0, 0) with the power supply frequency difference Δf and the phase difference Δδ as variables as described above. Compared to control performed by setting individual tolerance ranges for frequency and phase (see FIG. 4), only one of the frequency or phase is within the tolerance range and a sufficiently normal system can be entered. As a result, there is an advantage that the probability that the system separation state can be resolved more quickly is increased.

  Based on the above principle, the example of the power system synchronous input device shown in FIG. 1 is to output a synchronous power supply command to the circuit breaker (see FIG. 3) 3 for paralleling and disconnecting the two power systems. The input means 9 for taking in the power frequency and phase at the time of each sampling of the two power systems connected to the contacts provided in the circuit breaker 3 from the frequency detection unit 7 and the phase detection unit 8 of the circuit breaker, and the power supply The power frequency difference Δf and the phase difference Δδ between the two power systems are calculated from the frequency and phase, and the value of the energy function: U in (Expression 1) is calculated using the power frequency difference Δf and the phase difference Δδ. Current state calculation means 1, current state determination means 2 for determining whether or not the value of the energy function: U is within a preset allowable range, and the current state determination means 2, the energy function: U There has been an instruction output unit 4 for outputting a synchronous closing command to the circuit breaker 3 on condition that falls within the allowable range set in advance.

  FIG. 2 is a flowchart showing a series of processes by software used when the embodiment of the power system synchronous input device is realized by using a computer system constituted by a CPU, a memory, an input / output port or the like. is there. The input means 9 performs data communication with the frequency detection unit 7 and the phase detection unit 8 of the circuit breaker 3 so that the power supply frequencies and phases of the two power systems to be synchronized in parallel are synchronized with each other at a constant cycle. Capture to the device (step 0). Subsequently, the current state calculation means 1 calculates the power supply frequency difference Δf and the phase difference Δδ as a difference between the power supply frequency and the phase between the two power systems (step 1), and the power supply frequency is expressed in the equation (1). By substituting the frequency difference Δf (Δω) and the phase difference Δδ, the value of the energy function U between the two power systems (hereinafter referred to as the current value) is calculated (step 2). Whether or not the current value is inside the elliptical orbit determined as the allowable range, that is, whether or not the value of the energy function U is smaller than a threshold corresponding to the radius of the elliptical orbit. It is determined whether or not (step 3).

  As a result of the determination, if the current value is smaller than the threshold value set as the allowable range, it is determined that the current value is within the allowable range, and based on the determination, the command output means 4 performs data communication with the circuit breaker 3 through data communication. Will be output.

  In this way, when the current value becomes smaller than the preset allowable range, the command output means 4 may immediately output a synchronous input command to the circuit breaker 3. However, in order to further ensure system parallelism with less fluctuation, the power frequency difference Δf between the two systems to be synchronized in parallel is provided on condition that the value of the energy function U is within a preset allowable range. And the phase difference Δδ and the estimation function means 5 for calculating the value of the energy function U in each sample for three samples or more, and the energy function for the three samples or more: the energy function from the value of U : Approximate expression of a quadratic function indicating temporal change of U: U (t), and at the same time, the input calculation means 6 for calculating the estimated time when the approximate expression: U (t) takes the minimum value, and the estimation You may take the form provided with the said command output means 4 which outputs a synchronous injection | throwing-in instruction | command with respect to the circuit breaker 3 at the timing which becomes synchronous parallel at time.

  That is, if the current value is smaller than the threshold value determined as the allowable range as a result of the determination, it is determined that the current value is within the allowable range, and the frequency detecting unit 7 and the phase of the circuit breaker 3 are further determined by the input means 9. The power supply frequency and phase of the two power systems are fetched from the detection unit 8 (step 4), and the estimation calculation means 5 then uses the two power grids of the two power systems that have been fetched to determine the two systems to be synchronized in parallel. The power supply frequency difference Δf and the phase difference Δδ are calculated (step 5), and the value of the energy function U in each sample is calculated (step 6).

を導く（ステップ７）と共に、当該二次関数が最小値を採る前記推定時刻ｔを導く（ステップ８）。そして、前記指令出力手段４は、前記同期投入指令の送出から前記遮断器３の接点が閉じ、実際に二つの電力系統の並列が開始されるまでの遅延時間（例えば、１５０ｍｓ程度）を考慮した早めの同期投入指令の出力時を算定し（ステップ９）、そのタイミングを逃すことなく同期投入指令を出力する（ステップ１０）。 The charging time calculation means 6 calculates the energy function: U calculated in this way, and three samples from the energy function: U calculated before satisfying the condition that the current value is smaller than the threshold. Approximate expression of the quadratic function indicating the time variation of the extracted energy function: U value and the energy function: U value from the time t when each sample was obtained.

(Step 7) and the estimated time t at which the quadratic function takes the minimum value (Step 8). Then, the command output means 4 takes into account a delay time (for example, about 150 ms) from when the synchronous input command is sent until the contact of the circuit breaker 3 is closed and the two power systems are actually started in parallel. The time of outputting an early synchronous input command is calculated (step 9), and the synchronous input command is output without missing the timing (step 10).

  For example, when the frequency difference Δf is around 0.6 Hz and the phase difference Δδ passes through the zero point (see FIG. 5), the frequency difference Δf changes from +0.02 Hz to −0.02 Hz, and the phase difference Δδ is zero. It can be seen that the temporal change of the energy function: U can be approximated by a quadratic function in any of the cases where it does not (see FIG. 6).

  When the frequency difference Δf is relatively large as in the former, since the time change of the energy function: U can be obtained largely, the sampling time for obtaining the approximate expression of the quadratic function becomes small, but about 10 ms to 20 ms. A degree of sampling time is sufficient. Further, when the frequency difference Δf is relatively small as in the latter, the temporal change of the energy function: U is small and the sampling time can be increased, but if the sampling time is set to about 10 ms to 20 ms, In any case, an approximate expression of a quadratic function necessary for calculating the estimated time can be obtained.

  In some cases, the function as a synchronous circuit breaker, that is, the frequency detection unit 7 and the phase detection unit 8 are provided, and the synchronous input for actually performing the synchronous parallel of the two power systems in response to the synchronous input command. It is also possible to configure as a synchronous input device provided with means.

  It can be used to reduce power outage time in the recovery of power system accidents.

It is a functional block diagram which shows an example of the synchronous injection | throwing-in apparatus of a power system and a circuit breaker by this invention. It is a flowchart which shows an example of the process in the synchronous parallel method of a power system by this invention, and a synchronous injection | throwing-in apparatus. (A) is a block diagram showing an embodiment example of the synchronous parallel method of the power system according to the present invention, and (B) is an equivalent circuit diagram showing an embodiment example of the synchronous parallel method of the power system according to the present invention. It is explanatory drawing which compared the making allowable range in the synchronous parallel method of the electric power system by this invention, and the conventional making allowable range. (A) is a chart showing the relationship between the frequency difference Δf and the phase difference Δδ in an example in which the phase difference Δδ passes through the zero point, and (B) is an energy function in an example in which the phase difference Δδ passes through the zero point: It is a chart which shows the time change of the value of U. (A) is a chart showing the relationship between the frequency difference Δf and the phase difference Δδ in an example where the phase difference Δδ does not pass through the zero point, and (B) is an energy function in an example where the phase difference Δδ does not pass through the zero point: It is a chart which shows the time change of the value of U. It is explanatory drawing which showed the example of the input tolerance | permissible_range in the conventional synchronous parallel method of an electric power system.

Explanation of symbols

1 current calculation means, 2 current determination means, 3 circuit breaker, 4 command output means,
5 Estimate calculation means, 6 Input calculation means,
7 frequency detector, 8 phase detector,
9 input means,

Claims (4)

In a synchronous parallel method of a power system that synchronously parallelizes a plurality of power systems,
The power supply frequency difference Δf and the phase difference Δδ of the two systems to be synchronously paralleled are detected, and the power supply frequency difference Δf and the phase difference Δδ are used.

Here, M: Unit inertia constant of single system (sec)
Δω: Angular frequency difference between two systems 2πΔf (rad / sec)
X: Impedance of single system (system capacity based pu)
Δδ: Radian value of phase difference between two systems: 2πΔθ (°) / 360 (rad / sec)
A parallel parallel method of a power system that calculates the value of the energy function and outputs a synchronous input command to the circuit breaker (3) on condition that the value of the energy function U is within a preset allowable range.   On the condition that the value of the energy function: U falls within a preset allowable range, three or more samples of the value of the energy function: U are calculated from the power supply frequency difference Δf and the phase difference Δδ of the two systems to be synchronized in parallel. Then, an approximate expression U (t) of a quadratic function indicating a temporal change of the energy function U is derived from the calculated energy function U, and the approximate expression U (t) takes a minimum value. The synchronous parallel method of the electric power system according to claim 1, wherein an estimated time is calculated, and a synchronous input command is output to the circuit breaker (3) at a timing that becomes synchronous parallel at the estimated time. In a power system synchronous input device for synchronously paralleling multiple power systems,
The power supply frequency difference Δf and phase difference Δδ are calculated from the power supply frequency f and phase δ of the two systems that are synchronously paralleled, and the power supply frequency difference Δf and phase difference Δδ are used.

Here, M: Unit inertia constant of single system (sec)
Δω: Angular frequency difference between two systems 2πΔf (rad / sec)
X: Impedance of single system (system capacity based pu)
Δδ: Radian value of phase difference between two systems: 2πΔθ (°) / 360 (rad / sec)
Current state calculating means (1) for calculating the value of the energy function: current state determining means (2) for determining whether or not the value of the energy function U is within a preset allowable range, and the current state determining means (2) By means of the above-mentioned energy function: command output means (4) for outputting a synchronous input command to the circuit breaker (3) on condition that the value of U is within a preset allowable range, the synchronous input device for the electric power system . On the condition that the value of the energy function: U is within a preset allowable range, the power supply frequency difference Δf and the phase difference Δδ of the two systems to be synchronously paralleled are calculated, and the energy function: U for each sample is calculated. The estimation calculation means (5) for calculating the value of each of three samples or more, and the approximate function: U (t) of the quadratic function indicating the temporal change of the energy function: U from the value of each energy function: U At the same time, the on-time calculation means (6) for calculating the estimated time at which the approximate expression: U (t) takes the minimum value, and the synchronous on-command to the circuit breaker (3) at the timing that is synchronously parallel to the estimated time The apparatus for synchronously turning on the electric power system according to claim 3, further comprising the command output means (4) for outputting the power.

Images