JPH0734626B2 - Online stabilization control method for power supply system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is that a power system including a plurality of generators and a load is transiently unstable with respect to a main system due to a power line accident or the like. The present invention relates to an on-line stabilization control method of a power supply system that prevents the above.

[Conventional technology]

In recent years, in the power system, the stability of the power system at the time of a large disturbance tends to decrease with the increase in the capacity of the power source and the remote centralization. If a large-capacity power generator group goes out of order and is disconnected from the main system, it is expected that there will be a major problem in terms of supply. Therefore, various stabilization measures have been developed,
Has been applied.

Fig. 5 shows the conventional power supply system shown in, for example, PE-88-98, Power Engineering Research Conference of the Institute of Electrical Engineers of Japan, 1988, Suzuki, Yanagibashi, et al. Is a basic system model diagram for explaining the online stabilization control method of 1 is an equivalent generator in which the generators that are operating in the target power supply system are equivalently integrated into one by the parallel impedance method, and 2 is the target power supply system Virtual infinity bus that equivalently represents the main system that is supplied with power from
3 is a node admittance matrix, which shows the electrical coupling between the equivalent generator 1 and the virtual infinite bus 2 after the accident is cleared.
It is represented by a node admittance matrix of 2.

Next, the operation will be described. First, in Fig. 5, assuming that the load in the target power system is extremely small,
By ignoring the equivalent generator side self-conductance component G ₁₁ and the transfer conductance component G ₁₂ of the admittance matrix 3, the active power Pe of the equivalent generator 1 can be approximated by the following equation.

However, Eg: magnitude of internal voltage of equivalent generator 1 δ: transfer angle of internal voltage of equivalent generator 1 E ₀ : magnitude of voltage of virtual infinite bus 2 B ₁₂ : transfer susceptance of node admittance matrix 3 Here, assuming that the internal voltage of the equivalent generator 1 (internal reactance back voltage) is constant and the frequency deviation of the virtual infinite bus 2 is always zero, and the transfer susceptance component B ₁₂ is constant regardless of time, ( P (= EgE ₀ B ₁₂ ) in the equation 1) is a constant independent of time and is given by the following equation.

However, Pe: Active power output of equivalent generator 1 (total value of target generator group) Δω: Angular frequency deviation of equivalent generator 1 M: Inertia constant of equivalent generator 1 (total value of target generator group) Pm: Mechanical input of equivalent generator 1 (that is, active power output just before the accident of equivalent generator (total value of target generator group) ) Ωo: Reference angular frequency (rad / s) Moreover, Pe, M, and Pm are all Pu amounts (unit method expression) based on the same system reference capacity.

All the left and right components of the equation (2) can be calculated from the active power output Pe of the equivalent generator 1. On the other hand, the constant P given by the equation (1) corresponds to the peak value of the power phase difference angle curve expressed as a pure sin curve. Therefore, if the constant P is calculated from the equation (2) using the online data of the active power Pe of the equivalent generator 1 after clearing the accident, the power phase difference curve adapted to the accident condition or the grid condition can be obtained. .

When the power phase difference angle curve is obtained, the stability and the necessary stabilization control amount can be predicted in advance by the energy method (equal area method) as described below.

After the accident is cleared, the initial internal voltage Eg of the equivalent generator is calculated as the average value of the constant p calculated at each sampling point for several tens of ms.
The product of (0) and Pcor ^* is used as the estimated value of the constant P. Assuming that the stabilization control assumed completion time is tsh starting from the time of the accident occurrence, the online calculated values of the kinetic energy Vk at the stabilization control (generator shutdown) assumed completion time tsh and the critical energy Vc after the stabilization control assumed completion time are It is given by

Vk (ωoM / 2) {Δω (tsh) / ωo} ² …… (4) Note that the time integration for obtaining Δω (tsh) in the equation (4) is numerically executed by using trapezoidal approximation or the like. When P ^* <Pm, the critical energy Vc is set to 0 and it is judged to be unstable without stabilizing control.

The kinetic energy Vk and the critical energy Vc calculated online from the equations (4) and (5) are used to perform stability determination by the following equation.

When it is determined that the equation (6) is unstable, the stabilizing control amount (generator cutoff amount) can be determined using the online estimated value Pcor ^* of the constant P as follows.

The system of FIG. 5 is further modeled as shown in FIG. Sixth
In the figure, Xg is the sum of the trans-reactance xt looking from the bus N to the equivalent generator side and the generator internal reactance (direct-axis transient reactance) xd ″, and xs ^* is the short-circuit reactance looking from the bus N to the main system side. Can be calculated by the following equation (7), and these quantities are also pu values based on the system reference capacity.

The value of Xg can be grasped as online data in advance from the parallel state of the generator before the accident. xs ^* is an on-line estimate Pcor ^* constants P, also the size Eg of the initial internal voltage equivalent generator (0), by assuming that 1.0pu magnitude E ₀ of the infinite bus voltage, the following It can be calculated from the formula.

xs ^* = Eg (0) / Pcor ^* -xg (7) Now, in FIG. 6, a part of the target generator group constituting the equivalent generator 1 is cut off, and the inertia constant of the equivalent generator 1 is Mb. , The mechanical input changes to Pmb, and the generator reactance changes to Xgb. Further, assuming that Eg (0), xs ^* does not change due to interruption, the peak value Pcorb ^* of the power phase difference angle curve after the assumed interruption is given by the following equation.

From the above, the re-evaluation values Vkb and Vcb of the kinetic energy and critical energy in the assumed cutoff implementation can be calculated by the following equation.

Vkb = (ωoMb / 2) {Δω (tsh)} ² …… (9) Vkb and Vcb are calculated in order from the control pattern with the smaller interruption amount using Eqs. (9) and (10), and the minimum generator interruption amount that satisfies Vkb <Vcb ... (11) is stabilized control amount. Is determined as the online calculated value of, and the cutoff is performed for that amount.

[Problems to be Solved by the Invention]

Since the conventional on-line stabilization control method of the power supply system is performed as described above, it is possible to ignore the conductance component of the node admittance matrix element assuming that the load in the target power supply system is extremely small. Since the power phase difference angle curve that is the basis for online calculation of the critical energy Vc is regarded as a pure sin curve, the load in the target power system is large and the power phase difference angle curve is pure.
If it cannot be expressed by a sin curve, there is a problem that the error of the calculated stabilizing control amount becomes large.

The present invention has been made in order to solve the above problems, and is capable of accurately performing on-line accurate stabilization control necessary for maintaining transient stability, regardless of the size of the load in the target power system. The purpose is to obtain an online stabilization control method of.

[Means for Solving the Problems]

The on-line stabilization control method of the power supply system according to the present invention is the equivalent generator side self-conductance component G ₁₁ of the node admittance matrix element and the magnitude E of the equivalent generator internal voltage.
Let the product Eg ² G ₁₁ with the square of g be P ₁ (first operation value), and transfer susceptance component of the node admittance matrix element
The product EgE ₀ E ₁₂ of B ₁₂ and the size of the equivalent generator internal voltage Eg of the virtual layer infinity bus voltage E ₀ is P ₂ (second calculated value)
Then, the values of P ₁ and P ₂ are estimated using the online data of the generator output for several tens of msec after the accident is cleared, and the first and second estimated values P ₁ ^* and P ₂ ^* are ^calculated . The energy method is applied to the base to determine the stability determination and the stabilization control, and when the result of the stability determination is unstable, the generator for the stabilization control amount is selected from the target generators. It is the one.

[Work]

The first and second estimated values P ₁ ^* , P in the present invention
₂ ^* is estimated using online data of generator active power and reactive power output for an extremely short time immediately after clearing the accident, and the influence of electric charge is greatly reflected in the propulsion value P ₁ ^*. By expressing the angle curve as Pe = P ₁ ^* + P ₂ ^* sin δ, the critical energy, which is the stability determination threshold value, is adapted to the system condition and the accident condition regardless of the load in the target power system The calculation can be performed, and highly accurate stabilization control can be performed.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. First, the basic principle of the present invention will be described with reference to FIG. In the figure, the node admittance matrix 3
The elements that make up are the equivalent positive-phase impedance of the transmission line (mainly the power line that sends power from the target power system to the main system) after the accident is cleared, the short-circuit impedance when the main system side is viewed from the target power system, and the inside of the target power system. The load (constant impedance expression) and so on are collectively shown. In the system model of the figure, the active power output Pe and the reactive power output Qe of the equivalent generator 1 are given by the following equations, respectively.

Pe ＝ Eg ² G ₁₁ ＋ EgE ₀ B ₁₂ sin δ ＋ EgE ₀ B ₁₂ cos δ …… （12） Qe ＝ －Eg ² G ₁₁ −EgE ₀ B ₁₂ cos δ ＋ EgE ₀ B ₁₂ sinδ …… （13） In the above equation, Eg is the equivalent generator. The magnitude of the internal voltage of 1, δ
Is the phase angle of this internal voltage (referenced to the virtual infinite bus voltage phase), E ₀ is the magnitude of the voltage on the virtual infinite bus 2, G ₁₁ is the equivalent generator-side self-conductance of the node admittance matrix 3, and B ₁₁ Is also self-susceptance, G ₁₂ is also transfer conductance, and B ₁₂ is transfer susceptance. The unit of each of these quantities is pu for δ based on the same system reference capacity with rad and all others.
And In addition, M, Pm, Pe, Qe are also based on the same system reference capacity.
pu amount (however, the unit of M is sec). Also, M, Pm, Pe, Q
e is the total value of the target generator group, and Eg is the capacity-weighted average value of the target generator group.

Here, because of the nature of the online stabilization control, it is necessary to simplify the control logic as much as possible, so the following assumptions are made.

The generator internal voltage (internal reactance back voltage) is expressed as a constant model. As the internal reactance, the direct axial transient reactance xd ″ is adopted.

 Virtual infinite bus voltage is always fixed at 1.0∠0 °.

The frequency deviation of the virtual infinite bus voltage is always fixed at 0Hz.

Node admittance matrix elements are constant regardless of time.

The transfer conductance component G ₁₂ is ignored. Also, (1
In equations (2) and (13), (Here, P _{1 is referred} to as a first operation value and P _{2 is referred} to as a second operation value). From the assumptions and Eq. (14), (1
Equations 2) and (13) can be rewritten as follows.

Pe = P ₁ + P ₂ sin δ (15) Qe = P ₃ -P ₂ cos δ (16) Based on the assumption ,,, If the periphery of Eqs. (15) and (16) is differentiated with respect to time t, dPe / dt = P ₂ cos δ ・ d δ / dt = P ₂ cos δ ・ Δω ・ ・ ・ (17) dQe / dt = P ₂ sin δ ・ d δ / dt = P ₂ sin δ ・ Δω ・ ・ ・ (18) Equations (15), (18) By eliminating P ₂ sin δ, the following equation is obtained.

P ₁ = Pe− (1 / Δω) ・ (dQe / dt) (19) Also, if both sides of equations (17) and (18) are squared and the sides are added, In the right-hand side of Eqs. (19) and (20), the terms related to Pe are all quantities measurable at the generator terminals. Also for Δω, assuming that Pm is constant, If the integration on the right side is performed numerically using the trapezoidal approximation etc. at every sampling time point of Pe, it is possible to grasp online (the time point of the accident is taken as the time reference Os). Strictly speaking, Qe is the reactive power output inside the generator, but since the rate of change is used instead of the value itself, it is assumed that dQe / dt is almost equal inside and at the terminal. The rates of change dPe / dt and dQe / dt can be calculated from the first-order differential equation by approximating the changes with a quadratic equation from three-point sampling data of Pe and Qe, for example.

From the above, both P ₁ and P ₂ can be calculated from the amounts measurable at the generator terminals. For example, after the accident is cleared, the average value of P ₁ and P ₂ during the sampling period calculated from Eqs. (19) and (20) at each sampling time for several tens of ms is the online estimated value, which is P ₁ ^* , P ₂ ^* . By substituting these values into equation (15), the power phase difference angle curve adapted to the system state after the accident is cleared can be obtained as Pe = P ₁ ^* , P ₂ ^* sinδ (22) .

After clearing the accident, the kinetic energy Vk is set so that Pe can respond to severe accidents where it has not returned to its initial level Pm.
The time of calculation of is the estimated completion time tsh for judgment control (partial cutoff of the target generator). This Vk is Can be calculated online at. On the other hand, the critical energy Vc corresponding to this Vk can be calculated online using the following equation using the estimated power phase difference curve of equation (22) (see FIG. 1).

The estimated stabilization completion time ts from the accident clear time tf
If the delay time up to h becomes long, the required control amount may increase. In such a case, the data sampling is terminated at an appropriate time tdse (tf <tdse <tsh), and the change in Pe from tsh to tsh is approximated by a quadratic equation by the least squares method, and the equation (23) is used. Δω (tsh) and Pe (t in Equation (24)
For sh), the value predicted from this approximation formula may be used.

Using Vk and Vc calculated online from equations (23) and (24), stability determination is performed as in the following equation (when P ₁ ^* + P ₂ ^* <Pm, Vc = 0).

When it is determined that the system is unstable according to this equation (25), based on the online estimated values P ₁ ^* , P ₂ ^* and the idea of the energy method, the stabilization control amount (one of the target generator group Determine the cut-off amount).

It is assumed that the basic system model of FIG. 5 is equivalent to the system model of FIG. In FIG. 2, g _L is the ground conductance of the bus N, Xs is the reactance from the bus N to the virtual infinite bus 2, Xg is the reactance seen from the bus N toward the equivalent generator 1, and the internal reactance of the equivalent generator 1 is shown. It is given by the sum of Xd ″ and the step-up transformer reactance Xt (both are pu amounts based on the system reference capacity).

If the systems of FIG. 5 and FIG. 2 are equivalent, G ₁₁ = g _L Xs ² / {(g _L XgXs) ² + (Xg + Xs) ² } (26) B ₁₂ = (Xg + Xs) / { (G _L XgXs) ² + (Xg + Xs) ² } (27) holds. On the other hand, from the above assumptions, and Eq. (14), G
₁₁ and B ₁₂ can be obtained by G ₁₁ = P ₁ ^* / Eg ² , B ₁₂ = P ₂ ^* / Eg (28). Let Eg be the initial state, that is, the magnitude of the internal voltage of the equivalent generator immediately before the accident, and grasp it as online data in advance from the following formula.

From equations (26) and (27), If defined as, the following formula is derived.

^{Xs 3 + (Xg-1 /} B 12) Xs 2 + k 2 Xg 2 X S + k 2 Xg 3 = 0 ...... (31) g L = k (Xg 2 + Xs) / X S 2 ...... (32) Xg, Since B ₁₂ and k are known constants, equation (31) becomes a cubic equation regarding the reactance Xs. This is algebraically solved using the Cardano method and the most appropriate root is adopted as the online calculated value of Xs. If the value of reactance Xs is determined, the value of g _L can also be calculated from equation (32). These values of Xs, g _L shall not change due to partial interruption of the target generator.

In the system model of FIG. 2, assuming that the target generator is partially cut off, M of the equivalent generator 1 is Mb, Pm is Pmb, and Xg is Xg.
Suppose it changes to gb. Assuming that Eg does not change due to interruption, P ₁ ^* and P ₂ ^* after assuming interruption are
It is given as follows by referring to the equations (26) to (28).

P ₁ b ^* = Eg ² g _L Xs ² / {(g _L XgbXs) ² + (Xgb + Xs) ² } (33) P ₂ b ^* = Eg (Xgb + Xs) / {(g _L XgbXs) ² + (Xgb + Xs ) ^2} (34) power phase angle curve after assuming blocking than those obtained with ^{_{Peb = P 1 b * + P}} 2 b * sinδ ...... (35). From the above Mb, Pmb, and equation (35), the kinetic energy Vkb and the critical energy Vcb after the cutoff assumption can be calculated as follows.

Vk = (ωoMb / 2) {Δω (tsh) / ωo} ² …… (36) Using equations (33) to (37), Vkb and Vcb are calculated in order from the smallest interruption pattern, and the smallest generator interruption amount that satisfies Vkb <Vcb ... (38) is defined as the stabilization control amount. Determine and cut off the generator for that amount from the target generator group.

Next, an embodiment of the power supply system stabilizing device based on the above-described online stabilization control method of the power supply system and its operation will be described with reference to FIG.

In the figure, 1A to 1N are operating generator groups constituting a power supply system to be controlled, 4A to 4N are step-up transformers of operating generator groups 1A to 1N, and 5A to 5N are low voltage side busbars of generator groups 1A to 1N. , 51 is a substation bus in the power system, 6A and 6B are power lines that transmit the power of the operating generator groups 1A to 1N to the main system side, and 52A is the low-voltage side of the substation that is the connection point between the power system and the main system. Busbar, 41 is the main transformer of the substation, 52B is high voltage side busbar of the substation, 6
1A, 61B, 62A, 62B are main transmission lines in the main system, 7A-7N are step-up transformers 4A-4N circuit breakers, 8 is a power system stabilizer, 81
A to 81N are sensors for measuring the electrical output of the operating generator groups 1A to 1N, 82A to 82N are control cables for inputting the measured electrical output data to the power system stabilizer 8, 83A ~ 83N is a control cable for outputting a trip signal from the power system stabilizer 8 to the circuit breakers 7A ~ 7N, 84A ~ 84N is a sensor for measuring the voltage of the bus bar 5A ~ 5N, 85A ~ 85N is this A control cable for inputting voltage data to the power system stabilizer 8,
Reference numeral 86 is a sensor for measuring the voltage of the substation bus 51, 87 is a control cable for inputting the voltage data of the sensor 86 to the power system stabilizer 8, and 9 is a load in the target power system.

Next, the operation of this device will be described. Driving generator group 1A ~
1N active power output, reactive power and terminal voltage data are
Always measured by sensors 81A-81N, 84A-84N, control cable 82A-8 at a sampling interval of 3-5ms.
It is input to the power system stabilizer 8 via 2N, 85A to 85N. The power supply system stabilizer 8 always uses these data, and uses the mechanical input pm of the equivalent generator, the inertia constant M, the internal reactance Xd ″, the transformer reactance X _T and (2
Calculate and grasp the magnitude Eg of the internal voltage calculated from Eq. 9 as online data in advance.

For example, when a ground fault occurs in the power supply lines 6A and 6B, the active power output data or the voltage data is changed (decreased) by a certain value or more as a kick, and the power system stabilizer 8 enters the start state. , Stabilization processing is performed according to the flowchart shown in FIG.

That is, in FIG. 4, step ST1 is a device activation block by the accident generating device, step ST2 is a time reset processing block for setting the time of the accident occurrence as a time reference, and step ST3 is the operation electric power generation group 1A- 1N
Using the active and reactive power output online data of
From equations (19) to (21), P ₁ and P ₂ at each sampling time point
Step ST4 is a processing block for calculating whether or not the time is the stability determination execution, stabilization control amount determination time t ₁ , and P in step ST3 until this condition is satisfied.
The operations of ₁ and P ₂ are repeated, and the results are all stored in memory. The t ₁ is set to be about after the accident clear 60~70msec. When the time reaches t ₁ , the average value is obtained from the values of P ₁ and P ₂ stored in the memory, and the process proceeds to processing block step ST5 where P ₁ ^* and P ₂ ^* are obtained. Step ST6 uses these P ₁ ^* , P ₂ ^* and the generator active power output data Pe (t) sampled during the accident and stored in the memory to calculate the kinetic energy from equations (23) and (24). Vk, a processing block for calculating the critical energy Vc, step ST7 is a determination block that performs stability determination using the values of Vk and Vc calculated in step ST6, and if it is determined to be stable when Vk <Vc, it is stable. Monitoring and correction control processing routine step ST10
Proceed to.

When it is determined that Vk ≧ Vc is unstable, the process proceeds to the processing block step ST8 for determining the stabilization control amount, and (26) to (38)
The optimum generator cutoff amount required for stabilization is calculated from the formula, and the control target generator for that amount is stored. Time shifts in the processing block step ST9 when it becomes a stabilizing control signal output time t _2, the output a trip signal to the controlled object generator. In addition, t ₂ is set to be about after the accident clear 80~90ms. Phenol-safe elements such as voltage or frequency obtained from the voltage data of the busbar 51 measured by the sensor 86 and input to the stopper relay in the power system stabilizer 8 via the control cable 87 are When the set accident detection condition is satisfied, the trip signal is sent to the above-mentioned controlled generator by the control cables 83A to 8A.
Reach the appropriate one of the circuit breakers 7A-7N via 3N,
Stabilization control is completed.

After that, the processing routine step ST for stability monitoring and correction control using appropriate parameters and methods such as frequency and phase angle
After entering 10 and confirming that the transient stability of the target power system is maintained, proceed to the device stop block step ST11,
The process ends.

In addition, although an example of application to a single power supply system has been shown in the above-mentioned embodiment, even for a wide area power supply system composed of a plurality of power plants, devices equivalent to those in the above-mentioned embodiments are arranged at each power plant. By exchanging information between the respective devices, it is possible to determine the unstable mode and determine the stabilizing control amount corresponding to the mode. The method is applicable not only to the power system but also to the pumping system at night.

〔The invention's effect〕

As described above, according to the present invention, by using only the measurable amount at the operating generator terminal, the generator cutoff amount necessary for maintaining the transient stability of the target power supply system is taken into consideration while considering the influence of the load. Since it can be calculated automatically, there is an effect that the highly accurate stabilization control adapted to the accident condition or the system condition can be executed regardless of the load in the target power system.

[Brief description of drawings]

FIG. 1 is an energy function conceptual diagram for explaining the concepts of kinetic energy and critical energy on a power phase difference angle curve. FIG. 2 is a system model diagram equivalent to FIG. 5 for determining a stabilizing control amount. FIG. 4 is a block diagram of a power system stabilizing device according to an embodiment of the present invention, FIG. 4 is a processing flowchart of stabilization control in the stabilizing device of FIG. 3, and FIG. FIG. 6 is a system model diagram for explaining the basic principle of the control method, and FIG. 6 is a system model diagram for determining the stabilized control amount in the conventional method. 1, 1A to 1N are generators, 2 is an infinite bus, 3 is a node admittance matrix, and 8 is a power system stabilizer. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Tomizawa 1-3-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Within Tokyo Electric Power Co., Inc. No. 2 Mitsubishi Electric Co., Ltd. Control Factory (72) Inventor Tadahiro Goda 1-2 1-2 Wadazakicho, Hyogo-ku, Kobe, Hyogo Prefecture Mitsubishi Electric Co., Ltd. Control Factory

Claims (1)

[Claims] 1. A basic system in which generators operating in a power supply system are aggregated as one equivalent generator, and the equivalent generator and the virtual infinity bus are connected via the node admittance matrix elements of the equivalent generator. In the online stabilization control method for the power system that prevents the system model from becoming excessively unstable, confirming the recovery from the accident that occurred in the power system, the active power and the accident before and after the accident in the equivalent generator were confirmed. Based on the generated reactive power, a first calculated value corresponding to the product of the equivalent generator-side self-conductance of the node admittance matrix element and the square value of the internal voltage of the equivalent generator is calculated. It is calculated and corresponds to the product of the transfer susceptance of the node admittance matrix element, the internal voltage of the equivalent generator and the virtual infinite bus voltage. While calculating the calculated value of 2, the kinetic energy at the estimated completion time of the generator cutoff is calculated based on the active power before and after the accident in the equivalent generator, and based on the first and second calculated values. The critical energy corresponding to the kinetic energy is calculated, and when the kinetic energy is larger than the critical energy, the first and second calculated values, and the above-mentioned calculated value, assuming a partial cutoff of the generator that is operating appropriately. The kinetic energy and the critical energy are calculated, and the smallest generator cutoff amount is determined based on the first and second calculated values within a range where the kinetic energy does not become larger than the critical energy. An online stabilization control method for a power supply system, which selectively shuts off a generator corresponding to the amount of shutoff of the generator.