CN103051265A - Power generator forced excitation control method under condition of power system faults - Google Patents

Abstract

The invention discloses a power generator forced excitation control method under the condition of power system has faults, and the method comprises the following steps that power generators with large installed capacity and high excitation response are selected from a power system, and forced excitation controllers are arranged to the power generators; and when the working system has faults, all power generators in the system are classified into an S cluster and an A cluster according to the power-angle information of the power generators which is measured in a phase measuring unit in a wide area measuring system, and equivalent power angles of the whole system are calculated. The forced excitation startup/exit moments of all power generator units are determined by integrating the clusters that the power generators are located in according to the change rules of the equivalent power angles. According to the power generator forced excitation control method under the condition of the power system faults, the power generator forced excitation is started/shut up in a gradual swing mode according to the swinging frequency of a transient stable process of the system, so that enough forced excitation control force is applied to key swinging frequency on the one hand and partial power generator forced excitation does not over-brake the follow-up swinging frequency of the system on the other hand, and the role of the power generator forced excitation control in improving the transient stability of the system can be fully displayed.

Description

Generator in a kind of electric power system fault situation is encouraged by force control method

Technical field

The invention belongs to the control technique in power system field, the generator that is specifically related in a kind of electric power system fault situation is encouraged by force control method.

Background technology

The Unified Global that electric power system is linked together and formed by generator, transformer, converter, power circuit and the various power consumption equipments etc. of production, conversion, conveying, distribution, consumption electric energy.After being subject to large disturbance in the electric power system fault situation, each synchronous machine keeps synchronous operation and is transitioned into ability new or that return to original steady operation mode, is called the transient stability of electric power system by the insider.

Generator excitation control is the effective measures that improve power system transient stability; When AC system was short-circuited fault, generator terminal voltage descended, and the electromagnetic power of output reduces, and the mechanical output of input is constant, thereby the rotor acceleration, and generator loses synchronously the system transient modelling unstability when serious.And generator excited system can increase exciting voltage when set end voltage descends, and improves generator terminal voltage, increases the electromagnetic power of generator output, accelerates area thereby reduce rotor, improves power system transient stability.

Yet, the conventional generator excitation system all is take the set end voltage of generator as the control target: when AC system is short-circuited fault, excitation system only occurs in short circuit and brings into play field-forcing function during set end voltage returns to rated value, and usually occur to the first pendulum of system or the most dangerous pendulum finishes during this period of time much smaller than what excitation control can effectively play a role from short circuit during this period of time, thereby excitation system is not fully played the improvement effect of power system transient stability; When direct current system generation locking fault, because the capacitive reactive power of filter and shunt capacitor is superfluous in the DC converter station, AC system voltage will slightly raise, thus generator after fault with first demagnetize, can have a negative impact especially to power system transient stability.

Generator encourage by force control can the transient stability process after system breaks down in, generator was within one specific period always encourages by force state, thereby remedy the defects of conventional excitation control mode, improve the transient response characteristic of excitation system after the fault, give full play to excitation system to the castering action of power system transient stability.Encourage by force unit, by force encourage controlled quentity controlled variable, encourage that to start and withdraw from constantly be the major influence factors of encouraging by force the control effect by force, start and withdraw from and encourage by force control on appropriate opportunity if can not select suitable unit to encourage by force control or fail, encourage by force control and might be unfavorable on the contrary system stability.

The people such as Bayne J P are Static exacter control to improve transient stability (IEEE Trans on Power System at title, 1975, PAS-94 (4): the enable logic that the proposition generator is encouraged by force in document 1141-1146) generally is that the set end voltage bust surpasses a threshold value and the generator speed deviation also surpasses a threshold value; Adopt this when encouraging enable logic by force, on the one hand, only having near the short dot unit energy obviously to experience fault impacts and starts and encourage by force control, less usually can't the startup of the suffered disturbance of far-end unit encouraged by force control, because it is less that the unit of control is encouraged by force in actual participation between age at failure, its to the stability of a system to improve effect comparatively limited; On the other hand, if the dc inversion station is arranged near the short dot, arrange with respect to receiving end electrical network unit merit angle forward at sending end electrical network unit merit angle after the fault, and this encourages by force enable logic and can cause receiving end electrical network unit to be encouraged by force, is unfavorable on the contrary power system transient stability.

It is research (Tsing-Hua University's journal of Discrete Supplementary Excitation Control of Synchronous Generators for Improving Transient Stability at title that Liu such as gets at the people, 1980,20 (3): 43-51) propose in the literary composition after generator the 1st pendulum finishes, to withdraw from by force immediately and encourage, but the finish time that the finish time of certain unit the 1st pendulum and system the 1st put in the system is often different, so from the angle of whole system stability, the method is not optimum to the selection of encouraging by force exit time yet.

Summary of the invention

For the existing above-mentioned technological deficiency of prior art, the generator that the invention provides in a kind of electric power system fault situation is encouraged by force control method, transient stability that can the Effective Raise electric power system.

Generator in a kind of electric power system fault situation is encouraged by force control method, comprises the steps:

(1) determines a strong separately ex-cited generator group of planes in the electric power system, each generator in the strong separately ex-cited generator group of planes is installed encouraged by force controller;

(2) gather the merit angle of each generator in the electric power system, calculate the average merit of the generator angle of system; According to the average merit of the generator of system angle each generator in the system is classified as S cluster or A cluster;

(3) by the generator average merit angle of calculating S cluster and the average merit of the generator angle of A cluster, to determine the equivalent merit angle of system;

(4) according to described equivalent merit angle the generator in the system is encouraged by force, until tend to be steady in described equivalent merit angle.

In the described step (1), determine that the method for the strong separately ex-cited generator group of planes in the electric power system is: make the generator that satisfies simultaneously following two conditions in the electric power system range a strong separately ex-cited generator group of planes;

A. the Generator pool-size is greater than default capacity threshold;

B. generator excited system is high initial response excitation system or static excitation system.

The generator excited system type is that these two kinds of excitation systems of high initial response excitation system or static excitation system all belong to the quick response excitation system with high limited value exciting voltage multiple, the multiple of the highest exciting voltage and rated excitation voltage is not less than 1.8, can reach between the highest exciting voltage and the rated excitation voltage poor 95% in the time being less than or equal to 0.1s, and can inversion produce the negative sense exciting voltage.

In the described step (2), according to the average merit of the generator of following formula computing system angle:

$\stackrel{\‾}{\mathrm{\δ}}=\frac{\underset{k=1}{\overset{K}{\mathrm{\Σ}}}{M}_k{\mathrm{\δ}}_k\left(0\right)}{\underset{k=1}{\overset{K}{\mathrm{\Σ}}}{M}_k}$

Wherein:

Be the average merit of the generator of system angle, M _kBe the moment of inertia of k generator in the system, δ _k(0) be the merit angle of k generator in the initial time system, k is natural number and 1≤k≤K, and K is the generator sum of electric power system.

Described initial time is judged the moment that electric power system is broken down for monitoring.

In the described step (2), the method that each generator in the system is classified as S cluster or A cluster is: make in the electric power system, initial time merit angle ranges the S cluster greater than the generator at the average merit of system's generator angle, and the generator that initial time merit angle is less than or equal to the average merit of system's generator angle ranges the A cluster.

In the described step (3), determine the equivalent merit angle of system according to following formula:

$\mathrm{\δ}\left(t\right)=\stackrel{\‾}{\mathrm{\δS}}\left(t\right)-\stackrel{\‾}{\mathrm{\δA}}\left(t\right)$

$\stackrel{\‾}{\mathrm{\δS}}\left(t\right)=\frac{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{\mathrm{MS}}_i{\mathrm{\δS}}_i\left(t\right)}{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{\mathrm{MS}}_i}$

$\stackrel{\‾}{\mathrm{\δA}}\left(t\right)=\frac{\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{MA}}_j{\mathrm{\δA}}_j\left(t\right)}{\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{MA}}_j}$

Wherein: the equivalent merit angle of etching system when δ (t) is t,

With

Be respectively the average merit of the generator angle of t moment S cluster and A cluster, MS _iBe the moment of inertia of i generator in the S cluster, MA _jBe the moment of inertia of j generator in the A cluster, δ S _i(t) be the merit angle of i generator in the t moment S cluster, δ A _j(t) be the merit angle of j generator in the t moment A cluster, t is the time, and i and j are natural number and 1≤i≤m, and 1≤j≤n, m are the generator number of S cluster, and n is the generator number of A cluster.

In the described step (4), encourage by force strategy by following generator the generator in the system encouraged by force:

If the equivalent merit angle of current time is greater than upper one constantly equivalent merit angle, then apply by force and encourage each generator of encouraging by force controller is installed in the S cluster, generator in the A cluster is withdrawed from by force encourage;

If the equivalent merit angle of current time is less than upper one constantly equivalent merit angle, then apply by force and encourage each generator of encouraging by force controller is installed in the A cluster, generator in the S cluster is withdrawed from by force encourage;

If the equivalent merit angle of current time equals the equivalent merit angle in a moment, then keep the generator of etching system in a period of time and encourage by force strategy.

The present invention encourages by force control method by choosing the generator that installed capacity is large in the electric power system, excitation response is fast, it is installed encourage by force controller; After operating system generation AC system short trouble or DC system locking fault, utilize the generator's power and angle information that phasor measurement unit records in the WAMS, all generators in the system are divided into S cluster and A cluster, calculate the equivalent merit of total system angle.According to the Changing Pattern at equivalent merit angle and in conjunction with generator place cluster (S cluster or A cluster), thereby determine that encouraging by force of each generating set starts/withdraw from constantly.

So the present invention encourages by force control method and can make after the fault in the system all that the generating set of encouraging by force controller is housed all to participate in encouraging by force control, because it is many to participate in encouraging by force the generating set of control, the control dynamics is strong, to the successful that improves of the stability of a system; Inferior according to the pendulum of power system transient stability process simultaneously, starting/withdraw from generator by pendulum encourages by force, can guarantee on the one hand the key pendulum is applied enough control dynamics of encouraging by force, can prevent also on the other hand that the part generator from encouraging by force time produced braking to the follow-up pendulum of system, can give full play to generator and encourage by force the castering action of controlling power system transient stability.

Description of drawings

Fig. 1 is the schematic flow sheet that generator of the present invention is encouraged by force control method.

Fig. 2 is the control sequential chart that generator of the present invention is encouraged by force control method.

Fig. 3 is voe Power Plant power-angle curve figure.

Fig. 4 is voe Power Plant set end voltage curve chart.

Fig. 5 is voe Power Plant exciting voltage curve chart.

Embodiment

In order more specifically to describe the present invention, below in conjunction with the drawings and the specific embodiments generator of the present invention is encouraged by force control method and be elaborated.

Below take southern network system as example, south electric network is mainly economized electrical network by Yunnan, Guizhou, Guangxi, Guangdong, Hai Nanwu and is formed, wherein Hainan Power Grid is because of the geographical position cause, scale is less, and is comparatively independent.The simulation calculation data that adopt in the example, 253 of the total generating sets of Guangdong Power Grid, total installation of generating capacity 121558MVA; 123 of the total generating sets of Guangxi Power Grid, total installation of generating capacity 36468MVA; 803 of the total generating sets of Yunnan Power System, total installation of generating capacity 90000MVA; 170 of the total generating sets of Guizhou Power Grid, total installation of generating capacity 45267MVA.

At first, make the generator that satisfies simultaneously following two conditions in the electric power system range a strong separately ex-cited generator group of planes;

A. the Generator pool-size is greater than default capacity threshold; In the present embodiment, capacity threshold is preset as 300MVA;

B. generator excited system is high initial response excitation system or static excitation system.

In the reality, the generator shown in the table 1 in the power plant all satisfies above-mentioned two conditions, thereby forms a strong separately ex-cited generator group of planes, still the generating set shown in the his-and-hers watches 1 install and encourage by force controller.

Table 1

Below we investigate south electric network 500kV alternating current circuit and three phase short circuit fault and the 0.1s that delays time mistake occur cut the transient stability situation that double-circuit line is removed system after the fault, take the He Prefecture-Luo hole line fault is as example, short trouble occurs in t=1s constantly.

Through 0.1s the time delay, distributed stability control device monitoring and judgement system break down; As shown in Figure 1, the phasor measurement unit in (being initial time) WAMS is sent to Surveillance center with the merit angle of all generators in the south electric network system at this moment, and according to the average merit of the generator of following formula computing system angle:

$\stackrel{\‾}{\mathrm{\δ}}=\frac{\underset{k=1}{\overset{K}{\mathrm{\Σ}}}{M}_k{\mathrm{\δ}}_k\left(0\right)}{\underset{k=1}{\overset{K}{\mathrm{\Σ}}}{M}_k}$

Wherein: Be the average merit of the generator of system angle, M _kBe the moment of inertia of k generator in the system, δ _k(0) be the merit angle of k generator in the initial time system, k is natural number and 1≤k≤K, and K is the generator sum of electric power system.

Calculate the average merit of system's generator angle According to the average merit of system's generator angle each generator in the system is classified as S cluster or A cluster: make in the electric power system, initial time merit angle ranges the S cluster greater than the generator at the average merit of system's generator angle, and the generator that initial time merit angle is less than or equal to the average merit of system's generator angle ranges the A cluster.

Final S cluster unit has 1073 generators, and A cluster unit has 276 generators.According to dividing the result, all units all belong to the S cluster in the table 1.After having divided S cluster and A cluster, WAMS is according to the merit angle of all generators in Surveillance center's transfer system of set sampling period.

According to following formula, by the generator average merit angle of calculating S cluster and the average merit of the generator angle of A cluster, to determine the equivalent merit angle of system;

$\mathrm{\δ}\left(t\right)=\stackrel{\‾}{\mathrm{\δS}}\left(t\right)-\stackrel{\‾}{\mathrm{\δA}}\left(t\right)$

$\stackrel{\‾}{\mathrm{\δS}}\left(t\right)=\frac{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{\mathrm{MS}}_i{\mathrm{\δS}}_i\left(t\right)}{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{\mathrm{MS}}_i}$

$\stackrel{\‾}{\mathrm{\δA}}\left(t\right)=\frac{\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{MA}}_j{\mathrm{\δA}}_j\left(t\right)}{\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{MA}}_j}$

Wherein: the equivalent merit angle of etching system when δ (t) is t,

With

Be respectively the average merit of the generator angle of t moment S cluster and A cluster, MS _iBe the moment of inertia of i generator in the S cluster, MA _jBe the moment of inertia of j generator in the A cluster, δ S _i(t) be the merit angle of i generator in the t moment S cluster, δ A _j(t) be the merit angle of j generator in the t moment A cluster, t is the time, and i and j are natural number and 1≤i≤m, and 1≤j≤n, m are the generator number of S cluster, and n is the generator number of A cluster.

Encourage by force strategy according to equivalent merit angle by following generator the generator in the system is encouraged by force, until equivalent merit angle tends to be steady, as shown in Figure 2;

If the equivalent merit angle of current time is greater than upper one constantly equivalent merit angle, then apply by force and encourage each generator of encouraging by force controller is installed in the S cluster, generator in the A cluster is withdrawed from by force encourage;

If the equivalent merit angle of current time is less than upper one constantly equivalent merit angle, then apply by force and encourage each generator of encouraging by force controller is installed in the A cluster, generator in the S cluster is withdrawed from by force encourage;

If the equivalent merit angle of current time equals the equivalent merit angle in a moment, then keep the generator of etching system in a period of time and encourage by force strategy.

Just in the pendulum process, equivalent merit angle will continue to increase in system, i.e. δ (t+ Δ t)＞δ (t) (Δ t was determined by the sampling period of WAMS).Because all units all belong to the S cluster in the table 1, so all units in the table 1 sent and encouraged by force enabled instruction this moment.

At t=2.5s constantly, system equivalent merit angle reach maximum and then begin to reduce, i.e. δ (t+ Δ t)＜δ (t), system anti-pendulum process begins.Because all units all belong to the S cluster in the table 1, so the time in the table 1 all units send and encourage by force exit instruction.

When system equivalent merit angle has tended to steadily, then no longer in the table 1 generating set send and encourage by force enabled instruction, encourage by force control and finish, system keeps transient stability.

Fig. 3～5 have provided unit merit angle, the set end voltage of Yunnan Power System voe Power Plant, the transient response curve of exciting voltage.Dotted line and solid line are respectively not apply and encourage by force the simulation curve of encouraging by force system in the control situation in the control situation with the employing present embodiment among the figure.

Can find out from Fig. 3～5: when encouraging by force control without wide area, generator excitation voltage will rise to higher level in short-term during the short circuit, but exciting voltage will descend rapidly after fault is eliminated.During the first pendulum of system, action time is encouraged by force only for 0.10s by the DCgenerator motor field system, and is limited to the improvement effect of the stability of a system, and system is the most first pendulum unstability.When having wide area to encourage by force control, because unit is encouraged by force the effect of controller, exciting voltage will rise to rapidly the top value, and generator enters the state of encouraging by force.Generator voltage during this puts remarkable elevator system head, the forward at establishment unit merit angle is dispersed.After the first pendulum of system finished, generator was encouraged by force control and is finished, and exciting voltage descends rapidly, and set end voltage also descends rapidly thereupon.During the first pendulum of system, be 0.96s the action time of encouraging by force of generator excited system, and it is stable that system finally can keep.

Below we investigate the transient stability situation of system after each time of south electric network DC line generation bipolar locking fault.Result of calculation shows: after the wide direct current of cloud, glutinous bundle cross direct current or black East Germany DC bipolar block, fault will cause that a large amount of active power of sending end Yunnan Power System can't send, and finally cause the first pendulum of whole system unstability.

For above-mentioned fault, we select the generating set of 15 crucial power plant of Yunnan Power System to participate in wide area and encourage by force control, and take the following control strategy of encouraging by force: in the first pendulum process of (1) system after fault occurs, what start these units encourages by force control, it is entered rapidly encourage by force state; (2) after the first pendulum of system finishes, withdraw from immediately all units and encourage by force control.Although this has increased the backswing amplitude to a certain extent, but with regard to general effect, because set end voltage is maintained at a higher level (about 1.05p.u.), the voltage support ability of sending end electrical network will get a promotion, thereby a large amount of active power of sending end electrical network can successfully be sent by the stream passway for transmitting electricity that respectively backcrosses after having guaranteed high-capacity direct current bipolar locking fault.

Claims (7)

1. the generator in the electric power system fault situation is encouraged by force control method, comprises the steps:

(1) determines a strong separately ex-cited generator group of planes in the electric power system, each generator in the strong separately ex-cited generator group of planes is installed encouraged by force controller;

(2) gather the merit angle of each generator in the electric power system, calculate the average merit of the generator angle of system; According to the average merit of the generator of system angle each generator in the system is classified as S cluster or A cluster;

(3) by the generator average merit angle of calculating S cluster and the average merit of the generator angle of A cluster, to determine the equivalent merit angle of system;

(4) according to described equivalent merit angle the generator in the system is encouraged by force, until tend to be steady in described equivalent merit angle.

2. generator according to claim 1 is encouraged by force control method, it is characterized in that: in the described step (1), determine that the method for the strong separately ex-cited generator group of planes in the electric power system is: make the generator that satisfies simultaneously following two conditions in the electric power system range a strong separately ex-cited generator group of planes:

A. the Generator pool-size is greater than default capacity threshold;

B. generator excited system is high initial response excitation system or static excitation system.

3. generator according to claim 2 is encouraged by force control method, it is characterized in that: described capacity threshold is 300MVA.

4. generator according to claim 1 is encouraged by force control method, it is characterized in that: in the described step (2), according to the average merit of the generator of following formula computing system angle:

$\stackrel{\‾}{\mathrm{\δ}}=\frac{\underset{k=1}{\overset{K}{\mathrm{\Σ}}}{M}_k{\mathrm{\δ}}_k\left(0\right)}{\underset{k=1}{\overset{K}{\mathrm{\Σ}}}{M}_k}$

Wherein:

Be the average merit of the generator of system angle, M _kBe the moment of inertia of k generator in the system, δ _k(0) be the merit angle of k generator in the initial time system, k is natural number and 1≤k≤K, and K is the generator sum of electric power system.

5. generator according to claim 1 is encouraged by force control method, it is characterized in that: in the described step (2), the method that each generator in the system is classified as S cluster or A cluster is: make in the electric power system, initial time merit angle ranges the S cluster greater than the generator at the average merit of system's generator angle, and the generator that initial time merit angle is less than or equal to the average merit of system's generator angle ranges the A cluster.

6. generator according to claim 1 is encouraged by force control method, it is characterized in that: in the described step (3), determine the equivalent merit angle of system according to following formula:

$\mathrm{\δ}\left(t\right)=\stackrel{\‾}{\mathrm{\δS}}\left(t\right)-\stackrel{\‾}{\mathrm{\δA}}\left(t\right)$

$\stackrel{\‾}{\mathrm{\δS}}\left(t\right)=\frac{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{\mathrm{MS}}_i{\mathrm{\δS}}_i\left(t\right)}{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{\mathrm{MS}}_i}$

$\stackrel{\‾}{\mathrm{\δA}}\left(t\right)=\frac{\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{MA}}_j{\mathrm{\δA}}_j\left(t\right)}{\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{MA}}_j}$

Wherein: the equivalent merit angle of etching system when δ (t) is t,

With

Be respectively the average merit of the generator angle of t moment S cluster and A cluster, MS _iBe the moment of inertia of i generator in the S cluster, MA _jBe the moment of inertia of j generator in the A cluster, δ S _i(t) be the merit angle of i generator in the t moment S cluster, δ A _j(t) be the merit angle of j generator in the t moment A cluster, t is the time, and i and j are natural number and 1≤i≤m, and 1≤j≤n, m are the generator number of S cluster, and n is the generator number of A cluster.

7. generator according to claim 1 is encouraged by force control method, it is characterized in that: in the described step (4), encourage by force strategy by following generator the generator in the system is encouraged by force:

If the equivalent merit angle of current time is greater than upper one constantly equivalent merit angle, then apply by force and encourage each generator of encouraging by force controller is installed in the S cluster, generator in the A cluster is withdrawed from by force encourage;

If the equivalent merit angle of current time is less than upper one constantly equivalent merit angle, then apply by force and encourage each generator of encouraging by force controller is installed in the A cluster, generator in the S cluster is withdrawed from by force encourage;

If the equivalent merit angle of current time equals the equivalent merit angle in a moment, then keep the generator of etching system in a period of time and encourage by force strategy.

Images