A method and system for tuning the droop coefficient in conjunction with AVC substations

Abstract

This invention relates to a method for coordinating the droop coefficient with an AVC substation. The method includes the following steps: Step 1: Determine whether the droop coefficient of the power grid unit meets the requirements of the standard or dispatching department. If not, proceed to Step 2; if yes, proceed to Step 4. Step 2: Optimize the droop coefficient setting according to relevant standards or dispatching department requirements to reduce the total droop of a generating unit, thereby improving the unit's sensitivity to grid voltage response. Step 3: Determine whether the droop coefficient meets the requirements of the standard or dispatching department. If not, return to Step 2; if yes, proceed to Step 4. Step 4: Conduct an AVC substation commissioning test. Under the condition of meeting the AVC limiting function test objectives, adjust the adjustment pulse width of the AVC substation. Step 5: Determine whether the AVC substation control accuracy and rate are met. If yes, the setting is completed; otherwise, return to Step 4. Compared with the prior art, this invention has advantages such as improving the AVC substation regulation success rate.

Description

Technical Field

[0001] This invention relates to the field of AVC substation commissioning technology, and in particular to a method and system for adjusting the droop coefficient in conjunction with the AVC substation. Background Technology

[0002] like Figure 1 As shown, the generator excitation system droop coefficient is defined as the slope relationship of the curve of the generator terminal voltage changing with the generator reactive power. According to the slope characteristics of the curve, it can be divided into positive droop, negative droop, and zero droop. The droop coefficient when the voltage decreases with the increase of reactive load is positive, called positive droop; conversely, the droop coefficient when the voltage increases with the increase of reactive load is negative, called negative droop.

[0003] There are problems with the coordination and setting of droop adjustment technology and AVC (Automatic Voltage Control) commissioning: At present, the Shanghai power plant has completed the commissioning of the AVC system. By increasing and decreasing the magnetic pulse operation, a closed-loop control is established between the AVC and the excitation system. When the negative droop adjustment technology is used on the unit that has completed the commissioning of the AVC system, it will change the adjustment pulse width of the excitation system. The step size of AVC adjustment may increase with the increase of the negative droop adjustment coefficient. In severe cases, it may exceed the dead zone of AVC, resulting in AVC adjustment failure.

[0004] Current AVC commissioning tests or droop coefficient settings do not consider the coordination or mutual influence between the droop coefficient and the AVC. Inappropriate droop coefficient settings or improper AVC adjustment pulse width settings can lead to two possible scenarios: the AVC substation cannot correctly execute the AVC master station's adjustment commands, resulting in AVC adjustment failure; or the individual adjustment pulse width of the AVC substation increases, leading to a decrease in the AVC substation's adjustment accuracy. Therefore, it is necessary to coordinate the unit's droop coefficient and the AVC substation settings to meet the control accuracy and rate requirements of the AVC substation and ensure successful AVC substation adjustment. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art by providing a method and system for adjusting the droop coefficient in conjunction with the AVC substation.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for coordinating the adjustment coefficient with AVC substations, comprising the following steps:

[0008] Step 1: Determine whether the droop coefficient of the power grid unit meets the standard or the requirements of the dispatching department. If not, proceed to Step 2; if yes, proceed to Step 4.

[0009] Step 2: the optimization setting of the regulation coefficient is carried out, and the setting is carried out according to the related standard or the requirement of the dispatching department, the total regulation of a power generation unit is reduced to improve the sensitivity of the unit to the voltage response of the power grid;

[0010] Step 3: whether the regulation coefficient meets the standard or the requirement of the dispatching department is judged, if not, return to step 2, if yes, execute step 4;

[0011] Step 4: the AVC substation debugging test is carried out, and the regulation pulse width of the AVC substation is set under the target of meeting the AVC limiting function test;

[0012] Step 5: whether the AVC substation control precision and rate meet the requirement is judged, if yes, the setting is completed, if not, return to step 4.

[0013] The setting mode of the power grid unit is specifically:

[0014] The power grid unit is set in a unit connection mode, that is, a generator and a corresponding main transformer are taken as a power generation unit, a plurality of generators are connected in parallel on the high-voltage side of the main transformer, and the power grid unit adopts negative regulation, the total regulation of a power generation unit is reduced to improve the sensitivity of the unit to the voltage response of the power grid, and at the same time, the total regulation of a power generation unit is kept as positive regulation to ensure the parallel operation between a plurality of power generation units of the power plant.

[0015] The regulation coefficient is used to represent the slope of the voltage regulation characteristic curve of the generator, that is, the rate of change of the generator terminal voltage when the power factor is equal to 0 and the reactive current changes from 0 to the rated value.

[0016] The expression of the voltage regulation characteristic of the generator is:

[0017] U G =f(I Q )

[0018] Wherein, I Q is the reactive current, and U G is the generator voltage.

[0019] The regulation coefficient is divided into positive regulation and negative regulation, the regulation coefficient of the voltage decreasing with the increase of the reactive load is positive, which is called positive regulation, otherwise, the regulation coefficient of the voltage increasing with the increase of the reactive load is negative, which is called negative regulation.

[0020] The step 4 is to set the adjustment pulse width of the AVC substation according to the adjustment coefficient, the set dead zone range and the adjustment precision, and the AVC substation adjustment test includes multiple AVC adjustment tests considering the influence of the adjustment coefficient, namely, the AVC limiting function tests, which are the bus voltage over upper limit test, the bus voltage over lower limit test, the unit reactive power over upper limit test and the unit reactive power over lower limit test.

[0021] The bus voltage over upper limit test is specifically:

[0022] When the bus voltage is 232.2 kV and the voltage upper limit value of the bus voltage is set to be lower than the bus voltage, i.e. 230 kV, at this time, the bus voltage over high lockout is displayed on the central control unit, the AVC execution unit is magnetically locked, and no magnetic pulse output and demagnetization pulse output are outputted.

[0023] The bus voltage over lower limit test is specifically:

[0024] When the bus voltage is 232.2 kV and the voltage upper limit value of the bus voltage is set to be lower than the bus voltage, i.e. 234 kV, at this time, the bus voltage over low lockout is displayed on the central control unit, the AVC execution unit is demagnetized, and no magnetic pulse output and demagnetization pulse output are outputted.

[0025] The unit reactive power over upper limit test is specifically:

[0026] When the unit reactive power is set to be 32 Mvar and the actual reactive power upper limit value is 30 Mvar, at this time, the unit reactive power over high lockout is displayed on the central control unit, the AVC execution unit is magnetically locked, and no magnetic pulse output and demagnetization pulse output are outputted.

[0027] The unit reactive power over lower limit test is specifically:

[0028] When the unit reactive power is set to be -2 Mvar and the actual reactive power upper limit value is 0 Mvar, at this time, the unit reactive power over low lockout is displayed on the central control unit, the AVC execution unit is demagnetized, and no magnetic pulse output and demagnetization pulse output are outputted.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] The unit adjustment coefficient and the AVC substation are cooperatively set in the present application, the control precision and rate of the AVC substation are satisfied, the AVC substation adjustment is ensured to be successful, and the success rate of the AVC substation adjustment is improved. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is the adjustment characteristic curve diagram of the present application.

[0032] Figure 2 It is the structure schematic diagram of the single-machine infinite system considering excitation of the present application.

[0033] Figure 3 Fig. 2 is a diagram showing the reactive power variation of unit 1 before and after the adjustment of the regulation difference according to an embodiment of the present application.

[0034] Figure 4 Fig. 3 is a diagram showing the reactive power variation of unit 2 before and after the adjustment of the regulation difference according to an embodiment of the present application.

[0035] Figure 5 Fig. 4 is a flow chart of the method according to an embodiment of the present application. DETAILED DESCRIPTION

[0036] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments are implemented on the basis of the technical solutions of the present application, and detailed implementation manners and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0037] Generally, a link for changing the slope of the voltage regulation characteristic of the generator, i.e., the regulation difference coefficient, is provided in the excitation regulator of the excitation system, so that each generator set in parallel operation provides reactive power to the system according to its capacity, and realizes stable and reasonable distribution of the reactive power among the generator sets. The regulation difference coefficient δ is used to represent the slope of the curve of the voltage regulation characteristic (U G = f(I Q ), I Q is the reactive current) of the generator. The definition of the regulation difference coefficient is as follows: the rate of change of the terminal voltage of the generator when the power factor is equal to 0 and the reactive current changes from 0 to the rated value. The regulation difference coefficient is divided into positive regulation difference and negative regulation difference. The regulation difference coefficient is positive when the voltage decreases with the increase of the reactive load, which is called positive regulation difference. Conversely, the regulation difference coefficient is negative when the voltage increases with the increase of the reactive load, which is called negative regulation difference.

[0038] The specific settings of the units of Shanghai power grid are as follows:

[0039] At present, the power plants in Shanghai mainly adopt unit connection mode, that is, one generator and one corresponding main transformer are taken as a power generation unit, and multiple generators are connected in parallel at the high-voltage side of the main transformer. Therefore, there is also a problem of reactive power distribution among multiple power generation units of the power plant. The total regulation difference coefficient of a power generation unit is the sum of the generator regulation difference coefficient and the short-circuit reactance of the main transformer. Even if the generator regulation difference coefficient is 0, due to the short-circuit reactance of the main transformer, the total regulation difference of a power generation unit is equal to the short-circuit reactance of the main transformer, which is positive regulation difference, and can be operated in parallel. With the expansion of the power grid capacity, in order to limit the short-circuit current, the short-circuit reactance of the main transformer of the newly-operated unit is increased, the connection between the unit and the power grid is weakened, the sensitivity of the unit to the voltage drop of the power grid is reduced, and the supporting force of the unit to the reactive power of the power grid is also relatively weakened. Therefore, the units in Shanghai power grid adopt negative regulation difference to reduce the total regulation difference of a power generation unit, so as to improve the sensitivity of the unit to the voltage response of the power grid, and at the same time, keep the total regulation difference of a power generation unit as positive regulation difference to ensure the parallel operation of multiple power generation units in the power plant.

[0040] According to the characteristics of the AVC construction of the power plant, the pulse width output interval of the AVC is set as 15s to control the increase and decrease of the magnetic outlet of the unit, the influence of the pulse output of a specific time on the reactive power of the unit is viewed, the parameters of the unit and the system are recorded, and the stabilization time of the parameters of the unit after adjustment is viewed. The results are shown in Table 1:

[0041] Table 1: Record table of unit reactive power regulation and control setting experiment

[0042]

[0043]

[0044] According to the calculation results, the adjustment rate of the increase of the reactive power of the unit is 6.97Mvar / s, the adjustment rate of the decrease of the reactive power of the unit is 6.00Mvar / s, and the average adjustment rate is 6.49Mvar / s. Through calculation, when the adjustment pulse width is 500ms, the change amount of the reactive power of each adjustment pulse width is 3.25Mvar. Considering the dead zone range and adjustment accuracy set by the AVC software, it is suggested to set a reasonable adjustment pulse width of 500ms.

[0045] As Figure 2As shown, the adjustment coefficient is directly superimposed on the given value of the main control loop of the excitation system, which also reflects the importance of the adjustment, because the adjustment coefficient is directly superimposed on the given value of the main control loop of the excitation system, so the adjustment will inevitably affect the step size of the excitation system magnetic regulation and demagnetization. At present, the AVC system debugging of Shanghai Power Plant has been completed, and through the increase and decrease of magnetic pulse operation, a closed-loop control between AVC and excitation system is established. In the unit that has completed the AVC system debugging, the use of negative adjustment technology will change the adjustment pulse width of the excitation system. The AVC adjustment pulse width (adjustment step size) may increase with the increase of the negative adjustment coefficient, and in serious cases, it may exceed the dead zone of AVC, leading to AVC regulation failure. In the units that have completed the AVC debugging test, the adjustment pulse width is generally set to 500 ms, and the corresponding reactive power change is a constant. After the adjustment coefficient is modified, the reactive power change corresponding to a single adjustment pulse width may increase, which may exceed the limit of the reactive power change corresponding to a single adjustment pulse width of AVC.

[0046] Specifically, assuming that the reactive power change corresponding to a single adjustment pulse width is 17 Mvar, after using negative adjustment, the reactive power change corresponding to a single adjustment pulse width is amplified by 2 times, which is 34 Mvar, exceeding the adjustment dead zone of AVC 30 Mvar. At this time, the control unit displays that the higher the unit reactive power is, the more it is locked, and the AVC execution unit is locked for magnetic increase, leading to AVC regulation failure.

[0047] As shown in Figure 3 and Figure 4 Taking a unit in Shanghai as an example, a 0.1% step disturbance is performed to simulate an increase in magnetic pulse operation of AVC. The influence of the adjustment coefficient on the change of the unit output reactive power under the same disturbance is analyzed. It can be seen that under the same disturbance, the adjustment coefficient has different influences on the change of the output reactive power of different units.

[0048] The specific setting method is as follows:

[0049] First, check whether the unit adjustment coefficient needs to be optimized. If it needs to be optimized, first optimize and set the adjustment coefficient. If it does not need to be optimized, directly debug the AVC substation;

[0050] AVC substation debugging experiment is carried out. Under the condition of meeting the control accuracy and rate of AVC substation, the adjustment pulse width of AVC substation is modified. The optimization of the adjustment coefficient may increase the reactive power change of a single adjustment pulse width, the AVC adjustment step size is amplified, leading to AVC regulation failure. The influence of AVC regulation should be determined according to the different situations of each power plant. The power plant AVC substation single adjustment pulse width can be adjusted to ensure that the control accuracy and rate of AVC substation meet the requirements.

[0051] For example, the regulation accuracy of AVC reactive power control of a current power grid is ≤0.03 p.u., in the case of not changing the difference coefficient, the single regulation pulse width of the AVC substation is set as 500 ms by default, and the corresponding regulation accuracy is 0.03 p.u. If the difference coefficient is adjusted, the regulation accuracy of the single regulation pulse width is greater than 0.03 p.u. At this time, the regulation accuracy of AVC is adjusted by reducing the single regulation pulse width of AVC to 400 ms or 300 ms, so as to meet the requirement of the regulation accuracy of the current power grid.

[0052] The preferred embodiments of the present application are described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations without departing from the concept of the present application. Therefore, any technical solutions obtained by logical analysis, reasoning or limited experiments based on the concept of the present application and the prior art should be within the protection scope defined by the claims.

Claims

1. A method for setting a correction factor in cooperation with an AVC substation, characterized in that, The method comprises the following steps: Step 1: judging whether the regulation difference coefficient of the power grid unit meets the standard or the requirement of the dispatching department, if not, executing step 2, if yes, executing step 4; Step 2: optimizing and setting the regulation difference coefficient, setting according to the relevant standard or the requirement of the dispatching department, reducing the total regulation difference of one generating unit to improve the sensitivity of the unit to the voltage response of the power grid; Step 3: judging whether the regulation difference coefficient meets the standard or the requirement of the dispatching department, if not, returning to step 2, if yes, executing step 4; Step 4: performing the AVC substation debugging test, setting the regulation pulse width of the AVC substation under the condition of meeting the target of the AVC limiting function test; Step 5: judging whether the control precision and rate of the AVC substation meet the requirement, if yes, completing the setting, if not, returning to step 4; In step 4, the regulation pulse width of the AVC substation is set according to the regulation difference coefficient, the set dead zone range and the regulation precision, the AVC substation debugging test comprises a plurality of AVC debugging tests considering the influence of the regulation difference coefficient, namely the AVC limiting function test, which comprises bus voltage over-limit test, bus voltage under-limit test, unit reactive power over-limit test and unit reactive power under-limit test.

2. The method according to claim 1, wherein the adjustment coefficient is set in cooperation with the AVC substation. The setting mode of the power grid unit is specifically as follows: The power grid unit is set in the unit connection mode, namely one generator and one corresponding main transformer are taken as one generating unit, a plurality of generators are connected in parallel on the high-voltage side of the main transformer, and the power grid unit adopts negative regulation difference, the total regulation difference of one generating unit is reduced to improve the sensitivity of the unit to the voltage response of the power grid, and the total regulation difference of one generating unit is kept as positive regulation difference to ensure the parallel operation between a plurality of generating units in the power plant.

3. The method according to claim 1, wherein the method is characterized by, The regulation difference coefficient is used to represent the slope of the voltage regulation characteristic curve of the generator, namely the rate of change of the generator terminal voltage when the power factor is equal to 0 and the reactive current changes from 0 to the rated value.

4. The method according to claim 3, wherein the adjustment coefficient is set in coordination with the AVC substation. The expression of the voltage regulation characteristic of the generator is as follows: wherein, is the reactive current, is the generator voltage.

5. The method of claim 3, wherein the adjustment coefficient is set in cooperation with the AVC substation. The regulation difference coefficient is divided into positive regulation difference and negative regulation difference, the regulation difference coefficient is positive when the voltage decreases with the increase of the reactive load, which is called positive regulation difference, and the regulation difference coefficient is negative when the voltage increases with the increase of the reactive load, which is called negative regulation difference.

6. The method of claim 1, wherein the method is characterized by: The bus voltage over-limit test is specifically as follows: When the bus voltage is 232.2kV, the upper limit value of the bus voltage is set to be lower than the bus voltage, which is 230kV, at this time, the bus voltage over-limit lockout is displayed on the central control unit, the AVC execution unit is magnetically locked, and there is no increase or decrease of the magnetic pulse output.

7. The method of claim 1, wherein the method is characterized by: The bus voltage under-limit test is specifically as follows: When the bus voltage is 232.2kV, the upper limit value of the bus voltage is set to be lower than the bus voltage, which is 234kV, at this time, the bus voltage under-limit lockout is displayed on the central control unit, the AVC execution unit is magnetically locked, and there is no increase or decrease of the magnetic pulse output.

8. The method of claim 1, wherein the method is characterized by, The unit reactive power over-limit test is specifically as follows: The unit reactive power is set to be 32Mvar, and the actual upper limit value of the reactive power is 30Mvar, at this time, the unit reactive power over-limit lockout is displayed on the central control unit, the AVC execution unit is magnetically locked, and there is no increase or decrease of the magnetic pulse output.

9. The method of claim 1, wherein the method is used for setting the adjustment coefficient in cooperation with an AVC substation. The reactive power lower limit test of the unit is specifically: The reactive power of the unit is set to -2Mvar, the actual upper limit value of the reactive power is 0Mvar, at this time the central control unit displays that the lower limit of the reactive power of the unit is locked, the AVC execution unit is magnetically locked, and there is no magnetization pulse output and demagnetization pulse output.

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