RU2856420C1 - Method for controlling the operation of a turbogenerator by reactive power - Google Patents

Abstract

FIELD: electric power.

SUBSTANCE: invention relates to the regulation of synchronous generators with electromagnetic excitation operating in parallel with the grid, and can be used in developing control algorithms primarily for turbogenerators. In the method for controlling the operation of a turbogenerator by reactive power, based on determining the parameters of excitation current, stator current and stator voltage, by which the permissible operating modes of the turbogenerator are limited, according to the invention, the set or required operating mode of the turbogenerator before its change is checked on the turbogenerator using adjustment trends built for a specific turbogenerator. Control of the operating mode is carried out by comparing the data of the adjustment trends and the parameters taken from the turbogenerator. Based on the presence of deviation of the current operating mode of the turbogenerator, a conclusion is made about malfunctions in the operation of the turbogenerator or equipment connected to it, and the operation of the turbogenerator is transferred to another permissible mode. Determination of the parameters of excitation current, stator current and stator voltage is carried out using adjustment trends built on the basis of an array of initial data, including combinations of values of stator current I_s, excitation current I_e, angle between magnetic axes of rotor and stator d, turbogenerator voltage U_gen, angle between turbogenerator voltage and stator current j. Combinations (I_s, I_e, j, q, S, P, Q) of turbogenerator operating modes are formed, on the basis of which a family of dependencies of active P and reactive Q powers on excitation current I_e at various fixed values of apparent power S is built, taking into account limitations by the static stability margin coefficient k_SSM and minimum excitation current. At the same time, at a given active power P_given and corresponding values of excitation current I_e and reactive power Q, a limitation is imposed by the static stability margin coefficient k_SSM, where k_SSM і0.2, k_ssm =1-sin q. Permissible operating modes of the turbogenerator are determined by reactive power.

EFFECT: reduction in the complexity of implementing the method.

1 cl, 4 dwg

Description

Field of technology to which the invention relates

The invention relates to the field of electric power engineering, namely to the regulation of synchronous generators with electromagnetic excitation operating in parallel with the grid, and can be used in the development of control algorithms primarily for turbogenerators.

State of the art

A known method for controlling a three-phase synchronous generator (RU patent No. 2758996, published November 8, 2021, IPC No. H02P 9/14) involves generating a control signal to change the excitation current based on generator voltage data and measured armature current values. The generator excitation current is increased by an amount proportional to the ratio of the average generator current to the maximum phase voltage of the generator. During regulation, the maximum generator voltage is limited.

The disadvantage of this technical solution is the potential reduction in the generator's service life due to the lack of data on the permissible range of excitation current regulation in long-term operating modes.

A method is known for limiting the minimum excitation level of synchronous electric machines (Author's note SU No. 156213, published 21.08.1963, IPC H02P 9/10, H02J 3/24), in which, for reasons of static stability, it is proposed to set the minimum excitation current value depending on the active stator current, due to which, in some modes, the permissible range of excitation current regulation is expanded.

The disadvantages of this method are the low accuracy of determining the excitation current control range, as well as a decrease in the reliability of the turbogenerator due to the heating of the outer stator packages at low excitation currents.

A method for modeling the available reactive power of a turbogenerator is known (Author's Certificate SU No. 1381649, published March 15, 1988, IPC H02J 3/18). The invention proposes a method for calculating the operating mode of a synchronous electric machine based on a lumped-parameter model, taking into account the saturation of magnetic circuits. The essence of the proposed approach consists of decomposing the measured stator current into actual active and reactive currents. The latter is increased to the desired value for reactive power and summed with the actual active current, thereby obtaining the simulated total stator current. The simulated rotor current is obtained by multiplying the magnetizing current corresponding to the internal EMF by the ratio of the transverse axis EMF to the internal EMF. The simulated rotor current and the simulated total stator current are compared with the corresponding permissible values, with the specified increase in the simulated reactive current being carried out until either the simulated total stator current or the simulated rotor current reaches the permissible value. When these currents reach the permissible value, the simulated stator reactive current is recorded. The available reactive power is determined by multiplying the fixed value of the simulated stator reactive current by the stator voltage.

The disadvantages of this technical solution are low accuracy, as well as a decrease in the reliability and service life of the generator due to the lack of justification for the limitation on the minimum excitation current.

The closest in technical essence to the proposed invention is a method for determining the permissible operating modes of a hydrogenerator for specific equipment (Ilic, I., et al., Methodology for Determining the Actual PQ Diagram…, Energija, vol. 56(2007), No. 2, pp. 144-181), based on determining the parameters of the excitation current, stator current and stator voltage, which limit the permissible operating modes of the turbogenerator. It uses additional measurements during tests in the XX, short-circuit and load modes, based on which the limitations on the permissible modes are determined. The limitations are based on the heating of the stator winding, rotor and steel. To obtain data, special tests are carried out, and additional sensors are installed to monitor the temperature and magnetic field. In this case, the permissible modes are determined taking into account the electromagnetic and thermal state in the end zone. Moreover, the clarification of the data on the permissible operating modes is carried out periodically, since they are affected by the technical condition of the generator, including its service life. Based on the changes between the measurement results, a conclusion is made about the presence and development of damage.

The disadvantage of this technical solution is the technical complexity of implementation due to the need to conduct labor-intensive field experiments.

Disclosure of the essence of the invention

The technical objective of the proposed invention is to reduce the time and resources required to determine the permissible control zone when controlling the operation of a turbogenerator.

The technical result consists in reducing the complexity of implementing the method.

This is achieved by the fact that in the known method of controlling the operation of a turbogenerator based on reactive power, based on determining the parameters of the excitation current, stator current and stator voltage, which limit the permissible operating modes of the turbogenerator, according to the invention, the specified or required operating mode of the turbogenerator before changing it on the turbogenerator is checked using control trends constructed for a specific turbogenerator, the operating mode is monitored by comparing the data of the control trends and the parameters taken from the turbogenerator, based on the presence of a deviation in the current operating mode of the turbogenerator, a conclusion is made about malfunctions in the operation of the turbogenerator or equipment connected to it, the operation of the turbogenerator is transferred to another permissible mode, while the parameters of the excitation current, stator current and stator voltage are determined using control trends constructed on the basis of an array of initial data, including combinations of the values of the stator current I _c , excitation current I _в , the angle between the magnetic axes of the rotor and stator δ, the voltage of the turbogenerator U _gen , the angle between the voltage turbogenerator and stator current ϕ, and for each value of stator current I _{c ,} a family of dependencies of generator voltage U _g on excitation current I _v and angle δ is constructed, and for a given turbogenerator voltage, possible combinations of I _v and δ are determined, thereby forming all theoretically possible combinations (I _c , I _v , δ), for each value of stator current I _{c ,} families of dependencies of angle ϕ on excitation current I _v and angle δ are constructed, and for each of the theoretically possible combinations (I _c , I _v , δ) the values of angle ϕ are determined, from which the load angle θ is calculated using the formula θ = δ - ϕ - 90°, then the values of total S, active P and reactive Q powers are calculated using the formulas P = S ⋅ cos ϕ, Q = S ⋅ sin ϕ, thereby forming all theoretically possible combinations (I _c , I _in , ϕ, θ, S, P, Q) of the operating modes of the turbogenerator, on the basis of which a family of dependencies of the active P and reactive Q powers on the excitation current I _in is constructed at various fixed values of the apparent power S, taking into account the restrictions on k _SZU and the minimum excitation current, then a restriction on the static stability reserve factor k _ZSU is imposed on the data cut at a given active power P _zad and the corresponding values of the excitation current I _in and the reactive power Q, where k _ZSU ≥ 0.2, k _ZSU = 1 - sin θ, the permissible operating modes of the turbogenerator are determined by the reactive power.

Brief description of the drawings

The essence of the invention is explained by the drawings, where Fig. 1 shows a family of dependencies of the generator voltage U _gen on the excitation current I _in at different angles δ between the magnetic axes of the rotor and stator, Fig. 2 shows a family of dependencies of the angle between the current and voltage ϕ of the generator on the excitation current I _in at different angles δ between the magnetic axes of the rotor and stator, Fig. 3 shows the dependence of the active P and reactive Q powers on the excitation current I _in at a given voltage U _g = U _zad , Fig. 4 shows the control trends for the turbogenerator.

Implementation of the invention

The method for controlling the operation of a turbogenerator based on reactive power is carried out as follows.

The excitation current, stator current, and stator voltage parameters that limit the permissible operating modes of the turbogenerator are determined. The specified or required operating mode of the turbogenerator is verified before changing it using control trends constructed for the specific turbogenerator. The operating mode is monitored by comparing control trend data with parameters read from the turbogenerator. Based on the presence of deviations in the current operating mode of the turbogenerator, a conclusion is drawn about malfunctions in the turbogenerator or equipment connected to it, and the turbogenerator is switched to another permissible operating mode. When switching modes, a preliminary assessment allows for determining the safety of the transition to the new mode.

Regulatory trends are built individually for each turbogenerator, including taking into account the specifics of the introduced additional restrictions, which may be caused by the technical condition of the turbogenerator or restrictions associated with the operation of the turbine.

A complete three-dimensional model of the electromagnetic field of the active part of a turbogenerator is constructed, for example, using industrial computer software, employing a numerical analysis of three-dimensional electromagnetic fields taking into account the end parts. The values of the stator current I _c , the excitation current I _в , and the angle between the magnetic axes of the rotor and stator δ are specified in the following ranges: I _c - from zero to the nominal value; the excitation current I _в - from the nominal value to 20% of the nominal; δ - within the range of θ ÷ 180 electrical degrees. The generator voltage U _gen and the angle ϕ between the generator voltage U _gen and the stator current I _c are calculated.

The obtained combinations of values (I _c , I _in , δ, U _gen , ϕ) represent an array of initial data, unique for each generator model and are the basis for constructing adjustment trends.

Using the array of initial data, the possible operating modes of the generator are determined for a given network voltage U _gen = U _nom ± 5%. For each of the possible values of the stator current I _c = I _c1 , families of dependencies of the generator voltage U _g on the excitation current I _v and the angle δ between the magnetic axes of the rotor and stator are constructed - U _gen (I _v , δ).

Next, a data cut is made for a given generator voltage U _gen = U _da and the possible combinations of I _in and δ under the given conditions are determined (Fig. 1).

Thus, all theoretically possible combinations (I _c , I _in , δ) are formed at U _gen = U _zad , which represent the parameters of the generator operating modes at a given voltage.

Similarly, based on the array of initial data for each value of the stator current I _{c ,} families of dependencies of the angle ϕ on the excitation current I _in and the angle δ - ϕ( I _in , δ) are constructed (Fig. 2).

From the constructed dependencies for each of the found combinations (I _c , I _in , δ), the angle ϕ is determined.

Using the found values of the angle ϕ for each of the found combinations (I _c , I _in , δ), the load angle θ is calculated

The obtained data on the parameters of the generator operating modes (I _c , I _in , δ, ϕ, θ) at a given voltage U _gen = U _zad are supplemented by the values of the total S, active P and reactive Q powers:

Thus, all theoretically possible combinations (I _c , I _in , ϕ, θ, S, P, Q) are formed at U _gen = U _zad , - an array of data on the possible operating modes of the turbogenerator.

Using a data set on the possible operating modes of a turbogenerator, the dependences of the active P and reactive Q powers on the excitation current Iv are constructed _at a given voltage _Ug = _Uzad under various conditions, for example, a change in the reactive power Q at a constant active power P. For this purpose, a family of dependences of the active P and reactive Q powers _on the excitation current Iv is constructed at various fixed values of the apparent power S, taking into account the constraints on k _ZSU and the minimum excitation current (Fig. 3). Then, a data slice is made for a given active power _Pzad and the corresponding values of the excitation current _Iv and the reactive power Q are determined.

Based on the obtained data, control trends are constructed for the turbogenerator while maintaining constant active power and changing reactive power at a given voltage U _g = U _zad (Fig. 4).

Then, a limitation is imposed on the adjustment trends based on the static stability safety factor

And they determine the permissible operating modes of the turbogenerator based on reactive power.

The obtained characteristics are used to control and monitor the operating modes of the turbogenerator by setting the corresponding excitation current values in the absence of a change in the turbine torque, that is, in the following cases:

- when setting the required operating mode for consumption or generation of reactive power (without changing active power);

- when varying reactive power to maintain constant voltage.

The advantages of this technical solution include increased calculation accuracy due to the use of data from three-dimensional numerical modeling of the electromagnetic field of a turbogenerator, taking into account the nonlinear properties of materials and the pronounced saturation of the stator and rotor steel and effects in the end zones, as well as increased convenience for practical use.

The use of control trends allows for a more accurate determination of the permissibility of the turbogenerator operating modes, taking into account the characteristics of specific equipment.

The use of the invention makes it possible to control the operation of a turbogenerator by preliminarily assessing the required mode when regulating reactive power, and also to formulate recommendations for setting the operating modes of a turbogenerator in the form of control trends calculated on the basis of an electromagnetic field analysis, which represent the dependences of active and reactive power on the excitation current at a given generator voltage or a given voltage in an established network cross-section, obtained by a calculation method (and not in kind, as in the prototype method), which makes it possible to increase the reliability of the generator and accurately determine the reactive power reserve in a given operating mode of the turbogenerator.

The use of the invention makes it possible to reduce the time and resource costs required to determine the permissible control zone when controlling the operation of a turbogenerator by determining the permissible modes based on control trends pre-calculated using numerical modeling of electromagnetic fields, thereby reducing the complexity of implementing the method.

Claims (1)

A method for controlling the operation of a turbogenerator based on reactive power, based on determining the parameters of the excitation current, stator current and stator voltage, which limit the permissible operating modes of the turbogenerator, characterized in that the specified or required operating mode of the turbogenerator before changing it on the turbogenerator is checked using control trends constructed for a specific turbogenerator, the operating mode is monitored by comparing the data of the control trends and the parameters taken from the turbogenerator, based on the presence of a deviation in the current operating mode of the turbogenerator, a conclusion is made about malfunctions in the operation of the turbogenerator or equipment connected to it, the operation of the turbogenerator is transferred to another permissible mode, wherein the parameters of the excitation current, stator current and stator voltage are determined using control trends constructed on the basis of an array of initial data, including combinations of the values of the stator current I _c , excitation current I _в , the angle between the magnetic axes of the rotor and stator δ, the voltage of the turbogenerator U _gen , the angle between the voltage of the turbogenerator and the current stator ϕ, and for each value of the stator current I _{c ,} a family of dependencies of the generator voltage U _g on the excitation current I _v and the angle δ is constructed, and for a given voltage of the turbogenerator, possible combinations of I _v and δ are determined, thereby forming all theoretically possible combinations (I _c , I _v , δ), for each value of the stator current I _c , a family of dependencies of the angle ϕ on the excitation current I _v and the angle δ are constructed, and for each of the theoretically possible combinations (I _c , I _v , δ), the values of the angle ϕ are determined, from which the load angle θ is calculated using the formula θ = δ - ϕ - 90°, then the values of the total S, active P and reactive Q powers are calculated using the formulas P = S ⋅ cos ϕ, Q = S ⋅ sin ϕ, thereby forming all theoretically possible combinations (I _c , I _in , ϕ, θ, S, P, Q) of the operating modes of the turbogenerator, on the basis of which a family of dependencies of the active P and reactive Q powers on the excitation current I _in is constructed at various fixed values of the apparent power S, taking into account the restrictions on k _ZSU and the minimum excitation current, then a restriction on the static stability reserve factor k _ZSU is imposed on the data cut at a given active power P _zad and the corresponding values of the excitation current I _in and the reactive power Q, where k _ZSU ≥ 0.2, k _ZSU = 1 - sin θ, the permissible operating modes of the turbogenerator are determined by the reactive power.