RU2722642C1 - Method for automatic determination of frequency characteristic steepness of an isolated power connection - Google Patents

Abstract

FIELD: electric power engineering.

SUBSTANCE: for automatic determination of steepness of frequency characteristic of isolated power connection, measurements of load powers are performed, sum of powers of load nodes PS is determined, initial data are given: rated power of turbine equipment of power plants, rated power of power units of power plants, steepness of static characteristic of automatic controllers of rotation frequency of power units of power plants, indicator of approximation function of experimental or calculated data on changes of AC voltage frequency at emergency disconnection of power units at various values of reserve ratio, coefficient of regulating effect of load by frequency, information on the state of the generating equipment (included in the network / disconnected from the network). In addition, measurements of ambient air temperature at power plants are performed, values of rated power of power units of power plants for current ambient air temperature are corrected. Steepness of frequency characteristic is determined using given formulas.

EFFECT: high accuracy of automatic selection of control actions by complexes of anti-accident automation of isolated power connections.

1 cl

Description

Technical field

The invention relates to the electric power industry and is intended to determine the optimal volumes of control actions (HC) implemented by emergency control devices (PA) in isolated energy systems.

State of the art

Currently, there are a number of energy systems (ES) in Russia that provide full-fledged long-term isolated work from the Unified Energy System (UES) of Russia or forced short-term isolated work due to emergency outages of power lines connecting them to the UES of Russia. Examples of such energy systems can be the energy systems of the Chukotka Autonomous Okrug, Kamchatka Krai, Sakhalin and Magadan Regions, Norilsk-Taimyr and Nikolaev energy districts, as well as energy systems of the Republic of Sakha (Yakutia), the Republic of Karelia, the Republic of Komi, the Arkhangelsk Region, the Murmansk Region and other regions of Russia.

Unlike large power systems, interconnected by powerful electrical connections and having a sufficient amount of primary and secondary reserve of active power at power plant generators, the most frequent occurrence of emergency unbalances of active power leads to a change in the frequency of the alternating voltage in excess of the permissible values in isolated ES. First of all, this circumstance is due to the commensurability of the capacities of individual emergency shutdown power units of power plants with the total power of the isolated electric power plants themselves, as well as the relatively small values of the equivalent inertial time constants of such power systems.

In order to control the quality of frequency regulation in ES, dispatch centers should determine the steepness values of the static frequency characteristics of energy systems (SCH) for each case of imbalance of active power, leading to a frequency deviation of 0.05 Hz or more.

There is a method of determining the steepness of the frequency response of the power system (Organization Standard. Frequency and active power regulation in the UES of Russia. Standards and requirements. STO 59012820.27.100.003-2012), which consists in comparing the value of the jump-like change in the exchange power of the power system with the value of the frequency-hopping directly on the first 30 seconds of the transition process (before the intervention of the secondary regulation) according to the waveforms of the emergency (or experimental) transients using the ratios (1) and (2):

, (1)

, (1)

where σ is the slope of the static frequency response;

ΔP _s - change in the total external flow (exchange power), MW;

P _with - quasi-steady-state total external flow, MW;

P _с0 - initial total external overflow, MW;

Δf is the change in frequency, Hz;

f is the quasi-steady-state frequency value, Hz;

f ₀ - the initial value of the frequency, Hz.

, (2)

, (2)

where ΔP _NB is the primary imbalance of active power for generation and consumption, MW.

Relation (1) is used to determine the frequency response of the territorial (integrated) and regional power systems, except for those within which a fixed emergency incident occurred (or an experiment was conducted).

Relation (2) is used to determine the frequency response of the territorial (integrated) and regional power systems within which a fixed emergency incident occurred (or an experiment was conducted).

Since in the isolated operating mode of the ES ΔP _с = 0, to determine the frequency response of the isolated ES, expression (2) is converted to expression (3):

. (3)

. (3)

Due to the fact that the value of σ depends on factors such as the presence of an active power reserve at the power plant generators in the current mode, the composition of the power plant generators operating in the network, the position of the operating point of the speed controllers in the dead zone, etc., the main disadvantage of this of the method is the need to conduct a sufficiently large number of experiments in an isolated ES, allowing accurate determination of the value of σ for the entire possible variety of circuit-mode situations.

The most common way to compensate for emergency imbalances of active power that occur in isolated ESs is currently the use of additional automatic unloading (DAR) devices or automatic unloading devices when the generator or power unit (AROG or AROB) is turned off, which relate to local PA devices. These PA complexes implement control actions according to the hydrocarbon tables pre-formed by the technologist, without reference to the parameters of the real-time mode.

In addition to the local PA devices, which generate and implement control actions based on local circuit-mode information, the centralized emergency automation systems (TsSPA) are used in the energy systems of Russia, which monitor the power regime of the energy system or part thereof and automatically calculate the response parameters of emergency automation devices, included in DSPA, with reference to the real-time mode.

At the moment, in the TsSPA complexes (for example, in the TsSPA complex of the United Energy System (UES) of the East, operating in isolation from the UES of Russia), it is possible to select control actions according to the criterion of ensuring an acceptable frequency deviation in the post-emergency mode. At the same time, HC taking into account changes in the frequency in the ES are calculated according to the algorithm described in the article “Algorithm for assessing static stability and selecting control actions under the condition of ensuring static stability in the emergency mode” (Isaev EV [et al.] // Izvestiya NTTs Edinoy energy system. - 2013, No. 1 (68). - P. 48-57) using the formula (4):

, (4)

, (4)

where Δf is the change in frequency in the emergency mode in relative units;

ΔP _NB - primary imbalance of active power for generation and consumption, MW;

ΣP _tinom - the sum of the rated power of the turbine equipment involved in the primary frequency regulation, MW;

ΣP _{n is the} sum of the capacities of the load nodes of the ES, MW;

K _gf , K _{nf are the} coefficients of the regulatory effect of generation and load in frequency.

Thus, at present, in the TsSPA OES of the East, to determine the steepness of the frequency response of an isolated energy connection σ, a method is used that consists in calculating this parameter according to expression (5):

. 5)

. 5)

The values of the variables ΣP _{thi ohm} and ΣP _n in the considered method for determining the value of σ are calculated by the program module for assessing the state of the calculation model based on real-time data, while the coefficients K _gf and K _nf are manually set by the technologist based on empirical data.

The method for determining σ by the software and hardware complex TsSPA is taken as a prototype. The main disadvantages of this method are the limitation of the reliability of determining σ by the amount of active power unbalances (these unbalances should not lead to the output of power regulators of turbines of power plants beyond the dead band of the primary control), as well as the need for a significant number of field tests to accurately determine the coefficients K _gf and K _nf ( as well as σ, depending on the current circuit-mode situation) and manual changes in their values in real time. In this regard, despite the fact that the value of σ can vary significantly depending on the current operating mode of the power system, in practice, fixed values of σ are currently used, which can lead to significant errors in the calculation of HC.

It is known that the coefficient K _nf is determined by the qualitative composition of consumers of electric power (household, industrial and other loads) and for the energy systems of Russia varies in a fairly narrow range (1 ÷ 3). Due to the fact that it is not possible to take into account the detailed composition of consumers at each moment of the energy system’s operation, the average value of K _нf , which is determined on the basis of empirical or calculated data, is taken for HC calculations.

The coefficient K _{gf is} determined by a sufficiently large set of factors such as the composition of power plant generators, the circuit-balance situation, the presence of a rotating reserve, the position of the operating point of the speed controllers in the dead zone, etc. The parameters under consideration can vary significantly even within one day, therefore, in contrast from the coefficient K _nf , the coefficient K _gf can vary within a fairly wide range (from 0 to 25 or more) [1-4].

It should be noted that when designing energy systems, the total rated power of turbine equipment is determined based on the maximum power consumption of the electric power station, as well as the possibility of power plant generators being put into repair or emergency shutdown. Therefore, in the vast majority of circuit-balanced situations, the value of ΣP _{ti nom} significantly exceeds the value of ΣP _n (in some cases, up to 2 times). Thus, the steepness of the frequency response of an isolated operating energy _{combination is} primarily determined by the value of the product K _gf · ƩP _tin , which introduces the greatest error in determining the value of σ.

SUMMARY OF THE INVENTION

The technical result of the proposed method is to increase the accuracy of the automatic selection of hydrocarbons by PA complexes of isolated ES.

To automatically determine the steepness of the frequency response of an isolated operating power connection by the emergency control device, measurements of the load capacities are carried out, the sum of the power of the load nodes (ΣP _n ) is determined, and the following initial data are set that are not dependent on the current mode of the isolated working power connection:

- rated power of the turbine equipment of power plants (P _{ti nom} ) according to the passport data;

- Nominal capacities of power units of power plants (P _gin ) corresponding to the outdoor temperature + 15 ° С (according to the Order of the Ministry of Energy of the Russian Federation dated February 11, 2019 No. 90 “On approval of the Rules for testing and determination of system-wide technical parameters and characteristics of generating equipment and amending the Rules for the technical operation of power plants and networks of the Russian Federation, approved by order of the Ministry of Energy of Russia of June 19, 2003 No. 229 ”), according to the passport data;

- the steepness of the static characteristics of the automatic speed control of power units of power plants (K _gif ) according to the passport data;

- an indicator of the approximation function of experimental or calculated data on changes in the frequency of the alternating voltage during emergency shutdown of power units at various values of the reserve coefficient (r), determined by the method described in [5];

- coefficient of the regulatory effect of the load in frequency (K _nf ), determined on the basis of the calculated (experimental) data or empirically.

In addition, measurements of the outside temperature at power plants are performed and, based on the measurements, P _gynom.t values are _generated , which are defined as the adjusted values of the rated power of the power units P _{gynom of the} power plants of an isolated power _source for the current outdoor temperature.

The values of ΣP _n and P _gynom.t , as well as information on the state of the generating equipment of an isolated energy connection (included in the network / disconnected from the network), necessary to determine the sum of P _gynom.t and the sum of the products K _gif and P _gynom.t in real time time, arrive at the emergency control device from the operational measuring complex (DEC) or another source of information about the real mode of operation.

Then, to determine the value of σ, equations (6) are applied:

, (6)

, (6)

where σ is the steepness of the frequency response of an isolated energy connection;

- крутизна статической характеристики автоматического регулятора частоты вращения эквивалентного генератора;

- the steepness of the static characteristics of the automatic speed controller of the equivalent generator;

ρ is the reserve ratio;

n is the number of generators that are in operation in an isolated operating energy combination;

f (ρ) is the function of approximating experimental or calculated data on changes in the frequency of the alternating voltage during emergency shutdown of generators (power units) at various values of ρ;

r is the exponent of the function f (ρ);

ΣP _tinom - the sum of the rated power of the turbine equipment involved in the primary frequency regulation, MW;

K _nf - coefficient of the regulatory effect of the load in frequency;

ΣP _n - the sum of the power of the load nodes of the ES, MW;

K _gif is the passport value of the slope of the static characteristic of the automatic speed controller of the i-th power unit;

P _ginom.t is the rated power of the i-th power unit for the current outdoor temperature, MW.

In this case, equations (6) are supplemented by logical condition (7), which characterizes the absence of an active power reserve at the i-th power unit and its non-participation in the primary frequency control:

, (7)

, (7)

where P _gi is the current power of the i-th power unit, MW.

The implementation of the invention

STC UES JSC together with SO UES JSC developed a software and hardware complex for emergency control systems of the Kaliningrad Power System (PTK PA), which calculates the amount of HC based on actual information about the power system operating modes, available emergency control volumes and the current load of generating equipment of Kaliningrad power plants power systems in real time.

In May 2019, the power system of the Kaliningrad region was tested for three days for the possibility of prolonged isolation of this electric power station for isolated operation.

One of the tasks solved during the tests was to analyze the effectiveness of the functioning of the PTK PA.

Based on the test results, it was concluded that in order to reduce the error in calculating the optimal HC volumes by the PTK PA complex, the existing algorithms of the PTK PA operation should be supplemented by calculating the setpoint σ in real time taking into account the composition of the generating equipment of power plants, the amount of available reserve of active power in the power plant in the after-accident the mode and temperature of outdoor air at power plants, which include GTU and CCGT power units, their thermal operating conditions, etc.

The proposed method solves the problem. The testing of this method was carried out by JSC "STC UES" as part of research work on the modernization of the algorithms of the PTK PA.

In addition to emergency control devices, the proposed method for calculating the steepness of the frequency response of an isolated energy connection can be used in operational dispatch control. So, for example, at the present time, if it is necessary to synchronize two isolated power systems in order to ensure an acceptable frequency difference, in some cases the dispatcher needs to carry out forced unloading (loading) of power plant generators by active power or limit the consumption of an isolated power system. In order to solve this problem, the dispatcher is currently using average empirical values of σ, which show how the frequency in the power system changes when the generation (consumption) of active power changes. In the event that the calculated value of σ obtained in real time is transmitted to the dispatching personnel, then this information will allow for more accurate synchronization of two isolated associations.

Sources of information

1. Venikov V.A. Transient electromechanical processes in electrical systems: Textbook. for electric power. specialist. universities - 4th ed., revised. and add.

2. Rabinovich R.S. Automatic frequency unloading of power systems. - 2nd ed., Revised. and add. - M .: Energoatomizdat, 1989 .-- 352 p.

3. Weinstein R.A., Kolomiyets N.V., Shestakova V.V. Fundamentals of controlling the regimes of power systems in frequency and active power, in voltage and reactive power. - Publishing house of Tomsk Polytechnic University, 2010.

4. Sterninson L. D. Transients in the regulation of frequency and power in power systems. - M .: Energy, 1975.

5. Vitek V., Molish Z. To determining the steepness of the natural frequency response of the energy system of Czechoslovakia // News of the USSR Academy of Sciences. Energy and transport. 1965, No. 1. S. 38-42.

Claims (16)

A method for automatically determining the steepness of the frequency response of an isolated energy connection by an emergency control device, namely, that they measure the load capacities, determine the sum of the power of the load nodes, specify: the rated power of the turbine equipment of power plants according to the passport data, the coefficient of the regulatory effect of the load in frequency, characterized in what the rated power of the power units of the power plants is set according to the passport data, the slope of the static characteristic of the automatic speed controllers of the power units of the power plants according to the passport data, an indicator of the approximation function of the experimental or calculated data on changes in the frequency of the alternating voltage during emergency shutdown of the power units at various values of the reserve coefficient, measure the outdoor temperature at power plants, adjust the values of the nominal capacities of power units of a power plant d, depending on the outdoor temperature, in the current operating mode of an isolated power system, the switching state of the power units is determined and the frequency response slope is determined according to the following equations:

where σ is the steepness of the frequency response of an isolated energy connection; K ' _{g f} - the steepness of the static characteristics of the automatic speed controller of the equivalent generator; ρ is the reserve ratio; n is the number of generators that are in operation in an isolated operating energy combination; f (ρ) is the function of approximating experimental or calculated data on changes in the frequency of the alternating voltage during emergency shutdown of generators (power units) at various values of ρ; r is an indicator of the approximation function of experimental or calculated data on changes in the frequency of an alternating voltage during an emergency shutdown of power units at various values of ρ; ΣP _{t i nom} - the sum of the nominal capacity of the turbine equipment involved in the primary frequency regulation, MW; K _{n f} - coefficient of the regulatory effect of the load in frequency; ΣP _n - the sum of the power of the load nodes of the ES, MW; K _{g i f} - passport value of the slope of the static characteristic of the automatic speed controlleripower unit; R _{g i number t} - rated poweripower unit for the current outdoor temperature, MW, in this case, the equations are supplemented by a logical condition characterizing the absence of a reserve of active power at the i- th power unit and its non-participation in the primary frequency control:

, where R _{g i} is the current power of the i- th power unit, MW.