CN110797886A

CN110797886A - Load frequency control structure and combined frequency modulation model of water or thermal power generating unit

Info

Publication number: CN110797886A
Application number: CN201911235260.6A
Authority: CN
Inventors: 李小鹏; 李勇; 王民昆; 罗卫华; 兰强; 刘明忠; 王智娴; 张凯锋; 毕文骏
Original assignee: Electric Power Research Institute of State Grid Sichuan Electric Power Co Ltd; Southwest Branch of State Grid Corp
Current assignee: Electric Power Research Institute of State Grid Sichuan Electric Power Co Ltd; Southwest Branch of State Grid Corp
Priority date: 2019-12-05
Filing date: 2019-12-05
Publication date: 2020-02-14
Anticipated expiration: 2039-12-05
Also published as: CN110797886B

Abstract

The invention discloses a load frequency control structure and a combined frequency modulation model of a water or thermal power generating unit, and solves the problems that no adaptive parameter adjustment strategy can well match the requirement of power fluctuation of the water or thermal power generating unit and can not well ensure that the frequency can be well controlled in the prior art when different running modes in the rich and poor water periods are considered. The invention comprises a method and a system for constructing and applying a two-region alternating current-direct current water-fire-electricity combined frequency modulation model and simulation of the model. The invention considers different running modes of the rich and dry periods, provides adaptive parameter adjustment, and considers the parameter adjustment strategy of the rich and dry periods to promote the improvement of the economy of the power grid and the more reasonable utilization of energy.

Description

Load frequency control structure and combined frequency modulation model of water or thermal power generating unit

Technical Field

The invention relates to a water, fire and electricity combined regional power system, in particular to a load frequency control structure and a combined frequency modulation model of a water or thermal power generating unit.

Background

With the continuous expansion of the scale of the power grid, the application of multiple resources in coordination and participation in frequency control is increasingly wide. Meanwhile, the modern industrial development concept advocating energy conservation and environmental protection puts forward new requirements on application modes of various frequency modulation resources.

In recent years, the scale of a power grid is increasingly large, the interconnection degree between areas is continuously enhanced, the problems of energy shortage and power supply shortage in economic development areas are solved, and resource development and utilization are more fully and reasonably realized. The gradually expanding power systems also have drawbacks: the frequency is an important parameter in the stable operation of the power system, when the system load changes, the frequency fluctuation can cause great influence on the power grid in a larger range, and the cascading failure caused by the diffusion of local accidents occurs, so that large-area power failure is caused, and inconvenience is brought to industrial production and resident life. Currently, joint frequency modulation of multiple resources is becoming a development trend.

Taking hydroelectric and thermal power resources as an example, thermal power as a traditional power generation form has stable operation, but has low economy and is very limited in environmental protection, and meanwhile, in the current industrial society with energy shortage, coal as a non-renewable energy source needs to be reasonably exploited and utilized; hydroelectric power generation has a great deal of advantages such as clean, high efficiency, flexibility, but hydroenergy resource receives climatic factors and geographical environment influence greatly, can not stably be applied to frequency modulation work, according to the size of discharge, can be divided into two parts a year: the rich water period and the dry water period.

In actual operation, the thermal power unit needs to additionally consume coal when climbing a slope, the climbing speed of the thermal power unit is restricted, and the thermal power frequency modulation range is smaller. In addition, the thermal power generating unit also has the problem of time delay and is slow to start.

In actual operation, the hydroelectric generating set is sensitive to frequency change, and the frequency modulation dead zone limitation is usually provided for avoiding repeated starting and stopping of the hydroelectric generating set caused by fine frequency fluctuation; meanwhile, the hydraulic turbine speed regulator also comprises a transient frequency compensation part and a PID (proportion integration differentiation) regulation module to finish quick response to frequency change. In addition, the turbine also has a permanent slip coefficient which can affect the depth of primary frequency modulation.

In summary, considering different operation modes in the withered water period, there is no adaptive parameter adjustment strategy in the prior art that can well match the requirement of power fluctuation of the hydro-thermal power generation unit, and it cannot be guaranteed that the frequency is well controlled.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the different operation modes in the withered water period are considered, and no adaptive parameter adjustment strategy in the prior art can well match the requirement of power fluctuation of the water-fire-electricity generating set, and meanwhile, the frequency cannot be well controlled. The invention provides a load frequency control structure and a combined frequency modulation model of a water or thermal power generating unit, which solve the problems.

The invention is realized by the following technical scheme:

the load frequency control structure of the thermal power generating unit comprises a speed regulator, a prime motor, a generator load model, a load frequency controller, a speed limiter and a time delay module;

the speed regulator is characterized in that: when the system load changes, the primary frequency modulation controller changes the valve through the inherent property of the speed regulator to change the input power of the prime motor;

the prime mover: the generator set is used for generating mechanical power and driving the generator set to generate electricity;

the generator load model is as follows: the engine set overcomes a model of the outward output power of the load borne by the engine set and is used for compensating the error between the load change of the system and the input power change of the generator set;

the load frequency controller: when the system load changes, the position of an air valve of the speed regulator is changed through a frequency modulator of the load frequency controller so as to change the secondary frequency modulation controller of the input power of the prime mover, the load frequency controller is used as a secondary frequency modulation link of manual control, and the secondary frequency modulation is a feedback link of primary frequency modulation; the rate limiter: the method is used for adjusting the ramp speed of the thermal power generating unit, which is restrained due to the extra consumption of coal when the thermal power generating unit climbs a ramp;

the time delay module: the method is used for compensating the delay time when the thermal power generating unit is started.

Further, when the prime mover is a steam turbine, for the steam turbine, when the position of the air valve is changed, the output power of the steam turbine is changed, so that the power of the generator is changed, and a first-order inertia link function is adopted:

wherein: Δ X_g(s) is the amount of change in valve position, Δ P_TIs the variation of the turbine output power; k_TIs the gain factor of the turbine; t is_TIs a vapor volume time constant, and the value is 0.1-0.3;

when the prime mover is a reheat turbine, the reheat turbine is changed on the basis of the first-order inertia link function, and the transfer function is as follows:

wherein: t is_rIs the reheat time constant, usually taken to be 10, K_rThe reheating coefficient is 0.2-0.3 times of the total power of the steam turbine.

The load frequency control structure of the hydroelectric generating set comprises a speed regulator, a prime motor, a generator load model, a load frequency controller, a transient frequency compensation part, a PID (proportion integration differentiation) adjusting module and an integral module for processing a permanent slip coefficient, and further comprises a dead frequency zone for setting the speed regulator;

the load frequency controller: when the system load changes, the position of an air valve of the speed regulator is changed through a frequency modulator of the load frequency controller so as to change the secondary frequency modulation controller of the input power of the prime mover, the load frequency controller is used as a secondary frequency modulation link of manual control, and the secondary frequency modulation is a feedback link of primary frequency modulation;

the dead zone of the speed regulator is as follows: the disturbance frequency filter is used for filtering disturbance frequency influencing repeated starting and stopping of the hydroelectric generating set;

the transient frequency compensation section: the frequency compensation device is used for rapidly compensating the frequency change of the hydroelectric generating set;

the PID adjusting module: the frequency control device is used for carrying out quick self-feedback adjustment on the frequency change of the hydroelectric generating set;

the integration module for processing the permanent state slip coefficient is an integration module for processing the depth coefficient influencing the primary frequency modulation.

Further, when the prime mover is a water turbine, considering the influence of the water hammer effect, the transfer function of the water turbine is as follows:

in the formula T_wIs the water hammer time constant, which is typically 1.

Further, the transient frequency compensation part and the PID adjusting module are positioned in a speed regulator of a load frequency control structure of the hydroelectric generating set, the integral module for processing the permanent slip coefficient is positioned in a prime motor of the load frequency control structure of the hydroelectric generating set, and a dead zone of the speed regulator is arranged on the speed regulator of the load frequency control structure of the hydroelectric generating set.

The two-region alternating current and direct current water, fire and electricity combined frequency regulation model comprises a load frequency control structure of a thermal power generating unit and a load frequency control structure of a hydroelectric power generating unit, wherein the load frequency control structure of the thermal power generating unit and the load frequency control structure of the hydroelectric power generating unit are communicated through a connecting line and are connected to a direct current power transmission part to form the two-region alternating current and direct current water, fire and electricity combined frequency regulation model.

Further, when the prime mover of the load frequency control structure of the thermal power generating unit is a steam turbine, for the steam turbine, when the position of the air valve is changed, the output power of the steam turbine also changes, so that the power of the generator changes, and a first-order inertia link function is adopted as follows:

when the prime mover of the load frequency control structure of the thermal power generating unit is a reheat turbine, the reheat turbine is changed on the basis of the first-order inertia link function, and the transfer function is as follows:

wherein: t is_rIs the reheat time constant, usually taken to be 10, K_rThe reheating coefficient is 0.2-0.3 times of the total power of the steam turbine;

when the prime mover of the load frequency control structure of the thermal power generating unit is a water turbine, considering the influence of a water hammer effect, the transfer function of the water turbine is as follows:

in the formula T_wIs the water hammer time constant, which is typically 1.

Further, the speed governor: when the system load changes, the primary frequency modulation controller changes the valve through the inherent property of the speed regulator to change the input power of the prime motor;

the rate limiter: the method is used for adjusting the ramp speed of the thermal power generating unit, which is restrained due to the extra consumption of coal when the thermal power generating unit climbs a ramp;

the time delay module: the delay time compensation method is used for compensating the delay time when the thermal power generating unit is started;

Further, when the system load changes, the primary frequency modulation changes the valve through the inherent property of the speed regulator to change the input power of the prime motor, and the secondary frequency modulation changes the position of the valve of the speed regulator through the frequency regulator;

the transfer function involved in this process is:

where Δ F(s) is the frequency change of the system, Δ P_c(s) is the output of the controller, Δ X_B(s) is the amount of change in the position of the governor's valve; g_n(s) a transfer function for representing the speed governor, K_n、T_nRespectively, the static gain and the time constant of the speed regulator, and R is the adjustment coefficient of the speed regulator.

Further, the tie line is simplified toThe direct current transmission part is simplified into a first-order inertia link

Wherein T is_DCIs the time constant of inertia.

The two-region AC/DC water-fire-electricity combined frequency modulation method comprises an adjustment method of a two-region AC/DC water-fire-electricity combined frequency modulation model in a rich water period or/and an adjustment method of a two-region AC/DC water-fire-electricity combined frequency modulation model in a dry water period: the method for adjusting the AC/DC water-fire-electricity combined frequency modulation model in the two regions of the full water period comprises the following steps: in the water-rich period, the speed regulators in the load frequency control structure of the hydroelectric generating set and the load frequency control structure of the thermal power generating set are subjected to parameter setting, and the frequency dead zone range and the permanent state slip coefficient of the load frequency control structure of the hydroelectric generating set are set, so that when the hydroelectric generating set and the thermal power generating set jointly run, the generating frequency generated by the hydroelectric generating set forms a main frequency modulation baseband item, the hydroelectric generating set serves as auxiliary frequency modulation, and the thermal power generating set serves as main frequency modulation;

the method for adjusting the alternating current-direct current water-fire-electricity combined frequency modulation model in the two regions in the dry season comprises the following steps: in the dry season, parameters of speed regulators in a hydroelectric generating set load frequency control structure and a thermal power generating set load frequency control structure are set, and a frequency dead zone of the hydroelectric generating set load frequency control structure is removed, so that when the hydroelectric generating set and the thermal power generating set jointly run, the generating frequency generated by the thermal power generating set forms a main frequency modulation baseband item, the thermal power generating set serves as auxiliary frequency modulation, and the hydroelectric generating set serves as main frequency modulation.

Further, the adjusting method of the alternating current-direct current water-fire-electricity combined frequency regulation model in the two regions of the water-rich period is that the frequency dead zone range of the secondary speed regulator is adjusted to be-0.003-0.003, the permanent state slip coefficient is selected to be adjusted to be 0.06, the PID parameter of the speed regulator is adjusted to be Kp-2 and Ki-0.2, the AGC parameter of the speed regulator is set to be 0.7 for thermal power and 0.3 for water and electricity;

the adjusting method of the alternating current-direct current water-fire-electricity combined frequency modulation model in the two regions in the dry season comprises the following steps: removing a frequency dead zone of the secondary speed regulator, selecting a permanent state slip coefficient to be 0.01, wherein the PID parameters of the speed regulator are as follows: kp is 5.6 and Ki is 1.2.

The method for constructing the two-region alternating current/direct current water/fire/electricity combined frequency modulation model comprises the following steps of:

s1: respectively modeling thermal power generating units and hydroelectric generating units, and establishing a single-region typical load frequency control structure; the single-region typical load frequency control structure consists of a speed regulator, a prime motor, a generator load model and a load frequency controller;

s2: adding a rate limiter and a time delay module in a thermal power generating unit-single-region typical load frequency control structure to obtain a thermal power generating unit-single-region improved load frequency control structure;

setting a dead zone of a speed regulator in a hydroelectric generating set-single-region typical load frequency control structure, adding a transient frequency compensation part and a PID (proportion integration differentiation) adjusting module in the speed regulator of the hydroelectric generating set-single-region typical load frequency control structure, and adding an integral module for processing a permanent state slip coefficient in a prime motor in the hydroelectric generating set-single-region typical load frequency control structure to obtain a hydroelectric generating set-single-region improved load frequency control structure;

s3: and connecting the hydroelectric generating set-single-region improved load frequency control structure and the thermal generating set-single-region improved load frequency control structure by using a connecting line, and simultaneously adding a direct-current power transmission part to obtain a two-region alternating-current/direct-current water/power and thermal-power combined frequency modulation model.

A system of a two-region alternating current-direct current water-fire-electricity combined frequency regulation model is characterized in that a module of a thermal power generating unit-single-region typical load frequency control structure and a module of a hydroelectric generating unit-single-region typical load frequency control structure are respectively built by utilizing a speed regulator, a prime motor, a generator load model and a load frequency controller;

a module of a thermal power generating unit-single-region typical load frequency control structure is improved by using a rate limiter and a time delay module, and a module of the thermal power generating unit-single-region improved load frequency control structure is obtained;

setting a dead zone of a speed regulator for a module of a hydroelectric generating set-single-region typical load frequency control structure, adding a transient frequency compensation part and a PID (proportion integration differentiation) regulation module in the speed regulator of the module of the hydroelectric generating set-single-region typical load frequency control structure, setting a frequency dead zone, and adding an integral module for processing a permanent state slip coefficient in a prime motor of the module of the hydroelectric generating set-single-region typical load frequency control structure to obtain a module of the hydroelectric generating set-single-region improved load frequency control structure;

and connecting the module of the hydroelectric generating set-single-region improved load frequency control structure and the module of the thermal generating set-single-region improved load frequency control structure by using a connecting line, and simultaneously adding a direct current transmission part to obtain the system of the two-region alternating current/direct current water/power/thermal power combined frequency regulation model.

Furthermore, as can be seen from the two-region alternating current/direct current water/power/fire/electricity combined frequency modulation model, 3 parts of parameters in total can affect the frequency modulation effect, namely the frequency modulation dead zone range of the speed regulator, the permanent state slip coefficient of the water turbine and the PID parameters of the speed regulator. The effect of three parameters in frequency modulation was analyzed:

frequency modulation dead zone: when the frequency fluctuates in the dead zone, the unit is not adjusted. The frequency modulation dead zone can be used for fixing the load and preventing the unit from being too sensitive to frequency fluctuation, but the frequency modulation dead zone can also cause the water turbine to lose the frequency modulation capability if the frequency modulation dead zone is not reasonably arranged. The larger the frequency modulation dead zone range is, the poorer the primary frequency modulation effect is.

Permanent state slip coefficient: meaning a continuously changing slope on the static characteristic curve of the governor. The unit difference rate and the primary frequency modulation depth are in inverse proportion, and the difference rate is related to the permanent state slip coefficient. The permanent state slip coefficient is increased, and the primary frequency modulation effect is deteriorated.

PID of a speed regulator: when the proportional coefficient is larger, the regulation speed is accelerated, the overshoot is increased, and the stability is reduced, when the integral time is shorter, the residual error eliminating capability of the system is stronger, and the differential part usually adopts incomplete differential. The PID of the speed regulator has two different parameter setting directions, the smooth fluctuation adjustment time is long when the stability is approached, the quick adjustment is approached, and the time is short but the large overshoot of the oscillation is large.

Parameter adjustment strategies under different operation modes:

further, the conventional thermal power generating unit gradually exposes many problems as the power system develops. Firstly, the characteristics of the thermal power generating unit, such as limited climbing speed and long start-stop time, determine that the effective regulating range is smaller and the regulating response time is longer when the thermal power generating unit regulates the load. Secondly, the large demand of the thermal power generating unit on the coal resources increases the power generation cost and reduces the economical efficiency of the system. However, the advantages of the thermal power generating unit are not ignored, the whole operation of the thermal power generating unit is very stable after the thermal power generating unit is normally started, the thermal power generating unit is not restricted by seasons, and the thermal power generating unit does not change along with the change of time or weather.

Furthermore, the hydroelectric generating set is widely concerned by the characteristics of high starting and stopping speed, flexible adjustment, capability of quickly responding to load change and wide adjustment range. However, the uncertainty of facing the hydraulic energy source is large, and the practical application of the hydraulic energy source is greatly influenced by the climate change and the terrain difference. Depending on the size of the water flow, a year can be divided into two parts: the rich water period and the dry water period.

Further, in view of the above problems, the operation mode of the hydroelectric power combined frequency modulation in the dry season is as follows:

in the water-rich period, the water quantity is sufficient, so that the phenomena of waste water and water abandonment are avoided in order to fully utilize resources, the hydroelectric generating set is used for bearing stable base load, and the thermal power generating set is used for bearing a main frequency modulation task. In the dry season, due to the fact that less water is supplied, the hydroelectric generating set serves as a main frequency modulation unit to bear the rapidly changing load, and the thermal power generating set operates with stable base load and assists in participating in frequency modulation.

According to different operation modes, basic loads are borne by water and electricity and thermal power in the rich and dry periods respectively, and the unit bearing the basic loads is expected to have smooth power change and is used for frequency modulation in an auxiliary mode.

Further, the adjustment strategy of the parameters of the withered water period is proposed as follows:

and (3) a water enriching period:

the dead zone range of the speed regulator is set to be larger, so that the hydroelectric generator set is insensitive to frequency change;

the permanent state slip coefficient bp is set to be larger, so that the hydroelectric generating set bears smaller power in primary frequency modulation;

the PID parameters emphasize stability, so that the power change of the hydropower region is relatively smooth.

And (3) a dry period:

the dead zone range of the speed regulator is set to be small, and hydropower is sensitive to frequency and can bear the load of sudden change;

setting the permanent state slip coefficient bp to be smaller so that the hydroelectric generating set bears more power in primary frequency modulation;

the PID parameters focus on rapidity, maintaining the frequency at the initial value as soon as possible.

By combining a parameter adjustment strategy of the water, power and electricity combined frequency modulation in the dry season, the water, power and electricity combined frequency control action logic can be provided as follows:

according to month refreshing frequency modulation parameters, firstly carrying out frequency modulation by a hydroelectric generating set in a dry water period, if the load change is overlarge for a period, then carrying out frequency modulation by the thermoelectricity generating set, if the load change is overlarge for a period, firstly carrying out frequency modulation by the thermoelectricity generating set, and if the load change is overlarge for a period, then carrying out frequency modulation by the hydroelectric generating set (the primary frequency modulation is inherent, and the frequency modulation participation refers to secondary frequency modulation capacity allocation).

The invention has the following advantages and beneficial effects: the resources are fully utilized, the coal consumption is reduced, and the economical efficiency of a power grid is improved. The invention considers different running modes in the rich and dry water period, provides an adaptive parameter adjustment strategy and completes simulation work. The simulation curve shows that the proposed parameter setting strategy can meet the requirement on power fluctuation of the water-fire-electricity generator set, and meanwhile, the frequency can still be well controlled. The parameter adjustment strategy considering the withered water period can promote the improvement of the economy of the power grid and the more reasonable utilization of energy.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

fig. 1 is a diagram of a model of a governor of the present invention.

Fig. 2 is a schematic diagram of a prime mover model according to the present invention.

Fig. 3 is a diagram of a generator load model architecture according to the present invention.

Fig. 4 is a diagram illustrating a single-region exemplary load frequency control structure according to the present invention.

Fig. 5 is a schematic diagram of a complete thermal power generating unit model according to the present invention.

Fig. 6 is a schematic view of a complete model of a hydroelectric generating set according to the present invention.

FIG. 7 is a two-region AC/DC water/fire/electricity combined frequency modulation model of the present invention.

FIG. 8 is a diagram of the power change of the hydro-thermal generator set in two areas of the water-rich period.

FIG. 9 is a diagram showing the frequency variation of two regions in the water-rich period according to the present invention.

FIG. 10 is a diagram of the power change of the water-fire-electricity generator set in two areas in dry season.

FIG. 11 is a diagram showing the frequency change in two regions of the dry season of the present invention.

FIG. 12 is a diagram showing the control of the frequency of the dry season in accordance with the present invention.

FIG. 13 is a diagram of the variation of the power of the water-fire electric generator set in the dry season.

Fig. 14 is a diagram showing the influence of whether the thermal power generating unit of the present invention participates in secondary frequency modulation on the frequency.

Fig. 15 is a diagram illustrating an influence of whether the thermal power generating unit of the present invention participates in secondary frequency modulation on the power of the thermal power generating unit.

FIG. 16 is a diagram of the control of the water abundance period frequency according to the present invention.

FIG. 17 is a diagram of the power change of the water-fire electric machine set in the rich water period.

Fig. 18 is a diagram illustrating the influence of the participation of the hydroelectric generating set in secondary frequency modulation on frequency control.

Fig. 19 is a graph of the change in power of the hydroelectric generating set participating in the secondary frequency modulation after a period of time.

Detailed Description

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any inventive changes, are within the scope of the present invention.

the speed regulator is characterized in that: when the system load changes, the primary frequency modulation controller changes the input power of the prime motor by changing the valve through the inherent property of the speed regulator, and the model of the speed regulator is shown in figure 1;

the prime mover: the prime mover model is shown in figure 2 and is used for generating mechanical power and driving the generator set to generate electricity;

In actual operation, the thermal power generating unit needs to additionally consume coal when climbing a slope, the climbing speed of the thermal power generating unit is restricted, and the thermal power frequency modulation range is smaller. In addition, the thermal power generating unit also has the problem of time delay and is slow to start. In view of the above two problems, a time delay module and a rate limiter need to be added when the thermal power generating unit is constructed, and a complete thermal power generating unit model is shown in fig. 5.

Preferably, as shown in fig. 1, 2 and 3, the structure diagram of the single-region typical load frequency control of the present invention is shown in fig. 4.

Preferably, when the prime mover is a steam turbine, for the steam turbine, when the position of the air valve is changed, the output power of the steam turbine is also changed, so that the power of the generator is changed, and a first-order inertia link function is adopted:

The hydroelectric generating set is sensitive to frequency change, and is usually limited by a frequency modulation dead zone in order to avoid repeated starting and stopping of the hydroelectric generating set caused by fine frequency fluctuation; meanwhile, the hydraulic turbine speed regulator also comprises a transient frequency compensation part and a PID (proportion integration differentiation) regulation module to finish quick response to frequency change. In addition, the turbine also has a permanent slip coefficient which can affect the depth of primary frequency modulation.

The model of the hydroelectric generating set is shown in FIG. 6, b_pFor the permanent state slip coefficient, the transfer function of the differential module is

Because in practical application, pure differentiation is advanced control and the implementation difficulty is high, the formula is used for replacing a differentiation module;

preferably, when the prime mover is a water turbine, the transfer function of the water turbine is as follows in consideration of the influence of the water hammer effect:

in the formula T_wIs the water hammer time constant, which is typically 1.

Preferably, the transient frequency compensation part and the PID adjusting module are located in a speed regulator of a load frequency control structure of the hydroelectric generating set, the integral module for processing the permanent slip coefficient is located in a prime mover of the load frequency control structure of the hydroelectric generating set, and a dead zone of the speed regulator is set for the speed regulator of the load frequency control structure of the hydroelectric generating set.

The two-region alternating current/direct current water, fire and electricity combined frequency regulation model is established by integrating the models, as shown in fig. 7, and comprises a load frequency control structure of the thermal power generating unit and a load frequency control structure of the hydroelectric power generating unit, wherein the load frequency control structure of the thermal power generating unit and the load frequency control structure of the hydroelectric power generating unit are communicated through a connecting line and are connected to a direct current power transmission part to form the two-region alternating current/direct current water, fire and electricity combined frequency regulation model.

Preferably, when the prime mover of the load frequency control structure of the thermal power generating unit is a steam turbine, for the steam turbine, when the position of the air valve is changed, the output power of the steam turbine also changes, so that the power of the generator changes, and a first-order inertia link function is adopted as follows:

in the formula T_wIs the water hammer time constant, which is typically 1.

Preferably, the speed governor is: when the system load changes, the primary frequency modulation controller changes the valve through the inherent property of the speed regulator to change the input power of the prime motor;

Preferably, when the system load changes, the primary frequency modulation changes the valve through the inherent property of the speed regulator to change the input power of the prime motor, and the secondary frequency modulation changes the position of the valve of the speed regulator through the frequency regulator;

the transfer function involved in this process is:

where Δ F(s) is the frequency change of the system, Δ P_c(s) is the output of the controller, Δ X_B(s) is the amount of change in the position of the governor's valve; g_n(s) a transfer function for representing the speed governor, K_n、T_nRespectively static gain and time constant of speed regulator, R is the regulation of speed regulatorA difference coefficient.

Preferably, the interconnection line is simplified to

The direct current transmission part is simplified into a first-order inertia link

Wherein T is_DCIs the time constant of inertia.

Preferably, the adjusting method of the alternating current/direct current water/power-thermal-power combined frequency regulation model in the two regions of the rich water period is that the frequency dead zone range of the secondary speed regulator is adjusted to-0.003-0.003, the permanent state slip coefficient is selected to be adjusted to 0.06, the PID parameter of the speed regulator is adjusted to Kp-2 and Ki-0.2, the AGC parameter of the speed regulator is set to 0.7 for thermoelectricity, and the hydropower is 0.3;

and connecting the module of the hydroelectric generating set-single-region improved load frequency control structure and the module of the thermal generating set-single-region improved load frequency control structure by using a connecting line, and simultaneously adding a direct current transmission part to obtain the system of the two-region alternating current/direct current water/power/thermal power combined frequency regulation model. Preferably, as can be seen from the two-region ac/dc water-fire-electricity combined frequency modulation model, as shown in fig. 7, 3 total parameters affect the frequency modulation effect, namely, the parameters are the frequency modulation dead zone range of the speed regulator, the water turbine steady state slip coefficient and the PID parameter of the speed regulator. The effect of three parameters in frequency modulation was analyzed:

Parameter adjustment strategies under different operation modes:

the traditional thermal power generating unit gradually exposes a plurality of problems along with the development of a power system. Firstly, the characteristics of the thermal power generating unit, such as limited climbing speed and long start-stop time, determine that the effective regulating range is smaller and the regulating response time is longer when the thermal power generating unit regulates the load. Secondly, the large demand of the thermal power generating unit on the coal resources increases the power generation cost and reduces the economical efficiency of the system. However, the advantages of the thermal power generating unit are not ignored, the whole operation of the thermal power generating unit is very stable after the thermal power generating unit is normally started, the thermal power generating unit is not restricted by seasons, and the thermal power generating unit does not change along with the change of time or weather.

The hydroelectric generating set is widely concerned by the characteristics of high starting and stopping speed, flexible adjustment, capability of quickly responding to load change and wide adjustment range. However, the uncertainty of facing the hydraulic energy source is large, and the practical application of the hydraulic energy source is greatly influenced by the climate change and the terrain difference. Depending on the size of the water flow, a year can be divided into two parts: the rich water period and the dry water period.

Preferably, in view of the above problems, the operation mode of the cogeneration frequency modulation in the dry season is as follows:

Preferably, the adjustment strategy of the parameters of the withered water period is proposed as follows:

and (3) a water enriching period:

And (3) a dry period:

Preferably, in combination with a parameter adjustment strategy of the water, power and electricity combined frequency modulation in the rich and dry water period, the water, power and electricity combined frequency control action logic can be provided as follows:

Preferably, the frequency control response action logic refers to reasonable combination of time and capacity of frequency modulation tasks undertaken by each power plant during multi-energy combined frequency modulation. The design principle is as follows: the resources are fully utilized, the coal consumption is reduced, and the economical efficiency of a power grid is improved.

On the basis of the preferred embodiment, the adjustment strategy of the parameters in the dry and rough water season is subjected to simulation verification, and a water, fire and electricity combined frequency modulation model of two areas is subjected to simulation verification.

In the water-rich period, the hydroelectric band is operated under the base load, the thermal power plant undertakes more frequency modulation tasks, and in the aspect of parameter setting, a larger frequency modulation dead zone is adopted, namely, the dead zone is-0.003-0.003, a larger permanent state slip coefficient is 0.06, and PID parameters with stability as a target are adopted: kp is 2 and Ki is 0.2. The thermal power and the water power of AGC parameter distribution are 0.7 and 0.3 respectively.

When the load changes by 0.01p.u., the power change situation of the water-fire-electric generator set and the frequency change of the two areas are as follows:

as can be seen from FIG. 8, the thermal power fluctuation is larger and the water power fluctuation is smoother under the water-rich period parameters. Because the frequency modulation is mainly carried out by using thermal power and the frequency modulation effect of the thermal power is not ideal as that of the thermal power, as shown in fig. 9, the frequency can be adjusted without difference but the adjustment time is longer.

In another embodiment, in a dry season, the thermal power generating unit operates with the base load, the hydroelectric power generating unit is responsible for a main frequency modulation task, in the aspect of parameter setting, a frequency modulation dead zone is removed, a smaller permanent state slip coefficient is selected to be 0.01, and a PID (proportion integration differentiation) parameter tends to be rapid: kp is 5.6 and Ki is 1.2.

When the load changes by 0.01p.u., the change situation of the power of the hydro-thermal generator set and the frequency change of the two areas are as follows:

fig. 10 shows that the hydroelectric generating set bears the main frequency modulation task in the setting of the parameters of the dry season, the power fluctuation is large, and the thermal power generating set has stable power with the base load. It can be seen from a comparison of fig. 9 and 11 that the frequency of the hydroelectric generating set is modulated more rapidly.

In conclusion, the parameter changing strategy provided for the water, fire and electricity operation mode in the heavy water season can enable the water, fire and electricity generating set to adapt to the operation modes in different periods, and the frequency control effect is good.

In another embodiment, the simulation verification of the frequency response action logic is performed in combination with the above embodiments, and when the simulation is performed in MATLAB/simulink, the month judgment rich water period is first input to complete the setting of the frequency modulation parameters. In one year, the rich water period is 6 months to 10 months, the dry water period is 11 months to the next 5 months, according to the parameter modification strategy provided in the foregoing, when the input month is in the rich water period range, the water turbine adopts a larger frequency modulation dead zone of-0.003-0.003, a larger permanent state slip coefficient of 0.06 and a PID parameter (Kp is 2, Ki is 0.08) which aims at stability; when the month is in the range of the dry season, the turbine removes a frequency modulation dead zone, and adopts a small permanent slip coefficient of 0.03 and PID parameters (Kp is 5.6, Ki is 0.3) which aim at rapidity.

The capacity allocation of the secondary modulation needs to be determined according to the magnitude of the input load.

In the rich water period, the thermal power frequency modulation capability is weak, so that the load change of 0.1p.u. is taken as a limit. When the load change is less than 0.1p.u., the hydropower does not participate in secondary frequency modulation, and AGC coefficients of the thermal power generating unit and the hydroelectric generating unit are respectively kept to be 1 and 0. When the load is over the range, the hydropower participates in secondary frequency modulation after a period of time, the AGC coefficients of the initial thermal power generating unit and the hydropower generating unit are respectively 1 and 0, and after a period of time (after the load is changed for 20s), the AGC coefficients of the thermal power generating unit and the hydropower generating unit are respectively 0.7 and 0.3. In the dry season, the limit is positioned at 2p.u. due to the strong frequency modulation capability of the hydropower, if the load does not exceed the range, the AGC coefficients of the thermal power and the hydropower respectively become 0 and 1, and if the load changes greatly and exceeds the range, the AGC coefficients of the thermal power and the hydropower respectively become 0.5 and 0.5 after a period of time (same 20 s).

Therefore, before the Simulink simulation model is operated, the parameters can be updated and the specific control logic can be determined by operating the m file to input the month, the load size and the load adding time. The change of the participation of the hydroelectric generating set in the secondary frequency modulation in the simulation process is changed in a mode of combining a timer and a switch.

And (3) simulating the dry period action logic:

input for 2 months, load change is 0.05p.u., load is added at 10 s: as shown in fig. 12 and 13, the thermal power generating unit has small power fluctuation, the load is fixed, and the operation with the base load is favorable. In this case, the frequencies of the two regions are also well controlled.

Input for 2 months, load change is 5p.u., load is added at 10 s: as shown in fig. 14 and 15, because hydroelectric frequency modulation has a good effect, a thermal power generating unit can not be added to participate in secondary frequency modulation under a proper frequency modulation parameter when a large load changes. Therefore, the conclusion is drawn after the simulation is finished, and in the dry season, the thermal power generating unit does not need to frequently participate in secondary frequency modulation due to the strong frequency modulation capability of the hydro-power generating unit, so that the frequent increase and decrease of the load of the thermal power generating unit are avoided.

Performing logical simulation of actions in the full season:

input for 6 months, load change is 0.01p.u., load is added at 10 s: as shown in fig. 16 and 17, the hydroelectric power generating unit is stable at this time, and the aim of smoothing the power fluctuation due to the load bearing can be achieved. Because the load fluctuation is not large, the thermal power generating unit can complete the no-difference adjustment of the frequency.

Input for 6 months, load change is 0.5p.u., load is added at 10 s: as shown in fig. 18, since the frequency modulation performance of the thermal power generating unit is weak, the effect of the non-difference frequency modulation cannot be achieved or is achieved very slowly by only applying the adjustment of the thermal power generating unit under the condition that the original secondary frequency modulation parameters are not changed, and therefore, if the load fluctuation is too large, it is necessary to add the hydroelectric power generating unit to participate in the secondary frequency modulation after a period of time. At this time, the power change situation of the hydro-thermal electric generator set is as shown in fig. 19, and the hydro-thermal electric power in fig. 19 changes more after participating in the secondary frequency modulation. This is because the hydroelectric generating set is more suitable for bearing base load and the hydroelectric generating set is more suitable for frequency modulation work due to the essential characteristics. The purpose of saving energy and reducing cost is achieved by fully utilizing water resources and saving coal consumption from the perspective of economy and environmental protection, the essential characteristics of the water resources and the coal consumption cannot be changed, the requirement on power fluctuation of the water-gas-electric generator set can be met by the parameter setting strategy provided by the simulation curve, and meanwhile, the frequency can be guaranteed to be well controlled. The parameter adjustment strategy considering the withered water period can promote the improvement of the economy of the power grid and the more reasonable utilization of energy.

As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. The load frequency control structure of the thermal power generating unit is characterized by comprising a speed regulator, a prime motor, a generator load model, a load frequency controller, a speed limiter and a time delay module;

2. The load frequency control structure of the thermal power generating unit according to claim 1, wherein when the prime mover is a steam turbine, for the steam turbine, when the position of the gas valve is changed, the output power of the steam turbine is also changed, which further causes the power of the generator to change, and a first-order inertia element function is adopted as:

3. The load frequency control structure of the hydroelectric generating set is characterized by comprising a speed regulator, a prime motor, a generator load model, a load frequency controller, a transient frequency compensation part, a PID (proportion integration differentiation) adjusting module and an integral module for processing a permanent slip coefficient, wherein the load frequency control structure of the hydroelectric generating set further comprises a frequency dead zone for setting the speed regulator;

4. The load frequency control structure of a hydroelectric generating set according to claim 3, wherein when the prime mover is a water turbine, the transfer function of the water turbine is as follows in consideration of the influence of the water hammer effect:

in the formula T_wIs the water hammer time constant, which is typically 1.

5. The load frequency control structure of a hydroelectric generating set according to claim 3, wherein the transient frequency compensation portion and the PID adjustment module are located in a speed regulator of the load frequency control structure of the hydroelectric generating set, and the integral module for processing the transient slip coefficient is located in a prime mover of the load frequency control structure of the hydroelectric generating set, and a dead zone of the speed regulator is provided for the speed regulator of the load frequency control structure of the hydroelectric generating set.

6. The two-region alternating current/direct current/water/fire/electricity combined frequency regulation model is characterized by comprising a load frequency control structure of a thermal power generating unit according to any one of claims 1 to 2 and a load frequency control structure of a hydroelectric power generating unit according to any one of claims 3 to 5, wherein the load frequency control structure of the thermal power generating unit and the load frequency control structure of the hydroelectric power generating unit are communicated through a connecting line and connected into a direct current transmission part to form the two-region alternating current/water/fire/electricity combined frequency regulation model.

7. The two-region alternating current-direct current-water-fire-electricity combined frequency modulation model of claim 6, wherein:

when the system load changes, the primary frequency modulation changes the valve through the inherent property of the speed regulator to change the input power of the prime motor, and the secondary frequency modulation changes the position of the air valve of the speed regulator through the frequency regulator;

the transfer function involved in this process is:

8. The two-region alternating current-direct current-water-fire-electricity combined frequency modulation model of claim 6, wherein:

the connecting line is simplified into

The direct current transmission part is simplified into a first-order inertia linkWherein T is_DCIs the time constant of inertia.

9. The frequency modulation method by using the two-region alternating current/direct current/water/fire/electricity combined frequency modulation model according to any one of claims 6 to 8, characterized by comprising the following steps:

in the water-rich period, parameters of speed regulators in a hydroelectric generating set load frequency control structure and a thermal power generating set load frequency control structure are set, and a frequency dead zone range and a permanent state slip coefficient of the hydroelectric generating set load frequency control structure are set, so that when the hydroelectric generating set and the thermal power generating set jointly run, the generating frequency generated by the hydroelectric generating set forms a main frequency modulation baseband item, the hydroelectric generating set serves as auxiliary frequency modulation, and the thermal power generating set serves as main frequency modulation.

10. The method according to claim 9, wherein the setting of the parameters of the speed regulators in the hydroelectric generating set load frequency control structure and the thermal generating set load frequency control structure, and the setting of the frequency dead zone range and the permanent mode slip coefficient of the hydroelectric generating set load frequency control structure comprise: the frequency dead zone range of adjusting the secondary speed regulator is-0.003-0.003, selects the adjustment of permanent slip coefficient is 0.06, the PID parameter adjustment of speed regulator is Kp 2, Ki 0.2, the AGC parameter setting of speed regulator is thermal power 0.7, and water and electricity is 0.3.

11. The frequency modulation method by using the two-region alternating current/direct current/water/fire/electricity combined frequency modulation model according to any one of claims 6 to 8, characterized by comprising the following steps:

in the dry season, parameters of speed regulators in a hydroelectric generating set load frequency control structure and a thermal power generating set load frequency control structure are set, and a frequency dead zone of the hydroelectric generating set load frequency control structure is removed, so that when the hydroelectric generating set and the thermal power generating set jointly run, the generating frequency generated by the thermal power generating set forms a main frequency modulation baseband item, the thermal power generating set serves as auxiliary frequency modulation, and the hydroelectric generating set serves as main frequency modulation.

12. The method for modulating the frequency of the two-region alternating current/direct current/water/fire/electricity combined frequency modulation model according to claim 11, wherein the steps of setting parameters of speed regulators in a hydroelectric generating set load frequency control structure and a thermal generating set load frequency control structure and removing a frequency dead zone of the hydroelectric generating set load frequency control structure comprise: removing a frequency dead zone of the secondary speed regulator, selecting a permanent state slip coefficient to be 0.01, wherein the PID parameters of the speed regulator are as follows: kp is 5.6 and Ki is 1.2.

13. The method for constructing the two-region alternating current-direct current water-fire-electricity combined frequency modulation model is characterized by comprising the following steps of:

14. A system of a two-region alternating current-direct current water-fire-electricity combined frequency modulation model is characterized in that,

respectively building a module of a thermal power generating unit-single-region typical load frequency control structure and a module of a hydroelectric generating unit-single-region typical load frequency control structure by using a speed regulator, a prime motor, a generator load model and a load frequency controller;