CN118336791A - A frequency regulation control system for thermal power units using cluster electric vehicles for assistance - Google Patents

Abstract

The invention belongs to the technical field of thermal power generating unit frequency modulation control systems, and particularly provides a thermal power generating unit frequency modulation control system assisted by a clustered electric vehicle. The central control unit receives and processes the real-time working state and performance data of the thermal power generating unit and the AEV provided by the state monitoring module, and generates a corresponding frequency modulation instruction; the double-layer MPC controller optimizes and processes the frequency modulation instruction, so that the system can ensure the frequency adjustment precision and response speed while achieving the best economic benefit; the variable-mode decomposition VMD processing module decomposes the original frequency modulation signal into different frequency components, and the thermal power unit and the AEV respectively respond to the low-frequency component and the high-frequency component to realize accurate and efficient response to the frequency modulation requirement; when the total adjustable power of the thermal power generating unit and the AEV can not meet the frequency modulation requirement, the tie line control module can perform energy interaction with other areas to finish frequency modulation. The system effectively improves the frequency modulation effect of the thermal power generating unit, optimizes the economy and stability of the power system, and simultaneously provides a flexible and efficient frequency modulation strategy for the power system.

Description

A frequency regulation control system for thermal power units using cluster electric vehicles for assistance

Technical Field

The invention belongs to the technical field of frequency regulation control systems for thermal power generation units, and specifically provides a frequency regulation control system for thermal power generation units assisted by cluster electric vehicles.

Background technique

With the large-scale grid connection of intermittent renewable energy sources such as wind power and photovoltaic power, the frequency fluctuation of the power grid has increased. The system needs to reserve more frequency regulation reserve capacity, which is not conducive to the economic operation of the power grid. The frequency regulation of traditional thermal power units has problems such as slow regulation speed, low accuracy, and easy wear of equipment, which makes it difficult to meet the frequency stability requirements of new power systems. In recent years, the development of energy storage technology has made it possible for the power grid to provide frequency regulation auxiliary services, but problems such as large initial investment and difficult later maintenance are also difficult to avoid.

Compared with energy storage systems, cluster electric vehicles (AEVs) as a demand-side resource are convenient and flexible, have great adjustable potential, and respond quickly, making them a new way to alleviate the pressure of power system frequency regulation. However, in traditional power system load frequency control (LFC), there are many studies on applying model predictive control (MPC) to energy storage systems or wind-storage combined systems, but few are used for AEV frequency control, and most use conventional MPC, which often ignores the economic cost of frequency regulation.

Therefore, there is an urgent need for a frequency regulation control system for thermal power units that takes into account both the economy and dynamic performance of frequency regulation.

Summary of the invention

The present invention aims to solve at least one of the technical problems existing in the prior art and provide a frequency regulation control system for a thermal power unit assisted by cluster electric vehicles.

To achieve the above object, the technical solution proposed by the present invention is as follows:

A frequency regulation control system for a thermal power unit assisted by a cluster of electric vehicles, comprising:

An AEV cluster module, which includes multiple AEVs with battery energy storage systems and wireless communication modules for sending energy storage information to a central control unit and receiving frequency modulation control commands;

A central control unit is connected to the AEV cluster module, the central control unit, the double-layer MPC controller, the variational mode decomposition VMD processing module, the tie line control module and the state monitoring module, and is used to receive and process the power demand information from the thermal power unit and the energy storage information of the AEV cluster to determine the charging/discharging strategy of the AEV cluster and send a control command to the AEV cluster;

A variational mode decomposition (VMD) processing module is connected to the central control unit and is used to decompose and integrate the original frequency modulation signal into signals with different frequency components and send them to the double-layer MPC controller;

The two-layer MPC controller is connected to the central control unit. The upper layer controller is an economic model predictive control EMPC controller, which is used to achieve economic optimization and power balance; the lower layer controller is a model predictive control MPC controller, which is used to achieve active power balance and frequency stability.

The interconnection line control module is connected to the central control unit and is responsible for energy interaction with other areas through the interconnection line to complete frequency regulation when the total adjustable power of the thermal power unit and AEV cannot meet the frequency regulation requirements;

The status monitoring module is connected to the central control unit and is used to monitor the working status and performance of the thermal power unit and AEV in real time, and provide this information to the central control unit so that the central control unit can perform data analysis and decision-making.

A further improvement of the present invention is that the AEV cluster is formed by aggregating electric vehicle clusters with similar characteristic parameters of charging power, charging efficiency and battery capacity.

A further improvement of the present invention is that the variational mode decomposition (VMD) processing module decomposes and integrates the original frequency modulation signal into signals of different frequency components through VDM processing, the low-frequency part is responded by the thermal power unit, and the high-frequency part is responded by the AEV.

A further improvement of the present invention is that the VDM in the VDM processing module is an adaptive, completely non-recursive signal processing method, which decomposes the frequency modulated signal into Z sub-components with different frequencies, and the sum of the estimated bandwidths of the sub-components is minimized. The constraint condition is that the sum of the components is equal to the original frequency modulation instruction, and the corresponding constrained variational problem is constructed as follows:

in, is the gradient operation; δ(t) is the unit pulse function; _Hz , are the zth modal component and its center frequency respectively; Z is the number of decomposed intrinsic mode functions; f is the frequency modulation command signal;

The VDM process decomposes the original frequency modulation command signal into Z IMF components with different frequencies, and integrates the low-frequency components as the response command of the thermal power unit. High frequency components as corresponding instructions for AEV

The power constraint is:

Among them, z _l is the critical value of high and low frequency components, and the selection principle is to bear as many high frequency components as possible within the total adjustable power range of AEV; are the upper and lower limits of the adjustable power of the thermal power unit at time t, They are the upper and lower limits of the adjustable power of AEV at time t respectively;

When the adjustable power of thermal power units and AEVs meets their respective frequency regulation needs, the thermal power units and AEVs track their respective frequency regulation signals; but when the frequency regulation capacity of one of them is insufficient, the other frequency regulation resource will bear the corresponding under-regulation part.

A further improvement of the present invention is that the upper EMPC controller of the double-layer MPC controller redistributes instructions, coordinates the output of multiple units in the region, and achieves economic optimization and power balance.

A further improvement of the present invention is that the upper EMPC controller decomposes the high and low frequency signals obtained by VDM to obtain the original frequency modulation command signal. According to the economic indicators and related constraints of each resource, the frequency modulation instructions are further allocated to obtain the optimal tracking instructions for each unit.

A further improvement of the present invention is that the model constructed by the EMPC needs to take into account the power generation cost of the thermal power unit and the AEV regulation cost;

The power generation cost λ _g,i (P _g,i (k)) of the thermal power unit includes coal consumption and CO ₂ emissions. The AEV is an adjustable load, and the adjustment cost λ _ev,j (P _ev,j (k)) includes battery loss and electricity cost for interaction with the grid. Both cost functions can be described as quadratic functions;

Wherein, P _g,i (k) is the initial power value of thermal power unit i, and P _ev,i (k) is the initial power value of frequency modulation unit j;

The economic performance index σ(k) of the system at time k is:

Then the total optimization objective function J(k) of the system at time k is:

Among them, the first item is the cost item, the purpose is to reduce the regulation cost; the two square items are error items, the purpose is to ensure that the thermal power unit and AEV can better track their respective frequency regulation instructions. It is the maximum ramp time of the unit, and its purpose is to speed up the overall regulation speed of the system.

A further improvement of the present invention is that the lower-layer MPC controller of the double-layer MPC controller is a dynamic control layer, which controls each unit according to the power allocation result obtained in the upper layer to achieve active power balance and frequency stability.

A further improvement of the present invention is that, when the total adjustable power of the thermal power units and AEVs cannot meet the frequency regulation requirements, the area must exchange energy with other areas through the interconnection lines to complete the frequency regulation because local power balance cannot be achieved.

The present invention has at least the following beneficial technical effects:

1. The present invention decomposes the original frequency modulation signal into components of different frequencies through the variational mode decomposition (VMD) module, so that the cluster electric vehicle (AEV) and the thermal power unit can accurately respond to the high-frequency component and the low-frequency component respectively. This differentiated control strategy can give full play to the rapid response and regulation advantages of AEV, optimize the utilization efficiency of different frequency modulation entities, and thus greatly improve the stability of the power grid and the frequency regulation accuracy.

2. The present invention uses a double-layer MPC controller. The upper layer can optimize the steady-state economic set value through economic model predictive control (EMPC), and the lower layer can achieve dynamic frequency optimization control through MPC, thereby realizing the step-by-step progression of economic optimization and dynamic control, and can improve the economic benefits of the system.

3. When the total adjustable power of the thermal power units and AEVs cannot meet the frequency regulation requirements, the present invention can ensure the stable operation of the power grid and improve the frequency regulation capability of the system by performing energy interaction with other areas through the interconnection line control module.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a structural diagram of a frequency modulation control system for a thermal power unit assisted by cluster electric vehicles provided by the present invention;

FIG2 is a control flow chart of a frequency regulation control system of a thermal power unit assisted by cluster electric vehicles provided by the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

Example:

As shown in FIG1 , a frequency regulation control system of a thermal power unit using cluster electric vehicles as an aid is provided in an embodiment of the present invention as follows:

1. AEV cluster module, connected to the central control unit, which includes multiple AEVs with battery energy storage systems and wireless communication modules, used to send energy storage information to the central control unit and receive frequency modulation control commands;

2. The central control unit is connected to the AEV cluster module, the central control unit, the double-layer MPC controller, the variational mode decomposition VMD processing module, the tie line control module, and the state monitoring module, and is used to receive and process the power demand information from the thermal power unit and the energy storage information of the AEV cluster to determine the charging/discharging strategy of the AEV cluster and send control commands to the AEV cluster;

3. The variational mode decomposition (VMD) processing module is connected to the central control unit and is used to decompose and integrate the original frequency modulation signal into signals of different frequency components; the original frequency modulation signal is decomposed and integrated into signals of different frequency components through VDM processing, the low frequency part is responded by the thermal power unit, and the high frequency part is responded by the AEV;

4. A two-layer MPC controller is connected to the central control unit. The upper layer controller is an economic model predictive control (EMPC) controller, which is used to achieve economic optimization and power balance; the lower layer controller is a model predictive control (MPC) controller, which is used to achieve active power balance and frequency stability;

5. The interconnection line control module is connected to the central control unit and is responsible for energy interaction with other areas through the interconnection line to complete frequency regulation when the total adjustable power of the thermal power units and AEVs cannot meet the frequency regulation requirements.

6. The status monitoring module is connected to the central control unit and is used to monitor the working status and performance of the thermal power unit and AEV in real time, and provide this information to the central control unit so that the central control unit can perform data analysis and decision-making;

As shown in FIG. 1 and FIG. 2 , a VDM processing module of a frequency modulation control system of a thermal power unit assisted by a cluster electric vehicle provided in an embodiment of the present invention decomposes the frequency modulation signal into Z sub-components with different frequencies, and the sum of the estimated bandwidths of the sub-components is minimized. The constraint condition is that the sum of the components is equal to the original frequency modulation instruction. Then the corresponding constrained variational problem is constructed as follows:

in, is the gradient operation; δ(t) is the unit pulse function; _Hz , are the zth modal component and its center frequency respectively; Z is the number of decomposed intrinsic mode functions (IMFs); and f is the frequency modulation command signal.

The VDM process decomposes the original frequency modulation command signal into Z IMF components with different frequencies, and integrates the low-frequency components as the response command of the thermal power unit. High frequency components as corresponding instructions for AEV

The power constraint is:

Among them, z _l is the critical value of high and low frequency components, and the selection principle is to bear as many high frequency components as possible within the total adjustable power range of AEV; are the upper and lower limits of the adjustable power of the thermal power unit at time t, are the upper and lower limits of the adjustable power of AEV at time t respectively.

When the adjustable power of the thermal power unit and AEV meets their respective frequency regulation requirements, the thermal power unit and AEV track their respective frequency regulation signals;

When the frequency modulation capacity of one of them is insufficient, the other frequency modulation resource will bear the corresponding shortfall;

When the total adjustable power of thermal power units and AEVs cannot meet the frequency regulation requirements, since local power balance cannot be achieved, the area must exchange energy with other areas through interconnection lines to complete frequency regulation.

As shown in Figure 2, the upper EMPC controller of the two-layer MPC controller redistributes commands and coordinates the output of multiple units in the region to achieve economic optimization and power balance. The EMPC controller decomposes the high and low frequency signals obtained by VDM to obtain the original frequency modulation command signal. According to the economic indicators and related constraints of each resource, the frequency modulation instructions are further distributed to obtain the optimal tracking instructions for each unit;

The model constructed by the EMPC needs to consider the power generation cost of the thermal power unit and the AEV regulation cost;

The power generation cost λ _g,i (P _g,i (k)) of the thermal power unit mainly includes coal consumption and CO ₂ emissions. The AEV, as an adjustable load, has an adjustment cost λ _ev,j (P _ev,j (k)), which mainly includes battery loss and electricity cost for interaction with the grid. Both cost functions can be described as quadratic functions.

Among them, P _g,i (k) is the initial power value of thermal power unit i, and P _ev,i (k) is the initial power value of frequency modulation unit j.

The economic performance index σ(k) of the system at time k is:

Then the total optimization objective function J(k) of the system at time k is:

Among them, the first item is the cost item, the purpose is to reduce the regulation cost; the two square items are error items, the purpose is to ensure that the thermal power unit and AEV can better track their respective frequency regulation instructions. It is the maximum ramp time of the unit, and its purpose is to speed up the overall regulation speed of the system.

The lower-layer MPC controller of the double-layer MPC controller is a dynamic control layer, which controls each unit according to the power allocation result obtained in the upper layer to achieve active power balance and frequency stability.

In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present invention belong.

Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims (9)

1. Use thermal power generating unit frequency modulation control system of cluster electric automobile assistance, characterized in that includes:

the AEV cluster module comprises a plurality of AEVs with battery energy storage systems and wireless communication modules, and is used for sending energy storage information to the central control unit and receiving frequency modulation control commands;

The central control unit is connected with the AEV cluster module, the central control unit, the double-layer MPC controller, the variation modal decomposition VMD processing module, the tie line control module and the state monitoring module, and is used for receiving and processing the power demand information from the thermal power generating unit and the energy storage information of the AEV cluster so as to determine the charging/discharging strategy of the AEV cluster and sending a control command to the AEV cluster;

the variable mode decomposition VMD processing module is connected with the central control unit and is used for decomposing and integrating the original frequency modulation signals into signals with different frequency components and sending the signals to the double-layer MPC controller;

The double-layer MPC controller is connected with the central control unit, and the upper-layer controller is an economic model prediction control EMPC controller and is used for realizing economic optimization and power balance; the lower controller is a Model Predictive Control (MPC) controller and is used for realizing active power balance and frequency stabilization;

The tie line control module is connected with the central control unit and is responsible for carrying out energy interaction with other areas through the tie line to finish frequency modulation when the total adjustable power of the thermal power unit and the AEV can not meet the frequency modulation requirement;

The state monitoring module is connected with the central control unit and used for monitoring the working states and performances of the thermal power generating unit and the AEV in real time and providing the information to the central control unit so that the central control unit can conduct data analysis and decision.

2. The thermal power generating unit frequency modulation control system assisted by clustered electric vehicles according to claim 1, wherein the AEV cluster is formed by aggregation of electric vehicle clusters with similar charging power, charging efficiency and battery capacity characteristic parameters.

3. The thermal power generating unit frequency modulation control system assisted by the clustered electric vehicles according to claim 1, wherein the variable mode decomposition VMD processing module decomposes and integrates the original frequency modulation signals into signals with different frequency components through VDM processing, the low-frequency part is responded by the thermal power generating unit, and the high-frequency part is responded by the AEV.

4. A thermal power generating unit fm control system using clustered electric vehicle assistance as claimed in claim 3, wherein VDM in the VDM processing module is an adaptive, completely non-recursive signal processing method, the fm signal is decomposed into Z sub-components with different frequencies, and the sum of the estimated bandwidths of the sub-components is minimum, and if the constraint condition is that the sum of the components is equal to the original fm command, the corresponding constraint variation problem is constructed as follows:

Wherein, Is gradient operation; delta (t) is a unit pulse function; h _z,The z-th modal component and its center frequency, respectively; z is the number of the decomposed eigenmode functions; f is a frequency modulation instruction signal;

the VDM processing is used for decomposing an original frequency modulation instruction signal into Z IMF components with different frequencies, and integrating low-frequency components in the IMF components to be used as response instructions of the thermal power generating unit High frequency component as corresponding instruction for AEV

The power constraint is:

Wherein z _l is the critical value of the high and low frequency components, and the selection principle is that the high frequency components are born as much as possible in the total adjustable power range of AEV; respectively an upper limit and a lower limit of adjustable power of the thermal power generating unit at the moment t, The upper limit and the lower limit of the AEV adjustable power at the moment t are respectively;

When the adjustable power of the thermal power unit and the AEV meet respective frequency modulation requirements, the thermal power unit and the AEV track respective frequency modulation signals; however, when one of the frequency modulation capabilities is insufficient, the other frequency modulation resource is used for bearing the corresponding undershoot part.

5. The thermal power generating unit frequency modulation control system assisted by clustered electric vehicles according to claim 1, wherein an upper EMPC controller of the double-layer MPC controller redistributes instructions, coordinates multi-unit output in an area and realizes economic optimization and power balance.

6. The thermal power generating unit frequency modulation control system assisted by clustered electric vehicles as set forth in claim 5, wherein said upper-layer EMPC controller generates high and low frequency signals obtained by decomposing original frequency modulation command signals by VDMAnd further distributing the frequency modulation instruction according to the economic index and the related constraint of each resource to obtain the optimal tracking instruction of each unit.

7. The thermal power generating unit frequency modulation control system assisted by the clustered electric vehicles according to claim 5, wherein the model constructed by the EMPC needs to consider the generating cost and the AEV adjusting cost of the thermal power generating unit;

the thermal power generating unit power generation cost lambda _g,i(P_g,i (k)) comprises coal consumption and CO ₂ emission, the AEV is used as an adjustable load, the adjustment cost lambda _ev,j(P_ev,j (k)) comprises battery loss and electric charge cost for interaction with a power grid, and the two cost functions can be described as quadratic functions;

Wherein, P _g,i (k) is the initial power value of the thermal power unit i, and P _ev,i (k) is the initial power value of the frequency modulation unit j;

The economic index sigma (k) of the system at the moment k is:

The overall optimization objective function J (k) of the system at time k is:

Wherein the first term is a cost term with the aim of reducing the adjustment cost; 2 square terms are error terms, so as to ensure that the thermal power unit and the AEV can track respective frequency modulation instructions better, The maximum climbing time of the machine set is aimed at accelerating the overall regulating speed of the system.

8. The thermal power generating unit frequency modulation control system assisted by using a clustered electric vehicle as set forth in claim 5, wherein the lower MPC controller of the dual-layer MPC controller is a dynamic control layer, and is configured to control each unit according to the power distribution result obtained from the upper layer, so as to realize active power balance and frequency stabilization.

9. The thermal power generating unit frequency modulation control system assisted by using a clustered electric vehicle as claimed in claim 1, wherein the link control module performs energy interaction with other areas through a link to complete frequency modulation when the total adjustable power of the thermal power generating unit and the AEV cannot meet the frequency modulation requirement due to the fact that local power balance cannot be achieved.