Thermal power generating unit-energy storage coupling frequency modulation system for improving frequency stability of power grid

Abstract

The invention relates to the technical field of power system frequency, and discloses a thermal power generating unit-energy storage coupling frequency modulation system for improving power grid frequency stability, which comprises a thermal power generating unit module, an energy storage system module, an energy management and distribution control module and a communication and monitoring module. The thermal power generating unit provides a frequency stabilization basis through inertia response and power regulation, and the energy storage system compensates frequency deviation in a quick response mode. And the energy management module dynamically adjusts the power distribution proportion between the thermal power generating unit and the energy storage system based on the optimized objective function to realize efficient collaborative frequency modulation. The output power and the state of charge of the energy storage system are controlled by constraint conditions. The communication and monitoring module collects power grid frequency, load fluctuation and energy storage state data in real time, generates frequency modulation control signals and issues the frequency modulation control signals to each module. By combining the stability of the thermal power generating unit and the quick response characteristic of the energy storage system, the response speed and the adjustment precision of power grid frequency adjustment are remarkably improved, and meanwhile the frequency adjustment cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power system frequency regulation, and in particular to a thermal power unit-energy storage coupling frequency regulation system for improving power grid frequency stability. Background Art

[0002] With the large-scale access of renewable energy, especially the rapid development of intermittent energy such as wind and solar energy, the frequency stability problem of the power grid has become increasingly prominent. The traditional power system is based on large-scale thermal power units, which have large rotational inertia and stable output power. Therefore, for a long time in the past, the frequency regulation of the power grid mainly relied on thermal power units. However, with the continuous increase in the proportion of new energy power generation, this traditional frequency regulation mode has gradually exposed the following problems and shortcomings: The main frequency regulation methods of thermal power units are primary frequency regulation and secondary frequency regulation. On the one hand, primary frequency regulation depends on the rotational inertia of the unit, and its frequency regulation response has a certain time lag, which usually cannot quickly meet the sudden fluctuations in the grid frequency. On the other hand, secondary frequency regulation is mainly achieved by adjusting the output power of the thermal power unit, and the regulation speed is limited by the ramp rate of the unit (usually at the MW / s level), which cannot cope with the rapid load changes caused by the fluctuations of new energy. Therefore, thermal power units have obvious deficiencies in rapid frequency regulation.

[0003] Renewable energy generation (such as wind power and photovoltaic power) has strong volatility and intermittency because its output power is significantly affected by meteorological conditions. When the proportion of new energy access is high, the dynamic change amplitude of the grid load increases, and the frequency and amplitude of frequency deviation increase significantly. However, the new energy itself lacks inertia support and cannot directly participate in the inertial response and primary frequency regulation of the grid, which further exacerbates the challenge of grid frequency stability.

[0004] Energy storage systems (such as lithium-ion batteries, flywheel energy storage, etc.) can effectively make up for the shortcomings of thermal power units in rapid frequency regulation due to their fast response characteristics. However, the initial investment cost of energy storage systems is high, and they are easily affected by frequent power changes in long-term operation. In addition, the energy capacity and power output of energy storage systems are limited, making it difficult to take into account high power and long-term regulation requirements when used alone. Therefore, relying solely on energy storage systems is not an economically feasible solution.

[0005] Although the coordinated frequency regulation scheme of thermal power units and energy storage systems has gradually attracted attention, the existing technology still has shortcomings in the following aspects: Optimization problem of power allocation strategy: How to reasonably allocate power between thermal power units and energy storage systems to take into account response speed, frequency regulation accuracy and operating costs is a difficulty of current technology.

[0006] Dynamic response characteristic matching: Thermal power units have a slow response speed, while energy storage systems can respond quickly. There are significant differences in the dynamic characteristics of the two, and there is still a lack of mature solutions for how to achieve efficient dynamic coordinated control.

[0007] Economy and stability in long-term operation: During coordinated frequency regulation, how to reduce the frequent start and stop of the energy storage system to extend its service life while avoiding the efficiency reduction and wear problems caused by frequent adjustment of thermal power units remains a challenge to be solved.

[0008] The coordinated frequency regulation system needs to collect and process various data such as grid frequency, thermal power unit output power, energy storage status, etc. in real time, and transmit control signals through communication modules. However, the existing communication and monitoring systems may be insufficient in terms of real-time performance and accuracy, especially when sudden fluctuations occur in the grid, delays and errors may cause the frequency regulation effect to be impaired.

[0009] In summary, the existing frequency regulation technology has many deficiencies in terms of rapid response capability, economy and coordinated control strategy, and cannot fully meet the frequency stability requirements of high-proportion access to the power grid for new energy. Therefore, there is an urgent need for an innovative technology for coordinated frequency regulation of thermal power units and energy storage systems, which can give full play to the stability of thermal power units and the rapid response characteristics of energy storage systems, solve outstanding problems in current technologies, and achieve more efficient, economical and stable frequency regulation.

[0010] Therefore, we urgently need to design a thermal power unit-energy storage coupled frequency modulation system to improve the frequency stability of the power grid to solve the above problems. Summary of the invention

[0011] The purpose of the present invention is to solve the prior art problems raised in the above background technology and to provide a thermal power generation unit-energy storage coupling frequency modulation system for improving the frequency stability of the power grid.

[0012] The above-mentioned purpose of the present invention is achieved like this: The solution of the present invention provides a thermal power unit-energy storage coupling frequency modulation system for improving the frequency stability of the power grid, including the following modules: Thermal power unit frequency regulation module: Provides basic frequency regulation capability through thermal power units, and its output power The following dynamic equations are satisfied: ; in, For thermal power units at time Output power at the moment, in MW; is the initial output power of the thermal power unit, in MW; is the maximum power ramp rate of the thermal power unit, in MW / s; is the control signal of the thermal power unit, ranging from [0,1]; Energy storage system module: including battery energy storage or flywheel energy storage system, whose output power and state of charge The following dynamic equations and constraints are satisfied: ; ; , ; in, For energy storage system in time Output power at the moment, in MW; is the control signal of the energy storage system, ranging from [0,1]; is the state of charge of the energy storage system, in MWh; is the initial charge state; , They are the minimum and maximum state of charge limits of the energy storage system respectively; is the maximum power output of the energy storage system, in MW; Energy management and distribution control module: according to the grid frequency deviation Dynamically adjust the output power of thermal power units and energy storage systems to meet the following power balance equation: ; in, is the deviation between grid load power and power generation power, in MW; is the grid frequency deviation, unit: Hz; Communication and monitoring module: used to monitor grid frequency fluctuations, energy storage status and thermal power unit operation status, and transmit control signals , .

[0013] On the other hand, the energy management and distribution control module is based on the optimization objective function The power distribution of thermal power units and energy storage systems is controlled, and the objective function is: ; in, is the total system operating cost, unit MW 2 ·s; The time period for optimizing frequency modulation, in seconds; and are the power penalty coefficients of thermal power units and energy storage systems, both are dimensionless; It is the grid frequency deviation, in Hz.

[0014] On the other hand, thermal power units are Output power at the moment The following dynamic constraints are met: ; in, is the maximum power ramp rate of the thermal power unit, in MW / s; It is the power change rate of thermal power unit, in MW / s.

[0015] On the other hand, the output power of the energy storage system at a certain time The following dynamic constraints are met: ; in, The maximum power output of the energy storage system, in MW.

[0016] On the other hand, the state of charge of the energy storage system The following constraints are met: ; in, For energy storage system in time The state of charge at the moment, in MWh; is the minimum state of charge of the energy storage system, in MWh; It is the maximum state of charge of the energy storage system, in MWh.

[0017] On the other hand, the power allocation ratio of thermal power units and energy storage systems is determined by the optimization variable Determine that the following power allocation equation is satisfied: ; in, For thermal power units at time Output power at the moment, in MW; For energy storage system in time Output power at the moment, in MW; is the deviation between the grid load power and the generated power, in MW; is the power allocation ratio coefficient, ranging from [0,1], dimensionless, and represents the proportion of thermal power units in power allocation.

[0018] On the other hand, optimizing variables The following iteration formula is satisfied: ; in, is the power allocation ratio coefficient at the next moment, ranging from [0,1], dimensionless; is the power allocation ratio coefficient at the current moment, ranging from [0,1], dimensionless; is the learning rate, which indicates the step size of iterative optimization and is dimensionless; is the objective function right The partial derivative of 2 ; It is the system optimization objective function, which represents the comprehensive index of frequency deviation and power cost, and the unit is MW 2 ·s.

[0019] On the other hand, the grid frequency deviation Satisfies the following dynamic change equation: ; in, For the power grid in time The frequency deviation at the moment, in Hz; is the time derivative of the frequency deviation, in Hz / s; is the grid time constant, which indicates the time characteristic of frequency regulation response, in seconds; is the grid inertia constant, which indicates the grid's inertial anti-disturbance capability to frequency changes, and its unit is MW·S 2 / Hz; It is the deviation between grid load power and power generation power, in MW.

[0020] On the other hand, the final response of the frequency deviation satisfies the following closed-loop control formula: ; in, For the power grid in time The frequency deviation at the moment, in Hz; is the frequency deviation of the power grid at the initial moment, in Hz; is the grid time constant, which indicates the time characteristic of frequency regulation response, in seconds; is the grid inertia constant, which indicates the grid's inertial anti-disturbance capability to frequency changes, and its unit is MW·S 2 / Hz; is the current moment, in seconds; is the integral variable, which represents the intermediate variable of time integration, and its unit is s; For time Load power deviation at the moment, in MW; On the other hand, the energy management and distribution control module adopts the model predictive control algorithm to , Energy storage system charge state and frequency deviation Optimize power distribution.

[0021] The present invention also provides a thermal power unit-energy storage coupling frequency modulation method for improving the frequency stability of the power grid, and the specific steps include: Real-time monitoring of grid frequency deviation and power deviation ,Right now: ; Optimizing the calculation of power distribution of thermal power units And energy storage system output ; Generate control signals and And sent to thermal power units and energy storage systems; Feedback closed loop control, adjust power output until frequency deviation Converge to the target range.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses the coordinated frequency regulation of thermal power units and energy storage systems. The technical solution combines the stable inertial response of thermal power units with the rapid dynamic regulation capability of energy storage systems. When frequency fluctuations occur, the energy storage system can respond quickly to achieve timely compensation for frequency deviations. At the same time, thermal power units gradually take over the regulation tasks to provide continuous power support. This synergistic mechanism significantly improves the response speed and regulation accuracy of grid frequency regulation, and effectively copes with frequency disturbances caused by fluctuations in new energy sources. 2. The technology of the present invention rationally distributes power output tasks between thermal power units and energy storage systems through optimized energy management strategies, which not only reduces the impact of frequent start and stop of energy storage systems on their lifespan, but also avoids the problems of reduced efficiency and wear caused by over-regulation of thermal power units; the dynamic adjustment of power distribution takes into account both rapid response and economic operation, enabling the system to significantly reduce frequency regulation costs while meeting frequency stability requirements; 3. The technology of the present invention solves the problem that traditional frequency modulation methods cannot cope with the volatility of new energy, and realizes the organic combination of grid frequency stability and flexibility through coordinated frequency modulation; especially in the scenario of large-scale access of new energy, this technology can effectively absorb the volatility characteristics of new energy and ensure the stable operation of grid frequency, while providing technical support for building a green smart grid with a high proportion of renewable energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 The system block diagram of a thermal power generation unit-energy storage coupling frequency modulation system for improving the frequency stability of a power grid according to the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The following is combined with Figure 1 The specific embodiments of the present invention are described in detail with reference to the accompanying drawings and examples.

[0027] The solution of the embodiment of the present invention is a thermal power generation unit-energy storage coupling frequency modulation system for improving the frequency stability of the power grid, including the following modules: 1. Thermal power unit module: Thermal power units are based on frequency deviation and load deviation Dynamically adjust output power , the control signal is , satisfying the following dynamic formula: ; in, For thermal power units at time Output power at the moment, in MW; is the initial power output of the thermal power unit, in MW; is the maximum power ramp rate of the thermal power unit, in MW / s; is the control signal of the thermal power unit, ranging from [0, 1], dimensionless; is the time variable, unit is s.

[0028] 2. Energy storage system module: The energy storage system responds quickly to grid frequency fluctuations, and its output power Controlled signal Adjust, satisfy: ; in, For energy storage system in time Output power at the moment, in MW; is the control signal of the energy storage system, ranging from [0, 1], dimensionless; It is the maximum output power of the energy storage system, in MW.

[0029] Energy storage system charge state The dynamic change formula is: ; in, For energy storage system in time The state of charge at the moment, in MWh; For energy storage system in time Output power at the moment, in MW; is the time variable, unit is s;

[0030] The power and state of charge of the energy storage system must meet the following constraints: , ; in, , They are the minimum and maximum state of charge limits of the energy storage system, in MWh.

[0031] 3. Energy management and distribution control module: The energy management module is based on the optimization objective function Determine the power distribution ratio between thermal power units and energy storage systems ,but: ; in, It is the system optimization target value, in MW2 ·s; For the power grid in time Frequency deviation at the moment, in Hz; , are the thermal power unit and the energy storage system at time Output power at the moment, in MW; , are the power penalty coefficients of thermal power units and energy storage systems, dimensionless; The time period for frequency modulation optimization, in seconds.

[0032] Power allocation formula: , ; in, is the power allocation ratio of thermal power units, ranging from [0, 1], dimensionless; For the power grid in time Load power deviation at the moment, in MW.

[0033] Allocation ratio Dynamic update formula: ; in, , The time and time The power allocation ratio at the moment, dimensionless; is the learning rate, which controls the iteration step size and is dimensionless; is the partial derivative of the objective function with respect to the allocation ratio, in MW 2 .

[0034] 4. Communication and monitoring module: The communication and monitoring module monitors the frequency deviation of the power grid in real time , Load power deviation , energy storage status , and generates control signals and They are sent to thermal power units and energy storage systems respectively.

[0035] The following is a specific description in conjunction with several embodiments: Example 1: Initial value of grid frequency , target frequency . Frequency Deviation , thermal power units and energy storage systems work together to regulate frequency.

[0036] To calculate the load power deviation, use the formula: ; in, is the grid load power deviation, in MW; , then the conversion coefficient between frequency and power deviation is: ; Calculated: ; Power distribution optimization: Initial power allocation ratio ,but: ; ; Generate control signal: thermal power unit control signal: , ; Calculated: ; Energy storage system control signal: , ; Calculated: ; Frequency recovery: The thermal power units and the energy storage system work together to restore the frequency to 49.95Hz within 10 seconds.

[0037] Example 2: Fluctuations in renewable energy cause the grid frequency to drop to , target frequency ; Frequency deviation ;Energy storage system responds first.

[0038] Calculate the load power deviation: ; parameter: , ; Calculated: ; Energy storage-dominated power allocation: initial allocation ratio ,but ; ; Generate control signal: thermal power unit control signal: , ; ; Energy storage system control signal: , ; ; Energy storage charge state update: initial state ,but: ; Frequency recovery: The energy storage system acts quickly, restoring the frequency to 49.85Hz within 5 seconds.

[0039] Example 3: High grid inertia (M=10MW\cdops 2 / Hz), the frequency fluctuates slowly. Target frequency , initial frequency ,deviation .

[0040] Calculate the load power deviation: ; parameter: , .

[0041] Calculated: ; Thermal power dominated power allocation: Initial allocation ratio ,but: , ; Generate control signals: Thermal power unit control signal: , ; ; Energy storage system control signal: , ; ; Frequency recovery: Within 15 seconds, the frequency recovered to 49.98Hz.

[0042] Example 4: During long-term frequency regulation, the energy storage charge state needs to be maintained within a reasonable range to avoid over-discharge or over-charge. .

[0043] The current frequency deviation is , the target frequency is .

[0044] Load power deviation calculation: ; in, is the load power deviation, in MW; is the frequency adjustment coefficient, , unit: MW / Hz; ; Calculated: ; Power allocation optimization: The initial allocation ratio is set to ,but: ; ; Energy storage charge status dynamic update: Use the formula: ; in, For energy storage system in time The state of charge at the moment, in MWh; is the output power of the energy storage system, in MW; is the time step, unit s; initial state ; Update calculation: ; Long-term optimization scheduling: Assuming that the frequency deviation per second gradually decreases, then: Second 2: , ; Distributing power: , ; State of Charge Update: ; Second 3: , the frequency returns to normal and the energy storage system stops outputting power: ; Result analysis: Through reasonable power distribution and dynamic state of charge adjustment, the energy storage system maintains a stable state of charge in long-term operation, avoids over-charging and discharging, and completes the rapid recovery of grid frequency.

[0045] Initial state: ; Final state: .

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A thermal power unit-energy storage coupling frequency modulation system for improving the frequency stability of the power grid, characterized in that: Includes the following modules: Thermal power unit frequency regulation module: Provides basic frequency regulation capability through thermal power units, and its output power The following dynamic equations are satisfied: ； in, For thermal power units at time Output power at the moment, in MW; is the initial output power of the thermal power unit, in MW; is the maximum power ramp rate of the thermal power unit, in MW / s; is the control signal of the thermal power unit, ranging from [0,1]; Energy storage system module: including battery energy storage or flywheel energy storage system, whose output power and state of charge The following dynamic equations and constraints are satisfied: ； ； ， ； in, For energy storage system in time Output power at the moment, in MW; is the control signal of the energy storage system, ranging from [0,1]; is the state of charge of the energy storage system, in MWh; is the initial charge state; , They are the minimum and maximum state of charge limits of the energy storage system respectively; is the maximum power output of the energy storage system, in MW; Energy management and distribution control module: according to the grid frequency deviation Dynamically adjust the output power of thermal power units and energy storage systems to meet the following power balance equation: ； in, is the deviation between grid load power and power generation power, in MW; is the grid frequency deviation, unit: Hz; Communication and monitoring module: used to monitor grid frequency fluctuations, energy storage status and thermal power unit operation status, and transmit control signals , .

2. The thermal power generation unit-energy storage coupling frequency modulation system for improving the frequency stability of the power grid according to claim 1 is characterized in that: The energy management and distribution control module is based on the optimization objective function The power distribution of thermal power units and energy storage systems is controlled, and the objective function is: ； in, is the total system operating cost, unit MW 2 ·s; The time period for optimizing frequency modulation, in seconds; and are the power penalty coefficients of thermal power units and energy storage systems, both are dimensionless; It is the grid frequency deviation, in Hz.

3. The thermal power generation unit-energy storage coupling frequency modulation system for improving the frequency stability of the power grid according to claim 2 is characterized in that: The thermal power unit is at time Output power at the moment The following dynamic constraints are met: ； in, is the maximum power ramp rate of the thermal power unit, in MW / s; It is the power change rate of thermal power unit, in MW / s.

4. The thermal power generation unit-energy storage coupling frequency modulation system for improving the grid frequency stability according to claim 2 is characterized in that: The output power of the energy storage system at time The following dynamic constraints are met: ； in, The maximum power output of the energy storage system, in MW.

5. The thermal power generation unit-energy storage coupling frequency modulation system for improving the grid frequency stability according to claim 1 is characterized in that: The state of charge of the energy storage system The following constraints are met: ； in, For energy storage system in time The state of charge at the moment, in MWh; is the minimum state of charge of the energy storage system, in MWh; It is the maximum state of charge of the energy storage system, in MWh.

6. The thermal power generation unit-energy storage coupling frequency modulation system for improving the grid frequency stability according to claim 2 is characterized in that: The power distribution ratio of the thermal power unit and the energy storage system is determined by the optimization variable Determine that the following power allocation equation is satisfied: ； in, For thermal power units at time Output power at the moment, in MW; For energy storage system in time Output power at the moment, in MW; is the deviation between the grid load power and the generated power, in MW; is the power allocation ratio coefficient, ranging from [0,1], dimensionless, and represents the proportion of thermal power units in power allocation.

7. The thermal power generation unit-energy storage coupling frequency modulation system for improving the grid frequency stability according to claim 6 is characterized in that: The optimization variables The following iteration formula is satisfied: ； in, is the power allocation ratio coefficient at the next moment, ranging from [0,1], dimensionless; is the power allocation ratio coefficient at the current moment, ranging from [0,1], dimensionless; is the learning rate, which indicates the step size of iterative optimization and is dimensionless; is the objective function right The partial derivative of 2 ; It is the system optimization objective function, which represents the comprehensive index of frequency deviation and power cost, and the unit is MW 2 ·s.

8. The thermal power generation unit-energy storage coupling frequency modulation system for improving the frequency stability of the power grid according to claim 2 is characterized in that: The grid frequency deviation Satisfies the following dynamic change equation: ； in, For the power grid in time The frequency deviation at the moment, in Hz; is the time derivative of the frequency deviation, in Hz / s; is the grid time constant, which indicates the time characteristic of frequency regulation response, in seconds; is the grid inertia constant, which indicates the grid's inertial anti-disturbance capability to frequency changes, and its unit is MW·S 2 / Hz; It is the deviation between grid load power and power generation power, in MW.

9. The thermal power generation unit-energy storage coupling frequency modulation system for improving the grid frequency stability according to claim 8 is characterized in that: The final response of the frequency deviation satisfies the following closed-loop control formula: ； in, For the power grid in time The frequency deviation at the moment, in Hz; is the frequency deviation of the power grid at the initial moment, in Hz; is the grid time constant, which indicates the time characteristic of frequency regulation response, in seconds; is the grid inertia constant, which indicates the grid's inertial anti-disturbance capability to frequency changes, and its unit is MW·S 2 / Hz; is the current moment, in seconds; is the integral variable, which represents the intermediate variable of time integration, and its unit is s; For time Load power deviation at the moment, in MW; The energy management and distribution control module adopts the model predictive control algorithm according to the dynamic characteristics of the thermal power unit. , Energy storage system charge state and frequency deviation Optimize power distribution.

10. The frequency modulation method of the thermal power unit-energy storage coupling frequency modulation system according to any one of claims 1 to 9, characterized in that: The specific steps include: Real-time monitoring of grid frequency deviation and power deviation ,Right now: ; Optimizing the calculation of power distribution of thermal power units And energy storage system output ; Generate control signals and And sent to thermal power units and energy storage systems; Feedback closed loop control, adjust power output until frequency deviation Converge to the target range.

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