Electrode boiler and heat storage tank combined peak regulation system and method of a combined heat and power unit

Abstract

The present application relates to the technical field of thermoelectricity, and more particularly to a combined peak shaving system and method of electrode boiler and heat storage tank of a combined heat and power unit, which deeply integrates the electrode boiler, the heat storage tank and a low-temperature waste heat recovery module of the unit, and additionally adds an intelligent control unit to realize accurate linkage of pipeline connection and peak shaving instructions. In deep peak shaving, the three work cooperatively in time, space and grade: the electrode boiler responds quickly to provide main heat-electricity decoupling capacity; at the same time, the low-temperature waste heat recovery module recovers the waste heat that may be wasted when the unit is operated at low load; and the heat storage tank realizes fluctuation suppression and storage of heat from the above-mentioned multiple sources. This coupling solves the defects of a single technical path and realizes synergistic effect.

Description

Technical Field

[0001] This invention relates to the field of thermoelectric technology, and more specifically, to a combined peak-shaving system and method for electrode boilers and thermal storage tanks in cogeneration units. Background Technology

[0002] With the large-scale grid connection of fluctuating renewable energy sources such as wind power and photovoltaics, the power grid has placed higher demands on the deep peak-shaving capabilities of traditional thermal power units, especially combined heat and power (CHP) units. The "heat-driven power generation" operating characteristic of CHP units makes it difficult to reduce their power output during the heating season, which severely restricts the peak-shaving capacity of the power grid.

[0003] In existing technologies, the following technical routes are mainly adopted to achieve thermoelectric decoupling: First, electrode boilers or electric boilers are used to directly consume electrical energy to generate heat, replacing part of the unit's heating supply, thereby reducing power generation output; second, large heat storage tanks are added to realize the time transfer of heat energy, storing heat during off-peak hours and releasing heat during peak hours; third, the unit itself is modified, such as by adopting bypass heating, steam ejector to recover waste heat, or steam compressor pressurization, to maintain or improve heating capacity while reducing electrical load.

[0004] However, the aforementioned technical approaches each have their limitations. While a single electric boiler solution offers a fast response, its energy conversion is singular and it doesn't utilize the unit's own waste heat, leaving room for improvement in overall energy efficiency. Individual thermal storage technologies, although capable of time-shifting heat energy, don't synergize with the recovery of low-grade waste heat during deep peak shaving. Furthermore, when modifying the unit itself for deep peak shaving, the unit operates at extremely low loads, resulting in a significant reduction or even a decrease in the quality of the low-temperature exhaust steam or circulating water waste heat available for recovery, leading to a decline in the efficiency and economy of the waste heat recovery system.

[0005] Therefore, how to design a system that can not only achieve thermoelectric decoupling under deep peak shaving conditions, but also efficiently and economically recover and utilize the unit's own low-grade waste heat, and achieve optimized energy storage and release, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a combined peak-shaving system and method for electrode boilers and thermal storage tanks in cogeneration units. Through innovative integration, this system synergistically utilizes electrical energy and unit waste heat during periods of deep grid peak shaving, significantly reducing unit power output while substantially improving the overall energy efficiency, heating reliability, and operational economy of the system.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a combined peak-shaving system for an electrode boiler and a thermal storage tank in a cogeneration unit, applicable to a cogeneration unit comprising a boiler, a turbine system, a generator, and a heating network heater, wherein the turbine system comprises a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, a condenser, and a low-pressure heater connected in sequence, characterized in that the system comprises:

[0008] An electrode boiler module, wherein the power supply terminal of the electrode boiler module is connected to the plant power system or the power grid;

[0009] Thermal storage tank module;

[0010] A low-temperature waste heat recovery module is used to extract heat from the low-temperature heat source of the steam turbine system;

[0011] Integrated coupling of piping and valve assemblies;

[0012] The intelligent control unit is communicatively connected to the valve assembly;

[0013] The heat output end of the electrode boiler module is connected to the heat storage inlet of the heat storage tank module, the heat source inlet of the heating network heater, or the heat exchange medium inlet of the low temperature waste heat recovery module through the integrated coupling pipeline and valve group, according to the load demand corresponding to the power grid peak shaving command.

[0014] The heat output end of the low-temperature waste heat recovery module is connected to the heat storage inlet of the heat storage tank module, the heat source inlet of the heat network heater, or the water inlet of the electrode boiler module through the integrated coupling pipeline and valve group, depending on the difference in heat grade.

[0015] The heat release outlet of the heat storage tank module is connected to the heat source inlet of the heating network heater through the integrated coupling pipeline and valve group when the unit needs to increase its power generation output.

[0016] A further technical solution of this application: the low-temperature heat source includes at least one of the following: the low-pressure cylinder exhaust passage of the turbine system, the condenser circulating water system, or the low-pressure heater condensate system.

[0017] A further technical solution of this application: the low-temperature waste heat recovery module includes a first heat exchanger for extracting heat from the condenser circulating water system, and / or a second heat exchanger for extracting heat from the low-pressure heater drain system.

[0018] A further technical solution of this application: the system also includes an intelligent control unit, which is communicatively connected to the power grid dispatch signal, the unit load signal, the heating network load signal, various temperature and flow sensors, and the regulating valves and switching valves in the valve group;

[0019] The intelligent control unit is configured to automatically control the opening and closing of the valve group and the degree of opening according to a preset strategy. The preset strategy is adapted to different operating conditions. When the power generation output of the unit is lower than a first threshold, the intelligent control unit controls the electrode boiler module to generate heat and the low-temperature waste heat recovery module to recover heat, and introduces the two types of heat into the heat storage tank module for storage. At the same time, it coordinates the heat supply distribution of the heat storage tank module, the electrode boiler module and the unit's extracted steam. When the power grid requires an increase in power generation output, the intelligent control unit controls the electrode boiler module to reduce the load or stop operation, and opens the heat storage tank module to release heat to replace the unit's extracted steam for heating. The intelligent control unit adjusts the energy distribution ratio of the electrode boiler module's heat generation, the low-temperature waste heat recovery module's heat exchange and the heat storage tank module's heat charging and releasing based on real-time electricity price, peak-shaving compensation price and fuel cost, combined with the unit's operating parameters.

[0020] A method for combined peak shaving of an electrode boiler and a thermal storage tank in a cogeneration unit includes the following steps:

[0021] Monitor power grid peak-shaving commands, real-time generating load of generating units, and heating network load;

[0022] When a grid peak-shaving instruction is received, requiring the generating unit to reduce its power output to below the first threshold, it enters deep peak-shaving mode.

[0023] In the deep peak shaving mode, a coordinated control strategy is executed: the electrode boiler module is started to generate heat; the low-temperature waste heat recovery module is started simultaneously to recover the low-temperature heat source heat of the steam turbine system;

[0024] The heat generated by the electrode boiler module and / or the heat recovered by the low-temperature waste heat recovery module is introduced into the heat storage tank module for storage; at the same time, the distribution of heat from the heat storage tank module and / or the electrode boiler module and / or the original heating steam extracted from the unit to the heating network is controlled.

[0025] A further technical solution of this application includes a peak operation mode: when the power grid requires the unit to increase its power generation output, the operation of the electrode boiler module is reduced or stopped, and the heat storage tank module is controlled to release the stored heat to replace the unit's steam extraction for heating, thereby increasing the amount of steam entering the turbine to do work.

[0026] A further technical solution of this application: The collaborative control strategy includes an economic optimization sub-strategy: Based on the real-time electricity price signal, peak-shaving compensation price signal, fuel cost data collected by the intelligent control unit, as well as the detection data of the unit load sensor, the heating network temperature sensor, and the heat storage tank load status sensor, the optimal energy allocation scheme is calculated through a mixed integer linear programming algorithm to dynamically optimize the energy allocation between the heat generation power of the electrode boiler module, the heat exchange medium flow rate of the low-temperature waste heat recovery module, and the heat charging and discharging rate of the heat storage tank module.

[0027] A further technical solution of this application: In the deep peak shaving mode, the heat introduced into the heat storage tank module includes high-temperature hot water from the electrode boiler module and low-temperature hot water from the low-temperature waste heat recovery module. The heat storage tank module uses thermocline technology to store the high-temperature hot water and low-temperature hot water in layers.

[0028] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0029] 1. This invention deeply integrates the electrode boiler, thermal storage tank, and the unit's low-temperature waste heat recovery channel, and the added intelligent control unit enables precise linkage between pipeline connections and peak-shaving commands. During deep peak shaving, the three components work synergistically in terms of time, space, and grade: the electrode boiler responds quickly, providing the main thermoelectric decoupling capability; simultaneously, the low-temperature waste heat recovery module recovers waste heat that might otherwise be wasted when the unit is operating at low load; and the thermal storage tank smooths out fluctuations and stores heat from the aforementioned multiple sources. This coupling overcomes the shortcomings of single-technology paths, achieving synergistic efficiency; furthermore, traditional deep peak shaving schemes often sacrifice unit economics, while this invention, by simultaneously recovering low-grade waste heat during load reduction and converting electrical energy into high-value thermal energy storage, enables the system's overall energy utilization rate to increase rather than decrease under low power generation load, overcoming the problem of declining thermal economics in traditional schemes.

[0030] 2. The system of this invention has multiple operating modes, which can be flexibly switched according to the demand of the power grid and heating network and market price signals. The addition of the thermal storage tank greatly enhances the reliability and buffering capacity of the heating system, ensuring the stability of heating quality under any operating condition. At the same time, compared with complex systems such as molten salt thermal storage and compressed air energy storage, the scheme of this invention has better feasibility and economy, mainly because the electrode boiler and water thermal storage technology used in this invention are mature and reliable. The amount of engineering work required to retrofit existing cogeneration units is relatively small, the interface is simple, the investment cost is low, and it is easier to promote and implement in existing power plants, with significant market application prospects. The collaborative control architecture of the intelligent control unit realizes the automation and precision of valve opening and closing and module start and stop, avoiding the lag and error of manual control. The selective connection logic designed according to the load demand and heat quality differences realizes the cascade utilization of energy, further improving the energy utilization efficiency of the system.

[0031] The economic optimization sub-strategy based on mixed-integer linear programming algorithm combines real-time electricity prices, fuel costs and other market data with unit operating parameters. It achieves the optimal solution for energy allocation through quantitative calculation, avoiding the limitations of empirical control and maximizing the overall benefits of system operation, which is different from the management model that relies solely on commercial strategies. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the system structure of the present invention; Figure 2 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The present invention will be further described below with reference to the embodiments.

[0034] Please see Figure 1 In one embodiment of this application, the electrode boiler and thermal storage tank combined peak-shaving system of the cogeneration unit proposed in this invention is applied to a cogeneration unit including a boiler, a steam turbine system, a generator and a heating network heater. The steam turbine system includes a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, a condenser and a low-pressure heater connected in sequence.

[0035] The system includes: an electrode boiler module, whose power supply is connected to the plant power system or the power grid; a heat storage tank module; a low-temperature waste heat recovery module for extracting heat from the low-temperature heat source of the turbine system; an integrated coupling pipeline and valve group; and an intelligent control unit that is communicatively connected to the valve group.

[0036] The heat output terminal of the electrode boiler module is selectively connected to the heat storage inlet of the heat storage tank module, the heat source inlet of the heating network heater, or the heat exchange medium inlet of the low-temperature waste heat recovery module, according to the load demand corresponding to the grid peak-shaving command, through the integrated coupling pipeline and valve group. The heat output terminal of the low-temperature waste heat recovery module is selectively connected to the heat storage inlet of the heat storage tank module, the heat source inlet of the heating network heater, or the water inlet of the electrode boiler module, according to the heat grade difference, through the integrated coupling pipeline and valve group. The heat release outlet of the heat storage tank module is selectively connected to the heat source inlet of the heating network heater when the unit needs to increase its power generation output, through the integrated coupling pipeline and valve group.

[0037] Furthermore, the low-temperature heat source includes at least one of the following: the low-pressure cylinder exhaust passage of the turbine system, the condenser circulating water system, or the low-pressure heater condensate system.

[0038] Furthermore, the low-temperature waste heat recovery module includes a first heat exchanger for extracting heat from the condenser circulating water system, and / or a second heat exchanger for extracting heat from the low-pressure heater drain system.

[0039] Furthermore, it also includes an intelligent control unit, which is communicatively connected to the grid dispatch signal, unit load signal, heating network load signal, various temperature and flow sensors, and the regulating valves and switching valves in the valve group. The intelligent control unit is configured to automatically control the opening and closing and the degree of opening of the valve group according to a preset strategy. The preset strategy is adapted to different operating conditions. When the unit's power generation output is lower than a first threshold, the intelligent control unit controls the electrode boiler module to generate heat and the low-temperature waste heat recovery module to recover heat, and introduces the two types of heat into the heat storage tank module for storage. At the same time, it coordinates the heat supply distribution of the heat storage tank module, the electrode boiler module, and the unit's extracted steam. When the grid requires an increase in power generation output, the intelligent control unit controls the electrode boiler module to reduce its load or stop operating, and opens the heat storage tank module to release heat to replace the unit's extracted steam for heating. The intelligent control unit can also adjust the energy distribution ratio of the electrode boiler module's heat generation, the low-temperature waste heat recovery module's heat exchange, and the heat storage tank module's heat charging and releasing based on real-time electricity price, peak-shaving compensation price, fuel cost, and unit operating parameters.

[0040] The core new components of the system include: Electrode Boiler: A high-pressure electrode hot water boiler is adopted, whose power supply is connected to the plant's kV busbar, and can directly consume the energy generated by the generator or absorb energy from the grid. Thermal Storage Tank: A large atmospheric pressure inclined thermostatic water thermal storage tank is adopted, and its volume is designed according to the unit's peak-shaving requirements and site conditions. Temperature monitoring sensors are installed inside the thermal storage tank to provide real-time feedback on the water temperature of the upper and lower layers of the tank, providing data support for the stratified storage of the inclined thermostatic layer. Low-Temperature Waste Heat Recovery Module: This embodiment includes two parallel heat exchangers. The first heat exchanger is arranged on the circulating water outlet pipe of the condenser to recover waste heat in the circulating water. The second heat exchanger is connected to the drain pipe of the low-pressure heater to recover heat in the drain. Both heat exchangers are equipped with flow regulating valves, and the flow rate of the heat exchange medium is adjusted in real time by the intelligent control unit according to the heat grade.

[0041] Integrated coupling piping and valve group: A complex fluid network consisting of a series of pipes, pumps, regulating valves, and switching valves. This network achieves the following key connections: hot water from the electrode boiler outlet is directed to the upper part of the thermal storage tank and the heating network heater; hot water recovered from the first and second heat exchangers is directed to the lower part of the thermal storage tank and the inlet of the electrode boiler; hot water from the upper part of the thermal storage tank is directed to the heating network heater; and the return water from the heating network or condensate from the unit is used as the working fluid and transported to each heat exchange unit. All branch valves are electrically controlled and connected to the intelligent control unit, allowing for rapid switching of open and closed states based on control commands. A PLC controller serves as the intermediate execution unit between the intelligent control unit and the valve group, receiving command signals from the intelligent control unit and driving the opening, closing, and adjustment of the opening degree of each branch valve to achieve precise switching of piping connections. A DCS controller receives all sensor signals and external commands, outputting control signals to the intelligent control unit and pumps to execute pre-programmed control strategies. The control strategy incorporates valve action logic for three operating conditions: deep peak shaving, peak operation, and economic optimization, enabling mode switching without manual intervention.

[0042] Please see Figure 2 As a preferred embodiment of this application, a method for combined peak shaving of an electrode boiler and a thermal storage tank in a cogeneration unit includes the following steps:

[0043] The system monitors grid peak-shaving commands, real-time generator load, and heating network load. When a grid peak-shaving command is received, requiring the generator to reduce its power output to below a first threshold, the system enters deep peak-shaving mode. In this deep peak-shaving mode, a coordinated control strategy is implemented: the electrode boiler module is started to generate heat; the low-temperature waste heat recovery module is simultaneously started to recover the low-temperature heat source heat of the turbine system; the heat generated by the electrode boiler module and / or the heat recovered by the low-temperature waste heat recovery module is introduced into the heat storage tank module for storage; and the distribution of heat from the heat storage tank module and / or the electrode boiler module and / or the original heating steam extracted from the generator to the heating network is controlled.

[0044] Furthermore, the "first threshold" is a lower limit setting value for the generating output of the unit that triggers the deep peak shaving mode. Its physical meaning and determination method include one or more of the following technical principles:

[0045] Unit safety operation constraints: The first threshold shall not be lower than the minimum stable power generation load allowed by the unit. This load is determined by the boiler's stable combustion characteristics, the turbine's vibration zone, and the safety boundary of auxiliary equipment operation. It is a basic technical parameter to ensure the safety of the unit equipment.

[0046] Thermoelectric coupling constraint: The setting of the first threshold needs to take into account the current heating load of the heating network. Under the premise of ensuring that the basic heating demand is met, the lower limit of the power generation output that can be safely decoupled is calculated through the collaboration of the electrode boiler module and the thermal storage tank module, thereby achieving effective "thermoelectric decoupling".

[0047] Grid dispatch requirements: The first threshold can directly respond to or be slightly higher than the target power generation output value specified in the grid dispatch instruction, so as to ensure that the power generation output of the unit can be reliably reduced to the peak shaving depth required by the grid.

[0048] Economic boundary: Taking into account peak shaving compensation and fuel costs, the first threshold can be set near the output point where the marginal benefit of unit power generation is close to or below zero, making it economically feasible to enter the deep peak shaving mode.

[0049] In practical applications, the first threshold can be dynamically calculated or obtained by the intelligent control unit based on the above principles, combined with real-time operating data and preset algorithms, or by looking up a table; it is not a fixed value.

[0050] Furthermore, it also includes a peak operation mode: when the power grid requires the unit to increase its power generation output, the operation of the electrode boiler module is reduced or stopped, and the heat storage tank module is controlled to release the stored heat to replace the unit's steam extraction for heating, thereby increasing the amount of steam entering the turbine to do work.

[0051] Furthermore, the collaborative control strategy includes an economic optimization sub-strategy: based on real-time electricity price signals, peak-shaving compensation price signals, fuel cost data collected by the intelligent control unit, and detection data from unit load sensors, heating network temperature sensors, and thermal storage tank load status sensors, the optimal energy allocation scheme is calculated using a mixed integer linear programming algorithm to dynamically optimize the energy allocation between the heat generation power of the electrode boiler module, the heat exchange medium flow rate of the low-temperature waste heat recovery module, and the heat charging and discharging rate of the thermal storage tank module.

[0052] Furthermore, in the deep peak shaving mode, the heat introduced into the heat storage tank module includes high-temperature hot water from the electrode boiler module and low-temperature hot water from the low-temperature waste heat recovery module. The heat storage tank module utilizes thermocline technology to store the high-temperature hot water and low-temperature hot water in layers.

[0053] Example of system operating mode:

[0054] Mode 1: Nighttime deep peak shaving and waste heat recovery storage mode.

[0055] Scenario: At night, the grid load is low, wind power generation is high, and the grid requires the generating units to reduce their output from 300MW to 150MW.

[0056] Control logic:

[0057] (1) The intelligent control unit receives the peak shaving command.

[0058] (2) Gradually close the steam inlet valve of the steam turbine to reduce the power generation load. At the same time, reduce the amount of steam extracted from the intermediate pressure cylinder 3 to the heating network heater 7.

[0059] (3) Start the electrode boiler and use the surplus electricity or low-priced off-peak electricity in the plant to produce high-temperature hot water (e.g., 150℃).

[0060] (4) The low-temperature waste heat recovery module is started simultaneously. The circulating water pump and valve send the condensate into the first heat exchanger and the second heat exchanger to absorb the heat in the condenser circulating water and the low-temperature heater condensate to produce low-temperature hot water (such as 70-90℃).

[0061] (5) Control the valves to guide some or all of the high-temperature hot water generated by the electrode boiler into the upper part of the heat storage tank for storage. At the same time, control the valves to guide the low-temperature hot water produced by the low-temperature waste heat recovery module into the lower part of the heat storage tank for storage. The inclined temperature layer technology ensures the stratified storage of heat.

[0062] (6) Heating guarantee: At this time, the heat required by the heating network is provided by the direct release of heat from the heat storage tank and the combined extraction of steam from the remaining units. The user side is unaware of the heating supply.

[0063] Results: The unit's electrical output decreased significantly, freeing up space for new energy sources. Simultaneously, the system not only converts electrical energy into thermal energy for storage but also recovers waste heat from low-load conditions, resulting in higher overall energy efficiency than solutions using only electrode boilers.

[0064] Mode 2: Daytime peak power generation mode.

[0065] Scenario: During peak daytime electricity consumption, grid electricity prices are high, requiring generating units to increase power output.

[0066] Control logic:

[0067] (1) Stop or minimize the operation of the electrode boiler.

[0068] (2) Fully open the heat storage tank's heat release valve and may close some of the unit's heating steam extraction valves, so that the heat storage tank 9 can bear most or all of the instantaneous heating load.

[0069] (3) The extracted steam originally used for heating can be returned to the turbine to do work, thereby significantly increasing the unit's power generation capacity when the boiler load remains unchanged or increases slightly.

[0070] (4) In this mode, the low-temperature waste heat recovery module can continue to operate, and its heat generation can be directly added to the heating network or preheated electrode boiler feedwater.

[0071] Effect: Enhanced peak capacity of the generating units allows for higher power generation revenue during peak electricity market periods.

[0072] Mode 3: Economic Optimization Operation Mode.

[0073] The intelligent control unit has a built-in optimization algorithm that formulates the optimal "electricity-heat-storage" scheduling plan based on the predicted electricity price, heat price, and peak-shaving ancillary service price for the next hour. For example, during the period of lowest electricity price, the electrode boiler is started up to maximize heat production and stored in the thermal storage tank; during the period of peak electricity price, the thermal storage tank is mainly used for heating, and the unit generates more high-priced electricity.

[0074] The intelligent control unit's built-in optimization algorithm is a multi-objective, multi-time-scale, and multi-constraint collaborative optimization system. Its core objective is to achieve optimal overall system economics (or lowest comprehensive cost) while maximizing peak-shaving ancillary service revenue, under the premise of meeting grid security constraints, unit physical limits, and heating quality requirements.

[0075] Optimization level:

[0076] Optimized scheduling (time scale: 24 hours, resolution: 15 minutes to 1 hour): Based on electricity prices and load forecasts, formulate the optimal scheduling plan for the whole day.

[0077] Intraday rolling optimization (time scale: 4 hours, resolution: 5-15 minutes): Adjust the scheduling plan based on actual operational deviations and ultra-short-term forecasts.

[0078] Real-time coordinated control (time scale: seconds to minutes): quickly responds to AGC commands and frequency fluctuations, and executes optimized results.

[0079] Optimization algorithms essentially solve a mixed-integer linear programming (MILP) or nonlinear programming (NLP) problem, and their mathematical model can be expressed as follows:

[0080] 1. Objective function (maximize total revenue or minimize total cost).

[0081] ;

[0082] in: The on-grid electricity revenue (power generation × on-grid electricity price) for time period t.

[0083] The revenue from peak shaving / frequency regulation ancillary services for time period t (depending on the peak shaving depth and response speed provided);

[0084] For time period t, the fuel cost (boiler coal / gas cost) is used.

[0085] This represents the total number of time periods in the scheduling cycle.

[0086] The total revenue of the system;

[0087] This represents the cost of purchased electricity during time period t (if the electrode boiler uses low-priced electricity from the grid, this is a negative cost; if it consumes high-priced electricity from within the plant, it is a positive cost).

[0088] 2. Core constraints.

[0089] 2.1 Energy balance constraint:

[0090] Power balance: ;

[0091] The goal is to fulfill the power grid dispatch instructions;

[0092] Heat balance:

[0093] The purpose is to meet the heating network load.

[0094] Thermal storage tank status:

[0095] It also has upper and lower capacity limits.

[0096] The generating capacity of the unit; The electrical power consumed by the electrode boiler (can be positive, indicating power consumption; or it can be 0). The heat output of the electrode boiler; The power for charging and releasing heat from the heat storage tank; This refers to the power of low-temperature waste heat recovery; The steam extraction power for heating the unit; The heat storage tank is in a state of heat load (percentage of stored heat). The heat release efficiency of the heat storage tank; The heat storage tank's charging efficiency; This represents the heat load state of the heat storage tank during time period t+1; This refers to the grid's dispatch instructions or load demand on generating units during time period t.

[0097] This is the fundamental demand signal that drives the entire cogeneration system to carry out multi-source coordinated heating and heat storage allocation.

[0098] 2.2 Equipment physical and safety constraints:

[0099] Cogeneration units: operate within the "cogeneration feasible region" and are limited by factors such as minimum power generation output, maximum steam extraction capacity, and minimum cooling flow rate of the low-pressure cylinder.

[0100] Electrode boilers: power adjustment range (e.g., 30%-100%), maximum allowable power, and start-stop frequency limits.

[0101] Thermal storage tank: maximum charge / discharge rate, temperature limit, thermocline stability constraint.

[0102] Low-temperature waste heat recovery: the functional relationship between recovered heat and circulating water temperature and flow rate.

[0103] 2.3 Power grid and heating network constraints: Peak shaving rate limit (ramp rate); heating temperature and pressure must be within the allowable range.

[0104] The intelligent control unit performs optimization according to the following process:

[0105] Optimized dispatch strategy prior to 3.1: During off-peak electricity price periods (e.g., 00:00-06:00): The algorithm tends to maximize the power of the electrode boiler, converting cheap electricity into heat energy stored in the thermal storage tank, while the unit maintains its minimum technical output to provide the grid with the maximum downward peak-shaving capacity. Low-temperature waste heat recovery operates simultaneously, and the recovered waste heat is also stored in the thermal storage tank.

[0106] During peak electricity price periods (e.g., 08:00-11:00, 17:00-22:00): The algorithm stops or minimizes the electrode boiler, instructs the thermal storage tank to release heat at high power, replacing the unit's steam extraction, enabling the unit to maximize power generation and sell electricity at higher prices. At this time, the system provides upward peak shaving (peak) capability.

[0107] Normal period: Based on real-time electricity prices and heat load, energy is economically allocated between "power generation" and "thermal storage".

[0108] This algorithm has significant advantages and innovations, which are specifically reflected in the following:

[0109] Maximizing profits throughout the entire cycle: This algorithm not only considers the real-time balance of electricity and heat, but also uses predictive optimization methods to achieve cross-time arbitrage goals (such as "valley electricity storage for heat and peak electricity sales").

[0110] Multi-source collaborative optimization: The algorithm performs unified optimization on the conversion and storage of three energy sources: electricity, heat, and energy storage, breaking through the limitations of traditional item-by-item optimization.

[0111] Strictly embedded safety constraints: The physical limits of the equipment and the power grid specifications are directly set as constraints to ensure that the optimization results are safe and feasible.

[0112] The algorithm employs rolling optimization and feedback correction mechanisms, which can effectively overcome prediction errors and external disturbances, and maintain the stable and economical operation of the system.

[0113] Furthermore, this algorithm framework can be seamlessly integrated into advanced application scenarios such as electricity spot market and ancillary service market pricing.

[0114] In summary, this invention creatively integrates the electrode boiler, thermal storage tank, and the unit's low-temperature waste heat recovery channel. During deep peak shaving, the three components work synergistically in terms of time, space, and grade: the electrode boiler responds quickly, providing the main thermoelectric decoupling capability; simultaneously, the low-temperature waste heat recovery module recovers waste heat that might otherwise be wasted during low-load operation; and the thermal storage tank smooths out fluctuations and stores heat from the aforementioned multiple sources. This coupling overcomes the shortcomings of single-technology paths, achieving synergistic efficiency. Furthermore, traditional deep peak shaving schemes often sacrifice unit economics, while this invention, by simultaneously recovering low-grade waste heat during load reduction and converting electrical energy into high-value thermal energy storage, increases the overall energy utilization rate of the system under low power generation loads, overcoming the problem of decreased thermal economics in traditional schemes. Through ingenious system integration and intelligent control, this invention achieves multiple objectives: deep peak shaving, waste heat recovery, thermal energy storage, and market revenue, demonstrating outstanding innovation, practicality, and economy.

[0115] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

[0116] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A combined peak-shaving system for an electrode boiler and thermal storage tank in a cogeneration unit, applied to a cogeneration unit comprising a boiler, a turbine system, a generator, and a heating network heater, wherein the turbine system comprises a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, a condenser, and a low-pressure heater connected in sequence, characterized in that, The system includes: An electrode boiler module, wherein the power supply terminal of the electrode boiler module is connected to the plant power system or the power grid; Thermal storage tank module; A low-temperature waste heat recovery module is used to extract heat from the low-temperature heat source of the steam turbine system; Integrated coupling of piping and valve assemblies; The intelligent control unit is communicatively connected to the valve assembly; The heat output end of the electrode boiler module is connected to the heat storage inlet of the heat storage tank module, the heat source inlet of the heating network heater, or the heat exchange medium inlet of the low temperature waste heat recovery module through the integrated coupling pipeline and valve group, according to the load demand corresponding to the power grid peak shaving command. The heat output end of the low-temperature waste heat recovery module is connected to the heat storage inlet of the heat storage tank module, the heat source inlet of the heat network heater, or the water inlet of the electrode boiler module through the integrated coupling pipeline and valve group, depending on the difference in heat quality. The heat release outlet of the heat storage tank module is connected to the heat source inlet of the heating network heater through the integrated coupling pipeline and valve group when the unit needs to increase its power generation output.

2. The combined peak-shaving system of electrode boiler and thermal storage tank for a cogeneration unit according to claim 1, characterized in that, The low-temperature heat source includes at least one of the following: the low-pressure cylinder exhaust passage of the turbine system, the condenser circulating water system, or the low-pressure heater condensate system.

3. The combined peak-shaving system of electrode boiler and thermal storage tank for a cogeneration unit according to claim 2, characterized in that, The low-temperature waste heat recovery module includes a first heat exchanger for extracting heat from the condenser circulating water system, and / or a second heat exchanger for extracting heat from the low-pressure heater condensate system.

4. The combined peak-shaving system of electrode boiler and thermal storage tank for a cogeneration unit according to claim 1, characterized in that, The system also includes an intelligent control unit, which is communicatively connected to the power grid dispatch signal, the unit load signal, the heating network load signal, various temperature and flow sensors, and the regulating valves and switching valves in the valve group; The intelligent control unit is configured to automatically control the opening and closing of the valve group and the degree of opening according to a preset strategy. The preset strategy is adapted to different operating conditions. When the power generation output of the unit is lower than a first threshold, the intelligent control unit controls the electrode boiler module to generate heat and the low-temperature waste heat recovery module to recover heat, and introduces the two types of heat into the heat storage tank module for storage. At the same time, it coordinates the heat supply distribution of the heat storage tank module, the electrode boiler module and the unit's extracted steam. When the power grid requires an increase in power generation output, the intelligent control unit controls the electrode boiler module to reduce the load or stop operation, and opens the heat storage tank module to release heat to replace the unit's extracted steam for heating. The intelligent control unit adjusts the energy distribution ratio of the electrode boiler module's heat generation, the low-temperature waste heat recovery module's heat exchange and the heat storage tank module's heat charging and releasing based on real-time electricity price, peak-shaving compensation price and fuel cost, combined with the unit's operating parameters.

5. A method for combined peak shaving of an electrode boiler and a thermal storage tank in a cogeneration unit applied to the system described in any one of claims 1-4, characterized in that, Includes the following steps: Monitor power grid peak-shaving commands, real-time generating load of generating units, and heating network load; When a grid peak-shaving instruction is received, requiring the generating unit to reduce its power output to below the first threshold, it enters deep peak-shaving mode. In the deep peak shaving mode, a coordinated control strategy is executed: the electrode boiler module is started to generate heat; the low-temperature waste heat recovery module is started simultaneously to recover the low-temperature heat source heat of the steam turbine system; The heat generated by the electrode boiler module and / or the heat recovered by the low-temperature waste heat recovery module is introduced into the heat storage tank module for storage; at the same time, the distribution of heat from the heat storage tank module and / or the electrode boiler module and / or the original heating steam extracted from the unit to the heating network is controlled.

6. The method for combined peak shaving of electrode boiler and thermal storage tank in a cogeneration unit according to claim 5, characterized in that: It also includes a peak operation mode: when the power grid requires the unit to increase its power generation output, the operation of the electrode boiler module is reduced or stopped, and the heat storage tank module is controlled to release the stored heat to replace the unit's steam extraction for heating, thereby increasing the amount of steam entering the turbine to do work.

7. The method for combined peak shaving of electrode boiler and thermal storage tank in a cogeneration unit according to claim 5, characterized in that: The collaborative control strategy includes an economic optimization sub-strategy: based on real-time electricity price signals, peak-shaving compensation price signals, fuel cost data collected by the intelligent control unit, and detection data from unit load sensors, heating network temperature sensors, and thermal storage tank load status sensors, the optimal energy allocation scheme is calculated using a mixed integer linear programming algorithm to dynamically optimize the energy allocation between the heat generation power of the electrode boiler module, the heat exchange medium flow rate of the low-temperature waste heat recovery module, and the charging and discharging rate of the thermal storage tank module.

8. The method for combined peak shaving of electrode boiler and thermal storage tank in a cogeneration unit according to claim 7, characterized in that, In the deep peak shaving mode, the heat introduced into the heat storage tank module includes high-temperature hot water from the electrode boiler module and low-temperature hot water from the low-temperature waste heat recovery module. The heat storage tank module uses thermocline technology to store the high-temperature hot water and low-temperature hot water in layers.

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