Fireplace power generation and energy storage integrated system and control method thereof

Abstract

The present application relates to the field of waste heat or exhaust heat power generation system, and particularly to a fireplace power generation and energy storage integrated system and a control method thereof. The fireplace combustion waste heat is used to drive a waste heat energy extraction and power generation unit to output direct current, and a cold end heat dissipation is used to maintain a temperature difference and a safety temperature. In a preset control period, a working condition data is formed by synchronously collecting a power generation end voltage, a current, an open circuit voltage, a short circuit current, a hot end / cold end temperature, a flue temperature gradient, an ambient temperature and a heat dissipation state. According to this, a continuously outputtable available power generation capacity parameter of a next period and a wave absorption demand parameter to be borne by a direct current buffer under a battery charging and discharging friendly constraint are calculated. A power supply and charging control strategy set is further solved, and a direct current conversion, the direct current buffer and a load grading power supply are controlled, so that the key load is continuously powered and the main battery current fluctuation is reduced.

Description

Technical Field

[0001] This invention relates to the field of fireplace power generation systems, specifically an integrated fireplace power generation and energy storage system and its control method. Background Technology

[0002] The basic idea behind integrated fireplace power generation and storage is to arrange waste heat extraction and power generation units in high-temperature areas such as the fireplace body or flue. The heat generated by combustion is converted into DC power through thermoelectric conversion. This DC power is then conditioned, charged, and stored locally to provide power for low-power DC loads or emergency loads in the home. Existing publicly available solutions include both thermoelectric power generation (directly outputting DC power based on temperature difference) and the use of micro-combined heat and power devices such as Stirling engines, Rankine cycles / organic Rankine cycles to output power before energy management. On the power side, a system structure of "DC bus—charging control—battery management—DC output / inverter output" is generally adopted to power and charge the load and battery.

[0003] However, fireplace operation exhibits significant non-steady-state characteristics. The combustion process typically involves stages such as ignition and heating, stable flame, and ember decay. The heat intensity at the hot end varies significantly over time, compounded by disturbances such as fuel feeding, damper adjustment, and flue draft changes, causing substantial fluctuations in the voltage, current, and available power of the waste heat power generation unit. In thermoelectric power generation scenarios, changes in temperature difference and contact thermal resistance directly lead to drift in output electrical characteristics. In small-scale heat engines / cycle scenarios, output power also fluctuates with heat load due to start-up inertia, heat transfer lag, working fluid state, and pump and valve control. This coupling relationship between hot-end instability and electrical fluctuations makes it difficult to maintain power supply continuity and energy storage friendliness under all operating conditions by relying solely on traditional voltage stabilization or simple charging strategies.

[0004] From the perspective of power conditioning and energy storage management, the most common control method in existing technologies is to stabilize the DC bus and use constant current / constant voltage or current-limiting voltage regulation to charge the battery. Some solutions also incorporate control near the maximum power point to improve instantaneous power generation utilization. However, under fluctuating conditions like those of a fireplace, if the control objective is biased towards maximizing instantaneous energy extraction, it can easily overload the power generation unit when combustion capacity is insufficient or cold-end heat dissipation capacity decreases. This manifests as a rapid drop in output voltage, DC bus undervoltage, load interruption, and even oscillation. If the control objective is biased towards conservative voltage regulation, it will result in unused energy not being utilized in a timely manner, reduced charging efficiency, and potential bus voltage fluctuations and decreased power quality during switching between different combustion stages. Especially when cold-end heat dissipation is limited (e.g., dust accumulation leads to decreased heat sink efficiency, fan failure, or increased ambient temperature), existing solutions often lack a mechanism to explicitly incorporate cold-end thermal margin into power boundary management. This can easily lead to situations where the cold-end temperature approaches the upper limit but energy continues to be extracted, thereby increasing the risk of thermal stress on the hot-end-cold-end structure, degradation of the thermal interface, and reduced device lifespan.

[0005] On the other hand, existing technologies generally lack sufficient constraints on energy storage-side compatibility. Output fluctuations from fireplace waste heat extraction often occur on a second-level scale. Without a dedicated buffering and ripple absorption mechanism, power fluctuations will directly reflect the high-frequency fluctuations in the main battery's charging and discharging current. Under frequent pulse charging and discharging, the main battery is prone to problems such as increased temperature rise, increased internal resistance, and accelerated capacity decay. Simultaneously, the battery management unit may trigger current limiting or disconnection to protect the battery, further amplifying the probability of bus fluctuations and load power loss. While some solutions incorporate capacitors or small energy storage as parallel buffers, these often exist passively, lacking a quantitative allocation mechanism based on the battery's allowable ripple capacity. This makes it difficult to establish a stable and interpretable power sharing boundary between the battery's tolerable portion and the buffer's responsibility.

[0006] Furthermore, scenarios often exhibit different load priorities. For instance, critical loads such as communication equipment and lighting have high continuity requirements, while optional loads or inverter outputs can be connected only when there is sufficient power generation margin. Many existing systems only provide manual switching or simple threshold switch control, failing to coordinate decisions based on the combustion stage, available power generation capacity, energy storage status, and heat dissipation safety boundaries. This leads to problems such as optional loads being mistakenly connected, critical loads being de-energized, or users perceiving inflated power levels that are actually unusable when switching between the vigorous fire and ember stages, reducing system availability and user experience consistency. Summary of the Invention

[0007] The purpose of this invention is to provide an integrated fireplace power generation and energy storage system and its control method and system to solve the technical problems mentioned in the background art.

[0008] Based on the above ideas, the present invention provides the following technical solution:

[0009] A control method for an integrated fireplace power generation and energy storage system includes the following steps:

[0010] S1: The fireplace combustion generates heat, and the waste heat power generation unit absorbs heat at the hot end and outputs DC power.

[0011] S2: The temperature difference between the hot end and the cold end of the waste heat extraction power generation unit is established and maintained by the cold end heat dissipation unit, so that the waste heat extraction power generation unit is within a preset safe temperature range.

[0012] S3: During the control cycle, the voltage, current, open-circuit voltage, short-circuit current, hot end temperature, cold end temperature, flue temperature gradient, ambient temperature, and operating status of the waste heat extraction power generation unit are collected synchronously to form operating condition data.

[0013] S4: Based on the operating condition data, introduce a parameter set and calculate the available power generation capacity parameters to characterize the available power boundary that the system can continuously output in the next control cycle;

[0014] S5: Based on the operating condition data, introduce parameter groups and calculate the buffer absorption requirement parameters to characterize the power fluctuation requirements that need to be borne by the DC buffer unit under the charging and discharging friendly constraints defined by the main battery and battery management unit.

[0015] S6: Based on the available power generation capacity parameters and the buffer absorption requirement parameters, solve for the set of power supply and charging control strategies, and control the DC-DC converter unit, DC buffer unit and load-level power supply unit accordingly to achieve priority continuous power supply to key loads and suppress main battery current fluctuations.

[0016] By employing a closed-loop control chain that integrates waste heat extraction, cold-end heat dissipation, multi-source operating condition data acquisition, available power boundary estimation, buffer absorption demand assessment, and coordinated control of a set of strategies, the electrical fluctuations caused by fireplace combustion during the ignition and heating, fire stabilization, and ember decay stages become observable and controllable. This allows for prioritizing continuous power supply to critical loads such as communication and lighting without pursuing maximum instantaneous output, significantly reducing DC bus voltage flickering and load power outages. Simultaneously, it isolates second-level power fluctuations from the main battery side, reducing frequent pulse charging and discharging of the main battery, improving battery life and system availability, while also considering the cold-end temperature safety boundary, reducing the risks of overheating and heat dissipation failure.

[0017] Preferably, step S4 includes:

[0018] In each control cycle, the controller controls the DC-DC converter to perform open-circuit sampling and short-circuit sampling on the waste heat energy extraction power generation unit to obtain the open-circuit voltage and short-circuit current.

[0019] Calculate the rate of change of the open-circuit voltage and the rate of change of the short-circuit current, and calculate the cold junction thermal margin coefficient in combination with the cold junction temperature and the ambient temperature;

[0020] The available power generation capacity parameters are calculated based on the open-circuit voltage, the short-circuit current, the rate of change of the open-circuit voltage, the rate of change of the short-circuit current, and the cold-end thermal margin coefficient.

[0021] By sampling the waste heat extraction power generation unit in each control cycle using open-circuit / short-circuit parameters and combining the open-circuit voltage change rate, short-circuit current change rate, and cold-end thermal margin coefficient to calculate available power generation capacity parameters, the system achieves higher accuracy in identifying the current capacity and changing trends of the power generation unit. This allows for earlier identification of sudden changes in combustion conditions and heat dissipation capacity, avoiding misjudgments and lags caused by relying solely on real-time voltage and current. The cold-end thermal margin coefficient explicitly incorporates heat dissipation capacity into the control, making the power boundary estimation closer to the actual safe and usable range. This reduces the risk of overload damaging the hot end, causing voltage drop fluctuations, or excessive conservatism leading to wasted available power.

[0022] Preferably, the available power generation capacity parameters are obtained in the following manner:

[0023] Using the open-circuit voltage and short-circuit current of the current control cycle as the basic quantities, and combining the open-circuit voltage change rate and the short-circuit current change rate respectively, the open-circuit voltage and short-circuit current of the next control cycle are extrapolated to show trends.

[0024] Based on the extrapolated open-circuit voltage and short-circuit current, the theoretical available output capacity of the power generation unit in the next control cycle is obtained. The theoretical available output capacity is positively correlated with the product of the extrapolated open-circuit voltage and short-circuit current.

[0025] The cold end thermal margin coefficient is introduced to reduce the theoretical available output capacity to obtain the available power generation capacity parameter, so that the reduction is stronger when the cold end temperature is closer to the upper limit threshold of the cold end temperature and weaker when the cold end temperature is far from the upper limit threshold of the cold end temperature.

[0026] The cold end thermal margin coefficient is determined by the upper limit threshold of the cold end temperature and the relative difference between the current cold end temperature and the ambient temperature, and is limited to the range of 0 to 1.

[0027] By extrapolating the trends of open-circuit voltage, short-circuit current, and their rates of change for the next control cycle, and reducing the theoretical output capacity using a cold-end thermal margin coefficient, the available power generation capacity parameters reflect not only the output capacity on the electrical side but also the sustainable capacity allowed by cold-end heat dissipation. This method achieves equivalent coupling of the physical constraints between the hot and cold ends: when the cold-end temperature approaches its upper limit, the output capacity is automatically reduced, thereby mitigating the risk of degradation caused by long-term operation of the thermoelectric module / heat exchange interface under high thermal stress; when the cold-end margin is sufficient, the output capacity is released more fully, improving the effective power generation utilization rate and the system's continuous power supply capability.

[0028] Preferably, S5 includes:

[0029] The main battery's state of charge and temperature are obtained through the main battery and battery management unit, and the upper limit of the allowable ripple current of the main battery is determined based on the main battery's state of charge and temperature.

[0030] Based on the open-circuit voltage, the short-circuit current and its rate of change, calculate the predicted fluctuation of the output power of the waste heat extraction power generation unit in the next control cycle;

[0031] The predicted fluctuation amount is compared with the allowable power fluctuation amount determined by the upper limit of the allowable ripple current of the main battery, and the buffer absorption requirement parameter is calculated so that the main battery can charge and discharge under smooth current conditions and the DC buffer unit can handle the second-level power fluctuations.

[0032] By incorporating the main battery's state of charge and temperature, the upper limit of the allowable ripple current for the main battery is determined. The predicted fluctuations in power generation output are compared with the allowable power fluctuations of the main battery to obtain buffering and ripple absorption requirements, thus quantifying battery-friendly constraints. The direct effects are: limiting the main battery to operate under smoother charge and discharge current conditions, reducing heat generation, polarization, and lifespan loss caused by high-frequency charging and discharging; and enabling the DC buffer unit to handle second-level power fluctuations more suited to its characteristics, improving the steady-state power supply quality of the system under combustion fluctuation scenarios.

[0033] Preferably, the buffer absorption requirement parameters are obtained in the following manner:

[0034] Based on the open-circuit voltage and short-circuit current of the current control cycle, and combined with the open-circuit voltage change rate and the short-circuit current change rate, the available output capability of the next control cycle is predicted, thereby obtaining the predicted fluctuation amount.

[0035] The allowable power fluctuation of the main battery is determined by the main battery terminal voltage and the upper limit of the allowable ripple current of the main battery.

[0036] When the predicted fluctuation is greater than the allowable power fluctuation of the main battery, the difference between the two is determined as the buffer absorption requirement parameter; when the predicted fluctuation is not greater than the allowable power fluctuation of the main battery, the buffer absorption requirement parameter is determined to be zero.

[0037] The predicted fluctuation amount is determined by the absolute difference between the predicted output capability of the next control cycle and the output capability of the current control cycle.

[0038] By establishing a rule that buffering and absorbing power fluctuations only occur when the predicted fluctuation exceeds the allowable power fluctuation of the main battery, the intervention of the DC buffer unit becomes both necessary and boundary-based: it absorbs fluctuations only when they exceed the battery's tolerance range; otherwise, it does not absorb them or absorbs none. This mechanism avoids additional losses and device aging caused by long-term ineffective high-frequency operation of the buffer unit, reduces control oscillations and energy round trips, and improves overall energy efficiency and reliability. Simultaneously, it makes buffer capacity and control strategies easier to select in engineering, improving system maintainability and consistency.

[0039] Preferably, step S6 includes:

[0040] The upper limit of the power command of the DC-DC converter is limited based on the available power generation capacity parameters, and load reduction is triggered when the cold end temperature approaches the upper limit threshold of the cold end temperature to maintain heat dissipation safety; the charging and discharging commands of the DC buffer unit are adjusted based on the buffer absorption demand parameters so that the DC bus voltage is maintained within the set range and the main battery current ripple does not exceed the upper limit of the allowable ripple current.

[0041] Implement load-tiered power supply: critical loads are connected by default; optional loads are connected when combustion enters a stable, high-volume state and the main battery is in a rechargeable state; when combustion enters the ember decay stage, it switches to backup power supply and maintains the operation of heat dissipation loads.

[0042] By constraining the power command of the DC-DC converter unit with available power generation capacity parameters and triggering load descent when the cold end temperature approaches the upper limit threshold, active protection of the heat dissipation safety boundary is achieved. Combined with the scheduling of the DC buffer unit based on buffer absorption demand parameters, the DC bus voltage is kept stable and the main battery current ripple is controlled, thus achieving integrated voltage and power stabilization and battery protection on the power side. Furthermore, by linking load-level power supply with the combustion stage, optional loads are released during the stable phase of the fire, and backup power supply is provided while maintaining the operation of the heat dissipation load during the ember decay phase. This significantly reduces the user's perception of intermittent power outages and inflated power levels, while also avoiding the risk of heat accumulation caused by heat dissipation interruptions during the residual heat phase.

[0043] Preferably, the set of power supply and charging control strategies is obtained according to the following optimization criteria:

[0044] With the goal of minimizing the operating cost within the preset optimization time domain, the operating cost includes at least: the magnitude of the main battery current in the mean square sense, and the magnitude of the deviation of the DC bus voltage from the bus voltage set value in the mean square sense.

[0045] And simultaneously satisfy the following constraints:

[0046] The output power of the DC-DC converter unit on the DC bus side is not less than zero at any time and does not exceed the continuously output power boundary defined by the available power generation capacity parameters.

[0047] The variation in the output power of the DC-DC converter between adjacent control cycles does not exceed the absorption capability boundary defined by the buffer absorption requirement parameters.

[0048] The load-level power supply unit has a binary state for the connection status of each load, and the total power of the connected loads at any time does not exceed the output power that the DC-DC converter can provide on the DC bus side.

[0049] The critical load set meets the minimum guaranteed power requirement at any given time;

[0050] The output thus includes a set of control policies containing the following: power commands for the DC-DC converter, charge / discharge commands for the DC buffer unit, and connection / disconnect commands for each load.

[0051] By using the deviation between the main battery current intensity and the DC bus voltage as the main operational cost within a preset optimization time domain, and solving for the set of power supply and charging control strategies under available power boundaries, absorption boundaries, binary load access constraints, and minimum guarantee constraints for critical loads, control is no longer an isolated local rule, but a holistic coordinated decision that satisfies the constraints. The effects are: under the same power generation capacity, it further reduces the equivalent loss and temperature rise risk of the main battery, improves the stability of the bus voltage, and ensures the determinism of power supply to critical loads; in scenarios with strong combustion fluctuations, it can reduce repeated switching and oscillations caused by conflicting strategies, improving system predictability and long-term stability.

[0052] A fireplace power generation and energy storage integrated system, executing the aforementioned fireplace power generation and energy storage integrated control method, includes:

[0053] Waste heat extraction power generation unit, cold end heat dissipation unit, sensing and acquisition unit, DC-DC conversion unit, DC buffer unit, main battery and battery management unit, load hierarchical power supply unit and controller;

[0054] The waste heat energy extraction and power generation unit is installed in the heated area of ​​the fireplace body or flue and forms a hot end and a cold end with the cold end heat dissipation unit. The waste heat energy extraction and power generation unit is used to output DC power.

[0055] The input terminal of the DC-DC converter is electrically connected to the waste heat energy extraction and power generation unit, and the output terminal forms a DC bus; the DC buffer unit is bidirectionally electrically connected to the DC bus; the main battery and battery management unit are bidirectionally electrically connected to the DC bus; the load-level power supply unit is electrically connected to the DC bus and is used to perform hierarchical access and disconnection of critical loads and optional loads.

[0056] The sensing and acquisition unit is used to collect the voltage, current, open-circuit voltage and short-circuit current of the waste heat energy extraction and power generation unit, collect the hot end temperature, cold end temperature, flue temperature gradient and ambient temperature, and collect the operating status of the cold end heat dissipation unit to form operating condition data.

[0057] The controller is electrically connected to the sensing and acquisition unit to obtain the operating condition data, and is also electrically connected to the DC-DC converter, the DC-DC buffer unit, the main battery and battery management unit, and the load-level power supply unit to output control commands; wherein, the controller is configured as follows:

[0058] Based on the operating condition data, step S4 is performed to calculate the available power generation capacity parameters, and the available power generation capacity parameters are updated according to the defined sampling and calculation rules.

[0059] Based on the operating condition data and the main battery status provided by the main battery and the battery management unit, step S5 is executed to calculate the buffer absorption requirement parameters, and the buffer absorption requirement parameters are updated according to the defined calculation rules.

[0060] Based on the available power generation capacity parameters and the buffer absorption demand parameters, step S6 is executed, and the DC-DC converter unit, DC buffer unit and load-level power supply unit are coordinated and controlled according to load grading and bus stability control, and the power supply and charging control strategy set is output under the condition of satisfying the limited optimization criteria and constraints.

[0061] By structurally integrating the waste heat extraction power generation unit, cold-end heat dissipation unit, sensing and acquisition unit, DC-DC converter unit, DC buffer unit, main battery and battery management unit, load-level power supply unit, and controller, and enabling the controller to execute the aforementioned control logic, a one-to-one correspondence between the method and the system and a feasible closed loop are achieved. This system architecture solidifies key capabilities into hardware and interfaces: multi-source sensing ensures measurable operating conditions, DC-DC conversion and buffering ensure adjustable power, load-leveling ensures controllable power supply, and battery management ensures energy storage availability and safety control. Thus, under the strong safety constraints and highly fluctuating operating conditions of fireplaces, it balances continuous power supply experience, equipment lifespan, and safety boundaries, significantly improving the feasibility of project implementation.

[0062] The technical solution of the present invention may include the following beneficial effects:

[0063] This invention utilizes a closed-loop control link—including waste heat extraction, cold-end heat dissipation, multi-source operating condition data acquisition, available power generation capacity assessment, buffer absorption demand assessment, and tiered power supply and coordinated control—to online identify and manage the highly fluctuating operating conditions of a fireplace during its ignition and heating, fire stabilization, and ember decay stages. This prevents the power generation output from directly and randomly impacting the load and energy storage side. Consequently, it prioritizes continuous power supply to critical loads such as communication and lighting under conditions of strong combustion fluctuations, significantly reducing DC bus voltage interruptions, load power outages, and intermittent power supply perceived by users, thereby improving the system's availability and stability in home emergency and daily scenarios.

[0064] This invention introduces a constraint and buffering mechanism for battery life, prioritizing the handling of second-level power fluctuations by a DC buffer unit and limiting power fluctuations to the allowable ripple current of the main battery. This allows the main battery to operate more under smooth current conditions, reducing the risks of heat generation, polarization, and capacity decay caused by frequent pulse charging and discharging. Simultaneously, the usable power generation capacity assessment incorporates both the electrical output capacity and the cold-end heat dissipation margin, avoiding voltage drop jitter and ineffective charging and discharging caused by blindly pursuing instantaneous high power generation, thus improving effective energy utilization and overall system efficiency.

[0065] This invention explicitly integrates the cold-end temperature safety boundary and heat dissipation status into the control strategy. When the cold-end temperature approaches the upper threshold, it can proactively reduce the load while maintaining necessary heat dissipation load, reducing reliability risks caused by hot-end overheating, heat dissipation failure, and long-term thermal cycling. Furthermore, through a strategic load grading mechanism, selectable loads are opened in an orderly manner during the stable peak power phase, and the system automatically switches to a backup power supply mode during the decay phase, achieving a comprehensive balance between safety, lifespan, and user experience. The overall architecture also facilitates expansion with subsequent home energy management interfaces (such as linkage with photovoltaic systems and peak-valley electricity pricing), providing a more robust foundation for system engineering implementation and long-term maintainability. Attached Figure Description

[0066] Figure 1 This is a flowchart illustrating the workflow of an integrated fireplace power generation and energy storage system and its control method according to the present invention.

[0067] Figure 2 This is a system block diagram of an integrated fireplace power generation and energy storage system according to the present invention. Detailed Implementation

[0068] Example 1

[0069] A control method for an integrated fireplace power generation and energy storage system includes the following steps:

[0070] S1: The fireplace combustion generates heat, and the waste heat power generation unit absorbs heat at the hot end and outputs DC power.

[0071] S2: The temperature difference between the hot end and the cold end of the waste heat extraction power generation unit is established and maintained by the cold end heat dissipation unit, so that the waste heat extraction power generation unit is within a preset safe temperature range.

[0072] S3: During the control cycle, the voltage, current, open-circuit voltage, short-circuit current, hot end temperature, cold end temperature, flue temperature gradient, ambient temperature, and operating status of the waste heat extraction power generation unit are collected synchronously to form operating condition data.

[0073] S4: Based on the operating condition data, introduce a parameter set and calculate the available power generation capacity parameters to characterize the available power boundary that the system can continuously output in the next control cycle;

[0074] S5: Based on the operating condition data, introduce parameter groups and calculate the buffer absorption requirement parameters to characterize the power fluctuation requirements that need to be borne by the DC buffer unit under the charging and discharging friendly constraints defined by the main battery and battery management unit.

[0075] S6: Based on the available power generation capacity parameters and the buffer absorption requirement parameters, solve for the set of power supply and charging control strategies, and control the DC-DC converter unit, DC buffer unit and load-level power supply unit accordingly to achieve priority continuous power supply to key loads and suppress main battery current fluctuations.

[0076] In one possible implementation, the controller performs closed-loop control with a fixed control cycle, which can be selected from 0.5 to 5 seconds, preferably 1 second. Within each control cycle, the sensor acquisition unit collects the output voltage and output current of the waste heat extraction power generation unit, and obtains the open-circuit voltage and short-circuit current under the coordination of the controller. At the same time, it collects the hot end temperature, cold end temperature, flue temperature gradient, ambient temperature, and the operating status of the cold end heat dissipation unit (fan / pump speed or duty cycle, start / stop status). The original sampling frequency of voltage and current can be selected from 100 to 2000 Hz (preferably ≥200 Hz), and the sampling frequency of temperature and heat dissipation status can be selected from 1 to 10 Hz (preferably 2 Hz). The controller aligns the signals of different frequencies according to the timestamp and calculates statistical quantities such as "cycle mean, cycle peak-to-valley difference, and cycle standard deviation" as operating condition data within one control cycle. When the operating data enters the intermediate processing stage, the controller uses exponential moving average filtering on the electrical parameters (selectable time constant 2–10 control cycles, preferably 5), and clips peak values ​​according to "mean of the past 20 cycles ± 4 times the standard deviation"; it sets degradation for missing and abnormal data: if the cold end temperature is missing for more than 2 control cycles, the available power generation capacity parameter is set to zero and only the heat dissipation load and critical load are powered; if the voltage / current is missing for more than 2 control cycles, power tracking is stopped and the DC-DC converter output is limited to the minimum power supply. Subsequently, the controller calculates the available power boundary (available power generation capacity parameter) that can be continuously output in the next control cycle based on the operating data, as well as the power fluctuation requirement (buffer absorption requirement parameter) required by the DC buffer unit to meet the main battery charging and discharging friendly constraints, and solves the power supply and charging control strategy set accordingly. The strategy set includes at least the power command of the DC-DC converter, the charging and discharging command of the DC buffer unit, and the access / disconnect command of the load-level power supply unit; the controller prioritizes the continuous power supply of critical loads and keeps the main battery current ripple within the allowable range.

[0077] Specifically, step S4 includes:

[0078] In each control cycle, the controller controls the DC-DC converter to perform open-circuit sampling and short-circuit sampling on the waste heat energy extraction power generation unit to obtain the open-circuit voltage and short-circuit current.

[0079] Calculate the rate of change of the open-circuit voltage and the rate of change of the short-circuit current, and calculate the cold junction thermal margin coefficient in combination with the cold junction temperature and the ambient temperature;

[0080] The available power generation capacity parameters are calculated based on the open-circuit voltage, the short-circuit current, the rate of change of the open-circuit voltage, the rate of change of the short-circuit current, and the cold-end thermal margin coefficient.

[0081] In one possible implementation, open-circuit sampling is performed by the controller controlling the DC-DC converter to enter a high-resistance state or an equivalent open state on the input side, making the waste heat energy extraction power generation unit approximately open-circuited. The open-circuit sampling window can be selected as 10–200 ms (preferably 50 ms). Within the window, the open-circuit voltage sequence is collected and the first 10% of the transition samples are removed. The median of the remaining samples is taken as the open-circuit voltage for that control cycle. Short-circuit sampling is performed by the controller controlling the DC-DC converter to enter a controlled load current limiting mode, so that the input voltage is pulled down to within 5%–15% of the open-circuit voltage and the current under the current limiting steady state is recorded as the short-circuit current. The short-circuit sampling window can be selected as 5–100 ms (preferably 20 ms), and the short-circuit sampling current is limited to within 80%–120% of the rated short-circuit current of the waste heat energy extraction power generation unit (preferably not exceeding the rated value) to avoid transient overheating. The open-circuit voltage change rate and short-circuit current change rate are calculated using the sequence of the most recent N control cycles (N can be 3–20, preferably 10). A first-order differential averaging or linear regression slope can be selected, with linear regression slope preferred to improve noise immunity. The cold-end thermal margin coefficient is determined by the upper limit threshold of the cold-end temperature, the current cold-end temperature, and the ambient temperature. The upper limit threshold of the cold-end temperature can be selected as 70–120℃ (preferably 80–100℃ for air-cooled systems and 90–110℃ for water-cooled systems). The controller normalizes the "temperature margin of the cold end from the upper limit threshold" relative to the "difference between the upper limit threshold and the ambient temperature," and clips the result to the 0–1 range as the cold-end thermal margin coefficient. This coefficient is then used together with the open-circuit voltage, short-circuit current, and their change rates to calculate the available power generation capacity parameters.

[0082] Specifically, the available power generation capacity parameters are obtained from the following equations:

[0083]

[0084] in:

[0085] a=U oc (t) represents the open-circuit voltage measured during the current control cycle;

[0086] b=I sc (t) represents the short-circuit current measured in the current control cycle;

[0087] The open-circuit voltage change rate;

[0088] This represents the rate of change of short-circuit current.

[0089] Δt is the control period;

[0090] c is the cold junction heat margin coefficient, which satisfies:

[0091]

[0092] Where Tc T is the cold junction temperature. amb For ambient temperature, T c,max This is the upper limit threshold for the cold junction temperature. clip(⋅) indicates that the temperature is truncated to the interval between 0 and 1.

[0093] In one possible implementation, the power generation capacity parameter X can be calculated according to the formula given in the claim: where a is the open-circuit voltage (in V, typical range 5–60 V) measured in the current control cycle, and b is the short-circuit current (in A, typical range 0.5–20 A) measured in the current control cycle. Open-circuit voltage change rate (unit: V / s, typical range: -5 to +5 V / s). Δt is the rate of change of short-circuit current (unit: A / s, typical range: -5 to +5 A / s), Δt is the control period (unit: s, 0.5–5 s, preferably 1 s), and c is the cold-end thermal margin coefficient (dimensionless, 0–1). In the formula, "1 / 4" corresponds to the power estimation ratio of the waste heat extraction power generation unit when it approaches the maximum available power point under the equivalent Thevenin model; "and" "Used to extrapolate the first-order trend of the open-circuit voltage and short-circuit current for the next control cycle; c is used to map the cold-end heat dissipation margin to a sustainable output reduction factor, so that X characterizes the "available power boundary for continuous output in the next control cycle" (in W).

[0094] Specifically, S5 includes:

[0095] The main battery's state of charge and temperature are obtained through the main battery and battery management unit, and the upper limit of the allowable ripple current of the main battery is determined based on the main battery's state of charge and temperature.

[0096] Based on the open-circuit voltage, the short-circuit current and its rate of change, calculate the predicted fluctuation of the output power of the waste heat extraction power generation unit in the next control cycle;

[0097] The predicted fluctuation amount is compared with the allowable power fluctuation amount determined by the upper limit of the allowable ripple current of the main battery, and the buffer absorption requirement parameter is calculated so that the main battery can charge and discharge under smooth current conditions and the DC buffer unit can handle the second-level power fluctuations.

[0098] In one possible implementation, the upper limit d of the allowable ripple current of the main battery required for calculating the buffer absorption demand parameter Y is provided by the main battery and the battery management unit, or determined by the main battery state of charge (SOC) and main battery temperature output by the battery management unit. The SOC of the main battery can be obtained by combining coulomb measurement and open-circuit voltage estimation (output 0–100%), and the main battery temperature is the cell or casing temperature collected by the battery management unit (sampling frequency 1–5 Hz). d is preferably calculated using a two-dimensional lookup table: the value of d is mapped to the SOC segment (e.g., 0–20%, 20–80%, 80–100%) and the temperature segment (e.g., ≤0℃, 0–45℃, ≥45℃). The engineering range of d can be selected as the current corresponding to 0.02C–0.3C (e.g., 0.4–6 A for a 20 Ah battery). A smaller value is taken when the temperature is high or the SOC is close to full charge to protect the battery, and a larger value is taken when the temperature is moderate and the SOC is in the middle range to improve the available charging capacity. The controller calculates the predicted power value for the next control cycle based on the open-circuit voltage, short-circuit current, and their rate of change, and compares it with the current cycle's reference power estimate to obtain the predicted fluctuation amount. The reference power estimate can be selected as "one-quarter of the product of the open-circuit voltage and short-circuit current," consistent with the Y calculation. The controller then calculates the allowable power fluctuation amount of the main battery by multiplying the main battery terminal voltage Vb (in V, typically 10.5–14.6 V for a 12 V system) by d, which is used to determine the fluctuation demand that needs to be handled by the DC buffer unit.

[0099] Specifically, the buffer absorption requirement parameter Y is obtained from the following equation:

[0100]

[0101] Vb is the main battery terminal voltage; d is the upper limit of the main battery's allowable ripple current.

[0102] Y represents the condition that V is satisfied. bd The remaining power fluctuation demand that still needs to be absorbed by the DC buffer unit under the limited power fluctuation capability of the main battery.

[0103] In one possible implementation, the buffer absorption requirement parameter Y is calculated according to the formula given in the claim: the absolute value term in the formula is used to represent the power mutation amount between the predicted power of the next control cycle and the power estimate of the current cycle; "Vb·d" represents the upper limit of power fluctuation that the main battery can withstand under the constraint of the upper limit of the allowable ripple current d; max(0,⋅) is used to ensure that Y is zero when the predicted mutation amount does not exceed the upper limit of the battery, and Y is the excess part when it exceeds the upper limit.

[0104] Specifically, step S6 includes:

[0105] The upper limit of the power command of the DC-DC converter is limited based on the available power generation capacity parameters, and load reduction is triggered when the cold end temperature approaches the upper limit threshold of the cold end temperature to maintain heat dissipation safety; the charging and discharging commands of the DC buffer unit are adjusted based on the buffer absorption demand parameters so that the DC bus voltage is maintained within the set range and the main battery current ripple does not exceed the upper limit of the allowable ripple current.

[0106] Implement load-tiered power supply: critical loads are connected by default; optional loads are connected when combustion enters a stable, high-volume state and the main battery is in a rechargeable state; when combustion enters the ember decay stage, it switches to backup power supply and maintains the operation of heat dissipation loads.

[0107] In one implementation, the controller limits the output power command of the DC-DC converter bus side to between 0 and X in each control cycle, and triggers load descent when the cold-end temperature approaches the upper limit threshold of the cold-end temperature: triggering can be selected as "reaching 90%-100% of the upper limit threshold", preferably triggering at 95%, further tightening the upper limit of the power command according to the cold-end thermal margin coefficient, and prioritizing the power supply of heat dissipation loads and critical loads; when the cold-end temperature exceeds the upper limit threshold and lasts for more than 1 second, the controller converges the upper limit of the power command to a level that only supports the minimum guaranteed power of heat dissipation loads and critical loads, and disconnects optional loads. The controller uses Y to limit the power change rate: the absolute value of the difference between the DC-DC converter power commands of any two adjacent control cycles does not exceed Y, so that the power change is "split" into the part that the main battery can withstand and the part that the buffer unit can withstand; the charging and discharging command of the DC buffer unit is jointly determined by the bus voltage deviation and the "excess power", preferably with the bus voltage as the main control quantity maintained near the set value, and the buffer current is generated with the upper limit of the allowable ripple current of the main battery as a constraint. Load-level power supply is implemented in a binary manner: critical loads are connected by default; optional loads are allowed to be connected when the fire is determined to be in a stable phase and the main battery is in a rechargeable state; optional loads are automatically disconnected and backup power supply is activated when the embers decay phase is entered, while heat dissipation loads are kept working to meet thermal safety boundaries.

[0108] Specifically, the set of power supply and charging control strategies is obtained by the following optimization equations.

[0109]

[0110] The constraints are satisfied:

[0111]

[0112]

[0113]

[0114]

[0115]

[0116] in:

[0117] U={P dc (τ), I buf (τ), s1(τ),…,s n (τ)} represents the set of strategies to be determined;

[0118] X(τ) is the available power generation capacity parameter, and Y(τ) is the buffer absorption requirement parameter;

[0119] I b (τ) is the main battery current, V dc (τ) is the DC bus voltage, V ref This is the DC bus voltage setting value;

[0120] I buf (τ) represents the charging and discharging current of the DC buffer unit;

[0121] P dc (τ) represents the output power of the DC-DC converter unit on the DC bus side;

[0122] P i Let P be the rated power of the i-th load; C be the set of critical loads; P be the rated power of the i-th load. C The minimum guaranteed power for critical loads; T is the optimized time domain length, and Δt is the control period.

[0123] I ref This represents the normalized reference value for the main battery current.

[0124] ΔV ref This indicates the reference value for the allowable voltage deviation of the DC bus, in units of V.

[0125] In one possible implementation, the controller solves the optimization problem given in the claim in discrete form: it is discretized into N steps over a control period Δt with a preset optimization time domain length T (optionally 5–30 s, preferably 10 s). The decision variables include at least the DC-DC converter bus-side output power, DC buffer unit charging and discharging current, and load connection status at each step; wherein the load connection status is a binary variable, and the key load set must meet the minimum guaranteed power at any given time. The objective function includes the square term of the main battery current and the square term of the bus voltage deviation; to ensure that the two terms can be directly added and that the "weight coefficients are clearly derived without introducing additional limitations", this implementation adopts unit normalization to achieve equal weighting: the main battery current is divided by the upper limit of the main battery's allowable ripple current or the battery's rated current, and the bus voltage deviation is divided by the allowable deviation bandwidth (e.g., ±0.5–±1.0 V), so that both terms are converted to dimensionless quantities before being squared and integrated (or discretely summed), thereby allowing the implicit weight to be 1 without adding additional weight parameters to the formula. Constraints are applied item by item according to the claims: the output power at each step does not exceed X of that step; the power change between adjacent steps does not exceed Y of that step; the total power of the connected loads does not exceed the output power; and the minimum guaranteed power of the critical loads is always met. The solution method can be selected as follows: a finite enumeration of optional load combinations (e.g., no more than 16–64 combinations), solving a continuous quadratic programming problem for each combination and calculating the cost, selecting the strategy set with the minimum cost that satisfies the constraints as the output strategy set; if the solution times out or there is no feasible solution, the approach is immediately downgraded to disconnecting optional loads, taking a conservative lower bound for the output power, and prioritizing voltage regulation in the buffer unit to ensure the continuity of the critical loads and that the safety constraints are not violated. The output strategy set is then applied to: the power command of the DC-DC converter unit, the charging and discharging current command of the DC buffer unit, and the switching command of the load-level power supply unit, thereby completing the online control closed loop defined by the claims constraints at the execution level.

[0126] A fireplace power generation and energy storage integrated system, executing the aforementioned fireplace power generation and energy storage integrated control method, includes:

[0127] Waste heat extraction power generation unit, cold end heat dissipation unit, sensing and acquisition unit, DC-DC conversion unit, DC buffer unit, main battery and battery management unit, load hierarchical power supply unit and controller;

[0128] The waste heat energy extraction and power generation unit is installed in the heated area of ​​the fireplace body or flue and forms a hot end and a cold end with the cold end heat dissipation unit. The waste heat energy extraction and power generation unit is used to output DC power.

[0129] The input terminal of the DC-DC converter is electrically connected to the waste heat energy extraction and power generation unit, and the output terminal forms a DC bus; the DC buffer unit is bidirectionally electrically connected to the DC bus; the main battery and battery management unit are bidirectionally electrically connected to the DC bus; the load-level power supply unit is electrically connected to the DC bus and is used to perform hierarchical access and disconnection of critical loads and optional loads.

[0130] The sensing and acquisition unit is used to collect the voltage, current, open-circuit voltage and short-circuit current of the waste heat energy extraction and power generation unit, collect the hot end temperature, cold end temperature, flue temperature gradient and ambient temperature, and collect the operating status of the cold end heat dissipation unit to form operating condition data.

[0131] The controller is electrically connected to the sensing and acquisition unit to obtain the operating condition data, and is also electrically connected to the DC-DC converter, the DC-DC buffer unit, the main battery and battery management unit, and the load-level power supply unit to output control commands; wherein, the controller is configured as follows:

[0132] Based on the operating condition data, step S4 is performed to calculate the available power generation capacity parameters, and the available power generation capacity parameters are updated according to the defined sampling and calculation rules.

[0133] Based on the operating condition data and the main battery status provided by the main battery and the battery management unit, step S5 is executed to calculate the buffer absorption requirement parameters, and the buffer absorption requirement parameters are updated according to the defined calculation rules.

[0134] Based on the available power generation capacity parameters and the buffer absorption demand parameters, step S6 is executed, and the DC-DC converter unit, DC buffer unit and load-level power supply unit are coordinated and controlled according to load grading and bus stability control, and the power supply and charging control strategy set is output under the condition of satisfying the limited optimization criteria and constraints.

Claims

1. A control method for an integrated fireplace power generation and energy storage system, characterized in that, Includes the following steps: S1: The fireplace combustion generates heat, and the waste heat power generation unit absorbs heat at the hot end and outputs DC power. S2: The temperature difference between the hot end and the cold end of the waste heat extraction power generation unit is established and maintained by the cold end heat dissipation unit, so that the waste heat extraction power generation unit is within a preset safe temperature range. S3: During the control cycle, the voltage, current, open-circuit voltage, short-circuit current, hot end temperature, cold end temperature, flue temperature gradient, ambient temperature, and operating status of the waste heat extraction power generation unit are collected synchronously to form operating condition data. S4: Based on the operating condition data, introduce a parameter set and calculate the available power generation capacity parameters to characterize the available power boundary that the system can continuously output in the next control cycle; S5: Based on the operating condition data, introduce parameter groups and calculate the buffer absorption requirement parameters to characterize the power fluctuation requirements that need to be borne by the DC buffer unit under the charging and discharging friendly constraints defined by the main battery and battery management unit. S6: Based on the available power generation capacity parameters and the buffer absorption demand parameters, solve for the set of power supply and charging control strategies, and control the DC-DC converter unit, DC buffer unit and load-level power supply unit accordingly to achieve priority continuous power supply to key loads and suppress main battery current fluctuations. Step S4 includes: In each control cycle, the controller controls the DC-DC converter to perform open-circuit sampling and short-circuit sampling on the waste heat energy extraction power generation unit to obtain the open-circuit voltage and short-circuit current. Calculate the open-circuit voltage change rate and the short-circuit current change rate, and calculate the cold junction thermal margin coefficient in combination with the cold junction temperature and the ambient temperature; The available power generation capacity parameters are calculated based on the open-circuit voltage, the short-circuit current, the rate of change of the open-circuit voltage, the rate of change of the short-circuit current, and the cold-end heat margin coefficient. The available power generation capacity parameters are obtained in the following manner: Using the open-circuit voltage and short-circuit current of the current control cycle as the basic quantities, and combining the open-circuit voltage change rate and the short-circuit current change rate respectively, the open-circuit voltage and short-circuit current of the next control cycle are extrapolated to show trends. Based on the extrapolated open-circuit voltage and short-circuit current, the theoretical available output capacity of the power generation unit in the next control cycle is obtained. The theoretical available output capacity is positively correlated with the product of the extrapolated open-circuit voltage and short-circuit current. The cold end thermal margin coefficient is introduced to reduce the theoretical available output capacity to obtain the available power generation capacity parameter, so that the reduction is stronger when the cold end temperature is closer to the upper limit threshold of the cold end temperature and weaker when the cold end temperature is far from the upper limit threshold of the cold end temperature. The cold end thermal margin coefficient is determined by the upper limit threshold of the cold end temperature and the relative difference between the current cold end temperature and the ambient temperature, and is limited to the range of 0 to 1. The available power generation capacity parameters are obtained from the following equations: in: a=U oc (t) represents the open-circuit voltage measured during the current control cycle; b=I sc (t) represents the short-circuit current measured in the current control cycle; The open-circuit voltage change rate; This represents the rate of change of short-circuit current. Δt is the control period; c is the cold junction heat margin coefficient, which satisfies: Where T c T is the cold junction temperature. amb For ambient temperature, T c,max This is the upper limit threshold for the cold junction temperature. clip(⋅) indicates that the temperature is truncated to the interval between 0 and 1.

2. The control method for an integrated fireplace power generation and energy storage system according to claim 1, characterized in that, S5 includes: The main battery's state of charge and temperature are obtained through the main battery and battery management unit, and the upper limit of the allowable ripple current of the main battery is determined based on the main battery's state of charge and temperature. Based on the open-circuit voltage, the short-circuit current and its rate of change, calculate the predicted fluctuation of the output power of the waste heat extraction power generation unit in the next control cycle; The predicted fluctuation amount is compared with the allowable power fluctuation amount determined by the upper limit of the allowable ripple current of the main battery, and the buffer absorption requirement parameter is calculated so that the main battery can charge and discharge under smooth current conditions and the DC buffer unit can handle the second-level power fluctuations.

3. The control method for an integrated fireplace power generation and energy storage system according to claim 2, characterized in that, The buffer absorption requirement parameters are obtained in the following way: Based on the open-circuit voltage and short-circuit current of the current control cycle, and combined with the open-circuit voltage change rate and the short-circuit current change rate, the available output capability of the next control cycle is predicted, thereby obtaining the predicted fluctuation amount. The allowable power fluctuation of the main battery is determined by the main battery terminal voltage and the upper limit of the allowable ripple current of the main battery. When the predicted fluctuation is greater than the allowable power fluctuation of the main battery, the difference between the two is determined as the buffer absorption requirement parameter; when the predicted fluctuation is not greater than the allowable power fluctuation of the main battery, the buffer absorption requirement parameter is determined to be zero. The predicted fluctuation amount is determined by the absolute difference between the predicted output capability of the next control cycle and the output capability of the current control cycle.

4. The control method for an integrated fireplace power generation and energy storage system according to claim 3, characterized in that, Step S6 includes: The upper limit of the power command of the DC-DC converter is limited based on the available power generation capacity parameters, and load derating is triggered when the cold end temperature approaches the upper limit threshold of the cold end temperature to maintain heat dissipation safety; the charging and discharging commands of the DC buffer unit are adjusted based on the buffer absorption demand parameters to keep the DC bus voltage within the set range and the main battery current ripple does not exceed the upper limit of the allowable ripple current; load-level power supply is implemented: critical loads are connected by default; optional loads are connected when combustion is detected to enter a stable and vigorous state and the main battery is in a rechargeable state; when combustion is detected to enter the ember decay stage, the power supply is switched to the backup power supply and the heat dissipation load is maintained.

5. The control method for an integrated fireplace power generation and energy storage system according to claim 4, characterized in that, The set of power supply and charging control strategies is obtained according to the following optimization criteria: With the goal of minimizing the operating cost within the preset optimization time domain, the operating cost includes at least: the magnitude of the main battery current in the mean square sense, and the magnitude of the deviation of the DC bus voltage from the bus voltage set value in the mean square sense. And simultaneously satisfy the following constraints: The output power of the DC-DC converter unit on the DC bus side is not less than zero at any time and does not exceed the continuously output power boundary defined by the available power generation capacity parameters. The variation in the output power of the DC-DC converter between adjacent control cycles does not exceed the absorption capability boundary defined by the buffer absorption requirement parameters. The load-level power supply unit has a binary state for the connection status of each load, and the total power of the connected loads at any time does not exceed the output power that the DC-DC converter can provide on the DC bus side. The critical load set meets the minimum guaranteed power requirement at any given time; The output thus includes a set of control policies containing the following: power commands for the DC-DC converter, charge / discharge commands for the DC buffer unit, and connection / disconnect commands for each load.

6. A fireplace power generation and energy storage integrated system, characterized in that: The fireplace power generation and energy storage integrated control method as described in any one of claims 1-5 includes: Waste heat extraction power generation unit, cold end heat dissipation unit, sensing and acquisition unit, DC-DC conversion unit, DC buffer unit, main battery and battery management unit, load hierarchical power supply unit and controller; The waste heat energy extraction and power generation unit is installed in the heated area of ​​the fireplace body or flue and forms a hot end and a cold end with the cold end heat dissipation unit. The waste heat energy extraction and power generation unit is used to output DC power. The input terminal of the DC-DC converter is electrically connected to the waste heat energy extraction and power generation unit, and the output terminal forms a DC bus; the DC buffer unit is bidirectionally electrically connected to the DC bus; the main battery and battery management unit are bidirectionally electrically connected to the DC bus; the load-level power supply unit is electrically connected to the DC bus and is used to perform hierarchical access and disconnection of critical loads and optional loads. The sensing and acquisition unit is used to collect the voltage, current, open-circuit voltage and short-circuit current of the waste heat energy extraction and power generation unit, collect the hot end temperature, cold end temperature, flue temperature gradient and ambient temperature, and collect the operating status of the cold end heat dissipation unit to form operating condition data. The controller is electrically connected to the sensing and acquisition unit to obtain the operating condition data, and is also electrically connected to the DC-DC converter, the DC-DC buffer unit, the main battery and battery management unit, and the load-level power supply unit to output control commands; wherein, the controller is configured as follows: Based on the operating condition data, step S4 is performed to calculate the available power generation capacity parameters, and the available power generation capacity parameters are updated according to the defined sampling and calculation rules. Based on the operating condition data and the main battery status provided by the main battery and the battery management unit, step S5 is executed to calculate the buffer absorption requirement parameters, and the buffer absorption requirement parameters are updated according to the defined calculation rules. Based on the available power generation capacity parameters and the buffer absorption demand parameters, step S6 is executed, and the DC-DC converter unit, DC buffer unit and load-level power supply unit are coordinated and controlled according to load grading and bus stability control, and the power supply and charging control strategy set is output under the condition of satisfying the limited optimization criteria and constraints.

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