A building modular light storage micro-grid and air source heat pump switching control method

Abstract

The present application relates to the technical field of green building clean energy, and particularly relates to a building modular photovoltaic energy storage micro-grid and air source heat pump switching control method, a temperature trend signal is generated by continuously monitoring the outdoor temperature change direction, which is used as a leading representation of building heat load change, combined with photovoltaic state, energy storage state and power grid state to determine the target switching mode, so that the switching decision can predict the heat load dynamics, avoid frequent switching caused by only relying on energy itself, realize the precise alignment of switching demand and heating demand, and finally, according to the outdoor temperature change, the verification opportunity is identified after the switching is completed, the switching verification is triggered only when the outdoor temperature changes effectively, through the double inspection of current-temperature correlation and voltage stability, the system after switching has dynamic response capability, the problem of unreliable static verification is solved, and the switching effect can withstand the test of actual working condition changes.

Description

Technical Field

[0001] This invention relates to the field of green building and clean energy technology, specifically to a method for switching control between a modular photovoltaic energy storage microgrid and an air source heat pump for buildings. Background Technology

[0002] Buildings are the primary energy consumers, especially in frigid regions where heating energy consumption accounts for a high proportion and carbon emissions are significant. Against this backdrop, photovoltaic-storage microgrids, which combine photovoltaic power generation with energy storage, offer a cleaner alternative to grid power. Their synergistic application with air-source heat pumps can promote the decarbonization of building heating systems, becoming a development direction for green buildings in frigid regions.

[0003] Although solar-storage microgrids have advantages such as being clean and renewable, their output is intermittent and fluctuates due to factors such as weather and day / night cycles. A single solar-storage system cannot independently meet the heating needs of a building and requires coordinated switching with the grid power.

[0004] However, existing switching control technologies rely solely on whether the energy source meets the power requirements of the air source heat pump, neglecting the dynamic changes in building heat load. Building heat load primarily stems from heat transfer due to indoor-outdoor temperature differences. When outdoor temperature changes, the building heat load changes accordingly, and the real-time power demand of the heat pump fluctuates. In this situation, even if the energy source meets the switching conditions, if the building heat load has changed significantly, there may still be a mismatch between actual heating demand and energy supply, easily leading to insufficient heating capacity or energy waste after switching.

[0005] Furthermore, current solar-energy storage-heat pump co-operation solutions often assume a successful switchover after completion. Even if a switchover verification is performed, it is limited to checking the electrical parameters at the moment of switchover. Such checks are difficult to reflect the system's responsiveness to dynamic heating demands when the building's heat load fluctuates, resulting in unreliable verification results that cannot withstand the test of actual operating conditions. Summary of the Invention

[0006] To solve the above-mentioned technical problems, or at least partially solve them, the present invention provides a method for switching control between a modular photovoltaic-storage microgrid and an air-source heat pump for buildings.

[0007] The objective of this invention can be achieved through the following technical solution: a method for switching control between a modular photovoltaic-storage microgrid and an air-source heat pump for buildings, comprising: real-time acquisition of photovoltaic output power, heat pump input power, remaining energy storage power, and grid voltage and frequency; comparison of the acquired data with corresponding reference values; determination of photovoltaic status as sufficient, insufficient, or lacking; classification of energy storage status as sufficient, critical, or scarce; and determination of grid status as normal or abnormal.

[0008] A temperature trend signal is generated based on the direction of outdoor temperature change, and a switching lock signal is generated based on the operating time of the heat pump compressor.

[0009] The target switching mode is determined by combining and matching photovoltaic status, energy storage status, grid status and temperature trend signals, and the switching conditions are determined to be met after the switching lock signal is released.

[0010] In response to the fulfillment of switching conditions, the voltage waveforms of the current power supply branch and the target power supply branch are monitored for zero-crossing identification. Switching is triggered when the two voltages cross zero synchronously.

[0011] After the switch is completed, the verification timing is identified based on the change in outdoor temperature. When the verification timing is reached, the switch verification of current-temperature correlation and voltage stability is triggered.

[0012] Combining all the above technical solutions, the positive effects of this invention are as follows: 1. This invention generates a temperature trend signal by continuously monitoring the direction of outdoor temperature change, and uses it as a leading indicator of changes in building heat load. It combines and matches this signal with the photovoltaic status, energy storage status, and grid status to determine the target switching mode, enabling the switching decision to predict the dynamics of heat load and avoid frequent switching caused by relying solely on the energy itself. This achieves alignment between switching needs and heating needs, thereby ensuring heating continuity and preventing premature depletion of energy storage capacity.

[0013] 2. This invention generates a switching lock signal based on the operating time of the heat pump compressor, and prohibits switching requests within the shortest operating time after the compressor starts, thereby avoiding mechanical damage and electrical shock to the compressor caused by frequent switching of power supply modes and extending the service life of the heat pump.

[0014] 3. After the switch is completed, the present invention identifies the verification timing based on the change in outdoor temperature. The switch verification is only triggered when the outdoor temperature changes effectively. By verifying the current-temperature correlation and voltage stability, the present invention ensures that the system after the switch has dynamic response capability, solves the problem of unreliable static verification, and makes the switch effect withstand the test of actual operating conditions. Attached Figure Description

[0015] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0016] Figure 1 This is a diagram illustrating the method steps of the present invention;

[0017] Figure 2 This is a flowchart illustrating the implementation of identifying verification timing in this invention;

[0018] Figure 3This is a flowchart illustrating the implementation of the switching verification process in this invention. Detailed Implementation

[0019] 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.

[0020] See Figure 1 As shown, the present invention proposes a method for switching control between a modular photovoltaic-storage microgrid and an air source heat pump for buildings, including the following steps: S1, real-time acquisition of photovoltaic output power, heat pump input power, remaining energy storage power and grid voltage frequency, comparison of the acquired data with corresponding reference values, determination of photovoltaic status as sufficient, insufficient or missing, classification of energy storage status as sufficient, critical or scarce, and determination of grid status as normal or abnormal.

[0021] Heating has long dominated building energy consumption, especially in cold regions where winter heating demand is high and lasts for extended periods. Therefore, air-source heat pumps are widely used as heating equipment. Considering that photovoltaic (PV) power generation is clean and renewable but intermittent and highly volatile, achieving green power supply for heat pumps requires combining PV power generation with energy storage to form a PV-storage microgrid to power the heat pumps. However, PV output is affected by weather and day / night cycles, and cannot continuously meet the real-time power demands of the heat pumps. Therefore, it is necessary to switch power supply modes in real-time based on the status of PV, energy storage, and the power grid to ensure stable operation of the heat pumps.

[0022] The primary task in switching control is to acquire the current status of each energy source in real time, providing a reliable basis for subsequent mode selection. Photovoltaic output power, heat pump input power, remaining energy storage capacity, and grid voltage and frequency are selected as status characterization parameters because these four parameters determine the system's supply and demand balance capability: photovoltaic output power represents the real-time supply capacity of clean energy, heat pump input power reflects current load demand, remaining energy storage capacity determines the margin for supplementary regulation, and grid voltage and frequency indicate the reliability of external power supply. Based on these parameters, the status of each energy source can be quantified as follows: S11, Photovoltaic Status Determination.

[0023] Considering that photovoltaic output is intermittent and fluctuating, relying solely on instantaneous power can easily lead to frequent state changes. Therefore, this invention introduces a trend-assisted determination, as follows: the photovoltaic state is determined to be sufficient when any of the following conditions are met: 1) the photovoltaic output power is greater than the heat pump input power and the difference between the two exceeds the margin, where the margin can be set to 10% of the heat pump's rated input power.

[0024] The above conditions reflect that the photovoltaic output has significantly exceeded the current heat pump demand, not only fully meeting the load, but also having surplus capacity to charge energy storage, which can effectively avoid misjudgment of the status caused by small power fluctuations.

[0025] 2) The photovoltaic output power is greater than or equal to the heat pump input power and the photovoltaic output power increases at multiple consecutive sampling times.

[0026] The above conditions reflect that although the photovoltaic output is currently only slightly higher than or equal to the heat pump demand, the output is in the process of continuous enhancement and will be more abundant in the future. Judging it as abundant in advance can enable the system to switch to photovoltaic power supply mode as early as possible and reduce unnecessary switching later.

[0027] When the output power of the photovoltaic system is less than the input power of the heat pump, the photovoltaic system is considered to be inadequate, meaning that the photovoltaic power cannot independently meet the heat pump's demand and requires energy storage or grid supplementation.

[0028] When the photovoltaic output power is lower than the minimum operating power of the photovoltaic array, the photovoltaic status is determined to be missing, which means that there is almost no photovoltaic output and the photovoltaic system needs to rely on energy storage or grid power.

[0029] S12, Energy storage status determination.

[0030] The remaining energy storage capacity is compared with preset high and low energy thresholds. The high energy threshold is generally set at 80% to 90% of the rated capacity to ensure that the energy storage has the ability to continue charging. The low energy threshold is generally set at 20% to 30% to reserve emergency discharge capacity and prevent over-discharge from damaging the battery.

[0031] When the remaining power is higher than the high power threshold, the energy storage status is determined to be sufficient, meaning that the energy storage can undertake the discharge task.

[0032] When the remaining power is between the high and low thresholds, the energy storage state is determined to be critical, meaning that the energy storage can be discharged appropriately when needed.

[0033] When the remaining power is below the low power threshold, the energy storage state is determined to be scarce, which means that the energy storage should stop discharging and switch to charging state as soon as possible to avoid over-discharge.

[0034] S13, Power grid status determination.

[0035] The voltage and frequency of the power grid are compared with the normal operating range, which can be obtained from the State Grid technical specifications or equipment nameplate parameters.

[0036] When both voltage and frequency are within the normal operating range, the power grid is considered to be in normal condition, indicating that the mains power is available and can be used as a backup or auxiliary power source.

[0037] When either voltage or frequency exceeds the normal operating range, the power grid is deemed abnormal, indicating that the mains power quality is substandard. In this case, it is necessary to rely on photovoltaic and energy storage power supply.

[0038] S2. Generate a temperature trend signal based on the direction of outdoor temperature change, and generate a switching lock signal based on the operating time of the heat pump compressor.

[0039] After obtaining the status of various energy sources, this invention considers that the building's heat load is not constant but changes in real time with fluctuations in outdoor temperature. If switching decisions are made solely based on the status of photovoltaic, energy storage, and the power grid, it is impossible to predict the upcoming increase or decrease in heat load, which may lead to a mismatch between the switched power supply mode and actual demand. Therefore, this invention introduces the direction of outdoor temperature change as a leading signal of heat load trend.

[0040] As a specific embodiment of the present invention, the temperature trend signal is generated according to the following process.

[0041] The outdoor temperature is continuously collected, and the temperature at the current collection time is subtracted from the temperature at the previous collection time to obtain the temperature change between adjacent collection times. The direction of temperature change is determined by the sign of the temperature change, where positive means rising, negative means falling, and zero means unchanged.

[0042] If the temperature change of each sampling point relative to the previous sampling point is positive within a continuous sampling period, it is determined to be a warming trend, indicating that the building's heat load will gradually decrease and the heat pump power demand will tend to decrease.

[0043] If the temperature change at each sampling point relative to the previous sampling point is negative, it is determined to be a cooling trend, indicating that the heat load will gradually increase and the power demand of the heat pump will tend to rise.

[0044] If the absolute values ​​of all temperature changes are less than the stability limit, it is judged as a stable trend, indicating that the outdoor temperature does not change significantly and the heat load is basically constant.

[0045] In practice, the sampling duration can be adjusted according to the climate characteristics of the building's location: when the outdoor temperature changes gradually, the sampling duration can be appropriately extended to eliminate interference from short-term random fluctuations; when the outdoor temperature changes drastically, the sampling duration can be appropriately shortened to quickly capture the temperature change trend. For example, the sampling duration can be set to a value between 10 minutes and 30 minutes.

[0046] The stability limit is used to define whether the temperature has changed, and it is usually taken as 0.5℃ to 1.0℃.

[0047] By introducing the direction of outdoor temperature change as a leading signal of heat load trend, the direction of heat load increase or decrease can be predicted, thereby optimizing the selection of switching modes. However, simply predicting the heat load trend is insufficient to solve the equipment protection problem during the switching process. The compressor of an air source heat pump is a sensitive load. In the initial operation phase after startup, the lubricating oil has not yet fully circulated to all friction pairs, and the pipeline pressure has not yet fully stabilized. If the power supply source is frequently switched during this phase, the compressor will be subjected to additional electrical shocks and mechanical stresses, shortening the compressor's lifespan.

[0048] To this end, the present invention further generates a switching lock signal based on the running time of the heat pump compressor, prohibiting switching requests for a period of time after the compressor starts up, thereby providing physical protection for the compressor. The specific implementation is as follows: the operating current is detected in the power supply circuit of the heat pump compressor. When the compressor starts, the instantaneous value of the starting current usually reaches 5 to 7 times the rated current, and then drops rapidly and tends to stabilize. When the operating current is detected to drop from the starting peak to the rated current, it is determined that the compressor has switched from the starting state to the stable operating state. At this time, the starting timer starts to accumulate the continuous running time of the compressor. After the heat pump stops, the timer is automatically reset to zero.

[0049] When the cumulative duration is less than the minimum running time, the output lockout level is high, blocking all switching requests. The purpose is to prevent any power supply mode switching operation and ensure that the compressor is not disturbed during the initial lubrication establishment and pressure stabilization process.

[0050] When the cumulative duration reaches or exceeds the minimum running time, the lockout level is released, allowing subsequent switching condition judgment and switching execution.

[0051] The shortest running time mentioned above can be set according to the start-up protection requirements in the compressor technical manual, which is usually 60 to 180 seconds.

[0052] S3. Determine the target switching mode by combining and matching the photovoltaic status, energy storage status, grid status and temperature trend signals, and determine that the switching conditions are met after the switching lock signal is released.

[0053] After obtaining the photovoltaic status, energy storage range, grid status and temperature trend signals through the aforementioned steps, the switching mode can be determined. Since each state quantity is a discrete signal, the present invention adopts a combination matching method to directly map to the target power supply mode. The specific determination rules are as follows: (1) Photovoltaic power supply mode.

[0054] When the photovoltaic status is sufficient, it means that the photovoltaic output can meet the current needs of the heat pump. Regardless of the energy storage status, grid status, and temperature trend, the photovoltaic power supply alone can fully meet the needs. In this case, the photovoltaic power supply mode is selected, and the photovoltaic system supplies power to the heat pump alone. The excess electricity can be used to charge the energy storage, maximizing the utilization rate of clean energy.

[0055] (2) Photovoltaic-storage synergistic mode.

[0056] When the photovoltaic power is insufficient, the energy storage power is sufficient, the grid power is normal, and the temperature trend signal is not cooling down (i.e., heating up or stabilizing), it indicates that although the photovoltaic power is insufficient to independently meet the heat pump demand, it still has some output, and the energy storage has the ability to discharge. At the same time, the heat load will not increase in the short term, and the energy storage discharge to make up for the difference is of practical significance.

[0057] In this case, the photovoltaic-storage synergistic mode is selected, with photovoltaic power providing basic power supply and energy storage supplementing the difference. This prioritizes the consumption of photovoltaic power and reduces dependence on grid power.

[0058] (3) Energy storage power supply mode.

[0059] When the photovoltaic (PV) status is absent, the energy storage status is sufficient, and the grid status is abnormal, it indicates that there is no PV output, the mains power is unavailable, and only the energy storage can provide power. In this case, there is no need to consider temperature trends; the energy storage power supply mode can be directly selected, with the energy storage independently supplying power to the heat pump to ensure continuous heating.

[0060] (4) Mains power standby mode.

[0061] Scenario 1: When the photovoltaic (PV) status is insufficient, the energy storage status is sufficient, the grid status is normal, and the temperature trend signal indicates a cooling trend, it means that although the PV power is insufficient to independently meet the heat pump's demand, the energy storage has discharge capabilities. However, the future heat load will continue to increase. If the PV-energy storage synergy mode is adopted at this time, it will consume the energy storage power, leading to insufficient energy storage when the load increases later. Therefore, the grid backup mode should be prioritized, with the grid supplying power to the heat pump and reserving energy storage power to cope with the larger heat load in the future.

[0062] Scenario 2: When energy storage is scarce and the grid is normal, regardless of the photovoltaic status or temperature trend, priority should be given to protecting energy storage from deep discharge. In this case, the grid backup mode should be selected, with the grid supplying power to the heat pump, while the grid can be used to charge the energy storage.

[0063] The above rules cover the main operating conditions of the system. For state combinations not explicitly listed, the system will maintain the current power supply mode by default to avoid unnecessary switching.

[0064] It should be noted that when the target switching mode determined by the combination matching is the same as the current power supply mode, the switching action is not triggered, and the current mode is maintained.

[0065] After determining the target switching mode, considering that the switching lock signal of the heat pump compressor may fluctuate or bounce back at the moment of level change, in order to avoid system malfunction, the switching is not performed immediately, but the switching condition is determined only after the lock signal is stably released. The specific implementation is as follows: the level status of the switching lock signal is monitored in real time. When the signal is detected to jump from the lock level to the release level, a delay timer of fixed duration is started, such as 100 milliseconds.

[0066] During the operation of the delay timer, the lock signal is continuously monitored to see if the lock level reappears. If the lock signal remains at the unlock level throughout the entire delay period without any rebound of the lock level, the switching condition is officially determined to be met when the timer returns to zero, and subsequent switching execution is allowed.

[0067] If the lock level is detected to reappear during the delay period, it indicates signal jitter or the compressor has re-entered the lock state. In this case, the current timing will be terminated, the current switching preparation will be abandoned, and the system will wait for the next valid transition of the lock signal.

[0068] The aforementioned anti-jitter confirmation mechanism ensures that the switching conditions are met only when the signal is truly stable and released.

[0069] S4. In response to the fulfillment of the switching conditions, monitor the voltage waveforms of the current power supply branch and the target power supply branch to identify the zero-crossing point. When the two voltages cross the zero point synchronously, the switching is triggered.

[0070] Once the switching conditions are met, the system is qualified to switch, but this does not mean that the switch can be executed immediately. It is also necessary to ensure that the voltage waveforms of the current power supply branch and the target power supply branch remain synchronized at the moment of switching to avoid inrush current damage to the switching equipment.

[0071] Therefore, the present invention adopts a synchronous switching mechanism based on voltage zero-crossing point identification, which is implemented as follows: the voltage of the current power supply branch and the target power supply branch are continuously sampled respectively, wherein the current power supply branch refers to the power supply branch that is supplying power to the heat pump before the switching, and the target power supply branch refers to the power supply branch to be put into operation according to the target switching mode.

[0072] In real time, it determines whether the instantaneous value of each branch voltage changes from positive to negative or from negative to positive. When such a sign change is detected, the moment is identified as the zero-crossing point of the branch voltage.

[0073] Compare the zero-crossing times of the current power supply branch and the target power supply branch: When the time difference between the zero-crossing times of the two voltages is less than the synchronization threshold, a switching command is issued to shut down the current power supply branch and simultaneously turn on the target power supply branch. For example, the synchronization threshold is 100 microseconds.

[0074] The zero-crossing synchronous switching method can ensure that the switching action occurs at the natural zero-crossing point of the voltage, thereby effectively suppressing electrical shocks, reducing electric arcs, and improving the lifespan of switching equipment.

[0075] S5. After the switch is completed, the verification timing is identified based on the change in outdoor temperature. When the verification timing is reached, the switch verification of current-temperature correlation and voltage stability is triggered.

[0076] After the switchover is completed, if it is put into operation directly without verification, it cannot be confirmed whether it truly has the ability to cope with subsequent changes in operating conditions, and there may be hidden fault risks. To this end, the present invention introduces a switchover verification mechanism, which consists of two steps: first, determining the verification timing, and then performing the switchover verification.

[0077] See Figure 2 As shown, the following is a detailed description of a specific embodiment: S51, Determine the verification timing.

[0078] Traditional switching verification is mostly carried out immediately after the switch is completed. Although this verification method is fast, it is too hasty and fails to meet the right time for verification. The building's heat load changes with the outdoor temperature. If the verification is carried out when the heat load has not changed substantially, the system has not been tested under real working conditions, and the verification results obtained cannot prove whether the switch was truly successful.

[0079] To address the aforementioned issues, this invention considers that outdoor temperature is a driving factor for changes in heat load and uses its changes as a trigger condition for verification. The specific details are as follows: S511, At the moment the switching is completed, a monitoring window of a fixed duration is started, for example, 20 minutes. The function of this window is to provide an observation period for changes in outdoor temperature. Outdoor temperature is continuously collected within the window to form a temperature sampling sequence.

[0080] S512. For each pair of adjacent sampling points in the sequence, calculate the temperature change by subtracting the temperature of the previous sampling point from the temperature of the current sampling point. The change is used to determine whether the outdoor temperature has changed and the direction of the change.

[0081] S513. If the temperature changes at multiple consecutive sampling points within the window all exceed the stability limit and the direction of change is consistent, the fact that the temperature exceeds the stability limit indicates that the outdoor temperature has undergone a substantial change, and the consistent direction of change indicates that the change is continuous and unidirectional rather than oscillating. This indicates that the outdoor temperature is continuously rising or falling, which can provide real heat load disturbance conditions for subsequent handover verification and can immediately trigger handover verification.

[0082] If no effective temperature change is observed by the end of the monitoring window, it indicates that there was no significant disturbance in the heat load during the window period, and the system lacked an opportunity for practical testing. In this case, even if there are minor flaws in the switching process, the lack of load change will not lead to actual operational failure. Therefore, the current power supply mode after the switch can be maintained, and the outdoor temperature can continue to be monitored during subsequent operation. Once an effective temperature change occurs, the switching verification can be triggered again to supplement the verification of the switching effect.

[0083] S52, Switch verification.

[0084] Traditional switching verification is limited to static checks of electrical parameters at the moment of switching, and cannot verify the system's response capability under dynamic changes in heat load, resulting in unreliable verification results.

[0085] See Figure 3 As shown, for this purpose, the present invention introduces a dynamic verification method based on the correlation between outdoor temperature and heat pump operating current, and combines voltage stability judgment, and implements it as follows: S521, when triggering switching verification, continuously collect outdoor temperature, heat pump compressor operating current and heat pump input voltage. These three parameters represent: heat load driving source, system response and power supply quality, respectively, and form a time-aligned sampling sequence of outdoor temperature and heat pump compressor operating current.

[0086] S522. For each pair of adjacent sampling points in the outdoor temperature sampling sequence according to the time sequence, calculate the temperature change symbol sequence by subtracting the temperature of the previous sampling point from the temperature of the later sampling point. For the operating current sampling sequence, calculate the current change symbol sequence by subtracting the current of the previous sampling point from the current of the later sampling point. These two change symbols reflect the change in heat load and the response of the heat pump to the change in heat load, respectively.

[0087] S523. Due to the inherent delay in the response of a heat pump system to temperature changes, the timing of temperature changes and current responses are not strictly synchronized. Therefore, this invention performs time matching between the temperature change symbol sequence and the current change symbol sequence, ensuring that each temperature change symbol corresponds to a subsequent, time-matched current change symbol. The specific matching method is as follows: First, the temperature change symbol sequence is denoted as... The symbol sequence of current changes is denoted as Both are aligned using the same sampling time reference.

[0088] Secondly, from the first temperature change symbol Beginning, in the sequence of symbols for current changes from Begin searching backwards, find the first non-zero current change sign, and use that current change sign as... The matching object.

[0089] Then, starting from the position after the previous matched current symbol, the search proceeds backwards to find the first non-zero current change symbol as the matching object for the next temperature change symbol.

[0090] And so on, matching each temperature change symbol with the first non-zero current change symbol that follows it.

[0091] It should be noted that since the last temperature change symbol is located at the end of the sequence, there may be no subsequent non-zero current change symbol to match it. Therefore, this symbol is ignored and does not affect the established continuous matching judgment.

[0092] S524. When the following conditions are met simultaneously, the switching verification is deemed to be successful; otherwise, it is deemed to be unsuccessful and a back-switching operation is performed. The back-switching operation refers to restoring the power supply mode to the state before the switching: a) Temperature-current inverse relationship: In multiple consecutive matching pairs, the signs of temperature change and current change satisfy an inverse relationship, that is, when the temperature rises, the current decreases, or when the temperature falls, the current rises.

[0093] This is because the normal physical response of a heat pump is as follows: when the outdoor temperature rises, the building's heat load decreases, the heat output required by the heat pump decreases, and therefore the compressor's operating current should decrease accordingly; conversely, when the outdoor temperature falls, the heat load increases, the heat pump needs to output more heat, and the operating current should increase accordingly.

[0094] If the signs of temperature change and current change are the same, it indicates that the power supply system after the switch has failed to respond correctly to the change in heat load.

[0095] For example, if the current increases when the temperature rises, it means that the heat pump is still operating at high power, which will cause energy waste and indoor overheating.

[0096] If the current decreases when the temperature drops, it may lead to insufficient heating and an inability to maintain the indoor temperature.

[0097] Both of these anomalies can affect heating comfort and system energy efficiency, and need to be identified.

[0098] b) Voltage stability: The deviation between the input voltage of the heat pump and the rated voltage at multiple consecutive sampling points is within the allowable deviation range. For example, the allowable voltage deviation is ±5% of the rated voltage, which can be determined according to the State Grid standard or the equipment nameplate. This ensures that the power supply voltage quality is qualified after switching.

[0099] Through the above dual verification, the present invention ensures that the switched system not only has qualified electrical parameters, but also can dynamically respond correctly under real thermal load disturbances, thereby improving the reliability of switching.

[0100] After successful verification, to prevent unnecessary switching from being triggered again in a short period of time due to environmental fluctuations or signal interference, this invention adds a time-locking mechanism to ensure stable operation after switching. The specific operation is as follows: After successful verification, the lockout is initiated, for example, for 5 minutes. During the lockout period, all new switching requests are blocked, and any switching of power supply modes is prohibited. After the lockout period ends, the lockout is released, and normal response to switching requests is restored.

[0101] The time-locking mechanism can effectively avoid frequent actions after the switch is completed, ensure that the system has a sufficient stable observation period, reduce the number of switching operations, and extend the equipment life.

[0102] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0103] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0104] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0105] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0106] Finally, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for switching control between a modular photovoltaic-storage microgrid and an air-source heat pump for building applications, characterized in that, include: The system collects photovoltaic output power, heat pump input power, remaining energy storage power, and grid voltage and frequency in real time. It compares the collected data with the corresponding reference values ​​to determine whether the photovoltaic status is sufficient, insufficient, or lacking, whether the energy storage status is sufficient, critical, or scarce, and whether the grid status is normal or abnormal. A temperature trend signal is generated based on the direction of outdoor temperature change, and a switching lock signal is generated based on the operating time of the heat pump compressor. The target switching mode is determined by combining and matching photovoltaic status, energy storage status, grid status and temperature trend signals, and the switching conditions are determined to be met after the switching lock signal is released. In response to the fulfillment of switching conditions, the voltage waveforms of the current power supply branch and the target power supply branch are monitored for zero-crossing identification. Switching is triggered when the two voltages cross zero synchronously. After the switch is completed, the verification timing is identified based on the change in outdoor temperature. When the verification timing is reached, the switch verification of current-temperature correlation and voltage stability is triggered. When the switching verification is triggered, the outdoor temperature, the heat pump compressor operating current and the heat pump input voltage are continuously collected, and the outdoor temperature and the heat pump compressor operating current are combined into a time-aligned sampling sequence. For each pair of adjacent sampling points in the sequence, the temperature change symbol sequence is obtained by subtracting the temperature at the previous sampling point from the temperature at the later sampling point, and the current change symbol sequence is obtained by subtracting the current at the previous sampling point from the current at the later sampling point. The temperature change symbol sequence is time-matched with the current change symbol sequence so that each temperature change symbol corresponds to the current change symbol that appears afterward. The switchover verification is considered successful if the following conditions are met simultaneously; otherwise, it is considered unsuccessful and a switchback operation is performed. a) In multiple consecutive matching pairs, the signs of temperature change and current change satisfy an inverse relationship; b) The deviations between the input voltage and the rated voltage of the heat pump at multiple consecutive sampling points are all within the allowable deviation range.

2. The method for switching control between a modular photovoltaic-storage microgrid and an air-source heat pump for buildings as described in claim 1, characterized in that: The determination of photovoltaic status as sufficient, insufficient, or lacking, the classification of energy storage status as adequate, critical, or scarce, and the determination of grid status as normal or abnormal include the following: The photovoltaic output power is compared with the heat pump input power. The photovoltaic state is determined to be sufficient if any of the following conditions are met: 1) The photovoltaic output power is greater than the heat pump input power, and the difference between the two exceeds the margin; 2) The photovoltaic output power is greater than or equal to the heat pump input power and the photovoltaic output power increases at multiple consecutive sampling times; When the photovoltaic output power is less than the heat pump input power, the photovoltaic status is determined to be insufficient. When the photovoltaic output power is lower than the minimum operating power of the photovoltaic array, the photovoltaic status is determined to be missing. The remaining energy storage capacity is compared with the high energy threshold and the low energy threshold respectively. When the remaining energy is higher than the high energy threshold, the energy storage status is determined to be sufficient. When the remaining energy is between the high energy threshold and the low energy threshold, the energy storage status is determined to be critical. When the remaining energy is lower than the low energy threshold, the energy storage status is determined to be scarce. The voltage and frequency of the power grid are compared with the normal operating range. When both voltage and frequency are within the normal operating range, the power grid is considered to be in normal condition. When either voltage or frequency exceeds the normal operating range, the power grid is considered to be in abnormal condition.

3. The method for switching control between a modular photovoltaic-storage microgrid and an air-source heat pump for buildings as described in claim 1, characterized in that: The temperature trend signal is generated according to the following process: Continuously collect outdoor temperature data and calculate the temperature change between adjacent sampling points; If, within a continuous sampling period, the temperature change of each sampling point relative to the previous sampling point is positive, it is determined to be a warming trend. If the temperature change at each sampling point relative to the previous sampling point is negative, it is determined to be a cooling trend. If the absolute value of all temperature changes is less than the preset stability limit, then it is determined to be a stable trend.

4. The method for switching control between a modular photovoltaic-storage microgrid and an air-source heat pump for buildings as described in claim 1, characterized in that: The step of generating a switching lockout signal based on the heat pump compressor's operating time includes: When the heat pump compressor is detected to switch from the start-up state to the stable operation state, the start timer begins to accumulate the continuous running time of the compressor. The timer is automatically reset to zero after the heat pump stops. When the cumulative duration is less than the preset minimum running time, the output is locked; when the cumulative duration reaches or exceeds the minimum running time, the lock level is released.

5. The method for switching control between a modular photovoltaic-storage microgrid and an air-source heat pump for buildings as described in claim 1, characterized in that: The method for determining the target switching mode through combination matching is as follows: When the photovoltaic power supply is sufficient, the target switching mode is determined to be the photovoltaic power supply mode; When the photovoltaic status is insufficient, the energy storage status is sufficient, the grid status is normal, and the temperature trend signal is non-cooling trend, the target switching mode is determined to be the photovoltaic-energy storage coordinated mode. When the photovoltaic status is missing, the energy storage status is sufficient, and the grid status is abnormal, the target switching mode is determined to be the energy storage power supply mode. When the photovoltaic status is insufficient, the energy storage status is sufficient, the grid status is normal, and the temperature trend signal is a cooling trend, the target switching mode is determined to be the mains power backup mode. When energy storage is scarce and the power grid is in normal condition, the target switching mode is determined to be the mains power backup mode.

6. The method for switching control between a modular photovoltaic-storage microgrid and an air-source heat pump for buildings as described in claim 1, characterized in that: The process of determining whether the switching conditions are met after the switching lock signal is released includes: The level of the switching lock signal is monitored in real time. When the lock signal is detected to change from the lock level to the unlock level, a delay timer is started. During the operation of the delay timer, the lock signal is continuously monitored to see if the lock level reappears. If the lock level does not reappear, the switching condition is determined to be met when the timer returns to zero. If the lock level reappears, the current timing is terminated, and the system waits for the next transition of the lock signal, repeating the above process.

7. The method for switching control between a modular photovoltaic-storage microgrid and an air-source heat pump for buildings as described in claim 1, characterized in that: The triggering switching process includes: The voltages of the current power supply branch and the target power supply branch are continuously sampled. When the instantaneous value of the branch voltage changes from positive to negative or from negative to positive, the moment is taken as the zero-crossing point of the branch voltage. Compare the zero-crossing times of the current power supply branch and the target power supply branch. When the time difference between the zero-crossing times of the two voltages is less than the synchronization threshold, a switching command is issued to shut down the current power supply branch and simultaneously turn on the target power supply branch.

8. The method for switching control between a modular photovoltaic-storage microgrid and an air-source heat pump for buildings as described in claim 1, characterized in that: The identification and verification timing includes the following: A fixed-duration monitoring window is initiated at the moment the switch is completed, and outdoor temperature is continuously collected within the window to form a temperature sampling sequence; If the temperature changes at multiple consecutive sampling points within the window all exceed the stability limit and the direction of change is consistent, it is determined that the outdoor temperature has changed effectively, and a switching verification is triggered. If no change in outdoor temperature occurs by the end of the window, the current power supply mode is maintained.

9. The method for switching control between a modular photovoltaic-storage microgrid and an air-source heat pump for buildings as described in claim 1, characterized in that: It also includes time-locking after successful verification, as follows: Once verification is successful, a time-based latch is initiated, prohibiting new handover requests during the latch period. After the latch period ends, the latch is released, allowing new handover requests to be responded to.

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