A control method for a photovoltaic mains hybrid driven external power supply heat pump host

Abstract

The present application relates to the technical field of heat pump equipment, and particularly relates to a control method of a heat pump host for external power supply driven by photovoltaic and commercial power. The present application obtains mixed direct current by respectively preprocessing solar energy collected by photovoltaic and alternating current collected by commercial power, and determines whether there is surplus power in the mixed direct current based on the difference between photovoltaic power generation power and the operating power of the heat pump host. When there is no surplus power, the commercial power is used to supply the heat pump host with the balance current; when there is surplus power, the operating trend of the heat pump host is determined according to the source load response time difference and the thermal response lag, and whether the surplus power is switched to the external load interface to supply external load equipment is determined according to the operating trend, and after the switching is completed, whether the switching result is qualified is verified through the heat pump host power supply loop current and the external load interface output voltage. Therefore, the utilization rate of photovoltaic energy is improved.

Description

Technical Field

[0001] This invention relates to the field of heat pump equipment technology, and in particular to a control method for an externally powered heat pump host for photovoltaic-mains hybrid drive. Background Technology

[0002] Existing photovoltaic direct-drive heat pump systems suffer from core technological flaws. When the heat pump unit shuts down, the direct current generated by the photovoltaic modules lacks an effective channel for consumption, forcing the system to be curtailed. This results in low photovoltaic energy utilization, especially during non-heating / cooling seasons or when the heat pump operates intermittently. To address this issue, some existing solutions use energy storage batteries to store excess photovoltaic power. However, the addition of energy storage batteries significantly increases system construction costs and maintenance complexity, and also presents problems such as battery degradation and limited lifespan. Another solution uses a photovoltaic grid-connected mode, where photovoltaic power requires multiple power conversions through photovoltaic inversion and grid rectification before being supplied to the heat pump. This leads to energy conversion losses, failing to fully leverage the high efficiency of direct DC power supply, and also results in a complex system structure and reduced reliability. Requiring an external inverter to continue using photovoltaic power after the main unit shuts down is inconvenient for installation and costly.

[0003] Chinese Patent Publication No. CN121077043A discloses a power supply method for a photovoltaic direct-drive heat pump water heater, belonging to the field of heat pump power supply technology. By employing mains rectification, PFC, and boost modules, as well as photovoltaic drive and photovoltaic boost modules, the two power supplies can be synchronously adjusted to the required voltage of the DC bus. Furthermore, through dynamic voltage tracking and maximum power point tracking technology, the photovoltaic output voltage is ensured to always remain at the optimal power point, achieving efficient coordination and stable power supply between the power supplies, thereby enabling the use of photovoltaics to power the compressor.

[0004] However, the following problems still exist in the existing technology. In a photovoltaic direct-drive heat pump system, when the heat pump unit stops operating, the photovoltaic modules continue to generate electricity, resulting in the inability to consume the generated direct current and causing curtailment of solar power, which leads to low utilization of photovoltaic energy. Summary of the Invention

[0005] To address this issue, the present invention provides a control method for a photovoltaic-mains hybrid-driven external power supply heat pump host, which overcomes the problem in the prior art where, when the heat pump host stops operating, the photovoltaic modules continue to generate electricity, resulting in the inability to absorb the generated DC power and thus causing curtailment, leading to low photovoltaic energy utilization.

[0006] To achieve the above objectives, the present invention provides a control method for an externally powered heat pump host with photovoltaic and mains hybrid drive, comprising, The solar energy collected by photovoltaic power and the alternating current collected by mains power are preprocessed to obtain a mixed direct current. Determine whether there is surplus power in the hybrid DC power supply based on the characteristics of the power supply deviation; In response to the existence of surplus power in the hybrid DC power supply, the operating trend of the heat pump host is determined based on the source-load response time difference and the thermal response lag. Based on the operating trend of the heat pump host, determine whether to switch the surplus power; wherein, the power switching adopts a switching sequence of first closing and then disconnecting, and switches the surplus power to the external load interface to supply the external load equipment. Once the power switching is completed, the success of the power switching is determined based on the power supply circuit current of the heat pump unit and the output voltage of the external load interface.

[0007] Furthermore, the process of determining whether the hybrid DC power has surplus power includes, Based on the characteristics of power supply deviation, it can be determined whether there is surplus power in the hybrid DC power supply, or whether there is no surplus power in the hybrid DC power supply.

[0008] Furthermore, the process of determining the power supply deviation characteristics includes, The power supply deviation characteristics are determined based on the difference between the average photovoltaic power generation and the average operating power of the heat pump host within the same time period.

[0009] Furthermore, the processing procedure when there is no surplus power in the hybrid DC power includes: When there is no surplus power in the hybrid DC power supply and the power supply deviation characteristic is negative, the differential current supplemented by the mains power is determined based on the power supply deviation characteristic and the DC bus voltage, and the hybrid DC power supply and differential current are jointly supplied to the heat pump host.

[0010] Furthermore, the process of determining the operating trend of the heat pump unit includes, The heat pump host is determined to be either shut down or in operation based on the source load response time difference and the thermal response lag.

[0011] Furthermore, the process of determining the source load response time difference includes, Acquire the photovoltaic power generation change time and the operating power change time of the heat pump host within the same acquisition window; The source load response time difference is determined based on the average of the absolute values ​​of the time delays between each photovoltaic change time and the corresponding operational change time. Among them, the photovoltaic change time is determined based on the rate of change of photovoltaic power generation, and the operation change time is determined based on the rate of change of the operating power of the heat pump host.

[0012] Furthermore, the process of determining the thermal response hysteresis includes, The thermal response hysteresis is determined based on the difference in the rate of change of compressor exhaust temperature and the rate of change of compressor operating current of the heat pump host within the same acquisition window.

[0013] Furthermore, the process of determining whether surplus power should be switched over includes, If the heat pump unit is in operation, the surplus power will not be switched. If the heat pump unit is trending towards shutdown, the surplus power will be used for power switching. Among them, the power switching adopts a switching sequence of first closing and then disconnecting, and the surplus power is switched to the external load interface to supply the external load equipment.

[0014] Furthermore, the process of determining surplus electricity includes, The power supply deviation characteristic is identified as surplus power.

[0015] Furthermore, the process of determining whether the power switch is qualified includes, The power switching is determined to be either successful or unsuccessful based on the current value of the power supply circuit of the heat pump host after the power switch and the output voltage value of the external load interface.

[0016] Compared with existing technologies, this invention preprocesses the solar energy collected by photovoltaic power and the AC power collected by the mains to obtain hybrid DC power. It then determines whether there is surplus power in the hybrid DC power based on the difference between the operating power of the heat pump unit and the photovoltaic power generation. When there is no surplus power, the mains power supplements the difference current to supply the heat pump unit, ensuring its normal operation. When there is surplus power, the operating trend of the heat pump unit is determined based on the source-load response time difference and thermal response lag. If it is determined to be a working trend, power supply to the heat pump unit is maintained; if it is determined to be a shutdown trend, the surplus power is switched to the external load interface to supply external load devices. After the switch is completed, the switching result is verified by monitoring the current in the heat pump unit's power supply circuit and the output voltage of the external load interface. This improves the utilization rate of photovoltaic energy.

[0017] In particular, this invention determines the operating trend of the heat pump host based on the source load response time difference and thermal response lag, enabling early identification of the shutdown trend before the heat pump host has completely shut down. This eliminates the switching lag and curtailment problems caused by passive response in existing technologies. Specifically, in a photovoltaic direct-drive heat pump system, photovoltaic power generation can change abruptly within milliseconds due to variations in sunlight. The heat pump compressor, as a large inertial load, is constrained by mechanical and thermal inertia in its power regulation, resulting in a relatively slow response. This means that during the window period before the heat pump power responds when photovoltaic power has changed, the supply and demand status of the current heat pump host cannot be accurately determined based on the power difference, leading to curtailment. This application introduces a source-load response time difference, i.e., the time delay between the moment the photovoltaic power generation changes and the moment the heat pump host's operating power responds. The inherent difference in their response speeds creates a detectable time delay within the window period when the photovoltaic power has changed but the heat pump power has not yet responded. This time delay is the source-load response time difference. This application utilizes this time difference to detect source-load imbalance in advance within the disconnection window. Simultaneously, it introduces a thermodynamic response hysteresis, i.e., the response deviation between the rate of change of compressor exhaust temperature and the rate of change of operating current. Operating current is an electrical parameter, and its change can be completed within milliseconds; while exhaust temperature is a thermodynamic parameter, and its change is constrained by the thermal inertia of the entire refrigeration system, requiring multiple stages including changes in compression work, refrigerant state changes, pipe wall heat exchange, and temperature sensor response. The response time is typically on the order of seconds or even minutes. The response speeds of the two differ by orders of magnitude. This application utilizes the physical law that electrical parameters respond faster than thermodynamic parameters to identify shutdown trends in advance during the critical stage when the electrical response inside the heat pump already indicates a shutdown trend, but the thermodynamic parameters have not yet changed significantly. By using both methods in a coordinated manner, the switching delays and curtailment issues caused by lagging thermal parameters are eliminated, ensuring seamless consumption of photovoltaic power.

[0018] In particular, this invention determines whether to switch surplus power based on the operating trend of the heat pump unit. In the actual operation of a photovoltaic direct-drive heat pump system, when the indoor temperature reaches the set value, the compressor does not stop instantly, but undergoes a transition process of gradual power reduction. The system determines whether the heat pump unit is truly approaching shutdown based on the source load response time difference and thermal response lag, and decides whether to switch accordingly. During the operating trend, power supply is maintained, and surplus power continues to supply the heat pump unit to meet its normal operating needs, thus avoiding accidental disconnection that could interrupt heat pump operation. During the shutdown trend, the system switches in advance to eliminate the impact of the imminent shutdown of the heat pump unit causing a momentary loss of load on the photovoltaic power, leading to the inverter shutting down due to no-load protection and resulting in curtailment of solar power. Therefore, by deciding the power allocation in advance based on the operating trend, rather than waiting for the heat pump to completely shut down, the system achieves accurate capture of the heat pump shutdown trend and proactive control of the switching timing, thereby improving the utilization rate of photovoltaic energy.

[0019] In particular, this invention determines whether the power switching is qualified based on the power supply circuit current of the heat pump unit and the output voltage of the external load interface. In engineering practice, if the relay contacts fail to operate as scheduled due to oxidation, mechanical jamming, or delayed action, the switching will fail. Therefore, after the switching is completed, the switching result is verified by actual measurement of physical quantities to ensure that the switching action is truly executed. Specifically, the power supply circuit current of the heat pump unit indicates whether the heat pump unit has been successfully de-energized. When its current value drops below the current threshold, it indicates that the power supply circuit of the heat pump unit has been reliably disconnected. At the same time, the output voltage of the external load interface indicates whether the external load has been successfully connected. When its voltage value reaches or exceeds the voltage threshold, it indicates that the surplus power has been normally delivered to the external load. When both conditions are met, the power switching is deemed qualified. The system then re-executes the switching or maintains the current power supply state, thereby making the power switching result verifiable, improving the reliability of power switching, and enhancing the stability and safety of system operation. Attached Figure Description

[0020] Figure 1 This is a system block diagram of the control system for an externally powered heat pump host with photovoltaic-mains hybrid drive, according to an embodiment of the invention. Figure 2 This is a schematic diagram illustrating the steps of a control method for an externally powered heat pump host for photovoltaic-mains hybrid drive, according to an embodiment of the invention. Figure 3 A logic diagram for determining whether there is surplus power in a hybrid DC power supply according to an embodiment of the invention; Figure 4 This is a logic block diagram illustrating how to determine whether to switch power when there is surplus power, according to an embodiment of the invention. Detailed Implementation

[0021] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0022] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0023] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] Please see Figure 1 The diagram shown is a system block diagram of a control system for a photovoltaic-mains hybrid-driven external power supply heat pump host according to an embodiment of the invention. The system of the present invention includes: The preprocessing module is used to preprocess the solar energy collected by photovoltaic and the AC power collected by the mains to obtain mixed DC power; The surplus power determination module is used to determine whether there is surplus power in the mixed DC power based on the characteristics of power supply deviation. The operation trend detection module is used to respond to the existence of surplus power in the hybrid DC power supply and determine the operation trend of the heat pump host based on the source load response time difference and the thermal response lag. The switching decision module is used to determine whether to switch power when there is surplus electricity based on the operating trend of the heat pump unit. The qualification verification module is used to complete the power switching and determines whether the power switching is qualified based on the power supply circuit current of the heat pump host and the output voltage of the external load interface.

[0025] Please see Figure 2 The diagram illustrates the steps of a control method for an externally powered heat pump host with photovoltaic-mains hybrid drive, according to an embodiment of the invention. The method of the present invention includes: The solar energy collected by photovoltaic power and the alternating current collected by mains power are preprocessed to obtain a mixed direct current. Determine whether there is surplus power in the hybrid DC power supply based on the characteristics of the power supply deviation; In response to the existence of surplus power in the hybrid DC power supply, the operating trend of the heat pump host is determined based on the source-load response time difference and the thermal response lag. Determine whether to switch to other power sources based on the operating trend of the heat pump unit; Once the power switching is completed, the success of the power switching is determined based on the power supply circuit current of the heat pump unit and the output voltage of the external load interface.

[0026] In this embodiment, the preprocessing includes photovoltaic-side preprocessing and mains-side preprocessing. Photovoltaic-side preprocessing involves the DC power output from the photovoltaic array undergoing maximum power point tracking (MPPT) and voltage regulation via a unidirectional DC / DC boost converter, outputting a first DC power to the DC bus. Mains-side preprocessing involves the AC power input from the mains undergoing rectification and voltage regulation via a unidirectional AC / DC rectifier, outputting a second DC power to the DC bus. The first and second DC powers are connected in parallel on the DC bus, forming a hybrid DC power. The preprocessing methods described are all prior art, and their specific implementations will not be elaborated here.

[0027] Please see Figure 3As shown, this is a logic diagram for determining whether there is surplus power in the hybrid DC power supply according to an embodiment of the invention. The process for determining whether there is surplus power in the hybrid DC power supply in this embodiment includes: If the power supply deviation characteristic is greater than or equal to the reference power supply deviation, it is determined that the hybrid DC power supply has surplus power; if the power supply deviation characteristic is less than the reference power supply deviation, it is determined that the hybrid DC power supply does not have surplus power.

[0028] In this embodiment, the reference power supply deviation is the surplus state of photovoltaic power generation and heat pump host during normal operation in a historical period. The reference power supply deviation is a positive value. As an example, the process of determining the reference power supply deviation includes obtaining the difference between the absolute value of the average photovoltaic power generation of the heat pump host in the historical period and the average operating power of the heat pump host in the corresponding historical period. The duration of the historical period can be determined according to the actual application scenario, such as a complete heating or cooling season, to ensure that the obtained power average is representative.

[0029] The process for determining the power supply deviation characteristics in this embodiment includes, The power supply deviation characteristics are obtained by subtracting the average operating power of the heat pump host from the average photovoltaic power generation power within the same time period.

[0030] In this embodiment, the time period is set according to the actual operating conditions of the heat pump unit to ensure that the obtained average power value can truly reflect the average electricity demand and average power generation capacity under the current operating conditions. Those skilled in the art can reasonably set the duration of the predetermined time period according to the actual sampling frequency and the characteristics of operating condition changes, which will not be elaborated here.

[0031] In this embodiment, the power supply deviation characteristic is the degree of deviation between the average photovoltaic power generation capacity and the average power demand of the heat pump host within a predetermined period. The larger the power supply deviation characteristic, the more abundant the photovoltaic power is, and there is a surplus power beyond meeting the normal operation requirements of the heat pump host. The smaller the power supply deviation characteristic, the less sufficient the photovoltaic power is to meet the operation requirements of the heat pump host, and the higher the dependence of the heat pump host on the mains power.

[0032] It is understandable that the operating power of the heat pump host can be obtained in real time through its built-in frequency converter or power sensor, and the photovoltaic power generation can be obtained in real time through the output voltage and current sensors of the photovoltaic DC power generation module. Both can be collected through the CAN bus communication interface at a reasonable sampling frequency. The specific implementation method is a conventional technical means in this field and will not be elaborated here.

[0033] The process for determining when there is no surplus power in the hybrid DC power supply in this embodiment includes: The absolute value of the power supply deviation characteristic is determined, and the differential current supplemented by the mains power is determined based on the ratio of the absolute value to the DC bus voltage. The mixed DC power and the differential current are then supplied to the heat pump host.

[0034] In this embodiment, the differential current is the current demand corresponding to the difference between the operating power of the heat pump host and the photovoltaic power generation power. That is, the current value that the heat pump host needs to be supplemented by the mains power under the current operating state. It is used to accurately quantify the amount of mains power supplementation when photovoltaic power generation is insufficient, and to ensure the continuity and stability of the power supply of the heat pump host.

[0035] The process of determining the operating trend of the heat pump unit in this embodiment includes: If the source load response time difference is greater than or equal to the reference source load response value, and the thermal response lag is greater than or equal to the reference thermal response lag value, then the heat pump host is determined to be in a shutdown trend. If the source load response time difference is less than the reference source load response value, or the thermal response hysteresis is less than the reference thermal response hysteresis value, then the heat pump host is determined to be in operation.

[0036] In this embodiment, the reference source load response value is a critical reference value used to determine whether the source load response time difference has significantly deviated from the normal operating range. As an example, the process of determining the reference source load response value includes obtaining historical operating data of the heat pump host under normal operating conditions and calculating the average of multiple sets of source load response time differences of the heat pump host under normal operating conditions as the reference source load response value.

[0037] In this embodiment, the reference thermal response hysteresis value is the maximum acceptable deviation between the electrical response and thermal response of the heat pump host during normal operation. As an example, the process of determining the reference thermal response hysteresis value includes obtaining multiple sets of historical thermal response hysteresis data of the heat pump host under normal operation, and calculating the average value of the thermal response hysteresis value to determine the reference thermal response hysteresis value.

[0038] It should be noted that if the heat pump host is already in a shutdown state, for example, its operating power is zero or a shutdown feedback signal is received, then the heat pump host is directly determined to be in a shutdown trend, and there is no need to calculate the source load response time difference and thermal response lag.

[0039] It should be noted that photovoltaic power generation fluctuates continuously during normal operation due to changes in sunlight. This fluctuation provides a detectable power change signal for measuring the source-load response time difference. When the heat pump unit tends to shut down, its response speed to power fluctuations slows down, manifested as an increase in the source-load response time difference. Therefore, the larger the source-load response time difference, the more the heat pump unit tends to shut down. However, only in special operating conditions where photovoltaic power generation does not change significantly within a preset time period and the source-load response time difference cannot be measured, is the shutdown trend determined solely by the thermal response hysteresis. The preset time period is determined based on the normal fluctuation cycle of photovoltaic power generation and can be determined by those skilled in the art based on actual sunlight conditions.

[0040] The process for determining the source load response time difference in this embodiment includes, Acquire the photovoltaic power generation change time and the operating power change time of the heat pump host within the same acquisition window; The source load response time difference is determined based on the average of the absolute values ​​of the time delays between each photovoltaic change time and the corresponding operational change time. Among them, the photovoltaic change time is the time when the rate of change of photovoltaic power generation is greater than or equal to the benchmark rate of change of power generation, and the operation change time is the time when the rate of change of the operating power of the heat pump host is greater than or equal to the benchmark rate of change of operating power.

[0041] In this embodiment, the benchmark power generation change rate is the normal change value of photovoltaic power generation under normal operation. As an example, the process of determining the benchmark power generation change rate includes obtaining historical power generation change rate data of the photovoltaic power generation within a nearly complete sunshine season or a natural month, and determining the average historical change rate of photovoltaic power generation as the power generation change threshold.

[0042] In this embodiment, the baseline operating change rate is the normal power change value of the heat pump host under normal operating conditions caused by the compressor frequency rise and fall and start-stop control. As an example, the process of determining the baseline operating change rate includes: acquiring historical operating change rate data of the heat pump host operating power in the past complete operating cycle or natural month in advance, and determining the average historical operating change rate of the heat pump host operating power as the operating change threshold.

[0043] In this embodiment, the source-load response time difference is the degree of synchronization deviation between the photovoltaic power supply side power change and the heat pump load side power response. The larger the source-load response time difference, the more severe the disconnect between the photovoltaic power change and the heat pump power response, and the more necessary the system intervention. The smaller the source-load response time difference, the better the synchronization between the photovoltaic power change and the heat pump power response, and the higher the power matching degree between the source and load.

[0044] It is understandable that the same acquisition window is used to ensure that the photovoltaic change time and the operation change time have a temporal correspondence. When there are multiple photovoltaic change times and multiple operation change times, for each photovoltaic change time, the operation change time that is closest to that photovoltaic change time in time is obtained, the time delay between the two is calculated, and the average of the absolute values ​​of all time delays is determined as the source load response time difference. This ensures that each time delay reflects the causal relationship between the power change and power response corresponding to the same source load event. Those skilled in the art can reasonably set the duration of the same acquisition window according to the actual power response characteristics of the heat pump host, which will not be elaborated here.

[0045] The process for determining the thermal response hysteresis in this embodiment includes, Obtain the rate of change of compressor exhaust temperature and the rate of change of compressor operating current of the heat pump host within the same acquisition window; The ratio of the rate of change of compressor discharge temperature to the rate of change of reference temperature is determined as the first ratio value; The ratio of the compressor operating current change rate to the reference current change rate is determined as the second ratio value; The absolute value of the difference between the first ratio and the second ratio is determined as the thermal response hysteresis.

[0046] In this embodiment, the reference temperature change rate is the reference value of the rate of change of the compressor exhaust temperature under stable operating conditions. As an example, the process of determining the reference temperature change rate includes obtaining the time series data of the exhaust temperature of the compressor of the heat pump host under stable operating conditions, calculating the amount of change of exhaust temperature per unit time, and taking the average value as the corresponding reference temperature change rate.

[0047] In this embodiment, the reference current change rate is the reference value of the change rate of the compressor operating current under stable operating conditions. As an example, the process of determining the reference current change rate includes acquiring the operating current time sequence data of the heat pump host under stable operating conditions and using the average value of the operating current change rate as the reference current change rate.

[0048] In this embodiment, the thermodynamic response hysteresis is the degree to which the rate of change of the compressor's exhaust temperature lags behind the rate of change of the operating current. The greater the thermodynamic response hysteresis, the greater the deviation between the rate of change of the exhaust temperature and the rate of change of the operating current, and the more obvious the compressor tends to shut down; the smaller the thermodynamic response hysteresis, the more synchronized the electrical response and the more stable the compressor's operating state.

[0049] It is understood that the rate of change of compressor exhaust temperature can be determined based on the exhaust temperature value collected in real time by the exhaust temperature sensor of the heat pump host, and the rate of change of compressor operating current can be determined based on the real-time operating current value fed back by the current sensor of the heat pump host. Both are characterized by the amount of change per unit time. Those skilled in the art can select the appropriate sensor and sampling frequency according to the actual system configuration, which will not be elaborated here.

[0050] Please see Figure 4 The diagram shown is a logic block diagram for determining whether surplus power should be switched in accordance with an embodiment of the invention. The process of determining whether surplus power should be switched in this embodiment includes: If the heat pump unit is in operation, the surplus power will not be switched. If the heat pump unit is trending towards shutdown, the surplus power will be used for power switching. Among them, the power switching adopts a switching sequence of first closing and then disconnecting, and the surplus power is switched to the external load interface to supply the external load equipment.

[0051] In this embodiment, the power switching adopts a switching sequence of "on first, off later". That is, the external load interface is first controlled to be turned on so that the surplus power can flow to the external load device; after confirming that the external load interface is turned on, the power supply circuit of the heat pump host is then turned off. The external load interface is a configurable power output port, and its output form is matched with the type of the external load device.

[0052] Understandably, by switching the power supply path sequentially, the surplus power is always connected to the load during the switching process, avoiding the photovoltaic inverter from entering the no-load protection state due to the sudden disconnection of the load. This achieves synchronous and delay-free switching of the power supply path, ensuring the continuous consumption of photovoltaic power and the smooth transition of external power supply.

[0053] It is understandable that the surplus current corresponding to the surplus power is determined by converting the DC bus voltage value. Specifically, the surplus current is the ratio of the surplus power to the DC bus voltage. Power switching is essentially switching the surplus current to the external load interface to supply the external load equipment.

[0054] It should be noted that when the heat pump unit is operating at full capacity and there is surplus electricity, the surplus electricity is naturally absorbed by the heat pump unit during its operation. Only when the surplus electricity exceeds the maximum absorbable power of the heat pump unit will the power limiting protection be activated to reduce the photovoltaic output power to prevent DC bus voltage surge.

[0055] The process for determining surplus electricity in this embodiment includes, The power supply deviation characteristic is identified as surplus power.

[0056] The process for determining whether a power switch is successful in this embodiment includes: Obtain the power supply circuit current value of the heat pump unit and the output voltage value of the external load interface; If the power supply circuit current is less than the disconnection current and the output voltage is greater than or equal to the power supply voltage, the power switching is deemed successful. If the power supply circuit current value is greater than or equal to the disconnection current value, or the output voltage value is less than the reference voltage value, the power switching is deemed unqualified.

[0057] It should be noted that the power switching is deemed successful only after the entire switching sequence of "close first, disconnect later" has been executed.

[0058] In this embodiment, the disconnect current value is the critical current value for determining whether the power supply circuit of the heat pump host has been successfully disconnected. As an example, the process of determining the disconnect current value includes: collecting power supply circuit current data of the heat pump host during multiple normal operation processes, and taking the minimum value as the minimum current for normal operation; collecting power supply circuit current data of the heat pump host after multiple shutdowns, and taking the average value as the residual current after shutdown; setting the disconnect current value between the minimum current for normal operation and the residual current after shutdown to ensure that the operating trend and shutdown trend of the heat pump host can be accurately distinguished. Those skilled in the art can determine the disconnect current value based on the electrical characteristics of the actual system, which will not be elaborated here.

[0059] In this embodiment, the power supply voltage value is the critical voltage value for whether the external load interface has been successfully connected to the power supply. As an example, the process of determining the power supply voltage value includes collecting the output voltage data of the external load interface during multiple normal power supply processes and taking the average value as the power supply voltage value.

[0060] It is understandable that the current value of the power supply circuit of the heat pump host can be obtained in real time by a current sensor set on the power supply circuit, and the output voltage value of the external load interface can be obtained in real time by a voltage sensor set on the external load interface. The specific implementation method is a conventional technical means in this field, and will not be described in detail here.

[0061] In this embodiment, if the power switching is deemed unqualified, the power switching is re-executed; if it still fails after re-execution, the current power supply state is maintained, and a switching failure event is recorded. If the number of consecutive switching failure events reaches a set number, the system is determined to have a persistent fault, retries are stopped, and a fault indication signal is output.

[0062] It is understood that the number of times the settings can be configured by those skilled in the art based on the actual system's reliability requirements, and this will not be elaborated further.

[0063] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A control method for an externally powered heat pump host with photovoltaic-mains hybrid drive, characterized in that, include, The solar energy collected by photovoltaic power and the alternating current collected by mains power are preprocessed to obtain a mixed direct current. Determine whether there is surplus power in the hybrid DC power supply based on the characteristics of the power supply deviation; In response to the existence of surplus power in the hybrid DC power supply, the operating trend of the heat pump host is determined based on the source-load response time difference and the thermal response lag. Based on the operating trend of the heat pump unit, determine whether to switch the surplus power; wherein, the power switching adopts a switching sequence of first switching on and then switching off, and switches the surplus power to the external load interface to supply the external load equipment. Once the power switching is completed, the success of the power switching is determined based on the power supply circuit current of the heat pump unit and the output voltage of the external load interface.

2. The control method for an externally powered heat pump host for photovoltaic-mains hybrid drive according to claim 1, characterized in that, The process of whether the hybrid DC power has surplus power includes... Based on the characteristics of power supply deviation, it can be determined whether there is surplus power in the hybrid DC power supply, or whether there is no surplus power in the hybrid DC power supply.

3. The control method for an externally powered heat pump host for photovoltaic-mains hybrid drive according to claim 1, characterized in that, The process of determining the power supply deviation characteristics includes: The power supply deviation characteristics are determined based on the difference between the average photovoltaic power generation and the average operating power of the heat pump host within the same time period.

4. The control method for an externally powered heat pump host for photovoltaic-mains hybrid drive according to claim 2, characterized in that, The process for handling the hybrid DC power when there is no surplus power includes: When there is no surplus power in the hybrid DC power supply and the power supply deviation characteristic is negative, the differential current supplemented by the mains power is determined based on the power supply deviation characteristic and the DC bus voltage, and the hybrid DC power supply and differential current are jointly supplied to the heat pump host.

5. The control method for an externally powered heat pump host for photovoltaic-mains hybrid drive according to claim 1, characterized in that, The process of determining the operating trend of the heat pump unit includes, The heat pump host is determined to be either shut down or in operation based on the source load response time difference and the thermal response lag.

6. The control method for an externally powered heat pump host for photovoltaic-mains hybrid drive according to claim 1, characterized in that, The process of determining the source load response time difference includes, Acquire the photovoltaic power generation change time and the operating power change time of the heat pump host within the same acquisition window; The source load response time difference is determined based on the average of the absolute values ​​of the time delays between each photovoltaic change time and the corresponding operational change time. Among them, the photovoltaic change time is determined based on the rate of change of photovoltaic power generation, and the operation change time is determined based on the rate of change of the operating power of the heat pump host.

7. The control method for an externally powered heat pump host for photovoltaic-mains hybrid drive according to claim 1, characterized in that, The process of determining the thermal response hysteresis includes: The thermal response hysteresis is determined based on the difference in the rate of change of compressor exhaust temperature and the rate of change of compressor operating current of the heat pump host within the same acquisition window.

8. The control method for an externally powered heat pump host for photovoltaic-mains hybrid drive according to claim 1, characterized in that, The process of determining whether surplus electricity should be switched over includes... If the heat pump unit is in operation, the surplus power will not be switched. If the heat pump unit is trending towards shutdown, the surplus power will be used for power switching. Among them, the power switching adopts a switching sequence of first closing and then disconnecting, and the surplus power is switched to the external load interface to supply the external load equipment.

9. The control method for an externally powered heat pump host for photovoltaic-mains hybrid drive according to claim 1, characterized in that, The process of determining surplus electricity includes... The power supply deviation characteristic is identified as surplus power.

10. The control method for an externally powered heat pump host for photovoltaic-mains hybrid drive according to claim 1, characterized in that, The process of determining whether a power switch is qualified includes, The power switching is determined to be either successful or unsuccessful based on the current value of the power supply circuit of the heat pump host after the power switch and the output voltage value of the external load interface.

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