A method for controlling the frequency of a compressor of a variable frequency dehumidifier

Abstract

The application is suitable for the field of dehumidifiers, and discloses a compressor frequency control method of a variable frequency dehumidifier, which comprises the following steps: acquiring a user-set humidity value and an actual ambient humidity value, and calculating a humidity deviation; calculating a basic compressor frequency based on the humidity deviation through a PID control algorithm; controlling the compressor of the dehumidifier to operate at the basic compressor frequency; acquiring influence parameters, which include an evaporator temperature, a compressor discharge temperature, an ambient temperature, an AC voltage, an AC current and a compressor current; based on the influence parameters, correcting the basic compressor frequency through a preset multi-stage ladder constraint strategy to obtain a target compressor frequency; and adjusting the compressor frequency of the dehumidifier based on the target compressor frequency; through the multi-parameter collaborative control of the compressor frequency of the dehumidifier by the influence parameters such as the evaporator temperature, the compressor discharge temperature, the ambient temperature, the AC voltage, the AC current and the compressor current, the dehumidification efficiency and the equipment operation stability are taken into account.

Description

Technical Field

[0001] This invention relates to the field of dehumidifiers, and more particularly to a compressor frequency control method for an inverter dehumidifier. Background Technology

[0002] Dehumidifiers, as an important air humidity control device, are widely used in homes, industries, warehouses, and other environments to improve air quality and prevent mold growth on items. Their core working principle is to lower the temperature of the evaporator coil through a refrigeration system, causing the temperature of the air flowing through it to drop below the dew point, thereby condensing water vapor and achieving dehumidification.

[0003] Currently, dehumidifiers on the market are mainly divided into two categories: fixed-frequency dehumidifiers and variable-frequency dehumidifiers.

[0004] Traditional fixed-frequency dehumidifiers use an ON / OFF control method, where the compressor operates at a fixed frequency. When the ambient humidity reaches the set value, the compressor stops working; when the humidity rises again, the compressor restarts. This control method has several inherent drawbacks: High energy consumption: The compressor draws a huge current at startup, and frequent start-stop cycles will significantly increase the power consumption of the whole machine and result in low energy efficiency.

[0005] Poor control precision: Due to the lag in the start and stop of the compressor, the ambient humidity fluctuates greatly around the set value, resulting in a poor user experience.

[0006] Poor low-temperature adaptability: In low-temperature and high-humidity environments, the surface of the evaporator coil is prone to frost formation. To ensure normal operation, the system must periodically interrupt the dehumidification process for defrosting, resulting in a sharp drop in dehumidification efficiency or even failure to operate.

[0007] To address the aforementioned issues with fixed-frequency dehumidifiers, the industry has gradually developed variable-frequency dehumidifiers. These use variable-frequency compressors, adjusting the compressor's operating frequency to change the cooling capacity output, theoretically enabling smoother capacity regulation and more stable humidity control. However, existing variable-frequency control schemes still have significant limitations: Single control strategy: Most solutions still use PID algorithms with humidity as the single control objective, lacking comprehensive perception of the system's operating status and multi-parameter collaborative management.

[0008] Insufficient environmental adaptability: The system exhibits poor stability when facing complex operating conditions with a wide temperature range (e.g., -10℃ to 45℃) and a wide voltage range (e.g., 160V to 280V). Under low-temperature conditions, a single anti-frost logic may lead to loss of dehumidification capacity or frequent defrosting. Under high-pressure or low-pressure conditions, the system may shut down or be damaged due to untimely protection.

[0009] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0010] The purpose of this invention is to provide a compressor frequency control method for a variable frequency dehumidifier, which aims to solve the technical problem of existing dehumidifiers that use humidity as the sole control target.

[0011] To achieve the above objectives, the solution provided by the present invention is as follows: A method for controlling the compressor frequency of a variable frequency dehumidifier includes: acquiring a user-set humidity value and an actual ambient humidity value, and calculating the humidity deviation; calculating a base compressor frequency based on the humidity deviation using a PID control algorithm; controlling the dehumidifier's compressor to operate at the base compressor frequency; acquiring influencing parameters, including evaporator temperature, compressor exhaust temperature, ambient temperature, AC voltage, AC current, and compressor current; correcting the base compressor frequency based on the influencing parameters using a preset multi-level step constraint strategy to obtain a target compressor frequency; and adjusting the dehumidifier's compressor frequency based on the target compressor frequency.

[0012] Preferably, the basic compressor frequency is defined as F. tb Then F tb Represented as:

[0013] In the formula, ΔH is the humidity deviation, and Kp, Ki, and Kd are proportionality coefficients.

[0014] Preferably, the step of correcting the base compressor frequency based on influencing parameters using a preset multi-level step-by-step constraint strategy to obtain the target compressor frequency includes: acquiring a preset multi-level step-by-step constraint strategy, wherein the multi-level step-by-step constraint strategy includes an evaporator low-temperature protection strategy, a compressor exhaust high-temperature protection strategy, an ambient temperature adaptive strategy, and an electrical parameter protection strategy; selecting a first compressor frequency control strategy corresponding to the evaporator temperature from the evaporator low-temperature protection strategy based on the evaporator temperature; selecting a second compressor frequency control strategy corresponding to the compressor exhaust temperature from the compressor exhaust high-temperature protection strategy based on the compressor exhaust temperature; selecting a third compressor frequency control strategy corresponding to the ambient temperature from the ambient temperature adaptive strategy based on the ambient temperature; selecting a fourth compressor frequency control strategy corresponding to the AC voltage from the electrical parameter protection strategy based on the AC voltage; and selecting a fifth compressor frequency control strategy corresponding to the AC current from the electrical parameter protection strategy based on the AC current. Based on the compressor current, a sixth compressor frequency control strategy corresponding to the compressor current is selected from the electrical parameter protection strategies. The first, second, third, fourth, fifth, and sixth compressor frequency control strategies each include at least one of the following strategies: immediate shutdown, rapid frequency reduction, slow frequency reduction, prohibition of frequency increase, slow frequency increase, and normal operation. When the first, second, third, fourth, fifth, and sixth compressor frequency control strategies are mutually exclusive, the compressor frequency control strategy with the highest priority is executed in the order of immediate shutdown > rapid frequency reduction > slow frequency reduction > prohibition of frequency increase > slow frequency increase > normal operation to correct the base compressor frequency and obtain the target compressor frequency.

[0015] Preferably, the evaporator low-temperature protection strategy includes: when the evaporator temperature > the fifth evaporation temperature threshold, the first compressor frequency control strategy is normal operation; when the fourth evaporation temperature threshold < the evaporator temperature ≤ the fifth evaporation temperature threshold, the first compressor frequency control strategy is slow frequency increase; when the third evaporation temperature threshold < the evaporator temperature ≤ the fourth evaporation temperature threshold, the first compressor frequency control strategy is to prohibit frequency increase; when the second evaporation temperature threshold < the evaporator temperature ≤ the third evaporation temperature threshold, the first compressor frequency control strategy is slow frequency decrease; when the first evaporation temperature threshold < the evaporator temperature ≤ the second evaporation temperature threshold, the first compressor frequency control strategy is rapid frequency decrease; when the evaporator temperature ≤ the first evaporation temperature threshold, the first compressor frequency control strategy is immediate shutdown.

[0016] Preferably, the first evaporation temperature threshold, the second evaporation temperature threshold, the third evaporation temperature threshold, the fourth evaporation temperature threshold, and the fifth evaporation temperature threshold are dynamic thresholds, and the first evaporation temperature threshold, the second evaporation temperature threshold, the third evaporation temperature threshold, the fourth evaporation temperature threshold, and the fifth evaporation temperature threshold are dynamically compensated according to the ambient temperature.

[0017] Preferably, the compressor exhaust high temperature protection strategy includes: when the compressor exhaust temperature is ≤ the first compressor exhaust temperature threshold, the second compressor frequency control strategy is normal operation; when the first compressor exhaust temperature threshold is < the compressor exhaust temperature threshold is ≤ the second compressor exhaust temperature threshold, the second compressor frequency control strategy is slow frequency increase; when the second compressor exhaust temperature threshold is < the compressor exhaust temperature threshold is ≤ the third compressor exhaust temperature threshold, the second compressor frequency control strategy is to prohibit frequency increase; when the third compressor exhaust temperature threshold is < the compressor exhaust temperature threshold is ≤ the fourth compressor exhaust temperature threshold, the second compressor frequency control strategy is slow frequency decrease; when the fourth compressor exhaust temperature threshold is < the compressor exhaust temperature threshold is ≤ the fifth compressor exhaust temperature threshold, the second compressor frequency control strategy is rapid frequency decrease; when the compressor exhaust temperature is > the fifth compressor exhaust temperature threshold, the second compressor frequency control strategy is immediate shutdown. Preferably, the ambient temperature adaptive strategy includes: when the ambient temperature is ≤ a first ambient temperature threshold, the third compressor frequency control strategy is to rapidly reduce the frequency according to a first decreasing frequency; when the first ambient temperature threshold is < the ambient temperature is ≤ a second ambient temperature threshold, the third compressor frequency control strategy is to slowly reduce the frequency according to a second decreasing frequency; when the second ambient temperature threshold is < the ambient temperature is ≤ a third ambient temperature threshold, the third compressor frequency control strategy is to operate normally; when the third ambient temperature threshold is < the ambient temperature is ≤ a fourth ambient temperature threshold, the third compressor frequency control strategy is to slowly reduce the frequency according to a third decreasing frequency; and when the ambient temperature is > a fourth ambient temperature threshold, the third compressor frequency control strategy is to rapidly reduce the frequency according to a fourth decreasing frequency.

[0018] Preferably, the AC voltage strategy includes: when the AC voltage is ≤ a first AC voltage threshold, the fourth compressor frequency control strategy is to immediately stop; when the first AC voltage threshold < AC voltage ≤ a second AC voltage threshold, the fourth compressor frequency control strategy is to rapidly reduce the frequency; when the second AC voltage threshold < AC voltage ≤ a third AC voltage threshold, the fourth compressor frequency control strategy is to slowly reduce the frequency according to a fifth decreasing frequency; when the third AC voltage threshold < AC voltage ≤ a fourth AC voltage threshold, the fourth compressor frequency control strategy is to operate normally; when the fourth AC voltage threshold < AC voltage ≤ a fifth AC voltage threshold, the fourth compressor frequency control strategy is to slowly reduce the frequency according to a sixth decreasing frequency; and when the AC voltage > a fifth AC voltage threshold, the fourth compressor frequency control strategy is to immediately stop.

[0019] Preferably, the AC current strategy includes: when the AC current is ≤ a first AC current threshold, the fifth compressor frequency control strategy is normal operation; when the first AC current threshold < AC current ≤ a second AC current threshold, the fifth compressor frequency control strategy is slow frequency increase; when the second AC current threshold < AC current ≤ a third AC current threshold, the fifth compressor frequency control strategy is normal operation; when the third AC current threshold < AC current ≤ a fourth AC current threshold, the fifth compressor frequency control strategy is frequency prohibition; when the fourth AC current threshold < AC current ≤ a fifth AC current threshold, the fifth compressor frequency control strategy is slow frequency decrease; and when the AC current > a fifth AC current threshold, the fifth compressor frequency control strategy is immediate shutdown. Preferably, the compressor current strategy includes: when the compressor current is less than or equal to a first compressor current threshold, the sixth compressor frequency control strategy is normal operation; when the first compressor current threshold is less than or equal to a second compressor current threshold, the sixth compressor frequency control strategy is slow frequency increase; when the second compressor current threshold is less than or equal to a third compressor current threshold, the sixth compressor frequency control strategy is normal operation; when the third compressor current threshold is less than or equal to a fourth compressor current threshold, the sixth compressor frequency control strategy is frequency prohibition; when the fourth compressor current threshold is less than or equal to a fifth compressor current threshold, the sixth compressor frequency control strategy is rapid frequency decrease; and when the compressor current is greater than or equal to a fifth compressor current threshold, the sixth compressor frequency control strategy is immediate shutdown.

[0020] This solution calculates the deviation between the user-set humidity and the actual ambient humidity, and uses a PID control algorithm to calculate the base compressor frequency. Then, it combines key influencing parameters such as evaporator temperature, compressor exhaust temperature, ambient temperature, AC voltage, AC current, and compressor current. A pre-defined multi-level stepped constraint strategy is used to dynamically correct the base frequency to determine the target frequency. Finally, the compressor operation is adjusted according to the target frequency. This achieves precise humidity control through the PID algorithm, effectively ensuring the dehumidification effect matches user needs. Furthermore, the multi-level stepped constraint strategy for multi-dimensional influencing parameters constructs a protection mechanism under all operating conditions, specifically addressing issues such as low-temperature frosting, high-temperature overheating, voltage fluctuations, and current overload. Simultaneously, the hierarchical control logic, through base frequency calculation and multi-parameter correction, balances dehumidification efficiency and equipment operational stability, avoiding defects such as overshoot, oscillation, or untimely protection in single control modes. This improves the dehumidifier's adaptability and reliability under complex operating conditions such as wide temperature ranges and wide voltage ranges, achieving synergistic optimization of dehumidification performance, energy consumption control, and equipment lifespan. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 This is a compressor frequency control method for a variable frequency dehumidifier provided in an embodiment of the present invention. Detailed Implementation

[0023] The terms "first," "second," "third," "fourth," etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" or "having" and any variations thereof are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0024] For ease of understanding, the specific process of the embodiments of the present invention is described below. Please refer to [link / reference]. Figure 1 In this embodiment of the invention, a compressor frequency control method for a variable frequency dehumidifier includes: S101. Obtain the user-set humidity value and the actual ambient humidity value, and calculate the humidity deviation; S102. Calculate the base compressor frequency based on the humidity deviation using a PID control algorithm; S103. Control the dehumidifier compressor to operate at the basic compressor frequency; S104. Obtain the influencing parameters, including evaporator temperature, compressor discharge temperature, ambient temperature, AC voltage, AC current, and compressor current. S105. Based on the aforementioned influencing parameters, the base compressor frequency is corrected using a preset multi-level step constraint strategy to obtain the target compressor frequency. S106. Adjust the compressor frequency of the dehumidifier based on the target compressor frequency.

[0025] In this embodiment, in step S101, the actual ambient humidity is detected by a humidity sensor. The humidity sensor is typically installed at the air inlet of the dehumidifier or on the exterior of the unit. The humidity sensor is a capacitive polymer thin-film humidity sensor.

[0026] Humidity deviation = User-set humidity value - Actual ambient humidity value.

[0027] In this embodiment, in step S102, it is assumed that the basic compressor frequency is expressed as F. tb Then F tb Represented as:

[0028] In the formula, ΔH is the humidity deviation, and Kp, Ki, and Kd are proportional coefficients. Kp, Ki, and Kd are adjusted according to the specific model of the dehumidifier. Usually, Ki and Kd have relatively small weights to avoid overshoot and oscillation.

[0029] In this embodiment, the proportional (P) element is used to address the current deviation. .

[0030] It responds immediately to the current humidity deviation. The greater the deviation, the stronger the controller's output. If the environment is very humid ( (very large) Output a very high value to command the compressor to run at high speed immediately for rapid dehumidification.

[0031] The integral (I) stage is used to eliminate historical cumulative bias. .

[0032] Used to eliminate steady-state error. It accumulates all past deviation information. As long as there is still a tiny deviation, the integral term will continue to increase (or decrease) its output until the deviation is completely corrected to zero.

[0033] When the humidity approaches the set value ( When the humidity is very low, the proportional term has a weak effect. At this point, the integral term begins to dominate, fine-tuning the compressor frequency to precisely adjust the humidity to the target value (e.g., 50.0%RH).

[0034] The differential (D) stage is used to predict future deviation trends. ,Right now .

[0035] Used to suppress overshoot, stabilize the system, and monitor the rate and direction of deviation changes. If the humidity is rapidly approaching the setpoint, the derivative term generates a counterforce to prevent it from overshooting the setpoint due to inertia, thereby reducing oscillations and allowing the system to converge more smoothly.

[0036] When the dehumidifier first starts working and the humidity drops rapidly... It is a large positive value, and the differential term outputs a negative value, which appropriately suppresses the frequency spikes caused by the proportional and integral terms, making the compressor accelerate more smoothly.

[0037] The proportional (P) stage, integral (I) stage, differential (D) stage, and the synthesized final output F tb .

[0038] In this embodiment, a humidity deviation > 0 indicates that the environment is too dry. For example, the user sets the RH to 50%, but the actual ambient humidity is only 40%RH. This means the dehumidification demand is negative, and dehumidification should be stopped or its capacity reduced.

[0039] When the humidity deviation is 0, it means that the current humidity has just reached the set value, which is an ideal state. The compressor of the inverter dehumidifier maintains the current state and outputs a frequency value that can accurately match the current humidity load of the space.

[0040] A humidity deviation greater than 0 indicates that the environment is too humid. For example, if a user sets the RH to 50%, but the current ambient RH is as high as 70%, this signals the need for dehumidification. The larger the absolute value of the humidity deviation, the more urgent the dehumidification need, and the greater the required cooling capacity. Therefore, a higher F is calculated. tb This drives the compressor to run faster.

[0041] In this embodiment, in step S104, a negative temperature coefficient (NTC) thermistor is used to obtain the evaporator temperature. The NTC thermistor is closely attached to the elbow or middle surface of the evaporator coil (U-shaped copper tube), and thermal grease and clamps are typically used to ensure good thermal contact in order to accurately reflect the refrigerant evaporation temperature.

[0042] In this embodiment, an NTC thermistor or a PT1000 platinum resistance thermometer is used to obtain the compressor discharge temperature. The NTC thermistor or PT1000 platinum resistance thermometer is installed on the discharge pipe between the compressor discharge port and the condenser. It usually needs to be inserted into the pipe with a metal sleeve or tightly fitted to the pipe wall to withstand high temperature and high pressure.

[0043] In this embodiment, an NTC thermistor is used to obtain the ambient temperature. The NTC thermistor is installed inside the air inlet grille of the dehumidifier or on the outside of the unit to ensure that the true temperature of the circulating air can be sensed and to avoid being affected by the heat inside the unit.

[0044] In this embodiment, AC voltage sampling involves attenuating the mains voltage (220VAC) to a low voltage range (e.g., 0-3.3V) that can be safely read by the MCU's ADC through a high-voltage resistor divider network. Simultaneously, an operational amplifier is used for signal conditioning and isolation.

[0045] Current sampling: Using a current transformer (CT) or Hall current sensor attached to the live or neutral wire, the current transformer (CT) or Hall current sensor can output a voltage signal proportional to the alternating current without contact.

[0046] Since it is an AC signal, the MCU needs to perform high-speed sampling (thousands of times per second) through the ADC, and then obtain the effective values ​​of voltage and current through algorithms (such as root mean square (RMS) calculation).

[0047] In this embodiment, the sampling method for compressor current is similar to that for AC current, but the sampling point is specific to the power supply circuit of the compressor, that is, the sensor needs to be installed on the line from the inverter board to the compressor.

[0048] In this embodiment, in step S105, based on the influencing parameters, the base compressor frequency is corrected using a preset multi-level step constraint strategy to obtain the target compressor frequency, including: Obtain the preset multi-level step constraint strategy, which includes evaporator low temperature protection strategy, compressor exhaust high temperature protection strategy, ambient temperature adaptive strategy, and electrical parameter protection strategy; Based on the evaporator temperature, a first compressor frequency control strategy corresponding to the evaporator temperature is selected from the evaporator low-temperature protection strategy; based on the compressor discharge temperature, a second compressor frequency control strategy corresponding to the compressor discharge temperature is selected from the compressor discharge high-temperature protection strategy; based on the ambient temperature, a third compressor frequency control strategy corresponding to the ambient temperature is selected from the ambient temperature adaptive strategy; based on the AC voltage, a fourth compressor frequency control strategy corresponding to the AC voltage is selected from the electrical parameter protection strategy; based on the AC current, a fifth compressor frequency control strategy corresponding to the AC current is selected from the electrical parameter protection strategy; and based on the compressor current, a sixth compressor frequency control strategy corresponding to the compressor current is selected from the electrical parameter protection strategy. Each of the first, second, third, fourth, fifth, and sixth compressor frequency control strategies includes at least one of the following strategies: immediate shutdown, rapid frequency reduction, slow frequency reduction, prohibition of frequency increase, slow frequency increase, or normal operation. When the frequency control strategies of the first, second, third, fourth, fifth, and sixth compressors are mutually exclusive, the compressor frequency control strategy with the highest priority is executed in the following priority order: immediate shutdown > rapid frequency reduction > slow frequency reduction > prohibition of frequency increase > slow frequency increase > normal operation, in order to correct the base compressor frequency and obtain the target compressor frequency.

[0049] In this embodiment, the evaporator low-temperature protection strategy aims to protect the evaporator from freezing and prevent defrosting. While ensuring the evaporator does not frost, the evaporation temperature is lowered as much as possible to improve dehumidification efficiency. The greater the temperature difference, the more air is cooled, and the more moisture is precipitated.

[0050] The evaporator low-temperature protection strategy includes the following: when the evaporator temperature > the fifth evaporation temperature threshold, the first compressor frequency control strategy is normal operation; when the fourth evaporation temperature threshold < the evaporator temperature ≤ the fifth evaporation temperature threshold, the first compressor frequency control strategy is slow frequency increase; when the third evaporation temperature threshold < the evaporator temperature ≤ the fourth evaporation temperature threshold, the first compressor frequency control strategy is to prohibit frequency increase; when the second evaporation temperature threshold < the evaporator temperature ≤ the third evaporation temperature threshold, the first compressor frequency control strategy is slow frequency decrease; when the first evaporation temperature threshold < the evaporator temperature ≤ the second evaporation temperature threshold, the first compressor frequency control strategy is rapid frequency decrease; when the evaporator temperature ≤ the first evaporation temperature threshold, the first compressor frequency control strategy is immediate shutdown. After shutdown, the compressor can only be restarted if the evaporator temperature ≥ the third evaporation temperature threshold. Please refer to Table 1 for details.

[0051] Table 1 Evaporator Low Temperature Protection Strategy

[0052] In this embodiment, normal operation means operating at the base compressor frequency.

[0053] Understandably, the first, second, third, fourth, and fifth evaporation temperature thresholds are set according to actual conditions. In this embodiment, the first evaporation temperature threshold is -1℃, the second evaporation temperature threshold is 1℃, the third evaporation temperature threshold is 3℃, the fourth evaporation temperature threshold is 5℃, and the fifth evaporation temperature threshold is 7℃.

[0054] Furthermore, the first evaporation temperature threshold, the second evaporation temperature threshold, the third evaporation temperature threshold, the fourth evaporation temperature threshold, and the fifth evaporation temperature threshold are dynamic thresholds, which are dynamically compensated according to the ambient temperature.

[0055] For example, the first evaporation temperature threshold = the first evaporation temperature preset threshold + K1 × (ambient temperature - preset reference ambient temperature). Similarly, the compensation methods for the second, third, fourth and fifth evaporation temperature thresholds are the same.

[0056] Specifically, assuming a preset baseline ambient temperature of 10℃, K1 of 0.7, and a preset threshold for the first evaporation temperature of -1℃, then at an ambient temperature of 5℃, the first evaporation temperature threshold = -1 + 0.7 × (5 - 10) = -4.5℃, indicating that the evaporation temperature can operate at a lower level in low-temperature environments, thereby delaying protection intervention and maintaining dehumidification capacity. At an ambient temperature of 30℃, the first evaporation temperature threshold = -1 + 0.7 × (30 - 10) = 13℃, indicating that in high-temperature environments, protection is initiated earlier to prevent excessive condensation or reduced efficiency.

[0057] In this embodiment, the compressor exhaust high-temperature protection strategy is to prevent overheating damage or lubricant carbonization. While ensuring the compressor does not overheat, the compressor exhaust temperature is increased as much as possible to improve dehumidification power. Higher power results in a larger temperature difference, more air cooling, and more moisture condensation.

[0058] The compressor discharge high-temperature protection strategy includes the following: when the compressor discharge temperature is ≤ the first compressor discharge temperature threshold, the second compressor frequency control strategy is normal operation; when the first compressor discharge temperature threshold < the second compressor discharge temperature threshold, the second compressor frequency control strategy is slow frequency increase; when the second compressor discharge temperature threshold < the third compressor discharge temperature threshold, the second compressor frequency control strategy is to prohibit frequency increase; when the third compressor discharge temperature threshold < the fourth compressor discharge temperature threshold, the second compressor frequency control strategy is slow frequency decrease; when the fourth compressor discharge temperature threshold < the fifth compressor discharge temperature threshold, the second compressor frequency control strategy is rapid frequency decrease; when the compressor discharge temperature > the fifth compressor discharge temperature threshold, the second compressor frequency control strategy is immediate shutdown. After shutdown, restart is only allowed if the compressor discharge temperature is ≤ the third compressor discharge temperature threshold. Please refer to Table 2 for details.

[0059] Table 2 High Temperature Protection Strategy for Compressor Exhaust

[0060] Understandably, the discharge temperature thresholds for the first, second, third, fourth, and fifth compressors are set according to actual conditions. In this embodiment, the discharge temperature threshold for the first compressor is 75°C, the discharge temperature threshold for the second compressor is 80°C, the discharge temperature threshold for the third compressor is 85°C, the discharge temperature threshold for the fourth compressor is 90°C, and the discharge temperature threshold for the fifth compressor is 95°C.

[0061] In this embodiment, the ambient temperature adaptive strategy is used to avoid frequent protection. The ambient temperature, evaporator temperature, and compressor exhaust temperature are controlled in conjunction to prevent frequent defrosting at low temperatures and frequent protection at high temperatures.

[0062] The ambient temperature adaptive strategy includes the following: when the ambient temperature is ≤ the first ambient temperature threshold, the third compressor frequency control strategy is to rapidly reduce the frequency according to the first decreasing frequency; when the first ambient temperature threshold < the ambient temperature ≤ the second ambient temperature threshold, the third compressor frequency control strategy is to slowly reduce the frequency according to the second decreasing frequency; when the second ambient temperature threshold < the ambient temperature ≤ the third ambient temperature threshold, the third compressor frequency control strategy is to operate normally; when the third ambient temperature threshold < the ambient temperature ≤ the fourth ambient temperature threshold, the third compressor frequency control strategy is to slowly reduce the frequency according to the third decreasing frequency; when the ambient temperature > the fourth ambient temperature threshold, the third compressor frequency control strategy is to rapidly reduce the frequency according to the fourth decreasing frequency. Restarting is only permitted after shutdown if the ambient temperature is ≤ the third ambient temperature threshold. Please refer to Table 3 for details.

[0063] Table 3 Adaptive Strategy for Ambient Temperature

[0064] Understandably, the first, second, third, and fourth ambient temperature thresholds are set according to actual conditions. In this embodiment, the first ambient temperature threshold is 5°C, the second ambient temperature threshold is 10°C, the third ambient temperature threshold is 25°C, and the fourth ambient temperature threshold is 35°C.

[0065] In this embodiment, the electrical parameter protection strategy includes an AC voltage strategy, an AC current strategy, and a compressor current strategy.

[0066] The AC voltage strategy is designed to prevent equipment damage from grid voltage fluctuations and to avoid compressor or circuit damage caused by current overload. It adaptively adjusts the operating status when voltage / current is abnormal to ensure that the base compressor frequency does not exceed its maximum allowable frequency or current limit.

[0067] The AC voltage control strategy includes the following: when the AC voltage is less than or equal to the first AC voltage threshold, the fourth compressor frequency control strategy is immediate shutdown; when the first AC voltage threshold is less than or equal to the second AC voltage threshold, the fourth compressor frequency control strategy is rapid frequency reduction; when the second AC voltage threshold is less than or equal to the third AC voltage threshold, the fourth compressor frequency control strategy is slow frequency reduction according to the fifth frequency reduction; when the third AC voltage threshold is less than or equal to the fourth AC voltage threshold, the fourth compressor frequency control strategy is normal operation; when the fourth AC voltage threshold is less than or equal to the fifth AC voltage threshold, the fourth compressor frequency control strategy is slow frequency reduction according to the sixth frequency reduction; and when the AC voltage is greater than the fifth AC voltage threshold, the fourth compressor frequency control strategy is immediate shutdown. After shutdown, the compressor discharge temperature must be less than or equal to the third compressor discharge temperature threshold before restarting is allowed. Please refer to Table 4 for details.

[0068] Table 4 AC Voltage Strategy

[0069] Understandably, the first, second, third, fourth, and fifth AC voltage thresholds are set according to actual conditions. In this embodiment, the first AC voltage threshold is 175V, the second AC voltage threshold is 185V, the third AC voltage threshold is 200V, the fourth AC voltage threshold is 240V, and the fifth AC voltage threshold is 260V.

[0070] In this embodiment, the AC current control strategy includes: when the AC current is less than or equal to a first AC current threshold, the fifth compressor frequency control strategy is normal operation; when the first AC current threshold is less than or equal to a second AC current threshold, the fifth compressor frequency control strategy is slow frequency increase; when the second AC current threshold is less than or equal to a third AC current threshold, the fifth compressor frequency control strategy is normal operation; when the third AC current threshold is less than or equal to a fourth AC current threshold, the fifth compressor frequency control strategy prohibits frequency increase; when the fourth AC current threshold is less than or equal to a fifth AC current threshold, the fifth compressor frequency control strategy is slow frequency decrease; and when the AC current is greater than the fifth AC current threshold, the fifth compressor frequency control strategy is immediate shutdown. After shutdown, the AC current must drop below the third AC current threshold and a 2-minute delay is required before restarting is allowed. See Table 5 for details.

[0071] Table 5 AC Current Strategy

[0072] Understandably, the first, second, third, fourth, and fifth AC current thresholds are set according to actual conditions. In this embodiment, the first AC current threshold is 2A, the second AC current threshold is 3A, the third AC current threshold is 4A, the fourth AC current threshold is 5A, and the fifth AC current threshold is 6A.

[0073] Furthermore, the first AC current threshold, the second AC current threshold, the third AC current threshold, the fourth AC current threshold, and the fifth AC current threshold are dynamic thresholds, which are dynamically compensated according to the ambient temperature.

[0074] For example, the first AC current threshold = the first AC current preset threshold × (1 + K2 × (ambient temperature - preset activation temperature)). Similarly, the compensation methods for the second AC current threshold, the third AC current threshold, the fourth AC current threshold and the fifth AC current threshold are the same.

[0075] Specifically, assuming the preset activation temperature is 35℃, K2 is 0.03, and the preset threshold of the first AC current is 2A, then when the ambient temperature is 40℃, the first AC current threshold = 2×(1+0.03×(40-35)) = 2.3A, which allows the compressor to bear a higher load under extreme high temperature conditions in order to prioritize dehumidification performance.

[0076] In this embodiment, the compressor current control strategy includes: when the compressor current is less than or equal to the first compressor current threshold, the sixth compressor frequency control strategy is normal operation; when the first compressor current threshold is less than or equal to the second compressor current threshold, the sixth compressor frequency control strategy is slow frequency increase; when the second compressor current threshold is less than or equal to the third compressor current threshold, the sixth compressor frequency control strategy is normal operation; when the third compressor current threshold is less than or equal to the fourth compressor current threshold, the sixth compressor frequency control strategy prohibits frequency increase; when the fourth compressor current threshold is less than or equal to the fifth compressor current threshold, the sixth compressor frequency control strategy is rapid frequency decrease; and when the compressor current is greater than or equal to the fifth compressor current threshold, the sixth compressor frequency control strategy is immediate shutdown. After shutdown, the compressor current must drop below the third compressor current threshold and a 3-minute delay is required before restarting is allowed. See Table 6 for details.

[0077] Table 6 Compressor Current Strategy

[0078] Understandably, the first compressor current threshold, the second compressor current threshold, the third compressor current threshold, the fourth compressor current threshold, and the fifth compressor current threshold are set according to actual conditions. In this embodiment, the first compressor current threshold is 1A, the second compressor current threshold is 2A, the third compressor current threshold is 3A, the fourth compressor current threshold is 4A, and the fifth compressor current threshold is 5A.

[0079] Furthermore, the first compressor current threshold, the second compressor current threshold, the third compressor current threshold, the fourth compressor current threshold, and the fifth compressor current threshold are dynamic thresholds, which are dynamically compensated according to the ambient temperature.

[0080] For example, the first compressor current threshold = the first compressor current preset threshold × (1 + K2 × (ambient temperature - preset activation temperature)). Similarly, the compensation methods for the second compressor current threshold, the third compressor current threshold, the fourth compressor current threshold and the fifth compressor current threshold are the same.

[0081] Specifically, assuming the preset activation temperature is 35℃, K2 is 0.03, and the preset threshold of the first AC current is 1A, then when the ambient temperature is 40℃, the first AC current threshold = 1×(1+0.03×(40-35))=1.15A, which allows the compressor to bear a higher load under extreme high temperature conditions in order to prioritize dehumidification performance.

[0082] For example, assume the following operating conditions: Environmental conditions: High temperature and high humidity environment, ambient temperature = 38°C, actual ambient humidity = 70%RH.

[0083] User setting: User set humidity = 50%RH.

[0084] Power grid status: The power grid voltage is too high, AC voltage = 255V.

[0085] System operating status: The compressor of the inverter dehumidifier has been running for a period of time, and the system is under high load.

[0086] Evaporator temperature = 10°C (safe) The compressor discharge temperature is 102°C (extremely high, nearing the danger zone!). Alternating current = 5.2A (too high). The compressor current is 4.2A (too high).

[0087] First, calculate the humidity deviation and the base compressor frequency.

[0088] Humidity deviation ΔH = 50% - 70% = -20%RH, a negative value indicates that dehumidification is still required.

[0089] The basic compressor frequency was calculated to be 75Hz using a PID control algorithm.

[0090] Next, a multi-level step constraint strategy is applied to correct the frequency of the base compressor.

[0091] Among the influencing factors, the evaporator temperature is 10°C, the compressor discharge temperature is 102°C, the ambient temperature is 38°C, the AC voltage is 255V, the AC current is 5.2A, and the compressor current is 4.2A. Therefore, the first compressor frequency control strategy is normal operation, the second compressor frequency control strategy is immediate shutdown, the third compressor frequency control strategy is rapid frequency reduction according to the fourth frequency reduction, the fourth compressor frequency control strategy is slow frequency reduction according to the sixth frequency reduction, the fifth compressor frequency control strategy is slow frequency reduction, and the sixth compressor frequency control strategy is rapid frequency reduction. According to the priority rule of immediate shutdown > all other instructions, the base compressor frequency is corrected through the second compressor frequency control strategy to obtain the target compressor frequency of 0Hz, that is, immediate shutdown.

[0092] In the example above, the initial requirement was that the humidity deviation was still large. The PID control algorithm calculated the basic compressor frequency to be 75Hz. However, the performance requirement (high-frequency dehumidification) and the safety requirement (preventing the compressor from burning out) were in serious conflict. Therefore, the basic compressor frequency was corrected to obtain the target compressor frequency of 0Hz, which means immediate shutdown. This indicates that safety is the absolute priority. The exhaust temperature of 102°C has far exceeded the safety red line, triggering the highest level of immediate shutdown protection. All dehumidification performance requirements were abandoned, and the safety of the compressor was given priority.

[0093] For example, assume the following operating conditions: Environmental conditions: Low temperature and medium humidity environment, ambient temperature = 8°C, actual ambient humidity = 65%RH.

[0094] User setting: User set humidity = 50%RH.

[0095] Power grid status: The power grid voltage is low, AC voltage = 180V.

[0096] System operating status: The compressor has been running for some time.

[0097] Evaporator temperature = 2°C (close to the frosting point).

[0098] The compressor discharge temperature is 82°C (a bit high, but within the safe range).

[0099] Alternating current = 4.5A (medium load).

[0100] Compressor current = 3.5A (medium load).

[0101] First, calculate the humidity deviation and the base compressor frequency.

[0102] Humidity deviation ΔH = 50% - 65% = -15%RH, a negative value indicates that dehumidification is required.

[0103] The basic compressor frequency was calculated to be 60Hz using a PID control algorithm.

[0104] Next, a multi-level step constraint strategy is applied to correct the frequency of the base compressor.

[0105] Among the influencing factors, the evaporator temperature is 2°C, the compressor discharge temperature is 82°C, the ambient temperature is 8°C, the AC voltage is 180V, the AC current is 4.5A, and the compressor current is 3.5A. Therefore, the first compressor frequency control strategy is slow frequency reduction, the second compressor frequency control strategy is to prohibit frequency increase (maintain the current frequency, allow frequency decrease), the third compressor frequency control strategy is slow frequency reduction, the fourth compressor frequency control strategy is rapid frequency reduction, the fifth compressor frequency control strategy is to prohibit frequency increase, and the sixth compressor frequency control strategy is to prohibit frequency increase. Based on the priority order of immediate shutdown > rapid frequency reduction > slow frequency reduction > prohibit frequency increase > slow frequency increase > normal operation, rapid frequency reduction has the highest priority. The base compressor frequency is corrected according to the fourth compressor frequency control strategy (-2Hz / second) to obtain the target compressor frequency. Assuming the control cycle is 1 second, the target compressor frequency = 60Hz + (-2Hz) = 58Hz.

[0106] In the example above, the initial required humidity deviation is -15%RH. The PID control algorithm calculates a base compressor frequency of 60Hz. However, multiple conflicts arise between performance requirements (60Hz dehumidification) and reliability requirements (preventing damage from low-pressure operation, preventing evaporator frosting, and preventing compressor overheating). Low pressure (180V) is the primary conflict, requiring rapid frequency reduction to protect the circuitry and compressor motor. Low evaporation temperature (2°C) and ambient temperature (8°C) are secondary conflicts, requiring slow frequency reduction to prevent frosting. High exhaust temperature, AC current, and compressor current all necessitate that the system load cannot be increased further (an increase is prohibited). Therefore, the base compressor frequency of 60Hz is corrected to obtain a target compressor frequency of 58Hz.

[0107] In this embodiment, the deviation between the user-set humidity and the actual ambient humidity is calculated, and the base compressor frequency is calculated using a PID control algorithm. Then, key influencing parameters such as evaporator temperature, compressor exhaust temperature, ambient temperature, AC voltage, AC current, and compressor current are combined. A preset multi-level stepped constraint strategy is used to dynamically correct the base frequency to determine the target frequency. Finally, the compressor operation is adjusted according to the target frequency. This achieves precise humidity control through the PID algorithm, effectively ensuring the dehumidification effect matches user needs. Furthermore, the multi-level stepped constraint strategy for multi-dimensional influencing parameters constructs a protection mechanism under all operating conditions, specifically addressing issues such as low-temperature frosting, high-temperature overheating, voltage fluctuations, and current overload. Simultaneously, the hierarchical control logic, through base frequency calculation and multi-parameter correction, balances dehumidification efficiency and equipment operational stability, avoiding defects such as overshoot, oscillation, or untimely protection in single control modes. This improves the dehumidifier's adaptability and reliability under complex operating conditions such as wide temperature ranges and wide voltage ranges, achieving synergistic optimization of dehumidification performance, energy consumption control, and equipment lifespan.

[0108] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method of controlling the frequency of a compressor of a variable speed dehumidifier, characterized by, include: Obtain the user-set humidity value and the actual ambient humidity value, and calculate the humidity deviation; The base compressor frequency is calculated based on the humidity deviation using a PID control algorithm. The dehumidifier's compressor is controlled to operate at the aforementioned basic compressor frequency; Obtain influencing parameters, including evaporator temperature, compressor discharge temperature, ambient temperature, AC voltage, AC current, and compressor current; Based on the aforementioned influencing parameters, the base compressor frequency is corrected using a preset multi-level step constraint strategy to obtain the target compressor frequency. Adjust the compressor frequency of the dehumidifier based on the target compressor frequency; The step of correcting the base compressor frequency based on influencing parameters using a preset multi-level stepped constraint strategy to obtain the target compressor frequency includes: acquiring a preset multi-level stepped constraint strategy, which includes an evaporator low-temperature protection strategy, a compressor exhaust high-temperature protection strategy, an ambient temperature adaptive strategy, and an electrical parameter protection strategy; selecting a first compressor frequency control strategy corresponding to the evaporator temperature from the evaporator low-temperature protection strategy based on the evaporator temperature; selecting a second compressor frequency control strategy corresponding to the compressor exhaust temperature from the compressor exhaust high-temperature protection strategy based on the compressor exhaust temperature; selecting a third compressor frequency control strategy corresponding to the ambient temperature from the ambient temperature adaptive strategy based on the ambient temperature; selecting a fourth compressor frequency control strategy corresponding to the AC voltage from the electrical parameter protection strategy based on the AC voltage; and selecting a fifth compressor frequency control strategy corresponding to the AC current from the electrical parameter protection strategy based on the AC current. Based on the compressor current, a sixth compressor frequency control strategy corresponding to the compressor current is selected from the electrical parameter protection strategies. The first, second, third, fourth, fifth, and sixth compressor frequency control strategies each include at least one of the following strategies: immediate shutdown, rapid frequency reduction, slow frequency reduction, prohibition of frequency increase, slow frequency increase, and normal operation. When the first, second, third, fourth, fifth, and sixth compressor frequency control strategies are mutually exclusive, the compressor frequency control strategy with the highest priority is executed in the order of immediate shutdown > rapid frequency reduction > slow frequency reduction > prohibition of frequency increase > slow frequency increase > normal operation to correct the base compressor frequency and obtain the target compressor frequency.

2. The method of claim 1, wherein the frequency of the compressor is controlled by a variable frequency drive (VFD) of the compressor. The base compressor frequency is defined as F tb F = 60 / N tb is expressed as: In the formula, ΔH is the humidity deviation, and Kp, Ki, and Kd are proportionality coefficients.

3. The method of claim 1, wherein the frequency of the compressor is controlled by a variable frequency drive (VFD) of the compressor. The evaporator low-temperature protection strategy includes: when the evaporator temperature > the fifth evaporation temperature threshold, the first compressor frequency control strategy is normal operation; when the fourth evaporation temperature threshold < the evaporator temperature ≤ the fifth evaporation temperature threshold, the first compressor frequency control strategy is slow frequency increase; when the third evaporation temperature threshold < the evaporator temperature ≤ the fourth evaporation temperature threshold, the first compressor frequency control strategy is to prohibit frequency increase; when the second evaporation temperature threshold < the evaporator temperature ≤ the third evaporation temperature threshold, the first compressor frequency control strategy is slow frequency decrease; when the first evaporation temperature threshold < the evaporator temperature ≤ the second evaporation temperature threshold, the first compressor frequency control strategy is rapid frequency decrease; when the evaporator temperature ≤ the first evaporation temperature threshold, the first compressor frequency control strategy is immediate shutdown.

4. The method of claim 3, wherein the frequency of the compressor is controlled by the microcomputer according to the temperature of the indoor heat exchanger and the temperature of the outdoor heat exchanger. The first evaporation temperature threshold, the second evaporation temperature threshold, the third evaporation temperature threshold, the fourth evaporation temperature threshold, and the fifth evaporation temperature threshold are dynamic thresholds, and the first evaporation temperature threshold, the second evaporation temperature threshold, the third evaporation temperature threshold, the fourth evaporation temperature threshold, and the fifth evaporation temperature threshold are dynamically compensated according to the ambient temperature.

5. The method of claim 1, wherein the frequency of the compressor is controlled by a variable frequency drive (VFD) of the compressor. The compressor exhaust high-temperature protection strategy includes: when the compressor exhaust temperature is ≤ the first compressor exhaust temperature threshold, the second compressor frequency control strategy is normal operation; when the first compressor exhaust temperature threshold is < the compressor exhaust temperature threshold is ≤ the second compressor exhaust temperature threshold, the second compressor frequency control strategy is slow frequency increase; when the second compressor exhaust temperature threshold is < the compressor exhaust temperature threshold is ≤ the third compressor exhaust temperature threshold, the second compressor frequency control strategy is to prohibit frequency increase; when the third compressor exhaust temperature threshold is < the compressor exhaust temperature threshold is ≤ the fourth compressor exhaust temperature threshold, the second compressor frequency control strategy is slow frequency decrease; when the fourth compressor exhaust temperature threshold is < the compressor exhaust temperature threshold is ≤ the fifth compressor exhaust temperature threshold, the second compressor frequency control strategy is rapid frequency decrease; when the compressor exhaust temperature is > the fifth compressor exhaust temperature threshold, the second compressor frequency control strategy is immediate shutdown.

6. The method of claim 1, wherein the frequency of the compressor is controlled by a variable frequency drive (VFD) of the compressor. The ambient temperature adaptive strategy includes: when the ambient temperature is ≤ a first ambient temperature threshold, the third compressor frequency control strategy is to rapidly reduce the frequency according to a first decreasing frequency; when the first ambient temperature threshold is < the ambient temperature is ≤ a second ambient temperature threshold, the third compressor frequency control strategy is to slowly reduce the frequency according to a second decreasing frequency; when the second ambient temperature threshold is < the ambient temperature is ≤ a third ambient temperature threshold, the third compressor frequency control strategy is to operate normally; when the third ambient temperature threshold is < the ambient temperature is ≤ a fourth ambient temperature threshold, the third compressor frequency control strategy is to slowly reduce the frequency according to a third decreasing frequency; and when the ambient temperature is > a fourth ambient temperature threshold, the third compressor frequency control strategy is to rapidly reduce the frequency according to a fourth decreasing frequency.

7. The method of claim 1, wherein the frequency of the compressor is controlled by a variable frequency drive (VFD) of the compressor. The AC voltage control strategy includes: when the AC voltage is less than or equal to a first AC voltage threshold, the fourth compressor frequency control strategy is to immediately shut down; when the first AC voltage threshold is less than or equal to a second AC voltage threshold, the fourth compressor frequency control strategy is to rapidly reduce the frequency; when the second AC voltage threshold is less than or equal to a third AC voltage threshold, the fourth compressor frequency control strategy is to slowly reduce the frequency according to a fifth decreasing frequency; when the third AC voltage threshold is less than or equal to a fourth AC voltage threshold, the fourth compressor frequency control strategy is to operate normally; when the fourth AC voltage threshold is less than or equal to a fifth AC voltage threshold, the fourth compressor frequency control strategy is to slowly reduce the frequency according to a sixth decreasing frequency; and when the AC voltage is greater than or equal to a fifth AC voltage threshold, the fourth compressor frequency control strategy is to immediately shut down.

8. The method of claim 1, wherein the frequency of the compressor is controlled by a variable frequency drive (VFD) of the compressor. The AC current control strategy includes: when the AC current is less than or equal to a first AC current threshold, the fifth compressor frequency control strategy is normal operation; when the first AC current threshold is less than or equal to a second AC current threshold, the fifth compressor frequency control strategy is to slowly increase the frequency; when the second AC current threshold is less than or equal to a third AC current threshold, the fifth compressor frequency control strategy is normal operation; when the third AC current threshold is less than or equal to a fourth AC current threshold, the fifth compressor frequency control strategy is to prohibit frequency increase; when the fourth AC current threshold is less than or equal to a fifth AC current threshold, the fifth compressor frequency control strategy is to slowly decrease the frequency; and when the AC current is greater than or equal to a fifth AC current threshold, the fifth compressor frequency control strategy is to immediately stop.

9. The compressor frequency control method for a variable frequency dehumidifier as described in claim 1, characterized in that, The compressor current control strategy includes: when the compressor current is less than or equal to the first compressor current threshold, the sixth compressor frequency control strategy is normal operation; when the first compressor current threshold is less than or equal to the second compressor current threshold, the sixth compressor frequency control strategy is slow frequency increase; when the second compressor current threshold is less than or equal to the third compressor current threshold, the sixth compressor frequency control strategy is normal operation; when the third compressor current threshold is less than or equal to the fourth compressor current threshold, the sixth compressor frequency control strategy is frequency prohibition; when the fourth compressor current threshold is less than or equal to the fifth compressor current threshold, the sixth compressor frequency control strategy is rapid frequency reduction; and when the compressor current is greater than or equal to the fifth compressor current threshold, the sixth compressor frequency control strategy is immediate shutdown.

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