Circuit and control method of photovoltaic direct-drive compressor

Abstract

This application relates to a circuit and control method for a photovoltaic direct-drive compressor. The method includes: sampling the current DC bus voltage and the previous DC bus voltage to determine the bus voltage change rate; if the bus voltage change rate is greater than a preset threshold and the current DC bus voltage is lower than a preset low-voltage threshold, then the circuit of the photovoltaic direct-drive compressor is determined to be in a dynamic change condition; otherwise, the circuit of the photovoltaic direct-drive compressor is determined to be in a stable condition; under the stable condition, the current maximum photovoltaic power generation capacity of the photovoltaic Boost circuit is compared with the load demand, and a corresponding power supply strategy is determined based on the comparison result, and the duty cycle of the photovoltaic Boost circuit is adjusted based on the bus voltage deviation combined with the voltage outer loop and the current inner loop; under the dynamic change condition, the bus voltage drop is compensated by the bus capacitor current feedforward, and the limited PWM signal is output by hardware current limiting cycle by cycle.

Description

Technical Field

[0001] This application relates to the field of photovoltaic direct-drive compressor control, and more particularly to a circuit and control method for a photovoltaic direct-drive compressor. Background Technology

[0002] In the field of photovoltaic air conditioning, existing residential photovoltaic air conditioning systems typically employ an architecture of photovoltaic strings + full-bridge inverter + grid interaction. However, the full-bridge inverter solution requires a full-bridge inverter circuit composed of multiple power switching transistors (such as IGBTs or MOSFETs) on the AC side, along with complex drive control and protection circuits. While this solution can achieve bidirectional power flow control between photovoltaics and the grid, the large number of power devices required by the full-bridge inverter and the complexity of the drive circuitry result in higher system hardware costs. Furthermore, the increased number of components used also increases the risk of failure. Summary of the Invention

[0003] This application provides a circuit and control method for a photovoltaic direct-drive compressor to solve the problem that the use of full-bridge inverters in existing household photovoltaic air conditioning systems leads to high failure risks and hardware costs due to the large number of power devices and complex drive circuits.

[0004] In a first aspect, this application provides a circuit for a photovoltaic direct-drive compressor, including: a photovoltaic boost circuit, an AC uncontrolled rectifier circuit, a bus capacitor, and a ripple compensation capacitor; The photovoltaic Boost circuit consists of at least one photovoltaic input branch. Each photovoltaic input branch includes an inductor, a switching transistor, and a diode. One end of the inductor is connected to the positive terminal of the photovoltaic input, and the other end of the inductor is connected to the first terminal of the switching transistor and the anode of the diode. The second terminal of the switching transistor is connected to the negative terminal of the photovoltaic input. The cathode of the diode is the output terminal of the photovoltaic input branch. The output terminals of each photovoltaic input branch are connected in parallel and then converge to the positive terminal of the DC bus. The input terminals of each photovoltaic input branch are connected to the negative terminal of the DC bus. The AC input terminal of the uncontrolled AC rectifier circuit is connected to a single-phase AC power supply. The positive terminal of the DC output terminal of the uncontrolled AC rectifier circuit is connected to the positive terminal of the DC bus, and the negative terminal of the DC output terminal of the uncontrolled AC rectifier circuit is connected to the negative terminal of the DC bus. This is used to rectify the AC power and feed it into the DC bus, so as to supply power to the DC bus together with the photovoltaic Boost boost circuit. The positive terminal of the bus capacitor is connected to the positive terminal of the DC bus, and the negative terminal of the bus capacitor is connected to the negative terminal of the DC bus, and is connected in parallel between the positive and negative terminals of the DC bus. The positive terminal of the ripple compensation capacitor is connected to the positive terminal of the DC bus, and the negative terminal of the ripple compensation capacitor is connected to the negative terminal of the DC bus, and is connected in parallel between the positive and negative terminals of the DC bus.

[0005] Optionally, the circuit further includes a pre-charge protection circuit, which consists of a pre-charge resistor and a contactor connected in series and then in parallel between the positive and negative terminals of the DC bus, to suppress the inrush current at the moment the system is powered on.

[0006] Secondly, this application provides a control method based on the photovoltaic direct-drive single-phase compressor circuit described in the first aspect, the method comprising: Sample the DC bus voltage at the current moment and the DC bus voltage at the previous moment to determine the rate of change of the bus voltage; If the rate of change of the bus voltage is greater than a preset threshold and the current DC bus voltage is lower than a preset low voltage threshold, then the circuit of the photovoltaic direct-drive compressor is determined to be in a dynamic change condition; otherwise, the circuit of the photovoltaic direct-drive compressor is determined to be in a stable condition. Under the stable operating conditions, the current maximum photovoltaic power generation capacity of the photovoltaic Boost circuit is compared with the load demand, and a corresponding power supply strategy is determined based on the comparison result. The duty cycle of the photovoltaic Boost circuit is adjusted using a dual-loop control system combining the bus voltage deviation with the voltage outer loop and current inner loop. The power supply strategy refers to the strategy used to meet the current load demand; the bus voltage deviation refers to the difference between the actual sampled value of the DC bus voltage and the preset target reference value. Under the dynamic change condition, the bus voltage drop is compensated by the bus capacitor current feedforward, and the limited PWM signal is output by hardware current limiting on a cycle-by-cycle basis.

[0007] Optionally, the current maximum photovoltaic power generation capacity of the photovoltaic Boost circuit is compared with the load demand, including: determining the power-voltage slope sign based on the difference in photovoltaic power and voltage between the current and previous moments, wherein the slope sign represents the direction of the current operating point relative to the maximum power point; when the slope is positive, the duty cycle needs to be increased to increase the photovoltaic voltage, and when the slope is negative, the duty cycle needs to be decreased to decrease the photovoltaic voltage; determining an adaptive factor based on the bus voltage deviation, wherein the adaptive factor takes a first value when the bus voltage deviation is greater than a preset threshold, and takes a second value when the bus voltage deviation is less than or equal to the preset threshold, wherein the first value is greater than the second value; multiplying the determined adaptive factor by the slope sign and then by the base step size as the duty cycle adjustment amount of the photovoltaic Boost circuit at the current moment, and determining the photovoltaic operating point voltage after updating the duty cycle as the current maximum photovoltaic power generation capacity; and comparing the current maximum photovoltaic power generation capacity of the photovoltaic Boost circuit with the load demand based on the determined maximum photovoltaic power generation capacity.

[0008] Optionally, adjusting the duty cycle of the photovoltaic boost circuit based on the bus voltage deviation using a dual-loop control system combining an outer voltage loop and an inner current loop includes: in the outer voltage loop, generating a reference current based on the bus voltage deviation using proportional-integral control, wherein the reference current represents the target current drawn from the photovoltaic side required to eliminate the bus voltage deviation; in the inner current loop, using the smaller of the actual photovoltaic output power and the load demand power as the target power, and dividing the target power by the photovoltaic voltage to obtain an inductor current reference value; comparing the difference between the inductor current reference value and the actual inductor current sample value with a preset hysteresis width, and outputting a PWM signal based on the comparison result, wherein the duty cycle of the PWM signal is the duty cycle currently being adjusted by the photovoltaic boost circuit.

[0009] Optionally, a corresponding power supply strategy is determined based on the comparison results, including: when the maximum photovoltaic power generation capacity exceeds the load demand, a first power supply strategy is implemented, wherein the first power supply strategy refers to limiting the actual output power of the photovoltaic Boost circuit to the load demand level; when the maximum photovoltaic power generation capacity is insufficient for the load demand, a second power supply strategy is implemented, wherein the second power supply strategy refers to automatically forward biasing and conducting the diodes in the AC uncontrolled rectifier circuit when the bus voltage drops below the output voltage of the AC uncontrolled rectifier circuit, and grid energy is injected into the bus through the AC uncontrolled rectifier circuit to make up the difference.

[0010] Optionally, responding to bus voltage dips by feeding forward compensation of bus capacitance current includes: calculating a feedforward compensation current based on the bus capacitance value, the bus voltage difference between the current and previous times, and the sampling period, wherein the feedforward compensation current is equal to the product of the bus capacitance value and the rate of change of the bus voltage, and the feedforward compensation current is used to characterize the supplementary current required to suppress sudden changes in bus voltage; and superimposing the feedforward compensation current into the current loop reference command, so that the feedforward compensation amount enters the inner current loop to participate in regulation during the first sampling period when the bus voltage changes.

[0011] Optionally, the PWM signal is output through hardware current limiting on a cycle-by-cycle basis, including: truncating the current based on the maximum peak current allowed by the switching transistor and inductor as the limiting value according to the current loop reference command; mapping the limited current value to a voltage threshold according to the sampled reference voltage, and comparing the actual inductor voltage with the voltage threshold cycle-by-cycle; outputting a high-level PWM signal when the inductor voltage is less than the voltage threshold; and outputting a low-level PWM signal when the inductor voltage is greater than or equal to the voltage threshold.

[0012] Optionally, the method further includes: extracting the ripple component in the DC bus voltage for active compensation, and controlling the voltage of the ripple compensation capacitor to synthesize a control signal to drive the compensation capacitor to absorb or release pulsating energy.

[0013] Optionally, extracting the ripple component from the DC bus voltage for active compensation and controlling the ripple compensation capacitor voltage to synthesize a control signal to drive the compensation capacitor to absorb or release pulsating energy includes: sampling the DC bus voltage, subtracting the DC component obtained by low-pass filtering from the DC bus voltage to extract the ripple component, and subtracting the ripple component from zero and sending it to a proportional resonant controller to generate a first reference current for offsetting the ripple; sampling the ripple compensation capacitor voltage and generating a second reference current with a preset reference value as the target through a proportional-integral controller, wherein the second reference current is used to maintain the DC bias voltage of the ripple compensation capacitor at a set value; subtracting the actual inductor current from the sum of the first reference current and the second reference current, and outputting a PWM drive signal through the proportional controller, wherein the PWM drive signal controls the switching transistor to turn on and off, so that the charging and discharging current flowing through the ripple compensation capacitor tracks the sum of the first reference current and the second reference current, so that the ripple compensation capacitor absorbs or releases pulsating energy.

[0014] Compared with the prior art, the above-mentioned technical solution provided in this application has the following advantages: The method provided in this application sample the DC bus voltage at the current moment and the DC bus voltage at the previous moment to determine the bus voltage change rate. If the bus voltage change rate is greater than a preset threshold and the current DC bus voltage is lower than a preset low voltage threshold, it is determined that the photovoltaic direct-drive compressor circuit is in a dynamic change condition; otherwise, it is determined that the photovoltaic direct-drive compressor circuit is in a stable condition. Under the stable condition, the current maximum photovoltaic power generation capacity of the photovoltaic Boost boost circuit is compared with the load demand, and the corresponding power supply strategy is determined according to the comparison result. The duty cycle of the photovoltaic Boost boost circuit is adjusted based on the bus voltage deviation combined with the voltage outer loop and the current inner loop. Under the dynamic change condition, the bus voltage drop is compensated by the bus capacitor current feedforward, and the limited PWM signal is output by hardware current limiting on a cycle-by-cycle basis. As can be seen, this application achieves maximum utilization of photovoltaic energy and precise control of the bus voltage under stable operating conditions by comparing the maximum photovoltaic power generation capacity with the load demand → determining the power supply strategy → and adjusting the duty cycle through a dual-loop control logic chain. Under dynamic and sudden operating conditions, a combination strategy of feedforward compensation and cycle-by-cycle hardware current limiting is used to achieve rapid replenishment of power gaps and hardware safety protection. The control strategies for both operating conditions work together to ensure stable and safe operation of the system across the entire operating range. In addition, the entire circuit uses only an uncontrolled rectification configuration to achieve direct photovoltaic drive, which requires fewer components and is therefore less expensive than existing single-phase topologies that remove the full-bridge structure on the AC side. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0016] 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, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0018] Figure 1 A circuit diagram of a photovoltaic direct-drive compressor provided in an embodiment of this application; Figure 2 A flowchart illustrating a control method for a photovoltaic direct-drive compressor circuit provided in an embodiment of this application; Figure 3 A block diagram of sub-mode dynamic power decoupling provided in an embodiment of this application; Figure 4 An optional flowchart of a control method for a photovoltaic direct-drive compressor circuit provided in an embodiment of this application; Figure 5 This is a schematic diagram of the ripple suppression control loop provided in an embodiment of this application; Figure 6 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of the invention. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0021] To address the issues of high failure risk and hardware cost in existing residential photovoltaic air conditioning systems using full-bridge inverters due to the large number of power devices and complex drive circuits, this application provides a circuit for a photovoltaic direct-drive compressor, such as... Figure 1 As shown, the circuit includes: a photovoltaic boost circuit 11, an AC uncontrolled rectifier circuit 12, a bus capacitor 13, and a ripple compensation capacitor 14. The photovoltaic Boost circuit 11 consists of at least one photovoltaic input branch. Each photovoltaic input branch includes an inductor, a switching transistor, and a diode. One end of the inductor is connected to the positive terminal of the photovoltaic input, and the other end of the inductor is connected to the first terminal of the switching transistor and the anode of the diode. The second terminal of the switching transistor is connected to the negative terminal of the photovoltaic input. The cathode of the diode is the output terminal of the photovoltaic input branch. The output terminals of each photovoltaic input branch are connected in parallel and then converge to the positive terminal of the DC bus. The input terminals of each photovoltaic input branch are connected to the negative terminal of the DC bus. Specifically, in Figure 1 In the circuit, the Boost converter consists of two photovoltaic modules connected in parallel, which can significantly increase the photovoltaic power output. ,inductance Boost diode Boost diode Switching transistor , Together they form a boost circuit structure, For rectifier bridge module, This is the ripple compensation capacitor (dashed box). For bus capacitors, , The system includes a pre-charge resistor and a contactor. The pre-charge resistor effectively prevents the inrush current generated when the contactor engages. In addition, the air conditioner draws power from the busbar and can be powered by both photovoltaic and AC power simultaneously.

[0022] In an optional embodiment of this application, the photovoltaic boost circuit 11 is composed of two photovoltaic input branches connected in parallel. Based on this, the basic working process of the boost circuit in this application embodiment is as follows: Energy storage stage (switch on): When the PWM signal output by the main control chip is high, the switch... (or (The circuit is on.) At this time, the photovoltaic input voltage... All applied to the inductor (or In the diode, the inductor stores electrical energy as magnetic field energy, and the inductor current increases linearly. During this stage, the diode... (or The bus is cut off due to reverse bias, and the bus is controlled by the bus capacitor. The stored energy supplies power to the load.

[0023] Boost phase (switch off): When the PWM signal is low, the switch... (or (Switch off). Since the inductor current cannot change abruptly, the polarity of the voltage across the inductor reverses, and the magnetic field energy stored in the inductor is converted into electrical energy and released. At this time, the photovoltaic input voltage and the inductor voltage are superimposed, and the voltage is released through the diode. (or Output to the DC bus, serving as the bus capacitor. It charges and supplies power to the load. The combined output voltage is higher than the photovoltaic input voltage, thus achieving a boost function.

[0024] Output voltage regulation: By adjusting the duty cycle of the PWM signal (i.e., the ratio of the switching time of the switching transistor to the switching cycle), the ratio of energy storage and release time of the inductor can be controlled, thereby regulating the DC bus voltage. A higher duty cycle results in a higher output voltage. Theoretically, the output voltage... ,in This refers to the duty cycle.

[0025] As can be seen, the AC uncontrolled rectifier circuit 12 in this embodiment is a single-phase diode rectifier bridge; each of the two paths carries a portion of the current, and the total output power is the sum of the two paths, which can greatly improve the photovoltaic power input capability; when one path fails, the other path can continue to work (derating operation), which improves the system reliability; the two paths can be connected to photovoltaic strings facing different directions, which improves the system's adaptability to different lighting conditions.

[0026] The AC input terminal of the AC uncontrolled rectifier circuit 12 is connected to a single-phase AC power supply. The positive terminal of the DC output terminal of the AC uncontrolled rectifier circuit is connected to the positive terminal of the DC bus, and the negative terminal of the DC output terminal of the AC uncontrolled rectifier circuit is connected to the negative terminal of the DC bus. This is used to rectify the AC power and feed it into the DC bus, which together with the photovoltaic Boost boost circuit provides power to the DC bus. Based on this, the single-phase bridge uncontrolled rectifier circuit consists of four rectifier diodes connected in a bridge configuration: the cathodes of the first diode (D1) and the third diode (D3) are connected together as the positive DC output, and the anodes of the second diode (D2) and the fourth diode (D4) are connected together as the negative DC output. One end of the AC power supply is connected to the junction of the anode of D1 and the cathode of D2, and the other end of the AC power supply is connected to the junction of the anode of D3 and the cathode of D4. When the AC power supply is in the positive half-cycle, D1 and D4 conduct, and D2 and D3 are cut off; when the AC power supply is in the negative half-cycle, D2 and D3 conduct, and D1 and D4 are cut off, thus achieving full-wave rectification.

[0027] The positive terminal of bus capacitor 14 is connected to the positive terminal of the DC bus, and the negative terminal of the bus capacitor is connected to the negative terminal of the DC bus, and is connected in parallel between the positive and negative terminals of the DC bus. Among them, bus capacitor Connected in parallel across the DC bus, its fundamental characteristic is that the voltage cannot change abruptly. When the power input to the photovoltaic boost circuit and the AC uncontrolled rectifier circuit is greater than the power consumed by the load, the excess energy charges the bus capacitor, causing the bus voltage to rise; when the input power is less than the power consumed by the load, the bus capacitor discharges to release energy, causing the bus voltage to drop. Therefore, the bus capacitor has the following functions: 1) Energy storage buffer, acting as a power reservoir for the system, smoothing out instantaneous power fluctuations from the photovoltaic and AC inputs; 2) Stabilizing the bus voltage, providing energy support during load changes and preventing drastic voltage fluctuations; 3) Power supply guarantee, discharging first to provide inrush current in scenarios with instantaneous high current demands such as compressor startup.

[0028] The positive terminal of the ripple compensation capacitor 14 is connected to the positive terminal of the DC bus, and the negative terminal of the ripple compensation capacitor is connected to the negative terminal of the DC bus, and is connected in parallel between the positive and negative terminals of the DC bus.

[0029] Among them, ripple compensation capacitor While also connected in parallel across the DC bus, the ripple compensation capacitor functions differently from the bus capacitor. The bus capacitor is a passive energy storage element, its voltage naturally determined by the system's power balance; whereas the ripple compensation capacitor is an actively controlled element, its flow actively controlled by the main control chip via a PWM signal. The current is directed to the rectifier circuit, causing it to absorb or release energy according to a specific pattern. The main function of the ripple compensation capacitor is active filtering, specifically absorbing the power frequency ripple energy (mainly 100Hz and its harmonics) generated by the uncontrolled rectifier circuit. For example... Figure 5 As described in the related description, the control loop provides high gain at the 2nd to 12th ripple frequencies through a proportional resonant (PR) controller, generates compensation current commands, and drives the ripple compensation capacitor to actively absorb or release pulsating energy, thereby smoothing the DC bus voltage waveform.

[0030] By using ripple compensation capacitors in conjunction with an active control loop to suppress ripple, compared to the traditional approach of simply increasing the bus capacitor capacity, there is no need to significantly increase the capacity and volume of the bus capacitor, thus reducing material costs and space occupation. In addition, the active control method is more precise and efficient in suppressing ripple at specific frequencies. Moreover, it avoids the lifespan and reliability issues caused by relying solely on large-capacity electrolytic capacitors.

[0031] Furthermore, such as Figure 1 As shown, the circuit in this embodiment of the application also includes a pre-charge protection circuit, which consists of a pre-charge resistor and a contactor connected in series and then connected in parallel between the positive and negative terminals of the DC bus, and is used to suppress the inrush current at the moment the system is powered on.

[0032] It should be noted that at the moment of power-on, the bus capacitor... The voltage across the terminals is zero, equivalent to a short circuit. If the main contactor is closed directly to connect the power supply to the DC bus, the instantaneous inrush current can reach hundreds of amperes, enough to burn out the rectifier diodes, damage the bus capacitors, and potentially cause arcing damage to the contactor contacts. Based on this, the pre-charge protection circuit operates as follows: 1) Pre-charging phase: When the system is powered on, the contactor in the pre-charging branch is closed first. At this time, the current flows through the pre-charging resistor. After current limiting, the bus capacitor is slowly charged. Pre-charge resistor. The resistance is designed to limit the charging current within a safe range.

[0033] 2) Normal operating phase: When the voltage across the bus capacitor is charged to near its rated value (e.g., close to the AC rectified output voltage or photovoltaic boost output voltage), the main contactor engages, bypassing the pre-charging resistor. At this time, the system enters normal operating mode, and the current supplies power to the bus directly through the main contactor, no longer passing through the pre-charging resistor.

[0034] 3) Pre-charge circuit disconnection: After the main contactor engages, the contactor in the pre-charge branch... Disconnect, pre-charge resistor To separate it from the main circuit and avoid unnecessary losses during normal operation.

[0035] In combination with the above Figure 1 The circuit shown in this application embodiment also provides a photovoltaic direct-drive single-phase compressor control method. The steps of this method can be executed by a main control chip. The main control chip is used to collect various parameters from the photovoltaic direct-drive single-phase compressor circuit and perform control based on the collected parameters, specifically as follows: Figure 2 As shown, the method includes the following steps: Step 201: Sample the DC bus voltage at the current moment and the DC bus voltage at the previous moment to determine the rate of change of the bus voltage; In response, the main control chip uses a fixed sampling period. (e.g., 0.1ms) Real-time acquisition of DC bus voltage Let the bus voltage at the current moment (the k-th sampling) be... The bus voltage at the previous time step (the (k-1)th sampling step) was: The estimated value of the bus voltage change rate Calculate using the following formula:

[0036] The rate of change of bus voltage reflects the drastic change in DC bus voltage per unit time. When there is a severe imbalance between photovoltaic input power and load power consumption (such as at the moment of compressor startup), the bus voltage will drop rapidly, and the rate of change will increase significantly. Therefore, the rate of change of bus voltage is a direct physical quantity characterizing the power supply and demand balance of the system.

[0037] Step 202: If the rate of change of the bus voltage is greater than a preset threshold and the current DC bus voltage is lower than a preset low voltage threshold, then the circuit of the photovoltaic direct-drive compressor is determined to be in a dynamic change condition; otherwise, the circuit of the photovoltaic direct-drive compressor is determined to be in a stable condition. It can be seen that if the bus voltage change rate is greater than the preset threshold... And the current DC bus voltage is lower than the preset low voltage threshold. If the condition is abnormal, it is determined to be a dynamic change condition; otherwise, it is determined to be a stable condition.

[0038] Among them, the preset threshold This refers to the maximum permissible instantaneous rate of change of the DC bus, used to characterize whether the system power is in a state of drastic fluctuation. For a single-phase 220V photovoltaic air conditioning system, Typically, the voltage / ms is set to 50~100V. Preset low-voltage threshold. This refers to the minimum voltage required for safe operation of the busbar. Below this value, the system faces the risk of undervoltage shutdown, typically set at 300V. Two conditions must be met simultaneously: firstly, to ensure rapid detection of dynamic impact events (rate of change condition), and secondly, to prevent false triggering due to high-frequency interference (low voltage condition), thus improving the reliability of the judgment.

[0039] Stable operating condition: Bus voltage change rate is gradual (≤ ), or the bus voltage is still within a safe range (≥ At this point, the system's power supply and demand are basically balanced, or although there are slight fluctuations, they are insufficient to threaten system safety. Under this condition, the control strategy focuses on photovoltaic maximum power point tracking and precise regulation of the bus voltage, pursuing both economic efficiency and stability in system operation.

[0040] Dynamic sudden change condition: The rate of change of bus voltage increases sharply (> And the bus voltage has fallen below the safety threshold (< At this point, the system faces an emergency state of severe power imbalance, such as during compressor startup or a sudden drop in sunlight. Under these conditions, the control strategy focuses on rapid power replenishment and overcurrent protection, with the primary goal of preventing the system from shutting down due to undervoltage.

[0041] Step 203: Under stable operating conditions, compare the current maximum photovoltaic power generation capacity of the photovoltaic Boost circuit with the load demand, determine the corresponding power supply strategy based on the comparison result, and adjust the duty cycle of the photovoltaic Boost circuit based on the bus voltage deviation combined with the voltage outer loop and current inner loop dual-loop control; where the power supply strategy refers to the strategy used to meet the current load demand; the bus voltage deviation refers to the difference between the actual sampled value of the DC bus voltage and the preset target reference value; Under stable operating conditions, the main control chip first obtains the current maximum photovoltaic power generation capacity of the photovoltaic Boost circuit through an adaptive MPPT algorithm (see the subsequent description of obtaining the maximum photovoltaic power generation capacity for details). Then, it compares this maximum power generation capacity with the current load demand (i.e., the power required for the air conditioner compressor to operate), and the comparison result determines the system's power supply strategy.

[0042] The comparison results may result in the following two situations: Scenario 1: The maximum power generation capacity of the photovoltaic system exceeds the load demand.

[0043] At this point, the electrical energy generated by the photovoltaic system exceeds the load's consumption capacity. If the photovoltaic system is allowed to generate electricity at full power, the excess energy will have nowhere to go and will accumulate on the bus capacitor, causing the DC bus voltage to rise continuously, potentially exceeding the withstand voltage of the power devices and causing equipment damage.

[0044] Therefore, as described above, the corresponding power supply strategy is determined based on the comparison results. In this case, the control strategy is to actively limit the actual output power of the photovoltaic boost circuit to the level of load demand. This limitation is achieved through the active adjustment of the duty cycle by the adaptive MPPT module. That is, when an upward trend in the bus voltage is detected, the system actively reduces the duty cycle, causing the photovoltaic operating point to deviate from the maximum power point, thereby reducing the actual output power of the photovoltaic and keeping the power generation and consumption in balance.

[0045] Scenario 2: The maximum power generation capacity of the photovoltaic system is insufficient to meet the load demand.

[0046] At this point, the maximum electrical energy generated by the photovoltaic system is insufficient to meet the load's consumption demands. Under these circumstances, the DC bus capacitor continues to release energy, and the bus voltage begins to drop. When the bus voltage drops below the output voltage of the AC uncontrolled rectifier circuit (approximately 311V), the rectifier diodes in the AC uncontrolled rectifier circuit automatically switch from reverse cutoff to forward bias conduction, and grid energy is naturally injected into the DC bus through the rectifier bridge, filling the gap between the photovoltaic power and the load demand.

[0047] It is worth noting that this energy replenishment process is entirely determined by the physical characteristics of the diodes, without requiring any control commands from the main control chip. The response speed is on the nanosecond level, realizing seamless collaborative power supply between photovoltaics and the grid.

[0048] It is evident that by comparing the maximum photovoltaic power generation capacity with the load demand and determining the power supply strategy based on the comparison results, the following can be achieved: 1) When photovoltaic power is sufficient, proactive power limiting can be implemented to prevent overvoltage damage to equipment on the busbar; 2) When photovoltaic power is insufficient, the grid can be automatically introduced to supplement power through hardware, ensuring uninterrupted power supply to the load. Throughout the process, photovoltaic power generation is maximized, with the grid serving only as a supplement, realizing an economical operation mode of prioritizing photovoltaic power and self-consumption.

[0049] Furthermore, whether there is excess photovoltaic power requiring power limiting or insufficient photovoltaic power requiring grid supplementation, the system needs to adjust the duty cycle of the Boost circuit to change the actual output power of the photovoltaic system, thereby stabilizing the bus voltage at the target reference value (e.g., 400V). This task is accomplished by dual-loop control of the voltage outer loop and the current inner loop. As mentioned above, the bus voltage deviation refers to the actual sampled value of the DC bus voltage. Compared with the preset target reference value The difference between the actual voltage (usually 400V) and the target voltage is used. This deviation directly reflects the balance between the current photovoltaic input power and the load power consumption: a positive deviation (actual voltage higher than the target value) indicates excess power; a negative deviation (actual voltage lower than the target value) indicates insufficient power. The voltage outer loop and the current inner loop adopt a cascaded structure. For details on the implementation method, please refer to the subsequent description of dual-loop control.

[0050] In other words, under stable operating conditions, the relationship between the determination of the power supply strategy and the adjustment of the duty cycle by the dual-loop control is as follows: the power supply strategy, at the macro level, determines whether the photovoltaic system generates more or less power, or whether the grid participates in supplementary energy generation; the dual-loop control, at the micro execution level, precisely outputs the corresponding PWM duty cycle through PI regulation and hysteresis comparison, translating the power supply strategy into the on and off actions of the switching transistors, ultimately stabilizing the bus voltage at the target reference value. Together, they achieve a coordinated and unified approach to maximizing the utilization of photovoltaic energy and precisely controlling the bus voltage under stable operating conditions.

[0051] Step 204: Under dynamic change conditions, the bus voltage drop is compensated by the bus capacitor current feedforward, and the limited PWM signal is output by hardware current limiting on a cycle-by-cycle basis.

[0052] In this scenario, the bus voltage drops extremely rapidly (e.g., tens of volts within 0.1 ms), requiring the bus capacitor to release a large current to fill the power gap. If the PI control method used under stable operating conditions is employed, the response speed is slow because the PI controller relies on error accumulation to generate the adjustment. The bus voltage may drop below the undervoltage protection threshold before the PI controller has fully responded, leading to system shutdown. Therefore, the first measure under dynamic abrupt changes is bus capacitor current feedforward compensation. The core idea is to directly calculate the required current to suppress the bus voltage drop based on the capacitor's physical characteristics and the currently detected rate of change of bus voltage, and immediately add this compensation to the current loop command. Since feedforward compensation can intervene in control within the first sampling period of a bus voltage change (without waiting for error accumulation), it can respond several sampling periods earlier than existing PI control, effectively suppressing further bus voltage drops.

[0053] Under dynamic and sudden operating conditions, the system attempts to draw as much current as possible to quickly replenish power. However, due to the physical limits of hardware such as switches and inductors (e.g., a maximum allowable peak current of 20A), excessive current will damage the devices. Therefore, the second measure under dynamic and sudden operating conditions is cycle-by-cycle hardware current limiting, which includes two stages: amplitude limiting and cycle-by-cycle comparison. After the feedforward compensation is added to the current command, the system first truncates the command with the maximum peak current allowed by the hardware (amplification processing) to ensure that the command current does not exceed the hardware safety limit. Then, the amplitude-limited current command is mapped to a voltage threshold. In each PWM cycle, the actual inductor voltage (proportional to the instantaneous inductor current) is compared with this voltage threshold. Once the inductor voltage reaches or exceeds the threshold, the hardware comparator immediately forces the switch to turn off (for details on the specific implementation, please refer to the subsequent description of cycle-by-cycle hardware current limiting).

[0054] Therefore, the relationship between feedforward compensation and cycle-by-cycle hardware current limiting is as follows: feedforward compensation is responsible for speed, that is, generating a compensation current command within the first sampling cycle to respond to bus dips as quickly as possible; cycle-by-cycle hardware current limiting is responsible for protection, that is, monitoring the actual current in each PWM cycle and immediately shutting down once the safety boundary is reached to ensure hardware safety. The two complement each other, jointly achieving the dual goals of rapid energy replenishment and safe overcurrent control under dynamic and sudden operating conditions.

[0055] Through steps 201 to 204 above, the DC bus voltage at the current moment and the DC bus voltage at the previous moment are sampled to determine the bus voltage change rate. If the bus voltage change rate is greater than a preset threshold and the current DC bus voltage is lower than a preset low voltage threshold, the photovoltaic direct-drive compressor circuit is determined to be in a dynamic change condition; otherwise, the photovoltaic direct-drive compressor circuit is determined to be in a stable condition. Under the stable condition, the current maximum photovoltaic power generation capacity of the photovoltaic Boost boost circuit is compared with the load demand, and the corresponding power supply strategy is determined according to the comparison result. The duty cycle of the photovoltaic Boost boost circuit is adjusted based on the bus voltage deviation combined with the voltage outer loop and the current inner loop. Under the dynamic change condition, the bus voltage drop is compensated by the bus capacitor current feedforward, and the limited PWM signal is output through cycle-by-cycle hardware current limiting. As can be seen, this application achieves maximum utilization of photovoltaic energy and precise control of the bus voltage under stable operating conditions by comparing the maximum photovoltaic power generation capacity with the load demand → determining the power supply strategy → and adjusting the duty cycle through a dual-loop control logic chain. Under dynamic and sudden operating conditions, a combination strategy of feedforward compensation and cycle-by-cycle hardware current limiting is used to achieve rapid replenishment of power gaps and hardware safety protection. The control strategies for both operating conditions work together to ensure stable and safe operation of the system across the entire operating range. In addition, the entire circuit uses only an uncontrolled rectification configuration to achieve direct photovoltaic drive, which requires fewer components and is therefore less expensive than existing single-phase topologies that remove the full-bridge structure on the AC side.

[0056] In an optional embodiment of this application, the method of comparing the current maximum photovoltaic power generation capacity of the photovoltaic Boost circuit with the load demand in step 203 above may further include: Step 11: Determine the power-voltage slope sign based on the difference in photovoltaic power and the difference in photovoltaic voltage between the current time and the previous time. The slope sign represents the direction of the current operating point relative to the maximum power point. When the slope is positive, the duty cycle needs to be increased to increase the photovoltaic voltage. When the slope is negative, the duty cycle needs to be decreased to decrease the photovoltaic voltage. Wherein, the photovoltaic power at the current moment (the kth sampling time) From the photovoltaic voltage at the current moment With photovoltaic current Multiplying them together, we get:

[0057] Photovoltaic power at the previous time step (k-1th sampling) Similarly, the photovoltaic power difference can be calculated based on this. and photovoltaic voltage difference :

[0058] Further calculation of the power-voltage slope:

[0059] This slope reflects whether the photovoltaic operating point is currently on the left or right side of the maximum power point curve; when the slope is positive ( When the slope is negative ( ): This indicates that the current operating point is to the left of the maximum power point. In this region, the photovoltaic power increases as the photovoltaic voltage increases. Therefore, to move closer to the maximum power point, the duty cycle needs to be increased to boost the photovoltaic input voltage. When the slope is 0, it indicates that the current operating point is to the right of the maximum power point. In this region, the photovoltaic power decreases as the photovoltaic voltage increases. Therefore, to move closer to the maximum power point, the duty cycle needs to be reduced to lower the photovoltaic input voltage. The sign function of the above slope is then applied. The result is either +1 or -1, indicating the direction of duty cycle adjustment. +1 indicates that the duty cycle needs to be increased, and -1 indicates that the duty cycle needs to be decreased.

[0060] Step 12: Determine the adaptive factor based on the bus voltage deviation. When the bus voltage deviation is greater than a preset threshold, the adaptive factor takes a first value. When the bus voltage deviation is less than or equal to the preset threshold, the adaptive factor takes a second value. The first value is greater than the second value. Bus voltage deviation Defined as the actual sampled value of the DC bus voltage at the current moment. Compared with the preset target reference value Difference:

[0061] This deviation reflects the degree to which the current bus voltage deviates from the target value: a positive deviation indicates that the bus voltage is too high and the power is excessive; a negative deviation indicates that the bus voltage is too low and the power is insufficient.

[0062] Adaptive factor The value is determined based on the absolute value of the bus voltage deviation and a preset threshold. The comparison result (usually 5~10V) is used to determine: when When the bus voltage deviates significantly from the target value, the system is in a relatively unstable state. In this case, the adaptive factor takes its first value (i.e., the larger value). This allows the MPPT to track power changes with large steps, responding quickly to power variations and helping the bus voltage to stabilize as soon as possible.

[0063] when When the bus voltage is close to the target value, the system is in a relatively stable state. At this time, the adaptive factor takes the second value (i.e., the smaller value). This allows MPPT to perform fine optimization with small step sizes, avoiding unnecessary fluctuations in the already stable bus voltage caused by large step size disturbances.

[0064] The adaptive factor ranges from -1 to 1 (usually a positive value), and its specific value is determined through system integration testing to ensure that the system has excellent dynamic response and steady-state performance under different operating conditions.

[0065] Step 13: Multiply the determined adaptive factor by the slope sign and then by the base step size to obtain the duty cycle adjustment amount of the photovoltaic Boost circuit at the current moment, and determine the photovoltaic operating point voltage after updating the duty cycle as the current maximum photovoltaic power generation capacity. The duty cycle update formula is as follows:

[0066] in, Find the optimal duty cycle for the MPPT updated at the current moment; To optimize the duty cycle for the MPPT of the previous time step; This is an adaptive factor that determines the step size; The sign of the power-voltage slope determines the direction of the step size (+1 or -1). The base step size is the smallest unit for each adjustment of the duty cycle, usually taken as 0.01.

[0067] It should be further explained that, It indicates the direction in which the duty cycle should be adjusted—whether to increase or decrease. This direction brings the photovoltaic operating point closer to the maximum power point and determines the magnitude of each adjustment step. A larger value is used when the bus voltage deviation is large, enabling rapid coarse adjustment; a smaller value is used when the bus voltage deviation is small, enabling fine-tuning. This is the smallest adjustment scale, ensuring the discreteness and controllability of the adjustment.

[0068] Furthermore, determining the photovoltaic operating point voltage after updating the duty cycle as the current maximum photovoltaic power generation capacity does not mean that the operating point voltage and the maximum power generation capacity are physically equivalent. Rather, it means that during the MPPT optimization process, the operating point voltage is continuously adjusted to approach the maximum power point voltage, and the current maximum photovoltaic power generation capacity is obtained at that operating point. This maximum generating capacity is then compared with load demand to determine the system's power supply strategy.

[0069] Step 14: Based on the determined maximum photovoltaic power generation capacity, compare the current maximum photovoltaic power generation capacity of the photovoltaic Boost circuit with the load demand.

[0070] Existing fixed-step MPPT algorithms face a dilemma: large step sizes offer fast tracking speeds but result in significant steady-state disturbances, leading to bus voltage fluctuations; small step sizes offer high steady-state accuracy but slow tracking speeds, causing lag in response to sudden changes in illumination. This application introduces an adaptive factor, allowing the MPPT step size to dynamically change with the bus voltage deviation. Specifically, large steps are used for rapid tracking when the deviation is large, while small steps are used for fine-tuning when the deviation is small, achieving a balance between fast response and precise optimization. Accurate determination of the power-voltage slope sign ensures that the duty cycle adjustment direction always points to the maximum power point, avoiding power loss due to incorrect direction. Combined with the adaptive step size, the system can quickly and accurately lock onto the maximum power point under various illumination conditions, maximizing the collection and utilization of photovoltaic energy.

[0071] In an optional embodiment of this application, the method of adjusting the duty cycle of the photovoltaic Boost circuit based on the bus voltage deviation combined with the voltage outer loop and the current inner loop in step 203 above may further include: Step 21: In the outer voltage loop, a reference current is generated based on the bus voltage deviation through proportional-integral control, wherein the reference current is characterized as the target current drawn from the photovoltaic side required to eliminate the bus voltage deviation. It should be noted that the outer voltage loop is responsible for calculating the required current command based on the bus voltage deviation, while the inner current loop is responsible for making the actual inductor current quickly follow the command. Together, they form a complete execution link of voltage target → current command → PWM duty cycle.

[0072] In the outer voltage loop, a reference current is generated based on the bus voltage deviation using proportional-integral (PI) control.

[0073] Bus voltage deviation Defined as the actual sampled value of the DC bus voltage at the current moment. Compared with the preset target reference value Difference:

[0074] This deviation directly reflects the current balance between power supply and demand in the system: when When the bus voltage is higher than the target value, it indicates that the input power is greater than the load consumption, and the current drawn from the photovoltaic side needs to be reduced. when When the bus voltage is lower than the target value, it indicates that the input power is less than the load consumption, and the current drawn from the photovoltaic side needs to be increased.

[0075] The voltage outer loop uses a proportional-integral (PI) controller to adjust the above deviation and generate a reference current. The calculation formula is as follows:

[0076] in, This is the proportional control coefficient, used to generate an immediate adjustment based on the current bus voltage deviation; that is, the greater the deviation, the greater the current command output by the proportional term. This represents the current bus voltage deviation. The integral control coefficient is used to eliminate the long-term steady-state error of the system and ensure that the bus voltage can eventually converge accurately to the target reference value. The sum of the photovoltaic input currents at the previous moment is used as the base value for the integral term.

[0077] It should be noted that, and The specific value needs to be determined through system integration testing based on system stability requirements, and the value is usually between 0 and 1.

[0078] Reference current This refers to the target current value that needs to be drawn from the photovoltaic side to eliminate the current bus voltage deviation and restore the bus voltage to the target reference value. This reference current is output to the inner current loop as a given command for the inner current loop.

[0079] Step 22: In the inner current loop, the smaller of the actual output power of the photovoltaic and the power demanded by the load is taken as the target power, and the target power is divided by the photovoltaic voltage to obtain the inductor current reference value. In the inner current loop, the smaller of the actual photovoltaic output power and the load demand power is taken as the target power.

[0080] Let the actual output power of the photovoltaic system at the current moment be... The load power requirement is (That is, the product of the current bus voltage and the reference current output from the outer voltage loop), then the target power for:

[0081] The smaller of the two values ​​is selected as the target power to prevent overcurrent: 1) If the actual output power of the photovoltaic system is less than the load demand power, the actual output power of the photovoltaic system is used as the target, and the photovoltaic system generates as much power as it can use, with the grid automatically supplementing the shortfall through the uncontrolled rectifier circuit; 2) If the actual output power of the photovoltaic system is greater than the load demand power, the load demand power is used as the target, and the actual output of the photovoltaic system is limited to avoid excess energy accumulation that could lead to an increase in bus voltage.

[0082] Target power Once determined, divide it by the photovoltaic voltage. The inductor current reference value can then be obtained. :

[0083] This inductor current reference value represents the current that the inductor of the Boost circuit should flow under the current photovoltaic voltage to achieve the target power. Since power divided by voltage equals current, this formula converts the power-level control target into a current-level control target, allowing the inner current loop to directly adjust the inductor current.

[0084] Step 23: Compare the difference between the inductor current reference value and the actual inductor current sample value with the preset hysteresis width, and output a PWM signal based on the comparison result. The duty cycle of the PWM signal is used to adjust the current actual duty cycle of the photovoltaic Boost circuit.

[0085] Actual inductor current sampling value Inductor current error is acquired in real time via a sampling unit. The difference between the reference value and the actual value:

[0086] Preset hysteresis width Typically, the hysteresis width is 0.1 to 0.2 times the peak current. For example, if the maximum allowed peak current is 20A, the hysteresis width can be 2 to 4A. The execution logic of the hysteresis comparator is as follows: like This indicates that the actual inductor current is lower than the reference value and the deviation exceeds the hysteresis half-width. At this time, the PWM output is high, the switching transistor is turned on, and the inductor current rises. like This indicates that the actual inductor current is higher than the reference value and the deviation exceeds the hysteresis half-width. At this time, the PWM output is low, the switching transistor is turned off, and the inductor current decreases. like This indicates that the deviation between the actual inductor current and the reference value is within the hysteresis width range, and the PWM state of the previous moment remains unchanged.

[0087] The output of the hysteresis comparator is the PWM signal, and its duty cycle is the actual duty cycle that the photovoltaic boost circuit is currently operating on, directly controlling the on and off time ratio of the switching transistor. Therefore, this application eliminates the need for complex PI parameter tuning, offers fast response, and limits the switching frequency within a certain range through the hysteresis width, avoiding excessively high switching frequencies near the reference value that would increase switching losses.

[0088] Therefore, in this application, through proportional-integral control in the voltage outer loop, the system can precisely adjust the bus voltage deviation. The proportional term provides a fast transient response, while the integral term eliminates steady-state error, ensuring that the bus voltage converges to the target reference value without deviation in steady state. The current inner loop uses hysteresis comparison control, which has an extremely fast response speed (microsecond level), requires no complex PI parameter tuning, and is insensitive to changes in system parameters, exhibiting good robustness. By taking the smaller value between the actual photovoltaic output power and the load demand power as the target power, the inner loop implements the constraint that the photovoltaic output must not exceed the load demand at the control algorithm level, fundamentally preventing the overcurrent risk caused by excessive voltage outer loop commands, and providing a basic guarantee for subsequent dynamic response and hardware safety.

[0089] In an optional embodiment of this application, the method of determining the corresponding power supply strategy based on the comparison result in step 203 above may further include: Step 31: When the maximum power generation capacity of the photovoltaic system exceeds the load demand, execute the first power supply strategy, wherein the first power supply strategy refers to limiting the actual output power of the photovoltaic Boost circuit to the load demand level. Step 32: When the maximum photovoltaic power generation capacity is insufficient to meet the load demand, a second power supply strategy is executed. The second power supply strategy refers to the automatic forward biasing and conduction of the diodes in the AC uncontrolled rectifier circuit when the bus voltage drops below the output voltage of the AC uncontrolled rectifier circuit. The grid energy is injected into the bus through the AC uncontrolled rectifier circuit to make up the difference.

[0090] It is evident that when the maximum power generation capacity of photovoltaic (PV) exceeds the load demand, allowing PV to generate power at its maximum output will result in excess energy. Since this invention employs an AC uncontrolled rectifier circuit, whose rectifier diodes are unidirectional, electrical energy cannot be reversed back to the grid through the uncontrolled rectifier circuit. Therefore, the excess energy has nowhere to go but accumulates on the DC bus capacitor, causing the bus voltage to continuously rise. When the bus voltage exceeds the withstand voltage of power devices (such as switching transistors and bus capacitors), it will cause device damage or even system collapse. Therefore, when the system detects that the bus voltage is higher than the target reference value and has a continuous upward trend, it indicates that PV power is excessive. The system then actively limits the actual output power of the PV Boost circuit to the load demand level. Specifically, the adaptive MPPT continuously adjusts the duty cycle to track the maximum power point and outputs the base duty cycle. When there is excess power, due to the high bus voltage, the reference current output by the PI controller in the aforementioned voltage outer loop will increase. The current inner loop then compares the actual output power of the photovoltaic system with the load demand power, and takes the smaller of the two as the target power. When the actual output power of the photovoltaic system exceeds the load demand, the target power is limited to the load demand. This limits the inductor current reference value. This ultimately reduces the PWM duty cycle, lowering the actual output power of the photovoltaic system to the level required by the load.

[0091] Furthermore, when the maximum power generation capacity of the photovoltaic system is less than the load demand, the photovoltaic system cannot independently meet the load's electricity needs. If the energy gap is not filled, the bus capacitor will continue to release energy, causing the bus voltage to drop continuously, eventually leading to a system undervoltage shutdown. However, the uncontrolled rectifier circuit topology used in this application automatically turns on the diodes in the rectifier bridge when the bus voltage drops below the rectifier circuit output voltage, introducing grid energy to fill the gap. When the bus voltage... The voltage drops below the output voltage of the AC uncontrolled rectifier circuit. (Approximately the effective value of AC input voltage) When the voltage is 311V (approximately 311V for single-phase 220V AC), the diodes in the rectifier bridge switch from reverse cutoff to forward bias conduction. The conduction condition of a rectifier diode is that its anode potential is higher than its cathode potential. In an uncontrolled rectifier circuit, the diode's anode is connected to the AC input side (the pulsating voltage after rectification), and the cathode is connected to the DC bus. When the bus voltage (cathode potential) is lower than the rectified voltage (anode potential), the diode automatically conducts under forward bias. AC current flows along the conduction path of the rectifier bridge into the DC bus, charging the bus capacitor and supplementing the insufficient energy from the photovoltaic system. When the bus voltage recovers to a level higher than the rectified voltage, the diode automatically cuts off again under reverse bias, and the grid power supply naturally stops.

[0092] Therefore, the core objective of both strategies is the same: to ensure uninterrupted power supply to the load and that the bus voltage does not exceed limits while maximizing the utilization of photovoltaic energy. The first strategy addresses excess power through software-based active power limiting, while the second strategy addresses insufficient power through hardware-based automatic energy replenishment. These two strategies complement each other, jointly covering all scenarios where photovoltaic power and load demand are matched under stable operating conditions. It is important to note that regardless of whether the first or second strategy is implemented, the aforementioned dual-loop control operates continuously, constantly fine-tuning the duty cycle based on bus voltage deviations to ensure the bus voltage remains stable near the target reference value. The synergistic relationship between the two power supply strategies and the dual-loop control is as follows: Figure 3 The diagram shown (modal dynamic power decoupling block diagram) together constitutes a complete power distribution and bus voltage regulation solution under stable operating conditions.

[0093] In an optional embodiment of this application, the method of responding to bus voltage dips by feeding forward bus capacitor current in step 204 may further include: Step 41: Calculate the feedforward compensation current based on the bus capacitance value, the bus voltage difference between the current time and the previous time, and the sampling period. The feedforward compensation current is equal to the product of the bus capacitance value and the bus voltage change rate. The feedforward compensation current is used to characterize the current required to suppress sudden changes in bus voltage. bus capacitor Connected in parallel across the two ends of the DC bus, its terminal voltage With the current flowing through the capacitor The following conditions must be met:

[0094] in, This represents the rate of change of the bus voltage. The formula shows that the rate of change of the bus voltage is directly proportional to the charging and discharging current of the capacitor. When the load suddenly increases, the load draws a large current from the bus, the bus capacitor discharges, and its terminal voltage decreases at a certain rate. The faster the voltage decreases (i.e., the higher the rate of change), the greater the rate of change. The larger the absolute value of the value, the greater the current released by the capacitor, that is, the greater the power gap.

[0095] As can be seen, if the rate of change of the bus voltage can be detected in real time, the amount of current required to suppress voltage drops can be calculated in reverse. This is the core idea of ​​feedforward compensation: using the currently detected rate of change of voltage, the required compensation current is directly calculated, and this compensation amount is injected into the control loop in the first sampling period.

[0096] Let the sampling period be The DC bus voltage at the current moment (the kth sampling time) is The DC bus voltage at the previous time step (the (k-1)th sampling step) was: The bus capacitance value is Then the feedforward compensation current Calculate using the following formula:

[0097] in, This represents the change in bus voltage within one sampling period. The rate of change of bus voltage (i.e. Discretization approximation).

[0098] Among them, feedforward compensation current This is used to characterize the supplemental current required to suppress sudden changes in bus voltage. The rate of change in bus voltage per second is equivalent to the number of coulombs of charge charged and discharged by the capacitor per second. Multiplying this rate of change by the capacitance value yields the corresponding current value, which is exactly equal to the compensation current needed to prevent further drops in bus voltage.

[0099] Step 42: The feedforward compensation current is superimposed on the current loop reference command so that the feedforward compensation amount enters the inner current loop to participate in regulation during the first sampling period when the bus voltage changes.

[0100] Among them, feedforward compensation current The base target current is directly superimposed onto the current loop reference command. for:

[0101] in, This is the feedforward compensation current at the current moment; This is a proportional compensation term, generated proportionally based on the deviation between the current bus voltage and the target value; This is the reference current for the previous cycle, used to maintain the continuity of the control quantity.

[0102] The baseline target current, after being limited, serves as the final reference command for the inner current loop, driving the PWM output.

[0103] The fact that the feedforward compensation participates in the current inner loop for regulation within the first sampling period when the bus voltage changes means that the calculation of the feedforward compensation is entirely based on the bus voltage data obtained within the current sampling period, without relying on the accumulation of historical errors. After the main control chip completes voltage sampling in the interrupt service routine of each sampling period, it immediately executes the feedforward compensation calculation and writes the result to the PWM compare register, which takes effect during the next PWM cycle update. The entire calculation and activation process is completed within one sampling period (e.g., 0.1ms), therefore the feedforward compensation participates in regulation within the first sampling period when the bus voltage changes.

[0104] It is evident that under dynamic and sudden operating conditions, if PI feedback control is still relied upon, the controller needs to wait for the bus voltage deviation to accumulate to a certain value before generating a sufficiently large adjustment. However, by this time, the bus voltage may have already fallen below the undervoltage protection threshold, causing the system to shut down. Feedforward compensation, by directly using the voltage change rate to calculate the compensation amount, fundamentally overcomes this delay, achieving proactive response. In other words, feedforward compensation does not rely on error accumulation but directly uses the voltage change rate to calculate the compensation amount, achieving predictive rather than reactive control. Compensation begins in the early stages of voltage drop, effectively suppressing further voltage drops. Furthermore, feedforward compensation provides information on the direction and magnitude of the required large replenishment current, ensuring that the control command can quickly reach the limit value under dynamic and sudden operating conditions; subsequent cycle-by-cycle hardware current limiting ensures that the command does not exceed hardware safety limits at the execution level. Together, these two elements constitute a complete control link for rapid energy replenishment and safe overcurrent control under dynamic and sudden operating conditions.

[0105] In an optional embodiment of this application, the method of outputting the limited PWM signal by hardware current limiting cycle by cycle involved in step 204 above may further include: Step 51: Based on the current loop reference command, the maximum peak current allowed by the switching transistor and inductor is used as the limiting value for truncation. Under dynamic and sudden operating conditions, the current loop reference command after superimposing the feedforward compensation is: Its value may be far greater than the hardware safety limit. Trimming / throttling involves pruning this value, that is,... With the maximum peak current allowed by the hardware If a comparison is made, Exceed Then take If the value is not exceeded, the actual value is used. To ensure safety, a safety factor (such as 0.9) is usually multiplied to leave a 10% margin.

[0106] in, This is the current value after limiting; The maximum peak current allowed for the switching transistor and inductor (determined by hardware parameters, such as 20A); 0.9 is a safety factor, providing a margin for the hardware. This is a current loop reference command that includes feedforward compensation.

[0107] It is evident that regardless of the theoretical current requirement calculated by the feedforward compensation, the final command current output to the inner current loop must not exceed the physical limits of the hardware. Any excess current is truncated, i.e., cut off. The truncated current value... It is the maximum current value that the hardware can safely withstand under the current operating conditions.

[0108] Step 52: Map the current value after limiting to a voltage threshold according to the sampled reference voltage, and compare the actual inductor voltage with the voltage threshold cycle by cycle; Within the main control chip (DSP / MCU), voltage signals, not current signals, are processed internally. The chip's ADC (Analog-to-Digital Converter) typically samples a reference voltage of 0~3.3V, and the PWM comparator also accepts a voltage signal as a comparison reference. Therefore, the current value after limiting needs to be... Converted to a voltage threshold that the chip can recognize. .

[0109] The mapping process is performed according to the following formula:

[0110] The current value after the limit cutoff (unit: A) represents the maximum current value that the hardware can safely withstand under the current operating conditions; 3.3V is the sampling reference voltage (full-scale voltage) of the chip's ADC. The current software ramp signal (a sawtooth or triangular wave sequence generated by the CPU chip, unit: V).

[0111] It can be seen that the current value after limiting The ratio to the reference voltage of 3.3V is used as a scaling factor (between 0 and 1) and multiplied by the current ramp signal amplitude. When When, the proportionality coefficient is Voltage threshold It equals the ramp signal amplitude multiplied by this coefficient, corresponding to a certain scale point of the hardware full scale; when When the value is small, the proportional coefficient is small, and the voltage threshold is correspondingly low.

[0112] Actual inductor voltage This is the voltage sample value across the inductor of the Boost circuit obtained through the sampling unit. Since the voltage drop across the sampling resistor or current detection circuit caused by the inductor current is proportional to the instantaneous inductor current, therefore... The amplitude directly reflects the magnitude of the instantaneous current in the inductor. The larger the value, the greater the actual current of the inductor.

[0113] Step 53: When the inductor voltage is less than the voltage threshold, output a high-level PWM signal; Step 54: When the inductor voltage is greater than or equal to the voltage threshold, output a low-level PWM signal.

[0114] It can be seen that using a hardware comparator to convert the actual inductor voltage With voltage threshold Real-time comparisons are performed within each PWM cycle, and the comparison logic is as follows: when When the current is below the target current limit after the current limiting is applied, the switching transistor can continue to conduct to increase the current. At this time, the PWM output is high and the switching transistor is turned on.

[0115] when When the current actual current of the inductor has reached or exceeded the target current limit after the limit is set, as described in claim 8, the system outputs a low-level PWM signal. At this time, the hardware comparator immediately forces the PWM output to be low and turns off the switching transistor.

[0116] As can be seen, the final output PWM signal is the limited PWM signal. This means that regardless of the theoretical current command calculated by the feedforward compensation, after limiting and cycle-by-cycle comparison, the actual output PWM signal ensures that the switching transistor is forcibly turned off once the inductor current reaches the limit value in each PWM cycle, thus preventing the inductor current from exceeding the maximum peak current allowed by the hardware. Therefore, through limiting and cycle-by-cycle comparison, no matter how large the theoretical current calculated by the feedforward compensation is, the current corresponding to the final actual output PWM signal will not exceed the hardware safety limit, ensuring that the switching transistor and inductor will not be damaged due to overcurrent.

[0117] Furthermore, such as Figure 4 As shown, the method in this application embodiment may further include: Step 401: Extract the ripple component from the DC bus voltage for active compensation, and control the voltage of the ripple compensation capacitor to synthesize a control signal to drive the compensation capacitor to absorb or release pulsating energy.

[0118] Existing methods for suppressing ripple mainly include passive approaches such as increasing the bus capacitor capacity and adding LC filter circuits. However, increasing the bus capacitor capacity significantly increases the system's size, weight, and cost, and the lifespan and reliability of large-capacity electrolytic capacitors are significant issues. This invention employs an active ripple suppression scheme by adding a ripple compensation capacitor to the DC bus. It also works with the control loop to actively control its charging and discharging current, thereby achieving efficient suppression of ripple at specific frequencies.

[0119] Combination Figure 5 The method of actively compensating for the ripple component extracted from the DC bus voltage and controlling the ripple compensation capacitor voltage to synthesize a control signal to drive the compensation capacitor to absorb or release pulsating energy, as involved in step 401 above, may further include: Step 61: Sample the DC bus voltage, and extract the ripple component by subtracting the DC component obtained by low-pass filtering from the DC bus voltage. Then, subtract the ripple component from zero and send it to the proportional resonant controller to generate the first reference current for canceling the ripple. DC bus voltage sampling value It consists of two components: a DC component and an AC ripple component. To obtain the ripple component, the DC component needs to be removed from the sampled values.

[0120] As can be seen, the sampled DC bus voltage is first subjected to low-pass filtering. Low-pass filter The transfer function is:

[0121] in Characteristic angular frequency ( (Take 50Hz). This low-pass filter allows low-frequency signals (DC component) to pass through while filtering out high-frequency signals (AC ripple component).

[0122] Original sampling voltage The ripple component can be extracted by subtracting the DC component obtained after low-pass filtering. :

[0123] Extracted ripple components The difference between the value and zero (i.e., using zero as a reference value, with the goal of controlling the ripple component to zero) is fed into a proportional resonant (PR) controller to generate the first reference current. .

[0124] Proportional Resonant Controller The transfer function is:

[0125] in, For proportional gain; This is the resonant gain; The angular frequency of the nth order ripple ( , ).

[0126] The core characteristic of a proportional-resonant controller (PR controller) lies in its theoretically infinite gain at its resonant frequency. This means that for AC signals of specific frequencies (such as a second-order ripple at 100Hz, a fourth-order ripple at 200Hz, etc.), the PR controller can produce near-perfect tracking, ensuring the output signal tracks the input signal without steady-state error. In specific applications, the bus ripple generated by a single-phase uncontrolled rectifier mainly includes even-order harmonic components such as the 2nd (100Hz), 4th (200Hz)...12th (600Hz). The PR controller... High gain is provided at each resonant frequency, thereby suppressing the aforementioned ripple components simultaneously.

[0127] Among them, the output of the PR controller This is the first reference current used to cancel ripple. Its working principle is: when the ripple component... When the ripple component is positive (bus voltage is higher than the average DC value), the PR controller outputs a negative compensation current command, requiring the ripple compensation capacitor to absorb excess energy; when the ripple component is negative (bus voltage is lower than the average DC value), the PR controller outputs a positive compensation current command, requiring the ripple compensation capacitor to release energy to fill the gap. Through this reverse compensation mechanism, the ripple component is effectively canceled out.

[0128] Step 62: Sample the voltage of the ripple compensation capacitor and generate a second reference current through a proportional-integral controller with a preset reference value as the target. The second reference current is used to maintain the DC bias voltage of the ripple compensation capacitor at the set value. Ripple compensation capacitor In this application, it plays the role of an active filter. To enable... To achieve good ripple absorption and release capabilities, the DC bias voltage across its terminals needs to be controlled at an appropriate level. If the bias voltage is too low, the capacitor's energy storage capacity will be insufficient, limiting the ripple compensation effect; if the bias voltage is too high, there is a risk of capacitor breakdown.

[0129] The voltage of the ripple compensation capacitor is obtained in real time through the sampling unit. and compared with the preset reference value (Typically 400V) is used for comparison, and the deviation is sent to a proportional-integral (PI) controller to generate a second reference current. :

[0130] in This is the transfer function of the proportional-integral controller.

[0131] Among them, the second reference current Its function is to maintain the DC bias voltage of the ripple compensation capacitor at the set value. When When the value is below the reference value, the PI controller outputs a positive current command, requesting the compensation capacitor to be charged; when... When the voltage exceeds the reference value, the PI controller outputs a negative current command, requesting the compensation capacitor to discharge. Through this closed-loop control, the DC bias voltage of the compensation capacitor is stabilized at a preset value, ensuring that it has optimal ripple compensation capability.

[0132] Step 63: Subtract the actual inductor current from the sum of the first reference current and the second reference current, and output a PWM drive signal through the proportional controller. The PWM drive signal controls the switching transistor to turn on and off, so that the charging and discharging current flowing through the ripple compensation capacitor tracks the sum of the first reference current and the second reference current, so that the ripple compensation capacitor absorbs or releases the pulsating energy.

[0133] The ripple compensation reference current output by the PR controller The reference current is maintained by the bias voltage output of the PI controller. The sums are used to obtain the total reference current. This total reference current is then subtracted from the actual inductor current sample value. The difference is amplified by a proportional controller and then output as a PWM drive signal.

[0134] in, This is the proportional control coefficient (value 0~1, determined through integrated testing of the whole machine).

[0135] The PWM drive signal controls the switching transistor's on and off states, causing the charging and discharging current flowing through the ripple compensation capacitor to track the sum of the first reference current and the second reference current. Specifically: when When this occurs, it indicates that the current flowing through the compensation capacitor needs to be increased (charging), the PWM duty cycle increases, and the on-time of the switching transistor is prolonged; when When this occurs, it indicates that the current flowing through the compensation capacitor needs to be reduced (discharge), the PWM duty cycle decreases, and the on-time of the switching transistor is shortened.

[0136] Through this feedback control mechanism, the actual charging and discharging current of the ripple compensation capacitor is precisely controlled near the target value. As a result, when ripple occurs in the bus voltage, the compensation capacitor actively absorbs or releases pulsating energy according to the instructions of the PR controller, thereby offsetting the ripple component on the bus voltage. In other words, the effective suppression of bus voltage ripple reduces torque pulsation transmitted to the compressor drive, lowers compressor vibration and noise, and extends the compressor's service life.

[0137] like Figure 6 As shown in the figure, this application provides an electronic device including a processor 611, a communication interface 612, a memory 613, and a communication bus 614, wherein the processor 611, the communication interface 612, and the memory 613 communicate with each other through the communication bus 614. Memory 613 is used to store computer programs; In one embodiment of this application, when the processor 611 executes the program stored in the memory 613, it implements the control method of the circuit based on the photovoltaic direct-drive compressor provided in any of the aforementioned method embodiments, and its function is similar, so it will not be described again here.

[0138] This application also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the control method based on a photovoltaic direct-drive compressor circuit as provided in any of the foregoing method embodiments.

[0139] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0140] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented using software plus a general-purpose hardware platform, or of course, using hardware. Based on this understanding, the above technical solutions, in essence or the parts that contribute to the related technology, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0141] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0142] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A photovoltaic direct drive compressor circuit, characterized by, include: Photovoltaic boost converter circuit, AC uncontrolled rectifier circuit, bus capacitor and ripple compensation capacitor; The photovoltaic Boost circuit consists of at least one photovoltaic input branch. Each photovoltaic input branch includes an inductor, a switching transistor, and a diode. One end of the inductor is connected to the positive terminal of the photovoltaic input, and the other end of the inductor is connected to the first terminal of the switching transistor and the anode of the diode. The second terminal of the switching transistor is connected to the negative terminal of the photovoltaic input. The cathode of the diode is the output terminal of the photovoltaic input branch. The output terminals of each photovoltaic input branch are connected in parallel and then converge to the positive terminal of the DC bus. The input terminals of each photovoltaic input branch are connected to the negative terminal of the DC bus. The AC input terminal of the uncontrolled AC rectifier circuit is connected to a single-phase AC power supply. The positive terminal of the DC output terminal of the uncontrolled AC rectifier circuit is connected to the positive terminal of the DC bus, and the negative terminal of the DC output terminal of the uncontrolled AC rectifier circuit is connected to the negative terminal of the DC bus. This is used to rectify the AC power and feed it into the DC bus, so as to supply power to the DC bus together with the photovoltaic Boost boost circuit. The positive terminal of the bus capacitor is connected to the positive terminal of the DC bus, and the negative terminal of the bus capacitor is connected to the negative terminal of the DC bus, and is connected in parallel between the positive and negative terminals of the DC bus. The positive terminal of the ripple compensation capacitor is connected to the positive terminal of the DC bus, and the negative terminal of the ripple compensation capacitor is connected to the negative terminal of the DC bus, and is connected in parallel between the positive and negative terminals of the DC bus.

2. The circuit of claim 1, wherein, The circuit also includes a pre-charge protection circuit, which consists of a pre-charge resistor and a contactor connected in series and then in parallel between the positive and negative terminals of the DC bus, to suppress the inrush current at the moment the system is powered on.

3. A control method based on the photovoltaic direct-drive single-phase compressor circuit according to claim 1 or 2, characterized in that, The method includes: Sample the DC bus voltage at the current moment and the DC bus voltage at the previous moment to determine the rate of change of the bus voltage; If the rate of change of the bus voltage is greater than a preset threshold and the current DC bus voltage is lower than a preset low voltage threshold, then the circuit of the photovoltaic direct-drive compressor is determined to be in a dynamic change condition; otherwise, the circuit of the photovoltaic direct-drive compressor is determined to be in a stable condition. Under the stable operating conditions, the current maximum photovoltaic power generation capacity of the photovoltaic Boost circuit is compared with the load demand, and a corresponding power supply strategy is determined based on the comparison result. The duty cycle of the photovoltaic Boost circuit is adjusted using a dual-loop control system combining the bus voltage deviation with the voltage outer loop and current inner loop. The power supply strategy refers to the strategy used to meet the current load demand; the bus voltage deviation refers to the difference between the actual sampled value of the DC bus voltage and the preset target reference value. Under the dynamic change condition, the bus voltage drop is compensated by the bus capacitor current feedforward, and the limited PWM signal is output by hardware current limiting on a cycle-by-cycle basis.

4. The method according to claim 3, characterized in that, Compare the current maximum photovoltaic power generation capacity of the photovoltaic boost circuit with the load demand, including: The power-voltage slope sign is determined based on the difference in photovoltaic power and the difference in photovoltaic voltage between the current time and the previous time. The slope sign represents the direction of the current operating point relative to the maximum power point. When the slope is positive, the duty cycle needs to be increased to increase the photovoltaic voltage. When the slope is negative, the duty cycle needs to be decreased to decrease the photovoltaic voltage. An adaptive factor is determined based on the bus voltage deviation. When the bus voltage deviation is greater than a preset threshold, the adaptive factor takes a first value. When the bus voltage deviation is less than or equal to the preset threshold, the adaptive factor takes a second value. The first value is greater than the second value. The duty cycle adjustment of the photovoltaic Boost circuit at the current moment is obtained by multiplying the determined adaptive factor by the slope sign and then by the base step size, and the photovoltaic operating point voltage after updating the duty cycle is determined as the current maximum photovoltaic power generation capacity. Based on the determined maximum photovoltaic power generation capacity, the current maximum photovoltaic power generation capacity of the photovoltaic Boost circuit is compared with the load demand.

5. The method according to claim 3, characterized in that, The duty cycle of the photovoltaic Boost converter circuit is adjusted using a dual-loop control system combining the bus voltage deviation with the outer voltage loop and the inner current loop, including: In the outer voltage loop, a reference current is generated by proportional-integral control based on the bus voltage deviation, wherein the reference current is characterized as the target current drawn from the photovoltaic side required to eliminate the bus voltage deviation. In the inner current loop, the smaller of the actual photovoltaic output power and the load demand power is taken as the target power, and the target power is divided by the photovoltaic voltage to obtain the inductor current reference value. The difference between the inductor current reference value and the actual inductor current sample value is compared with a preset hysteresis width, and a PWM signal is output according to the comparison result. The duty cycle of the PWM signal is the duty cycle that the photovoltaic Boost circuit is currently actually executing.

6. The method according to claim 3, characterized in that, The corresponding power supply strategy is determined based on the comparison results, including: When the maximum power generation capacity of the photovoltaic system exceeds the load demand, the first power supply strategy is executed, wherein the first power supply strategy refers to limiting the actual output power of the photovoltaic boost circuit to the load demand level. When the maximum photovoltaic power generation capacity is insufficient to meet the load demand, a second power supply strategy is implemented. The second power supply strategy refers to the automatic forward biasing and conduction of the diodes in the AC uncontrolled rectifier circuit when the bus voltage drops below the output voltage of the AC uncontrolled rectifier circuit, and the grid energy is injected into the bus through the AC uncontrolled rectifier circuit to make up the difference.

7. The method according to claim 3, characterized in that, Response to bus voltage dips through bus capacitor current feedforward compensation includes: The feedforward compensation current is calculated based on the bus capacitance value, the bus voltage difference between the current time and the previous time, and the sampling period. The feedforward compensation current is equal to the product of the bus capacitance value and the bus voltage change rate. The feedforward compensation current is used to characterize the current required to suppress sudden changes in bus voltage. The feedforward compensation current is superimposed on the current loop reference command, so that the feedforward compensation amount enters the inner current loop to participate in regulation during the first sampling period when the bus voltage changes.

8. The method according to claim 7, characterized in that, The PWM signal is output after being limited by hardware current limiting on a cycle-by-cycle basis, including: Based on the current loop reference command, the maximum peak current allowed by the switching transistor and inductor is used as the limiting value for truncation. The current value after limiting is mapped to a voltage threshold according to the sampled reference voltage, and the actual inductor voltage is compared with the voltage threshold cycle by cycle. When the inductor voltage is less than the voltage threshold, a high-level PWM signal is output; When the inductor voltage is greater than or equal to the voltage threshold, a low-level PWM signal is output.

9. The method according to claim 3, characterized in that, The method further includes: The ripple component in the DC bus voltage is extracted for active compensation, and the voltage of the ripple compensation capacitor is controlled to synthesize a control signal to drive the compensation capacitor to absorb or release pulsating energy.

10. The method according to claim 9, characterized in that, The process involves extracting the ripple component from the DC bus voltage for active compensation and controlling the ripple compensation capacitor voltage to synthesize a control signal that drives the compensation capacitor to absorb or release pulsating energy. The DC bus voltage is sampled, and the ripple component is extracted by subtracting the DC component obtained by low-pass filtering from the DC bus voltage. The difference between the ripple component and zero is then sent to the proportional resonant controller to generate a first reference current for canceling the ripple. The voltage of the ripple compensation capacitor is sampled, and a second reference current is generated by a proportional-integral controller with a preset reference value as the target. The second reference current is used to maintain the DC bias voltage of the ripple compensation capacitor at the set value. After subtracting the actual inductor current from the sum of the first reference current and the second reference current, a PWM drive signal is output through the proportional controller. The PWM drive signal controls the switching transistor to turn on and off, so that the charging and discharging current flowing through the ripple compensation capacitor tracks the sum of the first reference current and the second reference current, so that the ripple compensation capacitor absorbs or releases the pulsating energy.

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