Efficient solar inverter topological structure based on MPPT and control method thereof

Abstract

The invention relates to the technical field of solar inverters, and discloses an MPPT (maximum power point tracking)-based efficient solar inverter topological structure and a control method thereof, and the topological structure is characterized in that the output end of a solar cell array is sequentially connected with an input EMI (electro-magnetic interference) filter, a multi-phase interleaving soft switching Boost circuit and a three-phase full-bridge inverter circuit; the Boost circuit is composed of at least two parallel branches, each branch comprises a power switch tube, a resonant element, a diode and an energy storage inductor, the input end of each branch is connected with the output of the EMI filter, the output end of each branch is connected with a direct-current bus, and the phases of drive signals of the power switch tubes are mutually different to form staggered work. The direct current side of the three-phase full-bridge inverter is connected with a direct current bus, and the alternating current side is output through an LCL filter and an isolation transformer; the MPPT control unit is arranged between the battery array and the EMI filter; and the phase controller is used for generating driving signals of each Boost branch. According to the invention, switching loss and electromagnetic interference are reduced, and the overall energy conversion efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of solar inverter technology, and more specifically, to a high-efficiency solar inverter topology based on MPPT and its control method. Background Technology

[0002] With the continuous expansion of large-scale photovoltaic power generation applications, solar inverters, as key energy conversion devices connecting photovoltaic modules and the power grid, directly affect the system's power generation efficiency and stability. Existing inverters mostly adopt a topology combining traditional Boost converter circuits with a full-bridge inverter structure, achieving maximum power point tracking through the MPPT algorithm. However, under conditions of frequent changes in solar irradiance and ambient temperature, this type of topology suffers from problems such as large input current ripple, high energy transmission losses, severe overheating of switching devices, and slow dynamic response speed, making it difficult to meet the design requirements of high power density and high efficiency simultaneously.

[0003] To improve energy conversion efficiency, some studies have attempted to use multiphase interleaved parallel structures to reduce current ripple and improve heat distribution. However, the current balancing and phase control among multiple branches are complex, which can easily lead to control instability or efficiency degradation. On the other hand, traditional MPPT algorithms often use perturbation-observation or incremental conductance methods, which only adjust for changes in output voltage and current, failing to fully consider the dynamic characteristics of power circuits, resulting in insufficient tracking accuracy and increased steady-state fluctuations.

[0004] Therefore, it is necessary to design a high-efficiency solar inverter topology based on MPPT and its control method to solve the problems existing in the current technology. Summary of the Invention

[0005] In view of this, the present invention proposes a high-efficiency solar inverter topology based on MPPT and its control method, aiming to solve the problems of complex current balancing and phase control among multiple branches, which easily leads to control instability or efficiency reduction, as well as insufficient tracking accuracy and increased steady-state fluctuations caused by failure to fully consider the dynamic characteristics of the power circuit.

[0006] In one aspect, this invention proposes a high-efficiency solar inverter topology based on MPPT, comprising:

[0007] The output of the solar cell array is connected to an input EMI filter, a multi-phase interleaved parallel soft-switching Boost circuit, and a three-phase full-bridge inverter circuit.

[0008] The multiphase interleaved parallel soft-switching Boost circuit includes at least two parallel soft-switching Boost conversion branches. Each soft-switching Boost conversion branch includes a power switch, a resonant element, a diode, and an energy storage inductor. The input terminal of each soft-switching Boost conversion branch is connected to the output terminal of the input EMI filter, and the output terminal of each soft-switching Boost conversion branch is connected to the DC bus. The power switch driving signals in each soft-switching Boost conversion branch are phase-differentiated, forming an interleaved operating mode.

[0009] The DC side of the three-phase full-bridge inverter circuit is connected to the DC bus, and the AC side is connected to an LCL filter and an isolation transformer. The LCL filter includes an inverter-side inductor, a filter capacitor, and a grid-side inductor. The inverter-side inductor is connected to the AC output terminal of the three-phase full-bridge inverter circuit. One end of the filter capacitor is connected to the inverter-side inductor, and the other end is grounded. The grid-side inductor is connected to the filter capacitor and the isolation transformer.

[0010] It also includes an MPPT control unit and a phase controller. The MPPT control unit is located between the output of the solar cell array and the input EMI filter. The phase controller is used to generate drive signals for each power switch in each soft-switching Boost conversion branch.

[0011] Furthermore, including:

[0012] The MPPT control unit is configured to acquire photovoltaic voltage and photovoltaic current signals, calculate the real-time output power of the solar cell array, determine the maximum power point (MPPT) location based on the incremental conductance method, compare the real-time output power with a power threshold to determine the current power region of the solar cell array, which includes a low-power region and a high-power region, determine the maximum power point voltage reference value based on the MPPT location, and generate a corresponding power adjustment command based on the current power region, and integrate the maximum power point voltage reference value and the power adjustment command into an MPPT control signal.

[0013] The phase controller is configured to dynamically adjust the operating state of all soft-switching Boost switching branches in the multi-phase interleaved parallel soft-switching Boost circuit according to the MPPT control signal output; calculate the phase offset and duty cycle adjustment value of the drive signal of the power switch in each soft-switching Boost switching branch based on the DC bus voltage data and the current data of all soft-switching Boost switching branches using a closed-loop feedback control algorithm, so that the photovoltaic array output voltage tracks the maximum power point voltage reference value; and generate a precise PWM drive signal based on the phase offset and duty cycle adjustment value of the drive signal using a digital signal processor to control the turn-on and turn-off timing of the power switch in each soft-switching Boost switching branch.

[0014] The phase controller is also configured to monitor the voltage and current waveforms of the power switching transistors in each soft-switching Boost conversion branch in real time. When the soft-switching condition is not met, the phase offset of the drive signal is dynamically adjusted based on the power region information in the MPPT control signal to restore the soft-switching working state of the power switching transistors and maintain the tracking accuracy of the maximum power point voltage reference value.

[0015] Furthermore, when the MPPT control unit acquires photovoltaic voltage and current signals and calculates the real-time output power of the solar cell array, it includes:

[0016] The photovoltaic voltage signal and photovoltaic current signal are acquired based on the signal conditioning circuit and digitally filtered; the photovoltaic voltage signal and photovoltaic current signal after digital filtering are multiplied in real time to obtain the instantaneous power value; the instantaneous power value is used as the real-time output power; the digital filtering includes the use of a moving average algorithm and amplitude limiting filtering.

[0017] Furthermore, when the MPPT control unit determines the location of the maximum power point based on the incremental conductance method, it includes:

[0018] Apply a voltage disturbance to the current operating point and measure the voltage and current changes before and after the disturbance. Calculate the ratio of the conductance increment to the instantaneous conductance. When the ratio is greater than zero, adjust the operating point in the direction of increasing voltage. When the ratio is less than zero, adjust the operating point in the direction of decreasing voltage. When the ratio is equal to zero, determine that the maximum power point has been reached.

[0019] Furthermore, when the phase controller dynamically adjusts the operating state of all soft-switching Boost switching branches in the multi-phase interleaved parallel soft-switching Boost circuit according to the MPPT control signal output, it includes:

[0020] When the power adjustment command indicates a low-power region, the number of operating soft-switching Boost conversion branches is reduced, the phase difference between operating branches is increased, and the power switching transistors of each soft-switching Boost conversion branch are ensured to achieve zero-voltage or zero-current switching under low-power conditions. When the power adjustment command indicates a high-power region, the number of operating soft-switching Boost conversion branches is increased, the phase difference between operating branches is decreased, the total input current ripple is reduced, and the power switching transistors of all operating branches are ensured to maintain soft-switching conditions. The number of operating soft-switching Boost conversion branches is adjusted based on the balanced distribution of current stress in each soft-switching Boost conversion branch and the fact that the power density of each soft-switching Boost conversion branch is less than the safe operating area limit.

[0021] Furthermore, the phase controller, through a digital signal processor, generates a precise PWM drive signal based on the calculated phase offset and duty cycle adjustment value of the drive signal. When controlling the turn-on and turn-off timing of the power switching transistors in each soft-switching Boost conversion branch, it includes:

[0022] The maximum power point voltage reference value is compared with the acquired photovoltaic voltage signal to calculate the voltage error signal; the voltage error signal is input to a proportional-integral controller to generate a current reference value; the proportional-integral controller includes a proportional term and an integral term, the proportional term generates a control action based on the instantaneous value of the voltage error signal, and the integral term accumulates the voltage error signal;

[0023] The current reference value is compared with the current data of all the soft-switching Boost conversion branches to calculate the current error signal; the current error signal is input to the proportional resonant controller to calculate and generate the phase offset and duty cycle adjustment value of the drive signal.

[0024] The proportional resonant controller includes a proportional term and a resonant term. The proportional term provides system damping and accelerates dynamic response, while the resonant term provides high gain characteristics at the fundamental frequency, enabling zero steady-state error tracking of the sinusoidal reference signal.

[0025] The phase offset is used to adjust the phase relationship between the drive signals of the power switches in each branch, and the duty cycle adjustment value is used to adjust the on-time of the power switches in each branch.

[0026] Furthermore, the phase controller, through a digital signal processor, generates a precise PWM drive signal based on the calculated phase offset and duty cycle adjustment value of the drive signal. When controlling the turn-on and turn-off timing of the power switching transistors in each soft-switching Boost conversion branch, it includes:

[0027] The phase offset and duty cycle adjustment values ​​are superimposed with preset phase reference signals and duty cycle reference signals to generate the final drive signal parameters of the power switching transistors in each soft-switching Boost conversion branch. The final drive signal parameters are converted into precise PWM drive signals by a digital signal processor to control the turn-on and turn-off timing of the power switching transistors in each soft-switching Boost conversion branch.

[0028] Furthermore, when the soft-switching condition is detected as not being met, the phase controller dynamically adjusts the phase offset of the drive signal based on the power region information in the MPPT control signal, including:

[0029] Within a preset time window before the power switch is turned on, it is detected whether the voltage across the power switch is lower than a preset voltage threshold. If the voltage before turn-on is lower than the preset voltage threshold, the zero-voltage switching condition is met. Within a preset time window before the power switch is turned off, it is detected whether the current flowing through the power switch is lower than a preset current threshold. If the current before turn-off is lower than the preset current threshold, the zero-current switching condition is met. If the voltage across the power switch is not lower than the preset voltage threshold before turn-on, or the current flowing through the power switch is not lower than the preset current threshold before turn-off, the soft-switching condition is not met.

[0030] When the soft-switching condition is not met, the reference step size for phase offset adjustment is determined based on the current power region; the adjustment coefficient is calculated based on the degree of deviation from the soft-switching condition; and the actual phase offset adjustment is obtained by multiplying the reference step size by the adjustment coefficient.

[0031] Furthermore, when the phase controller restores the soft-switching operation of the power switch to maintain the tracking accuracy of the maximum power point voltage reference value, it includes:

[0032] The change in output voltage of the photovoltaic array is calculated based on the phase offset adjustment; the negative value of the voltage change is superimposed on the maximum power point voltage reference value as a compensation; the impact of the phase offset adjustment on the operating point of the photovoltaic array is offset in advance, ensuring that the photovoltaic array continues to operate near the maximum power point.

[0033] Compared with existing technologies, the advantages of this invention are as follows: It employs a multi-phase interleaved parallel soft-switching Boost circuit structure, where each branch shares the input current through phase shifting, reducing current ripple and inductor current stress. Simultaneously, it utilizes resonant elements to achieve zero-voltage or zero-current soft switching of the power switching transistors, reducing switching losses and electromagnetic interference, and improving overall energy conversion efficiency. The MPPT control unit calculates the power change trend of the photovoltaic array in real time based on the incremental conductance method, and achieves adaptive adjustment through power region determination and dynamic voltage disturbance. This allows it to maintain the solar cell array near its maximum power point even under rapid changes in light or temperature, thereby increasing the output power of the photovoltaic power generation system. The phase controller dynamically adjusts the number of parallel branches and phase difference distribution according to the MPPT control signal, reducing the number of working branches in the low-power region and increasing the number of working branches in the high-power region. This achieves balanced distribution of current stress and adaptive control of branch power density, reducing device losses and thermal stress, and improving system stability and lifespan. By combining a proportional-integral controller (PIC) with a proportional-resonant controller, the phase offset and duty cycle adjustment values ​​can be accurately calculated under dual closed-loop voltage and current conditions, enabling the PWM drive signal to have a fast dynamic response capability. When the soft-switching condition is not met, the controller can dynamically correct the phase offset based on power region information, achieving rapid recovery of the soft-switching condition and maintaining stable operation of the system in the high-efficiency range. By calculating the drive signal parameters in real time and performing dynamic compensation through a digital signal processor, the impact of phase adjustment on the photovoltaic array voltage can be offset in advance, allowing the system to maintain stable tracking of the maximum power point under load fluctuations or external disturbances, exhibiting excellent anti-disturbance performance.

[0034] On the other hand, this application also provides a high-efficiency solar inverter topology control method based on MPPT, for applying the above-mentioned high-efficiency solar inverter topology based on MPPT, including:

[0035] Photovoltaic voltage and current signals are acquired to calculate the real-time output power of the solar cell array. The location of the maximum power point (MPPT) is determined based on the incremental conductance method. The real-time output power is compared with a power threshold to determine the current power region of the solar cell array, which includes a low-power region and a high-power region. A reference value for the maximum power point voltage is determined based on the location of the MPPT, and a corresponding power adjustment command is generated based on the current power region. The reference value for the MPPT voltage and the power adjustment command are integrated into an MPPT control signal.

[0036] The operating state of all soft-switching Boost switching branches in the multi-phase interleaved parallel soft-switching Boost circuit is dynamically adjusted according to the MPPT control signal output; based on the DC bus voltage data and the current data of all soft-switching Boost switching branches, the phase offset and duty cycle adjustment value of the drive signal of the power switch in each soft-switching Boost switching branch are calculated based on the closed-loop feedback control algorithm, so that the photovoltaic array output voltage tracks the maximum power point voltage reference value; a precise PWM drive signal is generated by the digital signal processor based on the phase offset and duty cycle adjustment value of the drive signal to control the turn-on and turn-off timing of the power switch in each soft-switching Boost switching branch;

[0037] The voltage and current waveforms of the power switching transistors in each soft-switching Boost conversion branch are monitored in real time. When the soft-switching condition is not met, the phase offset of the drive signal is dynamically adjusted based on the power region information in the MPPT control signal to restore the soft-switching working state of the power switching transistors and maintain the tracking accuracy of the maximum power point voltage reference value.

[0038] It is understandable that the above-mentioned high-efficiency solar inverter topology and control method based on MPPT have the same beneficial effects, and will not be elaborated further here. Attached Figure Description

[0039] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0040] Figure 1 A schematic diagram of the structure of a high-efficiency solar inverter topology based on MPPT provided in an embodiment of the present invention;

[0041] Figure 2 A flowchart of a high-efficiency solar inverter topology control method based on MPPT provided in an embodiment of the present invention.

[0042] The components include: 1. Solar cell array; 2. EMI filter; 3. Multiphase interleaved parallel soft-switching Boost circuit; 4. DC bus; 5. Three-phase full-bridge inverter circuit; 6. LCL filter; 7. Isolation transformer; 8. MPPT control unit; and 9. Phase controller. Detailed Implementation

[0043] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0044] Existing photovoltaic inverters typically employ a topology combining single-phase or multi-phase boost converters with full-bridge inverters, using the traditional MPPT algorithm to achieve maximum power point tracking. However, this approach has several drawbacks: First, the input current ripple is large, leading to increased heating of power switches and filter components, reducing device lifespan. Second, the dynamic response speed is slow, failing to quickly adjust the operating point when sunlight intensity changes rapidly, resulting in power loss. Third, the parallel control of multiple branches is complex, and current imbalances can easily cause control instability or overload of some branches. Fourth, the traditional MPPT algorithm is based solely on voltage and current disturbance regulation, making it difficult to balance soft-switching conditions with maximum power point tracking accuracy, thus reducing overall system efficiency and reliability.

[0045] For example, in large-scale photovoltaic power plants, if traditional single-phase Boost full-bridge inverters are used, the inverter input voltage changes rapidly when solar irradiance suddenly increases in the morning. The response lag of existing MPPT algorithms can cause the photovoltaic modules' output power to fail to reach its maximum value in a timely manner. Simultaneously, due to the large input current ripple in single-branch or non-interleaved multi-branch Boost circuits, the temperature rise of the power switching transistors increases, which may trigger overheat protection during long-term operation, reducing the system's continuous power generation capacity and equipment lifespan. This situation is particularly pronounced under strong sunlight conditions in summer, directly impacting the annual power generation of the photovoltaic power plant.

[0046] For this, please refer to Figure 1 As shown, a high-efficiency solar inverter topology based on MPPT includes:

[0047] The output of solar cell array 1 is connected to input EMI filter 2, multi-phase interleaved parallel soft-switching Boost circuit 3 and three-phase full-bridge inverter circuit 5;

[0048] The multiphase interleaved parallel soft-switching Boost circuit 3 includes at least two parallel soft-switching Boost conversion branches. Each soft-switching Boost conversion branch includes a power switch, a resonant element, a diode, and an energy storage inductor. The input terminal of each soft-switching Boost conversion branch is connected to the output terminal of the input EMI filter 2, and the output terminal of each soft-switching Boost conversion branch is connected to the DC bus 4. The power switch driving signals in each soft-switching Boost conversion branch are phase-differentiated, forming an interleaved operating mode.

[0049] The DC side of the three-phase full-bridge inverter circuit 5 is connected to the DC bus 4, and the AC side is connected to the LCL filter 6 and the isolation transformer 7. The LCL filter 6 includes an inverter-side inductor, a filter capacitor and a grid-side inductor. The inverter-side inductor is connected to the AC output terminal of the three-phase full-bridge inverter circuit 5. One end of the filter capacitor is connected to the inverter-side inductor and the other end is grounded. The grid-side inductor is connected to the filter capacitor and the isolation transformer 7.

[0050] It also includes an MPPT control unit 8 and a phase controller 9. The MPPT control unit 8 is located between the output of the solar cell array 1 and the input EMI filter 2. The phase controller 9 is used to generate drive signals for each power switch in each soft-switching Boost conversion branch.

[0051] Specifically, this topology consists of a solar cell array 1, an input EMI filter 2, a multi-phase interleaved parallel soft-switching boost stage, and a three-phase full-bridge inverter stage. The positive and negative outputs of the photovoltaic array first pass through the input EMI filter 2 (differential / common-mode inductors, X / Y capacitors) to suppress switching noise before being connected in parallel to the multi-phase interleaved parallel soft-switching boost stage and the MPPT sampling port. The soft-switching boost stage consists of at least two identical parallel conversion branches (expandable to 4 or 6 phases, etc.). Each branch consists of a power switch (it is recommended to use wide-bandgap devices such as SiC MOSFETs or GaN FETs to reduce switching losses), auxiliary resonant components (capacitors / inductors connected in series or in parallel to achieve ZVS / ZCS conditions), a freewheeling diode (or synchronous rectifier), and an energy storage inductor. The input terminals of each branch are connected in parallel to the output of the EMI filter 2, and the output terminals are connected in parallel to the DC bus 4. Large-capacity electrolytic / solid-state capacitors are connected in parallel on the bus to stabilize the DC voltage and supply it to the subsequent inverter stage. The gate drive of each branch is controlled by a phase-staggered PWM drive signal generated by the phase controller 9, forming an n-phase interleaved operation to evenly distribute the input current and reduce ripple; the gate driver must have isolation drive, short-circuit / undervoltage lockout, and adjustable dead time functions. The DC bus 4 supplies the three-phase full-bridge inverter unit. The inverter adopts a six-transistor full-bridge topology. On the AC side, there is an LCL filter 6 composed of inverter-side inductors, filter capacitors, and grid-side inductors. The filter parameters are designed according to the cutoff frequency, resonant damping, and grid connection specifications, and are connected to the grid through an isolation transformer 7; voltage and current sampling points are provided on both the inverter side and the grid side for closed-loop control and fault detection. Control / measurement is implemented by a high-speed DSP or MCU (such as TI C2000 series or STM32G4 series), including ADC channel acquisition of photovoltaic voltage / current, current of each Boost branch, DC bus 4 voltage, inverter output current / voltage and waveforms at both ends of the switching transistor; MPPT unit (such as incremental conductance method) calculates MPP voltage and power region on the array side and outputs MPPT control signal; phase controller 9 calculates phase offset and duty cycle correction of each branch through PI / PI+ proportional resonance (PR) closed loop algorithm based on DC bus 4 voltage error, current distribution and soft switching detection (voltage threshold before conduction, current threshold before turn-off), and after digitization, drives the gate with high-resolution PWM (sampling frequency much higher than the fundamental frequency, resolution usually 12-16 bits) to ensure phase synchronization and accurate dead-time control. The system incorporates soft-switching detection logic, fault and protection (overcurrent, overvoltage, undervoltage, overtemperature, and out-of-step protection), soft-start, and grid-connected synchronization (PLL) modules. When the soft-switching conditions are not met, the controller selects a reference step size according to the power range and calculates a coefficient according to the degree of deviation. It then adjusts the phase in real time to restore ZVS / ZCS. At the same time, the photovoltaic operating point offset caused by the phase adjustment is added back to the MPPT voltage reference through compensation to ensure that the array continues to operate near the maximum power point.

[0052] The working principle and process are as follows: the DC output of the photovoltaic array is suppressed by the input EMI filter 2 to suppress switching harmonics and external interference, and the voltage and current signals are collected by the signal conditioning circuit and sent to the MPPT control unit 8; the MPPT (e.g. based on the incremental conductance method) calculates the real-time output power in the DSP / MCU and gives the maximum power point voltage reference value and power differentiation command (low power / high power) as the upper-level control target. The boost stage consists of at least two parallel soft-switching boost branches. Each branch includes a power switch, a resonant element (for ZVS / ZCS), a free diode, and an energy storage inductor. The outputs of all branches are connected in parallel to the DC bus 4 and the phase controller 9 causes the drive signals of each branch to be phase-shifted (interleaved) to reduce input current ripple and achieve current stress distribution. The phase controller 9 runs on a digital signal processor and calculates the phase shift and duty cycle correction of each branch based on the DC bus 4 voltage, the current of each branch, and the power region information issued by the MPPT. It uses a closed-loop algorithm (PI voltage loop + proportional resonance or PR current loop) to generate a high-resolution PWM to precisely control the turn-on / turn-off timing of the power switch. The system monitors the voltage and current waveforms of each switch in real time. If the soft-switching condition (voltage before turn-on or current threshold before turn-off) is not met, the controller selects a reference step size based on the power range and calculates the adjustment coefficient according to the degree of deviation, dynamically adjusting the phase offset to restore soft switching. At the same time, the photovoltaic operating point drift caused by phase adjustment is compensated and superimposed on the MPPT voltage reference to ensure that the array continues to operate near the maximum power point. DC bus 4 supplies the three-phase full-bridge inverter. Its AC side passes through an LCL filter 6 composed of inverter-side inductors, filter capacitors, and grid-side inductors, and is connected to the grid through isolation transformer 7. The inverter grid-connected side uses a phase-locked loop (PLL) to synchronize with the grid. The corresponding current loop uses proportional-resonant or PR control to ensure fundamental frequency tracking and low harmonic injection. Active or passive damping of LCL resonance is implemented in the controller to maintain stability. The MPPT unit and the phase controller 9 form a tightly coupled control system: the MPPT provides the power / voltage target, and the phase controller 9 tracks the maximum power point by adjusting the phase and duty cycle while ensuring soft switching and current balance, thus taking into account high efficiency, low ripple, device thermal stress dispersion and excellent grid-connected power quality.

[0053] As a preferred embodiment, the solution of this application is implemented as follows: The high-efficiency solar inverter topology based on MPPT is adopted in a large-scale grid-connected photovoltaic power station. Assuming a 100 kW photovoltaic power station consists of multiple 10 kW photovoltaic arrays, each array is connected to a multi-phase interleaved parallel soft-switching Boost circuit via an input EMI filter 2. Each Boost branch uses SiC MOSFETs as power switches, coupled with series resonant capacitors and energy storage inductors, to achieve zero-voltage switching (ZVS) to reduce switching losses and electromagnetic interference. The gate drive signal of each branch is controlled by phase-differential PWM generated by a DSP to ensure minimal input current ripple and even load distribution. When the light intensity changes, the MPPT control unit 8 collects the voltage and current of each array, calculates the maximum power point voltage using the incremental conductance method, and outputs an MPPT control signal to the phase controller 9. The phase controller 9 dynamically adjusts the phase offset and duty cycle of each branch based on the DC bus 4 voltage and the current data of each branch, ensuring that the photovoltaic array continuously operates near the maximum power point. The three-phase full-bridge inverter converts the DC bus voltage (4) to AC, suppresses high-frequency harmonics through an LCL filter (6), and connects to the grid via an isolation transformer (7). Simultaneously, the DSP monitors the voltage and current waveforms of the switching transistors in real time. When it detects that the soft-switching conditions are not met, it automatically adjusts the phase offset to restore ZVS / ZCS, ensuring efficient and stable system operation. This topology can improve overall conversion efficiency (over 98%) and reduce power switching device losses and thermal stress in actual power plants.

[0054] Through the above technical solutions, this application employs a multi-phase interleaved parallel soft-switching Boost circuit 3. By controlling the phase difference of the power switches in each branch, the input current is interleaved, reducing input current ripple. Simultaneously, it ensures that the power devices in each branch switch under zero voltage or zero current conditions, reducing switching losses and electromagnetic interference, thereby improving overall conversion efficiency and system reliability. The MPPT control unit 8 collects photovoltaic voltage and current signals in real time, accurately calculates the maximum power point voltage based on the incremental conductance method, and sends the control signal to the phase controller 9. This allows each Boost branch to dynamically adjust its phase offset and duty cycle, ensuring the photovoltaic array continuously outputs power close to its maximum power point, thus improving photovoltaic energy utilization. The three-phase full-bridge inverter circuit 5, combined with the LCL filter 6 and isolation transformer 7, not only efficiently inverts DC voltage into high-quality AC power but also suppresses high-frequency harmonic interference to the power grid, ensuring grid-connected power quality. The phase controller 9 monitors the voltage and current waveforms of the power switches in real time and automatically adjusts the drive signal when soft-switching conditions are not met, achieving protection of the power switches and improving system stability.

[0055] This application further proposes an MPPT control unit 8, configured to acquire photovoltaic voltage and photovoltaic current signals, calculate the real-time output power of the solar cell array 1, determine the maximum power point position based on the incremental conductance method, compare the real-time output power with a power threshold to determine the current power region of the solar cell array 1, which includes a low power region and a high power region, determine the maximum power point voltage reference value based on the maximum power point position, and generate a corresponding power adjustment command based on the current power region, and integrate the maximum power point voltage reference value and the power adjustment command into an MPPT control signal.

[0056] Phase controller 9 is configured to dynamically adjust the operating state of all soft-switching Boost switching branches in the multi-phase interleaved parallel soft-switching Boost circuit 3 according to the MPPT control signal output; based on the voltage data of DC bus 4 and the current data of all soft-switching Boost switching branches, it calculates the phase offset and duty cycle adjustment value of the drive signal of the power switch in each soft-switching Boost switching branch based on the closed-loop feedback control algorithm, so that the output voltage of the photovoltaic array tracks the maximum power point voltage reference value; and generates a precise PWM drive signal based on the phase offset and duty cycle adjustment value of the drive signal through a digital signal processor to control the turn-on and turn-off timing of the power switch in each soft-switching Boost switching branch.

[0057] The phase controller 9 is also configured to monitor the voltage and current waveforms of the power switching transistors in each soft-switching Boost switching branch in real time. When it is detected that the soft-switching conditions are not met, the phase offset of the drive signal is dynamically adjusted based on the power region information in the MPPT control signal to restore the soft-switching working state of the power switching transistors and maintain the tracking accuracy of the maximum power point voltage reference value.

[0058] Specifically, the MPPT control unit 8 and the phase controller 9 form a tightly coupled closed-loop control chain: the MPPT control unit 8 acquires photovoltaic voltage and current signals at a fixed sampling rate (synchronized with the PWM timer) through signal conditioning and ADC channels, and multiplies them in real time after digital filtering (such as moving average and limiting) to obtain instantaneous power and calculate average / real-time output power; based on the incremental conductance method (IncCond), the ratio of voltage ΔV to current ΔI before and after the disturbance is compared to determine the direction of the maximum power point, thereby generating a maximum power point voltage reference value Vmp_ref; at the same time, the real-time output power is compared with the preset power threshold to determine whether the current region is low power or high power, and power adjustment commands are generated accordingly (such as adjusting the number of parallel working branches or the phase reference step size), and Vmp_ref and the power adjustment commands are encapsulated into MPPT control signals and sent to the phase controller 9. The phase controller 9 runs on the DSP / MCU. First, it calculates the voltage error using Vmp_ref and the acquired DC bus 4 voltage, and generates an overall current reference value through a PI voltage loop. Then, it compares this current reference with the actual current of each branch to obtain the current error signal. The current error signal is processed by a proportional-resonant (PR) or equivalent high-gain controller to obtain the phase offset Δφ and duty cycle adjustment ΔD for each branch. The controller also performs current balancing and power density constraints (to avoid overload of a branch) based on the DC bus 4 voltage, the current of each branch, and historical status. It superimposes Δφ and ΔD with the preset phase reference and duty cycle reference to form the final drive parameters of each branch. The digital signal processor converts these parameters into a high-resolution PWM (including adjustable dead time and isolated gate drive control signal), and synchronously samples the voltage and current flowing through the switch during the PWM cycle for soft-switching detection: it checks whether the voltage across the switch is lower than the preset voltage threshold Vth (to determine ZVS) within a preset time window before turn-on, and whether the switch current is lower than the current threshold Ith (to determine ZCS) within a preset window before turn-off. If either soft-switching condition is not met, the controller selects a reference phase step size based on the current power region and calculates the adjustment coefficient according to the degree of deviation (e.g., linear or nonlinear amplification based on voltage / current deviation), obtains the actual phase offset adjustment, and recursively updates Δφ to restore the soft-switching operating state. At the same time, the controller estimates the voltage change caused by this phase adjustment to the photovoltaic array operating point and adds its negative value back to Vmp_ref as compensation to offset the impact in advance, ensuring that the array continues to operate near the maximum power point. This closed-loop process achieves a dynamic trade-off between the MPPT target and the soft-switching requirements: the MPPT provides the voltage / power target, and the phase controller 9 tracks Vmp_ref through fine adjustment of phase and duty cycle while ensuring ZVS / ZCS and current balance.

[0059] The power threshold is determined based on the rated output power characteristics of the photovoltaic array and the inverter's safe operating range. Specifically, the power threshold for the low-power region can be set as a certain percentage of the photovoltaic array's rated output power, such as 20% to 40%, to determine the operating status under conditions of insufficient sunlight, shading, or low load. The power threshold for the high-power region can be set as a higher percentage of the photovoltaic array's rated output power, such as 70% to 90%, to determine the operating status under conditions of sufficient sunlight, high load, or full power output. To avoid misjudgments due to instantaneous power fluctuations, filtering or a hysteresis range can be added to the power threshold setting to ensure stability and robustness in power judgment. When the real-time output power of solar cell array 1 is lower than the low-power threshold, the system determines it is in the low-power region; when the real-time output power is higher than the high-power threshold, the system determines it is in the high-power region; when it falls between these two thresholds, a smooth transition can be achieved using either the previous power region state maintenance method or linear interpolation, depending on the system design.

[0060] The working principle and process are as follows: The MPPT control unit 8 acquires the voltage and current signals of the photovoltaic array through the signal conditioning circuit. After digital filtering (such as moving average and amplitude limiting filtering), stable voltage and current data are obtained, and the instantaneous power is calculated to obtain the real-time output power of the solar cell array 1. Subsequently, the MPPT control unit 8 uses the incremental conductance method (IncCond) to analyze the changes in voltage ΔV and current ΔI before and after the disturbance, determines the location of the maximum power point, and generates the corresponding maximum power point voltage reference value Vmp_ref. At the same time, the real-time output power is compared with the preset power threshold to determine whether the photovoltaic array is currently in the low-power region or the high-power region, and generates power adjustment commands according to the power region, such as adjusting the number of multi-phase interleaved parallel soft-switching Boost branches or the phase difference between branches, to achieve current stress balance and power optimization. After receiving the MPPT control signal, the phase controller 9 dynamically adjusts the operating state of each soft-switching Boost switching branch through a closed-loop feedback algorithm: First, it compares Vmp_ref with the acquired DC bus 4 voltage to calculate the voltage error, and then generates a current reference value through a proportional-integral (PI) controller; subsequently, it compares the current reference value with the current data of each branch to calculate the current error signal, and calculates the phase offset and duty cycle adjustment value of each power switch through a proportional-resonant (PR) controller to precisely control the turn-on and turn-off timing of the PWM signal, so that the DC bus 4 voltage closely tracks the maximum power point voltage. During the turn-on and turn-off process of the switching transistors, the controller monitors the voltage and current waveforms of each branch power switch in real time to detect whether the zero-voltage switching (ZVS) and zero-current switching (ZCS) conditions are met; if the soft-switching conditions are not met, the phase controller 9 dynamically adjusts the phase offset of the drive signal according to the current power region and the degree of soft-switching deviation, and preemptively offsets the impact on the photovoltaic output voltage by compensating for the adjustment, restoring the soft-switching operating state.

[0061] As a preferred embodiment, the solution of this application is implemented as follows: Assuming a photovoltaic power station, the total power of the solar cell array 1 is 50kW. Changes in current solar irradiance cause the photovoltaic output power to rapidly increase from a low-power region (e.g., 10kW) to a high-power region (e.g., 45kW) in the morning. The MPPT control unit 8 first collects the voltage signal (e.g., an average of 350V per branch) and current signal (initially approximately 28A) of the photovoltaic array, calculates the instantaneous output power, and uses the incremental conductance method to analyze the changes in voltage and current, determining the maximum power point voltage reference value to be 360V. At this time, the real-time output power is less than the high-power threshold, and the control unit determines that the photovoltaic array is in a low-power region and generates corresponding power adjustment commands: reducing the number of operating Boost branches and increasing the phase difference between branches to ensure zero-voltage or zero-current switching conditions under low power. The phase controller 9 reads the DC bus 4 voltage data (approximately 355V) and the current data of each Boost branch (approximately 5A / branch) according to the MPPT control signal, and uses a closed-loop feedback algorithm to calculate the phase offset and duty cycle adjustment value of each power switch. The digital signal processor converts these parameters into precise PWM drive signals to achieve accurate turn-on and turn-off of the power switches in each branch. During the control process, the phase controller 9 monitors the voltage and current waveforms of each switch in real time. When it finds that the turn-off current of some branch switches is higher than the preset threshold and the soft-switching condition is not met, the controller dynamically adjusts the phase offset, for example, by increasing the offset by 2° to extend the turn-off time and restore the zero-current switching state. At the same time, it compensates for the maximum power point reference voltage to ensure that the photovoltaic array still stably tracks the 360V maximum power point.

[0062] Through the above technical solution, this application collects the voltage and current signals of the photovoltaic array, the control unit calculates the output power in real time, and accurately locates the maximum power point based on the incremental conductance method, thereby determining the reference value of the maximum power point voltage. Furthermore, the real-time output power is compared with a preset power threshold to distinguish whether the photovoltaic array is in a low-power or high-power region, and corresponding power adjustment commands are generated to achieve dynamic adjustment of the multi-phase interleaved parallel soft-switching Boost branches. For example, in the low-power region, the number of working branches is reduced and the phase difference between branches is increased; in the high-power region, working branches are increased and the phase difference distribution is optimized, thereby reducing the total input current ripple and maintaining soft-switching conditions. The phase controller 9, based on the DC bus 4 voltage and the current data of each branch, calculates the phase offset and duty cycle adjustment value of each power switch through a closed-loop feedback algorithm, and a precise PWM drive signal is generated by the digital signal processor, realizing precise on / off control of the switching transistors. During operation, the controller monitors the voltage and current waveforms of each switch in real time. When it detects that the soft-switching conditions are not met, it automatically adjusts the phase offset according to the power region information to restore the soft-switching state. At the same time, it compensates for the maximum power point reference voltage, ensuring that the photovoltaic array continues to work near the maximum power point.

[0063] This application further proposes that when the MPPT control unit 8 acquires photovoltaic voltage and photovoltaic current signals and calculates the real-time output power of the solar cell array 1, it includes:

[0064] The photovoltaic voltage and current signals are acquired based on the signal conditioning circuit and digitally filtered. The photovoltaic voltage and current signals after digital filtering are multiplied in real time to obtain the instantaneous power value. The instantaneous power value is used as the real-time output power. The digital filtering process includes the use of a moving average algorithm and amplitude limiting filtering.

[0065] Specifically, the MPPT control unit 8 employs an end-to-end signal chain and multi-stage filtering to balance accuracy and response speed in acquiring photovoltaic voltage and current and performing real-time power calculations. The photovoltaic voltage is first fed into the ADC channel via a precision voltage divider / isolation amplifier and an anti-aliasing analog low-pass filter (used to suppress high-frequency switching noise and satisfy the ADC sampling theorem). The photovoltaic current can be acquired through differential amplification with a high-precision shunt resistor or a Hall effect sensor, and is also sampled after isolation amplification and analog filtering. The ADC channel preferably uses simultaneous or synchronous sampling to eliminate time differences between channels. The sampling rate should be several times higher than the control PWM frequency to ensure waveform reproduction (e.g., kHz to tens of kHz levels, selected according to the system switching frequency). Sampling triggering is synchronized with the PWM timer to ensure timing consistency. The digital end first performs bias calibration and gain correction (including temperature drift compensation and sensor nonlinearity correction), and then applies digital filtering to the original voltage and current sequences: a moving average (moving window) is used for noise reduction to lower random noise, and the window length can be dynamically selected based on the trade-off between noise and response time; then, a limiting filter is applied to eliminate outliers caused by instantaneous sampling spikes or sensor saturation. The filtered voltage and current samples are multiplied point-by-point at each sampling time to obtain the instantaneous power. To obtain the real-time output power for MPPT judgment, the instantaneous power can be further processed by short-time moving average or exponentially weighted moving average (EWMA) to obtain a smooth power estimate. Downsampling / integer-cycle accumulation is performed as needed to match the MPPT algorithm's update rate (the MPPT update rate is usually lower than the sampling rate to reduce algorithm jitter). In implementation, the DSP / MCU should use fixed-point or floating-point arithmetic, paying attention to saturation and overflow protection, and recording the timestamp and sampling sequence number in each calculation for tracking and fault diagnosis.

[0066] As a preferred embodiment, the solution of this application is implemented as follows: The MPPT control unit 8 acquires the voltage and current signals at the output of the photovoltaic array in real time through a signal conditioning circuit. The voltage signal, after precise voltage division and isolation amplification, is then filtered by an anti-aliasing low-pass filter to suppress high-frequency switching noise before being sampled by a high-speed ADC channel. The current signal, through a shunt resistor, generates a small voltage drop, which is then differentially amplified and isolated before being sampled and fed into the ADC. The sampled voltage and current data undergo digital filtering in the digital processing unit: a moving average algorithm is used to smooth random noise, while a limiting filter is used to remove occasional sampling spikes or abnormal peaks. The filtered voltage and current signals are multiplied point-by-point at each sampling moment to obtain the instantaneous power value; for example, at a sampling frequency of 20kHz, the instantaneous power value is calculated for each sampling point. The instantaneous power value is then subjected to short-time averaging to obtain a smoother real-time output power, which is used by the MPPT algorithm to determine the location of the maximum power point. In actual testing, when the sunlight gradually decreases from full sunlight to partial shade covering the photovoltaic module, digital filtering and limiting processing can suppress the interference of instantaneous voltage drops and current spikes on power calculation, enabling the control unit to still accurately output stable real-time power.

[0067] Through the above technical solutions, this application employs signal conditioning circuits and digital filtering processing. The MPPT control unit 8 can accurately acquire the voltage and current signals of the photovoltaic array, suppressing the interference of light changes, temperature fluctuations, and switching noise on the measurement signals. It uses a moving average algorithm to smooth random fluctuations, and at the same time, it uses amplitude limiting filtering to remove abnormal peaks or transient disturbances, ensuring the stability and reliability of the signal. The voltage and current signals after filtering are multiplied in real time to calculate the instantaneous power value, which can accurately reflect the actual output power of the photovoltaic array, ensuring that the MPPT algorithm obtains accurate power information.

[0068] This application further proposes that when the MPPT control unit 8 determines the location of the maximum power point based on the incremental conductance method, it includes:

[0069] Apply a voltage disturbance to the current operating point and measure the voltage and current changes before and after the disturbance. Calculate the ratio of the conductance increment to the instantaneous conductance. When the ratio is greater than zero, adjust the operating point in the direction of increasing voltage. When the ratio is less than zero, adjust the operating point in the direction of decreasing voltage. When the ratio is equal to zero, determine that the maximum power point has been reached.

[0070] Specifically, the MPPT unit based on the incremental conductance method operates according to an engineered process to accurately locate and maintain the maximum power point: the control unit acquires filtered photovoltaic voltage and current samples at a fixed sampling frequency synchronized with the PWM, and calculates the voltage and current increments of adjacent samples to determine the power change trend. If the judgment result indicates that there is still room for improvement at the current point, the controller applies a preset disturbance step size in the direction of voltage increase or decrease to move the operating point; when the judgment is close to the maximum power point, the disturbance step size is automatically reduced to reduce steady-state oscillations, thereby achieving a balance between convergence speed and steady-state accuracy. To improve noise robustness, the system performs short-time averaging of the sampling sequence before judgment and sets a dead-zone threshold to avoid frequent adjustments due to small sampling fluctuations; after applying the disturbance, the controller waits for a stable window that matches the circuit response time before resampling and judging, preventing misjudgment during filter or converter transients. To address rapid illumination changes, the algorithm includes a fast relocation mode: when a power surge exceeding the normal disturbance range is detected, the MPPT shortens the waiting time, increases the step size, and raises the update frequency to quickly relock the maximum power point; once the environment stabilizes, it returns to fine-grained search. The MPPT and phase controller 9 work collaboratively through a clearly defined interface—the MPPT only issues maximum power point voltage reference and power region commands, with a real-time update rate lower than the PWM frequency of the phase controller 9 to avoid mutual interference; upon receiving a new reference, the phase controller 9 smoothly adjusts the duty cycle and phase while maintaining soft switching and current balance constraints.

[0071] As a preferred embodiment, the solution of this application is implemented as follows: For example, in a photovoltaic system, the controller first collects the current voltage of solar cell array 1 as 320 volts and the current as 5 amps, and calculates the output power at this time. The controller slightly increases the voltage, for example, by 2 volts to 322 volts, and resamples the voltage and current within a short period of time. It is found that the current changes to 4.95 amps, and the power increases slightly, indicating that increasing the voltage can improve the output power. Therefore, the controller continues to increase the voltage in small steps, gradually approaching the maximum power point. When the controller finds that further increasing the voltage causes the current to drop significantly and the output power no longer increases, the system determines that it has approached the maximum power point, and thus stabilizes the voltage at about 325 volts to ensure that the photovoltaic array continues to output maximum power under the current illumination conditions.

[0072] Through the above technical solution, this application applies a small voltage disturbance at the operating point and monitors voltage and current changes in real time. The control unit can quickly determine whether the photovoltaic array is currently near its maximum power point, thereby intelligently adjusting the voltage operating point. This ensures that the photovoltaic array can output near-maximum power under different light conditions and temperature variations. It requires no complex preset parameters or external reference signals, has a fast response speed, reduces power fluctuations, improves system stability and reliability, reduces energy waste, and extends the service life of the photovoltaic inverter and related power devices.

[0073] This application further proposes that when the phase controller 9 dynamically adjusts the operating state of all soft-switching Boost switching branches in the multi-phase interleaved parallel soft-switching Boost circuit 3 according to the MPPT control signal output, it includes:

[0074] When the power regulation command indicates a low-power region, the number of operating soft-switching Boost converter branches is reduced, the phase difference between operating branches is increased, and the power switches of each soft-switching Boost converter branch are ensured to achieve zero-voltage or zero-current switching under low-power conditions. When the power regulation command indicates a high-power region, the number of operating soft-switching Boost converter branches is increased, the phase difference between operating branches is decreased, the total input current ripple is reduced, and the power switches of all operating branches are ensured to maintain soft-switching conditions. The number of operating soft-switching Boost converter branches is adjusted based on the balanced distribution of current stress in each soft-switching Boost converter branch and the fact that the power density of each soft-switching Boost converter branch is less than the safe operating area limit.

[0075] Specifically, when the phase controller 9 dynamically adjusts the operating state of the multi-phase interleaved parallel soft-switching Boost branch according to the MPPT control signal, the specific implementation logic includes closed-loop coordinated control of branch switching, phase allocation, duty cycle correction, and soft-switching protection. First, the controller reads the power region command (low power / high power) sent by the MPPT and collects real-time quantities such as the DC bus 4 voltage, the current of each branch, and the waveforms at both ends of the switch. In the low power region, the controller orderly reduces the parallel working branches according to the pre-set switching strategy (e.g., from N branches to M branches). However, before each branch is removed or restored, the duty cycle is smoothly adjusted and the switching is performed step by step according to the time window to avoid sudden changes that could cause bus or instantaneous current surges. At the same time, the phase difference of the remaining working branches is increased (an offset can be added on the basis of a phase difference of ≈360° / M) to extend the gap between each branch and maintain the zero-voltage or zero-current switching condition of a single branch under low load (by extending the commutation interval, fine-tuning the dead time, and the phase of the resonant element). In the high-power region, the controller adds the number of operating branches as needed and sequentially, gradually reducing the phase difference between branches to make the input current more evenly distributed over time, thereby reducing the total input current ripple and dispersing the current stress of each device. When adding branches, the controller simultaneously fine-tunes the duty cycle and phase of each branch to ensure that all connected branches can meet the soft-switching conditions and avoid short-term overcurrent. Branch selection and phase adjustment are based on real-time current stress and power density constraints. The controller continuously compares the current of each branch with the set safety threshold and temperature / thermal model data. If a branch is close to the power density limit, it is preferentially shut down or reduced in load, and more energy is allocated to the remaining branches with higher safety margins through phase fine-tuning. Soft-switching is ensured by online detection of the voltage before turn-on and the current threshold before turn-off. If the ZVS / ZCS conditions are not met, the controller selects an appropriate reference phase step size according to the current power range and amplifies or reduces the adjustment coefficient according to the degree of deviation, modifying the phase offset and duty cycle in real time until soft switching is restored. At the same time, the photovoltaic operating point drift caused by phase correction is added back to the MPPT voltage reference with compensation to maintain tracking accuracy. To avoid oscillation control, the entire switching and phase adjustment process employs stepped or proportional rate limiting (with hysteresis and steady-state dead time) and is executed synchronously with the PWM timer. The high-speed DSP is responsible for calculating and generating high-resolution PWM, dead-time control, and gate drive protection. The overall goal is to minimize input current ripple, minimize switching losses, and balance device stress within different power ranges through adaptive branch management and fine phase / duty cycle adjustment.

[0076] The safe operating area limits are set based on the rated current, voltage, and thermal characteristics of the power switches and related components in the soft-switching Boost converter branches, while also considering the system's long-term reliability and transient overload capacity. Specifically, the current density and power density of each branch should not exceed the maximum allowable values ​​provided by the device manufacturer to avoid overheating, device aging, or damage. When setting limits, factors such as heat dissipation, ambient temperature, long-term operating safety margin, and the impact of input voltage fluctuations on branch power must also be considered. In practical applications, the heat loss of the power switches under different load conditions can be calculated based on their rated power and on-resistance, with a safety margin of approximately 10% to 20% as the limit. Furthermore, for multi-phase interleaved parallel structures, it is necessary to ensure a balanced power distribution among the branches to prevent overload operation of any single branch. Through this limit setting, the number and phase distribution of operating branches can be dynamically adjusted under low-power and high-power operating conditions to ensure that all soft-switching Boost converter branches operate within the safe operating area while maintaining soft-switching conditions.

[0077] As a preferred embodiment, the solution of this application is implemented as follows: In practical applications, when the photovoltaic array is in a cloudy day or under low illumination conditions in the early morning or late evening, the MPPT control unit 8 detects that the solar output power is in a low power region. The phase controller 9 will reduce the number of working multi-phase interleaved parallel soft-switching Boost branches. For example, only three branches are kept in operation out of the original six branches. At the same time, by adjusting the phase difference between each working branch, the conduction time of adjacent branches is staggered, and the switching interval is extended, thereby ensuring that the power switching tube of each branch can achieve zero voltage or zero current switching under low current conditions, reducing switching losses and preventing device overheating. Meanwhile, the controller monitors the current stress and power density of each branch in real time to ensure that the retained working branches do not exceed the safe operating limits. Conversely, when the photovoltaic array is under high illuminance conditions at midday or on a sunny day, and the output power enters the high-power region, the controller increases the number of operating boost branches, for example, all six branches operate simultaneously, and reduces the phase difference between branches to ensure a more uniform distribution of the input current over time, reducing the total current ripple. Simultaneously, by fine-tuning the duty cycle and phase, it ensures that the power switches in each branch still meet the soft-switching conditions, guaranteeing efficiency and device safety during high-power output. Throughout this process, the phase controller 9 dynamically adjusts the phase offset and duty cycle by real-time acquisition of the current and voltage waveforms of each branch to adapt to power changes, thus ensuring maximum power point tracking accuracy.

[0078] Through the above technical solutions, when the photovoltaic array output power is in the low-power region, by reducing the number of working branches and increasing the phase difference between branches, this application not only reduces the conduction frequency and switching losses of the switching devices, but also ensures that the power switching transistors of each working branch can achieve zero-voltage or zero-current switching, extending the service life of the devices and reducing the overall energy consumption of the system. When the photovoltaic array output power is in the high-power region, by increasing the number of working branches and reducing the phase difference, the input current is evenly distributed among the branches, reducing the total current ripple, improving the output power quality, and maintaining the soft-switching state of all power switching transistors, thereby improving the overall system efficiency.

[0079] This application further proposes that when the phase controller 9 generates a precise PWM drive signal based on the calculated drive signal phase offset and duty cycle adjustment value by a digital signal processor, and controls the turn-on and turn-off timing of the power switching transistors in each soft-switching Boost conversion branch, it includes:

[0080] The maximum power point voltage reference value is compared with the acquired photovoltaic voltage signal to calculate the voltage error signal; the voltage error signal is input into the proportional-integral controller to generate the current reference value; the proportional-integral controller contains a proportional term and an integral term. The proportional term generates a control action based on the instantaneous value of the voltage error signal, and the integral term accumulates the voltage error signal.

[0081] The current reference value is compared with the current data of all soft-switching Boost switching branches to calculate the current error signal; the current error signal is input to the proportional resonant controller to calculate the phase offset and duty cycle adjustment value of the generated drive signal.

[0082] A proportional resonant controller consists of a proportional term and a resonant term. The proportional term provides system damping and accelerates dynamic response, while the resonant term provides high gain characteristics at the fundamental frequency, enabling zero steady-state error tracking of a sinusoidal reference signal.

[0083] The phase offset is used to adjust the phase relationship between the drive signals of the power switches in each branch, and the duty cycle adjustment value is used to adjust the conduction time of the power switches in each branch.

[0084] Specifically, the phase controller 9, through a digital signal processor (DSP), precisely generates PWM drive signals for each soft-switching Boost switching branch based on the calculated drive signal phase offset and duty cycle adjustment value, thereby controlling the turn-on and turn-off timing of the power switches. During operation, the real-time voltage signal of the photovoltaic array is compared with the maximum power point voltage reference value to obtain a voltage error signal. This error signal is input to a proportional-integral (PI) controller to generate a current reference value. The proportional term provides immediate control based on the instantaneous voltage error, while the integral term accumulates and corrects the error to eliminate steady-state deviation. This current reference value is then compared with the actual current of each soft-switching Boost switching branch to generate a current error signal, which is input to a proportional-resonant (PR) controller. The PR controller provides system damping and fast dynamic response through the proportional term, while providing high gain at the fundamental frequency through the resonant term, achieving zero steady-state error tracking of the sinusoidal reference signal, thus ensuring that the output current accurately matches the reference value. The phase offset output by the controller is used to adjust the phase of the drive signal between the power switches in each branch, so that the branches work alternately and the input current ripple is reduced; the duty cycle adjustment value adjusts the conduction time of the power switches, so as to achieve fine adjustment of the output voltage and tracking of the maximum power point voltage.

[0085] As a preferred embodiment, the solution of this application is implemented as follows: For example, in a grid-connected photovoltaic inverter system, the MPPT control unit 8 first compares the real-time output voltage of the photovoltaic array with the maximum power point voltage reference value to generate a voltage error signal. This error signal is input to a proportional-integral (PI) controller, where the proportional term responds quickly to instantaneous voltage deviations, and the integral term accumulates historical errors to ensure long-term system stability and eliminate steady-state deviations, thereby generating a corresponding current reference value. Subsequently, the system compares this current reference value with the actual current of each soft-switching Boost switching branch, calculates the current error signal, and inputs it to a proportional-resonant (PR) controller. The PR controller provides necessary damping and accelerates dynamic response through the proportional term, while the resonant term provides high gain at the grid fundamental frequency, achieving zero steady-state error tracking of the ideal sinusoidal current reference signal. The phase offset output by the controller is used to adjust the conduction timing between the power switches of each branch, so that each branch operates alternately to reduce input current ripple; the duty cycle adjustment value precisely adjusts the conduction time of the switches to achieve close tracking of the output voltage to the maximum power point reference value. In actual operation, such as when the light intensity changes rapidly at noon on a sunny day, the control mechanism can adjust the working status of each branch in real time to ensure that the output power of the photovoltaic array remains close to the maximum power point, while the power switching tubes of each branch remain in a soft-switching state.

[0086] Through the above technical solution, this application generates a voltage error signal by comparing the maximum power point voltage reference value with the real-time acquired photovoltaic voltage signal, and converts it into a precise current reference value through a proportional-integral controller, which can respond instantly to photovoltaic output fluctuations caused by changes in light intensity or ambient temperature; the current error signal is input to a proportional-resonant controller, which precisely adjusts the turn-on and turn-off timing of the power switching transistors in each soft-switching Boost conversion branch through phase offset and duty cycle adjustment, thereby realizing the interleaved soft-switching operation of each branch, thus reducing switching losses and input current ripple.

[0087] This application further proposes that when the phase controller 9 generates a precise PWM drive signal based on the calculated drive signal phase offset and duty cycle adjustment value by a digital signal processor, and controls the turn-on and turn-off timing of the power switching transistors in each soft-switching Boost conversion branch, it includes:

[0088] The phase offset and duty cycle adjustment values ​​are superimposed with the preset phase reference signal and duty cycle reference signal to generate the final drive signal parameters of the power switching transistors in each soft-switching Boost conversion branch. The final drive signal parameters are converted into precise PWM drive signals by a digital signal processor to control the turn-on and turn-off timing of the power switching transistors in each soft-switching Boost conversion branch.

[0089] Specifically, the phase controller 9 utilizes a digital signal processor (DSP) to precisely control the power switches in each soft-switching Boost conversion branch. Based on the drive signal phase offset and duty cycle adjustment values ​​calculated by the preceding closed-loop control, these are superimposed with pre-set phase and duty cycle reference signals to generate the final drive signal parameters for each branch's power switches. This superposition process not only incorporates the system's dynamic adjustment requirements but also preserves the stability of the reference signals, enabling the final output to adapt to changes in photovoltaic array power and external load fluctuations. The DSP converts these final drive signal parameters into high-precision PWM waveform signals, achieving precise on / off switching of the power switches through high-speed timing control. This control method ensures soft-switching operation in interleaved mode for each branch, reducing switching losses and electromagnetic interference, while optimizing input current ripple and improving the overall inverter conversion efficiency and dynamic response capability.

[0090] The setting of the phase reference signal and duty cycle reference signal is based on the topology of the soft-switching Boost circuit, the input voltage range, the output voltage requirements, and the optimization design principles of multi-phase interleaved parallel branches. Specifically, the phase reference signal is used to determine the initial phase distribution between the power switches of each branch, so as to achieve current interleaving between branches, reduce the total input current ripple, and ensure the current balance of each branch under different power loads. Generally, the more branches there are, the smaller the reference phase difference between each phase, in order to optimize the current distribution and reduce electromagnetic interference. The duty cycle reference signal is used to determine the initial conduction time of each power switch, ensuring that the Boost circuit can boost the output voltage of the photovoltaic array to the target DC bus voltage in a steady state, while maintaining soft-switching conditions and reducing switching losses. The setting of the reference signal is optimized in combination with the actual device switching speed, on-resistance, and load capacity, and provides a reference for subsequent phase offset and duty cycle fine-tuning. This allows the system to achieve precise PWM drive by superimposing adjustment amounts under dynamic load and power change conditions, thereby ensuring the efficient turn-on and turn-off of the power switches of each branch.

[0091] As a preferred embodiment, the solution of this application is implemented as follows: In practical applications, such as in a photovoltaic inverter system, the phase controller 9 receives the phase offset and duty cycle adjustment value of the drive signal for each soft-switching Boost branch calculated by the closed-loop control algorithm through a digital signal processor. These dynamically adjusted parameters are then superimposed with the system's preset phase reference signal and duty cycle reference signal. The final drive signal parameters generated after superposition are converted into high-precision PWM waveform signals by the digital signal processor. Each PWM signal precisely controls the turn-on and turn-off timing of the corresponding power switch. For example, when the output power of the photovoltaic array suddenly increases, the system automatically adjusts the duty cycle of each branch's power switch to quickly track the maximum power point. Simultaneously, by adjusting the phase offset, the total input current ripple is reduced, ensuring that the soft-switching conditions are maintained even in the interleaved operation mode of each branch, thereby minimizing switching losses and heat generation.

[0092] Through the above technical solution, the phase controller 9 of this application can achieve precise timing control of each power switch in the multi-phase interleaved parallel soft-switching Boost converter branch, ensuring that it remains in a soft-switching state during conduction and turn-off, thereby reducing switching losses and heat generation and improving the overall system efficiency. By superimposing the calculated phase offset and duty cycle adjustment values ​​with a preset reference signal to generate the final drive parameters, it can dynamically adapt to rapid changes in the output power of the photovoltaic array, ensuring the stability of the DC bus 4 voltage and tracking the maximum power point voltage reference value.

[0093] This application further proposes that when the soft-switching condition is not met, the phase controller 9 dynamically adjusts the phase offset of the drive signal based on the power region information in the MPPT control signal, including:

[0094] Within a preset time window before the power switch is turned on, it is detected whether the voltage across the power switch is lower than a preset voltage threshold. If the voltage before turn-on is lower than the preset voltage threshold, the zero-voltage switching condition is met. Within a preset time window before the power switch is turned off, it is detected whether the current flowing through the power switch is lower than a preset current threshold. If the current before turn-off is lower than the preset current threshold, the zero-current switching condition is met. If the voltage across the power switch is not lower than the preset voltage threshold before turn-on, or the current flowing through the power switch is not lower than the preset current threshold before turn-off, the soft-switching condition is not met.

[0095] When the soft-switching condition is not met, the reference step size for phase offset adjustment is determined based on the current power region; the adjustment coefficient is calculated based on the degree of deviation from the soft-switching condition; and the actual phase offset adjustment is obtained by multiplying the reference step size by the adjustment coefficient.

[0096] Specifically, when the soft-switching condition is not met, the phase controller 9 dynamically adjusts the phase offset of the drive signal of the power switch in each soft-switching Boost conversion branch based on the power region information provided in the MPPT control signal. Within a preset time window before the power switch is turned on, the phase controller 9 continuously monitors the voltage across its terminals and compares it with a preset voltage threshold. If the voltage across the terminals is lower than the set threshold before turn-on, the current switch is deemed to meet the zero-voltage switching condition; otherwise, it is considered that there is still residual voltage before turn-on, and phase adjustment is required. Within a preset time window before the power switch is turned off, the phase controller 9 simultaneously monitors the current flowing through the switch and compares it with a preset current threshold to determine if the zero-current switching condition is met. If the current is still higher than the threshold before turn-off, it indicates that the switch has not yet completed zero-current switching, and phase adjustment is also required to ensure soft switching is achieved. When the phase controller 9 determines that the soft-switching condition of a certain branch is not met, it selects the corresponding phase offset adjustment reference step size according to the current power region of the photovoltaic array. Different step sizes are used for low-power and high-power regions to adapt to differences in current load and voltage variations. Phase controller 9 calculates the corresponding adjustment coefficient by evaluating the actual detected voltage and current deviations to accurately correct the deviation. The reference step size is multiplied by the adjustment coefficient to obtain the actual phase offset adjustment, which is then applied to the PWM drive signals of each soft-switching Boost switching branch. This dynamic adjustment process ensures that each power switch maintains zero voltage or zero current conditions as much as possible during turn-on and turn-off, thereby reducing switching losses, improving system efficiency, ensuring stable DC bus 4 voltage, and optimizing the overall performance and operational reliability of the photovoltaic inverter under different power output conditions.

[0097] The preset time window before the power switch turns on, the preset voltage threshold, the preset time window before the power switch turns off, and the preset current threshold are all optimized based on the physical characteristics of the power switch, the system operating frequency, and the dynamic response requirements of the soft-switching Boost circuit. The preset time window before turn-on should sufficiently cover the time it takes for the voltage to drop to near zero before the power switch turns on, ensuring that the zero-voltage switching condition can be reliably detected. This time window is generally taken as the typical delay time of the switch's rising edge plus a safety margin. The preset voltage threshold is set based on the switch's withstand voltage and the allowable voltage fluctuation range for soft switching, and is usually slightly higher than the theoretical zero voltage point to prevent misjudgment. The preset time window before turn-off should cover the time it takes for the current flowing through the switch to drop to near zero before the switch turns off, to meet the zero-current switching condition. This time window is usually set based on the switch's turn-off characteristics, the inductor's energy storage release time, and the system response delay. The preset current threshold is determined based on the accuracy of the current sensor and the maximum allowable conduction current of the switch, and is generally slightly higher than the ideal zero current value to ensure safety and reliability.

[0098] As a preferred embodiment, the solution of this application is implemented as follows: When the power switch of a certain soft-switching Boost conversion branch detects that the soft-switching condition is not met during the operation of the inverter, for example, when the sunlight is strong and the output power of the photovoltaic array is high, the voltage across the power switch fails to drop to the preset voltage threshold before the power switch is turned on, or the current flowing through the switch is still higher than the set current threshold before the switch is turned off, the phase controller 9 will immediately start the dynamic adjustment mechanism. Specifically, the phase controller 9 first continuously samples the voltage across the power switch within a short time window before the power switch is turned on and compares it with the preset voltage threshold. If the voltage is still higher than the threshold before the power switch is turned on, it is determined that the zero-voltage switching condition is not met. At the same time, within a short time window before the power switch is turned off, the controller samples the switch current and compares it with the preset current threshold. If the current does not drop below the threshold before the power switch is turned off, it is determined that the zero-current switching condition is not met, thereby confirming that the soft-switching condition of the branch has failed. After confirming that the soft-switching conditions are not met, the controller selects an appropriate phase offset reference step size based on the current power region of the photovoltaic array. For example, a smaller step size is selected in the high-power region to avoid current surges caused by large adjustments, while a larger step size is selected in the low-power region to quickly restore the soft-switching state. Subsequently, the phase controller 9 evaluates the degree to which the pre-turn-on voltage and pre-turn-off current deviate from the threshold, calculates the specific adjustment coefficient, and multiplies this coefficient by the reference step size to obtain the actual phase offset adjustment value. The digital signal processor updates the PWM drive signal based on the calculation results, dynamically correcting the turn-on and turn-off timing of the power switches, thereby restoring the zero-voltage or zero-current switching state.

[0099] Through the above technical solution, the controller of this application continuously collects the voltage across the power switch within a preset time window before the power switch is turned on. If the detected voltage is lower than a preset threshold, it is determined that the zero-voltage switching condition is met. Within a preset time window before the power switch is turned off, the controller collects the current flowing through the power switch. If the current is lower than a preset threshold, it is determined that the zero-current switching condition is met. When the voltage before turn-on is higher than the threshold or the current before turn-off is higher than the threshold, the system determines that the soft-switching condition is not met. The controller determines the reference step size for phase offset adjustment based on the current photovoltaic power region. A smaller step size is used in the high-power region to reduce current surges, and a larger step size is used in the low-power region to accelerate the soft-switching recovery speed. An adjustment coefficient is calculated based on the degree of deviation. The reference step size is multiplied by the adjustment coefficient to generate the actual phase offset adjustment amount, which is then applied to the PWM drive signal to control the turn-on and turn-off sequence of each power switch.

[0100] This application further proposes that when the phase controller 9 restores the soft-switching operation of the power switch to maintain the tracking accuracy of the maximum power point voltage reference value, it includes:

[0101] The change in output voltage of the photovoltaic array is calculated based on the phase offset adjustment; the negative value of the voltage change is superimposed on the maximum power point voltage reference value as a compensation; the impact of the phase offset adjustment on the operating point of the photovoltaic array is offset in advance, ensuring that the photovoltaic array continues to work near the maximum power point.

[0102] Specifically, when the phase controller 9 restores the soft-switching operation of the power switches and maintains accurate tracking of the photovoltaic array to the maximum power point voltage reference value, the system first calculates the change in the output voltage of the photovoltaic array based on the aforementioned phase offset adjustment. This change reflects the actual impact of the voltage offset caused by the phase adjustment of the PWM drive signal on the operating point of the photovoltaic array. To ensure that the photovoltaic array can continuously and stably operate near the maximum power point, the controller takes a negative value for the calculated voltage change to form a compensation amount, and adds this compensation amount to the maximum power point voltage reference value in real time, thereby dynamically correcting the original reference value. In this way, even when the conduction timing of each branch in the multi-phase interleaved parallel soft-switching Boost circuit 3 is adjusted to restore the soft-switching state, the output voltage of the photovoltaic array can still closely follow the maximum power point voltage, achieving power tracking without steady-state error. In the specific operation, the digital signal processor continuously collects the voltage and current data of the photovoltaic array, compares the real-time measured values ​​with the corrected reference values, and continuously updates the duty cycle and phase of the PWM drive signal through closed-loop feedback, so that the conduction and turn-off of each power switch precisely match the adjusted operating point.

[0103] As a preferred embodiment, the solution of this application is implemented as follows: In practical applications, when the phase controller 9 detects that the power switch of a certain soft-switching Boost conversion branch is about to deviate from the soft-switching state, it first calculates the change in the photovoltaic array output voltage caused by the phase offset adjustment of that branch. For example, if the phase offset of a certain power switch is adjusted to restore zero voltage or zero current switching, its early or delayed conduction will cause the voltage output contributed by that branch to shift positively or negatively. Assume the calculated voltage change is +2 volts. The controller will take the negative value of this voltage change to form a compensation amount, i.e., -2 volts, and add it to the originally set maximum power point voltage reference value, thereby adjusting the reference value from the assumed 320 volts to 318 volts. This adjustment will offset the impact of voltage fluctuations caused by phase offset on the overall operating point of the photovoltaic array in advance, so that the array can still remain close to the maximum power point throughout the adjustment process. Meanwhile, the digital signal processor continuously collects the array voltage and the current of each branch, and updates the duty cycle and phase of the PWM signal in real time through closed-loop feedback to ensure that the turn-on and turn-off of each power switch are precisely matched with the corrected reference voltage. In actual testing, even under high load conditions or when power fluctuates rapidly due to changes in illumination, the output voltage of the photovoltaic array can still stably track the maximum power point within a range of approximately ±0.5 volts, ensuring maximum system output power while avoiding overvoltage or overcurrent losses in the switching transistors.

[0104] Through the above technical solution, this application calculates the output voltage change of the photovoltaic array based on the phase offset adjustment. The controller can accurately predict the operating point offset caused by soft switching adjustment and superimpose the negative value of the voltage change as a compensation amount onto the maximum power point voltage reference value, thus achieving active correction of the array's operating point. This compensation mechanism can offset the voltage fluctuations caused by phase adjustment in advance, enabling the photovoltaic array to operate stably near the maximum power point and avoiding power loss caused by transient voltage changes when the switch is turned on or off.

[0105] Based on the other preferred method described above, see [link / reference]. Figure 2 As shown, this embodiment provides a high-efficiency solar inverter topology control method based on MPPT, used to apply the above-mentioned high-efficiency solar inverter topology based on MPPT, including:

[0106] Photovoltaic voltage and current signals are acquired to calculate the real-time output power of the solar cell array. The location of the maximum power point (MPPT) is determined based on the incremental conductance method. The real-time output power is compared with a power threshold to determine the current power region of the solar cell array, which includes low-power and high-power regions. The reference value of the maximum power point voltage is determined based on the location of the MPPT, and a corresponding power adjustment command is generated based on the current power region. The reference value of the MPPT voltage and the power adjustment command are integrated into an MPPT control signal.

[0107] The operating state of all soft-switching Boost switching branches in the multi-phase interleaved parallel soft-switching Boost circuit is dynamically adjusted based on the MPPT control signal output. Based on the DC bus voltage data and the current data of all soft-switching Boost switching branches, the phase offset and duty cycle adjustment value of the drive signal for the power switching transistors in each soft-switching Boost switching branch are calculated using a closed-loop feedback control algorithm, ensuring that the photovoltaic array output voltage tracks the maximum power point voltage reference value. A precise PWM drive signal is generated by a digital signal processor based on the phase offset and duty cycle adjustment value of the drive signal to control the turn-on and turn-off timing of the power switching transistors in each soft-switching Boost switching branch.

[0108] The voltage and current waveforms of the power switching transistors in each soft-switching Boost conversion branch are monitored in real time. When the soft-switching condition is not met, the phase offset of the drive signal is dynamically adjusted based on the power region information in the MPPT control signal to restore the soft-switching working state of the power switching transistors and maintain the tracking accuracy of the maximum power point voltage reference value.

[0109] In summary, the multi-phase interleaved parallel soft-switching Boost circuit structure distributes the input current through phase shifting, reducing current ripple and inductor current stress. Simultaneously, resonant elements enable zero-voltage or zero-current soft switching of the power switches, reducing switching losses and electromagnetic interference, and improving overall energy conversion efficiency. The MPPT control unit calculates the power change trend of the photovoltaic array in real time based on the incremental conductance method. Through power region determination and dynamic voltage disturbance, it achieves adaptive adjustment, maintaining the solar cell array near its maximum power point even under rapid changes in illumination or temperature, thereby increasing the output power of the photovoltaic power generation system. The phase controller dynamically adjusts the number of parallel branches and phase difference distribution according to the MPPT control signal, reducing the number of working branches in the low-power region and increasing the number of working branches in the high-power region. This achieves balanced current stress distribution and adaptive control of branch power density, reducing device losses and thermal stress, and improving system stability and lifespan. By combining a proportional-integral controller (PIC) with a proportional-resonant controller, the phase offset and duty cycle adjustment values ​​can be accurately calculated under dual closed-loop voltage and current conditions, enabling the PWM drive signal to have a fast dynamic response capability. When the soft-switching condition is not met, the controller can dynamically correct the phase offset based on power region information, achieving rapid recovery of the soft-switching condition and maintaining stable operation of the system in the high-efficiency range. By calculating the drive signal parameters in real time and performing dynamic compensation through a digital signal processor, the impact of phase adjustment on the photovoltaic array voltage can be offset in advance, allowing the system to maintain stable tracking of the maximum power point under load fluctuations or external disturbances, exhibiting excellent anti-disturbance performance.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A high-efficiency solar inverter topology based on MPPT, characterized in that, include: The output of the solar cell array is connected to an input EMI filter, a multi-phase interleaved parallel soft-switching Boost circuit, and a three-phase full-bridge inverter circuit. The multiphase interleaved parallel soft-switching Boost circuit includes at least two parallel soft-switching Boost conversion branches. Each soft-switching Boost conversion branch includes a power switch, a resonant element, a diode, and an energy storage inductor. The input terminal of each soft-switching Boost conversion branch is connected to the output terminal of the input EMI filter, and the output terminal of each soft-switching Boost conversion branch is connected to the DC bus. The power switch driving signals in each soft-switching Boost conversion branch are phase-differentiated, forming an interleaved operating mode. The DC side of the three-phase full-bridge inverter circuit is connected to the DC bus, and the AC side is connected to an LCL filter and an isolation transformer. The LCL filter includes an inverter-side inductor, a filter capacitor, and a grid-side inductor. The inverter-side inductor is connected to the AC output terminal of the three-phase full-bridge inverter circuit. One end of the filter capacitor is connected to the inverter-side inductor, and the other end is grounded. The grid-side inductor is connected to the filter capacitor and the isolation transformer. It also includes an MPPT control unit and a phase controller. The MPPT control unit is located between the output of the solar cell array and the input EMI filter. The phase controller is used to generate drive signals for each power switch in each soft-switching Boost conversion branch.

2. The high-efficiency solar inverter topology based on MPPT according to claim 1, characterized in that, include: The MPPT control unit is configured to acquire photovoltaic voltage and photovoltaic current signals, calculate the real-time output power of the solar cell array, determine the maximum power point (MPPT) location based on the incremental conductance method, compare the real-time output power with a power threshold to determine the current power region of the solar cell array, which includes a low-power region and a high-power region, determine the maximum power point voltage reference value based on the MPPT location, and generate a corresponding power adjustment command based on the current power region, and integrate the maximum power point voltage reference value and the power adjustment command into an MPPT control signal. The phase controller is configured to dynamically adjust the operating state of all soft-switching Boost switching branches in the multi-phase interleaved parallel soft-switching Boost circuit according to the MPPT control signal output; and to calculate the phase offset and duty cycle adjustment value of the drive signal of the power switch in each soft-switching Boost switching branch based on the DC bus voltage data and the current data of all soft-switching Boost switching branches, so as to make the photovoltaic array output voltage track the maximum power point voltage reference value. A precise PWM drive signal is generated by a digital signal processor based on the phase offset and duty cycle adjustment value of the drive signal, which controls the turn-on and turn-off timing of the power switching transistors in each soft-switching Boost conversion branch. The phase controller is also configured to monitor the voltage and current waveforms of the power switching transistors in each soft-switching Boost conversion branch in real time. When the soft-switching condition is not met, the phase offset of the drive signal is dynamically adjusted based on the power region information in the MPPT control signal to restore the soft-switching working state of the power switching transistors and maintain the tracking accuracy of the maximum power point voltage reference value.

3. The high-efficiency solar inverter topology based on MPPT according to claim 2, characterized in that, When the MPPT control unit acquires photovoltaic voltage and current signals and calculates the real-time output power of the solar cell array, it includes: The photovoltaic voltage signal and photovoltaic current signal are acquired based on the signal conditioning circuit and digitally filtered; the photovoltaic voltage signal and photovoltaic current signal after digital filtering are multiplied in real time to obtain the instantaneous power value; the instantaneous power value is used as the real-time output power; the digital filtering includes the use of a moving average algorithm and amplitude limiting filtering.

4. The high-efficiency solar inverter topology based on MPPT according to claim 3, characterized in that, When the MPPT control unit determines the location of the maximum power point based on the incremental conductance method, it includes: Apply a voltage disturbance to the current operating point and measure the voltage and current changes before and after the disturbance. Calculate the ratio of the conductance increment to the instantaneous conductance. When the ratio is greater than zero, adjust the operating point in the direction of increasing voltage. When the ratio is less than zero, adjust the operating point in the direction of decreasing voltage. When the ratio is equal to zero, determine that the maximum power point has been reached.

5. The high-efficiency solar inverter topology based on MPPT according to claim 4, characterized in that, When the phase controller dynamically adjusts the operating state of all soft-switching Boost switching branches in the multi-phase interleaved parallel soft-switching Boost circuit according to the MPPT control signal output, it includes: When the power adjustment command indicates a low-power region, the number of operating soft-switching Boost conversion branches is reduced, the phase difference between operating branches is increased, and the power switching transistors of each soft-switching Boost conversion branch are ensured to achieve zero-voltage or zero-current switching under low-power conditions. When the power adjustment command indicates a high-power region, the number of operating soft-switching Boost conversion branches is increased, the phase difference between operating branches is decreased, the total input current ripple is reduced, and the power switching transistors of all operating branches are ensured to maintain soft-switching conditions. The number of operating soft-switching Boost conversion branches is adjusted based on the balanced distribution of current stress in each soft-switching Boost conversion branch and the fact that the power density of each soft-switching Boost conversion branch is less than the safe operating area limit.

6. The high-efficiency solar inverter topology based on MPPT according to claim 5, characterized in that, The phase controller, through a digital signal processor, generates a precise PWM drive signal based on the calculated phase offset and duty cycle adjustment value of the drive signal. When controlling the turn-on and turn-off timing of the power switching transistors in each soft-switching Boost conversion branch, it includes: The maximum power point voltage reference value is compared with the acquired photovoltaic voltage signal to calculate the voltage error signal; the voltage error signal is input to a proportional-integral controller to generate a current reference value; the proportional-integral controller includes a proportional term and an integral term, the proportional term generates a control action based on the instantaneous value of the voltage error signal, and the integral term accumulates the voltage error signal; The current reference value is compared with the current data of all the soft-switching Boost conversion branches to calculate the current error signal; the current error signal is input to the proportional resonant controller to calculate and generate the phase offset and duty cycle adjustment value of the drive signal. The proportional resonant controller includes a proportional term and a resonant term. The proportional term provides system damping and accelerates dynamic response, while the resonant term provides high gain characteristics at the fundamental frequency, enabling zero steady-state error tracking of the sinusoidal reference signal. The phase offset is used to adjust the phase relationship between the drive signals of the power switches in each branch, and the duty cycle adjustment value is used to adjust the on-time of the power switches in each branch.

7. The high-efficiency solar inverter topology based on MPPT according to claim 6, characterized in that, The phase controller, through a digital signal processor, generates a precise PWM drive signal based on the calculated phase offset and duty cycle adjustment value of the drive signal. When controlling the turn-on and turn-off timing of the power switching transistors in each soft-switching Boost conversion branch, it includes: The phase offset and duty cycle adjustment values ​​are superimposed with preset phase reference signals and duty cycle reference signals to generate the final drive signal parameters of the power switching transistors in each soft-switching Boost conversion branch. The final drive signal parameters are converted into precise PWM drive signals by a digital signal processor to control the turn-on and turn-off timing of the power switching transistors in each soft-switching Boost conversion branch.

8. The high-efficiency solar inverter topology based on MPPT according to claim 7, characterized in that, When the soft-switching condition is not met, the phase controller dynamically adjusts the phase offset of the drive signal based on the power region information in the MPPT control signal, including: Within a preset time window before the power switch is turned on, it is detected whether the voltage across the power switch is lower than a preset voltage threshold. If the voltage before turn-on is lower than the preset voltage threshold, the zero-voltage switching condition is met. Within a preset time window before the power switch is turned off, it is detected whether the current flowing through the power switch is lower than a preset current threshold. If the current before turn-off is lower than the preset current threshold, the zero-current switching condition is met. If the voltage across the power switch is not lower than the preset voltage threshold before turn-on, or the current flowing through the power switch is not lower than the preset current threshold before turn-off, the soft-switching condition is not met. When the soft-switching condition is not met, the reference step size for phase offset adjustment is determined based on the current power region; the adjustment coefficient is calculated based on the degree of deviation from the soft-switching condition; and the actual phase offset adjustment is obtained by multiplying the reference step size by the adjustment coefficient.

9. The high-efficiency solar inverter topology based on MPPT according to claim 8, characterized in that, When the phase controller restores the soft-switching operation of the power switch to maintain the tracking accuracy of the maximum power point voltage reference value, it includes: The change in output voltage of the photovoltaic array is calculated based on the phase offset adjustment; the negative value of the voltage change is superimposed on the maximum power point voltage reference value as a compensation; the impact of the phase offset adjustment on the operating point of the photovoltaic array is offset in advance, ensuring that the photovoltaic array continues to operate near the maximum power point.

10. A method for controlling the topology of a high-efficiency solar inverter based on MPPT, used to apply the high-efficiency solar inverter topology based on MPPT as described in any one of claims 1-9, characterized in that, include: Photovoltaic voltage and current signals are collected, the real-time output power of the solar cell array is calculated, and the location of the maximum power point is determined based on the incremental conductance method. The real-time output power is compared with a power threshold to determine the current power region of the solar cell array, which includes a low-power region and a high-power region; the maximum power point voltage reference value is determined based on the maximum power point location, and a corresponding power adjustment command is generated based on the current power region; the maximum power point voltage reference value and the power adjustment command are integrated into an MPPT control signal. The operating state of all soft-switching Boost switching branches in the multi-phase interleaved parallel soft-switching Boost circuit is dynamically adjusted according to the MPPT control signal output; based on the voltage data of the DC bus and the current data of all soft-switching Boost switching branches, the phase offset and duty cycle adjustment value of the drive signal of the power switch tube in each soft-switching Boost switching branch are calculated based on the closed-loop feedback control algorithm, so that the output voltage of the photovoltaic array tracks the maximum power point voltage reference value. A precise PWM drive signal is generated by a digital signal processor based on the phase offset and duty cycle adjustment value of the drive signal, which controls the turn-on and turn-off timing of the power switching transistors in each soft-switching Boost conversion branch. The voltage and current waveforms of the power switching transistors in each soft-switching Boost conversion branch are monitored in real time. When the soft-switching condition is not met, the phase offset of the drive signal is dynamically adjusted based on the power region information in the MPPT control signal to restore the soft-switching working state of the power switching transistors and maintain the tracking accuracy of the maximum power point voltage reference value.

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