A control method of a power converter, a power converter and related devices

Abstract

The application discloses a power converter control method applied to a power converter with a common primary full-bridge switching circuit of an interleaved parallel Boost circuit and a dual active bridge converter. The output voltage, output current, grid voltage and grid-connected current of a photovoltaic module are collected, the target duty ratio of the primary full-bridge switching circuit is calculated based on the photovoltaic output parameters, the grid synchronous phase is obtained at the same time, the phase-shifted ratio adjustment amount is obtained by closed-loop regulation of the grid-connected current, the nominal phase-shifted ratio of the primary and secondary sides of the dual active bridge converter is calculated through the grid-connected current mathematical model in combination with the photovoltaic output voltage, the preset maximum switching frequency threshold and the grid-connected current reference value, the actual phase-shifted ratio and the real-time switching frequency matched with the actual phase-shifted ratio are determined after the nominal phase-shifted ratio is superimposed with the phase-shifted ratio adjustment amount in combination with the target duty ratio and the grid synchronous phase, and finally, the photovoltaic maximum power point tracking and unit power factor grid-connected inversion are realized by controlling the power converter based on the target duty ratio, the actual phase-shifted ratio and the real-time switching frequency.

Description

Technical Field

[0001] This invention relates to the field of distributed photovoltaic power generation technology, and in particular to a control method for a power converter, a power converter, and related equipment. Background Technology

[0002] With the continued advancement of the global dual-carbon strategy, new energy power generation technologies have experienced rapid development and large-scale application. Among them, distributed photovoltaic (PV) power generation, with its core advantages of local power generation and consumption, and low transmission losses, has become an important component of the new energy system. Balcony PV systems, especially those designed for lightweight applications such as urban residential and small commercial buildings, have seen rapid market growth in recent years due to their plug-and-play nature, ease of installation, and self-consumption-oriented operation. To maximize the utilization of electricity generated by PV modules, mitigate the intermittent fluctuations in PV power generation, and optimize electricity costs by adapting to peak-valley pricing policies, micro-inverters with energy storage capabilities have become core equipment in these scenarios.

[0003] Currently, microinverters with energy storage in the industry generally adopt a two- or three-stage power conversion topology. A typical implementation involves: a front-end using an independent boost converter to achieve maximum power point tracking (MPPT) control and voltage boosting for the photovoltaic (PV) modules; an intermediate stage using an independent bidirectional DC / DC converter to manage the charging and discharging of the energy storage battery and control bidirectional power flow; and a rear-end using a full-bridge or half-bridge inverter circuit to achieve DC-to-AC conversion and grid-connected control. The accompanying control system typically employs a multi-loop independent design architecture, with separate control loops for the PV MPPT, energy storage charging and discharging, and grid-connected current. Through the coordinated operation of these multiple loops, power control and grid-connected operation of the entire system are achieved. Furthermore, many existing single-stage microinverter topologies can only achieve direct grid connection of PV modules and are incompatible with bidirectional power flow control of the energy storage battery, making them unsuitable for the needs of residential PV applications with energy storage.

[0004] In the aforementioned existing technical solutions, multi-stage power conversion topologies require multiple independent switching bridge arms and corresponding drive circuits. Power devices cannot be reused, leading to redundant circuit architecture and making it difficult to further improve the overall power density, while also increasing the system's hardware cost. Furthermore, under the multi-stage power conversion architecture, photovoltaic power needs to undergo multiple power conversions before being transmitted to the grid. Each power conversion stage generates fixed conduction and switching losses, resulting in low overall conversion efficiency and insufficient utilization of photovoltaic power. Simultaneously, the independently designed control architecture with multiple loops exhibits strong coupling characteristics, making it highly susceptible to system oscillations. This not only significantly increases the development difficulty of the control logic but also leads to insufficient system stability under complex operating conditions. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and propose a single-stage micro inverter circuit topology and control method with portable energy storage. This simplifies the inverter circuit architecture to improve power density and reduce cost, and can also shorten the energy transmission path from photovoltaic to grid to improve power generation efficiency.

[0006] To achieve the above objectives, the present invention provides a control method for a power converter, a power converter, and related equipment.

[0007] In a first aspect, the present invention provides a control method for a power converter, the method being applied to the power converter, the power converter comprising an interleaved parallel boost circuit and a dual active bridge converter; the interleaved parallel boost circuit comprising a boost inductor assembly and a primary-side full-bridge switching circuit, the dual active bridge converter comprising an isolation transformer, a secondary-side bidirectional switching circuit and the primary-side full-bridge switching circuit; the interleaved parallel boost circuit and the dual active bridge converter sharing the primary-side full-bridge switching circuit;

[0008] The midpoint of the bridge arm of the primary-side full-bridge switching circuit is connected to the output terminal of the photovoltaic module through the boost inductor component, and the DC bus terminal of the primary-side full-bridge switching circuit is connected in parallel to the energy storage battery.

[0009] The primary winding of the isolation transformer is connected to the midpoint of the bridge arm of the primary full-bridge switching circuit, the secondary winding of the isolation transformer is connected to the AC terminal of the secondary bidirectional switching circuit, and the output terminal of the secondary bidirectional switching circuit is connected to the power grid.

[0010] The method includes:

[0011] Real-time acquisition of the photovoltaic module's output voltage, output current, grid voltage, and grid-connected current;

[0012] Based on the output voltage V of the photovoltaic module pv With output current I pv The target duty cycle D of the primary-side full-bridge switching circuit is calculated using the maximum power point tracking algorithm. b Controls the maximum power transfer from photovoltaic modules to energy storage batteries;

[0013] Based on grid voltage V g Obtain the grid synchronization phase θ;

[0014] Based on grid-connected current I g Compared with the preset grid-connected current reference value I ref Perform closed-loop regulation to obtain the shift ratio adjustment ∆D ps,n ;

[0015] According to the output voltage V of the photovoltaic module pvThe preset maximum switching frequency threshold f sw,max and the grid-connected current reference value I ref Based on a pre-established mathematical model of grid-connected current, the nominal shift ratio D between the primary and secondary sides of the dual active bridge converter is calculated. ps,n ;

[0016] The nominal shift is compared to D ps,n Compared to the shift, the adjustment amount ∆D ps,n Superimposed, combined with the target duty cycle D b Synchronize with the power grid phase θ to determine the actual displacement ratio D ps Compared to the actual movement D ps Matching real-time switching frequency f sw ;

[0017] Based on the target duty cycle D b The actual displacement compared to D ps and the real-time switching frequency f sw The secondary-side extended phase-shift modulation strategy is used to generate drive signals for the primary-side full-bridge switching circuit and the secondary-side switching circuit, thereby controlling the power converter to synchronously achieve photovoltaic maximum power point tracking and unity power factor grid-connected inversion.

[0018] In one possible implementation, the output voltage V based on the photovoltaic module pv With output current I pv The target duty cycle D of the primary-side full-bridge switching circuit is calculated using the maximum power point tracking algorithm. b ,include:

[0019] According to the output voltage V pv With the output current I pv Calculate the input power of the photovoltaic module, and determine the target duty cycle value that maximizes the input power of the photovoltaic module by perturbing the duty cycle.

[0020] Wherein, the duty cycle is related to the output voltage V pv The relationship satisfies:

[0021] ;

[0022] Among them, V pv The output voltage is given by , where Db is the duty cycle and Vbat is the energy storage battery voltage.

[0023] In one possible implementation, the voltage V based on the grid voltage... g Obtaining the grid synchronization phase θ includes:

[0024] The grid voltage V gThe signal is decomposed into two orthogonal voltage signals with a 90° phase difference by a second-order generalized integrator.

[0025] The grid synchronization phase θ is calculated using a single-phase phase-locked loop based on the two orthogonal voltage signals.

[0026] In one possible implementation, the grid-connected current I... g Compared with the preset grid-connected current reference value I ref Perform closed-loop regulation to obtain the shift ratio adjustment ∆D ps,n ,include:

[0027] By performing a Parker transformation on the grid-connected current Ig using the grid synchronization phase θ, the active component id and reactive component iq of the grid-connected current Ig in the dq rotating coordinate system are obtained.

[0028] The active component id is controlled by a proportional-integral controller to track the grid-connected current reference value Iref, and the shift ratio adjustment amount ∆Dps,n is obtained by outputting the result.

[0029] The reactive component iq is controlled by a proportional-integral controller to track the 0 value, thereby achieving unity power factor grid connection.

[0030] In one possible implementation, the expression for the grid-connected current Ig in the pre-established mathematical model of the grid-connected current is:

[0031] ;

[0032] Wherein, ig is the grid-connected current, n is the turns ratio of the isolation transformer, Vpv is the input voltage of the photovoltaic module, Db is the target duty cycle, Ls is the equivalent leakage inductance of the transformer, fsw is the switching frequency, and Dps1 and Dps2 are phase shift compensation values ​​calculated based on the target duty cycle Db.

[0033] D ps1 and D ps2 The expression is:

[0034] .

[0035] In one possible implementation, the determination of the actual movement is compared to D. ps Compared to the actual movement D ps Matching real-time switching frequency f sw ,include:

[0036] When the grid-connected current reference value Iref is less than or equal to a preset current threshold, the system switches to light-load mode. The actual shift ratio Dps and the real-time switching frequency fsw are:

[0037] ;

[0038] Wherein, Dps1 and Dps2 are phase shift compensation values ​​calculated based on the target duty cycle. The shift ratio adjustment amount, This represents the maximum switching frequency under light load. Let |sinθ| be the target duty cycle, and |sinθ| be the absolute value of the sine of the grid synchronization phase θ. Compared to the nominal displacement under light load mode;

[0039] When the grid-connected current reference value Iref is greater than the current threshold, the system switches to heavy load mode. The actual shift ratio Dps and the real-time switching frequency fsw are:

[0040] ;

[0041] in, This represents the maximum reload switching frequency. Compared to the nominal displacement in heavy-load mode.

[0042] In one possible implementation, the driving logic of the primary-side full-bridge switching circuit in the secondary-side extended phase-shift modulation strategy is specifically as follows:

[0043] The target duty cycle Db is used as the conduction duty cycle of the drive signals of the two lower bridge arm switches in the primary-side full-bridge switching circuit to control the two lower bridge arm switches; wherein, the drive signals of the two lower bridge arm switches are 180° out of phase; in the primary-side full-bridge switching circuit, the upper bridge arm switches and the lower bridge arm switches of the same bridge arm are complementary in conduction.

[0044] In the aforementioned secondary-side extended phase-shift modulation strategy, the driving logic of the secondary-side switching circuit is specifically as follows:

[0045] When the grid voltage Vg is in the positive half-cycle, the lower transistors of the two sets of bidirectional switches in the secondary-side switching circuit are kept on, and the upper transistors of the two sets of bidirectional switches are complementary and on. The phase difference between the driving signal of the lower transistor of the right bridge arm of the primary-side full-bridge switching circuit and the upper transistor of the upper bridge arm in the secondary-side switching circuit matches the actual shift ratio Dps.

[0046] When the grid voltage Vg is in the negative half-cycle, the upper transistors of the two sets of bidirectional switches in the secondary-side switching circuit remain on, the lower transistors of the two sets of bidirectional switches are complementary and on, and the phase difference between the driving signal of the lower transistor of the right bridge arm of the primary-side full-bridge switching circuit and the lower transistor of the lower bridge arm in the secondary-side switching circuit matches the actual shift ratio Dps.

[0047] In a second aspect, the present invention provides a power converter, characterized in that it includes an interleaved parallel boost circuit, a dual active bridge converter, and a controller; the interleaved parallel boost circuit includes a boost inductor component and a primary-side full-bridge switching circuit, the dual active bridge converter includes an isolation transformer, a secondary-side bidirectional switching circuit, and the primary-side full-bridge switching circuit; the interleaved parallel boost circuit and the dual active bridge converter share the primary-side full-bridge switching circuit;

[0048] The midpoint of the bridge arm of the primary-side full-bridge switching circuit is connected to the output terminal of the photovoltaic module through the boost inductor component, and the DC bus terminal of the primary-side full-bridge switching circuit is connected in parallel to the energy storage battery.

[0049] The primary winding of the isolation transformer is connected to the midpoint of the bridge arm of the primary full-bridge switching circuit, the secondary winding of the isolation transformer is connected to the AC terminal of the secondary bidirectional switching circuit, and the output terminal of the secondary bidirectional switching circuit is connected to the power grid.

[0050] The controller is used to execute the control method for the power converter as described in any one of the first aspects.

[0051] In one possible implementation, the boost inductor assembly includes a first boost inductor and a second boost inductor; the primary-side full-bridge switching circuit includes a first switch, a second switch, a third switch, and a fourth switch.

[0052] The first switch and the second switch are connected in series to form the first primary side bridge arm, and the third switch and the fourth switch are connected in series to form the second primary side bridge arm. The first primary side bridge arm and the second primary side bridge arm are connected in parallel.

[0053] The first end of the first boost inductor is connected to the positive terminal of the photovoltaic module, and the second end of the first boost inductor is connected to the midpoint of the first primary side bridge arm;

[0054] The first end of the second boost inductor is connected to the positive terminal of the photovoltaic module, and the second end of the second boost inductor is connected to the midpoint of the second primary side bridge arm;

[0055] The negative terminal of the photovoltaic module and the negative terminal of the energy storage battery are connected to the negative terminal of the full-bridge DC bus, and the positive terminal of the energy storage battery is connected to the positive terminal of the full-bridge DC bus.

[0056] In one possible implementation, the dual active bridge converter further includes a first capacitor and a second capacitor; the secondary-side bidirectional switching circuit includes a fifth switch, a sixth switch, a seventh switch, and an eighth switch.

[0057] The fifth and sixth switches are connected in reverse series to form a first bidirectional switch branch, and the seventh and eighth switches are connected in reverse series to form a second bidirectional switch branch; the first end of the first bidirectional switch branch is connected to the first end of the second bidirectional switch branch.

[0058] The first terminal of the first capacitor is connected to the first terminal of the second capacitor;

[0059] The second end of the first bidirectional switch branch is connected to the second end of the first capacitor, and the second end of the second bidirectional switch branch is connected to the second end of the second capacitor;

[0060] The first end of the secondary winding of the isolation transformer is connected to the common terminal of the first bidirectional switch branch and the second bidirectional switch branch, and the second end of the secondary winding of the isolation transformer is connected to the common terminal of the first capacitor and the second capacitor.

[0061] In one possible implementation, the dual active bridge converter further includes a third inductor and a fourth inductor;

[0062] The first end of the fourth inductor is connected to the second end of the first capacitor, and the second end of the fourth inductor is connected to the power grid.

[0063] The first terminal of the secondary winding of the third inductor is connected to the common terminal of the first bidirectional switch branch and the second bidirectional switch branch.

[0064] In one possible implementation, the power converter further includes a third capacitor;

[0065] The third capacitor is connected in parallel across the two ends of the photovoltaic module.

[0066] In one possible implementation, the power converter further includes a fourth capacitor connected in parallel across the energy storage battery.

[0067] Thirdly, the present invention provides a control device for a power converter, characterized in that the control device includes a sampling unit, a processor, and a memory;

[0068] The sampling unit is used to collect the output voltage and output current of the photovoltaic module, and the grid voltage and grid-connected current on the grid side; the memory is used to store computer programs; the processor is used to execute the computer programs in the memory to implement the control method of the power converter as described in any one of the first aspects.

[0069] Fourthly, the present invention provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program, which, when loaded and executed by a processor, implements the control method of the power converter according to any one of the first aspects.

[0070] This invention provides a power converter control method applied to a power converter topology where an interleaved parallel Boost circuit and a dual active bridge converter share a primary-side full-bridge switching circuit. This method acquires real-time data on the output voltage and current of the photovoltaic (PV) modules, as well as the grid voltage and grid-connected current. First, based on the PV output parameters, it calculates the target duty cycle of the primary-side full-bridge switching circuit using a maximum power point tracking (MPPT) algorithm to achieve maximum power transfer from the PV modules to the energy storage battery. Simultaneously, it obtains the grid synchronization phase based on the grid voltage and performs closed-loop regulation of the grid-connected current to obtain the phase shift adjustment. Finally, it combines this with the PV... The output voltage, preset maximum switching frequency threshold, and grid-connected current reference value are used to calculate the nominal shift ratio of the primary and secondary sides of the dual active bridge converter through a pre-established grid-connected current mathematical model. The nominal shift ratio is then superimposed with the shift ratio adjustment, and the actual shift ratio and the matching real-time switching frequency are determined by combining the target duty cycle and the grid synchronization phase. Finally, based on the target duty cycle, the actual shift ratio, and the real-time switching frequency, the drive signals for the primary-side full-bridge switching circuit and the secondary-side switching circuit are generated using a secondary-side extended phase-shift modulation strategy. This controls the power converter to synchronously achieve photovoltaic maximum power point tracking and unity power factor grid-connected inversion.

[0071] This invention addresses a single-stage power converter topology featuring interleaved parallel Boost converters and dual active bridges sharing a primary-side full-bridge. Through integrated control logic, it achieves synchronous execution of photovoltaic maximum power point tracking and grid-connected inverter control, eliminating the need for multiple independently coupled control loops and significantly simplifying the system control architecture. The nominal shift ratio is calculated using a pre-established mathematical model of the grid-connected current, and the final control parameters are determined by combining the shift ratio adjustment obtained from closed-loop regulation. Simultaneously, the corresponding real-time switching frequency is matched to the actual shift ratio, achieving precise closed-loop control of the grid-connected current and ensuring the stability of grid-connected operation. A secondary-side extended phase-shift modulation strategy generates the drive signal, perfectly adapting to the single-stage topology with multiplexed bridge arms, achieving unity power factor grid connection. Furthermore, relying on integrated control adapted to the single-stage power converter topology, it effectively shortens the energy transmission path from photovoltaic power to the grid, improving the utilization efficiency of photovoltaic power. Attached Figure Description

[0072] Figure 1 A schematic diagram of a power converter provided in an embodiment of the present invention;

[0073] Figure 2 A schematic diagram of a control method for a power converter provided in an embodiment of the present invention;

[0074] Figure 3 This invention provides a schematic diagram of key waveforms of the power converter under secondary-side EPS modulation in an embodiment of the present invention when the grid voltage is in the positive half-cycle, wherein v g1 -v g8 These are the drive signals for Q1-Q8;

[0075] Figure 4 A control block diagram of the controller provided in an embodiment of the present invention;

[0076] Figure 5 The simulated voltage V of the photovoltaic module provided in the embodiments of the present invention pv and current I pv Waveform;

[0077] Figure 6 The simulated voltage V of the energy storage battery provided in the embodiments of the present invention bat and current I bat Waveform;

[0078] Figure 7 The simulated voltage v of the power grid provided in the embodiments of the present invention g and current i g Waveform;

[0079] Figure 8 The current i of the input-side boost inductor provided in the embodiment of the present invention L1 i L2 The current i of the transformer equivalent leakage inductance Ls . Detailed Implementation

[0080] As mentioned earlier, with the continuous advancement of the dual-carbon strategy, distributed photovoltaic power generation technology is rapidly becoming more widespread. Among them, the market size of balcony photovoltaic systems adapted to urban residential and small commercial scenarios is growing rapidly, and micro inverters with energy storage access functions have become the core equipment for achieving efficient photovoltaic utilization in such scenarios.

[0081] Currently, most microinverters with energy storage adopt a two- or three-stage power conversion topology, which sequentially uses an independent Boost circuit, a bidirectional DC / DC converter, and an inverter circuit to realize photovoltaic MPPT control, energy storage charging and discharging management, and grid-connected inversion, respectively. They are equipped with a control architecture with multiple independent loop designs. Most existing single-stage microinverters only support direct grid connection of photovoltaics and cannot be compatible with bidirectional power flow control of energy storage.

[0082] The aforementioned multi-level topology requires multiple sets of independent switching arms, and power devices cannot be reused. This not only results in redundant circuit architecture, limited overall power density, and high hardware costs, but also generates additional losses due to multiple power conversions, reducing the overall conversion efficiency. At the same time, strong coupling exists between multiple control loops, which can easily cause system oscillations, increasing development difficulty and reducing operating condition adaptability. Power converters compatible with energy storage generally suffer from nonlinearity between grid-connected current and control quantities, insufficient grid-connected control accuracy, and high harmonic content, making it difficult to meet grid-connected standard requirements and hindering large-scale application.

[0083] This invention addresses a single-stage power converter topology featuring interleaved parallel Boost converters and dual active bridges sharing a primary-side full-bridge. Through integrated control logic, it achieves synchronous execution of photovoltaic maximum power point tracking and grid-connected inverter control, eliminating the need for multiple independently coupled control loops and significantly simplifying the system control architecture. The nominal shift ratio is calculated using a pre-established mathematical model of the grid-connected current, and the final control parameters are determined by combining the shift ratio adjustment obtained from closed-loop regulation. Simultaneously, the corresponding real-time switching frequency is matched to the actual shift ratio, achieving precise closed-loop control of the grid-connected current and ensuring the stability of grid-connected operation. A secondary-side extended phase-shift modulation strategy generates the drive signal, perfectly adapting to the single-stage topology with multiplexed bridge arms, achieving unity power factor grid connection. Furthermore, relying on integrated control adapted to the single-stage power converter topology, it effectively shortens the energy transmission path from photovoltaic power to the grid, improving the utilization efficiency of photovoltaic power.

[0084] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0085] For ease of explanation, the embodiments of the present invention will first introduce the power converter provided by the embodiments of the present invention. For example... Figure 1 As shown, Figure 1 This is a schematic diagram of a power converter according to an embodiment of the present invention. The power converter includes an interleaved parallel boost circuit, a dual active bridge converter, and a controller.

[0086] The interleaved parallel boost circuit includes a boost inductor assembly and a primary-side full-bridge switching circuit. The dual active bridge converter includes an isolation transformer, a secondary-side bidirectional switching circuit, and a primary-side full-bridge switching circuit. Both the interleaved parallel boost circuit and the dual active bridge converter share the primary-side full-bridge switching circuit.

[0087] The midpoint of the bridge arm of the primary-side full-bridge switching circuit is connected to the output terminal of the photovoltaic module through a boost inductor component, and the DC bus of the primary-side full-bridge switching circuit is connected in parallel to the energy storage battery.

[0088] The primary winding of the isolation transformer is connected to the midpoint of the bridge arm of the primary full-bridge switching circuit, the secondary winding of the isolation transformer is connected to the AC terminal of the secondary bidirectional switching circuit, and the output terminal of the secondary bidirectional switching circuit is connected to the power grid.

[0089] The primary-side full-bridge switching circuit is a shared core component for both functional modules. In one possible implementation, the primary-side full-bridge switching circuit includes a first switch Q1, a second switch Q2, a third switch Q3, and a fourth switch Q4. The first switch Q1 and the second switch Q2 are connected in series as the first primary-side bridge arm, and the third switch Q3 and the fourth switch Q4 are connected in series as the second primary-side bridge arm. The first and second primary-side bridge arms are connected in parallel. The upper ends of both bridge arms are connected to the positive terminal of the full-bridge DC bus, and the lower ends of both bridge arms are connected to the negative terminal of the full-bridge DC bus. The midpoints of the two bridge arms are connected to the two output terminals of the boost inductor assembly, and also to the two ends of the primary winding of the isolation transformer.

[0090] The primary-side full-bridge switching circuit, on the one hand, works with the boost inductor to form the switching unit of the interleaved parallel Boost circuit. Through the on and off actions of its own switching transistors, it controls the energy storage and release rhythm of the boost inductor to achieve the maximum power transfer of the photovoltaic module. On the other hand, as the primary-side bridge arm of the dual active bridge converter, it outputs a square wave voltage signal to work with the secondary-side circuit to complete the power transfer and inversion conversion between the primary and secondary sides.

[0091] The boost inductor assembly includes two boost inductors connected in parallel. Their input terminals are both connected to the positive output terminal of the photovoltaic module, and their two output terminals are respectively connected to the midpoints of the two arms of the primary-side full-bridge switching circuit. The boost inductor assembly is used to complete the energy storage and release process under the switching action of the primary-side full-bridge switching circuit, thereby achieving the boosting and alternating parallel voltage conversion of the photovoltaic output voltage. In one possible implementation, the boost inductor assembly includes a first boost inductor L1 and a second boost inductor L2. The first terminal of the first boost inductor L1 is connected to the positive terminal of the photovoltaic module PV, and the second terminal of the first boost inductor L1 is connected to the midpoint of the first primary-side bridge arm. The first terminal of the second boost inductor L2 is connected to the positive terminal of the photovoltaic module PV, and the second terminal of the second boost inductor L2 is connected to the midpoint of the second primary-side bridge arm.

[0092] The photovoltaic (PV) module, as the core power input unit of the system, is used to convert solar energy into direct current (DC) electricity. The positive output terminal of the PV module is connected to the input terminal of the boost inductor module, and the negative output terminal is connected to the negative terminal of the DC bus, providing input power to the entire system. In one possible implementation, the power converter also includes a third capacitor C3; this third capacitor is connected in parallel across the PV module.

[0093] The energy storage battery is connected in parallel across the DC bus of the primary-side full-bridge switching circuit; that is, the positive terminal of the energy storage battery is connected to the positive terminal of the DC bus, and the negative terminal is connected to the negative terminal of the DC bus. The energy storage battery serves two purposes: firstly, it receives and stores the electrical energy output from the photovoltaic modules, smoothing out intermittent fluctuations in photovoltaic power generation; secondly, it provides a stable DC bus voltage for the dual active bridge converter, serving as the DC input source for the grid-connected inverter. In one possible implementation, the power converter also includes a fourth capacitor C4, which is connected in parallel across the energy storage battery.

[0094] An isolation transformer consists of a primary winding and a secondary winding. The two ends of the primary winding are connected to the midpoints of the two arms of the primary full-bridge switching circuit, and the two ends of the secondary winding are connected to the AC terminals of the secondary bidirectional switching circuit. The isolation transformer achieves electrical isolation between the primary DC side and the AC side of the power grid, improving system safety and interference immunity. Furthermore, it achieves voltage matching between the primary and secondary sides through its winding turns ratio. Its equivalent leakage inductance also serves as the power transfer inductance of the dual active bridge converter, participating in the power transfer process between the primary and secondary sides.

[0095] In one possible implementation, the dual active bridge converter further includes a third inductor L3 and a fourth inductor L4. The first terminal of the fourth inductor L4 is connected to the second terminal of the first capacitor C1, and the second terminal of the fourth inductor L4 is connected to the power grid. The first terminal of the third inductor L3 is connected to the first terminal of the secondary winding, and the second terminal of the third inductor L3 is connected to the common terminal of the first and second bidirectional switching branches.

[0096] The secondary-side bidirectional switching circuit includes two sets of bidirectional switching branches connected in reverse series. These two sets are connected in parallel, with their common terminals serving as AC terminals connected to both ends of the secondary winding of the isolation transformer. The two output terminals of each bidirectional switching branch are connected to both ends of the power grid. This circuit, acting as the secondary arm of a dual active bridge converter, works in conjunction with the switching action of the primary-side full-bridge switching circuit to convert DC power to AC power through phase-shift control. Simultaneously, by switching the bidirectional switches on and off, it adapts to the commutation requirements of the positive and negative half-cycles of the grid voltage, ensuring that the grid-connected current and grid voltage are in phase and frequency synchronized.

[0097] In one possible implementation, the secondary-side bidirectional switching circuit includes a fifth switch Q5, a sixth switch Q6, a seventh switch Q7, and an eighth switch Q8; the dual active bridge converter also includes a first capacitor C1 and a second capacitor C2.

[0098] The fifth switch Q5 and the sixth switch Q6 are connected in reverse series to form the first bidirectional switch branch, and the seventh switch Q7 and the eighth switch Q8 are connected in reverse series to form the second bidirectional switch branch; the first end of the first bidirectional switch branch is connected to the first end of the second bidirectional switch branch.

[0099] The first terminal of the first capacitor C1 is connected to the first terminal of the second capacitor C2. The second terminal of the first bidirectional switch branch is connected to the second terminal of the first capacitor C1, and the second terminal of the second bidirectional switch branch is connected to the second terminal of the second capacitor C2.

[0100] The first end of the secondary winding of the isolation transformer is connected to the common terminal of the first bidirectional switch branch and the second bidirectional switch branch, and the second end of the secondary winding of the isolation transformer is connected to the common terminal of the first capacitor C1 and the second capacitor C2.

[0101] The power converter provided in this invention, through the bridge arm multiplexing architecture of the primary-side full-bridge switching circuit, can simultaneously achieve flexible switching and coordinated operation of three power transmission paths: photovoltaic to energy storage, energy storage to the grid, and photovoltaic direct power supply to the grid, adapting to the diverse operating conditions of residential photovoltaic scenarios. Under normal photovoltaic module power generation conditions, the primary-side full-bridge switching circuit, in conjunction with the boost inductor module, operates in interleaved parallel Boost mode. By controlling the duty cycle of the primary-side full-bridge switching transistors, the output operating point of the photovoltaic module can be adjusted, achieving maximum power transmission from the photovoltaic module to the energy storage battery, prioritizing the storage of photovoltaic energy in the energy storage battery, and smoothing out intermittent fluctuations in photovoltaic power generation. When the system needs grid-connected power supply, the primary-side full-bridge switching circuit also serves as the primary-side bridge arm of a dual active bridge converter, working in conjunction with the secondary-side bidirectional switching circuit to convert the DC power output from the energy storage battery into AC power with the same frequency and phase as the grid through the primary-secondary power conversion of the isolation transformer, completing the grid-connected inverter process.

[0102] Based on the power converter described above, embodiments of the present invention provide a control method for the power converter, such as... Figure 2 As shown, the method includes:

[0103] S201: Real-time acquisition of photovoltaic module output voltage V pv The output current I of the photovoltaic module pv Grid voltage V g With grid-connected current V i .

[0104] The output voltage V of the photovoltaic module pvThe DC voltage between the positive and negative output terminals of a photovoltaic module is a core electrical parameter characterizing the current operating state of the photovoltaic module. Its value fluctuates dynamically with changes in light intensity, ambient temperature, and load conditions, and it is a core fundamental parameter for achieving photovoltaic maximum power point tracking control.

[0105] The output current I of the photovoltaic module pv The value of the direct current flowing through the output circuit of the photovoltaic module is related to the output voltage V. pv Together, they determine the real-time output power of the photovoltaic module. Their value changes with the operating voltage of the photovoltaic module and the light environment. They are the core parameters for calculating the photovoltaic output power and achieving maximum power point optimization.

[0106] Grid voltage V g The instantaneous value of AC voltage at the common coupling point on the power grid side is a standard power frequency sinusoidal AC signal. Its amplitude, frequency, and phase are the core reference for achieving power grid synchronization phase locking and ensuring that the grid-connected current and the power grid voltage are in phase and frequency.

[0107] Grid-connected current I g The instantaneous value of the alternating current supplied by the power converter to the grid is the core controlled object of grid-connected inverter control. Its waveform distortion rate, phase deviation, and amplitude accuracy directly determine whether the grid-connected power quality meets the stringent requirements of the grid connection standards.

[0108] This invention is implemented through the coordinated operation of the hardware sampling circuit of the power converter and the on-chip sampling peripheral of the controller. Specifically, it addresses the DC voltage V on the photovoltaic side. pv With DC current I pv A DC-isolated sampling architecture is used for data acquisition. The photovoltaic output voltage is stepped down using a high-precision, low-temperature drift resistor divider network to obtain the voltage relative to V. pv A voltage sampling signal with a fixed ratio is generated. The current signal of the photovoltaic output circuit is acquired by a high-precision Hall DC current sensor and converted into a corresponding voltage sampling signal. The two DC sampling signals are then processed by a signal conditioning circuit consisting of an RC filter circuit and an operational amplifier to remove noise and adjust amplitude before being synchronously input to the controller's analog-to-digital conversion channel. This is based on the AC voltage V on the grid side. g With grid current I g An AC isolation sampling architecture is used for data acquisition. A voltage transformer is used to achieve electrical isolation and signal step-down of the grid voltage, and a current transformer is used to achieve electrical isolation and signal acquisition of the grid current. The two AC sampling signals are boosted to the effective input range of the controller's analog-to-digital conversion peripheral through a bias conditioning circuit and synchronously connected to the corresponding sampling channel of the controller.

[0109] In this embodiment, the controller performs synchronous trigger acquisition and digital preprocessing operations on each sampling signal to ensure the synchronization and accuracy of the sampled data. The controller's analog-to-digital conversion peripheral adopts a synchronous trigger mode, performing synchronous sampling of two DC parameters on the photovoltaic side and two AC parameters on the grid side at the same frequency. The sampling frequency is set to 10 times the switching frequency of the power converter, ensuring that multiple sets of continuous real-time sampling data can be acquired in each switching cycle, meeting the real-time requirements of subsequent control algorithms. Simultaneously, the controller performs digital filtering and calibration processing on the acquired raw sampling data: a moving average filtering algorithm is used to filter out high-frequency switching noise, grid harmonic interference, and random pulse interference mixed in the sampling signal; zero-point calibration and gain calibration are performed to address hardware system errors in the sampling circuit, eliminating fixed and proportional deviations caused by the hardware circuit, ultimately obtaining accurate V. pv I pv V g I g The system generates real-time numerical values ​​and outputs the processed valid data to subsequent control algorithm modules.

[0110] As the starting point and data foundation of the entire control method, this embodiment of the invention provides reliable and timely basic data support for subsequent maximum power point tracking (MPPT) algorithms, grid synchronization phase-locked loop (PLL) algorithms, and grid-connected current closed-loop control algorithms through synchronous and high-precision real-time acquisition of core electrical parameters on both the photovoltaic and grid sides. This fundamentally ensures the control accuracy and operational stability of the entire control method. Simultaneously, this step employs an AC / DC isolated sampling architecture, combined with synchronous acquisition, digital filtering, and hardware calibration, effectively suppressing electromagnetic interference caused by high-frequency switching of the power converter. This ensures the accuracy and anti-interference capability of the sampled data under complex electromagnetic conditions, avoiding problems such as control algorithm failure, inaccurate MPPT, and substandard grid-connected power quality due to distorted sampled data. This significantly improves the operational reliability and all-condition adaptability of the entire power converter system.

[0111] S202: Based on the output voltage V of the photovoltaic module pv With output current I pv The target duty cycle D of the primary-side full-bridge switching circuit is calculated using the maximum power point tracking algorithm. b It controls the maximum power transfer from photovoltaic modules to energy storage batteries.

[0112] Maximum Power Point Tracking (MPPT) is a control algorithm that optimizes and locks the operating point corresponding to the maximum output power of a photovoltaic (PV) module in real time, taking into account the dynamic changes in the output characteristics of PV modules with light intensity and ambient temperature. It is a core control method for improving the utilization rate of solar energy in PV systems. Its core logic is to adjust the operating voltage of the PV module so that the PV module always works at the maximum power output state under any operating conditions.

[0113] Target duty cycle D b In a primary-side full-bridge switching circuit, the ratio of the conduction time of the two lower-arm switches within one switching cycle to the total duration of the switching cycle is the core control variable for controlling the operating characteristics of the interleaved parallel Boost circuit. In the bridge arm reuse topology of this invention, this parameter directly determines the operating voltage of the photovoltaic module and provides basic parameters for the phase shift control and switching frequency calculation of the subsequent grid-connected inverter stage.

[0114] Maximum power transfer refers to the transfer of power through the target duty cycle D. b The system adjusts the power output of the photovoltaic modules to ensure that they always output the maximum usable power under the current light and temperature conditions. This power is then efficiently and with low loss transmitted to the energy storage battery for storage, maximizing the use of solar energy captured by the photovoltaic modules, smoothing out the intermittent fluctuations in photovoltaic power generation, and providing a stable power source for subsequent grid-connected inverters.

[0115] In this embodiment of the invention, the maximum power point of photovoltaic (MPPT) optimization and the target duty cycle D are achieved through the MPPT algorithm. b The solution involves first receiving the photovoltaic output voltage V. pv With output current I pv The instantaneous power calculation formula is used to calculate the current output power P of the photovoltaic module in real time. pv Meanwhile, the output power and output voltage values ​​calculated in the current cycle are compared and stored with the latched values ​​of the previous control cycle, providing a complete data foundation for the optimization judgment of the MPPT algorithm.

[0116] In this embodiment, the energy storage battery is directly connected in parallel across the DC bus of the primary-side full-bridge switching circuit in the power converter topology. The energy storage battery voltage V... bat During charging and discharging, the fluctuation amplitude is extremely small and remains basically stable, therefore the output voltage V of the photovoltaic module is... pv Duty cycle D b There exists a fixed linear correspondence between them:

[0117] (1)

[0118] Among them, V pv For the output voltage, D b V is the duty cycle. bat This refers to the energy storage battery voltage. This linear relationship directly translates the adjustment of the photovoltaic operating voltage into an adjustment of the target duty cycle D. b The single-variable regulation eliminates the need for additional voltage closed-loop control circuit design, significantly simplifying the execution logic of the MPPT algorithm.

[0119] In this embodiment of the invention, the perturbation-observation method, which has strong engineering adaptability and robustness, is used as the core MPPT algorithm. The algorithm executes optimization actions with a fixed control cycle, and the control cycle is synchronized with the switching cycle of the power converter to ensure the real-time performance and control continuity of the optimization actions. Within each optimization control cycle, the controller adjusts the target duty cycle D. b Apply a small positive perturbation with a fixed step size, and then detect the photovoltaic output power P after the perturbation. pv The changing trend.

[0120] If the photovoltaic output power increases after the disturbance, the current optimization direction is determined to be correct, and the next control cycle continues to optimize D in the same direction. b Apply a perturbation with equal step size; if the photovoltaic output power decreases after the perturbation, the current optimization direction is determined to be incorrect, and the duty cycle D is adjusted in the opposite direction in the next control cycle. b Apply a periodic perturbation. Through this periodic perturbation, judgment, and adjustment, the algorithm can quickly find and lock the optimal target duty cycle D corresponding to the maximum photovoltaic output power under the current operating conditions. b Simultaneously, the controller synchronously outputs the calculated target duty cycle Db to the PWM modulation module and subsequent grid-connected control circuit. This provides core control parameters for the generation of drive signals for the primary-side full-bridge switching circuit, and, in conjunction with the interleaved parallel drive logic, enables the two boost inductors to operate at 180° phase shift, reducing photovoltaic input current ripple. It also provides basic parameters for the subsequent calculation of the phase shift ratio and switching frequency, ensuring the coordinated operation of the entire control method.

[0121] S203: Based on grid voltage V g Obtain the grid synchronization phase θ.

[0122] The grid synchronization phase θ refers to the instantaneous phase angle of the grid power frequency sinusoidal voltage signal. It is a core parameter characterizing the real-time change state of the grid voltage. Its change period is strictly consistent with the grid voltage period. It is the core reference benchmark for realizing synchronous tracking of grid-connected current and grid voltage and grid connection with unity power factor. It is also the core basic parameter for subsequent grid-connected current coordinate transformation, phase shift and switching frequency calculation.

[0123] The second-order generalized integrator (SOGI) is a digital filtering algorithm that can achieve zero steady-state error tracking of a specific power frequency signal and simultaneously generate two strictly orthogonal signals. In a single-phase grid-connected system, it is used to solve the problem that a single AC signal cannot be directly subjected to synchronous rotating coordinate transformation. At the same time, it can effectively filter out harmonic components in the grid voltage, suppress interference caused by grid voltage distortion and DC bias, and improve the anti-interference capability of the phase-locked loop.

[0124] A single-phase phase-locked loop (PLL) is a control algorithm that tracks the frequency and phase of the grid voltage in real time through closed-loop control and outputs a phase signal that is completely synchronized with the grid voltage. It is the core technology for photovoltaic grid-connected inverters to achieve grid synchronization. Its core function is to quickly and accurately lock the real-time phase of the grid voltage under complex operating conditions such as grid voltage amplitude fluctuations, frequency offsets, and waveform distortions, so as to ensure the synchronization and stability of grid-connected control.

[0125] Unity power factor grid connection refers to a situation where the phase difference between the grid-connected current output by the power converter and the grid voltage is 0, maximizing active power transmission efficiency and reducing reactive power output to 0. This is a core requirement of grid connection standards for photovoltaic grid-connected inverters, which can effectively reduce grid line losses and avoid reactive power pollution to the grid.

[0126] In this embodiment of the invention, a single-phase phase-locked loop (SOGI-PLL) architecture based on a second-order generalized integrator is used to accurately acquire the grid synchronization phase θ. The entire process is executed in real time by the controller's digital processing unit. First, the controller receives the grid voltage Vg and uses it as the input signal to the SOGI module. The SOGI module uses the grid's rated power frequency as its resonant frequency and performs orthogonalization processing and digital filtering on the input grid voltage signal. On one hand, it outputs an α-axis voltage signal v_gα that is in phase and frequency with the input grid voltage signal. On the other hand, it outputs a β-axis orthogonal voltage signal v_gβ that is strictly out of phase with v_gα by 90°. These two orthogonal signals completely eliminate harmonic components, DC bias, and random noise interference mixed in the grid voltage, providing a high signal-to-noise ratio foundation signal for the subsequent accurate phase locking of the phase-locked loop. At the same time, the SOGI module has frequency adaptive characteristics and can adjust the resonant frequency in real time to follow the fluctuations of the grid frequency. Even when the grid frequency deviates from the rated value, it can still stably output two orthogonal signals without phase deviation, ensuring the adaptability of the phase-locked loop under abnormal grid conditions.

[0127] The two orthogonal voltage signals v_gα and v_gβ obtained by the SOGI module are input to the closed-loop control of the phase-locked loop (PLL) to achieve phase locking. First, based on the principle of synchronous rotating coordinate transformation, the Parker transform is performed on the two voltage signals in the orthogonal stationary coordinate system using the phase estimate of the current PLL output, converting them into d-axis and q-axis voltage components in the dq rotating coordinate system. The value of the q-axis voltage component directly reflects the deviation between the PLL output phase and the actual phase of the grid voltage. When the q-axis voltage component is 0, it indicates that the PLL output phase and the actual phase of the grid voltage are completely coincident, achieving precise phase locking. Subsequently, the q-axis voltage component is input to a proportional-integral (PI) controller for zero steady-state error closed-loop regulation. The output of the PI controller is the adjustment amount of the grid angular frequency. This adjustment amount is superimposed on the grid's rated angular frequency, integrated by an integrator, and finally outputs a grid synchronization phase θ that is completely synchronized with the real-time phase of the grid voltage. In this embodiment, the parameters of the PI controller are engineered to balance the dynamic response speed and steady-state locking accuracy of the phase-locked loop. It can quickly complete phase relocking within several power frequency cycles under conditions of sudden changes in grid voltage phase and frequency shift, while maintaining a phase locking error of less than 0.5° under steady-state conditions, providing a high-precision phase reference for subsequent grid-connected control.

[0128] Step 203, as a core pre-processing step in grid-connected inverter control, utilizes the SOGI-PLL architecture to achieve rapid and accurate acquisition of the grid synchronization phase θ. This provides a unified and high-precision phase reference for subsequent grid-connected current closed-loop regulation, phase shift and switching frequency calculation, and secondary-side extended phase shift modulation. It fundamentally ensures that the grid-connected current and grid voltage are in phase and frequency match, achieving unity power factor grid connection and meeting the core requirements of grid connection standards. Simultaneously, the SOGI orthogonalization processing architecture used in step 203 effectively filters out the effects of harmonic interference, DC bias, and waveform distortion in the grid voltage. Combined with the closed-loop regulation mechanism of the phase-locked loop, it possesses excellent adaptability to grid operating conditions. Even under complex grid conditions such as grid voltage fluctuations, frequency shifts, and harmonic distortion, it can still stably output accurate synchronization phase signals, avoiding problems such as grid-connected current distortion, substandard power factor, and even grid-connected protection shutdown caused by phase-locking inaccuracies. This significantly improves the operational stability and reliability of the power converter under complex grid conditions.

[0129] S204: Based on grid-connected current I g Compared with the preset grid-connected current reference value I ref Perform closed-loop regulation to obtain the shift ratio adjustment ∆D ps,n .

[0130] Grid-connected current reference value I refThe active power component target amplitude of the grid-connected current, calculated based on the system's preset grid-connected active power target and grid rated parameters, is the core reference for grid-connected current closed-loop control. Its value can be dynamically adjusted according to the user's grid-connected power demand, photovoltaic output status, and energy storage battery SOC status, directly determining the amount of active power delivered by the power converter to the grid.

[0131] The Parker transform is a coordinate transformation algorithm that converts a sinusoidal AC grid-connected current signal in a stationary coordinate system into a DC component in a synchronous rotating coordinate system, based on the grid synchronization phase θ. In single-phase grid-connected systems, the Parker transform can convert AC tracking control into DC error-free control, making it a core algorithm for achieving high-precision closed-loop regulation of grid-connected current.

[0132] Closed-loop regulation refers to the control process of comparing the actual output value of the controlled object with the preset reference value, and performing closed-loop calculations through the controller based on the deviation between the two, and outputting the corresponding adjustment amount to eliminate the tracking deviation. The core objective of closed-loop regulation in this step is to make the active component of the actual grid-connected current accurately track the grid-connected current reference value, so as to achieve precise control of grid-connected power and unity power factor grid connection.

[0133] The adjustment amount ∆D of the shift ratio ps,n The final output of the closed-loop controller in this step is the dynamic correction and compensation amount for the nominal shift ratio of the primary and secondary sides of the dual active bridge converter. Its value is directly related to the tracking deviation of the grid-connected current and is used to offset the grid-connected current tracking error caused by external disturbances such as grid voltage fluctuations, device parameter drift, and load condition changes. It is the core adjustment variable for achieving zero steady-state error control of the grid-connected current.

[0134] In this embodiment of the invention, a single-phase grid-connected current closed-loop control architecture based on a synchronous rotating coordinate system is adopted. First, the controller receives the grid-connected current I. g To address the issue of direct Parker transformation in single-phase systems, and to synchronize the phase θ with the grid, a second-order generalized integrator (SOGI) is used to measure the grid-connected current I. g Perform orthogonal reconstruction to generate the actual grid-connected current I. g The α-axis current signal i_gα, which is in phase and frequency, and the β-axis orthogonal current signal i_gβ, which is strictly out of phase with i_gα by 90°, can effectively filter out high-frequency harmonics and switching noise in the grid-connected current, providing a high signal-to-noise ratio input signal for subsequent coordinate transformation.

[0135] Subsequently, based on the grid synchronization phase θ, the controller performs a Parker transformation on the current signals in the two orthogonal stationary coordinate systems, converting them into DC components in the synchronous rotating coordinate system, where the d-axis component i d The active component of the grid-connected current directly corresponds to the active power delivered by the system to the grid, with the q-axis component i.q The reactive component of the grid-connected current directly corresponds to the reactive power output of the system. Through this coordinate transformation, the originally complex sinusoidal AC quantity tracking control is transformed into DC quantity zero steady-state error control, which greatly reduces the difficulty of implementing closed-loop control.

[0136] In this embodiment of the invention, after completing the coordinate transformation, the controller will perform dual-loop decoupling regulation, where the active power control loop is the core control loop and the reactive power control loop is the auxiliary control loop. In the active power control loop, the controller will apply the active power component i obtained from the Park transformation... d Compared with the preset grid-connected current reference value I ref The difference is calculated to obtain the active current tracking error. In the reactive power control loop, the reactive power component i is... q The reactive current tracking error is obtained by subtracting it from the zero reference value, thereby achieving the control objective of grid connection with unity power factor. The two tracking errors are fed into their respective proportional-integral (PI) controllers for closed-loop calculations. The output of the active-loop PI controller is the ratio shift adjustment ∆D. ps,n The output of the reactive power loop PI controller is used for auxiliary regulation of reactive power compensation in the power grid.

[0137] In this embodiment of the invention, the PI controller is equipped with anti-integral saturation limiting and variable parameter adjustment functions. When the grid-connected current tracking deviation is large, a large proportional parameter is used to improve the dynamic response speed; when the tracking deviation is small, a small parameter is used to improve the steady-state control accuracy. Simultaneously, the limiting function prevents system oscillations caused by controller output saturation. Finally, the controller adjusts the calculated shift ratio ∆D. ps,n The current is output in real time to the subsequent shift ratio calculation stage to dynamically correct and compensate the nominal shift ratio, ensuring that the grid-connected current always accurately tracks the reference value.

[0138] This invention transforms the tracking control of AC grid-connected current into zero steady-state error control of DC quantity through synchronous rotating coordinate transformation. This perfectly adapts to the integrated control architecture of the single-stage power conversion topology of this invention, achieving high-precision, fast-response closed-loop regulation of the grid-connected current and ensuring that the grid-connected power quality meets grid standards from a core perspective. Simultaneously, this invention directly converts the output of the closed-loop regulation into a phase-shift adjustment, fully adapting to the subsequent phase-shift frequency converter control logic of this invention. No additional intermediate conversion stage is required, significantly simplifying the grid-connected control link and effectively reducing the controller's computational load. Furthermore, by dynamically correcting and compensating for the nominal phase-shift, it solves the problems of insufficient control accuracy caused by nonlinearity between grid-connected current and control quantity, device parameter drift, and grid disturbances in single-stage bridge arm reuse topologies, achieving zero steady-state error tracking of the grid-connected current under all operating conditions. In addition, this invention achieves independent regulation of active and reactive power through decoupling control of the dq axis. While ensuring unity power factor grid connection, it is compatible with the grid's reactive power compensation requirements, significantly improving the system's grid operating condition adaptability.

[0139] S205: Based on the output voltage V of the photovoltaic module pv The preset maximum switching frequency threshold f sw,max and grid-connected current reference value I ref Based on a pre-established mathematical model of grid-connected current, the nominal shift ratio D between the primary and secondary sides of the dual active bridge converter is calculated. ps,n .

[0140] Maximum switching frequency threshold f sw,max The maximum allowed switching frequency of the power switching transistor in the power converter within its safe operating range is determined by a combination of factors including the switching loss characteristics of the transistor, the maximum allowable junction temperature, electromagnetic compatibility (EMC) standard requirements, and heat dissipation design capabilities. It is the core upper limit constraint parameter of the frequency conversion control logic of this invention and serves as the benchmark value for calculating the nominal shift ratio, ensuring that the switching devices always operate within a safe and reliable operating range.

[0141] The pre-established grid-connected current mathematical model refers to the quantitative mathematical relationship expression between the grid-connected current amplitude and various control quantities and circuit parameters, established by the time-domain analysis of the circuit's full operating modes and the derivation of the variation law of the transformer's equivalent leakage inductance current. This model is the core theoretical basis for realizing open-loop feedforward control and linear regulation of the grid-connected current, and can accurately quantify the correspondence between the grid-connected current and control quantities such as shift ratio and switching frequency under different operating conditions.

[0142] In one possible implementation, the pre-established mathematical model of grid-connected current is expressed as follows:

[0143] (2)

[0144] Among them, i g V is the grid-connected current, n is the turns ratio of the isolation transformer, and V pv D is the input voltage of the photovoltaic module. b Let Ls be the target duty cycle, and f be the equivalent leakage inductance of the transformer. sw D is the switching frequency. ps1 and D ps2 Based on the target duty cycle D b The calculated phase shift compensation value;

[0145] D ps1 and D ps2 The expression is:

[0146] (3)

[0147] Nominal displacement compared to D ps,n This refers to the target grid-connected current reference value I under ideal steady-state conditions, without considering nonlinear interference factors such as grid voltage disturbances, device parameter drift, and line losses. ref The nominal reference value of the shift ratio needs to be set between the primary and secondary output square wave voltages of the dual active bridge converter; its value is the core basis for subsequent closed-loop regulation correction and actual shift ratio calculation, and directly determines the nominal grid-connected power transmission capability of the power converter.

[0148] The formula for calculating the nominal displacement ratio Dps,n is:

[0149] (4)

[0150] Among them, I ref This is the reference value for grid-connected current. is the maximum switching frequency parameter, Ls is the equivalent leakage inductance of the transformer, Vpv is the input voltage of the photovoltaic module, and n is the transformer turns ratio of the isolation transformer.

[0151] The phase shift ratio refers to the ratio of the phase difference between the square wave voltage output by the primary-side full-bridge switching circuit and the square wave voltage output by the secondary-side bidirectional switching circuit in a dual active bridge converter to half a switching cycle. It is the core power control quantity of the dual active bridge converter, and its magnitude and sign directly determine the magnitude and direction of power transfer between the primary and secondary sides.

[0152] In this embodiment of the invention, based on a pre-established mathematical model of grid-connected current, the nominal shift ratio D is completed. ps,n The precise feedforward calculation ensures that the entire calculation process is strictly synchronized with the grid-connected current closed-loop control cycle, providing real-time updated reference parameters for subsequent control stages. First, the controller acquires and retrieves basic parameters in real time, receiving the photovoltaic module output voltage V... pvand grid-connected current reference value I ref On the other hand, it retrieves pre-calibrated circuit parameters from the controller's storage unit, including the turns ratio n of the isolation transformer, the equivalent leakage inductance Ls, and the preset maximum switching frequency threshold f. sw,max .

[0153] Simultaneously, a pre-established mathematical model of the grid-connected current is invoked. This model is derived through modal analysis of the topology of this invention and characterizes the grid-connected current I. g With photovoltaic output voltage V pv Target duty cycle D b Compared to D ps Switching frequency f sw The quantitative relationship between the circuit's inherent parameters and the switching frequency. In this embodiment of the invention, to simplify the calculation process of the nominal shift ratio, the mathematical model is simplified based on the upper limit constraint of the switching frequency, and the maximum switching frequency threshold f is set. sw,max Substituting a fixed reference value into the model eliminates the influence of the switching frequency variable on the solution process, and directly establishes the nominal shift ratio D. ps,n With grid-connected current reference value I ref Photovoltaic output voltage V pv The linear correspondence between them reduces the computational load on the controller.

[0154] In this embodiment of the invention, the controller performs real-time calculation of the nominal shift ratio based on a simplified mathematical model and is optimized for adaptability to operating conditions across the entire power range. First, the controller substitutes the acquired real-time parameters into the nominal shift ratio calculation formula to calculate the nominal shift ratio D, which matches the current grid-connected current reference value and photovoltaic operating conditions. ps,n Meanwhile, to address the difference in control accuracy under light and heavy load conditions, this embodiment of the invention adopts a tiered setting method for the maximum switching frequency threshold, presetting a first maximum switching frequency threshold f corresponding to the light load condition. sw,max1 The second maximum switching frequency threshold f corresponding to heavy load conditions sw,max2 When the grid-connected current reference value I ref When the current is less than or equal to the preset current threshold, f is used. sw,max1 Solving for the nominal displacement ratio of light load D ps,n1 , when I ref When the current exceeds the preset current threshold, f is used. sw,max2 Solving the nominal displacement ratio of heavy load D ps,n2 This ensures the accuracy of the nominal displacement ratio calculation across the entire power range.

[0155] Furthermore, the controller compares the calculated nominal displacement with D. ps,nA reasonable limiting range was set, with the upper and lower limits determined based on the phase shift boundary values ​​in the pre-established mathematical model. This prevents the calculated nominal shift ratio from exceeding the effective adjustment range, which could lead to problems such as grid-connected current runaway and hard switching of the switching transistor in subsequent control stages. Ultimately, the controller will adjust the calculated and limited nominal shift ratio to D. ps,n The data is output in real time to subsequent steps, providing an accurate open-loop reference for the actual displacement calculation.

[0156] This invention, through a pre-established mathematical model of the grid-connected current, pre-calculates the nominal shift ratio reference value that matches the target grid-connected current. This provides a precise open-loop control basis for subsequent closed-loop regulation, significantly reducing the computational burden and adjustment range of closed-loop regulation. It effectively improves the dynamic response speed and steady-state control accuracy of grid-connected current control, avoiding problems such as tracking lag and overshoot oscillation caused by relying solely on closed-loop regulation. Furthermore, this invention uses the maximum switching frequency threshold as the calculation benchmark, incorporating the safety constraint of the switching frequency into the nominal shift ratio calculation process in advance. This fundamentally ensures that the operating frequency of the switching transistors never exceeds the safe upper limit during subsequent frequency conversion control, avoiding problems such as device overheating, excessive losses, and electromagnetic compatibility issues caused by excessively high switching frequencies. This significantly improves the operational reliability of the power converter.

[0157] In embodiments of the present invention, such as Figure 3 As shown, the equivalent leakage inductance current i of the transformer at different stages is derived. Ls rate of change di Ls The / dt expression is as follows:

[0158] (5)

[0159] Based on i Ls Symmetry about the 0 axis within a switching cycle, according to i Ls The average value over half a switching cycle and i g The relationship can be used to calculate i. g The expression is as follows:

[0160] (6)

[0161] Among them, T sw For the switching period, D ps1 and D ps2 The expression is as follows:

[0162] (7)

[0163] According to i g The expression, using V pv Maximum switching frequency f sw,maxand the set grid-connected current reference value I ref Conversely, we can obtain the nominal shift ratio D corresponding to a certain grid-connected current. ps,n Set f according to the magnitude of the grid-connected current. sw,max1 and f sw,max2 D is calculated using the following formula. ps,n1 and D ps,n2 .

[0164] (8)

[0165] (9)

[0166] Among them, L s Let n be the equivalent leakage inductance of the transformer, and n be the transformer turns ratio.

[0167] S206: Shift the nominal value relative to D ps,n Compared to the adjustment amount ∆D ps,n Superimposed, combined with the target duty cycle D b Synchronize with the grid phase θ to determine the actual displacement ratio D ps Compared to actual movement D ps Matching real-time switching frequency f sw .

[0168] The controller is based on the target duty cycle D. b The phase-shifting boundary value D is calculated using a predefined formula. ps1 and D ps2 This determines the effective adjustment range of the downward shift ratio under the current operating condition. Based on this, the controller first adjusts the nominal shift ratio D... ps,n Compared to the adjustment amount ∆ Dps,n By superimposing these values, the total reference value of the shift ratio is obtained, and then the grid-connected current reference value I is added. ref With the preset current threshold I ref,th By comparing the results, the automatic switching between light-load and heavy-load modes is completed. Substituting the values ​​into the corresponding mode's calculation formula and combining the absolute value of the sine wave of the grid synchronization phase |sinθ|, the real-time actual shift ratio D in each control cycle is calculated. ps At the same time, the solution obtained D ps Implement range limiting to ensure it always stays within D. ps1 With D ps2 Within the effective adjustment range between them, avoid problems such as grid current runaway and reverse power transmission caused by the shift ratio exceeding the limit.

[0169] In this embodiment of the invention, the real-time switching frequency f sw Compared with actual movement D psA synchronous linkage solution method is adopted to ensure complete matching of the two control variables, achieving linear control of the grid-connected current. The controller completes the actual displacement phase D... ps After solving, immediately set the current D ps Numerical value, phase-shifting boundary value D ps1 and D ps2 Target duty cycle D b Substituting the maximum switching frequency threshold that matches the control mode into the corresponding formula, the result is obtained that is consistent with the current D. ps Fully adapted real-time switching frequency fs w In light-load mode, the switching frequency varies with the actual displacement compared to D. ps With D ps1 The difference changes positively; under heavy load mode, the switching frequency changes with D. ps2 Compared with actual movement D ps The difference changes positively. Through this linkage design, the original quadratic function relationship in the pre-established grid-connected current mathematical model can be transformed into a linear relationship between the grid-connected current and the shift ratio adjustment, thus completely eliminating the accuracy loss caused by control nonlinearity.

[0170] At the same time, the controller calculates the real-time switching frequency f. sw Upper and lower limit constraints were set. The upper limit was the maximum switching frequency threshold for the corresponding mode, and the lower limit was the preset minimum switching frequency threshold. This avoided problems such as excessive switching losses, junction overheating, and electromagnetic compatibility issues caused by excessively high switching frequencies, as well as problems such as excessive grid-connected current harmonic distortion and excessively large filter device size caused by excessively low switching frequencies. Finally, the controller synchronously calculated the actual shift ratio to D. ps Real-time switching frequency f sw , with target duty cycle D b The synchronous output is sent to the subsequent modulation stage to provide precise core control parameters for the generation of the drive signal.

[0171] When the grid-connected current reference value I ref Less than or equal to the preset current threshold I ref,th When switching to light load mode, the actual displacement is compared to D. ps With real-time switching frequency f sw for:

[0172] (10)

[0173] Among them, D ps1 and D ps2 The phase shift compensation value is calculated based on the target duty cycle. The shift ratio adjustment amount, This represents the maximum switching frequency under light load. Let |sinθ| be the target duty cycle, and |sinθ| be the absolute value of the sine of the grid synchronization phase θ. Compared to the nominal displacement under light load mode;

[0174] When the grid-connected current reference value I ref Greater than the current threshold I ref,th When switching to overload mode, the actual displacement is compared to D. ps With real-time switching frequency f sw for:

[0175] (11)

[0176] in, This represents the maximum reload switching frequency. Compared to the nominal displacement in heavy-load mode.

[0177] S207: Based on target duty cycle D b The actual transfer compared to D ps and real-time switching frequency f sw The secondary-side extended phase-shift modulation strategy is used to generate drive signals for the primary-side full-bridge switching circuit and the secondary-side switching circuit, thereby controlling the power converter to synchronously achieve photovoltaic maximum power point tracking and unity power factor grid-connected inversion.

[0178] Secondary-side extended phase-shift modulation refers to a dedicated modulation strategy adapted to the single-stage topology and bidirectional switching half-bridge structure of the bridge arm reuse in this invention. Unlike the fixed-frequency phase-shift modulation of traditional dual active bridges, this strategy uses the grid synchronous phase as a reference and adopts differentiated driving logic for the positive and negative half-cycles of the grid voltage. At the same time, it links and matches the real-time changing duty cycle, phase shift, and switching frequency. It is the core modulation method for realizing DC-AC inverter conversion and unity power factor grid connection under a single-stage topology.

[0179] In this embodiment of the invention, based on the core control parameters calculated in the preceding steps, a secondary-side extended phase-shift modulation strategy is used to synchronously generate the full-path drive signals for both the primary-side full-bridge switching circuit and the secondary-side bidirectional switching circuit. The entire modulation process is synchronized with the real-time switching frequency f. sw The switching cycles are strictly synchronized to ensure that the drive signal for each switching cycle is perfectly matched with the current control parameters.

[0180] The controller operates at a real-time switching frequency f sw Based on this, the period and counting reference of the PWM modulation are dynamically updated to ensure that the switching frequency of the drive signal is consistent with the previously calculated f. sw Completely consistent; then based on the target duty cycle D b This generates drive signals for the four switches on the primary side of the full-bridge, where the duty cycle of the drive signals for the second switch Q2 and the fourth switch Q4 is D. bFurthermore, the two drive signals are 180° out of phase, enabling the two boost inductors to operate in alternating parallel mode, thus reducing photovoltaic input current ripple. Simultaneously, the primary-side first switch Q1 and the second switch Q2 employ complementary conduction logic, as do the third switch Q3 and the fourth switch Q4. A preset dead time is inserted at the switching moment of each complementary signal to prevent bridge arm shoot-through faults.

[0181] In this embodiment of the invention, the drive signal of the primary-side full bridge simultaneously undertakes two core functions. On the one hand, it works with the boost inductor component to achieve interleaved parallel Boost conversion and complete photovoltaic MPPT control; on the other hand, it serves as the primary-side square wave output of the dual active bridge converter, working with the secondary-side drive signal to achieve phase-shifted power transmission. This truly realizes the functional multiplexing of a single bridge arm, eliminating the need to generate independent drive signals for the two functions separately.

[0182] In this embodiment of the invention, the generation of the secondary-side drive signal strictly follows the secondary-side extended phase-shift modulation strategy. Using the grid synchronization phase θ as a reference, differentiated drive logic is employed for the positive and negative half-cycles of the grid voltage, and the phase difference between the secondary-side drive signal and the primary-side drive signal is strictly matched to the actual phase shift ratio D. ps First, the controller determines the current power frequency half-cycle of the grid voltage in real time based on the grid synchronization phase θ. When the grid synchronization phase θ is in the range of 0~π, it is determined to be the positive half-cycle of the grid voltage. At this time, the controller keeps the sixth switch Q6 and the eighth switch Q8 on the secondary side continuously conducting to provide a continuous commutation path for the current in the positive half-cycle of the grid. The fifth switch Q5 and the seventh switch Q7 adopt complementary conduction drive logic, and the switching cycle of the two drive signals is completely synchronized with the primary side drive signal.

[0183] Simultaneously, using the rising edge of the drive signal of the fourth switch Q4 as the phase reference, the phase difference between the rising edge of the drive signal of the fifth switch and this reference is set to a value matching the actual phase shift ratio Dps, thus accurately realizing phase shift control between the primary and secondary sides. When the grid synchronization phase θ is in the range of π to 2π, it is determined to be the negative half-cycle of the grid voltage. At this time, the fifth switch Q5 and the seventh switch Q7 on the secondary side are kept continuously conducting to provide a continuous commutation path for the current in the negative half-cycle of the grid. The sixth switch Q6 and the eighth switch Q8 adopt complementary conduction drive logic. At the same time, using the rising edge of the drive signal of the fourth switch Q4 as the phase reference, the phase difference between the rising edge of the drive signal of the eighth switch Q8 and this reference is set to a value matching the actual phase shift ratio Dps. ps The matched values ​​complete the phase shift control for the negative half-cycle.

[0184] In this embodiment of the invention, the controller performs synchronization verification and safety protection processing while generating drive signals to ensure the accuracy of the drive signals and the safety of circuit operation. First, the controller performs real-time verification of the phase synchronization of the primary and secondary drive signals to ensure that the deviation between the actual executed value and the calculated value of the shift ratio is less than 1%, avoiding problems such as grid-connected power fluctuations and current distortion caused by phase deviations. Simultaneously, for the reverse series structure of the secondary bidirectional switches, the controller performs synchronization calibration on the two drive signals of each bidirectional switch to ensure that the two reverse series switches are completely synchronized in turning on and off, preventing damage to the devices due to reverse overvoltage. Furthermore, the controller also sets up a fault-blocking linkage mechanism for the drive signals. When the system detects fault states such as overcurrent, overvoltage, overtemperature, or grid anomalies, it can immediately block the drive signals of all switches within one switching cycle, forcing all switches to turn off, achieving rapid circuit protection and preventing the fault range from expanding. Finally, the controller outputs the generated full-path drive signals to the hardware drive circuit, which, after power amplification, drives the power switches to operate, controlling the power converter to synchronously achieve photovoltaic maximum power point tracking and unity power factor grid-connected inversion.

[0185] Based on the above steps S201-S207, the controller used to perform the above steps S201-S207 is controlled as follows: Figure 4 As shown.

[0186] Furthermore, to verify the effectiveness of the present invention, [the following is conducted]: Figure 1 The micro-inverter circuit shown was simulated and verified. The circuit simulation parameters were set as follows: input voltage V pv =25-60V, input boost inductors L1 and L2 are 50μH, input capacitor C1=2200μF, nominal voltage of energy storage battery V bat =72V, battery bus capacitance C2=3300μF, transformer turns ratio n=1.5, equivalent leakage inductance L s =20μH, Output filter inductor L f =1mH, filter capacitor C f =2.2μF, grid voltage V g =220Vrms, mains frequency 50Hz, rated power 750W, switching frequency f under frequency converter control sw The range is 70-170kHz.

[0187] After the micro-inverter is stably connected to the grid, the simulation results are as follows: The simulated voltage and current waveforms of the photovoltaic module are as follows. Figure 5 As shown, V can be seen at this time pv The voltage is approximately 41V and at its maximum power point, with a power output of approximately 450W. The simulated voltage and current waveforms of the energy storage battery are as follows: Figure 6As shown, the battery is currently discharging, outputting approximately 300W of power. The simulated voltage and current waveforms of the power grid are as follows: Figure 7 As shown, the peak grid-connected current is approximately 4.8A, and the micro-inverter is transmitting energy to the grid at a rated power of 750W. The current i of the input-side boost inductor... L1 i L2 The current i of the transformer equivalent leakage inductance Ls like Figure 8 As shown.

[0188] In summary, the single-stage micro inverter circuit topology and its control method with portable energy storage proposed in this invention are effective and feasible.

[0189] The above are some specific implementations of the control method provided in the embodiments of the present invention. Based on this, the present invention also provides a corresponding device. The control device provided in the embodiments of the present invention will be described below from the perspective of functional modularity. The control device includes a sampling unit, a memory, and a processor. The sampling unit is used to collect the output voltage and output current of the photovoltaic module, and the grid voltage and grid-connected current on the grid side; the memory is used to store a computer program; the processor is used to execute the computer program in the memory to implement the control method of the power converter described in any of the above embodiments.

[0190] This invention also provides corresponding devices and computer storage media for implementing the solutions provided in this invention.

[0191] The device includes a memory and a processor. The memory is used to store instructions or code, and the processor is used to execute the instructions or code to enable the device to perform the control method of the power converter according to any embodiment of the present invention.

[0192] The computer storage medium stores code, and when the code is run, the device running the code implements the data push method described in any embodiment of the present invention.

[0193] In the embodiments of this invention, the terms "first" and "second" are used only as name identifiers and do not represent the order of first and second.

[0194] The implementation of this invention is not limited to the embodiments described above. That is, the control method of this invention is also applicable when the secondary side of the DAB adopts a full-bridge topology. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of this invention shall be considered equivalent substitutions and are included within the protection scope of this invention.

Claims

1. A control method for a power converter, characterized in that, The method is applied to the power converter, which includes an interleaved parallel boost circuit and a dual active bridge converter; the interleaved parallel boost circuit includes a boost inductor component and a primary-side full-bridge switching circuit, and the dual active bridge converter includes an isolation transformer, a secondary-side bidirectional switching circuit and the primary-side full-bridge switching circuit; the interleaved parallel boost circuit and the dual active bridge converter share the primary-side full-bridge switching circuit. The midpoint of the bridge arm of the primary-side full-bridge switching circuit is connected to the output terminal of the photovoltaic module through the boost inductor component, and the DC bus terminal of the primary-side full-bridge switching circuit is connected in parallel to the energy storage battery. The primary winding of the isolation transformer is connected to the midpoint of the bridge arm of the primary full-bridge switching circuit, the secondary winding of the isolation transformer is connected to the AC terminal of the secondary bidirectional switching circuit, and the output terminal of the secondary bidirectional switching circuit is connected to the power grid. The method includes: Real-time acquisition of the photovoltaic module's output voltage, output current, grid voltage, and grid-connected current; Based on the output voltage and output current of the photovoltaic module, the target duty cycle of the primary-side full-bridge switching circuit is calculated by the maximum power point tracking algorithm to control the maximum power transfer from the photovoltaic module to the energy storage battery. Obtain the grid synchronization phase based on grid voltage; Closed-loop regulation is performed based on the grid-connected current and the preset grid-connected current reference value to obtain the shift ratio regulation amount; Based on the output voltage of the photovoltaic module, the preset maximum switching frequency threshold, and the grid-connected current reference value, the nominal shift ratio between the primary and secondary sides of the dual active bridge converter is calculated based on the pre-established grid-connected current mathematical model. The nominal shift ratio is superimposed with the shift ratio adjustment amount, and combined with the target duty cycle and the grid synchronization phase, to determine the real-time switching frequency that matches the actual shift ratio; Based on the target duty cycle, the actual phase shift ratio, and the real-time switching frequency, a secondary-side extended phase shift modulation strategy is used to generate drive signals for the primary-side full-bridge switching circuit and the secondary-side switching circuit, thereby controlling the power converter to synchronously achieve photovoltaic maximum power point tracking and unity power factor grid-connected inversion.

2. The method according to claim 1, characterized in that, The target duty cycle of the primary-side full-bridge switching circuit is calculated using the maximum power point tracking algorithm based on the output voltage and current of the photovoltaic module, including: The input power of the photovoltaic module is calculated based on the output voltage and the output current. The target duty cycle value that maximizes the input power of the photovoltaic module is determined by perturbing the duty cycle. The relationship between the duty cycle and the output voltage satisfies: ； Among them, V pv For the output voltage, D b V is the duty cycle. bat This refers to the voltage of the energy storage battery.

3. The control method according to claim 1, characterized in that, The method of obtaining the grid synchronization phase based on grid voltage includes: The grid voltage is decomposed into two orthogonal voltage signals with a 90° phase difference by a second-order generalized integrator. The grid synchronization phase is calculated using a single-phase phase-locked loop based on the two orthogonal voltage signals.

4. The control method according to claim 1, characterized in that, The closed-loop adjustment based on the grid-connected current and a preset grid-connected current reference value to obtain the shift ratio adjustment amount includes: The grid-connected current is subjected to Park transformation using the grid synchronization phase to obtain the active and reactive components of the grid-connected current in the dq rotating coordinate system. The active component is controlled by a proportional-integral controller to track the grid-connected current reference value, and the shift ratio adjustment is obtained by outputting the output. The reactive component is controlled to track the 0 value by a proportional-integral controller, thereby achieving unity power factor grid connection.

5. The control method according to claim 1, characterized in that, In the pre-established mathematical model of grid-connected current, the expression for the grid-connected current is: ； Among them, i g Let n be the grid-connected current, n be the turns ratio of the isolation transformer, and V be the voltage. pv D is the input voltage of the photovoltaic module. b Let Ls be the target duty cycle, Ls be the transformer equivalent leakage inductance, and f be the value of the duty cycle. sw D is the switching frequency. ps1 and D ps2 Based on the target duty cycle D b The calculated phase shift compensation value; D ps1 and D ps2 The expression is: 。 6. The control method according to claim 5, characterized in that, The determination of the real-time switching frequency that matches the actual shift ratio includes: When the grid-connected current reference value is less than or equal to the preset current threshold, the system switches to light-load mode. The actual shift ratio compared to the real-time switching frequency is: ； Among them, D ps1 and D ps2 The phase shift compensation value is calculated based on the target duty cycle. The shift ratio adjustment amount, This represents the maximum switching frequency under light load. Let |sinθ| be the target duty cycle, and |sinθ| be the absolute value of the sine of the grid synchronization phase θ. Compared to the nominal displacement under light load mode; When the grid-connected current reference value is greater than the current threshold, the system switches to heavy load mode, and the actual shift ratio compared to the real-time switching frequency is: ； in, This represents the maximum reload switching frequency. Compared to the nominal displacement in heavy-load mode.

7. The method according to claim 1, characterized in that, In the secondary-side extended phase-shift modulation strategy, the driving logic of the primary-side full-bridge switching circuit is specifically as follows: The target duty cycle is used as the conduction duty cycle of the drive signals of the two lower bridge arm switches in the primary-side full-bridge switching circuit to control the two lower bridge arm switches; wherein, the drive signals of the two lower bridge arm switches are 180° out of phase; in the primary-side full-bridge switching circuit, the upper bridge arm switches and the lower bridge arm switches of the same bridge arm are complementary in conduction. In the secondary-side extended phase-shift modulation strategy, the driving logic of the secondary-side switching circuit is specifically as follows: When the grid voltage is in the positive half-cycle, the lower transistors of the two sets of bidirectional switches in the secondary-side switching circuit are kept on, the upper transistors of the two sets of bidirectional switches are complementary and on, and the phase difference between the driving signal of the lower transistor of the right bridge arm of the primary-side full-bridge switching circuit and the upper transistor of the upper bridge arm in the secondary-side switching circuit matches the actual shift ratio. When the grid voltage is in the negative half-cycle, the upper transistors of the two sets of bidirectional switches in the secondary-side switching circuit remain on, the lower transistors of the two sets of bidirectional switches are complementary and on, and the phase difference between the driving signal of the lower transistor of the right bridge arm of the primary-side full-bridge switching circuit and the lower transistor of the lower bridge arm in the secondary-side switching circuit matches the actual shift ratio.

8. A power converter, characterized in that, The power converter includes an interleaved parallel boost circuit, a dual active bridge converter, and a controller; the interleaved parallel boost circuit includes a boost inductor component and a primary-side full-bridge switching circuit; the dual active bridge converter includes an isolation transformer, a secondary-side bidirectional switching circuit, and the primary-side full-bridge switching circuit; the interleaved parallel boost circuit and the dual active bridge converter share the primary-side full-bridge switching circuit. The midpoint of the bridge arm of the primary-side full-bridge switching circuit is connected to the output terminal of the photovoltaic module through the boost inductor component, and the DC bus terminal of the primary-side full-bridge switching circuit is connected in parallel to the energy storage battery. The primary winding of the isolation transformer is connected to the midpoint of the bridge arm of the primary full-bridge switching circuit, the secondary winding of the isolation transformer is connected to the AC terminal of the secondary bidirectional switching circuit, and the output terminal of the secondary bidirectional switching circuit is connected to the power grid. The controller is used to execute the control method of the power converter as described in any one of claims 1-7.

9. A control device for a power converter, characterized in that, The control device includes a sampling unit, a memory, and a processor; the sampling unit is used to collect the output voltage and output current of the photovoltaic module, and the grid voltage and grid-connected current on the grid side; the memory is used to store a computer program; the processor is used to execute the computer program in the memory to implement the control method of the power converter according to any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which, when loaded and executed by a processor, implements the control method of the power converter according to any one of claims 1-7.

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