Single-phase photovoltaic energy storage converter and control method thereof

Abstract

The application discloses a single-phase photovoltaic energy storage converter and a control method thereof, relates to the technical field of photovoltaic charging and discharging control, and comprises a front-stage bidirectional power conversion unit, a rear-stage single-phase inversion unit, an integrated main control unit and a wide-voltage adaptation control unit. The input end of the front-stage bidirectional power conversion unit is used for being connected with a direct-current power supply, and the output end is connected with the direct-current bus end of the rear-stage single-phase inversion unit. The output end of the rear-stage single-phase inversion unit is used for being connected with a power grid or a load. The integrated main control unit is electrically connected with the front-stage bidirectional power conversion unit, the rear-stage single-phase inversion unit and the wide-voltage adaptation control unit respectively, and is configured to perform integrated collaborative control of double-mode switching, power conversion, battery management and energy scheduling. The wide-voltage adaptation control unit is connected with the front-stage bidirectional power conversion unit, and the front-stage bidirectional power conversion unit is configured to work in full-condition soft switching within a wide direct-current input voltage range.

Description

Technical Field

[0001] This application relates to the field of photovoltaic charging and discharging control technology, and in particular to a single-phase photovoltaic energy storage converter and its control method. Background Technology

[0002] Driven by the "dual-carbon" strategy and the popularization of distributed energy, residential photovoltaic energy storage systems have entered a stage of large-scale promotion. As the core energy conversion device connecting photovoltaic modules, energy storage batteries, the power grid, and loads, the energy storage converter's operating efficiency, voltage adaptability, integration, and control response speed directly determine the safety, reliability, and economy of residential photovoltaic energy storage systems. As residential scenarios increasingly demand flexibility in battery configuration, system miniaturization, and high efficiency, traditional single-phase energy storage converters can no longer meet the application requirements of wide voltage compatibility, high frequency and high efficiency, and integrated collaborative control.

[0003] Currently, most residential single-phase energy storage converters use silicon-based IGBTs or MOSFETs as power switching devices. Due to the inherent limitations of these devices—poor reverse recovery characteristics and high switching losses—the switching frequency is typically restricted to below 20kHz. This results in large magnetic components, low power density, and a maximum overall efficiency of only around 96%. Long-term operation leads to severe heat generation and compromised reliability. Furthermore, existing products typically have a DC-side voltage range of 200V to 400V, supporting only battery packs with a fixed number of cells. They are incompatible with a wide DC voltage input range of 120V to 270V, making it difficult to adapt to voltage fluctuations in different battery specifications and distributed photovoltaic modules. This results in poor system configuration flexibility and high adaptation costs.

[0004] Existing photovoltaic-storage systems generally adopt an architecture where the energy storage converter, battery management system, and energy management system are built separately. Each of these three units is equipped with an independent controller, sampling circuit, communication module, and protection unit, resulting in high hardware redundancy, a large number of components, and high overall cost. The modules communicate with each other via CAN or RS485 bus, which results in communication delays of hundreds of milliseconds. This leads to slow system protection response, low precision of coordinated control, and easy disruption of protection timing under fault conditions, causing safety risks such as battery overcharging, over-discharging, and power surges. This fails to meet the requirements of high reliability, high safety, and fast response in residential applications. Summary of the Invention

[0005] In view of this, this application provides a single-phase photovoltaic energy storage converter and its control method, which can meet the requirements of high reliability, high safety and fast response in residential scenarios.

[0006] According to a first aspect of this application, a single-phase photovoltaic energy storage converter is provided, comprising: a front-end bidirectional power conversion unit, a back-end single-phase inverter unit, an integrated main control unit, and a wide voltage adaptation control unit. The input terminal of the front-stage bidirectional power conversion unit is used to connect to a DC power supply, and the output terminal is connected to the DC bus terminal of the rear-stage single-phase inverter unit. The output terminal of the subsequent single-phase inverter unit is used to connect to the power grid or load; The integrated main control unit is electrically connected to the front-end bidirectional power conversion unit, the rear-end single-phase inverter unit, and the wide voltage adaptation control unit. The integrated main control unit is configured to perform integrated collaborative control of dual-mode switching, power conversion, battery management, and energy scheduling. The wide voltage adaptation control unit is connected to the front-end bidirectional power conversion unit, which is configured to operate soft-switching under all operating conditions within a wide DC input voltage range.

[0007] Optionally, the front-end bidirectional power conversion unit is a full-bridge symmetrical bidirectional LLC resonant converter, including a primary-side full-bridge circuit, a secondary-side full-bridge circuit, a resonant cavity, and a high-frequency transformer. The primary winding of the high-frequency transformer is connected to the primary full-bridge circuit, and the secondary winding is connected to the secondary full-bridge circuit. The input terminal of the primary-side full-bridge circuit forms a DC input side, which is compatible with 120V~270V DC voltage input. The output terminal of the secondary full-bridge circuit is connected to the 400V rated DC bus. The resonant cavity is composed of a resonant inductor, a resonant capacitor, and a magnetizing inductor. The ratio of the magnetizing inductor to the resonant inductor is k=4, and the quality factor Q=0.3~0.8, so that the voltage gain range of the converter covers 1.48~3.33.

[0008] Optionally, the bidirectional LLC resonant converter operates in the inductive range, with the switching frequency set to 70kHz~120kHz; The switching transistors of the primary-side full-bridge circuit are configured to operate in zero-voltage turn-on mode, and the switching transistors of the secondary-side full-bridge circuit are configured to operate in zero-current turn-off mode.

[0009] Optionally, the downstream single-phase inverter unit is a two-level single-phase full-bridge inverter, with the DC side connected to the 400V DC bus and the AC side connected to the power grid or load via an LC filter circuit. The downstream single-phase inverter unit is configured to use PQ decoupling control in grid-connected mode and droop control in off-grid mode.

[0010] Optionally, the single-phase photovoltaic energy storage converter further includes a battery sampling circuit, a grid sampling circuit, a drive circuit, and a communication circuit. The battery sampling circuit, the grid sampling circuit, the drive circuit, and the communication circuit are all integrated on the same PCB motherboard and are all electrically connected to the integrated main control unit. The single-phase photovoltaic energy storage converter is configured not to have a discrete controller and an external communication bus.

[0011] Optionally, the integrated main control unit is a single multi-core MCU, which is configured to perform dual-mode switching, PCS power conversion control, BMS battery management, and EMS energy dispatch functions.

[0012] Optionally, the wide voltage adaptation control unit adopts a hybrid control strategy that combines frequency conversion control with fixed reference PI fine-tuning control; The wide voltage adaptation control unit is configured to perform frequency conversion regulation in the input voltage range of 180V~270V, perform small-amplitude frequency fine-tuning of the reference frequency center in the input voltage range of 120V~180V, and stabilize the DC bus voltage at 400V.

[0013] Optionally, all switching transistors in the front-end bidirectional power conversion unit and the rear-end single-phase inverter unit are configured as 650V silicon carbide MOSFETs, and the overall switching frequency is set to 100kHz.

[0014] Optionally, the downstream single-phase inverter unit is configured to include a pre-synchronization control module; The pre-synchronization control module is configured to perform grid-connected to off-grid switching control when the grid fails, and to perform off-grid to grid-connected switching control when the grid recovers and the voltage amplitude difference and phase difference access conditions are met, wherein the grid-connected to off-grid switching time is configured to be no more than 10ms.

[0015] According to a second aspect of this application, a control method for a single-phase photovoltaic energy storage converter is provided, the method being applied to an integrated main control unit of the aforementioned single-phase photovoltaic energy storage converter, comprising: The wide voltage adaptation control unit controls the front-end bidirectional power conversion unit to operate in full-condition soft-switching mode within a wide DC input voltage range. Acquire power grid status signals and determine whether the power grid is in a fault state; If the power grid is determined to be in a fault state, the pre-synchronization control module of the downstream single-phase inverter unit will perform the switching control from grid-connected mode to off-grid mode. If it is determined that the power grid has returned to normal and the preset voltage amplitude difference and phase difference access conditions are met, then the switching control from off-grid mode to grid-connected mode is executed through the pre-synchronization control module. Based on the sampling signals from the battery sampling circuit and the power grid sampling circuit, PCS power conversion control, BMS battery management and EMS energy dispatch are performed.

[0016] By employing the above technical solutions, the single-phase photovoltaic energy storage converter and its control method provided in this application, through the overall architecture of a front-end bidirectional power conversion unit, a back-end single-phase inverter unit, an integrated main control unit, and a wide-voltage adaptation control unit, utilizes the wide-voltage adaptation control unit in conjunction with the front-end bidirectional power conversion unit to achieve full-condition soft-switching operation within a wide DC input voltage range. This effectively reduces switching losses, increases switching frequency and overall operating efficiency, reduces the size of magnetic components and increases power density, and improves device heating issues to enhance the long-term operational reliability of the system. Simultaneously, it is compatible with a wide range of DC voltage inputs from 120V to 270V, adapting to voltage fluctuation scenarios of different battery specifications and distributed photovoltaic modules, improving system configuration flexibility and reducing adaptation costs. The integrated main control unit enables integrated collaborative control of dual-mode switching, power conversion, battery management, and energy scheduling. By eliminating the need for separate controllers and external communication buses, it can eliminate communication delays between modules, improve protection response speed and collaborative control accuracy, avoid protection timing disorder under fault conditions, reduce hardware redundancy and the number of components, reduce overall costs, and avoid safety risks such as battery overcharging and over-discharging and power surges, thus meeting the high reliability, high safety, and fast response requirements of residential scenarios.

[0017] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This paper illustrates a system architecture block diagram of a single-phase photovoltaic energy storage converter provided in an embodiment of this application. Figure 2 This paper shows a main circuit topology diagram of a single-phase photovoltaic energy storage converter provided in an embodiment of this application; Figure 3 This application provides an embodiment of a front-end bidirectional LLC resonant gain characteristic curve. Figure 4 This illustration shows a PQ control block diagram provided in an embodiment of this application; Figure 5 This paper shows a control principle circuit diagram in an off-grid mode according to an embodiment of this application; Figure 6 This application provides a control flowchart for switching from grid-connected to off-grid operation according to an embodiment of the present application. Figure 7 This application provides a control flowchart for switching from off-grid to grid-connected operation according to an embodiment of the present application. Figure 8 This illustration shows a dual-mode switching principle diagram provided in an embodiment of this application; Figure 9 A flowchart illustrating a single-phase photovoltaic energy storage converter control method provided in an embodiment of this application is shown. In the picture: 1-Pre-stage bidirectional power conversion unit, 2-Post-stage single-phase inverter unit, 3-Integrated main control unit, 4-Wide voltage adaptation control unit. Detailed Implementation

[0019] The present application will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present application can be combined with each other.

[0020] Existing photovoltaic-storage systems generally adopt an architecture where the energy storage converter, battery management system, and energy management system are built separately. Each of these three units is equipped with an independent controller, sampling circuit, communication module, and protection unit, resulting in high hardware redundancy, a large number of components, and high overall cost. The modules communicate with each other via CAN or RS485 bus, which results in communication delays of hundreds of milliseconds. This leads to slow system protection response, low precision of coordinated control, and easy disruption of protection timing under fault conditions, causing safety risks such as battery overcharging, over-discharging, and power surges. This fails to meet the requirements of high reliability, high safety, and fast response in residential applications.

[0021] To address the aforementioned problems, embodiments of the present invention provide a single-phase photovoltaic energy storage converter, such as... Figure 1 As shown, the single-phase photovoltaic energy storage converter includes: a front-end bidirectional power conversion unit 1, a rear-end single-phase inverter unit 2, an integrated main control unit 3, and a wide-voltage adaptation control unit 4. The input terminal of the front-end bidirectional power conversion unit 1 is used to connect to a DC power supply, and the output terminal is connected to the DC bus terminal of the rear-end single-phase inverter unit 2. The output terminal of the rear-end single-phase inverter unit 2 is used to connect to the power grid or a load. The integrated main control unit 3 is electrically connected to the front-end bidirectional power conversion unit 1, the rear-end single-phase inverter unit 2, and the wide-voltage adaptation control unit 4. The integrated main control unit 3 is configured to perform integrated coordinated control of dual-mode switching, power conversion, battery management, and energy dispatch. The wide-voltage adaptation control unit 4 is connected to the front-end bidirectional power conversion unit 1, and the front-end bidirectional power conversion unit 1 is configured to operate in a soft-switching manner under all operating conditions within a wide DC input voltage range.

[0022] The input of the front-stage bidirectional power conversion unit 1 is connected to a DC power supply, and the output is connected to the DC bus of the rear-stage single-phase inverter unit 2. This allows for the isolation and boosting of a wide range of DC input voltages, and enables soft-switching operation under all voltage conditions, reducing switching losses and improving efficiency and power density. The output of the rear-stage single-phase inverter unit 2 is connected to the power grid or load, and can be used to invert a stable DC bus voltage into single-phase AC power, supporting both grid-connected and off-grid dual-mode operation. The integrated main control unit 3 connects to the front-stage bidirectional power conversion unit 1, the rear-stage single-phase inverter unit 2, and the wide-voltage adapter unit. Control unit 4 is electrically connected and serves as the core control unit of the entire machine. It can realize integrated and coordinated control of dual-mode switching, power conversion control, battery management, and energy dispatch, eliminating the need for separate controllers and external communication buses, eliminating communication delays, and improving system response speed and reliability. Wide voltage adaptation control unit 4 is connected to the front-end bidirectional power conversion unit 1 and can be used to cooperate with the front-end bidirectional power conversion unit 1 to achieve wide DC input voltage adaptation and adjustment, ensuring stable DC bus voltage under a wide input range of 120V~270V, compatible with different specifications of batteries and photovoltaic modules, improving system configuration flexibility and reducing adaptation costs.

[0023] In specific application scenarios, such as Figure 2 As shown, the front-end bidirectional power conversion unit 1 is a full-bridge symmetrical bidirectional LLC resonant converter, including a primary-side full-bridge circuit, a secondary-side full-bridge circuit, a resonant cavity, and a high-frequency transformer. The primary winding of the high-frequency transformer is connected to the primary-side full-bridge circuit, and the secondary winding is connected to the secondary-side full-bridge circuit. The input terminal of the primary-side full-bridge circuit forms the DC input side, which is compatible with 120V~270V DC voltage input. The output terminal of the secondary-side full-bridge circuit is connected to the 400V rated DC bus. The resonant cavity consists of a resonant inductor, a resonant capacitor, and a magnetizing inductor. The ratio of the magnetizing inductor to the resonant inductor is k=4, and the quality factor Q=0.3~0.8, so that the voltage gain range of the converter covers 1.48~3.33.

[0024] like Figure 2 As shown, the primary-side full-bridge circuit is the left-side H1 bridge arm, composed of switching transistors S1~S4 and their body diodes D1~D4. Its input terminal is connected to the bus capacitor C. H1 Connect to DC power supply U BAT / PV It is compatible with a wide range of DC voltage input from 120V to 270V; the secondary full-bridge circuit is the right-side H2 bridge arm, consisting of switching transistors Q1~Q4 and their body diodes M1~M4, with the output terminal connected to the bus capacitor C. H2 Connected to the 400V rated DC bus, providing a stable DC power supply for the subsequent DC / AC inverter; the resonant cavity consists of a resonant inductor L r1 Resonant capacitor C r And the magnetizing inductance L of the high-frequency transformer T mThe primary winding of the high-frequency transformer T is connected to the output of the primary full-bridge circuit, while the secondary winding is connected to the secondary full-bridge circuit, achieving electrical isolation and voltage matching.

[0025] Figure 3 The gain characteristic curves of the front-end bidirectional LLC resonant converter are shown. The left figure shows the gain curves for different ratios of excitation inductance to resonant inductance k (k=3~7) when the quality factor Q is fixed at 0.4. The right figure shows the gain curves for different quality factors Q (Q=0.2~0.6) when k is fixed at 5. It can be seen from the curves that the smaller the k value, the higher the peak gain of the converter and the steeper the gain curve; the smaller the Q value, the higher the peak gain of the converter and the sharper the resonant peak. This invention preferentially selects the parameter combination of k=4 and Q=0.3~0.8, which enables the converter to obtain a voltage gain of 1.48~3.33 in the switching frequency range of 70kHz~120kHz. This allows for a stable output of 400V rated DC bus voltage under a wide DC input range of 120V~270V, while ensuring that the switching frequency always operates in the inductive range, providing conditions for full-condition soft switching.

[0026] This bidirectional LLC resonant converter, through the aforementioned symmetrical full-bridge structure and resonant parameter configuration (excitation inductance to resonant inductance ratio k=4, quality factor Q=0.3~0.8, voltage gain covering 1.48~3.33), utilizes the resonant characteristics of the resonant cavity within the inductive operating range of 70kHz~120kHz to achieve zero-voltage turn-on (ZVS) for primary-side switches S1~S4 and zero-current turn-off (ZCS) for secondary-side switches Q1~Q4, thus eliminating hard switching losses and reverse recovery losses in principle. Simultaneously, through a hybrid control strategy combining frequency conversion and PI fine-tuning, it can stably output a 400V DC bus voltage within a wide input voltage range of 120V~270V. This solves the problems of soft-switching failure and efficiency degradation in traditional topologies under wide voltage conditions, improving system efficiency, power density, and operational reliability.

[0027] In specific application scenarios, the bidirectional LLC resonant converter operates in the inductive range with a switching frequency set to 70kHz~120kHz. The resonant current lags behind the bridge arm output square wave voltage, providing phase conditions for the zero-voltage turn-on of the primary-side switch. At the same time, by utilizing the clamping characteristics of the magnetizing inductor, the switching cycle is divided into a power transfer resonant stage and a free resonant stage, respectively achieving zero-current turn-off of the secondary-side switch and zero-voltage turn-on of the primary-side switch.

[0028] In boost mode, the primary-side full-bridge circuit (H1) alternately conducts S1, S4 and S2, S3 to convert the DC input voltage U... BAT / PV Converted to high-frequency square wave voltage v H1 This voltage excites the resonant cavity to generate a resonant current I.L The resonant current flows through the magnetizing inductor L before the switching transistor is turned off. m The energy stored in the resonant cavity completes the charging and discharging of the parasitic capacitance of the switching transistors during the dead time, causing the voltage across the switching transistors to drop to zero, thereby achieving zero-voltage turn-on (ZVS) for the primary-side switching transistors S1~S4 and eliminating turn-on losses. At the same time, under the clamping effect of the resonant cavity and the high-frequency transformer T, the resonant current naturally drops to zero before the secondary-side switching transistors Q1~Q4 are turned off, which can avoid the current surge when the switching transistors are turned off and achieve zero-current turn-off (ZCS) for the secondary-side switching transistors. In principle, this eliminates reverse recovery losses and turn-off spikes. Combined with 650V silicon carbide MOSFET devices, it significantly increases the switching frequency and reduces losses, solving the problems of low efficiency and severe heat generation of traditional hard-switching topologies under wide voltage and high-frequency operating conditions.

[0029] Specifically, during forward operation, the switching frequency operates in the range of 70kHz to 120kHz. A complete switching cycle is divided into 6 core modes, fully realizing primary-side ZVS and secondary-side ZCS. The circuit states and soft-switching logic of each mode are as follows: In the first mode, the system operates at the series resonant frequency, and the resonant current is always greater than the excitation current. The difference is the reduced load current on the secondary side of the transformer, which is the core stage of energy transfer.

[0030] In the second mode, the on-state current of secondary-side switches Q1 and Q4 has dropped to zero. At this point, Q1 and Q4 are turned off, achieving zero-current turn-off and completely eliminating turn-off losses. Simultaneously, the reverse recovery losses of the power devices are completely avoided. After the secondary-side current returns to zero, the magnetizing inductor... Loss of clamping, and resonant inductance Resonant capacitor They participate in the resonance, the resonant frequency switches to a lower excitation resonant frequency, and the resonant cavity enters the free resonance stage.

[0031] In the third mode, this design optimizes the parameters by k=4. The peak excitation current meets the minimum current requirement for junction capacitance charging and discharging across the full load and voltage range. Before the dead zone ends, the drain-source voltage of S2 and S3 can be completely discharged to 0V, and the body diodes of S2 and S3 will naturally conduct, clamping them at 0V. This completes all the preparatory work for the zero-voltage turn-on of S2 and S3.

[0032] In the fourth mode, the body diodes of S2 and S3 are already conducting. At this time, S2 and S3 are turned on, achieving zero-voltage turn-on of the primary-side switching transistors and completely eliminating turn-on losses. The primary-side input is applied in reverse across the resonant cavity, and the resonant current begins to rise negatively from the magnetizing current, increasing the magnetizing inductance. Once again clamped by the secondary-side reflected voltage, only the resonant inductor... With resonant capacitor When participating in series resonance, secondary side Q2 and Q3 enter synchronous rectification and conduction state, and energy is continuously supplied to the bus.

[0033] In the fifth mode, Q2 and Q3 are turned off, achieving zero-current turn-off again with no turn-off losses or reverse recovery losses; subsequently, the magnetizing inductor... Losing clamping again, with the resonant inductor Resonant capacitor They both enter the free resonance stage of the excitation resonant frequency.

[0034] In the sixth mode, S2 and S3 are turned off, entering the dead zone of the second half-cycle; the negative excitation current charges the junction capacitance of S2 and S3 and discharges the junction capacitance of S1 and S4. Before the dead zone ends, the voltage of S1 and S4 is discharged to 0V, and their body diodes are turned on, completing the preparatory work for the ZVS turn-on of S1 and S4 at the next moment.

[0035] In specific application scenarios, such as Figure 2 As shown, the downstream single-phase inverter unit 2 is a two-level single-phase full-bridge inverter. The DC side is connected to the 400V DC bus, and the AC side is connected to the grid or load through an LC filter circuit. The downstream single-phase inverter unit 2 is configured to use PQ decoupling control in grid-connected mode and droop control in off-grid mode.

[0036] like Figure 2 As shown, the second-stage single-phase inverter unit 2 is the DC / AC inverter section on the right side of the diagram. It consists of two-level single-phase full-bridge circuits formed by switching transistors S5~S8 and their body diodes M5~M8. The DC side is connected to the 400V DC bus output from the preceding bidirectional LLC resonant converter, and the AC side is connected via inductor L and capacitor C. f The LC filter circuit is connected to the power grid or load U. g .

[0037] In specific application scenarios, such as Figure 4 As shown, in grid-connected mode, the downstream single-phase inverter unit 2 achieves PQ decoupling control through a dual-loop control system based on a power outer loop and a current inner loop using a dq rotating coordinate system: the integrated main control unit first locks the grid phase through a phase-locked loop (PLL), and then converts the inverter output voltage and current to the dq coordinate system via Park transformation; in the power control stage, the active power reference value P... ref Compared with the measured active power P and reactive power reference values ​​Q ref The deviations from the measured reactive power Q are fed into the corresponding PI regulators to generate the d-axis reference current i. dref and q-axis reference current i qref In the current control stage, the reference current is compared with the actual current i. d i qThe difference, after passing through a current loop PI regulator and being compensated by a decoupling term ωL, is compared with the grid voltage U in the voltage synthesis stage. d U q By subtracting, the dq axis voltage command U is obtained. dref U qref Ultimately, through inverse Park transform and SPWM modulation, it drives... Figure 2 The full-bridge circuit composed of switching transistors S5 to S8 enables independent tracking and precise control of grid-connected active and reactive power.

[0038] In off-network mode, such as Figure 5 As shown, this unit switches to a drooping outer loop + voltage and current dual inner loop control: the main control unit samples the inductor current I. L With capacitor voltage U C The data is fed into the power calculation module to obtain real-time active power P and reactive power Q; in the droop control stage, P is compared with the reference active power P. ref Q and reference reactive power Q ref The deviation is measured by the droop coefficient k p k q Adjustment, combined with the rated frequency ω N Rated voltage U N The reference frequency and reference voltage are obtained. The voltage inner loop sends the deviation between the reference voltage and the measured voltage to the PI regulator to generate d-axis and q-axis reference currents. The current inner loop then sends the deviation between the reference current and the sampled current to the PI control. After inverse Park transformation, the drive signal is generated through SPWM to control the on and off of S5~S8, so that the inverter can autonomously and stably output voltage and frequency under the condition of no grid support, and realize reliable power supply for off-grid loads.

[0039] In specific application scenarios, the single-phase photovoltaic energy storage converter also includes a battery sampling circuit, a grid sampling circuit, a drive circuit, and a communication circuit. These circuits are all integrated on the same PCB motherboard and electrically connected to the integrated main control unit 3. The single-phase photovoltaic energy storage converter is configured without a discrete controller or external communication bus. The redundant architecture of discrete controllers and external communication buses is eliminated in the single-phase photovoltaic energy storage converter. Specifically, the battery sampling circuit is used to collect the voltage, current, and temperature signals of the energy storage battery in real time to realize the BMS battery management function; the grid sampling circuit is used to collect grid voltage, current, and frequency signals to provide a basis for grid-connected control, phase-locked synchronization, and fault protection; the drive circuit receives the PWM control signal from the integrated main control unit 3, amplifies it, and drives the switching transistors of the front-end bidirectional power conversion unit 1 and the rear-end single-phase inverter unit 2 to realize power conversion control; the communication circuit is used to realize signal interaction with the EMS energy management system, transmitting operating status and scheduling commands. Each circuit interacts with the integrated main control unit 3 via direct connection within the board, which can eliminate external communication delays between multiple controllers in traditional systems, improve protection response speed and collaborative control accuracy, reduce hardware redundancy and system cost, and realize integrated collaborative control of PCS power conversion, BMS battery management and EMS energy dispatch.

[0040] In specific application scenarios, the integrated main control unit is a single multi-core MCU. As the sole control core of the entire machine, the single multi-core MCU processes all control tasks of the single-phase photovoltaic energy storage converter in parallel through different cores: one core executes PCS power conversion control, realizing wide-voltage soft-switching control of the front-end bidirectional power conversion unit 1 and grid-connected / off-grid power closed-loop control of the back-end single-phase inverter unit 2; the second core executes BMS battery management function, completing battery charging and discharging protection, SOC estimation and equalization control through voltage, current and temperature signals collected by the battery sampling circuit; the third core executes EMS energy dispatch function, receiving external dispatch commands through the communication circuit and dynamically optimizing charging and discharging strategies based on grid status and battery state of charge; at the same time, the multi-core MCU uniformly executes dual-mode switching control, judging the grid status through the grid sampling circuit to achieve seamless switching between grid-connected PQ control and off-grid droop control. This single-chip multi-core MCU architecture can replace the three separate controllers (PCS, BMS, and EMS) in traditional optical storage systems. Each functional module achieves high-speed data interaction within the same chip, completely eliminating external communication bus delays, significantly improving system protection response speed and collaborative control accuracy, reducing hardware redundancy and overall system cost, and realizing full-link integrated control, sampling, driving, and communication.

[0041] In specific application scenarios, the wide voltage adaptation control unit 4 adopts a hybrid control strategy combining frequency conversion control and fixed-reference PI fine-tuning control. It is electrically connected to the preceding bidirectional power conversion unit 1 to collaboratively achieve stable output and efficient operation of the 400V DC bus within an ultra-wide input voltage range of 120V~270V. The wide voltage adaptation control unit 4 is configured to perform frequency conversion regulation within the input voltage range of 180V~270V. Utilizing the inherent characteristic of the LLC resonant converter's voltage gain varying with the switching frequency, it dynamically adjusts the switching frequency within the inductive operating range of 70kHz~120kHz. When the input voltage is 270V, the required gain is approximately 1.48. By adjusting the switching frequency to near the resonant frequency, the converter operates near the resonant point. To reduce circulating current losses and achieve maximum efficiency, when the input voltage drops to 180V, the required gain is approximately 2.22. The switching frequency is automatically reduced through a PI closed-loop control system, utilizing the characteristic that the gain increases as the frequency decreases to precisely match the gain requirement and stabilize the 400V bus. In the input voltage range of 120V to 180V, the wide voltage adaptation control unit 4 switches to small-amplitude PI fine-tuning control with 80kHz as the reference frequency. The bus voltage error is fed into the PI regulator, so that the switching frequency is only finely adjusted within the range of 70kHz to 90kHz. This not only utilizes the high gain and gentle slope of the gain curve in this range to meet the low-voltage high-gain requirement, but also avoids efficiency degradation caused by large frequency fluctuations, ultimately achieving efficient and stable operation across the entire voltage range.

[0042] In specific application scenarios, all switches in the front-end bidirectional power conversion unit 1 and the rear-end single-phase inverter unit 2 are configured as 650V silicon carbide MOSFETs, and the overall switching frequency is set to 100kHz. Compared with traditional silicon-based devices, silicon carbide MOSFETs have lower on-resistance, better reverse recovery characteristics, and higher switching speed. Combined with the full-condition soft-switching control of the bidirectional LLC resonant converter, switching losses and conduction losses can be significantly reduced, enabling the converter to operate stably at a high frequency of 100kHz. The high-frequency operating state not only reduces the size of the front-end resonant cavity magnetic components and the rear-end LC filter circuit, increasing the overall power density, but also avoids the heat generation and electromagnetic interference problems caused by high-frequency hard switching due to the soft-switching characteristics of the LLC topology. This allows the overall efficiency to break through the limitations of traditional silicon-based solutions, achieving higher energy conversion efficiency and long-term operational reliability.

[0043] In specific application scenarios, the downstream single-phase inverter unit 2 is configured with a pre-synchronization control module. This module is electrically connected to the integrated main control unit 3, serving as the core execution unit for seamless switching between grid-connected and off-grid modes. It works in conjunction with the grid sampling circuit 6 and the drive circuit 7 to achieve rapid, shock-free switching. For example... Figure 6As shown, when the system is in grid-connected operation, the pre-synchronization control module can monitor the grid status in real time. Once a grid fault is detected, the grid-connected to off-grid process is immediately initiated: First, the reference values ​​of active and reactive power exchange are set to 0 by control, so that the power exchange on the grid side is reduced to the set threshold range. Then, the static switch K is disconnected, the load voltage amplitude and phase are detected, and within a time of no more than 10ms, the inverter is switched from the grid-connected PQ control mode to the off-grid droop / constant voltage and constant frequency control mode. The voltage setpoint is adjusted to the load rated voltage, and a stable AC output is quickly established to ensure that the load power supply is uninterrupted.

[0044] like Figure 7 As shown, when the power grid resumes normal operation, the pre-synchronization control module initiates the off-grid to grid-connected process: It collects the amplitude, frequency, and phase information of the grid voltage and the inverter output voltage in real time through a dual phase-locked loop, continuously adjusting the inverter output voltage to keep the voltage amplitude difference within 2.2V and the phase difference within 1°, thus meeting the grid connection access conditions; during this process, such as Figure 8 As shown, a smooth transition of control modes can be achieved through a control switch: when the system is in an off-grid state, switch S will set the voltage reference value U... dref U qref With current reference value i dref i qref The control loop is connected to execute droop / constant voltage and constant frequency control; when the power grid returns to normal, and the amplitude difference and phase difference between the inverter output voltage and the grid voltage meet the grid connection access conditions, switch S switches to grid connection control mode, and the current reference value i is set to... dref i qref The control loop is connected to generate dq-axis voltage commands through the current loop PI regulator, decoupling term ωL compensation, and voltage synthesis stage. These commands are then driven by SPWM modulation to drive the switching transistors S1~S4. At this time, the static switch K is closed, and the current setpoint is adjusted to the grid-connected desired value. This ensures that the inverter output current is in phase and frequency with the grid voltage, allowing for a smooth transition into grid-connected operation. This approach avoids the impact of inrush current on equipment and the grid from the control loop level, achieving seamless switching from off-grid to grid-connected operation.

[0045] In summary, the single-phase photovoltaic energy storage converter provided in this application, through its overall architecture consisting of a front-end bidirectional power conversion unit, a back-end single-phase inverter unit, an integrated main control unit, and a wide-voltage adaptation control unit, utilizes the wide-voltage adaptation control unit in conjunction with the front-end bidirectional power conversion unit to achieve soft-switching operation under all operating conditions within a wide DC input voltage range. This effectively reduces switching losses, increases switching frequency and overall system efficiency, reduces the size of magnetic components and increases power density, and improves device heat dissipation to enhance the long-term reliability of the system. Simultaneously, it is compatible with a wide range of DC voltage inputs from 120V to 270V, adapting to voltage fluctuation scenarios of different battery specifications and distributed photovoltaic modules, improving system configuration flexibility and reducing adaptation costs. The integrated main control unit enables integrated collaborative control of dual-mode switching, power conversion, battery management, and energy scheduling. By eliminating the need for separate controllers and external communication buses, it can eliminate communication delays between modules, improve protection response speed and collaborative control accuracy, avoid protection timing disorder under fault conditions, reduce hardware redundancy and the number of components, reduce overall costs, and avoid safety risks such as battery overcharging and over-discharging and power surges, thus meeting the high reliability, high safety, and fast response requirements of residential scenarios.

[0046] Furthermore, to fully illustrate the implementation of this embodiment, this embodiment also provides a control method for a single-phase photovoltaic energy storage converter, which can be applied to the integrated main control unit of the aforementioned single-phase photovoltaic energy storage converter. For example... Figure 9 As shown, the method includes: Step 910: Control the front-end bidirectional power conversion unit to operate in full-condition soft-switching mode within a wide DC input voltage range through the wide voltage adaptation control unit.

[0047] Among them, the wide DC input voltage range refers to the range of DC input voltages in which the converter can operate stably. This solution can cover an ultra-wide range from low voltage to high voltage to adapt to the DC power input requirements of different scenarios. The full-condition soft-switching mode means that the converter can achieve zero voltage turn-on (ZVS) or zero current turn-off (ZCS) under the entire input voltage range and full load conditions, which greatly reduces the switching losses.

[0048] In specific application scenarios, the wide voltage adaptation control unit can dynamically adjust the operating parameters of the front-end bidirectional power conversion unit according to changes in the input DC voltage, enabling the converter to operate stably in full-condition soft-switching mode across a wide DC input voltage range. By combining wide voltage adaptation control with full-condition soft-switching operation, the DC input voltage adaptation range of the converter can be significantly expanded, switching losses reduced, and energy conversion efficiency and operational stability improved.

[0049] Step 920: Obtain the power grid status signal and determine whether the power grid is in a fault state.

[0050] Among them, the power grid status signal refers to various electrical parameters that reflect the operating status of the power grid, mainly including power grid voltage amplitude, frequency, phase and current waveform signals, which are the basis for judging whether the power grid is normal; the fault status refers to the operating status when the power grid voltage, frequency, phase and other parameters exceed the normal operating range, or when there are abnormal situations such as power outage, drop, distortion, etc., and the power grid cannot provide stable power support for the load.

[0051] In this embodiment of the present disclosure, the grid sampling unit can collect grid voltage, frequency, phase and other status signals in real time, and then the main control unit can process and analyze the collected signals and compare them with preset normal operation parameter thresholds to determine whether the grid is in a fault state.

[0052] By acquiring and analyzing grid status signals in real time, grid fault conditions can be quickly and accurately identified, providing a reliable basis for subsequent control strategies such as grid connection / off-grid mode switching and protection actions. This effectively improves the system's response speed and operational reliability to grid anomalies, ensuring the continuity and stability of power supply to the load.

[0053] Step 930: If the power grid is determined to be in a fault state, the switching control from grid-connected mode to off-grid mode is executed through the pre-synchronization control module of the downstream single-phase inverter unit.

[0054] Among them, grid-connected mode refers to the working mode in which the inverter operates in parallel with the public power grid, using the grid voltage as a reference and adopting a constant power control strategy to deliver or absorb power from the grid; off-grid mode refers to the working mode in which the inverter disconnects from the public power grid, independently establishes AC voltage and frequency, and provides stable power to local loads.

[0055] In specific application scenarios, when the power grid is determined to be in a fault state, the pre-synchronization control module of the downstream single-phase inverter unit can be used to perform the switching control from grid-connected mode to off-grid mode, so that the inverter can quickly disconnect from the power grid and switch to autonomous operation mode, providing stable AC power supply to the local load.

[0056] The pre-synchronization control module enables rapid switching from grid-connected to off-grid mode, which can promptly disconnect from the grid and establish independent power supply in the event of a grid fault. This avoids the impact of grid faults on local loads, ensures the continuity and stability of load power supply, reduces inrush current during the switching process, and improves the reliability and safety of system operation.

[0057] Step 940: If it is determined that the power grid has returned to normal and meets the preset voltage amplitude difference and phase difference access conditions, then the off-grid mode to grid-connected mode switching control is executed through the pre-synchronization control module.

[0058] Among them, the voltage amplitude difference access condition refers to the preset threshold that the difference between the inverter output voltage amplitude and the grid voltage amplitude must meet, which is one of the key parameters for achieving safe grid connection; the phase difference access condition refers to the preset threshold that the difference between the inverter output voltage phase and the grid voltage phase must meet, which is one of the key parameters for achieving shock-free grid connection.

[0059] In specific application scenarios, when it is determined that the power grid has returned to normal operation, and the amplitude difference and phase difference between the inverter output voltage and the grid voltage meet the preset access conditions, the pre-synchronization control module of the downstream single-phase inverter unit can be used to perform the switching control from off-grid mode to grid-connected mode, so that the inverter can be smoothly connected to the grid and achieve parallel operation with the grid.

[0060] By using the pre-synchronization control module to perform off-grid to grid-connected switching control under the conditions of voltage amplitude difference and phase difference access, the generation of inrush current during grid connection can be effectively avoided, achieving smooth and shock-free grid connection between the inverter and the grid, ensuring the safe and stable operation of the equipment and the grid, and improving the reliability of system mode switching and power quality.

[0061] Step 950: Based on the sampling signals from the battery sampling circuit and the power grid sampling circuit, execute PCS power conversion control, BMS battery management and EMS energy dispatch.

[0062] Among them, PCS power conversion control refers to the closed-loop regulation strategy for the bidirectional conversion process of electrical energy, so as to realize the bidirectional stable conversion and output regulation of AC and DC energy; BMS battery management is a comprehensive management mechanism for monitoring, controlling and protecting the overall operating status of energy storage batteries, so as to ensure the long-term healthy operation of batteries; EMS energy dispatch refers to the overall regulation and control method for energy allocation and operation strategy optimization based on the overall operating conditions of the system, so as to realize the rational allocation and utilization of electrical energy.

[0063] In this embodiment of the present disclosure, real-time detection signals output by the battery sampling circuit and the power grid sampling circuit can be collected in a unified manner. The two types of sampling data are integrated and summarized as the basis for overall regulation. Dynamic regulation of the power conversion process, comprehensive monitoring and management of energy storage batteries, and overall energy scheduling of the system are carried out simultaneously. Multi-dimensional functions are coordinated and centrally controlled based on a unified data foundation.

[0064] By relying on multi-channel sampling signals to achieve integrated operation of multiple control functions, data exchange and strategy coordination can be formed between power conversion, battery management and energy dispatch, improving the overall operation and control of the entire equipment, ensuring the stability and controllability of the power conversion process, constraining battery operating conditions, optimizing system energy distribution logic, and comprehensively enhancing the overall operational stability, safety and energy utilization efficiency of the equipment.

[0065] In summary, the single-phase photovoltaic energy storage converter control method provided in this application, through the wide voltage adaptation control of the front-end bidirectional power conversion unit, can achieve efficient soft-switching operation under all operating conditions with an ultra-wide DC input range of 120V~270V. Combined with the pre-synchronization control module of the downstream single-phase inverter unit, it can complete the rapid switching from grid-connected to off-grid within no more than 10ms. Furthermore, when the grid recovers, it achieves seamless switching from off-grid to grid-connected through voltage amplitude difference and phase difference access conditions. Simultaneously, based on the sampling signals from the battery sampling circuit and the grid sampling circuit, it executes PCS power conversion control, BMS battery management, and EMS energy dispatch in parallel on a single multi-core MCU. This eliminates external communication delays between multiple controllers in traditional systems, improves system protection response speed and collaborative control accuracy, reduces hardware redundancy and overall cost, and achieves an organic combination of wide voltage adaptation, seamless mode switching, and multi-task integrated control. It solves the technical problems of narrow voltage adaptation range, high switching losses, large impact during grid-connected / off-grid switching, and complex redundant control architecture in traditional residential photovoltaic energy storage systems, significantly improving system efficiency, reliability, and operational flexibility.

[0066] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing this application. Those skilled in the art will understand that the modules in the apparatus of the embodiment can be distributed within the apparatus of the embodiment as described, or can be modified to be located in one or more apparatuses different from this embodiment. The modules of the above-described embodiment can be combined into one module, or further divided into multiple sub-modules.

[0067] The serial numbers in this application are for descriptive purposes only and do not represent the superiority or inferiority of any particular implementation scenario. The above disclosures are merely a few specific implementation scenarios of this application; however, this application is not limited thereto, and any variations conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A single phase photovoltaic energy storage converter, characterized in that, include: The system includes a front-end bidirectional power conversion unit, a back-end single-phase inverter unit, an integrated main control unit, and a wide voltage adaptation control unit. The input terminal of the front-stage bidirectional power conversion unit is used to connect to a DC power supply, and the output terminal is connected to the DC bus terminal of the rear-stage single-phase inverter unit. The output terminal of the subsequent single-phase inverter unit is used to connect to the power grid or load; The integrated main control unit is electrically connected to the front-end bidirectional power conversion unit, the rear-end single-phase inverter unit, and the wide voltage adaptation control unit. The integrated main control unit is configured to perform integrated collaborative control of dual-mode switching, power conversion, battery management, and energy scheduling. The wide voltage adaptation control unit is connected to the front-end bidirectional power conversion unit, which is configured to operate soft-switching under all operating conditions within a wide DC input voltage range.

2. The single-phase PV energy storage inverter of claim 1, wherein, The front-end bidirectional power conversion unit is a full-bridge symmetrical bidirectional LLC resonant converter, which includes a primary-side full-bridge circuit, a secondary-side full-bridge circuit, a resonant cavity, and a high-frequency transformer. The primary winding of the high-frequency transformer is connected to the primary full-bridge circuit, and the secondary winding is connected to the secondary full-bridge circuit. The input terminal of the primary-side full-bridge circuit forms a DC input side, which is compatible with 120V~270V DC voltage input. The output terminal of the secondary full-bridge circuit is connected to the 400V rated DC bus. The resonant cavity is composed of a resonant inductor, a resonant capacitor, and a magnetizing inductor. The ratio of the magnetizing inductor to the resonant inductor is k=4, and the quality factor Q=0.3~0.8, so that the voltage gain range of the converter covers 1.48~3.

33.

3. The single-phase PV energy storage inverter of claim 2, wherein, The bidirectional LLC resonant converter operates in the inductive range, with a switching frequency set to 70kHz~120kHz. The switching transistors of the primary-side full-bridge circuit are configured to operate in zero-voltage turn-on mode, and the switching transistors of the secondary-side full-bridge circuit are configured to operate in zero-current turn-off mode.

4. The single-phase PV energy storage inverter of claim 1, wherein, The subsequent single-phase inverter unit is a two-level single-phase full-bridge inverter, with the DC side connected to the 400V DC bus and the AC side connected to the grid or load through an LC filter circuit. The downstream single-phase inverter unit is configured to use PQ decoupling control in grid-connected mode and droop control in off-grid mode.

5. The single-phase PV energy storage inverter of claim 1, wherein, The single-phase photovoltaic energy storage converter also includes a battery sampling circuit, a grid sampling circuit, a drive circuit, and a communication circuit. The battery sampling circuit, the grid sampling circuit, the drive circuit, and the communication circuit are all integrated on the same PCB motherboard and are all electrically connected to the integrated main control unit. The single-phase photovoltaic energy storage converter is configured not to have a discrete controller and an external communication bus.

6. The single-phase PV energy storage inverter of claim 5, wherein, The integrated main control unit is a single multi-core MCU, which is configured to perform dual-mode switching, PCS power conversion control, BMS battery management, and EMS energy dispatch functions.

7. The single-phase PV energy storage inverter of claim 1, wherein, The wide voltage adaptation control unit adopts a hybrid control strategy that combines frequency conversion control with fixed reference PI fine-tuning control. The wide voltage adaptation control unit is configured to perform frequency conversion regulation in the input voltage range of 180V~270V, perform small-amplitude frequency fine-tuning of the reference frequency center in the input voltage range of 120V~180V, and stabilize the DC bus voltage at 400V.

8. The single-phase photovoltaic energy storage converter according to claim 2 or 4, characterized in that, All switching transistors in the front-end bidirectional power conversion unit and the rear-end single-phase inverter unit are configured as 650V silicon carbide MOSFETs, and the overall switching frequency is set to 100kHz.

9. The single-phase photovoltaic energy storage converter according to claim 1, characterized in that, The subsequent single-phase inverter unit is configured to have a pre-synchronization control module; The pre-synchronization control module is configured to perform grid-connected to off-grid switching control when the grid fails, and to perform off-grid to grid-connected switching control when the grid recovers and the voltage amplitude difference and phase difference access conditions are met, wherein the grid-connected to off-grid switching time is configured to be no more than 10ms.

10. A single-phase photovoltaic energy storage inverter control method, characterized by, The method is applied to the integrated main control unit of the single-phase photovoltaic energy storage converter according to any one of claims 1-9, including: The wide voltage adaptation control unit controls the front-end bidirectional power conversion unit to operate in full-condition soft-switching mode within a wide DC input voltage range. Acquire power grid status signals and determine whether the power grid is in a fault state; If the power grid is determined to be in a fault state, the pre-synchronization control module of the downstream single-phase inverter unit will perform the switching control from grid-connected mode to off-grid mode. If it is determined that the power grid has returned to normal and the preset voltage amplitude difference and phase difference access conditions are met, then the switching control from off-grid mode to grid-connected mode is executed through the pre-synchronization control module. Based on the sampling signals from the battery sampling circuit and the power grid sampling circuit, PCS power conversion control, BMS battery management and EMS energy dispatch are performed.

Images