Direct-current bus voltage stabilization system and method of alternating-current and direct-current micro-grid

Abstract

The invention discloses a DC bus voltage stabilization system and method for an AC / DC micro-grid. The method comprises the following steps: transmitting photovoltaic electric energy to a DC bus through a Boost converter of a photovoltaic power generation unit; a super capacitor energy storage branch and a storage battery energy storage branch of the hybrid energy storage unit are connected in parallel to a direct current bus through independent bidirectional Buck-Boost converters; the direct current bus electric energy is converted into alternating current electric energy through a grid-connected inverter of the alternating current inversion grid-connected unit; after the direct-current bus voltage, the voltage of each unit, the current and the energy storage charge state information are obtained through a sampling link of the special control unit, an adjusting instruction is generated through operation, the direct-current bus voltage is stably controlled, and the stability of the direct-current bus voltage is kept. Through hardware design optimization, the DC bus voltage anti-disturbance capability is significantly improved, and the service life of energy storage equipment is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of microgrid technology, and particularly relates to a DC bus voltage stabilization system and method for AC / DC microgrids. Background Technology

[0002] Driven by the "dual carbon" goal, the scale of distributed photovoltaic grid connection has experienced explosive growth. As the core carrier for efficient photovoltaic consumption, the DC bus of the AC-DC hybrid microgrid serves as the power interaction hub between photovoltaic power generation units, hybrid energy storage systems, and AC inverter grid-connected units. Its voltage stability directly determines the photovoltaic power transmission efficiency, hybrid energy storage lifespan, and grid-connected power quality. However, in existing photovoltaic grid-connected systems, DC bus voltage stability faces multiple challenges: photovoltaic output is subject to random disturbances such as sudden irradiance and temperature drift, causing high-frequency fluctuations in bus voltage; in hybrid energy storage systems, the "instantaneous-long-term" power regulation requirements of supercapacitors (millisecond-level response, long cycle life but low capacity) and batteries (minute-level response, high capacity but limited cycle life) differ significantly, but due to the inability of the general-purpose circuit topology hardware architecture to match their characteristics, energy storage efficiency decreases; at the same time, when the output power of the inverter grid-connected unit changes, the load changes suddenly, or the grid fails, the instantaneous power change on the inverter side increases, directly transmitted to the DC bus, causing voltage surges / drops.

[0003] To address the aforementioned issues, existing technologies are caught in a contradiction between "hardware architecture synergy" and "hardware design." At the hardware architecture synergy level, many control schemes rely on a hardware combination of "high-frequency communication links + high-computing-power controllers." While theoretically this can achieve power component partitioning, structural adaptability is lacking, and complex coordination among multiple hardware modules is required, leading to delayed control response and difficulty in meeting the real-time requirements of bus voltage regulation. At the hardware design level, photovoltaic converters mostly use silicon-based power devices to construct the basic topology, resulting in insufficient adaptability of switching characteristics to sudden changes in photovoltaic power, making it difficult to quickly track power variations, and incurring high losses during power transmission. In hybrid energy storage branches, the battery branch lacks integrated current constraint hardware structures, making it prone to current surges during charge-discharge switching, thereby shortening battery cycle life.

[0004] The core pain point of existing technologies lies in the "lack of coordination between control and hardware"—complex algorithms struggle to match the hardware response limits, and general-purpose hardware cannot support the fine-grained control of algorithms. Therefore, there is an urgent need to construct a solution based on "differentiated hardware design as the foundation, and coordinated control strategies as an aid": by using photovoltaic SiC converters, energy storage branch characteristic adaptation circuits, and inverter-side filtering and pre-charging circuits, a topological foundation for "hardware-level characteristic matching" is established; combined with power and voltage control, the high cost and high latency of complex algorithms are avoided, achieving efficient voltage regulation through "hardware adaptation first, then control coordination."

[0005] Therefore, how to innovate from the perspective of system architecture and control strategy coordination to achieve efficient coordination of different characteristic units, thereby comprehensively improving the voltage stability and operational resilience of DC microgrids, has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the DC bus voltage stability problem caused by power fluctuations and load abrupt changes in existing DC microgrids, and to provide a DC microgrid voltage stabilization system and method based on multi-timescale coordinated control. By constructing a system architecture that combines hybrid energy storage coordination and power coordination, and adopting a hierarchical cooperative control strategy, precise voltage control across the entire timescale, from millisecond-level instantaneous response to minute-level energy dispatch, is achieved, thereby significantly improving the system's dynamic stability, operational reliability, and adaptability to high proportions of renewable energy.

[0007] To address the aforementioned technical problems, this invention provides a DC bus voltage stabilization system and method for AC / DC microgrids. Specifically, the DC bus voltage stabilization system for an AC / DC microgrid includes:

[0008] The system comprises a photovoltaic power generation unit, a hybrid energy storage unit, an AC inverter grid-connected unit, a DC bus, and a dedicated control unit, among which:

[0009] The photovoltaic power generation unit is used to transmit photovoltaic power to the DC bus through a Boost converter;

[0010] The hybrid energy storage unit includes a supercapacitor energy storage branch and a battery energy storage branch, and the two branches are connected in parallel to the DC bus through independent bidirectional Buck-Boost converters;

[0011] The AC inverter grid-connected unit is used to convert DC bus power into AC power through a grid-connected inverter.

[0012] The dedicated control unit is used to acquire DC bus voltage, voltage, current and energy storage state of charge information through the sampling link, generate adjustment commands through calculation, and transmit the adjustment commands to the Boost converter of the photovoltaic power generation unit, the bidirectional Buck-Boost converter of the hybrid energy storage unit and the AC inverter grid-connected unit through the drive link to stabilize the DC bus voltage and obtain control results.

[0013] Preferably, the Boost converter of the photovoltaic power generation unit adopts a two-way SiC MOSFET interleaved parallel topology, the phase difference between the two topologies is 180°, the switching frequency is ≥50kHz, and the output side is connected in series with a filter inductor.

[0014] The Boost converter receives the duty cycle adjustment command from the dedicated control unit via the PWM drive interface.

[0015] Preferably, the bidirectional Buck-Boost converter of the supercapacitor energy storage branch adopts a triple-staggered SiC topology;

[0016] The bidirectional Buck-Boost converter has a built-in voltage control module based on a DSP core.

[0017] The voltage control module is used to collect the supercapacitor terminal voltage, branch current and bus voltage through the voltage and current sampling link; it is also used to interact with the dedicated control unit through the high-speed digital interface, and the dedicated control unit sends instructions to the voltage control module.

[0018] Preferably, the bidirectional Buck-Boost converter of the battery energy storage branch adopts a three-interleaved topology design and has dual hardware and software protection functions;

[0019] The protection functions include: limiting the sudden amplitude of the bidirectional converter during operation and automatically disconnecting the circuit under branch overcurrent conditions.

[0020] Preferably, the AC side of the AC inverter grid-connected unit includes a coordinated hardware link of "pre-charging-filtering";

[0021] The collaborative hardware link includes a pre-charging circuit and a filtering circuit;

[0022] The pre-charge circuit is used to limit inrush current during the inverter startup phase;

[0023] The filter circuit is used to suppress harmonic components in power fluctuations.

[0024] Preferably, the dedicated control unit adopts a DSP+FPGA heterogeneous hardware architecture, including a DSP module and an FPGA module;

[0025] The DSP module is used for battery power control and supercapacitor DC bus voltage constant control, and outputs control commands to the FPGA module.

[0026] The FPGA module is used to generate PWM pulses based on control commands;

[0027] The PWM pulses are used to synchronously control each converter through the drive link.

[0028] Preferably, the interleaved parallel Boost converter of the photovoltaic power generation unit integrates current sampling elements and voltage sampling elements;

[0029] The sampling element is connected through the ADC sampling interface of the dedicated control unit to form a real-time acquisition hardware link for photovoltaic side current and voltage raw data;

[0030] The DSP module processes the acquired raw data and issues a duty cycle command, which is transmitted to the Boost converter through the PWM drive interface.

[0031] Preferably, the dedicated control unit is equipped with a power distribution function, which divides the power to be mitigated into instantaneous power components and continuous energy components through preset power component distribution logic;

[0032] The instantaneous power component is transmitted to the bidirectional Buck-Boost converter of the supercapacitor energy storage branch through the drive link;

[0033] The continuous energy component is transmitted to the bidirectional Buck-Boost converter of the battery energy storage branch through the drive link.

[0034] Preferably, the battery power control and the supercapacitor DC bus voltage constant control are implemented based on a DSP+FPGA heterogeneous hardware architecture;

[0035] The DSP module is responsible for power control and voltage control, and outputs a command reference.

[0036] The FPGA module receives instructions processed by the DSP module and generates drive signals, and controls the power adjustment of each converter based on the drive signals.

[0037] This invention also provides a method for stabilizing the DC bus voltage of an AC / DC microgrid, comprising:

[0038] Photovoltaic power is transmitted to the DC bus via the Boost converter of the photovoltaic power generation unit;

[0039] The supercapacitor energy storage branch and the battery energy storage branch of the hybrid energy storage unit are connected in parallel to the DC bus through independent bidirectional Buck-Boost converters.

[0040] The grid-connected inverter of the AC inverter grid-connected unit converts DC bus power into AC power.

[0041] After acquiring DC bus voltage, voltage, current and energy storage state of charge information through the sampling link of the dedicated control unit, the system generates adjustment commands through calculation and transmits the adjustment commands through the drive link to the Boost converter of the photovoltaic power generation unit, the bidirectional Buck-Boost converter of the hybrid energy storage unit and the AC inverter grid-connected unit respectively, so as to stabilize the DC bus voltage and maintain its stability.

[0042] Compared with the prior art, the present invention has the following advantages and technical effects:

[0043] This invention focuses on the synergy between hardware topology differentiation design and control strategy, breaking through the traditional approach of "relying on complex algorithms or single hardware". Through high-frequency adaptation of photovoltaic converters, characteristic matching of energy storage branches, and filtering and pre-charging circuits on the inverter side, it achieves efficient voltage regulation of the DC bus and is suitable for AC grid-connected microgrid scenarios with a high proportion of photovoltaic access.

[0044] This invention constructs a system architecture centered on a DC bus, integrating distributed generation, clearly defined hybrid energy storage, and grid-connected inverters. At the hardware level, this forms an organically coordinated "multi-port power router" structure, achieving complementary structural advantages between AC and DC microgrids. Based on this, a coordinated control algorithm effectively suppresses power disturbances and other operating conditions across multiple time scales, significantly improving the system's dynamic response performance and operational stability. Furthermore, the distributed control architecture reduces dependence on the central control unit, ensuring that local faults do not affect the overall system function, further enhancing the system's robustness and reliability. Ultimately, the photovoltaic power generation unit, hybrid energy storage unit, dedicated control unit, and AC inverter grid-connected unit form a DC bus voltage stabilization scheme combining hardware topology differentiation with a coordinated control algorithm. Attached Figure Description

[0045] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0046] Figure 1 This is a schematic diagram of the system hybrid energy storage allocation strategy according to an embodiment of the present invention;

[0047] Figure 2 This is a system overall structure topology diagram according to an embodiment of the present invention;

[0048] Figure 3 This is a schematic diagram of the bidirectional BUCK-BOOST control of a supercapacitor according to an embodiment of the present invention;

[0049] Figure 4 This is a schematic diagram of the bidirectional BUCK-BOOST control for batteries according to an embodiment of the present invention.

[0050] Figure 5 This is a schematic diagram of VSG control according to an embodiment of the present invention. Detailed Implementation

[0051] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0052] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0053] Example 1

[0054] like Figure 1 As shown, this embodiment provides a DC bus voltage stabilization system for an AC / DC microgrid, aiming to solve the problem of DC bus voltage instability caused by photovoltaic output fluctuations, mismatch in energy storage response characteristics, and inverter grid-connection disturbances in existing photovoltaic grid-connected systems. It includes:

[0055] The system comprises a photovoltaic power generation unit, a hybrid energy storage unit, an AC inverter grid-connected unit, a DC bus, and a dedicated control unit, among which:

[0056] The photovoltaic power generation unit is used to transmit photovoltaic power to the DC bus via a Boost converter;

[0057] The hybrid energy storage unit includes a supercapacitor energy storage branch and a battery energy storage branch. The two branches are connected in parallel to the DC bus through independent bidirectional Buck-Boost converters. The supercapacitor branch is adapted to suppress millisecond-level instantaneous power fluctuations, while the battery branch is adapted to continuous energy surplus and deficit regulation.

[0058] The AC inverter grid-connected unit is used to convert DC bus power into AC power through a grid-connected inverter.

[0059] The dedicated control unit is used to obtain the DC bus voltage, voltage, current and energy storage state of charge information through the sampling link, generate adjustment commands through calculation, and transmit the adjustment commands to the Boost converter of the photovoltaic power generation unit, the bidirectional Buck-Boost converter of the hybrid energy storage unit and the AC inverter grid-connected unit through the drive link to stabilize the DC bus voltage and obtain the control results.

[0060] Specifically, the DC bus voltage stabilization system in this embodiment includes a photovoltaic power generation unit, a hybrid energy storage unit, an AC inverter grid-connected unit, a DC bus, and a dedicated control unit. Each unit forms a closed-loop control link through electrical connections.

[0061] The photovoltaic power generation unit is connected to the DC bus through an interleaved parallel Boost converter based on silicon carbide devices to reduce switching losses and stabilize photovoltaic power transmission.

[0062] The hybrid energy storage unit consists of a supercapacitor energy storage branch and a battery energy storage branch. Both branches are connected in parallel to the DC bus through independent bidirectional Buck-Boost converters. The supercapacitor branch is adapted to millisecond-level instantaneous power fluctuation suppression, while the battery branch is adapted to continuous energy surplus and deficit regulation.

[0063] The AC inverter grid-connected unit adopts an ANPC three-level topology grid-connected inverter, whose circuit integrates a pre-charge circuit and a filter circuit:

[0064] In the pre-charge circuit, the switch, in conjunction with the parallel resistor, suppresses the inrush current during the power-on initialization phase, preventing damage to power devices and capacitors from instantaneous high current and ensuring safe power-on of the system.

[0065] The filter circuit consists of a filter inductor and a filter capacitor. The inductor and capacitor form an LC low-pass filter network, which attenuates the high-frequency harmonics of the inverter output to optimize the grid-connected current waveform, avoid oscillation amplification, and improve the stability of the filter system.

[0066] The dedicated control unit adopts a DSP+FPGA heterogeneous architecture to collect the bus voltage, voltage and current of each unit and energy storage state of charge in real time. Through hardware drive control, it adjusts the output of the photovoltaic converter, the charging and discharging power of the energy storage and the output power of the inverter to achieve DC bus voltage stability.

[0067] This embodiment significantly improves the DC bus voltage's anti-disturbance capability through hardware topology optimization, controlling voltage fluctuations within ±2% of the rated value, while extending the service life of energy storage equipment. It is suitable for AC grid-connected microgrid scenarios with a high proportion of photovoltaic access.

[0068] Furthermore, the Boost converter of the photovoltaic power generation unit adopts a two-way SiC MOSFET interleaved parallel topology with a phase difference of 180° between the two topologies, a switching frequency ≥50kHz, and a series filter inductor on the output side.

[0069] The Boost converter receives duty cycle adjustment commands from a dedicated control unit via a PWM drive interface.

[0070] Furthermore, the photovoltaic power generation unit in this embodiment adopts an interleaved parallel Boost converter topology. The converter consists of two phase-interleaved Boost power bridge arms. Each bridge arm integrates a high-frequency power switching device, and the converter body integrates a voltage sampling element and a current sampling element, which are connected to the DC bus in parallel through the power output terminal.

[0071] Specifically, the Boost converter adopts a two-SiC MOSFET interleaved parallel topology with a switching frequency ≥50kHz. It utilizes the low on-resistance and high-frequency switching characteristics of SiC devices to reduce power loss and improve dynamic response speed.

[0072] Furthermore, the bidirectional Buck-Boost converter of the supercapacitor energy storage branch adopts a synchronous bidirectional Buck-Boost half-bridge high-frequency topology.

[0073] The bidirectional Buck-Boost converter incorporates a high-bandwidth voltage control module based on a DSP core;

[0074] The voltage control module is used to collect the supercapacitor terminal voltage, branch current and bus voltage through the voltage and current sampling link; it is also used to interact with the dedicated control unit through the high-speed digital interface, and the dedicated control unit sends commands to the voltage control module.

[0075] Furthermore, the bidirectional Buck-Boost converter of the supercapacitor energy storage branch involved in this embodiment is adapted to the millisecond-level instantaneous voltage regulation requirement. It adopts a synchronous bidirectional Buck-Boost triple-interleaved topology and uses complementary high-frequency switching devices to form a power converter. It has a built-in voltage control module based on a DSP core and integrates a high-precision voltage and current sampling link to collect the supercapacitor terminal voltage. It interacts with a dedicated control unit through a high-speed digital interface and receives commands when the DC bus voltage fluctuates instantaneously, realizing fast response to power command tracking.

[0076] Furthermore, the bidirectional Buck-Boost converter of the battery energy storage branch adopts a three-interleaved topology design and has dual hardware and software protection functions.

[0077] The protection functions include: limiting the sudden amplitude of the bidirectional converter during operation and automatically disconnecting the circuit under conditions such as branch overcurrent.

[0078] Furthermore, the bidirectional Buck-Boost converter of the battery energy storage branch involved in this embodiment is adapted to long-term energy regulation requirements: the branch is connected in series with a current suppression element, which uses its impedance characteristics to limit the current surge amplitude during the charge and discharge switching process; a parallel fuse device is connected to automatically cut off the circuit to achieve protection when the branch is overcurrent for a long time, and can be manually reset after the fault is cleared, so as to ensure the long-term operational reliability of the battery and the converter.

[0079] Furthermore, the grid-connected side of the AC inverter grid-connected unit includes a coordinated hardware link of "pre-charging-filtering";

[0080] The collaborative hardware link includes a pre-charging circuit and a filtering circuit;

[0081] The pre-charge circuit is used to limit inrush current during the inverter startup phase;

[0082] Filtering circuits are used to suppress harmonic components in power fluctuations.

[0083] Furthermore, the "pre-charge-filter" collaborative hardware link constructed on the DC side of the AC inverter grid-connected unit involved in this embodiment limits the surge current during inverter startup and other stages through the pre-charge circuit; the synchronously integrated filter circuit suppresses harmonic components in power fluctuations. The two work together to ensure that the power change rate and voltage ripple strictly match the overall power quality requirements of DC bus voltage regulation.

[0084] Furthermore, the dedicated control unit adopts a DSP+FPGA heterogeneous hardware architecture, including a DSP module and an FPGA module;

[0085] The DSP module is used for battery power control and supercapacitor DC bus voltage constant control, and outputs control commands to the FPGA module.

[0086] The FPGA module is used to generate PWM pulses based on control commands;

[0087] PWM pulses are used to synchronously control each converter through the drive link.

[0088] Furthermore, the dedicated control unit involved in this embodiment adopts a DSP+FPGA heterogeneous architecture to collect DC bus voltage, current of each unit and state of charge (SOC) of energy storage in real time. Through control strategies, it directly adjusts the output of the Boost converter of the photovoltaic power generation unit, the charging and discharging power of the hybrid energy storage unit, and the DC side power absorption of the inverter unit to achieve stable control of DC bus voltage.

[0089] Furthermore, the dedicated control unit involved in this embodiment adopts a DSP+FPGA heterogeneous hardware architecture. The DSP module carries the core control logic such as battery power control and supercapacitor DC bus voltage constant control, and performs calculations related to the division of power components to be smoothed and DC bus voltage stability. The FPGA module generates PWM pulses based on the control commands output by the DSP, and synchronously regulates the output power adjustment of the bidirectional Buck-Boost converter of the photovoltaic power generation unit, the bidirectional Buck-Boost converter of the hybrid energy storage unit, and the AC inverter grid-connected unit, ensuring the timing consistency of the coordinated response of multiple units.

[0090] Furthermore, the interleaved parallel Boost converter of the photovoltaic power generation unit integrates current sampling elements and voltage sampling elements;

[0091] The sampling element is connected through the ADC sampling interface of a dedicated control unit to form a hardware link for real-time acquisition of raw photovoltaic current and voltage data;

[0092] The DSP module processes the acquired raw data and issues a duty cycle command, which is transmitted to the Boost converter through the PWM drive interface.

[0093] Furthermore, the dedicated control unit in this embodiment possesses the capability for hardware-based acquisition of photovoltaic power data and command generation. This capability is achieved through the hardware link of the "photovoltaic power generation unit - dedicated control unit" and the collaboration of the DSP module: the interleaved parallel Boost converter of the photovoltaic power generation unit integrates current sampling elements and voltage sampling elements. The sampling elements are sampled and connected through the ADC of the dedicated control unit, forming a real-time acquisition hardware link for the raw current and voltage data of the photovoltaic side; the DSP module of the dedicated control unit relies on its own hardware computing resources to process the acquired raw data and issue commands; the commands are transmitted to the Boost converter through the PWM drive interface between the dedicated control unit and the photovoltaic power generation unit to adjust the converter duty cycle; the above-mentioned "data acquisition - processing - command issuance" entire link relies on hardware transmission and DSP hardware computing to meet the real-time control requirements of DC bus voltage regulation.

[0094] Furthermore, the dedicated control unit is equipped with a power distribution function, which divides the power to be mitigated into instantaneous power components and continuous energy components through preset power component distribution logic;

[0095] The instantaneous power component is transmitted to the bidirectional Buck-Boost converter of the supercapacitor energy storage branch through the drive link;

[0096] The continuous energy component is transmitted to the bidirectional Buck-Boost converter of the battery energy storage branch through the drive link.

[0097] Furthermore, the dedicated control unit in this embodiment is equipped with a power distribution function, which is designed based on the hardware response characteristics of the hybrid energy storage unit: for the power to be smoothed, the dedicated control unit, through a preset power component distribution logic, combined with the hardware characteristics of the supercapacitor energy storage branch's "millisecond-level instantaneous response" and the battery energy storage branch's "continuous energy regulation", divides the power to be smoothed into an instantaneous power component adapted to the supercapacitor and a continuous energy component adapted to the battery, and then transmits them to the bidirectional Buck-Boost converters of the two branches through a hardware drive link, driving the corresponding energy storage branches to perform power compensation actions.

[0098] Furthermore, the battery power control and the supercapacitor DC bus voltage constant control are implemented based on a DSP+FPGA heterogeneous hardware architecture;

[0099] The DSP module is responsible for power control and voltage control, and outputs a command reference.

[0100] The FPGA module receives instructions processed by the DSP module and generates drive signals, which are then used to control the power regulation of each converter.

[0101] Furthermore, in this embodiment, the battery power control and the supercapacitor DC bus voltage constant control are implemented based on a DSP+FPGA heterogeneous hardware architecture of a dedicated control unit. The specific structure and operation logic are as follows:

[0102] The battery power control algorithm focuses on power point tracking accuracy, implemented through a power-to-current conversion mechanism: first, a reference current is generated by dividing the battery power reference value by the terminal voltage; then, the actual current is sampled and the difference is calculated. After processing by the DSP's built-in PI controller, the PWM module outputs a control signal, and NOT logic generates complementary switching signals. The power of the battery branch converter is controlled by an FPGA. This algorithm relies on a DSP+FPGA heterogeneous architecture, with the DSP handling mathematical operations and instruction output, and the FPGA ensuring the timing of the drive and the coordination of modules such as the photovoltaic boost converter, achieving millisecond-level tracking of power commands.

[0103] The supercapacitor DC bus voltage constant control algorithm is based on voltage regulation and relies on the PI control logic of the DSP module. It acquires the DC bus voltage in real time and calculates the difference with the rated reference value. The deviation signal is processed by the PI controller and input to the PWM module to generate a single-channel drive waveform and complementary switching signals derived from the NOT logic. Then, the FPGA controls the timing of the bidirectional converter in the supercapacitor branch, ultimately constraining the bus voltage stability within ±2% of the rated value. The DSP undertakes the core control calculation task, while the FPGA is responsible for hardware timing and drive signal generation, ensuring the accuracy and real-time performance of the closed-loop regulation.

[0104] As a preferred implementation method, this embodiment discloses a DC bus voltage stabilization system for photovoltaic hybrid energy storage AC inverter grid connection. The core of this system is to solve the problems of photovoltaic output fluctuations, hybrid energy storage characteristic mismatch, and DC bus voltage instability caused by inverter grid connection disturbances in existing photovoltaic grid-connected systems through "differentiated hardware topology design + coordinated control strategy". The overall system architecture is built around "power transmission - fluctuation suppression - grid connection adaptation - precise control". The hardware selection and functional design of each unit are based on the actual microgrid operation requirements, as detailed below:

[0105] The system comprises photovoltaic power generation units, hybrid energy storage units, AC inverter grid-connected units, a DC bus, and dedicated control units. Each unit interacts with the others via electrical links and coordinates their operation through the dedicated control units, forming a closed-loop voltage regulation system. The DC bus is the core hub for power exchange in the entire system, responsible for aggregating power from the photovoltaic power generation units, compensating for power from the hybrid energy storage units, and facilitating power interaction between the AC inverter grid-connected units. Its rated voltage is set at 600VDC.

[0106] The photovoltaic power generation unit is used to convert photovoltaic energy into DC power and transmit it stably to the DC bus. Its core hardware is an interleaved parallel Boost converter of MOSFETs. The converter uses MOSFETs to form an interleaved parallel topology. The maximum power of the photovoltaic simulation source adapted to the converter is 5kW. At the same time, the converter of the photovoltaic power generation unit is connected to the dedicated control unit through the PWM output interface and the ADC sampling interface to ensure that the dedicated control unit can adjust the photovoltaic output in real time.

[0107] The hybrid energy storage unit is used to smooth power fluctuations on the DC bus. It consists of a supercapacitor energy storage branch and a battery energy storage branch with complementary functions. Both branches are connected in parallel to the DC bus through independent bidirectional Buck-Boost converters, and the hardware design is fully adapted to their respective response characteristics: First, the supercapacitor energy storage branch focuses on suppressing millisecond-level instantaneous power fluctuations, using supercapacitors, and the matching bidirectional Buck-Boost converter is based on MOSFETs. Second, the battery energy storage branch focuses on balancing continuous energy surpluses and deficits on the order of seconds to minutes, using lithium batteries, and the matching bidirectional Buck-Boost converter is also based on MOSFETs. The branch can collect the battery voltage, state of charge (SOC), and charging and discharging current in real time and upload the data to a dedicated control unit to prevent the battery life from being shortened due to overcharging, over-discharging, or current surges.

[0108] The AC inverter grid-connected unit converts DC power on the DC bus into AC power and connects it to the external AC grid, while preventing power disturbances on the inverter side from affecting the bus voltage. Its core hardware includes an ANPC three-level DC-AC grid-connected converter: the ANPC three-level grid-connected converter adopts a pluggable board design, uses fiber optic transmission for PWM signals, and has built-in voltage and current sensors to ensure sampling accuracy and isolation safety. A pre-charge circuit is configured to suppress inrush current during transient phases such as inverter startup, preventing sudden changes in bus voltage due to instantaneous charging and discharging; an integrated LC topology filter circuit suppresses harmonic components in power fluctuations. The aforementioned pre-charge and filtering units work together to ensure that the power change rate and voltage ripple strictly match the overall requirements of DC bus voltage regulation.

[0109] The dedicated control unit is the core of the system's regulation, employing heterogeneous hardware based on DSP and FPGA. The DSP handles closed-loop control algorithm calculations and data processing, while the FPGA is responsible for high-frequency PWM pulse generation, signal acquisition, and timing control. The control unit's hardware resources include 36 PWM outputs, 32 ADC sampling points, 2 CAN interfaces, and 2 Ethernet interfaces. The control strategy employs voltage and power control: the power control algorithm focuses on power tracking accuracy, implemented through a power-to-current conversion mechanism. First, a reference current is generated by dividing the battery power reference value by the terminal voltage. Then, the actual current is sampled and the difference is calculated. After processing by the DSP's built-in PI controller, the PWM module outputs a regulation signal, and NOT logic generates complementary switching signals. The FPGA controls the power flow of the battery branch converter.

[0110] The DC bus voltage constant control algorithm is based on voltage regulation and relies on the PI control logic of the DSP module to operate: real-time acquisition of DC bus voltage and subtraction with rated reference value. After the deviation signal is processed by the PI controller, it is input into the PWM module to generate a single-channel drive waveform and a complementary switching signal derived from the NOT logic. Then, the supercapacitor branch bidirectional converter is controlled by the FPGA to finally constrain the bus voltage stability within ±1% of the rated value.

[0111] During system operation, each unit works together to achieve voltage stabilization: the photovoltaic power generation unit transmits photovoltaic power stably to the DC bus through a SiC interleaved parallel Boost converter, and a dedicated control unit collects the bus voltage in real time; if the bus is undervoltage due to a sudden drop in photovoltaic output or inverter impact, the supercapacitor energy storage branch performs a discharge action in milliseconds to replenish the power deficit to the bus. After the bus voltage deviation is reduced, the battery energy storage branch performs continuous discharge through a bidirectional converter based on the SOC status uploaded by the BMS to balance the long-term energy deficit; throughout the process, all links work together to ultimately achieve DC bus voltage stabilization.

[0112] As an additional implementation, the DC microgrid voltage stabilization system of this invention uses the DC bus as the power hub and integrates distributed generation, hybrid energy storage, grid-connected conversion, and control units, such as... Figure 1 As shown, by combining the complementary characteristics of hybrid energy storage, the high power density of supercapacitors, the high energy density of batteries, and the AC side support capability of grid-type inverters, the DC bus voltage can be accurately stabilized across multiple time scales, while improving the system's adaptability and reliability to complex operating conditions.

[0113] The system described in this embodiment consists of a DC bus, a photovoltaic power generation unit, a hybrid energy storage unit, an AC inverter grid-connected unit, and a dedicated control unit. Each unit operates collaboratively via electrical links and communication interfaces. For example... Figure 2As shown, the DC bus rated voltage is set to 600V to match the output characteristics of the photovoltaic and energy storage units. The photovoltaic power generation unit adopts an interleaved parallel Boost converter based on SiCMOSFET, adapted to a 5kW photovoltaic analog source, and runs the MPPT function to maximize photovoltaic output. The converter is connected to a dedicated control unit through a PWM drive interface and an ADC sampling interface. The hybrid energy storage unit includes a supercapacitor energy storage branch and a battery energy storage branch, both of which are connected in parallel to the DC bus through a bidirectional Buck-Boost converter. The supercapacitor branch is equipped with high-frequency response hardware components. Both branches communicate with the dedicated control unit through a CAN bus to upload SOC and operating status parameters in real time. The AC inverter grid-connected unit adopts an ANPC three-level topology and transmits PWM signals through optical fiber to reduce electromagnetic interference. The dedicated control unit adopts a heterogeneous architecture of DSP and FPGA. The DSP runs voltage and power control algorithms, while the FPGA is responsible for high-frequency PWM pulse generation and signal acquisition to achieve precise coordinated control of each unit.

[0114] When the operating condition is triggered, a scenario of a sudden drop in light intensity is simulated using a photovoltaic simulation source. The light intensity drops rapidly from the rated value by about 30%, and the output power of the photovoltaic power generation unit decreases in the same step with the change in light intensity, from about 1kW to about 0.7kW, resulting in an instantaneous power deficit of about 0.3kW. Since the AC inverter grid-connected unit needs to maintain stable grid-connected power to avoid disturbing the grid, the DC bus experiences a voltage drop due to the sudden decrease in input power. The ADC sampling module of the dedicated control unit captures the bus voltage change in a very short time, and the voltage deviation reaches the response trigger threshold.

[0115] In this process, the supercapacitor energy storage branch first initiates an instantaneous power compensation response. This response characteristic is reflected in the power change curve as an instantaneous negative peak in the supercapacitor power curve. This leverages the hardware topology advantages of the supercapacitor branch. For example... Figure 3 As shown, the SiC bidirectional Buck-Boost converter it employs has high-frequency switching characteristics. After detecting a voltage deviation, the FPGA of the dedicated control unit generates an adjustment command within 1ms, driving the supercapacitor converter to quickly enter the discharge mode, injecting instantaneous power into the DC bus to fill the power deficit caused by the sudden drop in photovoltaic power. With the instantaneous support of the supercapacitor, the voltage drop trend of the bus is quickly curbed, which is reflected in the power change curve as a rapid stabilization and recovery of the voltage curve.

[0116] As the instantaneous power replenishment process of the supercapacitor energy storage branch progresses, the DSP of the dedicated control unit begins executing power balance calculations and long-term regulation logic. It calculates the total power difference of the system in real time using sampled data to determine the need for continuous power compensation from the battery branch to maintain long-term energy balance. The DSP sends a status query command to the BMS system of the battery energy storage branch via the CAN bus. Based on this query, the DSP sends a discharge command to the local controller of the battery branch. Figure 4 As shown, after receiving the command, the bidirectional Buck-Boost converter in the battery branch gradually increases the discharge power under the control of the power loop. The discharge current increases at a smooth rate. This characteristic is reflected in the power change curve as a smooth negative change in the battery power curve, which effectively ensures the battery cycle life.

[0117] With the combined effect of the instantaneous power support from the supercapacitor and the long-term energy compensation from the battery, the system gradually restores power balance: such as Figure 5 As shown, the input power of the AC inverter grid-connected unit adapts to a new power balance state through voltage and power control during the energy storage replenishment process, ultimately achieving a dynamic balance between photovoltaic input power, energy storage compensation power, and inverter output power. At this time, the DC bus voltage returns to the rated value of 600V under control, and the voltage fluctuation amplitude is controlled within ±2%. The power curves of each unit in the power change curve all enter the stable operation stage, verifying the voltage stabilization effectiveness of the system under the condition of sudden drop in photovoltaic output.

[0118] This implementation achieves rapid stabilization of DC bus voltage under photovoltaic power drop scenarios through deep collaboration between hardware topology and control strategy. The millisecond-level response of the supercapacitor is achieved by relying on high-frequency hardware characteristics, the stable replenishment of the battery is achieved by relying on its discharge characteristics, and the heterogeneous architecture of the dedicated control unit ensures the rapid generation and execution of control commands. All response characteristics are highly consistent with the power change curve, which fully verifies the engineering feasibility and stability of the technical solution of this invention.

[0119] Example 2

[0120] Based on the same inventive concept, this embodiment also provides a method for stabilizing the DC bus voltage of an AC / DC microgrid, including:

[0121] Photovoltaic power is transmitted to the DC bus via the Boost converter of the photovoltaic power generation unit;

[0122] The supercapacitor energy storage branch and the battery energy storage branch of the hybrid energy storage unit are connected in parallel to the DC bus through independent bidirectional Buck-Boost converters.

[0123] The grid-connected inverter of the AC inverter grid-connected unit converts DC bus power into AC power.

[0124] After acquiring DC bus voltage, current of each unit, and energy storage state of charge information through the sampling link of the dedicated control unit, a power regulation command is generated through calculation. The power regulation command is then transmitted through the drive link to the Boost converter of the photovoltaic power generation unit, the bidirectional Buck-Boost converter of the hybrid energy storage unit, and the AC inverter grid-connected unit to stabilize the DC bus voltage and obtain the control result.

[0125] The DC bus voltage stabilization method for AC / DC microgrids provided in this embodiment has all the advantages of the DC bus voltage stabilization system for AC / DC microgrids provided in Embodiment 1.

[0126] Example 3

[0127] This embodiment also discloses a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method described in Embodiment 1.

[0128] Example 4

[0129] This embodiment also discloses a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the method described in Embodiment 1.

[0130] Example 5

[0131] This embodiment also discloses a computer program product, including a computer program that, when executed by a processor, implements the steps of the method described in Embodiment 1.

[0132] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A DC bus voltage stabilization system for an AC / DC microgrid, characterized in that, include: The system comprises a photovoltaic power generation unit, a hybrid energy storage unit, an AC inverter grid-connected unit, a DC bus, and a dedicated control unit, among which: The photovoltaic power generation unit is used to transmit photovoltaic power to the DC bus through a Boost converter; The hybrid energy storage unit includes a supercapacitor energy storage branch and a battery energy storage branch, and the two branches are connected in parallel to the DC bus through independent bidirectional Buck-Boost converters; The AC inverter grid-connected unit is used to convert DC bus power into AC power through a grid-connected inverter. The dedicated control unit is used to acquire DC bus voltage, voltage, current and energy storage state of charge information through the sampling link, generate adjustment commands through calculation, and transmit the adjustment commands to the Boost converter of the photovoltaic power generation unit, the bidirectional Buck-Boost converter of the hybrid energy storage unit and the AC inverter grid-connected unit through the drive link to stabilize the DC bus voltage and obtain control results.

2. The system according to claim 1, characterized in that, The Boost converter of the photovoltaic power generation unit adopts a two-way SiC MOSFET interleaved parallel topology with a phase difference of 180° between the two topologies, a switching frequency ≥50kHz, and a series filter inductor on the output side. The Boost converter receives the duty cycle adjustment command from the dedicated control unit via the PWM drive interface.

3. The system according to claim 1, characterized in that, The bidirectional Buck-Boost converter of the supercapacitor energy storage branch adopts a triple-interlaced SiC topology; The bidirectional Buck-Boost converter has a built-in voltage control module based on a DSP core. The voltage control module is used to collect the supercapacitor terminal voltage, branch current and bus voltage through the voltage and current sampling link; it is also used to interact with the dedicated control unit through the high-speed digital interface, and the dedicated control unit sends power compensation commands to the voltage control module.

4. The system according to claim 1, characterized in that, The bidirectional Buck-Boost converter of the battery energy storage branch adopts a three-interleaved topology design and has dual hardware and software protection functions. The protection functions include: limiting the sudden amplitude of the bidirectional converter during operation and automatically disconnecting the circuit under branch overcurrent conditions.

5. The system according to claim 1, characterized in that, The AC side of the AC inverter grid-connected unit includes a "pre-charge-filter" collaborative hardware link; The collaborative hardware link includes a pre-charging circuit and a filtering circuit; The pre-charge circuit is used to limit inrush current during the inverter startup phase; The filter circuit is used to suppress harmonic components in power fluctuations.

6. The system according to claim 1, characterized in that, The dedicated control unit adopts a DSP+FPGA heterogeneous hardware architecture, including a DSP module and an FPGA module; The DSP module is used for battery power control and supercapacitor DC bus voltage constant control, and outputs control commands to the FPGA module. The FPGA module is used to generate PWM pulses based on control commands; The PWM pulses are used to synchronously control each converter through the drive link.

7. The system according to claim 6, characterized in that, The interleaved parallel Boost converter of the photovoltaic power generation unit integrates current sampling elements and voltage sampling elements; The sampling element is connected through the ADC sampling interface of the dedicated control unit to form a real-time acquisition hardware link for photovoltaic side current and voltage raw data; The DSP module processes the acquired raw data and issues a duty cycle command, which is transmitted to the Boost converter through the PWM drive interface.

8. The system according to claim 1, characterized in that, The dedicated control unit is equipped with a power distribution function, which divides the power to be mitigated into instantaneous power components and continuous energy components through preset power component distribution logic. The instantaneous power component is transmitted to the bidirectional Buck-Boost converter of the supercapacitor energy storage branch through the drive link; The continuous energy component is transmitted to the bidirectional Buck-Boost converter of the battery energy storage branch through the drive link.

9. The system according to claim 6, characterized in that, The battery power control and the supercapacitor DC bus voltage constant control are implemented based on a DSP+FPGA heterogeneous hardware architecture. The DSP module is responsible for power control and voltage control, and outputs a command reference. The FPGA module receives instructions processed by the DSP module and generates drive signals, and controls the power adjustment of each converter based on the drive signals.

10. A method for stabilizing the DC bus voltage of an AC / DC microgrid, characterized in that, include: Photovoltaic power is transmitted to the DC bus via the Boost converter of the photovoltaic power generation unit; The supercapacitor energy storage branch and the battery energy storage branch of the hybrid energy storage unit are connected in parallel to the DC bus through independent bidirectional Buck-Boost converters. The grid-connected inverter of the AC inverter grid-connected unit converts DC bus power into AC power. After acquiring DC bus voltage, voltage, current and energy storage state of charge information through the sampling link of the dedicated control unit, the system generates adjustment commands through calculation and transmits the adjustment commands through the drive link to the Boost converter of the photovoltaic power generation unit, the bidirectional Buck-Boost converter of the hybrid energy storage unit and the AC inverter grid-connected unit respectively, so as to stabilize the DC bus voltage and maintain its stability.

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