Low-voltage line single-phase distributed energy storage system and control method thereof

Abstract

The invention relates to the technical field of low-voltage single-phase energy storage, and discloses a low-voltage line single-phase distributed energy storage system and a control method thereof.The energy storage system comprises a control system and a plurality of distributed independent energy storage systems, and each independent energy storage system comprises a controller, a converter and an energy storage unit; the controllers are respectively connected with the converters and the energy storage units, the energy storage units are connected with the single-phase low-voltage lines through the converters, the controllers are in communication connection with the control system, and the control system controls the converters to charge and discharge electric energy according to the power grid environment where the energy storage units are located. The safety detection of each independent energy storage system is realized through a single battery self-checking device and a system self-checking component of each independent energy storage system, the charging and discharging states of each battery are safely controlled, and each independent energy storage system realizes precise voltage support and flexible energy buffering through single-phase independent regulation and control; dynamic optimization of single-phase electric energy quality is realized by adopting a power control strategy, and the technical blank of traditional centralized energy storage in the field of single-phase electric energy regulation and control is filled.

Description

Technical Field

[0001] The present invention relates to the technical field of low-voltage single-phase energy storage, and in particular to a low-voltage line single-phase distributed energy storage system and a control method thereof. Background Art

[0002] Voltage deviation of power supply lines is usually manifested as the voltage of the low-voltage bus being lower or higher than the normal range. Especially during peak power consumption periods, the voltage may drop significantly due to excessive load. During low power consumption periods, the voltage increases due to reduced load.

[0003] The voltage fluctuations in power supply lines caused by the integration of distributed photovoltaic power generation into the grid are a major issue hindering grid integration. During abundant daytime sunlight, distributed photovoltaic power generation provides a large amount of active power to the power supply lines, causing excessively high voltages. To mitigate this voltage increase, power supply companies reduce the voltage at the transformer output. At night or during periods of low sunlight, the power supply line voltage is often low due to user load, a major issue hindering grid integration. In single-phase power supply scenarios, particularly in rural power grids and older urban communities, implementing power regulation using single-phase distributed energy storage on low-voltage lines has been a pressing industry challenge.

[0004] Traditional centralized energy storage systems utilize three-phase converters, but they suffer from complex three-phase balancing control, low utilization due to capacity redundancy, and high hardware costs. Especially on low-voltage single-phase lines, three-phase energy storage is difficult to deploy directly at the end of the line, making it impossible to achieve precise voltage support. Existing single-phase energy storage systems lack efficient power conversion control strategies and have high hardware design redundancy, resulting in low energy efficiency and high costs.

[0005] In view of this, the applicant innovatively designed the low-voltage line single-phase distributed energy storage system and its control method of this application, which is suitable for single-phase power supply scenarios such as rural power grids and old urban communities, and is used to solve voltage fluctuations, three-phase imbalance and low voltage problems at the end. Summary of the Invention

[0006] In order to overcome the shortcomings of the existing technology, the present invention provides a low-voltage line single-phase distributed energy storage system and a control method thereof, which realizes dynamic optimization of power quality and efficient energy management through a modular design of a single-phase bidirectional power conversion system (PCS) and an intelligent control strategy.

[0007] The present invention is achieved through the following technical solutions: A low-voltage line single-phase distributed energy storage system includes a control system and several distributed independent energy storage systems. Each independent energy storage system includes a controller, a converter and an energy storage unit. The controller is connected to the converter and the energy storage unit respectively. The converter is a single-phase bidirectional PCS (AC / DC) converter. The energy storage unit is connected to the single-phase low-voltage line where it is located through the converter. Each controller is communicatively connected to the control system. The control system controls the converter to charge and discharge electric energy according to the power grid environment in which the energy storage unit is located. The control system also implements safety detection of each independent energy storage system through the individual battery self-test devices and system self-test components of each independent energy storage system, safely controls the charge and discharge status of each battery, and independently regulates the single phase of each independent energy storage system to achieve precise voltage support and flexible energy buffering. A power control strategy is used to achieve dynamic optimization of single-phase power quality.

[0008] Preferably, the energy storage unit includes a battery stack self-test device, which includes a total current sensor installed at the confluence of multiple battery clusters for collecting the total current of a single battery stack, a total voltage sensor for collecting the total voltage of a single battery stack, an insulation detector for collecting the insulation signal of a single battery stack, a PCS detection device for collecting the fault status of the power system of a single battery stack, a three-level master control detection device for collecting whether the battery signal of a single battery stack is abnormal, and a fire protection system detection device for protecting the energy storage system.

[0009] Preferably, the converter includes a power conversion unit, a control unit, a drive unit, a detection unit and a communication unit. The power conversion unit is responsible for realizing the bidirectional conversion of electric energy; The control unit generates corresponding control strategies based on external instructions and detection signals; In order to overcome the shortcomings of the existing technology, the present invention provides a low-voltage line single-phase distributed energy storage system and a control method thereof, which realizes dynamic optimization of power quality and efficient energy management through a modular design of a single-phase bidirectional power conversion system (PCS) and an intelligent control strategy.

[0010] The present invention is achieved through the following technical solutions: A low-voltage line single-phase distributed energy storage system includes a control system and several distributed independent energy storage systems. Each independent energy storage system includes a controller, a converter and an energy storage unit. The controller is connected to the converter and the energy storage unit respectively. The converter is a single-phase bidirectional PCS (AC / DC) converter. The energy storage unit is connected to the single-phase low-voltage line where it is located through the converter. Each controller is communicatively connected to the control system. The control system controls the converter to charge and discharge electric energy according to the power grid environment in which the energy storage unit is located. The control system also implements safety detection of each independent energy storage system through the individual battery self-test devices and system self-test components of each independent energy storage system, safely controls the charge and discharge status of each battery, and independently regulates the single phase of each independent energy storage system to achieve precise voltage support and flexible energy buffering. A power control strategy is used to achieve dynamic optimization of single-phase power quality.

[0011] Preferably, the energy storage unit includes a battery stack self-test device, which includes a total current sensor installed at the confluence of multiple battery clusters for collecting the total current of a single battery stack, a total voltage sensor for collecting the total voltage of a single battery stack, an insulation detector for collecting the insulation signal of a single battery stack, a PCS detection device for collecting the fault status of the power system of a single battery stack, a three-level master control detection device for collecting whether the battery signal of a single battery stack is abnormal, and a fire protection system detection device for protecting the energy storage system.

[0012] Preferably, the converter includes a power conversion unit, a control unit, a drive unit, a detection unit and a communication unit. The power conversion unit is responsible for realizing the bidirectional conversion of electric energy; The control unit generates corresponding control strategies based on external instructions and detection signals; The communication unit exchanges data with the control system to achieve coordinated operation of the system.

[0013] The power conversion unit adopts a two-stage topology, with a bidirectional DC-DC converter at the front stage and a bidirectional DC-AC inverter at the back stage. It uses a bidirectional Buck-Boost circuit and a full-bridge inverter circuit. In charging mode, the rectified DC voltage on the grid side is stepped down to charge the battery. In discharging mode, the battery voltage is boosted to an appropriate DC bus voltage, and the DC bus voltage is inverted into AC power with the same frequency and phase as the grid. At the same time, the amplitude and phase of the output AC power are adjusted through PWM modulation to achieve seamless connection with the grid and precise power control.

[0014] A control method for a low-voltage line single-phase distributed energy storage system comprises the following steps: E. Initialization and self-test: After the controller is powered on, it initializes the system and peripheral modules, reads system parameters, and completes the initialization and self-test of the power device drive circuit; F. The controller regularly samples and pre-processes the sampled data by filtering and normalizing it to provide accurate data input for the control system and the PCS control unit. The PCS control unit generates the corresponding power control strategy mode based on external instructions and detection signals. G. The controller calculates the PWM duty cycle of the power switch tube according to the current system operating mode and outputs a control signal; H. The controller monitors the system operating status in real time. Once a fault signal is detected, it immediately triggers the protection mechanism, blocks the PWM output, and cuts off the power circuit. At the same time, it interacts with the control system through the communication interface, receives external commands, and uploads system operating parameters and status information.

[0015] The power control strategy includes a double closed-loop control strategy of a current inner loop and a voltage outer loop and a vector control strategy based on grid voltage orientation.

[0016] In the dual closed-loop control strategy, the voltage outer loop outputs a current setpoint value via a PI regulator based on the deviation between the battery voltage setpoint and the actual detected value; the current inner loop compares the actual current detected value with the setpoint value, controls the duty cycle of the power switch tube through PWM modulation, and adjusts the current to achieve precise control of the battery charging and discharging current, ensuring safe and stable operation of the battery.

[0017] The vector control strategy uses a phase-locked loop (PLL) to precisely track the phase and frequency of the grid voltage, converting the AC voltage and current into a synchronously rotating coordinate system to achieve decoupled control of active and reactive power. Based on external commands, the strategy controls active power by adjusting the d-axis current component and reactive power by adjusting the q-axis current component, ensuring precise power interaction between the PCS and the grid.

[0018] The low-voltage single-phase distributed energy storage system of the present invention utilizes a modular design, a single-phase bidirectional power conversion system (PCS), and an intelligent control strategy. Each independent energy storage system independently regulates the single phase to achieve precise voltage support and flexible energy buffering, enabling dynamic optimization of power quality and efficient energy management. This system utilizes a power control strategy to achieve dynamic optimization of single-phase power quality. This system addresses the voltage fluctuations, three-phase imbalances, and low voltage at the end of low-voltage single-phase lines that are difficult to address with existing three-phase energy storage technologies, reducing hardware costs by 30% to 50%. Furthermore, the system reduces line transmission losses through local balancing of the "solar-storage-load" single phase. This system provides a new solution for deploying distributed energy storage systems directly at the end of lines in rural power grids and older urban communities, filling a technological gap in traditional centralized energy storage in the field of single-phase power regulation. The system can be installed in homes, industrial facilities, or commercial buildings. It can serve as a grid regulator and backup power source; on the user side, it provides power security and peak-shaving and valley-shifting functions; and on the renewable energy generation side, it can smooth the output power of renewable energy generators, improving the stability and reliability of the grid.

[0019] This invention uses an efficient and reliable single-phase bidirectional power conversion system (PCS) to achieve bidirectional conversion between DC and AC power, meeting the needs of various application scenarios. It achieves conversion efficiency ≥ 95%, harmonic distortion (THD) < 5%, and DC voltage ripple ≤ ±2%. It reduces hardware costs by 30%-50% and improves overall energy efficiency by 10%-15%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the overall system architecture diagram; Figure 2 Schematic diagram of self-test of converter and energy storage unit; Figure 3 Schematic diagram of the control strategy model. DETAILED DESCRIPTION

[0021] The following will be combined with the accompanying drawings in the embodiments of the invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The programs involved in or relied upon in the following embodiments are conventional or simple programs in the field of technology, and those skilled in the art can make conventional selections or adaptive adjustments based on specific application scenarios. Unless otherwise specified, the unit modules, parts, structures, mechanisms, or sensors involved in the following embodiments are all conventional commercially available products. Example

[0022] Referring to the figure, a low-voltage line single-phase distributed energy storage system includes a control system (not shown) and several distributed independent energy storage systems. Each independent energy storage system includes a controller (not shown), a converter and an energy storage unit. The controller is connected to the converter and the energy storage unit. The converter is a single-phase bidirectional PCS (AC / DC) converter. The energy storage unit is connected to the single-phase low-voltage line where it is located through the converter. Each controller is communicated with the control system. The control system controls the converter to charge and discharge electric energy according to the grid environment in which the energy storage unit is located, and realizes safety detection of each independent energy storage system through the single battery self-test device and system self-test component of each independent energy storage system, and safely controls the charge and discharge status of each battery. Each independent energy storage system 1 is independently regulated to achieve precise voltage support and flexible energy buffering, and a power control strategy is adopted to achieve dynamic optimization of single-phase power quality. The energy storage unit includes a battery stack self-test device, which includes a total current sensor installed at the confluence of multiple battery clusters to collect the total current of a single battery stack; a total voltage sensor to collect the total voltage of a single battery stack; an insulation detector to collect insulation signals from a single battery stack; a PCS detection device to collect power system fault status of a single battery stack; a three-level master control detection device to detect abnormal battery signals in a single battery stack; and a fire protection system detection device to protect the energy storage system. The independent energy storage system monitors the charge and discharge status through the battery self-test device and system self-test components.

[0023] The single-phase bidirectional PCS (AC / DC) converter includes a power conversion unit, a control unit, a drive unit, a detection unit and a communication unit. The power conversion unit is responsible for realizing bidirectional conversion of electric energy; the control unit generates corresponding control strategies according to external instructions and detection signals; the drive unit amplifies the control signal and drives the power device to work; the detection unit monitors parameters such as voltage and current in real time and feeds back to the control system through the communication unit; the communication unit exchanges data with the control system (including the battery management system BMS, the power grid monitoring system, etc.) to realize coordinated operation of the system.

[0024] The power conversion unit adopts a two-stage topology, with a bidirectional DC-DC converter in the front stage and a bidirectional DC-AC inverter in the back stage. It utilizes a bidirectional Buck-Boost circuit and a full-bridge inverter circuit. This simple structure and flexible control enable buck-boost functionality over a wide voltage range. For example, when the battery voltage range is 200-400V and the DC bus voltage is set at 600V, the Buck-Boost circuit effectively performs voltage conversion. In charging mode, the rectified DC voltage from the grid is stepped down to charge the battery. In discharging mode, the battery voltage is stepped up to the appropriate DC bus voltage and then inverted into AC power with the same frequency and phase as the grid. PWM modulation is used to adjust the amplitude and phase of the output AC power, achieving seamless grid connection and precise power control. The preferred solution utilizes high-quality components, redundant design, and multiple protection mechanisms to ensure long-term stable operation of the PCS under complex operating conditions, with a mean time between failures (MTBF) of at least 10,000 hours. Silicon carbide (SiC) MOSFETs are preferred for power switches, due to their low on-resistance, fast switching speed, and high-temperature resistance. These characteristics effectively reduce conduction and switching losses, thereby improving system efficiency. For example, a 1200V, 200A SiC MOSFET has a typical on-resistance of only 10mΩ, significantly reducing overheating under high-frequency switching conditions. Furthermore, SiC MOSFETs as power switches enable the inverter to exhibit excellent dynamic response and low harmonic output characteristics. Preferably, a fast recovery diode can be used to absorb the reverse voltage spike during switch turn-off, protecting the power components. The bidirectional buck-boost circuit utilizes a high-permeability iron powder core with tightly packed and evenly distributed windings, reducing the inductor's DC and AC resistances and minimizing copper and iron losses. For example, at a switching frequency of 50kHz and a maximum current of 30A, an inductor with an inductance of 1mH is designed. Furthermore, a high-frequency isolation transformer is preferably used to electrically isolate the DC and AC sides, while also matching the output voltage to the grid voltage. The transformer core uses low-loss ferrite material and the winding uses multi-strand twisted wire to reduce the loss caused by skin effect and proximity effect, and improve the transformer efficiency and power density.

[0025] The driver chip of the drive unit preferably adopts the IR2110 driver chip, which has high driving capability, fast switching speed and complete protection function. Electrical isolation is performed by optical coupling to prevent the power circuit from interfering with the control circuit. At the same time, R and C absorption circuits are added to the output end of the driver chip to suppress the voltage spikes at the moment of turning on and off the power switch tube, thereby protecting the chip and power devices.

[0026] The detection unit uses a resistor divider to detect the DC side voltage and the AC side voltage. Through a high-precision resistor network, the high voltage is converted into a low-voltage signal suitable for sampling by the controller ADC, and is filtered to remove high-frequency noise interference. For example, for a 700V DC bus voltage, a resistor divider with an accuracy of 0.1% is used to reduce the voltage to a range of 0-3V for ADC acquisition. Preferably, Hall current sensors are used in the DC side and AC side main circuits to detect current. They have the advantages of fast response speed, good linearity, and strong isolation performance, and can accurately measure bidirectional current. The detection signal is amplified and filtered and then input into the controller to implement functions such as overcurrent protection and power control.

[0027] The control method of the above-mentioned low-voltage line single-phase distributed energy storage system includes the following steps: A. Initialization and self-test: After the controller is powered on, it initializes the system and peripheral modules, reads the system parameters, and completes the initialization and self-test of the power device drive circuit. Figure 2 shown.

[0028] B. The controller samples regularly and performs pre-processing such as filtering and normalization on the sampled data to provide accurate data input for the control system and the PCS control unit. The PCS control unit generates corresponding power control strategy modes based on external instructions and detection signals, such as high and low voltage modes, peak and valley modes, and time modes, to meet the needs of different scenarios. Figure 3 For example, the inverter is controlled according to the grid voltage. When the grid voltage is high and the grid power consumption is low, the inverter absorbs energy from the grid. When the grid voltage is low and the grid power consumption is peak, the inverter releases energy to the grid. The inverter is synchronized with the grid frequency. Each bidirectional inverter of the distributed energy storage system operates independently. The system can implement different control strategy modes for different independent energy storage systems. C. The controllers of different independent energy storage systems calculate the PWM duty cycle of the power switch tube according to the current system operating mode and output the control signal; D. The drive unit amplifies the control signal to drive the power device. The detection unit monitors parameters such as voltage and current in real time and feeds them back to the control system through the communication unit. The communication unit exchanges data with the control system (including the battery management system (BMS) and power grid monitoring system) to achieve coordinated operation of the system. E. The controller monitors the system operating status in real time. Once a fault signal is detected, it immediately triggers the protection mechanism, blocks the PWM output, and cuts off the power circuit. At the same time, it interacts with the control system through the communication interface, receives external commands, and uploads system operating parameters and status information.

[0029] In step C, the power control strategy includes a dual closed-loop control strategy of a current inner loop and a voltage outer loop and a vector control strategy based on grid voltage orientation.

[0030] In the dual closed-loop control strategy, the voltage outer loop outputs a current setpoint value via a PI regulator based on the deviation between the battery voltage setpoint and the actual detected value; the current inner loop compares the actual current detected value with the setpoint value, controls the duty cycle of the power switch tube through PWM modulation, and adjusts the current to achieve precise control of the battery charging and discharging current, ensuring safe and stable operation of the battery.

[0031] The described vector control strategy uses a phase-locked loop (PLL) to accurately track the phase and frequency of the grid voltage, converting the AC side voltage and current to a synchronously rotating coordinate system to achieve decoupled control of active power and reactive power. Based on external instructions (such as power instructions from the grid dispatcher), the strategy controls active power by adjusting the d-axis current component and reactive power by adjusting the q-axis current component, ensuring precise power interaction between the PCS and the grid. Inverter mode power conversion: Output voltage RMS: For a single-phase inverter, if the DC side voltage is Vdc , using sinusoidal pulse width modulation (SPWM) technology, under ideal conditions, the output AC voltage is effective value Vac The relationship with the DC side voltage is ,in M is the modulation ratio, and its value range is usually between 0 and 1.

[0032] Output power: output active power Pac It can be expressed as ,in Iac is the output AC current effective value, cos φ is the power factor. In the case of a purely resistive load, cos φ =1, then Assuming the inverter efficiency is η , then the input DC power Pdc is .

[0033] Single-phase bidirectional PCS performs Fourier transform on the AC side current AC side current i ac (t) is a sinusoidal signal, but it may have harmonics due to nonlinear loads or control strategies.

[0034] Also using Fourier series expansion

[0035] The coefficient calculation method is similar to the above:

[0036] Rectification mode power conversion: Input current effective value: In a single-phase rectifier, the AC input voltage effective value is Vac , the effective value of AC input current is Iac , the DC output voltage is Vdc , the DC output current is Idc Without considering the loss, according to the power conservation law, the AC input power is equal to the DC output power, that is For a diode rectifier bridge, under a sinusoidal input voltage, the effective value of the input current is Iac With DC output current Idc The relationship is (When the load is resistive and harmonics are ignored).

[0037] Output DC voltage: For a single-phase uncontrolled rectifier bridge, under ideal conditions where line resistance and device voltage drop are ignored, the average output DC voltage is Vdc and the effective value of the input AC voltage Vac The relationship is If it is a controlled rectifier, by controlling the trigger angle α , the output DC voltage can be changed, and the relationship is: .

[0038] Single-phase bidirectional PCS performs Fourier transform on DC side voltage and DC side current respectively Fourier transform: For the DC side voltage and current vdc(t) and current idc(t), assuming that their fluctuations are periodic with a period of T, the Fourier series expansion is as follows:

[0039] Where Vdc0 and Vdc2 are DC components, is the fundamental angular frequency, and the coefficients anV, bnV, anI, and bnI can be calculated using the integral formula:

[0040] In step D, the protection mechanism includes Overvoltage protection: Overvoltage protection circuits are installed on both the DC and AC sides. When the voltage exceeds the set threshold, the control circuit immediately blocks the drive signal to the power switch, halting power conversion and preventing further voltage increases that could damage the equipment. Simultaneously, a hardware bleeder circuit is activated to dissipate excess energy in the resistor, rapidly reducing the voltage. Overcurrent protection: A detection circuit monitors the current in real time. When the current exceeds a certain multiple of the rated value, overcurrent protection is triggered. The control algorithm first reduces the PWM duty cycle to attempt to lower the current. If the current remains excessive, the drive signal is quickly blocked, shutting off the main circuit current to prevent damage to the power components due to overcurrent. Overheat protection: A temperature sensor is installed on the power device heat sink to monitor the device temperature in real time. When the temperature exceeds the allowable operating temperature, the fan is activated to enhance heat dissipation. If the temperature continues to rise to the dangerous threshold, the PCS operation is immediately stopped and resumed after the temperature drops, preventing power device failure due to overheating. Short-circuit protection: Once a short-circuit fault is detected on the DC or AC side, the power circuit is quickly disconnected and an alarm signal is issued. Short-circuit protection should have a fast response characteristic, operating within a very short time (such as tens of microseconds) to protect equipment and personnel.

[0041] The PCS achieves conversion efficiency exceeding 95% across the full load range of this application, minimizing energy loss. It precisely controls power flow and volume, enabling both DC conversion to AC for grid connection and AC conversion to DC for storage, with power control accuracy within ±5%. The total harmonic distortion (THD) of the output AC power is less than 5%, meeting grid access standards. The DC-side voltage ripple is controlled within ±2%, ensuring stable operation of back-end equipment.

[0042] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A low-voltage line single-phase distributed energy storage system, characterized by: It includes a control system and several distributed independent energy storage systems. Each independent energy storage system includes a controller, an inverter and an energy storage unit. The controller is connected to the inverter and the energy storage unit. The inverter is a single-phase bidirectional PCS (AC / DC) inverter. The energy storage unit is connected to the single-phase low-voltage line where it is located through the inverter. Each controller is communicated with the control system. The control system controls the inverter to charge and discharge electric energy according to the grid environment where the energy storage unit is located, and realizes safety detection of each independent energy storage system through the single battery self-test device and system self-test component of each independent energy storage system, and safely controls the charging and discharging status of each battery. Each independent energy storage system is independently regulated in a single phase to achieve precise voltage support and flexible energy buffering, and adopts a power control strategy to achieve dynamic optimization of single-phase power quality.

2. The low-voltage line single-phase distributed energy storage system according to claim 1, characterized in that: The energy storage unit includes a battery stack self-test device installed at the confluence of multiple battery clusters, a total current sensor for collecting the total current of a single battery stack, a total voltage sensor for collecting the total voltage of a single battery stack, an insulation detector for collecting the insulation signal of a single battery stack, a PCS detection device for collecting the fault status of the power system of a single battery stack, a three-level master control detection device for collecting whether the battery signal of a single battery stack is abnormal, and a fire protection system detection device for protecting the energy storage system.

3. The low-voltage line single-phase distributed energy storage system according to claim 1, characterized in that: The converter includes a power conversion unit, a control unit, a drive unit, a detection unit and a communication unit. The power conversion unit is responsible for realizing bidirectional conversion of electric energy. The control unit generates corresponding control strategies based on external instructions and detection signals; The drive unit amplifies the control signal and drives the power device to work; The detection unit monitors parameters such as voltage and current in real time and feeds back to the control system through the communication unit; The communication unit exchanges data with the control system to achieve coordinated operation of the system.

4. The low-voltage line single-phase distributed energy storage system according to claim 3, characterized in that: The power conversion unit adopts a two-stage topology, with a bidirectional DC-DC converter at the front stage and a bidirectional DC-AC inverter at the back stage. It uses a bidirectional Buck-Boost circuit and a full-bridge inverter circuit. In charging mode, the rectified DC voltage on the grid side is stepped down to charge the battery. In discharging mode, the battery voltage is boosted to an appropriate DC bus voltage, and the DC bus voltage is inverted into AC power with the same frequency and phase as the grid. At the same time, the amplitude and phase of the output AC power are adjusted through PWM modulation to achieve seamless connection with the grid and precise power control.

5. A control method for a low-voltage line single-phase distributed energy storage system according to any one of claims 1 to 4, characterized in that: The following steps are involved: A. Initialization and self-test: After the controller is powered on, it initializes the system and peripheral modules, reads system parameters, and completes the initialization and self-test of the power device drive circuit; B. The controller regularly samples and pre-processes the sampled data by filtering and normalizing it to provide accurate data input for the control system and the PCS control unit. The PCS control unit generates the corresponding power control strategy mode based on external instructions and detection signals. C. The controller calculates the PWM duty cycle of the power switch tube according to the current system operating mode and outputs a control signal; D. The controller monitors the system's operating status in real time. Once a fault signal is detected, it immediately triggers the protection mechanism, blocking the PWM output and disconnecting the power circuit. Simultaneously, it interacts with the control system through a communication interface, receiving external commands and uploading system operating parameters and status information.

6. The control method according to claim 5, characterized in that: The power control strategy includes a double closed-loop control strategy of a current inner loop and a voltage outer loop and a vector control strategy based on grid voltage orientation.

7. The control method according to claim 6, characterized in that: In the dual closed-loop control strategy, the voltage outer loop outputs a current given value through a PI regulator based on the deviation between the battery voltage set value and the actual detected value; The current inner loop compares the actual current detection value with the given value, controls the duty cycle of the power switch tube through PWM modulation, adjusts the current, and achieves precise control of the battery charge and discharge current to ensure safe and stable operation of the battery.

8. The control method according to claim 6, wherein: The described vector control strategy uses a phase-locked loop (PLL) to accurately track the phase and frequency of the grid voltage, converting the AC side voltage and current into a synchronously rotating coordinate system to achieve decoupled control of active power and reactive power. Based on external commands, the strategy controls active power by adjusting the d-axis current component and reactive power by adjusting the q-axis current component, ensuring precise power interaction between the PCS and the grid.

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