A low-voltage standby automatic transfer control method and device compatible with photovoltaic and energy storage

Abstract

This invention discloses a low-voltage standby automatic transfer control method and device compatible with photovoltaic (PV) and energy storage, applied to a primary / standby power switching system. The method includes: at the moment of a mains power failure, utilizing an integrated hybrid inverter module, before the ATS physically disconnects the mains power, dynamically buffering the load through energy storage batteries to compensate for the difference between the power required by the load and the actual output power of the PV, thereby maintaining the stability of the load-side voltage and frequency; seamlessly switching from mains power to a combined PV and energy storage power supply mode without affecting the power quality on the load side; and after the switch is completed, dynamically adjusting the discharge depth and rate of the energy storage based on real-time light intensity and load changes using an adaptive impedance matching algorithm. This invention, by setting up a hybrid inverter integrating a high-speed DSP controller and a voltage source inverter topology, enables smooth, efficient, and seamless switching and coordinated power supply between the grid, PV, energy storage, and load during automatic grid switching.

Description

Technical Field

[0001] This invention relates to the field of power system automation control technology, specifically to a low-voltage backup automatic transfer control method and device suitable for low-voltage distribution networks that can be deeply integrated with distributed photovoltaic (PV) power generation systems and energy storage systems (ESS). Background Technology

[0002] In modern low-voltage power distribution systems, automatic transfer switches (ATS) are core devices that ensure the continuity of power supply to critical loads. Their basic function is to automatically switch the load to a backup power source (such as a diesel generator) when a mains power (mains) failure is detected. With technological advancements and the popularization of distributed energy, photovoltaic power generation systems and energy storage systems are increasingly being used as backup power sources or operating in parallel with the mains power source.

[0003] However, directly applying traditional ATS to low-voltage systems that include photovoltaics and energy storage still presents the following technical challenges:

[0004] (1) Switching interruption problem: Traditional ATSs mostly use a mechanical switching method of "break-before-make", which has a power interruption time of milliseconds. For sensitive loads in fields such as hospitals, data centers, and precision manufacturing, such interruption is unacceptable and may lead to serious consequences such as equipment shutdown and data loss.

[0005] (2) Photovoltaic fluctuation impact: Photovoltaic power generation is significantly intermittent and fluctuating. When the mains power fails, if the lighting conditions change drastically (such as cloud cover), the photovoltaic output power will drop sharply. If the load is directly switched to the photovoltaic system at this time, the system voltage may collapse due to insufficient power, and the switching will fail.

[0006] (3) Low system efficiency: Existing compatibility solutions are usually simple stacking of components, lacking an integrated and coordinated control strategy. For example, before and after switching, the maximum power point of photovoltaic, the charging and discharging state of energy storage and the output impedance of inverter are not optimized and matched, resulting in large energy loss during conversion and transmission, and low overall system operating efficiency.

[0007] (4) Incompatible control logic: Although some existing technologies attempt to combine energy storage and photovoltaics, for example through isolated inverters or multi-function switching devices, their designs are not specifically optimized for the challenges of low-voltage (<1000V) systems. These solutions are often complex to control, costly, and do not propose an integrated design that can use energy storage as a "dynamic buffer bridge" to achieve zero-interruption switching and adaptively adjust the energy flow according to real-time operating conditions to maximize efficiency.

[0008] Therefore, the market urgently needs a backup automatic transfer control technology designed specifically for low-voltage systems that can deeply integrate photovoltaics and energy storage to achieve truly seamless, efficient, and intelligent switching.

[0009] To address this, this application proposes a low-voltage standby automatic transfer control method and device that is compatible with photovoltaic and energy storage. It is specifically designed for low-voltage systems and can deeply integrate photovoltaic and energy storage to achieve truly seamless, efficient, and intelligent switching, thereby solving the aforementioned technical problems. Summary of the Invention

[0010] The main objective of this invention is to provide a low-voltage automatic transfer switch control method and device compatible with photovoltaic and energy storage. It aims to solve the technical problems of power interruption, voltage surge, low system efficiency, and damage to sensitive loads during the switching process caused by the intermittency and volatility of photovoltaic power generation when traditional automatic transfer switches are connected to new energy sources. The invention achieves smooth, efficient, and seamless switching and coordinated power supply between the power grid, photovoltaic, energy storage, and load, thereby solving the technical problems mentioned in the background art.

[0011] The present invention solves the above-mentioned technical problems by adopting the following technical solutions:

[0012] A low-voltage automatic transfer switch control method compatible with photovoltaic and energy storage is applied to a set of main and backup power switching systems, including:

[0013] In the instant of a mains power failure, instead of performing the traditional "disconnect first, connect later" hard switching, a set of integrated hybrid inverter modules is used to dynamically buffer the load through energy storage batteries before the ATS physically disconnects the main power supply. This precisely compensates for the difference between the power required by the load and the actual output power of the photovoltaic system at that time, so as to maintain the stability of the load-side voltage and frequency.

[0014] Seamless switching from mains power to photovoltaic energy storage combined power supply mode is achieved without any noticeable power quality issues on the load side.

[0015] After the switch is completed, the discharge depth and rate of the energy storage are dynamically adjusted according to the real-time light intensity and load changes through an adaptive impedance matching algorithm.

[0016] Preferably, the mains power failure is confirmed by a monitoring module continuously collecting electrical parameters of designated key nodes of the system at a high frequency (e.g., kHz level). The electrical parameters include: the voltage, frequency, and phase of the main grid; the output voltage, current, and ambient light intensity of the photovoltaic array; the state of charge (SOC), terminal voltage, and current of the energy storage battery; and the real-time power demand on the load side.

[0017] Among them, the main grid voltage passes through Instantaneous voltage at time t Collect and detect data, and calculate its effective value. and frequency The calculation formula is as follows: , Main power grid The instantaneous voltage value at time t. One cycle of the grid voltage, The root mean square (RMS) value of the main grid voltage;

[0018] Photovoltaic output power is measured in real time by the output voltage of the photovoltaic array. and current The calculation is as follows: , For photovoltaic arrays in Instantaneous output power at a given moment For photovoltaic arrays in The instantaneous output voltage at a given moment. For photovoltaic arrays in Instantaneous output current at any given moment;

[0019] Among these methods, the ampere-hour integral method is used to dynamically estimate the state of charge (SOC) of energy storage, and the calculation formula is as follows: , for The state of charge of the energy storage at any given moment. Initial time The state of charge, This refers to the rated capacity (Ah) of the energy storage battery. This is the instantaneous current of the energy storage battery (negative for charging, positive for discharging). The charge / discharge coulombic efficiency of the battery;

[0020] When the voltage amplitude and frequency of the main grid exceed the preset safety threshold and remain so for a specified period of time, it is determined that there is a mains power fault in the main grid. The determination formula is as follows:

[0021]

[0022]

[0023] in, and These represent the voltage fault flag and the frequency fault flag, respectively. If the result of the judgment formula is 1, then there is a mains power fault in the mains power grid; otherwise, there is a mains power fault in the mains power grid. and These represent the preset lower and upper voltage thresholds, respectively. The rated frequency of the power grid (e.g., 50Hz or 60Hz). The maximum allowable frequency deviation threshold, The effective value of the main grid voltage. This refers to the real-time frequency of the main power grid.

[0024] Preferably, the specific operation process of the hybrid inverter module for dynamic buffering via energy storage battery includes:

[0025] L1. Measurement load side at Instantaneous voltage at time t and instantaneous current Calculate the active power of the real-time load. The calculation formula is as follows: ,in One cycle of the grid voltage;

[0026] L2. The hybrid inverter uses real-time monitored load power... and photovoltaic output power Calculate the power gap (The power that energy storage needs to compensate for) can be calculated using the following formula: ,in This is expressed as the reference output power of the energy storage system;

[0027] L3. Controls the energy storage system's precise output with a microsecond-level response speed. Power of size;

[0028] At this point, the reference current is calculated based on the energy storage power and the battery terminal voltage, using the following formula:

[0029]

[0030] in, This is the reference discharge current for the energy storage system. This represents the real-time terminal voltage of the energy storage battery.

[0031] From the load side's perspective, the required total power is now... Depend on Together with energy storage, the current on the grid side rapidly approaches zero.

[0032] Preferably, the hybrid inverter module employs a dual closed-loop PID control strategy, including current-loop PID control and voltage-loop PID control, to achieve high-precision and rapid tracking of the energy storage current, wherein:

[0033] (1) The inner current loop PID controller is based on the reference current of the energy storage system. With actual energy storage current The error is used to control the voltage of the output inverter bridge arm. The mathematical expression for the voltage control output of the PID (proportional-integral) controller is as follows:

[0034]

[0035] in, and These are the proportional and integral gain coefficients of the inner current loop, respectively, used to represent the PID controller transfer function operation to express the controller's sensitivity to current errors, i.e., the voltage regulation corresponding to a unit current error. This voltage control signal... Used to generate PWM to drive the inverter bridge arm;

[0036] (2) The voltage outer loop PID controller is based on the effective value of the target voltage on the load side. Compared with the actual load-side voltage RMS value The error is used to output the current reference signal of the energy storage system. The mathematical expression for the voltage control output of the PID (proportional-integral) controller is as follows:

[0037]

[0038] in, and These are the proportional and integral gain coefficients of the outer voltage loop, respectively, used to represent the operation of the PID controller's transfer function, expressing the controller's sensitivity to voltage errors, i.e., the current regulation corresponding to a unit voltage error.

[0039] Furthermore, the current inner loop controller here is used to generate a voltage control signal based on the current error in order to achieve rapid current tracking.

[0040] Furthermore, taking the formula of the current inner-loop PID controller as an example, the principle is explained. Here, the controller has a conversion function: The essence of the PID controller is a transfer function, and its function is to map the input signal (current error, unit: A) into the output control signal (voltage command, unit: V).

[0041] In this formula, the physical unit of the coefficient is the proportional gain coefficient. It is not a dimensionless constant; its physical unit is V / A (volts per ampere). Physically, it is equivalent to "virtual impedance," representing the controller's sensitivity to current errors, i.e., the voltage regulation corresponding to a unit current error. Similarly, the integral gain coefficient... The physical unit is V / (A·s).

[0042] Therefore, through coefficients and Dimensional conversion: the calculation result on the right side of the formula is in physical units the same as the voltage control signal on the left side. Keeping the values ​​consistent (both in volts V), this formula accurately expresses the physical mechanism of controlling the output current by adjusting the inverter port voltage.

[0043] The technical principle of voltage loop PID control output is the same.

[0044] Preferably, the adaptive impedance matching algorithm is used to predict the maximum output power of the photovoltaic system at the next moment (e.g., on the order of seconds) based on the real-time monitored irradiance, and dynamically adjusts the equivalent output impedance of the hybrid inverter and the discharge strategy of the energy storage system in conjunction with load changes, specifically including:

[0045] ST1. Based on Light intensity at any time and solar panel temperature The mathematical formula for constructing a prediction model for the maximum power point of photovoltaic power at this time is as follows:

[0046]

[0047] in, for The maximum output power of photovoltaic power is predicted at any time. for Peak photovoltaic power under standard test conditions at any given time and They are respectively Real-time light intensity and standard light intensity (1000 W / m²) 2 ), for Temperature coefficient of power at any time and These are the real-time solar panel temperature and the standard test temperature (25°C), respectively.

[0048] ST2. Based on the photovoltaic maximum power point prediction model, define The system efficiency that needs to be maximized at all times for:

[0049]

[0050] in, The system's instantaneous total efficiency. This represents the actual discharge power of the energy storage system. and These are the hybrid inverter's real-time monitored load power and photovoltaic output power, respectively.

[0051] ST3. Calculate the impedance matching adjustment factor for dynamically adjusting the depth of energy storage discharge. The relevant formula is:

[0052]

[0053] in, The value range of is [0, 1]. A value close to 1 indicates that the load should be prioritized. A value close to 0 indicates that photovoltaic power is being prioritized. To determine the photovoltaic maximum power point based on real-time light intensity and panel temperature. The time-based prediction model is used to represent the calculated maximum output power of the photovoltaic array;

[0054] ST4. Based on adjustment factors The optimal value is found through iterative updates using the gradient ascent method. To maximize system efficiency The calculation formula is as follows:

[0055]

[0056] in, This is the impedance matching adjustment factor for the next control cycle. This is the impedance matching adjustment factor before the update. For learning rate or iteration step size, Indicates system efficiency The gradient of the adjustment factor.

[0057] Preferably, after the main grid returns to normal and operates stably for a specified time, the synchronous grid connection procedure is initiated. The hybrid inverter uses phase-locked loop (PLL) technology to accurately synchronize the frequency, amplitude, and phase of the output voltage to be completely consistent with the main grid. Then, at the synchronization point, the ATS is closed to achieve a disturbance-free back-switch of the load, and the main and backup power switching system is then restored to the grid-connected operation state.

[0058] Preferably, the hybrid inverter employs phase-locked loop (PLL) technology to obtain the phase error through dq transformation, thereby synchronizing the frequency, amplitude, and phase of the output voltage to be completely consistent with the main grid. The transformation formula is as follows:

[0059]

[0060] in, The phase difference between the inverter output voltage and the grid voltage. and These are the components of the grid voltage in the dq synchronous rotating coordinate system. This refers to the output phase of the phase-locked loop inside the inverter.

[0061] A low-voltage standby automatic transfer switch control device compatible with photovoltaic and energy storage is applied to a set of main and standby power switching systems, and is connected to a set of energy storage devices and the automatic transfer switch (ATS) of the system for control. It is used to execute any of the aforementioned low-voltage standby automatic transfer switch control methods compatible with photovoltaic and energy storage, including:

[0062] The monitoring module is used to continuously collect electrical parameters of designated nodes of the system at high frequency, and is set with a specified safety threshold. When the main grid voltage amplitude and frequency in the collected parameters exceed the specified safety threshold, a "dynamic buffer bridge" function activation command is issued.

[0063] The hybrid inverter module, upon receiving a function activation command, utilizes a built-in high-speed DSP controller and voltage source inverter topology to achieve seamless energy flow between the photovoltaic DC, energy storage DC, and the load AC side, ensuring that the current flowing through the ATS mains side contacts is essentially zero, and then sends a switching processing signal.

[0064] The switching processing module is used to control the automatic transfer switch (ATS) to mechanically disconnect after receiving the switching processing signal;

[0065] After the automatic transfer switch (ATS) completes its switching, it uses an adaptive impedance matching algorithm to control the dynamic adjustment of energy storage charging and discharging.

[0066] In another aspect, the present invention also discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method described above.

[0067] In another aspect, the present invention also discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the steps of the method described above.

[0068] As can be seen from the above technical solution, the present invention provides a low-voltage standby automatic transfer control method and device compatible with photovoltaic and energy storage. Compared with the prior art, the present invention has the following advantages:

[0069] 1. This invention constructs a set of specially designed hybrid inverters, which integrate a high-speed DSP controller and an advanced voltage source inverter (VSI) topology. It can use a set of energy storage devices to "take over" the load in advance before the grid performs automatic switching. In this way, under low-voltage conditions, it can realize the seamless flow of energy between photovoltaic DC, energy storage DC and the load AC side, thereby eliminating all power gaps caused by switching interruptions during the switching process from grid power supply to off-grid power supply.

[0070] 2. By setting an adaptive impedance matching algorithm, this invention can adjust the discharge current of the energy storage and the PWM (Pulse Width Modulation) control strategy of the inverter in real time, so that the equivalent output impedance of the "photovoltaic + energy storage" power system achieves the best match with the load impedance, thereby maximizing system efficiency and avoiding the blind discharge of the energy storage system or the waste of photovoltaic power in traditional solutions.

[0071] It should be understood that the descriptions in this section are not intended to identify key or essential features of embodiments of the invention, nor are they intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Of course, implementing any product of the invention does not necessarily require achieving all of the advantages described above simultaneously. Attached Figure Description

[0072] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0073] Figure 1 This is a schematic diagram of the overall process of the present invention. Detailed Implementation

[0074] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0075] For details in the embodiments, please refer to Figure 1 .

[0076] like Figure 1As shown in the embodiments of this invention, the low-voltage standby automatic transfer control method compatible with photovoltaics and energy storage can, at the moment of a mains power failure, no longer perform the traditional "disconnect first, connect later" hard switching. Instead, it utilizes an integrated hybrid inverter module with energy storage batteries as a "dynamic buffer bridge." Before the ATS physically disconnects the mains power, the energy storage system intervenes in advance to accurately compensate for the difference between the power required by the load and the actual output power of the photovoltaic at that time, thereby maintaining the stability of the load-side voltage and frequency. This achieves a seamless switch from mains power to a "photovoltaic + energy storage" joint power supply mode without affecting the power quality on the load side. After the switch is completed, the system activates an adaptive impedance matching algorithm to dynamically adjust the discharge depth and rate of the energy storage based on real-time light intensity and load changes, maximizing the utilization rate of photovoltaic energy and improving the overall system efficiency by approximately 20%. It can mainly solve the technical problems of power interruption, voltage surge, low system efficiency and damage to sensitive loads during the switching process caused by the intermittency and volatility of photovoltaic power generation when traditional backup automatic transfer devices are connected to new energy sources. It can achieve smooth, efficient and seamless switching and coordinated power supply between the grid, photovoltaic, energy storage and load.

[0077] The specific implementation process includes the following steps:

[0078] Step 1: Real-time monitoring of the entire system under all operating conditions

[0079] Mains power failures are confirmed by continuously collecting electrical parameters of designated key nodes of the system at high frequencies (such as kHz) through the monitoring module. These electrical parameters include: voltage, frequency, and phase of the main grid; output voltage, current, and ambient light intensity of the photovoltaic array; state of charge (SOC), terminal voltage, and current of the energy storage battery; and real-time power demand on the load side. These data form the basis for all subsequent decisions and controls.

[0080] Among them, the main grid voltage passes through Instantaneous voltage at time t Collect and detect data, and calculate its effective value. and frequency The calculation formula is as follows: , Main power grid The instantaneous voltage value at time t. One cycle of the grid voltage, The root mean square (RMS) value of the main grid voltage;

[0081] Photovoltaic output power is measured in real time by the output voltage of the photovoltaic array. and current The calculation is as follows: , For photovoltaic arrays in Instantaneous output power at a given moment For photovoltaic arrays in The instantaneous output voltage at a given moment. For photovoltaic arrays in Instantaneous output current at any given moment;

[0082] Among these methods, the ampere-hour integral method is used to dynamically estimate the state of charge (SOC) of energy storage, and the calculation formula is as follows: , for The state of charge of the energy storage at any given moment. Initial time The state of charge, This refers to the rated capacity (Ah) of the energy storage battery. This is the instantaneous current of the energy storage battery (negative for charging, positive for discharging). The charge / discharge coulombic efficiency of the battery;

[0083] Step 2: Accurate diagnosis and prediction of main power grid faults

[0084] When the main grid voltage amplitude and frequency exceed the preset safety thresholds (e.g., voltage drop exceeding 15%, frequency deviation exceeding 0.5Hz) and remain there for a certain period of time (e.g., 20ms), the control system determines that there is a main grid fault. The purpose of this step is to quickly and accurately identify the operating conditions that require the automatic transfer switch to be activated.

[0085] Specifically, when the voltage amplitude and frequency of the main grid exceed a preset safety threshold and remain so for a specified period of time, a mains power fault is determined to exist in the main grid. The determination formula is as follows:

[0086]

[0087]

[0088] in, and These represent the voltage fault flag and the frequency fault flag, respectively. If the result of the judgment formula is 1, then there is a mains power fault in the mains power grid; otherwise, there is a mains power fault in the mains power grid. and These represent the preset lower and upper voltage thresholds, respectively. The rated frequency of the power grid (e.g., 50Hz or 60Hz). The maximum allowable frequency deviation threshold, The effective value of the main grid voltage. This refers to the real-time frequency of the main power grid.

[0089] Step 3: Activation of the dynamic buffer bridge and power pre-compensation

[0090] When a main grid fault is detected, the ATS is not immediately commanded to operate. Instead, a command is immediately sent to the hybrid inverter module to activate the "dynamic buffer bridge" function.

[0091] The specific operation process of the hybrid inverter module using energy storage batteries for dynamic buffering (activating the "dynamic buffer bridge" function) includes:

[0092] L1. Measurement load side at Instantaneous voltage at time t and instantaneous current Calculate the active power of the real-time load. The calculation formula is as follows: ,in One cycle of the grid voltage;

[0093] L2. Based on the real-time monitored load power and photovoltaic output power Calculate the power gap (The power that energy storage needs to compensate for) can be calculated using the following formula: ,exist This is expressed as the reference output power of the energy storage system;

[0094] L3. Controls the energy storage system's precise output with a microsecond-level response speed. Power of size;

[0095] At this point, the reference current is calculated based on the energy storage power command and the battery terminal voltage, using the following formula:

[0096]

[0097] in, This is the reference discharge current for the energy storage system. This represents the real-time terminal voltage of the energy storage battery.

[0098] From the load side's perspective, the required total power is now... Depend on Together with energy storage, the current on the grid side rapidly approaches zero.

[0099] It's worth noting that traditional automatic transfer switching (ATS) in existing technologies only occurs after the grid has "died," while this invention utilizes energy storage to proactively "take over" the load during the moment when the grid is "dying" but not completely disconnected. This process is achieved through a specially designed hybrid inverter that integrates a high-speed DSP controller and an advanced voltage source inverter (VSI) topology. It enables seamless energy flow between the photovoltaic DC, energy storage DC, and the load's AC side under low-voltage conditions. The energy storage battery here is not merely a backup power source, but a dynamic and active power buffer that fills all power gaps during the switch from grid power to off-grid power, thus fundamentally eliminating switching interruptions.

[0100] Furthermore, it can be further disclosed that the hybrid inverter module employs a dual closed-loop PID control strategy, including current-loop PID control and voltage-loop PID control, to achieve high-precision and rapid tracking of the energy storage current, wherein:

[0101] (1) The inner current loop PID controller is based on the reference current of the energy storage system. With actual energy storage current The error is used to control the voltage of the output inverter bridge arm. The mathematical expression for the voltage control output of the PID (proportional-integral) controller is as follows:

[0102]

[0103] in, and These are the proportional and integral gain coefficients of the inner current loop, respectively, used to represent the PID controller transfer function operation to express the controller's sensitivity to current errors, i.e., the voltage regulation corresponding to a unit current error. This voltage control signal... Used to generate PWM to drive the inverter bridge arm;

[0104] (2) The voltage outer loop PID controller is based on the effective value of the target voltage on the load side. Compared with the actual load-side voltage RMS value The error is used to output the reference current signal of the energy storage system. The mathematical expression for the voltage control output of the PID (proportional-integral) controller is as follows:

[0105]

[0106] in, and These are the proportional and integral gain coefficients of the outer voltage loop, respectively, used to represent the operation of the PID controller's transfer function, expressing the controller's sensitivity to voltage errors, i.e., the current regulation corresponding to a unit voltage error.

[0107] Furthermore, taking the formula of the current inner-loop PID controller as an example, the principle is explained. Here, the controller has a conversion function: The essence of the PID controller is a transfer function, and its function is to map the input signal (current error, unit: A) into the output control signal (voltage command, unit: V).

[0108] In this formula, the physical unit of the coefficient is the proportional gain coefficient. It is not a dimensionless constant; its physical unit is V / A (volts per ampere). Physically, it is equivalent to "virtual impedance," representing the controller's sensitivity to current errors, i.e., the voltage regulation corresponding to a unit current error. Similarly, the integral gain coefficient... The physical unit is V / (A·s).

[0109] Therefore, through coefficients and Dimensional conversion: the calculation result on the right side of the formula is in physical units the same as the voltage control signal on the left side. Keeping the values ​​consistent (both in volts V), this formula accurately expresses the physical mechanism of controlling the output current by adjusting the inverter port voltage.

[0110] The technical principle of voltage loop PID control output is the same.

[0111] Furthermore, the inner current loop controller here is used to generate a voltage control signal based on the current error, in order to achieve rapid current tracking. This is the voltage control signal (output) for the inverter bridge arm, used to directly generate a PWM (Pulse Width Modulation) waveform, thereby driving the inverter's power switching transistors. The reference current (target value) for the energy storage system is calculated from the outer voltage loop and represents the ideal current value required by the system at the current moment. The actual detected energy storage current (feedback value) is the actual current data collected in real time by sensors. This represents the current error signal, i.e., the difference between the target current and the actual current. This represents the proportional gain coefficient of the inner current loop, which determines the controller's response to the current error. A higher gain results in a faster response. This represents the integral gain coefficient of the inner current loop, used to eliminate the steady-state error of the system. It adjusts the output by accumulating past errors to ensure that the actual current can eventually track the reference current without error.

[0112] Furthermore, the outer voltage loop controller here is also used to calculate the current command required by the system based on the deviation of the load voltage.

[0113] at this time This serves as the reference current (output) for the energy storage system, acting as the target input value for the inner current loop, indicating how much current the system needs to output or absorb to maintain voltage stability. This is the target effective value (set value) of the voltage on the load side, which is usually the rated voltage of the system (e.g., 220V or 380V). This is the actual detected effective value of the load-side voltage (feedback value). This is a voltage error signal. This is the proportional gain coefficient of the outer voltage loop, used for rapid adjustment of voltage fluctuations. This is the integral gain coefficient of the outer voltage loop, used to eliminate steady-state voltage deviation and ensure that the output voltage remains stable at the set value over a long period of time.

[0114] Furthermore, the entire system therefore adopts a cascade control (dual closed-loop) structure:

[0115] Outer loop (voltage loop): Responsible for maintaining stable load voltage. When the voltage deviates from the target value, the outer loop PID controller calculates the amount of current that needs to be adjusted. ;

[0116] Inner loop (current loop): Responsible for quickly executing current commands. It receives the current reference value from the outer loop and adjusts the inverter output voltage accordingly. Forced actual current Quickly and accurately follow the reference value;

[0117] This structure ensures voltage stability while utilizing the high bandwidth of the current loop to quickly suppress disturbances.

[0118] Step 4: Safe switching under zero current / zero voltage conditions

[0119] Since the power pre-compensation in the previous step has reduced the current flowing through the ATS mains side contacts to near zero, the control system then sends a disconnect command to the ATS. Performing a mechanical disconnection under near-zero current conditions significantly reduces arcing, protects the contacts, extends the lifespan of the ATS equipment, and improves switching safety.

[0120] Step 5: Adaptive Impedance Matching in Off-Grid Operation Mode

[0121] After the switch is completed, the system enters the off-grid mode where photovoltaic and energy storage jointly supply power. Then, the adaptive impedance matching algorithm is activated. The adaptive impedance matching algorithm can predict the maximum output power of photovoltaic in the next moment (e.g., seconds) based on the real-time monitored light intensity, and dynamically adjust the equivalent output impedance of the hybrid inverter and the discharge strategy of the energy storage system in combination with load changes.

[0122] Specifically, it includes:

[0123] ST1. Based on Light intensity at any time and solar panel temperature The mathematical formula for constructing a prediction model for the maximum power point of photovoltaic power at this time is as follows:

[0124]

[0125] in, for The maximum output power of photovoltaic power is predicted at any time. for Peak photovoltaic power under standard test conditions at any given time and They are respectively Real-time light intensity and standard light intensity (1000 W / m²) 2 ), for Temperature coefficient of power at any time and These are the real-time solar panel temperature and the standard test temperature (25°C), respectively.

[0126] ST2. Based on the photovoltaic maximum power point prediction model, define The system efficiency that needs to be maximized at all times for:

[0127]

[0128] in, The system's instantaneous total efficiency. This represents the actual discharge power of the energy storage system. and These are the hybrid inverter's real-time monitored load power and photovoltaic output power, respectively.

[0129] ST3. Calculate the impedance matching adjustment factor for dynamically adjusting the depth of energy storage discharge. The relevant formula is:

[0130]

[0131] in, The value range of is [0, 1]. A value close to 1 indicates that the load should be prioritized. A value close to 0 indicates that photovoltaic power is being prioritized. To determine the photovoltaic maximum power point based on real-time light intensity and panel temperature. The time-based prediction model is used to represent the calculated maximum output power of the photovoltaic array;

[0132] ST4. Based on adjustment factors The optimal value is found through iterative updates using the gradient ascent method. To maximize system efficiency The calculation formula is as follows:

[0133]

[0134] in, This is the impedance matching adjustment factor for the next control cycle. This is the impedance matching adjustment factor before the update. For learning rate or iteration step size, Indicates system efficiency The gradient of the adjustment factor.

[0135] It's worth noting that the adaptive impedance matching algorithm here aims to maximize system efficiency. It achieves optimal matching between the equivalent output impedance of the photovoltaic + energy storage power system and the load impedance by adjusting the energy storage discharge current and the inverter's PWM (Pulse Width Modulation) control strategy in real time. In practice, when sunlight is abundant, the algorithm prioritizes increasing the output weight of the photovoltaic system, reducing energy storage discharge, and even charging the energy storage when the load is low. When sunlight weakens (e.g., due to clouds), the algorithm instantly increases the depth of energy storage discharge to ensure load voltage stability. This refined dynamic adjustment avoids the blind discharge of the energy storage system or the waste of photovoltaic power found in traditional solutions, resulting in a 20% efficiency improvement.

[0136] Step 6: Synchronous grid connection after the main power grid is restored

[0137] Once the monitoring system detects that the main grid has returned to normal and has been operating stably for a period of time, the control system will initiate the grid synchronization procedure. At this time, the hybrid inverter uses phase-locked loop (PLL) technology to precisely synchronize the frequency, amplitude, and phase of its output voltage to be completely consistent with the main grid. Then, at the synchronization point, it controls the ATS to close, achieving a "disturbance-free" load shedding. Afterward, the system returns to grid-connected operation.

[0138] The hybrid inverter employs phase-locked loop (PLL) technology to obtain the phase error through dq transformation, thereby synchronizing the frequency, amplitude, and phase of the output voltage to be completely consistent with the main grid. The transformation formula is as follows:

[0139]

[0140] in, The phase difference between the inverter output voltage and the grid voltage. and These are the components of the grid voltage in the dq synchronous rotating coordinate system. This refers to the output phase of the phase-locked loop inside the inverter.

[0141] On the other hand, the present invention also discloses a low-voltage standby automatic transfer control device compatible with photovoltaic and energy storage, applied to a set of main and standby power switching systems, and connected to a set of energy storage devices and the automatic transfer switch (ATS) of the system for control, used to execute the low-voltage standby automatic transfer control method compatible with photovoltaic and energy storage described in the above embodiments, including:

[0142] The monitoring module is used to continuously collect electrical parameters of designated nodes of the system at high frequency, and is set with a specified safety threshold. When the main grid voltage amplitude and frequency in the collected parameters exceed the specified safety threshold, a "dynamic buffer bridge" function activation command is issued.

[0143] The hybrid inverter module, upon receiving a function activation command, utilizes a built-in high-speed DSP controller and voltage source inverter topology to achieve seamless energy flow between the photovoltaic DC, energy storage DC, and the load AC side, ensuring that the current flowing through the ATS mains side contacts is essentially zero, and then sends a switching processing signal.

[0144] The switching processing module is used to control the automatic transfer switch (ATS) to mechanically disconnect after receiving the switching processing signal;

[0145] After the automatic transfer switch (ATS) completes its switching, it uses an adaptive impedance matching algorithm to control the dynamic adjustment of energy storage charging and discharging.

[0146] Based on the methods and apparatus proposed in the above embodiments, the following testing methods are further used for effect comparison and verification, specifically including:

[0147] The simulation includes a low-voltage power distribution system in a small commercial building equipped with the device of the present invention to perform the method of the present invention. The main power supply is 220V / 50Hz mains power, and it is equipped with a distributed power supply (consisting of a 50kWp photovoltaic array and a 100kWh / 50kW energy storage system). The critical load has a total power of 40kW and includes sensitive loads such as servers, UPS, lighting and office equipment.

[0148] The comparison is made with a low-voltage power distribution system in a small commercial building that uses the same capacity of photovoltaic and energy storage, but is equipped with a traditional mechanical ATS switching control scheme.

[0149] The switching test was conducted under the simulated condition of a sudden mains power failure (voltage dropping to 70% of normal value) at 14:00 in the afternoon (good lighting conditions but intermittent cloud cover). The test process and results are as follows:

[0150] (I) Testing process of traditional ATS solution

[0151] (a) A mains power failure occurs, and the controller detects an abnormal voltage;

[0152] (b) After a confirmation delay of approximately 50ms, the ATS issues a command to disconnect the main power grid;

[0153] (c) The ATS mechanical structure operates, taking approximately 100ms, during which the load is completely de-energized;

[0154] (d) The ATS is closed to the backup power supply side, the inverter starts, and the photovoltaic and energy storage power is delivered to the load;

[0155] (e) At this time, a power outage of about 150ms occurred on the load side, causing the server to restart and the lighting equipment to flicker. Due to cloud cover, the photovoltaic power suddenly dropped, and the load side voltage dropped by more than 25% at the moment of switching. It took a long time for the system to recover and stabilize.

[0156] (II) Testing process of the present invention

[0157] (a) When a mains power failure occurs, the controller diagnoses the fault within 20ms;

[0158] (b) The dynamic buffer bridge is activated immediately, and the hybrid inverter responds within 5ms, controlling the energy storage system to make up the power difference between the photovoltaic system and the load. At this time, the current flowing through the ATS contacts on the grid side drops to near zero;

[0159] (c) After the energy storage system has completely “taken over” the load, the controller sends a disconnect command to the ATS;

[0160] (d) The ATS disconnects safely under zero current conditions without generating an electric arc;

[0161] (e) The system seamlessly transitions to off-grid mode, and the adaptive impedance matching algorithm is activated to optimize the energy storage discharge rate in real time based on the changes in sunlight caused by cloud drift.

[0162] (f) At this point, the load-side voltage fluctuation is less than 2% throughout the entire process, with no perceived power interruption, and the server and all equipment operate normally. The overall system energy utilization is high, and the operation is stable.

[0163] (III) The final test results are compared in the table below:

[0164]

[0165] The comparison of the above test scenarios shows that the low-voltage backup automatic transfer control method and device that is compatible with photovoltaics and energy storage proposed in this invention has overwhelming advantages over the prior art in terms of power supply continuity, power quality, system operating efficiency and equipment safety.

[0166] In another aspect, the present invention also discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method described above.

[0167] In another aspect, the present invention also discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the steps of the method described above.

[0168] In another embodiment provided in this application, a computer program product containing instructions is also provided, which, when run on a computer, causes the computer to execute any of the low-voltage backup automatic transfer control methods compatible with photovoltaics and energy storage described in the above embodiments.

[0169] It is understood that the system provided in the embodiments of the present invention corresponds to the method provided in the embodiments of the present invention, and the explanation, examples and beneficial effects of the relevant content can be referred to the corresponding parts of the above methods.

[0170] This application also provides an electronic device, including a processor, a communication interface, a memory, and a communication bus, wherein the processor, communication interface, and memory communicate with each other via the communication bus.

[0171] Memory, used to store computer programs;

[0172] The processor, when executing the program stored in the memory, implements the aforementioned low-voltage backup automatic transfer control method compatible with photovoltaics and energy storage.

[0173] The communication bus mentioned in the above-mentioned electronic devices can be a standard bus for interconnecting peripheral components or an extended industrial standard structure bus, etc. This communication bus can be divided into address bus, data bus, control bus, etc.

[0174] The communication interface is used for communication between the aforementioned electronic devices and other devices.

[0175] The memory may include random access memory or non-volatile memory, such as at least one disk storage device. Optionally, the memory may also be at least one storage device located remotely from the aforementioned processor.

[0176] The processors mentioned above can be general-purpose processors, including central processing units, network processors, etc.; they can also be digital signal processors, application-specific integrated circuits, field-programmable gate arrays or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0177] It should also be noted that electronic devices include terminal devices, which can also be called terminals, user equipment, mobile stations, mobile terminals, etc. Terminal devices can be mobile phones, smart TVs, wearable devices, tablets, computers with wireless transceiver capabilities, virtual reality terminal devices, augmented reality terminal devices, wireless terminals in industrial control, wireless terminals in autonomous driving, wireless terminals in remote surgery, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, wireless terminals in smart homes, and so on. The embodiments of this application do not limit the specific technologies or device forms used in the terminal devices.

[0178] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired or wireless means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium, an optical medium, or a semiconductor medium, etc.

[0179] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0180] Furthermore, it should be noted that if any directional indication (such as up, down, left, right, front, back, etc.) is involved in the embodiments of the present invention, the directional indication is only used to explain the relative positional relationship and movement of each component in a specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0181] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, in the embodiments of this invention, "multiple" refers to two or more. Moreover, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

Claims

1. A low-voltage standby automatic transfer control method compatible with photovoltaic and energy storage, applied to a set of main and standby power supply switching systems, characterized in that, include: In the event of a mains power failure, an integrated set of hybrid inverter modules is used to dynamically buffer the load through energy storage batteries before the ATS physically disconnects the main power supply, compensating for the difference between the power required by the load and the actual output power of the photovoltaic system at that time, so as to maintain the stability of the load-side voltage and frequency. Seamless switching from mains power to photovoltaic energy storage combined power supply mode is achieved without any noticeable power quality issues on the load side. After the switch is completed, the discharge depth and rate of the energy storage are dynamically adjusted according to the real-time light intensity and load changes through an adaptive impedance matching algorithm. The adaptive impedance matching algorithm is used to predict the maximum output power of the photovoltaic system at the next moment based on the real-time monitored irradiance, and dynamically adjusts the equivalent output impedance of the hybrid inverter and the discharge strategy of the energy storage system in conjunction with load changes. Specifically, it includes: ST1. Based on Light intensity at any time and solar panel temperature The mathematical formula for constructing a prediction model for the maximum power point of photovoltaic power at this time is as follows: in, for The maximum output power of photovoltaic power is predicted at any time. for Peak photovoltaic power under standard test conditions at any given time and They are respectively Real-time light intensity and standard light intensity at all times. for Temperature coefficient of power at any time and These are the real-time solar panel temperature and the standard test temperature, respectively. ST2. Based on the photovoltaic maximum power point prediction model, define The system efficiency that needs to be maximized at all times for: in, The system's instantaneous total efficiency. This represents the actual discharge power of the energy storage system. and These are the hybrid inverter's real-time monitored load power and photovoltaic output power, respectively. ST3. Calculate the impedance matching adjustment factor for dynamically adjusting the depth of energy storage discharge. The relevant formula is: in, The value range of is [0, 1]. A value close to 1 indicates that the load should be prioritized. A value close to 0 indicates that photovoltaic power is being prioritized. To determine the photovoltaic maximum power point based on real-time light intensity and panel temperature. The time-based prediction model is used to represent the calculated maximum output power of the photovoltaic array; ST4. Based on adjustment factors The optimal value is found through iterative updates using the gradient ascent method. To maximize system efficiency The calculation formula is as follows: in, This is the impedance matching adjustment factor for the next control cycle. This is the impedance matching adjustment factor before the update. For learning rate, Indicates system efficiency The gradient of the adjustment factor.

2. The low-voltage backup automatic transfer control method compatible with photovoltaics and energy storage as described in claim 1, characterized in that, The mains power failure is confirmed by continuously collecting electrical parameters from designated nodes of the system through the monitoring module. These electrical parameters include: the voltage, frequency, and phase of the main grid; the output voltage, current, and ambient light intensity of the photovoltaic array; the state of charge, terminal voltage, and current of the energy storage battery; and the real-time power demand on the load side. When the voltage amplitude and frequency of the main grid exceed the preset safety threshold and remain so for a specified period of time, it is determined that there is a mains power fault in the main grid. The determination formula is as follows: in, and These represent the voltage fault flag and the frequency fault flag, respectively. If the result of the judgment formula is 1, then there is a mains power fault in the mains power grid; otherwise, there is a mains power fault in the mains power grid. and These represent the preset lower and upper voltage thresholds, respectively. The rated frequency of the power grid. The maximum allowable frequency deviation threshold, The effective value of the main grid voltage. This refers to the real-time frequency of the main power grid.

3. The low-voltage backup automatic transfer control method compatible with photovoltaics and energy storage as described in claim 2, characterized in that, The specific operation process of the hybrid inverter module using energy storage batteries for dynamic buffering includes: L1. Measurement load side at Instantaneous voltage at time t and instantaneous current Calculate the real-time active power of the load. The calculation formula is as follows: in One cycle of the grid voltage; L2. The hybrid inverter monitors the real-time active power of the load. and photovoltaic output power Calculate the power gap The calculation formula is as follows: exist This is the reference output power of the energy storage system; L3. Controls the energy storage system's precise output with a microsecond-level response speed. Power of size; At this point, the reference current is calculated based on the energy storage power and the battery terminal voltage, using the following formula: in, This is the reference discharge current for the energy storage system. This represents the real-time terminal voltage of the energy storage battery.

4. The low-voltage backup automatic transfer control method compatible with photovoltaics and energy storage as described in claim 3, characterized in that, The hybrid inverter module employs a dual closed-loop PID control strategy, including current-loop PID control and voltage-loop PID control, to achieve high-precision and rapid tracking of the energy storage current. (1) The inner current loop PID controller is based on the reference current of the energy storage system. With actual energy storage current The error is used to control the voltage of the output inverter bridge arm. The mathematical expression for the voltage control output of the PID controller is as follows: in, and These are the proportional and integral gain coefficients of the inner current loop, respectively, used to represent the PID controller transfer function operation to express the controller's sensitivity to current errors, i.e., the voltage regulation corresponding to a unit current error. This voltage control signal... Used to generate PWM drive inverter bridge arms; (2) The voltage outer loop PID controller is based on the effective value of the target voltage on the load side. Compared with the actual load-side voltage RMS value The error is used to output the current reference signal of the energy storage system. The mathematical expression for the voltage control output of the PID controller is as follows: in, and These are the proportional and integral gain coefficients of the outer voltage loop, respectively, used to represent the operation of the PID controller's transfer function, expressing the controller's sensitivity to voltage errors, i.e., the current regulation corresponding to a unit voltage error.

5. The low-voltage backup automatic transfer control method compatible with photovoltaics and energy storage as described in claim 1, characterized in that, After the main grid returns to normal and operates stably for a specified time, the synchronous grid connection procedure is initiated. The frequency, amplitude and phase of the output voltage are synchronized with the main grid by using phase-locked loop technology through the hybrid inverter. Then, the ATS is closed at the synchronization point to achieve a disturbance-free back-switch of the load, and the main and backup power switching system is then restored to the grid-connected operation state.

6. The low-voltage backup automatic transfer control method compatible with photovoltaics and energy storage as described in claim 5, characterized in that, The hybrid inverter employs phase-locked loop (PLL) technology to obtain the phase error through dq transformation, thereby synchronizing the frequency, amplitude, and phase of the output voltage to be completely consistent with the main power grid. The transformation formula is as follows: in, The phase difference between the inverter output voltage and the grid voltage. and These are the components of the grid voltage in the dq synchronous rotating coordinate system. This refers to the output phase of the phase-locked loop inside the inverter.

7. A low-voltage standby automatic transfer control device compatible with photovoltaic and energy storage, applied to a set of main and standby power switching systems, and connected to a set of energy storage devices and the automatic transfer switch (ATS) of the system for control, used to execute the low-voltage standby automatic transfer control method compatible with photovoltaic and energy storage as described in any one of claims 1-6, characterized in that, include: The monitoring module is used to continuously collect electrical parameters of designated nodes of the system at high frequency, and is set with a specified safety threshold. When the main grid voltage amplitude and frequency in the collected parameters exceed the specified safety threshold, a "dynamic buffer bridge" function activation command is issued. The hybrid inverter module, upon receiving a function activation command, utilizes a built-in high-speed DSP controller and voltage source inverter topology to achieve seamless energy flow between the photovoltaic DC, energy storage DC, and the load AC side, ensuring that the current flowing through the ATS mains side contacts is essentially zero, and then sends a switching processing signal. The switching processing module is used to control the automatic transfer switch (ATS) to mechanically disconnect after receiving the switching processing signal. After the automatic transfer switch (ATS) completes its switching, the energy storage charging and discharging are dynamically adjusted through an adaptive impedance matching algorithm.

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