Method, device and electronic equipment for suppressing transformer magnetizing inrush current

Abstract

The application discloses a method, device and electronic equipment for inhibiting transformer excitation inrush current, and the method comprises the following steps: outputting a pre-charge voltage from a first port of an inverter; collecting a voltage signal of the inverter, and determining a zero-crossing point of the pre-charge voltage according to the voltage signal; determining a first closing time according to the zero-crossing point of the pre-charge voltage; determining a second closing time according to the first closing time and a target delay time; the target delay time is the time from the issuance of an attraction instruction of the inverter to the response of a relay; and issuing the attraction instruction to the relay at the second closing time, and controlling the attraction of a contact of the relay, so as to inhibit the transformer excitation inrush current. The method provided by the application can efficiently inhibit the transformer excitation inrush current, and is helpful to improve the stability of the energy storage inverter control system; meanwhile, no additional hardware circuit or device needs to be added in the energy storage inverter control system, and the cost of inhibiting the transformer excitation inrush current is reduced.

Description

Technical Field

[0001] This application relates to the field of energy storage power supply technology, specifically to a method, apparatus, and electronic device for suppressing transformer inrush current. Background Technology

[0002] The Emergency Power Supply (EPS) port of a photovoltaic energy storage inverter is used to supply power to the load when the grid is interrupted. When the EPS port is connected to a transformer for isolation or step-up / step-down equipment, a large inrush current is generated at the moment the inverter's relay closes due to the transformer core flux saturation, residual flux, and the nonlinear characteristics of the core material. This impactful closing current can reach several times the rated current, potentially causing the inverter's overcurrent protection to malfunction, leading to inverter control system startup failure, excessive stress on power devices, decreased long-term operational reliability, and even DC bus voltage fluctuations, affecting the stability of the inverter control system. Furthermore, the dispersion and temperature drift of the relay's operating time are also key factors affecting closing accuracy.

[0003] Therefore, there is an urgent need for a method to suppress transformer inrush current in order to improve the stability of the energy storage inverter control system. Summary of the Invention

[0004] A method, apparatus, and electronic device for suppressing transformer inrush current are provided, with the aim of suppressing transformer inrush current to improve the stability of the energy storage inverter control system.

[0005] In a first aspect, a method for suppressing transformer inrush current is provided, applied to an energy storage inverter control system. The energy storage inverter control system includes: an inverter, a transformer, and a load. One end of the transformer is connected to the inverter via a first port, and the other end of the transformer is connected to the load via a second port. The inverter's first port outputs a pre-charge voltage; The inverter's voltage signal is acquired, and the zero-crossing point of the pre-charge voltage is determined based on the voltage signal. The first closing time is determined based on the zero-crossing point of the pre-charge voltage; The second closing time is determined based on the first closing time and the target delay time; the target delay time is the time from when the energizing command is issued by the inverter to when it is responded to by the relay. At the second closing moment, a closing command is sent to the relay to control the relay contacts to close, thereby suppressing the transformer inrush current.

[0006] In some embodiments of this application, the precharge voltage has the same frequency as the rated voltage of the inverter, and the amplitude of the precharge voltage is lower than that of the rated voltage.

[0007] In some embodiments of this application, the method for suppressing transformer inrush current further includes: obtaining a target delay time; wherein, obtaining the target delay time includes: performing a pull-in test on the relays of multiple inverters at different ambient temperatures to obtain test results; the test results include: the target delay time corresponding to each of the different ambient temperatures.

[0008] In some embodiments of this application, the method for suppressing transformer inrush current further includes: storing target delay times corresponding to different ambient temperatures in the inverter's memory, so as to retrieve the corresponding target delay times according to the ambient temperature when determining the second closing time.

[0009] In some embodiments of this application, the method for suppressing transformer inrush current further includes: obtaining a target delay time; wherein, obtaining the target delay time includes: after detecting that the Nth inverter issues a closing command to the relay, recording the time from when the Nth inverter issues the closing command to when the relay responds to the closing command and controls the relay contacts to close, thereby obtaining the target delay time corresponding to the Nth inverter issuing the closing command to the relay, so as to retrieve the target delay time when determining the N+1th second closing time.

[0010] In some embodiments of this application, the first closing time is the time corresponding to a quarter cycle after the zero-crossing time of the precharge voltage. Determining the second closing time based on the first closing time and the target delay time includes: performing a difference calculation on the first closing time and the target delay time to obtain the second closing time.

[0011] In some embodiments of this application, the method for suppressing transformer inrush current further includes: after the relay contacts are engaged, increasing the output voltage of the first port of the inverter from the precharge voltage to the rated voltage, and outputting the output voltage of the first port to the second port via the relay to supply power to the load.

[0012] In some embodiments of this application, the method for suppressing transformer inrush current further includes: real-time monitoring of output current or DC bus voltage, so as to adjust the rate of increase from precharge voltage to rated voltage when an abnormality is detected in output current or DC bus voltage; and increasing the output voltage of the first port of the inverter from precharge voltage to rated voltage in a linear or stepwise manner.

[0013] Secondly, a device for suppressing transformer inrush current is also provided, applied to an energy storage inverter control system. The energy storage inverter control system includes: an inverter, a transformer, and a load, comprising: The output module is used to output the pre-charge voltage at the first port of the inverter; The first determining module is used to acquire the voltage signal of the inverter and determine the zero-crossing point of the pre-charge voltage based on the voltage signal; The second determining module is used to determine the first closing time based on the zero-crossing point of the precharge voltage; The third determining module is used to determine the second closing time based on the first closing time and the target delay time; the target delay time is the time from when the energizing command is issued by the inverter to when it is responded to by the relay. The control module is used to send a closing command to the relay at the second closing moment to control the relay contacts to close, thereby suppressing the transformer inrush current.

[0014] Thirdly, this application provides an electronic device, comprising: Memory, used to store computer programs; A processor for executing a computer program to implement the steps in the method for suppressing transformer inrush current as provided in the first aspect.

[0015] Through one or more embodiments of the above embodiments in this application, at least the following technical effects can be achieved: By acquiring the inverter's voltage signal and determining the zero-crossing point of the pre-charge voltage based on the voltage signal, the first closing time is determined based on the zero-crossing point of the pre-charge voltage. The second closing time is determined based on the first closing time and the target delay time. At the second closing time, a closing command is sent to the relay to control the relay contacts to close, thereby suppressing the transformer inrush current. This method can effectively suppress the transformer inrush current, which helps to improve the stability of the energy storage inverter control system. At the same time, no additional hardware circuits or devices are required, reducing the cost of suppressing the transformer inrush current. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the frame of a photovoltaic energy storage inverter provided in an exemplary embodiment of this disclosure; Figure 2 This is a flowchart illustrating a method for suppressing transformer inrush current provided by an exemplary embodiment of this disclosure. Figure 3 This is a schematic diagram of a structure for suppressing transformer inrush current provided by an exemplary embodiment of this disclosure; Figure 4This is a schematic diagram of the process for obtaining the target delay time provided by an exemplary embodiment of this disclosure; Figure 5 This is another schematic flowchart of a method for suppressing transformer inrush current provided by an exemplary embodiment of this disclosure; Figure 6 This is a schematic diagram of an embodiment of a device for suppressing transformer inrush current provided by an exemplary embodiment of this disclosure; Figure 7 This is a schematic diagram of the structure of the electronic device provided in the embodiments of this application. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] In the description of the embodiments of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0020] The use of "applies to" or "configured to" in this application implies open and inclusive language, which does not exclude the applicability to or configuration to devices performing additional tasks or steps. Additionally, the use of "based on" implies openness and inclusivity, because processes, steps, calculations, or other actions "based on" one or more of the stated conditions or values ​​may in practice be based on additional conditions or values ​​beyond those stated.

[0021] In this application, the term "exemplary" is used to mean "used as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use this application. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that this application can be made without using these specific details. In other instances, well-known structures and processes are not described in detail to avoid obscuring the description of this application with unnecessary detail. Therefore, this application is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.

[0022] In existing technologies, photovoltaic energy storage inverters are devices that realize energy conversion between solar energy systems, electrochemical energy storage systems, AC power grids, and AC loads. Figure 1 This is a schematic diagram of the framework of a photovoltaic energy storage inverter provided in an exemplary embodiment of this disclosure, such as... Figure 1 As shown, the first port (EPS port) of the photovoltaic energy storage inverter is connected to a transformer as an isolation or step-up / step-down device, and the other end of the transformer is connected to the load through the second port (load port). The EPS port of the photovoltaic energy storage inverter provides power support to the load when the grid is interrupted. When the EPS port is connected to the transformer as an isolation or step-up / step-down device, at the moment the relay closes, the transformer will generate a large-amplitude inrush current due to the core flux saturation, residual magnetism, and nonlinear characteristics of the core material. After a transient process of several cycles, it tends to stabilize. This impactful closing current can be several times the rated current, which may cause the inverter overcurrent protection to malfunction, leading to the failure of the energy storage inverter control system to start up, overstressing of power devices, and reduced long-term operational reliability. It may also cause DC bus voltage fluctuations, affecting the stability of the energy storage inverter control system.

[0023] In related technologies, phase-selective closing technology is commonly used to suppress inrush current in large transformers. Specifically, by controlling the opening and closing times of the high-voltage circuit breaker, the circuit breaker closes when the voltage phase is 90°, corresponding to zero magnetic flux, which effectively suppresses inrush current. However, phase-selective closing technology is mainly geared towards power transmission and distribution systems. For the power grid and conventional power equipment, it requires external independent circuit breakers or closing devices, resulting in high costs for suppressing transformer inrush current. Furthermore, the inverter uses AC relays inside the EPS port for closing control. In addition, the inverter itself acts as a voltage source, and the phase and frequency of the output voltage at its EPS port are generated and precisely controlled by an internal controller, which is fundamentally different from the fixed-frequency voltage source on the grid side. In other words, conventional phase-selective closing technology relies on the grid phase reference and external circuit breakers for closing control, while the EPS of a photovoltaic energy storage inverter is an independently controllable voltage source without external synchronization signals and only uses low-cost built-in relays, lacking the conditions for high-precision phase selection. Meanwhile, traditional solutions require additional hardware, are costly and have low integration, and cannot meet the design requirements of integrated inverters and high cost-effectiveness. Therefore, it is difficult to directly apply conventional phase selection and closing technology to photovoltaic energy storage systems.

[0024] It should be noted that, in some optional embodiments, the energy conversion circuit on the battery side is not limited to the two-stage structure of the resonant converter circuit and the buck-boost circuit described above. A single-stage isolated DC-DC converter circuit can also be used to achieve energy transfer and voltage regulation between the battery and the DC bus. Those skilled in the art can choose different circuit topologies according to specific application requirements without affecting the implementation of the control method for suppressing transformer inrush current described in this application.

[0025] To at least partially address one or more of the aforementioned problems and other potential issues, this application proposes a scheme for suppressing transformer inrush current. The scheme includes: outputting a pre-charge voltage at the first port of the inverter; acquiring the inverter's voltage signal and determining the zero-crossing point of the pre-charge voltage based on the voltage signal; determining a first closing time based on the zero-crossing point of the pre-charge voltage; determining a second closing time based on the first closing time and a target delay time; the target delay time being the time from when the closing command is issued by the inverter to when it is responded to by a relay; and issuing a closing command to the relay at the second closing time to control the relay contacts to close, thereby suppressing transformer inrush current. This effectively suppresses transformer inrush current, contributing to improved stability of the energy storage inverter control system; simultaneously, it eliminates the need for additional hardware circuitry or components, reducing the cost of suppressing transformer inrush current.

[0026] Figure 2 This is a schematic flowchart of a method for suppressing transformer inrush current provided by an exemplary embodiment of this disclosure, such as... Figure 2 As shown, the process may include: Step S201: The inverter outputs a pre-charge voltage at its first port.

[0027] The energy storage inverter control system includes an inverter, a transformer, and a load. One end of the transformer is connected to the inverter via a first port, and the other end is connected to the load via a second port. An inverter is a power electronic device that converts alternating current (AC) to direct current (DC) or vice versa. The inverter's first port is the emergency power supply port (EPS port), used to provide AC power to the load during grid outages.

[0028] The precharge voltage is a low-amplitude AC voltage output by the inverter before it is officially switched on. It is synchronized with the inverter's rated voltage and frequency, and its frequency is the same as the inverter's rated output voltage frequency, for example, 50Hz. The amplitude of the precharge voltage is lower than the rated voltage, for example, the amplitude of the precharge voltage is 10% to 30% of the rated voltage, so as to provide a stable reference signal for subsequent voltage zero-crossing detection, while avoiding direct high-voltage impact.

[0029] The above-mentioned pre-charge voltage output process constitutes a voltage pre-synchronization process, which is used to establish a stable phase reference before the relay closes.

[0030] Step S202: Acquire the voltage signal of the inverter and determine the zero-crossing point of the pre-charge voltage based on the voltage signal.

[0031] Voltage signal refers to the voltage waveform signal at the output port of the inverter, which can be obtained in real time through a voltage sensor or sampling circuit.

[0032] For example, in a specific implementation, the inverter control system samples the voltage signal in real time through an analog-to-digital converter. The sampling frequency can usually be set to tens or even hundreds of times the voltage frequency to ensure the accuracy of zero-crossing detection. By performing digital filtering and zero-crossing detection algorithm processing on the sampled data, the zero-crossing moment when the pre-charge voltage waveform transitions from the negative half-cycle to the positive half-cycle or from the positive half-cycle to the negative half-cycle is identified.

[0033] Step S203: Determine the first closing time based on the zero-crossing point of the pre-charge voltage.

[0034] The first closing moment refers to the ideal moment when the relay contacts should theoretically complete their engagement. Determining the first closing moment can take into account the zero-crossing position of the pre-charge voltage and the magnetization characteristics of the transformer core. Ideally, if the relay can respond to the control command instantaneously, the first closing moment can be directly set to the zero-crossing moment of the pre-charge voltage. However, in practical applications, due to the mechanical action time and electromagnetic response delay of the relay, the first closing moment needs to be appropriately adjusted.

[0035] The first closing time can be calculated based on the zero-crossing point of the pre-charge voltage and the principle that "the magnetic flux is zero when closing the circuit at the peak of the sinusoidal AC voltage." Specifically, the first closing time can be set to the moment corresponding to a quarter-cycle after the zero-crossing point of the pre-charge voltage, that is, when the phase of the pre-charge voltage is 90° or 270°. Since the peak voltage occurs a quarter-cycle after the zero-crossing point of the sinusoidal AC voltage, setting this quarter-cycle as the first closing time is appropriate. Closing the circuit at this time ensures that the magnetic flux in the transformer core is at zero, effectively preventing magnetic flux saturation and thus suppressing inrush current.

[0036] Step S204: Determine the second closing time based on the first closing time and the target delay time; the target delay time is the time from when the closing command is issued by the inverter to when it is responded to by the relay.

[0037] The target delay time is a parameter that measures the dynamic response characteristics of a relay. It is the time interval from when the inverter issues a energizing command to when the relay contacts actually complete their closing action. This target delay time can be affected by various factors, including the electrical parameters of the relay coil, the mechanical structure of the contacts, the ambient temperature, and the degree of aging of the relay.

[0038] Step S205: At the second closing moment, a closing command is sent to the relay to control the relay contacts to close, thereby suppressing the transformer inrush current.

[0039] The activation command refers to the control command generated by the inverter control system to energize the relay coil; this activation command can be represented as a digital signal or pulse signal at a specific level. At the second closing moment, an activation command is issued to the relay. Under the action of electromagnetic force, the relay coil controls the relay contacts to close. At the instant the contacts close, the magnetic flux in the transformer core starts from zero, avoiding sudden changes in magnetic flux caused by phase mismatch between residual magnetism and the closing voltage. Moreover, the pre-charge voltage amplitude is low, and even with a slight phase deviation, the resulting excitation current is limited to a small range, preventing the inverter's overcurrent protection from being triggered. As the contacts close stably, the inverter gradually increases the output voltage to the rated value, and the transformer enters normal operation. The inrush current during the entire closing process is effectively suppressed.

[0040] Figure 3 This is a schematic diagram of a structure for suppressing transformer inrush current provided by an exemplary embodiment of this disclosure, such as... Figure 3 As shown, the photovoltaic input terminal is connected to the positive and negative terminals of the DC bus via a boost circuit. The battery terminal is connected to the DC bus via a resonant converter circuit (such as an inductor-inductor-capacitor resonant converter circuit (LLC) or other types of resonant topology) and a boost / buck circuit, realizing the conversion and regulation of photovoltaic energy and battery energy. The DC bus energy is converted into AC power by the topology inverter circuit and then connected to the emergency power relay and the grid relay, thereby switching between grid-connected power supply and emergency power supply modes. In emergency power supply mode, the electrical energy is output through the emergency power relay to the emergency power supply L and emergency power supply N terminals and connected to the transformer to supply power to the load. It should be noted that the control unit is used to output a precharge voltage drive command to the topology inverter circuit to control the output of the precharge voltage at the first port of the inverter, and to acquire the voltage signal in real time to determine the zero-crossing point of the precharge voltage based on the voltage signal; to determine the first closing time based on the zero-crossing point of the precharge voltage; and to determine the second closing time based on the first closing time and the target delay time. The target delay time is the time from when the closing command is issued by the inverter to when it is responded to by the relay. At the second closing time, a closing command is issued to the relay to control the relay contacts to close, thereby suppressing the transformer inrush current. Here, the control unit can be a Digital Signal Processor (DSP).

[0041] The energy storage system control method provided in this application provides a method that outputs a pre-charge voltage through the first port of the inverter; acquires the voltage signal of the inverter and determines the zero-crossing point of the pre-charge voltage based on the voltage signal; determines the first closing time based on the zero-crossing point of the pre-charge voltage; determines the second closing time based on the first closing time and the target delay time; and issues a closing command to the relay at the second closing time to control the relay contacts to close, thereby suppressing transformer inrush current. This method can efficiently suppress transformer inrush current, which helps to improve the stability of the energy storage inverter control system. At the same time, it does not require additional hardware circuits or devices, thus reducing the cost of suppressing transformer inrush current.

[0042] In some embodiments of this application, the precharge voltage has the same frequency as the rated voltage of the inverter, and the amplitude of the precharge voltage is lower than that of the rated voltage.

[0043] For example, in a specific implementation, the pre-charge voltage is an AC voltage output from the inverter's topology inverter circuit and is output at the first port (emergency power port); the control unit controls the topology inverter circuit by outputting drive commands to generate this pre-charge voltage. The pre-charge voltage has the same frequency as the inverter's rated voltage, but its amplitude is lower than the rated voltage.

[0044] In some embodiments of this application, the method for suppressing transformer inrush current further includes: obtaining a target delay time; wherein, obtaining the target delay time includes: performing a pull-in test on the relays of multiple inverters at different ambient temperatures to obtain test results; the test results include: the target delay time corresponding to each of the different ambient temperatures.

[0045] In some embodiments of this application, the method for suppressing transformer inrush current further includes: storing target delay times corresponding to different ambient temperatures in the inverter's memory, so as to retrieve the corresponding target delay times according to the ambient temperature when determining the second closing time.

[0046] In practical applications, during the inverter production or on-site commissioning phases, relay engagement tests are conducted on multiple inverters of the same model under different ambient temperature conditions. A high-precision time measurement device records the actual time from the issuance of the engagement command to the closure of the contacts, obtaining the test results. These results are then stored in the inverter's memory. The test includes the target delay time corresponding to different ambient temperatures. During actual operation, the energy storage inverter control system monitors the ambient temperature in real time using a temperature sensor and retrieves the corresponding target delay time from the memory based on the ambient temperature, achieving temperature-adaptive compensation for the delay time.

[0047] It should be noted that the memory can be any type of non-volatile storage medium, including but not limited to flash memory, electrically erasable programmable read-only memory, or ferroelectric memory, to ensure that the target latency data is not lost in the event of a power outage. The memory capacity and read / write speed must meet the requirements of real-time control.

[0048] Figure 4 This is a schematic diagram of the process for obtaining the target delay time provided by an exemplary embodiment of this disclosure, such as... Figure 4 As shown, the process may include: Step S401: Begin; then proceed to step S402; Step S402: Perform activation tests on the relays of multiple inverters under different ambient temperatures to obtain test results; then proceed to step S403. Step S403: Store the target delay time corresponding to different ambient temperatures in the test results into the inverter's memory; then execute step S404; Step S404: End.

[0049] In some embodiments of this application, the method for suppressing transformer inrush current further includes: obtaining a target delay time; wherein, obtaining the target delay time includes: after detecting that the Nth inverter issues a closing command to the relay, recording the time from when the Nth inverter issues the closing command to when the relay responds to the closing command and controls the relay contacts to close, thereby obtaining the target delay time corresponding to the Nth inverter issuing the closing command to the relay, so as to retrieve the target delay time when determining the N+1th second closing time.

[0050] In practical applications, during inverter operation, when a relay is detected to have engaged, the energy storage inverter control system records the time interval from issuing the engagement command to detecting the actual contact closure feedback signal, and updates the memory with this time interval as the target delay time. This allows for continuous tracking of relay performance changes over time and with aging, ensuring the real-time nature and accuracy of the target delay time.

[0051] Here, the moment the contacts close can be determined by detecting sudden changes in current or relay feedback signals.

[0052] It should be noted that the target delay time can be obtained using the aforementioned factory calibration method alone, the online self-learning method alone, or both methods simultaneously. For example, production test data can be used as the initial target delay time during the initial commissioning of the inverter. During operation, real-time monitoring data can be used for continuous correction, ensuring both the reliability of initial control and long-term accuracy optimization. Furthermore, for complex topologies with multiple relays connected in parallel or series, the target delay time of each relay can be measured separately, and the maximum value or weighted average value can be taken as the target delay time, ensuring the coordination of synchronous closure of multiple contacts.

[0053] In some embodiments of this application, the first closing time is the time corresponding to a quarter cycle after the zero-crossing time of the precharge voltage. Determining the second closing time based on the first closing time and the target delay time includes: performing a difference calculation on the first closing time and the target delay time to obtain the second closing time.

[0054] The second closing time is calculated according to the following formula: T_trigger=T_target-T_delay ; in, T_trigger Indicates the second closing time; T_target Indicates the moment of the first closing; T_delay Indicates the target delay time.

[0055] In some embodiments of this application, the method for suppressing transformer inrush current further includes: after the relay contacts are engaged, increasing the first port output voltage of the inverter from the precharge voltage to the rated voltage, and outputting the first port output voltage to the second port via the relay and the transformer to supply power to the load.

[0056] For example, in a specific implementation, after the relay contacts close, the process of gradually increasing the output voltage of the inverter's first port from the pre-charge voltage to the rated voltage can be done linearly or in a step-by-step manner. This avoids secondary current surges caused by voltage fluctuations, and the output voltage of the first port is transmitted to the second port via the closed relay contacts to provide stable rated AC power to the load.

[0057] Here, the voltage rise rate can be set according to the characteristics of the transformer and the load to avoid secondary current surges. During the voltage rise process, the energy storage inverter control system monitors the output current and DC bus voltage in real time. If abnormal fluctuations are detected, the voltage rise process is paused or slowed down to ensure that the energy storage inverter control system safely and stably enters the rated operating state.

[0058] In some embodiments of this application, the method for suppressing transformer inrush current further includes: real-time monitoring of output current or DC bus voltage, so as to adjust the rate of increase from precharge voltage to rated voltage when an abnormality is detected in output current or DC bus voltage; and increasing the output voltage of the first port of the inverter from precharge voltage to rated voltage in a linear or stepwise manner.

[0059] Figure 5 This is another schematic flowchart of a method for suppressing transformer inrush current provided by an exemplary embodiment of this disclosure, such as... Figure 5 As shown, the process may include: Step S501: Begin; then proceed to step S502; Step S502: The inverter is powered on and performs a self-test; then proceed to step S503. Step S503: Determine whether the inverter has entered the emergency power supply mode based on the sampling information of each port; if yes, proceed to step S504; if no, proceed to step S502. Step S504: The inverter outputs a pre-charge voltage at its first port; then proceed to step S505. Step S505: Acquire the inverter's voltage signal and determine the zero-crossing point of the pre-charge voltage based on the voltage signal; then execute step S506. Step S506: Determine the first closing time based on the zero-crossing point of the pre-charge voltage; then execute S507; Step S507: Determine the second closing time based on the first closing time and the target delay time; then proceed to step S508; Step S508: At the second closing moment, a closing command is sent to the relay to control the relay contacts to close; then step S509 is executed. Step S509: Record the time from when the inverter issues the activation command to when the relay responds to the activation command and controls the relay contacts to activate, and obtain the target delay time; it should be noted that this step is used to dynamically update the target delay time, and based on the updated target delay time, the triggering time of subsequent relay activation commands is corrected in real time to form a closed-loop adaptive control mechanism; then execute step S510. Step S510: Increase the output voltage of the first port of the inverter from the pre-charge voltage to the rated voltage, and output the first port output voltage to the second port via a relay to supply power to the load; then execute step S511; Step S511: End.

[0060] It should be noted that emergency power supply mode refers to the inverter operating independently from the power grid to provide emergency power to local loads. In emergency power supply mode, the inverter needs to autonomously establish its output voltage and frequency, and control relays to deliver power to the transformer and load side. Triggering conditions for emergency power supply mode typically include abnormal grid voltage, grid frequency exceeding limits, received external switching commands, or user-manual switching commands. When the inverter detects these triggering conditions, it automatically switches to emergency power supply mode, initiates the pre-charge voltage output process, and prepares for subsequent relay closing control.

[0061] Figure 6 This is a schematic diagram of an embodiment of a device for suppressing transformer inrush current provided in this exemplary embodiment of the present disclosure, as shown below. Figure 6 As shown, this is applied to an energy storage inverter control system, which includes an inverter, a transformer, and a load. The device for suppressing transformer inrush current includes: Output module 601 is used to output a pre-charge voltage at the first port of the inverter; The first determining module 602 is used to acquire the voltage signal of the inverter and determine the zero-crossing point of the pre-charge voltage based on the voltage signal; The second determining module 603 is used to determine the first closing time based on the zero crossing point of the precharge voltage; The third determining module 604 is used to determine the second closing time based on the first closing time and the target delay time; the target delay time is the time from when the energizing command is issued by the inverter to when it is responded to by the relay. The control module 605 is used to send a closing command to the relay at the second closing moment to control the relay contacts to close, so as to suppress the transformer inrush current.

[0062] Based on any of the above embodiments, another embodiment of this application also provides an electronic device, such as... Figure 7 As shown, the electronic device may include a processor 710, a communication interface 720, a memory 730, and a communication bus 740, wherein the processor 710, the communication interface 720, and the memory 730 communicate with each other through the communication bus 740. The processor 710 can call logic instructions in the memory 730 to execute the control method of the energy storage system described above.

[0063] Furthermore, the logical instructions in the aforementioned memory 730 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0064] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0065] The foregoing has provided a detailed description of a method, apparatus, and electronic device for suppressing transformer inrush current according to embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this application. At the same time, those skilled in the art will recognize that there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for suppressing transformer inrush current, applied to an energy storage inverter control system, the energy storage inverter control system comprising: An inverter, a transformer, and a load are provided, wherein one end of the transformer is connected to the inverter via a first port, and the other end of the transformer is connected to the load via a second port. The method comprises: The inverter outputs a pre-charge voltage at its first port. The voltage signal of the inverter is acquired, and the zero-crossing point of the pre-charge voltage is determined based on the voltage signal; The first closing time is determined based on the zero-crossing point of the pre-charge voltage; The second closing time is determined based on the first closing time and the target delay time; the target delay time is the time from when the energizing command is issued by the inverter to when it is responded to by the relay. At the second closing moment, the closing command is sent to the relay to control the contacts of the relay to close, thereby suppressing the inrush current of the transformer.

2. The method according to claim 1, characterized in that, The pre-charge voltage has the same frequency as the rated voltage of the inverter, and the amplitude of the pre-charge voltage is lower than that of the rated voltage.

3. The method according to claim 1, characterized in that, Also includes: Obtain the target delay time; The step of obtaining the target delay time includes: The relays of multiple inverters were tested for engagement under different ambient temperatures to obtain test results; the test results included the target delay time corresponding to each ambient temperature.

4. The method according to claim 3, characterized in that, Also includes: The target delay time corresponding to different ambient temperatures is stored in the inverter's memory so that the corresponding target delay time can be retrieved according to the ambient temperature when the second closing time is determined.

5. The method according to claim 1, characterized in that, Also includes: Obtain the target delay time; The step of obtaining the target delay time includes: When the inverter sends the closing command to the relay for the Nth time, the time from when the inverter sends the closing command to when the relay responds to the closing command and controls the relay contacts to close is recorded, and the target delay time corresponding to the Nth time the inverter sends the closing command to the relay is obtained, so as to retrieve the target delay time when determining the N+1th second closing time.

6. The method according to claim 1, characterized in that, The first closing time is the time corresponding to a quarter cycle after the zero-crossing time of the precharge voltage. The step of determining the second closing time based on the first closing time and the target delay time includes: The second closing time is obtained by performing a difference calculation between the first closing time and the target delay time.

7. The method according to claim 2, characterized in that, Also includes: After the relay contacts are engaged, the output voltage of the first port of the inverter is increased from the pre-charge voltage to the rated voltage. The output voltage of the first port is then output to the second port via the relay to supply power to the load.

8. The method according to claim 7, characterized in that, Also includes: The output current or DC bus voltage is monitored in real time, and when an abnormality is detected in the output current or DC bus voltage, the rate at which the voltage is increased from the precharge voltage to the rated voltage is adjusted; the rate at which the output voltage of the first port of the inverter is increased from the precharge voltage to the rated voltage is either linear or stepwise.

9. A device for suppressing transformer inrush current, applied in an energy storage inverter control system, the energy storage inverter control system comprising: Inverter, transformer, and load, characterized in that the device comprises: The output module is used to output a pre-charge voltage at the first port of the inverter; The first determining module is used to acquire the voltage signal of the inverter and determine the zero-crossing point of the pre-charge voltage based on the voltage signal; The second determining module is used to determine the first closing time based on the zero-crossing point of the pre-charge voltage; The third determining module is used to determine the second closing time based on the first closing time and the target delay time; the target delay time is the time from when the energizing command is issued by the inverter to when it is responded to by the relay. The control module is used to send the closing command to the relay at the second closing moment to control the contacts of the relay to close, so as to suppress the inrush current of the transformer.

10. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the steps of the method for suppressing transformer inrush current as described in any one of claims 1-8.

Images