CN-121984058-A - Load self-adaptive starting control method of off-grid energy storage system and off-grid energy storage system

CN121984058ACN 121984058 ACN121984058 ACN 121984058ACN-121984058-A

Abstract

The application provides a load self-adaptive starting control method of an off-grid energy storage system and the off-grid energy storage system. The method comprises the steps of controlling an inverter to operate at rated voltage amplitude and rated voltage frequency in an off-grid operation mode, sampling output current of the inverter in real time, outputting a current signal, generating an overcurrent signal when the peak value of the current signal reaches a preset value, starting timing a first preset duration and detecting the overcurrent signal, accumulating the times of detecting the overcurrent signal in the first preset duration, judging whether the accumulated value reaches the preset times, if so, reducing the voltage amplitude and the voltage frequency output by the inverter, and if not, re-timing the first preset duration when the first preset duration is finished. The method of the application does not need to increase the overload capacity of the inverter, is suitable for the stable start of various loads, ensures the stable operation of the inverter, omits a frequency converter or a soft starter, reduces the cost and the price of the system, reduces external elements, has simple wiring and is convenient for installation and maintenance.

Inventors

YIN CONG
HUO YONGPENG
YANG HUIMING
SUN PENG

Assignees

麦田能源股份有限公司

Dates

Publication Date: 20260505
Application Date: 20260408

Claims (14)

1. The load self-adaptive starting control method of the off-grid energy storage system is characterized in that the energy storage system comprises an inverter and a control device, the inverter is connected with the load and the control device, and the method comprises the following steps: S1, when the inverter enters an off-grid operation mode, controlling the inverter to operate at a rated voltage amplitude and a rated voltage frequency, so that the voltage amplitude output by the inverter is the rated voltage amplitude and the voltage frequency is the rated voltage frequency; s2, sampling the output current of the inverter in real time, outputting a current signal, and generating an overcurrent signal when the peak value of the current signal reaches a preset value; s3, starting to time a first preset duration and detecting the overcurrent signal; S4, accumulating the times of detecting the overcurrent signals within the first preset time length to obtain an accumulated value; S5, judging whether the accumulated value reaches the preset times, if so, executing a step S6, and if not, returning to the step S3 when the first preset duration is over; S6, controlling the inverter, and reducing the voltage amplitude and the voltage frequency output by the inverter; And S7, judging whether the reduced voltage amplitude reaches a minimum voltage value or not, and whether the reduced voltage frequency reaches a minimum frequency value or not, if so, controlling the inverter to operate at the minimum voltage value and the minimum frequency value, and entering a protection state, and if not, returning to the step S3.
2. The method of claim 1, wherein controlling the inverter in step S6 to reduce the voltage amplitude and the voltage frequency output by the inverter includes controlling the inverter to reduce the voltage amplitude output by the inverter by a first voltage step and to reduce the voltage frequency by a first frequency step.
3. The load adaptive start-up control method of an off-grid energy storage system according to claim 1, further comprising initializing a step-down flag bit before step S3, and setting the step-down flag bit to 0; starting to time a first preset time length in the step S3, wherein the step comprises the step of timing the first preset time length through a timing counter; And in the step S4, the times of detecting the overcurrent signal are accumulated within the first preset time length to obtain the accumulated value, and the times of detecting the overcurrent signal are accumulated within the first preset time length and when the step-down flag bit is 0 to obtain the accumulated value.
4. The method for controlling load adaptive start of an off-grid energy storage system according to claim 3, wherein the step S5 returns to the step S3 when the first preset time period is over, and the step S3 includes clearing both the timer counter and the accumulated value when the first preset time period is over.
5. The method for controlling load self-adaptive start of an off-grid energy storage system according to claim 3, wherein if yes in step S5, step S6 is executed, including if yes, step S6 is executed with the step-down flag position being 1, and then both the accumulated value and the timer counter are cleared, or if yes, step S6 is executed with the step-down flag position being 1, and both the accumulated value and the timer counter are cleared; If not, the step S7 is returned to the step S3, and if not, the step-down mark position is set to 0, and the step S3 is returned.
6. The method of claim 1, wherein the step S6 of controlling the inverter to decrease the voltage amplitude and the voltage frequency output by the inverter includes starting to time a second preset time period, and controlling the inverter to decrease the voltage amplitude and the voltage frequency output by the inverter when the second preset time period ends.
7. The method of claim 6, wherein starting to time a second preset time period comprises timing the second preset time period by a delay counter; if not, the step S7 returns to the step S3, and if not, the delay counter is cleared, and then the step S3 is returned.
8. The method of claim 1, wherein the minimum frequency value is the nominal voltage frequency minus a preset frequency offset.
9. The load adaptive start-up control method of an off-grid energy storage system of claim 1, further comprising the steps of: s8, when the overcurrent signal is not detected, starting to count a third preset time period, and judging whether the overcurrent signal is detected or not within the third preset time period; And S9, judging whether the voltage amplitude output by the inverter reaches the rated voltage amplitude and whether the voltage frequency reaches the rated voltage frequency when the overcurrent signal is still not detected at the end of the third preset time period, if so, controlling the inverter to operate at the rated voltage amplitude and the rated voltage frequency, otherwise, controlling the inverter, raising the voltage amplitude and the voltage frequency of the inverter, and returning to the step S3.
10. The method of claim 9, wherein controlling the inverter to increase the voltage amplitude and the voltage frequency of the inverter in step S9 includes controlling the inverter to increase the voltage amplitude output by the inverter by a second voltage step and increasing the voltage frequency by a second frequency step.
11. The method for controlling load adaptive start-up of an off-grid energy storage system according to claim 9, wherein starting timing in step S8 is performed for a third preset duration, including timing the third preset duration by a persistence counter; The load self-adaptive starting control method of the off-grid energy storage system further comprises the steps of resetting the continuous counter when the overcurrent signal is detected, and returning to the step S3.
12. The load adaptive start-up control method of an off-grid energy storage system according to claim 11, wherein controlling the inverter in step S9 increases the voltage amplitude and the voltage frequency of the inverter and returns to step S3, including controlling the inverter, increasing the voltage amplitude and the voltage frequency of the inverter and clearing the persistence counter, and returning to step S3.
13. The method for controlling load self-adaptive start-up of an off-grid energy storage system according to claim 1, wherein in step S2, an output current of the inverter is sampled in real time and a current signal is output, and when a peak value of the current signal reaches a preset value, an overcurrent signal is generated, specifically comprising the following steps: S21, sampling the output current of the inverter in real time and outputting a current signal representing the magnitude of the output current; s22, comparing the current signal with the preset value, and generating the overcurrent signal when the peak value of the current signal reaches the preset value.
14. An off-grid energy storage system, comprising: an inverter connected to a load; the control device is connected with the inverter and is used for executing the load self-adaptive starting control method of the off-grid energy storage system according to any one of claims 1 to 13.

Description

Load self-adaptive starting control method of off-grid energy storage system and off-grid energy storage system Technical Field The invention relates to the field of energy storage systems, in particular to a load self-adaptive starting control method of an off-grid energy storage system and the off-grid energy storage system. Background The energy storage inverter is used as a core device of the energy storage system and has two modes of grid connection and off-grid. In grid-tie mode, the energy storage inverter delivers energy to the grid. In off-grid mode, the energy storage inverter needs to independently power the load and maintain a stable voltage and frequency output. Typically, the energy storage inverter design has a short-time overload capability of 1.2-1.5 times and duration of 3 s-30 s to meet the switching and short-time impact requirements of a general load. However, in practical applications, the off-grid energy storage system usually needs to drive a motor load, such as a water pump, a fan, or a compressor. The load has two outstanding characteristics when being directly started, namely, the starting current is extremely large and can reach 5-7 times of rated current, and a large amount of inductive reactive power is required to be absorbed in the starting process, so that the output voltage is easy to drop suddenly. When the power of the motor load reaches a certain value, the short-time overload capacity of the energy storage inverter is limited, so that the motor load cannot be started, the motor load can not be always in a locked-rotor or low-speed running state, and finally the motor load is started to fail due to the fact that the short-time overload capacity is insufficient to trigger overcurrent or overload protection, and the normal work of the motor load is influenced, and the motor load or the energy storage inverter can be damaged. In order to solve the problem, a soft start device such as a frequency converter device is usually added between the output end of the energy storage inverter and the motor load in the conventional scheme. When the motor type load is started, the frequency converter device slowly climbs at extremely low voltage and frequency according to a preset starting curve, starting current is limited, and therefore the large starting current is prevented from triggering the protection of the energy storage inverter until rated operation. However, the traditional scheme needs to purchase and install the frequency converter device additionally, so that the system cost and the occupied area are increased, the operation and maintenance complexity is improved, and the economical efficiency and the applicability are poor. However, this conventional scheme is applicable to a motor type load, but is not applicable to a resistance type load or a general household load. When the frequency converter device is connected with a resistor load or a common household load, the frequency converter device slowly climbs at extremely low voltage and frequency according to a preset starting curve, and when the voltage and frequency provided by the frequency converter device do not reach a certain value, the resistor load or the common household load cannot be started normally. Disclosure of Invention In view of the above-mentioned drawbacks of the prior art, the present invention aims to provide a load adaptive start control method of an off-grid energy storage system and an off-grid energy storage system, which can realize uninterrupted power supply when a resistive load or a common household load is smaller than the rated power of the energy storage system, and realize stable start of the motor load when the motor load is larger than the rated power of the energy storage system, without the assistance of a frequency converter, and have quick installation and high economical efficiency. The application provides a load self-adaptive starting control method of an off-grid energy storage system, which comprises an inverter and a control device, wherein the inverter is connected with the load and the control device, and the method comprises the following steps of: S1, when the inverter enters an off-grid operation mode, controlling the inverter to operate at a rated voltage amplitude and a rated voltage frequency, so that the voltage amplitude output by the inverter is the rated voltage amplitude and the voltage frequency is the rated voltage frequency; s2, sampling the output current of the inverter in real time, outputting a current signal, and generating an overcurrent signal when the peak value of the current signal reaches a preset value; s3, starting to time a first preset duration and detecting the overcurrent signal; S4, accumulating the times of detecting the overcurrent signals within the first preset time length to obtain an accumulated value; S5, judging whether the accumulated value reaches the preset times, if so, executing a step S6, and if not, returning to the step S3 wh