Bus capacitor soft start method and system for energy storage inverters

Abstract

The application discloses a bus capacitor soft starting method and system for an energy storage inverter, and comprises the following steps: collecting the first output voltage and the first frequency of a step-by-step power supply of a distributed energy storage microgrid system where the energy storage inverter is located, and obtaining a soft starting rule of a bus capacitor of the energy storage inverter, wherein the step-by-step power supply is used to represent one or more combinations of wind power, water power and photovoltaic power generation; collecting the first input voltage of a load of the distributed energy storage microgrid system after power conversion, and controlling the bus capacitor to charge according to the soft starting rule, so as to control the second output voltage of the energy storage inverter to be the same in amplitude and phase as the first input voltage, and complete phase locking; and the bus capacitor soft starting is designed, so that the safe and stable operation of the energy storage inverter in the distributed energy storage microgrid system is ensured, and the safety of the application of the energy storage inverter is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of capacitor soft start control, and particularly relates to a bus capacitor soft start method and system for an energy storage inverter. BACKGROUND

[0002] Distributed energy storage technology has been regarded as an important part of the six links of "generation-distribution-transmission-distribution-use-storage" in the process of power grid operation. After introducing the energy storage link in the system, the demand side management can be effectively carried out, the day-night peak-valley difference can be eliminated, and the load can be smoothed. Not only can the power equipment be more effectively utilized and the power supply cost be reduced, but also the application of renewable energy can be promoted, which can be used as a means to improve system operation stability, adjust frequency and compensate load fluctuation.

[0003] A distributed energy storage microgrid system capable of self-control, protection and management is usually composed of distributed power sources (light energy, wind energy, etc.), energy storage units, energy conversion devices, related loads, monitoring and protection devices. The microgrid system can operate in parallel with the external power grid or in isolation. Due to the influence of natural conditions, the output power of light energy, wind energy and the like has intermittency and randomness, and with the increasing number of such microgrid systems connected to the system and the power grid, certain negative effects are brought to the system and the power grid. How to realize seamless switching between grid-connected and off-grid modes and minimize the disturbance to power equipment and the power grid during microgrid operation mode switching is a key technology for improving the performance of distributed energy storage microgrid systems.

[0004] The energy storage inverter is an energy conversion device of the energy storage system, which can effectively realize energy management of the energy storage microgrid system. In energy management, in order to prevent excessive current from causing impact on the circuit, reducing the performance, life of the device and even damaging the device, soft start design is required for the bus of the energy storage inverter. Therefore, there is an urgent need for a bus capacitor soft start method and system for an energy storage inverter to solve the problems existing in the operation of the energy storage inverter. SUMMARY

[0005] In order to solve the problems existing in the operation of the energy storage inverter, the purpose of the present application is to provide a bus capacitor soft start method and system for an energy storage inverter, which can avoid damage to the energy storage inverter caused by excessive current.

[0006] In order to achieve the above technical purpose, the present application provides a bus capacitor soft start method for an energy storage inverter, comprising the following steps:

[0007] The first output voltage and the first frequency of the step-by-step power source of the distributed energy storage microgrid system in which the energy storage inverter is located are collected, and the soft start rule of the bus capacitor of the energy storage inverter is obtained, wherein the step-by-step power source represents one or more combinations of wind power, hydroelectric power and photovoltaic power generation;

[0008] The first input voltage of the load of the distributed energy storage micro-grid system after power conversion is collected, the bus capacitor is charged according to the soft start rule, and the second output voltage of the energy storage inverter is controlled to be the same amplitude and phase as the first input voltage, so as to complete phase locking.

[0009] Preferably, in the process of obtaining the soft start rule, when the distributed energy storage micro-grid system is connected to the external power grid, the second input voltage of the external power grid, the third output voltage and the second frequency of the third output voltage are obtained.

[0010] According to the first output voltage, the third output voltage, the first frequency and the second frequency, the soft start rule is generated.

[0011] Preferably, in the process of charging the bus capacitor according to the soft start rule, the bus capacitor is charged according to the soft start rule according to the first input voltage and the second input voltage, so as to control the second output voltage of the energy storage inverter to be the same amplitude and phase as the first input voltage and the second input voltage respectively, and complete phase locking.

[0012] Preferably, in the process of controlling the second output voltage and the first input voltage to complete phase locking, it is judged whether the step-by-step power supply is lost according to the first output voltage and the first frequency, and whether the external power grid is lost according to the third output voltage and the second frequency.

[0013] According to the loss condition, the bus capacitor is charged according to the soft start rule, and the energy storage inverter outputs the second output voltage for the load.

[0014] Preferably, in the process of controlling the energy storage inverter to output the second output voltage for the load, it is judged whether the step-by-step power supply is lost according to the first output voltage and the first frequency, and when the step-by-step power supply is not lost, the bus capacitor is charged according to the soft start rule, and the energy storage inverter outputs the second output voltage for the load through the step-by-step power supply.

[0015] When the step-by-step power supply is lost, it is judged whether the external power grid is lost according to the third output voltage and the second frequency, and if the external power grid is lost, the energy storage inverter outputs the second output voltage for the load; if the external power grid is not lost, the bus capacitor is charged according to the soft start rule, and the energy storage inverter outputs the second output voltage for the load through the external power grid.

[0016] Preferably, in the process of controlling the second output voltage and the second input voltage to complete phase locking, it is judged whether the external power grid is lost according to the third output voltage and the second frequency.

[0017] When the external power grid is lost, the energy storage inverter is controlled to be off-grid with the external power grid.

[0018] When the external power grid is not powered off, it is judged whether the step-by-step power supply is powered off according to the first output voltage and the first frequency, if the step-by-step power supply is not powered off, the bus capacitor is charged according to the soft start rule, and the energy storage inverter is controlled to output the second output voltage for the power grid; if the step-by-step power supply is powered off, the energy storage inverter is controlled to output the second output voltage for the power grid according to the energy storage condition of the energy storage inverter.

[0019] Preferably, in the process of controlling the bus capacitor to charge according to the soft start rule, whether the difference between the voltage of the bus capacitor and the first output voltage and / or the third output voltage is less than a preset voltage value is collected;

[0020] If yes, the energy storage inverter is started, and the soft start is completed.

[0021] The application discloses a bus capacitor soft start system for an energy storage inverter.

[0022] The data acquisition module is used for collecting the first output voltage and the first frequency of the step-by-step power supply of the distributed energy storage micro-grid system in which the energy storage inverter is located, and the first input voltage of the load of the distributed energy storage micro-grid system after power conversion, wherein the step-by-step power supply is used for representing one or more combinations of wind power, hydroelectric power and photovoltaic power generation.

[0023] The soft start rule generation module is used for obtaining the soft start rule of the bus capacitor of the energy storage inverter according to the first output voltage and the first frequency.

[0024] The soft start module is used for controlling the bus capacitor to charge according to the soft start rule, and is used for controlling the second output voltage of the energy storage inverter to be the same amplitude and phase as the first input voltage, so as to complete phase locking.

[0025] The application discloses the following technical effects:

[0026] The application designs the soft start rule according to needs and different conditions, achieves satisfactory soft start characteristics, reduces the impact on the grid connection process, and improves the system reliability. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0028] Figure 1 The method flowchart described in the application is shown. DETAILED DESCRIPTION

[0029] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0030] As shown in Figure 1 The present application provides a bus capacitor soft starting method for an energy storage inverter, comprising the following steps:

[0031] The first output voltage and the first frequency of a step-by-step power supply of a distributed energy storage micro-grid system in which the energy storage inverter is located are collected, and a soft starting rule of a bus capacitor of the energy storage inverter is obtained, wherein the step-by-step power supply represents one or a combination of multiple of wind power, hydroelectric power and photovoltaic power generation;

[0032] The first input voltage of the load of the distributed energy storage micro-grid system after power conversion is collected, and the bus capacitor is controlled to charge according to the soft starting rule, so as to control the second output voltage of the energy storage inverter to be the same amplitude and phase as the first input voltage, and complete phase locking.

[0033] The step-by-step power supply mentioned in the present application can be one of wind power, hydroelectric power and photovoltaic power generation, can also be a combination of multiple implementations of power generation, or can be other clean energy. The present application determines whether the step-by-step power supply is in a stable power generation state or an optimal state according to the environment and working condition of the step-by-step power supply, when the optimal state exists, the step-by-step power supply in the optimal state is preferentially selected to supply power to the load and store energy; when the optimal state does not exist, the input voltage frequency is matched with the load to determine the power supply selection.

[0034] Further preferably, in the process of obtaining the soft starting rule, when the distributed energy storage micro-grid system is connected to an external grid for operation, the present application obtains the second input voltage of the external grid, the third output voltage and the second frequency of the third output voltage;

[0035] The present application generates the soft starting rule according to the first output voltage, the third output voltage, the first frequency and the second frequency.

[0036] Further preferably, in the process of controlling the bus capacitor to charge according to the soft-start rule, the application controls the bus capacitor to charge according to the soft-start rule according to the first input voltage and the second input voltage, controls the second output voltage of the energy storage inverter to be of the same amplitude and phase as the first input voltage and the second input voltage respectively, and completes phase locking.

[0037] Generally, the step-by-step energy storage micro-grid system is connected to the external grid for operation, which aims to connect the excess energy to the external grid or introduce the external grid energy to power the micro-grid system. At this time, the control strategy is different from that when the micro-grid operates alone, mainly in the strategy for powering the load. When the micro-grid operates alone, the load is powered by the step-by-step power supply and the energy storage in the energy storage inverter. Generally, this case is suitable for areas with small electricity consumption and stable external clean energy, which can achieve electricity balance. However, in the case of unstable external energy, the connection of the external grid needs to be considered, and the external grid is controlled by the energy storage inverter to provide suitable voltage for the load. Whether the external grid or the step-by-step power supply, there is a power loss state. Therefore, when controlling the overall system, the power loss problem needs to be considered.

[0038] Further preferably, in the process of controlling the second output voltage to complete phase locking with the first input voltage, the application determines whether the step-by-step power supply loses power according to the first output voltage and the first frequency, and determines whether the external grid loses power according to the third output voltage and the second frequency.

[0039] According to the power loss condition, the application controls the bus capacitor to charge according to the soft-start rule, and controls the energy storage inverter to output the second output voltage for the load.

[0040] Further preferably, in the process of controlling the energy storage inverter to output the second output voltage for the load, the application determines whether the step-by-step power supply loses power according to the first output voltage and the first frequency. When the step-by-step power supply does not lose power, the application controls the bus capacitor to charge according to the soft-start rule, and controls the energy storage inverter to output the second output voltage for the load through the step-by-step power supply.

[0041] When the step-by-step power supply loses power, the application determines whether the external grid loses power according to the third output voltage and the second frequency. If the external grid loses power, the application controls the energy storage inverter to output the second output voltage for the load. If the external grid does not lose power, the application controls the bus capacitor to charge according to the soft-start rule, and controls the energy storage inverter to output the second output voltage for the load through the external grid.

[0042] Further preferably, in the process of controlling the second output voltage to complete phase locking with the second input voltage, the application determines whether the external grid loses power according to the third output voltage and the second frequency.

[0043] When the external power grid is powered off, the control energy storage inverter is off-grid with the external power grid;

[0044] When the external power grid is not powered off, whether the step-by-step power supply is powered off is judged according to the first output voltage and the first frequency, if the step-by-step power supply is not powered off, the bus capacitor is charged according to the soft start rule, and the control energy storage inverter outputs the second output voltage for the power grid, if the step-by-step power supply is powered off, the control energy storage inverter outputs the second output voltage for the power grid according to the energy storage condition of the energy storage inverter.

[0045] Further preferably, in the process of charging the bus capacitor according to the soft start rule, the application collects whether the difference between the voltage of the bus capacitor and the first output voltage and / or the third output voltage is less than the preset voltage value;

[0046] If yes, start the energy storage inverter and complete the soft start.

[0047] In the above-mentioned capacitor soft start process designed by the application, the soft start rule needs to consider various situations, that is, the soft start rule is a rule formulated according to different operating conditions, through data acquisition and analysis, and then the appropriate soft start rule is selected to charge the bus capacitor, which ensures the stability of the energy storage inverter after soft start, and ensures that the bus capacitor is not damaged due to excessive current during charging.

[0048] The application discloses a bus capacitor soft start system for an energy storage inverter, comprising:

[0049] The data acquisition module is used for acquiring the first output voltage and the first frequency of the step-by-step power supply of the distributed energy storage micro-grid system where the energy storage inverter is located, and the first input voltage of the load of the distributed energy storage micro-grid system after power conversion, wherein the step-by-step power supply represents one or more combinations of wind power, hydroelectric power and photovoltaic power generation;

[0050] The soft start rule generation module is used for acquiring the soft start rule of the bus capacitor of the energy storage inverter according to the first output voltage and the first frequency;

[0051] The soft start module is used for controlling the bus capacitor to charge according to the soft start rule, and is used for controlling the second output voltage of the energy storage inverter to be the same amplitude and phase as the first input voltage, and completing phase locking.

[0052] The working scheme of the energy storage inverter when the micro-grid system is independently operated and the working scheme of the energy storage inverter when the micro-grid system is connected with the external power grid are designed, the bus capacitor soft start is designed, the fault caused by excessive current in the energy storage and grid connection of the energy storage inverter is avoided, the safe and stable operation of the whole system is ensured, and the safety of the application of the energy storage inverter is ensured.

[0053] The computer program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other processing device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other processing device to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions specified in the flowchart block or blocks or in conjunction with the flowcharts and / or block diagram. Figure 1 one or more of the blocks or steps in the flowchart or flowchart diagrams. Figure 1 one or more of the blocks or steps in the flowchart or flowchart diagrams.

[0054] In the description of the present application, it is to be understood that the terms "first", "second", "third" and the like, merely identify features belonging to distinct categories, and do not imply or imply a relative importance or a specific number thereof. Thus, a feature defined with "first", "second", or "third" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality" is two or more, unless otherwise explicitly specified.

[0055] Although the embodiments of the present application have been shown and described above, it is to be understood that the above-described embodiments are exemplary, and are not to be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A bus capacitor soft start method for an energy storage inverter, characterized by, The method comprises the following steps: Collecting a first output voltage and a first frequency of a step-by-step power source of a distributed energy storage microgrid system in which an energy storage inverter is located, and obtaining a soft start rule of a bus capacitor of the energy storage inverter, wherein the step-by-step power source represents one or more combinations of wind power, hydroelectric power, and photovoltaic power generation; Collecting a first input voltage of a load of the distributed energy storage microgrid system after power conversion, and controlling the bus capacitor to charge according to the soft start rule, so as to control a second output voltage of the energy storage inverter to have the same amplitude and phase as the first input voltage, and complete phase locking; During the process of obtaining the soft start rule, when the distributed energy storage microgrid system is connected to an external power grid for operation, a second input voltage of the external power grid, a third output voltage, and a second frequency of the third output voltage are obtained; According to the first output voltage, the third output voltage, the first frequency, and the second frequency, the soft start rule is generated; During the process of controlling the bus capacitor to charge according to the soft start rule, according to the first input voltage and the second input voltage, the bus capacitor is controlled to charge according to the soft start rule, so as to control the second output voltage of the energy storage inverter to have the same amplitude and phase as the first input voltage and the second input voltage respectively, and complete phase locking; During the process of controlling the second output voltage and the first input voltage to complete phase locking, whether the step-by-step power source loses power is judged according to the first output voltage and the first frequency, and whether the external power grid loses power is judged according to the third output voltage and the second frequency; According to the power loss condition, the bus capacitor is controlled to charge according to the soft start rule, and the energy storage inverter outputs the second output voltage to the load.

2. The method according to claim 1, wherein: During the process of controlling the energy storage inverter to output the second output voltage to the load, whether the step-by-step power source loses power is judged according to the first output voltage and the first frequency, and when the step-by-step power source does not lose power, the bus capacitor is controlled to charge according to the soft start rule, and the energy storage inverter outputs the second output voltage to the load through the step-by-step power source; When the step-by-step power source loses power, whether the external power grid loses power is judged according to the third output voltage and the second frequency, and if the external power grid loses power, the energy storage inverter outputs the second output voltage to the load; if the external power grid does not lose power, the bus capacitor is controlled to charge according to the soft start rule, and the energy storage inverter outputs the second output voltage to the load through the external power grid.

3. The method according to claim 2, wherein: During the process of controlling the second output voltage and the second input voltage to complete phase locking, whether the external power grid loses power is judged according to the third output voltage and the second frequency; When the external power grid loses power, the energy storage inverter is controlled to be off-grid with the external power grid. If the external power grid is not powered off, it is determined whether the step-by-step power supply is powered off according to the first output voltage and the first frequency. If the step-by-step power supply is not powered off, the bus capacitor is charged according to the soft-start rule, and the energy storage inverter is controlled to output the second output voltage to the power grid. If the step-by-step power supply is powered off, the energy storage inverter is controlled to output the second output voltage to the power grid according to the energy storage condition of the energy storage inverter.

4. The bus capacitor soft-start method for an energy storage inverter according to claim 3, characterized in that: In the process of charging the bus capacitor according to the soft-start rule, it is determined whether the difference between the voltage of the bus capacitor and the first output voltage and / or the third output voltage is less than a preset voltage value; If yes, the energy storage inverter is started to complete soft-start.

5. A bus capacitor soft start system for energy storage inverters for implementing a bus capacitor soft start method for energy storage inverters as claimed in claim 1, characterized by, Comprise: a data acquisition module for acquiring the first output voltage and the first frequency of the step-by-step power supply of the distributed energy storage microgrid system in which the energy storage inverter is located, and the first input voltage of the load of the distributed energy storage microgrid system after power conversion, wherein the step-by-step power supply represents one or more combinations of wind power, hydroelectric power, and photovoltaic power generation; a soft-start rule generation module for obtaining the soft-start rule of the bus capacitor of the energy storage inverter according to the first output voltage and the first frequency; a soft-start module for controlling the bus capacitor to charge according to the soft-start rule, and for controlling the second output voltage of the energy storage inverter to be the same amplitude and phase as the first input voltage to complete phase locking.

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