Starting method and system for multi-machine parallel system of network construction type energy storage converter

Abstract

The invention provides a method and a system for starting a multi-machine parallel system of a network construction type energy storage converter, relates to the technical field of energy storage system control, and is applied to the multi-machine parallel system comprising a plurality of network construction type energy storage converters. Configuring a starting parameter for judging a synchronization condition and a grid-connected time sequence; determining a target reference voltage source according to the operation condition and the real-time state data of each grid-forming type energy storage converter; based on the target reference voltage source, executing pre-synchronization control on a to-be-connected converter in the multi-machine parallel system; and when the to-be-grid-connected converter meets the synchronization condition corresponding to the starting parameter, the to-be-grid-connected converter is connected into the multi-machine parallel system by using the output power obtained by the flexible cut-in control algorithm based on the grid-connected time sequence. According to the method, the control process of'detection-synchronization-flexible cut-in 'is constructed, so that the method is suitable for different operation conditions, and rapid, flexible and impact-free starting of the multi-machine parallel system in different scenes is realized.

Description

Technical Field

[0001] This invention relates to the field of energy storage system control technology, specifically to a startup method and system for a grid-type energy storage converter multi-machine parallel system. Background Technology

[0002] As core equipment in microgrids and distributed energy systems, grid-connected energy storage converters rely on parallel operation of multiple units for improving system capacity and reliability. However, the coordinated startup of multi-unit parallel systems faces three major technical challenges: First, synchronization accuracy issues, where differences in voltage phase, amplitude, and frequency among converters can lead to huge inrush currents; second, operating condition adaptability issues, where frequency drift is prone to occur due to the lack of grid reference in off-grid conditions, while in grid-connected conditions, simultaneous tracking of grid signals is crucial to avoid disturbances to the point of common coupling; and third, coordinated control issues, where traditional multi-unit parallel startup methods can lead to circulating current superposition, while simple timing control can prolong startup time.

[0003] Therefore, when a multi-machine parallel system of a grid-connected energy storage converter in the existing technology starts up, the lack of an intelligent coordination mechanism results in poor synchronization accuracy, weak adaptability to operating conditions, and large inrush current. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a startup method for a multi-unit parallel system of grid-connected energy storage converters, applicable to a multi-unit parallel system containing multiple grid-connected energy storage converters. The method includes: Detect the operating status of a multi-machine parallel system and configure startup parameters for determining synchronization conditions and grid connection timing; The target reference voltage source is determined based on the operating conditions and real-time status data of each grid-type energy storage converter; Based on the target reference voltage source, pre-synchronization control is performed on the grid-connected converter in a multi-machine parallel system; When the converter to be connected to the grid meets the synchronization conditions corresponding to the start-up parameters, based on the grid connection timing, the output power obtained by the flexible cut-in control algorithm is used to connect the converter to the grid into the multi-machine parallel system.

[0005] Preferably, the target reference voltage source is determined based on the operating conditions and real-time status data of each grid-type energy storage converter, including: If the operating condition is off-grid, then based on the real-time status data of each grid-connected energy storage converter, one of the multiple grid-connected energy storage converters is selected as the main converter, and the output voltage of the main converter is determined as the target reference voltage source. If the operating condition is grid-connected, then the grid voltage is determined as the target reference voltage source.

[0006] Preferably, based on the real-time status data of each grid-type energy storage converter, one converter is selected from multiple grid-type energy storage converters as the main converter, and the voltage of the main converter is determined as the target reference voltage source, including: The real-time status data of each grid-type energy storage converter is normalized. The real-time status data includes state of charge data, DC voltage data, and operating temperature. The normalized real-time status data is substituted into the main converter election algorithm to obtain the election value of each grid-type energy storage converter. The grid-type energy storage converter with the highest election value is selected as the main converter, and the output voltage of the main converter is selected as the target reference voltage source. The main converter election algorithm is as follows:

[0007]

[0008] in, For grid-type energy storage converter The election value, For grid-type energy storage converter Normalized state of charge data, For grid-type energy storage converter The normalized DC voltage data, For grid-type energy storage converter The normalized operating temperature, For grid-type energy storage converter Weighting coefficients for state of charge data, For grid-type energy storage converter Weighting coefficients for DC voltage data For grid-type energy storage converter Weighting factor for operating temperature.

[0009] Preferably, under off-grid conditions, the expression for the output voltage of the main converter is:

[0010] in, The output voltage of the main converter The voltage amplitude of the main converter. The angular frequency of the main converter. To set the initial phase, For time.

[0011] Preferably, the starting parameters used to determine synchronization conditions include a voltage threshold. Frequency threshold Phase threshold ; The grid-connected converter must meet the synchronization conditions corresponding to the startup parameters, including: When the deviation between the output voltage amplitude of the converter to be connected to the grid and the output voltage amplitude of the target reference voltage source is less than the voltage threshold, and the deviation between the angular frequency of the converter to be connected to the grid and the angular frequency of the target reference voltage source is less than the frequency threshold, and the deviation between the phase of the converter to be connected to the grid and the phase of the target reference voltage source is less than the phase threshold, it is determined that the converter to be connected to the grid meets the synchronization conditions corresponding to the start-up parameters. Wherein, voltage threshold Δ U th ≤2% U N The frequency threshold Δ ω th ≤0.05Hz, the phase threshold Δ θ th ≤2°.

[0012] Preferably, the pre-synchronization control adopts a dual closed-loop control structure; Based on the target reference voltage source, pre-synchronization control of the converters to be connected to the grid in a multi-machine parallel system includes: The voltage amplitude error between the converter to be connected to the grid and the target reference voltage source is processed by a PI regulator, and a reference signal for the inner current loop is output to realize the outer loop voltage control. In the dq coordinate system, inner-loop current control is achieved by adjusting the active and reactive components of the output current. The phase and frequency information of the target reference voltage source is extracted by a second-order generalized integrator-phase-locked loop model, and the frequency and phase of the converter to be connected to the grid are adjusted in a closed loop to achieve phase synchronization between the converter to be connected to the grid and the target reference voltage source. The second-order generalized integrator-phase-locked loop model is as follows:

[0013] in, The q-axis component is the input to the phase-locked loop. For the proportional coefficient of the second-order generalized integrator-phase-locked loop, These are the integral coefficients of a second-order generalized integrator-phase-locked loop. Nominal frequency, This is the output angular frequency of the phase-locked loop.

[0014] Preferably, the output power obtained by the flexible cut-in control algorithm is achieved through a power reference curve; The formula for calculating the power reference curve is as follows:

[0015] in, The power command at time t. This refers to the rated power of the grid-type energy storage converter. is the time constant.

[0016] Preferably, the pre-synchronization control also includes dynamic synchronization compensation; Based on a target reference voltage source, pre-synchronization control is performed on the grid-connected converters among multiple grid-connected energy storage converters, including: If fluctuations or changes are detected in the parameters of the target reference voltage source, all grid-connected energy storage converters will update their synchronization references in real time and re-execute pre-synchronization control.

[0017] Based on the same inventive concept, this invention also provides a starting system for a grid-connected energy storage converter multi-unit parallel system. The grid-connected energy storage converter multi-unit parallel system includes multiple grid-connected energy storage converters. The system comprises: The detection and configuration module is used to detect the operating conditions of a multi-machine parallel system and configure the startup parameters for judging synchronization conditions and grid connection timing. The reference voltage source determination module is used to determine the target reference voltage source based on the operating conditions and the real-time status data of each grid-type energy storage converter. The pre-synchronization control module is used to perform pre-synchronization control on the converter to be connected to the grid in a multi-machine parallel system based on the target reference voltage source; The grid connection execution module is used to connect the converter to be connected to the grid into the multi-machine parallel system when the converter meets the synchronization conditions corresponding to the start-up parameters, based on the grid connection timing and the output power obtained by the flexible cut-in control algorithm.

[0018] Preferably, the reference voltage source determination module includes: The off-grid operating condition voltage source determination module is used to select one of the multiple grid-connected energy storage converters as the main converter based on the real-time status data of each grid-connected energy storage converter if the operating condition is off-grid, and determine the output voltage of the main converter as the target reference voltage source. The grid-connected operating condition voltage source determination module is used to determine the grid voltage as the target reference voltage source if the operating condition is grid-connected.

[0019] Preferably, the off-grid voltage source determination module is specifically used for: The real-time status data of each grid-type energy storage converter is normalized. The real-time status data includes state of charge data, DC voltage data, and operating temperature. The normalized real-time status data is substituted into the main converter election algorithm to obtain the election value of each grid-type energy storage converter. The grid-type energy storage converter with the highest election value is selected as the main converter, and the output voltage of the main converter is selected as the target reference voltage source. The main converter election algorithm is as follows:

[0020]

[0021] in, For grid-type energy storage converter The election value, For grid-type energy storage converter Normalized state of charge data, For grid-type energy storage converter The normalized DC voltage data, For grid-type energy storage converter The normalized operating temperature, For grid-type energy storage converter Weighting coefficients for state of charge data, For grid-type energy storage converter Weighting coefficients for DC voltage data For grid-type energy storage converter Weighting factor for operating temperature.

[0022] Preferably, under off-grid conditions, the expression for the output voltage of the main converter is:

[0023] in, The output voltage of the main converter The voltage amplitude of the main converter. The angular frequency of the main converter. To set the initial phase, For time.

[0024] Preferably, the starting parameters used to determine synchronization conditions include a voltage threshold. Frequency threshold Phase threshold ; The grid-connected converter must meet the synchronization conditions corresponding to the startup parameters, including: When the deviation between the output voltage amplitude of the converter to be connected to the grid and the output voltage amplitude of the target reference voltage source is less than the voltage threshold, and the deviation between the angular frequency of the converter to be connected to the grid and the angular frequency of the target reference voltage source is less than the frequency threshold, and the deviation between the phase of the converter to be connected to the grid and the phase of the target reference voltage source is less than the phase threshold, it is determined that the converter to be connected to the grid meets the synchronization conditions corresponding to the start-up parameters. Wherein, voltage threshold Δ U th ≤2% UN The frequency threshold Δ ω th ≤0.05Hz, the phase threshold Δ θ th ≤2°.

[0025] Preferably, the pre-synchronization control adopts a dual closed-loop control structure; Based on the target reference voltage source, pre-synchronization control of the converters to be connected to the grid in a multi-machine parallel system includes: The voltage amplitude error between the converter to be connected to the grid and the target reference voltage source is processed by a PI regulator, and a reference signal for the inner current loop is output to realize the outer loop voltage control. In the dq coordinate system, inner-loop current control is achieved by adjusting the active and reactive components of the output current. The phase and frequency information of the target reference voltage source is extracted by a second-order generalized integrator-phase-locked loop model, and the frequency and phase of the converter to be connected to the grid are adjusted in a closed loop to achieve phase synchronization between the converter to be connected to the grid and the target reference voltage source. The second-order generalized integrator-phase-locked loop model is as follows:

[0026] in, The q-axis component is the input to the phase-locked loop. For the proportional coefficient of the second-order generalized integrator-phase-locked loop, These are the integral coefficients of a second-order generalized integrator-phase-locked loop. Nominal frequency, This is the output angular frequency of the phase-locked loop.

[0027] Preferably, the output power obtained by the flexible cut-in control algorithm is achieved through a power reference curve; The formula for calculating the power reference curve is as follows:

[0028] in, The power command at time t. This refers to the rated power of the grid-type energy storage converter. is the time constant.

[0029] Preferably, the pre-synchronization control also includes dynamic synchronization compensation; The pre-synchronization control module is also used to: if fluctuations or changes are detected in the parameters of the target reference voltage source, all grid-connected energy storage converters to be connected to the grid will update the synchronization reference in real time and re-execute the pre-synchronization control.

[0030] Based on the same inventive concept, the present invention also provides an electronic device, comprising: at least one processor and a memory; wherein the memory and the processor are connected via a bus; The memory is used to store one or more programs; When the one or more programs are executed by the at least one processor, a startup method for a multi-machine parallel grid-connected energy storage converter system as described above is implemented.

[0031] Based on the same inventive concept, the present invention also provides a readable storage medium having an executable program stored thereon, wherein when the executable program is executed, it implements the startup method of a multi-machine parallel grid-type energy storage converter system as described above.

[0032] Compared with the closest existing technology, the present invention has the following beneficial effects: This invention provides a startup method for a multi-unit parallel system of grid-connected energy storage converters, applicable to a multi-unit parallel system containing multiple grid-connected energy storage converters. The method includes: detecting the operating conditions of the multi-unit parallel system and configuring startup parameters for determining synchronization conditions and grid connection timing; determining a target reference voltage source based on the operating conditions and real-time status data of each grid-connected energy storage converter; performing pre-synchronization control on the converters to be connected to the grid in the multi-unit parallel system based on the target reference voltage source; and when the converter to be connected to the grid meets the synchronization conditions corresponding to the startup parameters, connecting the converter to be connected to the grid into the multi-unit parallel system based on the grid connection timing and the output power obtained by the flexible cut-in control algorithm. This invention uses real-time status data of the converter as the basis for decision-making to ensure the determination of the target reference power supply under operating conditions. By defining precise start-up parameters and executing synchronous control, it achieves high-precision synchronization of voltage, frequency, and phase between the pre-target reference voltage sources of the converter, suppressing the generation of inrush current. By constructing a "detection-synchronization-flexible entry" control process, it is applicable to different operating conditions, realizing rapid, flexible, and shock-free start-up of multi-machine parallel systems in different scenarios, and improving the overall dynamic performance and robustness of the system. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating the startup method of a multi-machine parallel system of a grid-type energy storage converter provided by the present invention. Figure 2 This is a block diagram of the dual closed-loop control structure provided by the present invention; Figure 3 A schematic diagram of a multi-unit parallel-off-grid system for a grid-type energy storage converter provided by the present invention; Figure 4 This is a block diagram of the synchronization control structure provided by the present invention; Figure 5 This is a structural diagram of the starting system of the multi-machine parallel grid-type energy storage converter system provided by the present invention; Figure 6 A schematic diagram of the electronic device provided by the present invention. Detailed Implementation

[0034] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0035] Example 1: This invention provides a startup method for a multi-unit parallel system of grid-connected energy storage converters, applicable to such systems. Specifically, as shown... Figure 1 The figure shows a flowchart illustrating the startup method of a multi-unit parallel grid-connected energy storage converter system provided in an embodiment of the present invention. The method includes the following steps: S101: Detects the operating status of a multi-machine parallel system and configures startup parameters for judging synchronization conditions and grid connection timing; S102: Determine the target reference voltage source based on the operating conditions and the real-time status data of each grid-type energy storage converter; S103: Based on the target reference voltage source, perform pre-synchronization control on the grid-connected converter in a multi-machine parallel system; S104: When the converter to be connected to the grid meets the synchronization conditions corresponding to the start-up parameters, based on the grid connection timing, the converter to be connected to the grid is connected to the multi-machine parallel system using the output power obtained by the flexible cut-in control algorithm.

[0036] This invention uses real-time status data of the converter as the basis for decision-making to ensure the determination of the target reference power supply under operating conditions. By defining precise start-up parameters and executing synchronous control, it achieves high-precision synchronization of voltage, frequency, and phase between the pre-target reference voltage sources of the converter, suppressing the generation of inrush current. By constructing a "detection-synchronization-flexible entry" control process, it is applicable to different operating conditions, realizing rapid, flexible, and shock-free start-up of multi-machine parallel systems in different scenarios, and improving the overall dynamic performance and robustness of the system.

[0037] The startup method for a multi-machine parallel system of grid-type energy storage converters provided by the present invention is applied to a multi-machine parallel system containing multiple grid-type energy storage converters, and is used to start up and control the multiple grid-type energy storage converters in the multi-machine parallel system.

[0038] First, the multi-machine parallel system is initialized, its operating conditions are checked, and startup parameters are configured. These startup parameters are used to subsequently determine synchronization conditions and grid connection timing. Specifically, the startup parameters used to determine synchronization conditions include voltage thresholds. Frequency threshold Phase threshold ; Grid connection sequence, which is the preset grid connection sequence number of multiple grid-connected energy storage converters.

[0039] After initialization, the target reference voltage source is determined based on the operating conditions and the real-time status data of each grid-connected energy storage converter. This includes: if the operating condition is off-grid, then one of the multiple grid-connected energy storage converters is selected as the main converter based on the real-time status data of each grid-connected energy storage converter, and the output voltage of the main converter is determined as the target reference voltage source; if the operating condition is grid-connected, then the grid voltage is determined as the target reference voltage source.

[0040] When the system initialization detects that the operating condition is off-grid, one grid-type energy storage converter is selected as the master converter from the multiple grid-type energy storage converters in the multi-machine parallel system, and the remaining grid-type energy storage converters are slave converters. The target reference voltage source is determined based on the master converter.

[0041] In some alternative implementations, the main converter and the target reference voltage source are determined as follows: based on the real-time status data of each grid-connected energy storage converter, one of the multiple grid-connected energy storage converters is selected as the main converter, and the voltage of the main converter is determined as the target reference voltage source.

[0042] Specifically, the real-time status data of each grid-type energy storage converter is normalized. The real-time status data includes state of charge data, DC voltage data, and operating temperature. The normalized real-time status data is substituted into the main converter election algorithm to obtain the election value of each grid-type energy storage converter. The grid-type energy storage converter with the highest election value is selected as the main converter, and the output voltage of the main converter is selected as the target reference voltage source. The main converter election algorithm is as follows:

[0043]

[0044] in, For grid-type energy storage converter The election value, For grid-type energy storage converter Normalized state of charge data, For grid-type energy storage converter The normalized DC voltage data, For grid-type energy storage converter The normalized operating temperature, For grid-type energy storage converter Weighting coefficients for state of charge data, For grid-type energy storage converter Weighting coefficients for DC voltage data For grid-type energy storage converter Weighting factor for operating temperature.

[0045] In practical applications, the weighting coefficients can be dynamically adjusted according to the system design objectives. , , If the system prioritizes endurance (such as off-grid microgrids), the weighting coefficient can be increased. ,For example If the system prioritizes equipment safety (e.g., high-temperature environments), the weighting coefficient can be increased. ,For example Weighting coefficients , , The selection criteria are based on the desired performance, and these three weighting coefficients ensure that the present invention has sufficient adaptability.

[0046] Generally, The recommended value is 0.4 to 0.6. The recommended value is 0.2 to 0.4. The recommended value is 0.1 to 0.3.

[0047] Under off-grid conditions, the expression for the output voltage of the main converter is:

[0048] in, The output voltage of the main converter The voltage amplitude of the main converter. The angular frequency of the main converter. To set the initial phase, For time.

[0049] If the operating condition is grid-connected, the grid voltage is determined as the target reference voltage source. Specifically, when the system initialization detects that the operating condition is grid-connected, the multi-machine parallel system uses the grid voltage as the target reference voltage source.

[0050] Whether in off-grid or grid-connected operation, once the target reference voltage source is determined, pre-synchronization control is performed on the converters to be connected to the grid in the multi-machine parallel system based on the target reference voltage source.

[0051] In some alternative implementations, the pre-synchronization control employs a dual closed-loop control structure; Based on the target reference voltage source, pre-synchronization control of the converters to be connected to the grid in a multi-machine parallel system includes: The voltage amplitude error between the converter to be connected to the grid and the target reference voltage source is processed by a PI regulator, and a reference signal for the inner current loop is output to realize the outer loop voltage control. In the dq coordinate system, inner-loop current control is achieved by adjusting the active and reactive components of the output current. The phase and frequency information of the target reference voltage source is extracted by a second-order generalized integrator-phase-locked loop model, and the frequency and phase of the converter to be connected to the grid are adjusted in a closed loop to achieve phase synchronization between the converter to be connected to the grid and the target reference voltage source. The second-order generalized integrator-phase-locked loop model is as follows:

[0052] in, The q-axis component is the input to the phase-locked loop. For the proportional coefficient of the second-order generalized integrator-phase-locked loop, These are the integral coefficients of a second-order generalized integrator-phase-locked loop. The nominal frequency is typically 2*pi*50Hz. This is the output angular frequency of the phase-locked loop.

[0053] like Figure 2 The diagram shown is a block diagram of the dual closed-loop control structure provided by the present invention. In a specific implementation, the pre-synchronization control using the dual closed-loop control structure includes: Outer loop voltage control (via voltage control loop): A PI regulator handles the voltage amplitude error between the converter to be connected to the grid and the target reference voltage source. The amplitude reference of the inner loop of the output current. This serves as the target reference voltage source for both off-grid and grid-connected operating conditions. For the first Output voltage amplitude of the grid-connected converter. This refers to the voltage amplitude error. The voltage reference signal is in the dq rotating coordinate system. This is the voltage reference signal in the abc three-phase stationary coordinate system. This voltage amplitude error measures the difference between the voltage amplitude output by the converter to be connected to the grid and the voltage amplitude of the target reference voltage source followed by the system.

[0054] Inner loop current control (same specification current control loop): Current closed-loop control based on the dq coordinate system, which adjusts the active and reactive components of the output current. This is a reference value for the total current amplitude. For the first Output current amplitude of the converter to be connected to the grid. This refers to the current amplitude error.

[0055] Frequency and phase adjustment: The phase information of the reference voltage is extracted through a second-order generalized integrator-phase-locked loop, and the angular frequency error is processed by a PI regulator. This achieves phase synchronization. The angular frequency of the target reference voltage source under off-grid or grid-connected operating conditions. For the first The angular frequency of the output voltage of the grid-connected converter. This refers to the angular frequency error. The angular frequency error measures the difference between the angular frequency of the output voltage of the converter to be connected to the grid and the angular frequency of the target reference voltage source. This represents the output voltage phase of the converter.

[0056] After performing pre-synchronization control on the converter to be connected to the grid in a multi-machine parallel system, it is determined whether the converter meets the synchronization conditions corresponding to the startup parameters. Specifically, the startup parameters used to determine the synchronization conditions include voltage thresholds. Frequency threshold Phase threshold ; The grid-connected converter must meet the synchronization conditions corresponding to the startup parameters, including: When the deviation between the output voltage amplitude of the converter to be connected to the grid and the output voltage amplitude of the target reference voltage source is less than the voltage threshold, and the deviation between the angular frequency of the converter to be connected to the grid and the angular frequency of the target reference voltage source is less than the frequency threshold, and the deviation between the phase of the converter to be connected to the grid and the phase of the target reference voltage source is less than the phase threshold, it is determined that the converter to be connected to the grid meets the synchronization conditions corresponding to the start-up parameters. Wherein, voltage threshold Δ U th ≤2% U N The frequency threshold Δ ω th ≤0.05Hz, the phase threshold Δ θ th ≤2°. For a reference voltage, such as when the bus voltage is 380V, Δ U th ≤2%*380V.

[0057] like Figure 3The diagram shows a multi-unit parallel-off-grid system of a grid-connected energy storage converter. When operating in off-grid mode, pre-synchronization control of the slave converter includes: error adjustment via a proportional-integral regulator to ensure the slave converter's output voltage... Tracking main converter voltage When the synchronization condition is met , and At that time, the converters are connected to the multi-machine parallel system sequentially according to the preset sequence number, among which, For the first The output voltage amplitude of the converter awaiting grid connection. For the first The angular frequency of the output voltage from the converter, which is awaiting grid connection. For the first The phase of the output voltage from the converter is waiting to be connected to the grid. The output voltage amplitude of the main converter The output voltage angular frequency of the main converter. The output voltage phase of the main converter. When the converter to be connected to the grid meets the synchronization conditions corresponding to the start-up parameters, based on the grid connection timing, the output power obtained by the flexible cut-in control algorithm is used to connect the converter to the grid into the multi-machine parallel system.

[0058] like Figure 4 The diagram shown is a block diagram of the pre-synchronization control structure. The first step is to obtain voltage, frequency, and phase through a phase-locked loop (PLL); the second step is to generate the active power deviation adjustment amount through PI regulation. and reactive power deviation adjustment The third step is to adjust the power loop accordingly. , Adjustments are made to obtain the internal potential amplitude. and phase Specifically, , , The three-phase instantaneous voltage of the target reference voltage source. , , The three-phase instantaneous voltage of the converter to be connected to the grid. , , From , , The voltage amplitude, angular frequency, and phase of the target reference voltage source are extracted. , , From , , The output voltage amplitude, angular frequency, and phase of the converter to be connected to the grid are extracted. This is then processed... PI proportional-integral controller processing and The voltage amplitude error between them is converted into reactive power deviation adjustment. At the same time, utilizing processing PI proportional-integral controller processing and The angular frequency error between them is converted into active power deviation adjustment. This is further superimposed on the reactive power loop. ,in This is the initial reactive power reference value. This serves as the final reactive power reference value. Then, it is adjusted using anti-saturation gain. This is a correction stage introduced to prevent integral saturation in the PI proportional-integral regulator, ultimately yielding the internal potential amplitude. At the same time, it is superimposed on the active power loop. ,in This is the initial active power reference value. This is the final active power reference value. Then, it is determined by the rated angular frequency. Effect on In terms of time, further based on virtual rotational inertia The virtual damping coefficient D is used to obtain the phase. .

[0059] Specifically, the output power obtained by the flexible cut-in control algorithm is achieved through a power reference curve; The formula for calculating the power reference curve is as follows:

[0060] in, The power command at time t. This refers to the rated power of the grid-type energy storage converter. It is a time constant. Generally, The value range is 0.1s-0.5s.

[0061] In addition to allowing all converters to operate in parallel, flexible switching also requires outputting power according to a set curve, because each converter has a power setting value.

[0062] In some alternative implementations, the pre-synchronization control also includes dynamic synchronization compensation; Based on a target reference voltage source, pre-synchronization control is performed on the grid-connected converters among multiple grid-connected energy storage converters, including: If fluctuations or changes are detected in the parameters of the target reference voltage source, all grid-connected energy storage converters will update their synchronization references in real time and re-execute pre-synchronization control.

[0063] Taking a microgrid system consisting of four 100kVA grid-type energy storage converters as an example, the starting method of the multi-machine parallel grid-type energy storage converter system provided by the present invention will be described in detail.

[0064] 1. Off-grid startup process 1) Upon system power-on initialization, no voltage was detected at the common connection point, indicating an off-grid operating condition; 2) Collect status data for each converter, including the normalized state of charge (SOC) data for each converter (SOC=[0.9,0.85,0.92,0.88]) and the normalized DC voltage data for each converter. U dc =[800,790,810,795]V, normalized operating temperature of each converter T =[45,42,48,43]℃; 3) Normalize the status data of each converter and calculate the result based on the main converter election mechanism. Converter No. 3 was selected as the main converter. Specifically, the rated DC voltage was set. ,but They are: 1.0 (No. 1), 0.99 (No. 2), 1.01 (No. 3), and 0.99 (No. 4); minimum temperature. Maximum temperature The temperature term is The values ​​are 0.5 (No. 1), 0.8 (No. 2), 0.2 (No. 3), and 0.7 (No. 4), respectively. After substituting, we obtain the value of S.

[0065] 4) The main converter starts in grid-type control mode and establishes a 380V / 50Hz three-phase voltage within 100ms.

[0066] 5) For the start-up and synchronization control of converters 1, 2, and 4, the parameters of the second-order generalized integrator-phase-locked loop are set as follows: , .

[0067] 6) Converter No. 1 first meets the synchronization condition (voltage difference Δ U =0.5%, angular frequency difference Δ ω =0.02Hz, phase difference Δ θ =1.2°), triggering the grid connection process.

[0068] 7) Perform a flexible cut-in according to the aforementioned power reference curve. The current will reach the rated value after 500ms.

[0069] 8) After an interval of 100ms, converter No. 2 meets the synchronization conditions and is connected to the grid, and converter No. 4 is connected to the grid in sequence.

[0070] 2. Start-up procedure under grid-connected conditions 1) A voltage of 380V / 50Hz was detected at the point of common coupling, indicating grid-connected operation. 2) All converters lock the grid phase through a second-order generalized integrator-phase-locked loop. ,frequency Amplitude ; 3) Each converter performs pre-synchronization control to adjust the output voltage parameters to track the power grid; 4) Connect to the grid sequentially according to the preset sequence number 1→2→3→4, with a grid connection interval of 100ms between each converter; 5) After grid connection is completed, the total system capacity reaches 400kVA, and the load is evenly distributed among the converters.

[0071] This invention establishes a flexible start-up method for multi-machine systems that combines high-precision synchronization, multi-condition adaptability, and shock-free characteristics. The core of this method lies in constructing a three-layer control architecture of "detection-synchronization-switching". Through precise mathematical modeling and control algorithm design, the flexible start-up of a multi-machine parallel system of grid-type converters is realized.

[0072] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) An adaptive selection mechanism for the main converter based on weighted evaluation is proposed to solve the problem of establishing a reference source under off-grid conditions. Compared with the fixed master-slave method, it can provide system reliability.

[0073] 2) Establish a pre-synchronization control model that includes a second-order generalized integrator-phase-locked loop. Through the three-loop coordinated control consisting of voltage loop, frequency loop and phase loop, high-precision synchronization of voltage amplitude, frequency and phase can be achieved, which can reduce synchronization error compared with traditional methods.

[0074] 3) The design of an exponential flexible cut-in curve, combined with a time-sequence grid connection strategy, greatly reduces the inrush current.

[0075] 4) Construct a unified off-grid / grid-connected startup framework and achieve seamless startup in all scenarios through an adaptive switching algorithm based on operating conditions.

[0076] Example 2: Based on the same inventive concept, this invention also provides a starting system 500 for a grid-type energy storage converter multi-unit parallel system. The grid-type energy storage converter multi-unit parallel system includes multiple grid-type energy storage converters, and the system structure is as follows: Figure 5 As shown, the system includes: The detection configuration module 501 is used to detect the operating conditions of the multi-machine parallel system and configure the startup parameters for judging the synchronization conditions and grid connection timing. The reference voltage source determination module 502 is used to determine the target reference voltage source based on the operating conditions and the real-time status data of each grid-type energy storage converter. The pre-synchronization control module 503 is used to perform pre-synchronization control on the grid-connected converter in a multi-machine parallel system based on the target reference voltage source. The grid connection execution module 504 is used to connect the converter to be connected to the grid into the multi-machine parallel system based on the grid connection timing and the output power obtained by the flexible cut-in control algorithm when the converter to be connected to the grid meets the synchronization conditions corresponding to the start-up parameters.

[0077] Preferably, the reference voltage source determination module 502 includes: The off-grid operating condition voltage source determination module is used to select one of the multiple grid-connected energy storage converters as the main converter based on the real-time status data of each grid-connected energy storage converter if the operating condition is off-grid, and determine the output voltage of the main converter as the target reference voltage source. The grid-connected operating condition voltage source determination module is used to determine the grid voltage as the target reference voltage source if the operating condition is grid-connected.

[0078] Preferably, the off-grid voltage source determination module is specifically used for: The real-time status data of each grid-type energy storage converter is normalized. The real-time status data includes state of charge data, DC voltage data, and operating temperature. The normalized real-time status data is substituted into the main converter election algorithm to obtain the election value of each grid-type energy storage converter. The grid-type energy storage converter with the highest election value is selected as the main converter, and the output voltage of the main converter is selected as the target reference voltage source. The main converter election algorithm is as follows:

[0079]

[0080] in, For grid-type energy storage converter The election value, For grid-type energy storage converter Normalized state of charge data, For grid-type energy storage converter The normalized DC voltage data, For grid-type energy storage converter The normalized operating temperature, For grid-type energy storage converter Weighting coefficients for state of charge data, For grid-type energy storage converter Weighting coefficients for DC voltage data For grid-type energy storage converter Weighting factor for operating temperature.

[0081] Preferably, under off-grid conditions, the expression for the output voltage of the main converter is:

[0082] in, The output voltage of the main converter The voltage amplitude of the main converter. The angular frequency of the main converter. To set the initial phase, For time.

[0083] Preferably, the starting parameters used to determine synchronization conditions include a voltage threshold. Frequency threshold Phase threshold ; The grid-connected converter must meet the synchronization conditions corresponding to the startup parameters, including: When the deviation between the output voltage amplitude of the converter to be connected to the grid and the output voltage amplitude of the target reference voltage source is less than the voltage threshold, and the deviation between the angular frequency of the converter to be connected to the grid and the angular frequency of the target reference voltage source is less than the frequency threshold, and the deviation between the phase of the converter to be connected to the grid and the phase of the target reference voltage source is less than the phase threshold, it is determined that the converter to be connected to the grid meets the synchronization conditions corresponding to the start-up parameters. Wherein, voltage threshold Δ U th ≤2% U N The frequency threshold Δ ω th ≤0.05Hz, the phase threshold Δ θ th ≤2°.

[0084] Preferably, the pre-synchronization control adopts a dual closed-loop control structure; Based on the target reference voltage source, pre-synchronization control of the converters to be connected to the grid in a multi-machine parallel system includes: The voltage amplitude error between the converter to be connected to the grid and the target reference voltage source is processed by a PI regulator, and a reference signal for the inner current loop is output to realize the outer loop voltage control. In the dq coordinate system, inner-loop current control is achieved by adjusting the active and reactive components of the output current. The phase and frequency information of the target reference voltage source is extracted by a second-order generalized integrator-phase-locked loop model, and the frequency and phase of the converter to be connected to the grid are adjusted in a closed loop to achieve phase synchronization between the converter to be connected to the grid and the target reference voltage source. The second-order generalized integrator-phase-locked loop model is as follows:

[0085] in, The q-axis component is the input to the phase-locked loop. For the proportional coefficient of the second-order generalized integrator-phase-locked loop, These are the integral coefficients of a second-order generalized integrator-phase-locked loop. Nominal frequency, This is the output angular frequency of the phase-locked loop.

[0086] Preferably, the output power obtained by the flexible cut-in control algorithm is achieved through a power reference curve; The formula for calculating the power reference curve is as follows:

[0087] in, The power command at time t. This refers to the rated power of the grid-type energy storage converter. is the time constant.

[0088] Preferably, the pre-synchronization control also includes dynamic synchronization compensation; The pre-synchronization control module 503 is also used to: if fluctuations or changes are detected in the parameters of the target reference voltage source, all grid-connected energy storage converters to be connected to the grid update the synchronization reference in real time and re-execute the pre-synchronization control.

[0089] Example 3: Based on the same inventive concept, such as Figure 6 As shown, the present invention also provides an electronic device, which may be a computer device, a microcontroller device, a smart mobile device, etc. The electronic device in this embodiment may include a processor, a memory, a transceiver component, etc. The memory, processor, and transceiver component are connected via a bus; the memory can be used to store executable programs, and an exemplary executable program may include instructions; the processor is used to execute the instructions stored in the memory. The memory can also be used to store data, which can be accessed and / or modified when instructions are executed.

[0090] The processor may be a Central Processing Unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and it is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in a readable storage medium to realize the corresponding method flow or corresponding function, so as to realize the steps of the startup method of a multi-machine parallel grid-type energy storage converter system in the above embodiments.

[0091] Example 4: Based on the same inventive concept, this invention also provides a readable storage medium, specifically an electronic device readable storage medium (Memory). This readable storage medium is a memory device within an electronic device used to store programs and data. It is understood that the readable storage medium here can include both the built-in storage medium within the electronic device and extended storage media supported by the electronic device. The storage medium provides storage space, which stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more executable programs (including program code). It should be noted that the storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the storage medium to implement the steps of the startup method for a multi-machine parallel grid-connected energy storage converter system in the above embodiments.

[0092] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0093] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0094] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0095] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the application, but these changes, modifications or equivalent substitutions are all within the scope of protection of the claims pending approval.

Claims

1. A startup method for a multi-unit parallel grid-connected energy storage converter system, characterized in that, The method, applied to a multi-machine parallel system comprising multiple grid-connected energy storage converters, includes: The operating status of the multi-machine parallel system is detected, and startup parameters are configured to determine the synchronization conditions and grid connection timing. The target reference voltage source is determined based on the operating conditions and the real-time status data of each grid-type energy storage converter. Based on the target reference voltage source, pre-synchronization control is performed on the grid-connected converter in the multi-machine parallel system; When the converter to be connected to the grid meets the synchronization conditions corresponding to the start-up parameters, based on the grid connection timing, the converter to be connected to the grid is connected to the multi-machine parallel system using the output power obtained by the flexible cut-in control algorithm.

2. The method according to claim 1, characterized in that, The step of determining the target reference voltage source based on the operating conditions and the real-time status data of each grid-type energy storage converter includes: If the operating condition is off-grid, then based on the real-time status data of each grid-connected energy storage converter, one of the multiple grid-connected energy storage converters is selected as the main converter, and the output voltage of the main converter is determined as the target reference voltage source. If the operating condition is grid-connected, then the grid voltage is determined as the target reference voltage source.

3. The method according to claim 2, characterized in that, The process of selecting one grid-connected energy storage converter from multiple grid-connected energy storage converters as the main converter based on the real-time status data of each converter, and determining the voltage of the main converter as the target reference voltage source, includes: The real-time status data of each grid-type energy storage converter is normalized. The real-time status data includes state of charge data, DC voltage data, and operating temperature. The normalized real-time status data is substituted into the main converter election algorithm to obtain the election value of each grid-type energy storage converter. The grid-type energy storage converter with the largest election value is determined as the main converter, and the output voltage of the main converter is determined as the target reference voltage source. The main converter election algorithm is as follows: in, For grid-type energy storage converter The election value, For grid-type energy storage converter Normalized state of charge data, For grid-type energy storage converter The normalized DC voltage data, For grid-type energy storage converter The normalized operating temperature, For grid-type energy storage converter Weighting coefficients for state of charge data, For grid-type energy storage converter Weighting coefficients for DC voltage data For grid-type energy storage converter Weighting factor for operating temperature.

4. The method according to claim 3, characterized in that, Under off-grid conditions, the expression for the output voltage of the main converter is: in, The output voltage of the main converter The voltage amplitude of the main converter. The angular frequency of the main converter. To set the initial phase, For time.

5. The method according to claim 1, characterized in that, The starting parameters used to determine synchronization conditions include voltage threshold, frequency threshold, and phase threshold; The converter to be connected to the grid meets the synchronization conditions corresponding to the startup parameters, including: When the deviation between the output voltage amplitude of the converter to be connected to the grid and the output voltage amplitude of the target reference voltage source is less than the voltage threshold, and the deviation between the angular frequency of the converter to be connected to the grid and the angular frequency of the target reference voltage source is less than the frequency threshold, and the deviation between the phase of the converter to be connected to the grid and the phase of the target reference voltage source is less than the phase threshold, it is determined that the converter to be connected to the grid meets the synchronization conditions corresponding to the start-up parameters. Wherein, voltage threshold Δ U th ≤2% U N The frequency threshold Δ ω th ≤0.05Hz, the phase threshold Δ θ th ≤2°.

6. The method according to claim 1, characterized in that, The pre-synchronization control adopts a dual closed-loop control structure; The pre-synchronization control of the converters to be connected to the grid in the multi-machine parallel system based on the target reference voltage source includes: The voltage amplitude error between the converter to be connected to the grid and the target reference voltage source is processed by a PI regulator, and a reference signal for the inner current loop is output to realize outer loop voltage control. In the dq coordinate system, inner-loop current control is achieved by adjusting the active and reactive components of the output current. The phase and frequency information of the target reference voltage source is extracted by a second-order generalized integrator-phase-locked loop model, and the frequency and phase of the converter to be connected to the grid are adjusted in a closed loop to achieve phase synchronization between the converter to be connected to the grid and the target reference voltage source. The second-order generalized integrator-phase-locked loop model is as follows: in, The q-axis component is the input to the phase-locked loop. For the proportional coefficient of the second-order generalized integrator-phase-locked loop, These are the integral coefficients of a second-order generalized integrator-phase-locked loop. Nominal frequency, This is the output angular frequency of the phase-locked loop.

7. The method according to claim 1, characterized in that, The output power obtained by the flexible cut-in control algorithm is realized through a power reference curve; The formula for calculating the power reference curve is as follows: in, The power command at time t. This refers to the rated power of the grid-type energy storage converter. is the time constant.

8. The method according to claim 1, characterized in that, The pre-synchronization control also includes dynamic synchronization compensation; The pre-synchronization control of the grid-connected converters among the multiple grid-connected energy storage converters based on the target reference voltage source includes: If fluctuations or changes are detected in the parameters of the target reference voltage source, all grid-connected energy storage converters will update their synchronization references in real time and re-execute pre-synchronization control.

9. A starting system for a multi-unit parallel grid-connected energy storage converter system, characterized in that, The grid-connected energy storage converter multi-machine parallel system includes multiple grid-connected energy storage converters, and the startup system includes: The detection configuration module is used to detect the operating status of the multi-machine parallel system and configure the startup parameters for judging the synchronization conditions and grid connection timing. The reference voltage source determination module is used to determine the target reference voltage source based on the operating conditions and the real-time status data of each grid-type energy storage converter. The pre-synchronization control module is used to perform pre-synchronization control on the grid-connected converters in the multi-machine parallel system based on the target reference voltage source. The grid connection execution module is used to connect the converter to be connected to the grid into the multi-machine parallel system based on the grid connection timing and the output power obtained by the flexible cut-in control algorithm when the converter to be connected to the grid meets the synchronization conditions corresponding to the start-up parameters.

10. An electronic device, characterized in that, include: At least one processor and memory; The memory and processor are connected via a bus; The memory is used to store one or more programs; When the one or more programs are executed by the at least one processor, the startup method of a multi-machine parallel grid-connected energy storage converter system as described in any one of claims 1 to 8 is implemented.

11. A readable storage medium, characterized in that, It contains an execution program, which, when executed, implements the startup method of a multi-machine parallel grid-connected energy storage converter system as described in any one of claims 1 to 8.

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