A current limiting control method for voltage source operation of an energy storage inverter

Abstract

This invention relates to a current limiting control method for an energy storage inverter operating under voltage source mode, comprising the following steps: obtaining the rated voltage and current of the inverter and setting the maximum current that the energy storage inverter can handle; introducing a current limiter to limit the d-axis and q-axis current command values ​​in the dq coordinate system; introducing a phase-locked loop (PLL) to track the q-axis voltage of the distribution network bus, and calculating the frequency and phase angle of the distribution network bus when the q-axis voltage is 0; calculating the actual output frequency and phase angle of the inverter based on the drooping active power-frequency relationship; engaging a phase angle switching mechanism, maintaining the output frequency and phase angle of the energy storage inverter when the current limiter is not triggered, and switching the frequency and phase angle to the frequency and phase angle of the distribution network bus when the current limiter is triggered; after triggering the current limiter, determining whether the output frequency of the energy storage inverter has recovered to within the threshold value, and if so, switching the output frequency and phase angle of the inverter back to the actual output frequency and phase angle.

Description

Technical Field

[0001] This invention relates to a current limiting control method for an energy storage inverter operating under voltage source mode, belonging to the field of control technology for energy storage voltage source inverters. Background Technology

[0002] With the continuous advancement of energy transition and smart grid technology, the problems arising from the increasing penetration rate of new energy sources cannot be ignored. At the same time, new energy sources are characterized by randomness, volatility, and intermittency, which necessitates the support of energy storage technology.

[0003] In recent years, with the advancement of energy conservation, emission reduction, and environmental protection requirements, the State Grid Corporation of China has begun to advocate the construction of a new power system based on new energy sources. This indicates that the proportion of distributed generation systems with new energy sources as the main power generation source will increase year by year. Therefore, the stable operation of inverters is crucial to the stable operation of the entire system.

[0004] When high-power loads are frequently switched on and off on the load side, significant fluctuations in line current can easily occur. These line current fluctuations directly affect the normal operating conditions of energy storage voltage source inverters. Energy storage inverters are typically considered voltage sources with internal resistance, and their output current and output power are affected by the load. When a sudden increase in high-power load occurs, the inverter needs to output a surge in current during the transient process. This transient inrush current can easily damage the switching devices in the inverter, affecting the normal operation of the inverter under steady-state conditions.

[0005] Without protective measures, once overload conditions are entered, the inverter will continue to output at maximum power and maximum current for a long time and will not be able to return to steady-state operation. Working in non-rated conditions for a long time can easily cause the inverter's switching devices to break down, resulting in the loss of inverter and rectification capabilities. Summary of the Invention

[0006] To address the issue of overcurrent phenomena caused by inverter overload in existing technologies, which can adversely affect the inverter, this invention proposes a current-limiting control technology for voltage-source operation of energy storage inverters. This technology limits the current command value under overload conditions, ensuring a margin for reactive power fluctuations during transient processes while still providing a certain voltage support capability. Simultaneously, it ensures the system outputs maximum current only during transients, and when it returns to steady state, it outputs rated current and rated power, operating stably under rated conditions and guaranteeing the inverter's lifespan.

[0007] The technical solution of the present invention is as follows:

[0008] On one hand, the present invention provides a current limiting control method for an energy storage inverter operating under voltage source mode, comprising the following steps:

[0009] Obtain the rated voltage and rated current of the energy storage inverter, and set the maximum current that the energy storage inverter can withstand based on the rated current;

[0010] When the load increases during voltage source operation of the energy storage inverter, a current limiter is introduced into the current loop to limit the d-axis and q-axis current command values ​​in the dq coordinate system. The limit value and the d-axis and q-axis current command value are set according to the maximum current that the energy storage inverter can handle.

[0011] A phase-locked loop (PLL) is introduced to collect the voltage of the distribution network bus. The q-axis voltage of the distribution network bus is tracked through dq transformation and PI controller. When the q-axis voltage of the distribution network bus is 0, the frequency and phase angle of the distribution network bus are calculated.

[0012] The actual output frequency and phase angle of the energy storage inverter are calculated based on the drooping active power-frequency relationship when the energy storage inverter is voltage sourced.

[0013] When the phase angle switching stage is engaged, if the actual output current of the energy storage inverter does not trigger the current limiter, the frequency and phase angle of the energy storage inverter output are kept at the actual output frequency and phase angle. When the actual output current of the energy storage inverter triggers the current limiter, the frequency and phase angle of the energy storage inverter output are switched to the frequency and phase angle of the distribution network bus when the q-axis voltage of the distribution network bus is 0.

[0014] When the current limiter is triggered, the system recalculates and determines whether the output frequency of the energy storage inverter has recovered to the set threshold. If it has, the frequency and phase angle of the inverter output are switched back to the actual output frequency and phase angle of the energy storage inverter.

[0015] In a preferred embodiment, the maximum current that the energy storage inverter can handle is set to 1.1 times the rated current.

[0016] In a preferred embodiment, the step of setting the limiting amplitude based on the maximum current that the energy storage inverter can handle, and the amplitude of the d-axis and q-axis current command values, specifically are as follows:

[0017] The limiting amplitude is set to be equal to the maximum current that the energy storage inverter can handle;

[0018] The amplitude of the d-axis current command value is set to I. refdmax =0.95*I M The q-axis current command amplitude is set to

[0019] The specific d-axis and q-axis current limiting settings are as follows:

[0020]

[0021] When I ref_qWhen the value is greater than 0, the q-axis current command amplitude is set as follows:

[0022]

[0023] When I ref_q When <0, the q-axis current command amplitude is set as follows:

[0024]

[0025] Among them, I M This is the maximum current that the energy storage inverter can handle. These are the d-axis and q-axis current command values ​​for the inverter after current limiting; I ref_d I ref_q This is the current command value output by the actual voltage loop of the inverter.

[0026] In a preferred embodiment, in the step of recalculating and determining whether the output frequency of the energy storage inverter has recovered to within the set threshold, the set threshold is specifically 50Hz ± 0.2Hz.

[0027] On the other hand, the present invention also provides a current limiting control system for an energy storage inverter operating under voltage source mode, comprising:

[0028] The initial parameter module is used to obtain the rated voltage and rated current of the energy storage inverter, and to set the maximum current that the energy storage inverter can withstand based on the rated current;

[0029] The current limiter module is used to introduce a current limiter into the current loop when the load increases during the voltage source operation of the energy storage inverter. The current limiter limits the d-axis and q-axis current command values ​​in the dq coordinate system. The limit value and the d-axis and q-axis current command value are set according to the maximum current that the energy storage inverter can handle.

[0030] The distribution network bus frequency and phase angle calculation module is used to introduce a phase-locked loop (PLL) link to collect the distribution network bus voltage, track the distribution network bus q-axis voltage through dq transformation and PI controller, and calculate the distribution network bus frequency and phase angle when the distribution network bus q-axis voltage is 0.

[0031] The inverter actual output frequency and phase angle calculation module calculates the actual output frequency and phase angle of the energy storage inverter based on the droop active power-frequency relationship when the energy storage inverter is voltage sourced.

[0032] The phase angle switching module is activated in the phase angle switching stage. When the actual output current of the energy storage inverter does not trigger the current limiter, the frequency and phase angle of the energy storage inverter output are kept at the actual output frequency and phase angle. When the actual output current of the energy storage inverter triggers the current limiter, the frequency and phase angle of the energy storage inverter output are switched to the frequency and phase angle of the distribution network bus when the q-axis voltage of the distribution network bus is 0.

[0033] The phase angle recovery module is used to recalculate and determine whether the output frequency of the energy storage inverter has recovered to the set threshold after the current limiter is triggered. If it has recovered, the frequency and phase angle of the inverter output are switched back to the actual output frequency and phase angle of the energy storage inverter.

[0034] In a preferred embodiment, the maximum current that the energy storage inverter can handle is set to 1.1 times the rated current.

[0035] In a preferred embodiment, the current limiter module sets the limit value based on the maximum current that the energy storage inverter can handle, and the d-axis and q-axis current command values ​​are specifically as follows:

[0036] The limiting amplitude is set to be equal to the maximum current that the energy storage inverter can handle;

[0037] The amplitude of the d-axis current command value is set to I. refdmax =0.95*I M The q-axis current command amplitude is set to

[0038] The specific d-axis and q-axis current limiting settings are as follows:

[0039]

[0040] When I ref_q When the value is greater than 0, the q-axis current command amplitude is set as follows:

[0041]

[0042] When I ref_q When <0, the q-axis current command amplitude is set as follows:

[0043]

[0044] Among them, I M This is the maximum current that the energy storage inverter can handle. These are the d-axis and q-axis current command values ​​for the inverter after current limiting; I ref_d I ref_q This is the current command value output by the actual voltage loop of the inverter.

[0045] In a preferred embodiment, the set threshold in the phase angle recovery module is specifically 50Hz ± 0.2Hz.

[0046] In another aspect, the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement a current limiting control method for voltage source operation of an energy storage inverter as described in any embodiment of the present invention.

[0047] In another aspect, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the current limiting control method for voltage source operation of an energy storage inverter as described in any embodiment of the present invention.

[0048] The present invention has the following beneficial effects:

[0049] This invention limits the d-axis and q-axis components of the current command value under overload conditions, ensuring that the reactive current remains within a certain fluctuation range. This guarantees a margin for reactive power fluctuations during transient processes while still providing a certain voltage support capability, effectively improving the service life of the energy storage voltage source inverter and ensuring system stability under different load fluctuations. Simultaneously, by engaging the phase angle switching module, the phase angle of the inverter output is the same as the voltage phase angle at the distribution network bus during transient overcurrent. After entering steady state, the phase angle in the original droop-Pf relationship is used again. By employing this switching module, the system outputs maximum current only during transients. When it returns to steady state, i.e., the inverter output frequency is within the threshold range, the inverter outputs rated current and rated power, operating stably under rated conditions. This mitigates the transient overcurrent phenomenon, effectively improving the service life of the energy storage voltage source inverter and ensuring system stability under different load fluctuations. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the method flow of Embodiment 1 of the present invention;

[0051] Figure 2 The algorithm flow for using a current limiter and phase angle switching stage in this embodiment of the invention is as follows;

[0052] Figure 3 This is an example diagram of an energy storage grid-connected structure in an embodiment of the present invention;

[0053] Figure 4a This is a comparison of the single-phase output current in the simulation results of the system without current limiting measures and the system with a single current limiter being applied to the load for the first time in the embodiment.

[0054] Figure 4bThe figure shows a comparison of the three-phase output current in the simulation results of the system without current limiting measures and the system with a single current limiter being connected to the load for the first time.

[0055] Figure 4c The above is a schematic diagram of the voltage and current waveforms at the distribution network bus in the simulation results of the system without current limiting measures and the system with a single current limiter being put into operation for the first time.

[0056] Figure 5a This is a comparison chart of the single-phase output current in the simulation results of the system without current limiting measures and the system with a current limiter introduced alone when the load is applied for the second time.

[0057] Figure 5b The figure shows a comparison of the three-phase output current in the simulation results of the system without current limiting measures and the system with a current limiter introduced alone when the load is applied for the second time.

[0058] Figure 5c The above is a schematic diagram of the voltage and current waveforms at the distribution network bus in the simulation results of the system without current limiting measures and with a single current limiter applied to the load for the second time in the embodiment.

[0059] Figure 6a The figure shows a comparison of the three-phase output current in the simulation results of the first load input of the system in the embodiment without current limiting measures and with the current limiting control method of the energy storage voltage source inverter.

[0060] Figure 6b The figure shows a comparison of the three-phase output current in the simulation results of the first load input of the system in the embodiment without current limiting measures and with the current limiting control method of the energy storage voltage source inverter.

[0061] Figure 6c This is a schematic diagram of the voltage and current waveforms at the distribution network bus in the simulation results of the first load input of the system without current limiting measures and the current limiting control method of the energy storage voltage source inverter in the embodiment.

[0062] Figure 7a This is a comparison of the three-phase output current in the simulation results of the second load input of the system in the embodiment without current limiting measures and with the current limiting control method of the energy storage voltage source inverter.

[0063] Figure 7b This is a comparison of the three-phase output current in the simulation results of the second load input of the system in the embodiment without current limiting measures and with the current limiting control method of the energy storage voltage source inverter.

[0064] Figure 7c This is a schematic diagram of the voltage and current waveforms at the distribution network bus in the simulation results of the second load input of the system without current limiting measures and the current limiting control method of the energy storage voltage source inverter in the embodiment.

[0065] Figure 8 This is a system control block diagram provided in Embodiment 2 of the present invention. Detailed Implementation

[0066] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0067] It should be understood that the step numbers used in the text are for ease of description only and are not intended to limit the order in which the steps are performed.

[0068] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0069] The terms “comprising” and “including” indicate the presence of the described feature, whole, step, operation, element and / or component, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0070] The term “and / or” refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes these combinations.

[0071] Example 1:

[0072] See Figure 1 and Figure 2 This embodiment provides a current limiting control method for energy storage inverters operating under voltage source conditions, applicable to grid-connected energy storage. Figure 3 The diagram shows a block diagram of a grid-connected energy storage system. The distributed energy storage voltage source inverter system includes an energy storage battery, a DC / DC converter, an inverter, and a filter circuit. The energy storage battery is connected to the DC side of the inverter via the DC / DC converter, and the filter circuit is connected to the AC side of the inverter. The system is connected to the load through line impedance and then connected to the power grid through a public grid connection point via line impedance. This method specifically includes the following steps:

[0073] S100, Obtain the rated voltage and rated current of the energy storage inverter, denoted as I. n U n The maximum current I that the energy storage inverter can handle is set based on the rated current. M In this embodiment, IM Set to 1.1*In.

[0074] S200. When the load increases during the voltage source operation of the energy storage inverter, a current limiter is introduced into the current loop to limit the current command values ​​of the d and q axes in the dq coordinate system. The limit value and the current command value of the d and q axes are set according to the maximum current that the energy storage inverter can bear.

[0075] In this embodiment, the limiting amplitude is set to the maximum current I that the energy storage inverter can handle. M equal;

[0076] The amplitude of the d-axis current command value is set to I. refdmax =0.95*I M The q-axis current command amplitude is set to

[0077] The specific d-axis and q-axis current limiting settings are as follows:

[0078]

[0079] When I ref_q When the value is greater than 0, the q-axis current command amplitude is set as follows:

[0080]

[0081] When I ref_q When <0, the q-axis current command amplitude is set as follows:

[0082]

[0083] Among them, I M This is the maximum current that the energy storage inverter can handle. These are the d-axis and q-axis current command values ​​for the inverter after current limiting; I ref_d I ref_q This is the current command value output by the actual voltage loop of the inverter.

[0084] Based on step S200, when a current limiter is introduced alone for an extended period, it can cause voltage loop failure, leading to fluctuations in the inverter output voltage and consequently, significant fluctuations in the inverter's output active power, resulting in a continuous shift in the angular frequency. Therefore, when the load increases, current limiting is triggered simultaneously, and a control mode with a switching phase angle command is activated. When the current does not reach the limiting command, the phase angle of the inverter coordinate transformation is the phase angle calculated using the drooping Pf relationship. When the current triggers the limiting command, the phase angle of the inverter coordinate transformation is the phase angle obtained through phase-locked loop (PLL) with the distribution network bus voltage. Based on this, this embodiment also includes the following steps:

[0085] S300: A phase-locked loop (PLL) is introduced to acquire the distribution network bus voltage. The q-axis voltage of the distribution network bus is tracked via dq conversion and a PI controller. When the q-axis voltage of the distribution network bus is 0, the distribution network bus frequency f is calculated. pcc With phase angle θ pcc ;

[0086] S400. The actual output frequency f of the energy storage inverter is calculated based on the drooping active power-frequency relationship when the energy storage inverter is voltage sourced. ps and phase angle θ ps ;

[0087] S500, when the phase angle switching stage is engaged, if the actual output current of the energy storage inverter does not trigger the current limiter, the frequency of the energy storage inverter output will maintain the actual output frequency f with respect to the phase angle. ps and phase angle θ ps When the actual output current of the energy storage inverter triggers the current limiter, the frequency and phase angle of the energy storage inverter output are switched to the distribution bus frequency f when the q-axis voltage of the distribution bus is 0. pcc With phase angle θ pcc .

[0088]

[0089] Where, θ inv This refers to the actual output phase angle of the energy storage voltage source inverter.

[0090] S600. After the current limiter is triggered, the output frequency f of the energy storage inverter, calculated using the drooping active power-frequency relationship, is recalculated and determined. ps Whether the system has recovered to within the set threshold is determined. In this embodiment, the set threshold is specifically 50Hz ± 0.2Hz. If the system has recovered to within the threshold, it indicates that the system has successfully passed the transient process of load switching. The inverter output frequency and phase angle are then switched back to the inverter output frequency f calculated from the original drooping active power-frequency relationship. ps With phase angle θ ps .

[0091]

[0092] To verify the effectiveness and accuracy of the current-limiting control method for voltage-source operation of the energy storage inverter proposed in this embodiment, simulation verification was performed on the PLECS simulation platform. The simulation background was set as a single-unit grid-connected energy storage inverter based on droop control, wherein the rated active power Pn of the energy storage inverter was set to 30kW, the rated reactive power Qn to 1kvar, the rated current In to 45A, and the rated voltage Un to 220V. To protect the switching devices in the inverter, the maximum current that the inverter can withstand was set to IM = 1.1 * In = 50A.

[0093] Operating Condition 1: Without any restrictions, observe the inverter output during load fluctuations and compare it with the current limiting control method introduced later in this embodiment. The system initially bears a load Z. load1 The load is a constant resistance load, primarily consisting of a resistor and an inductor, with a resistance of 10Ω and an inductance of 2μH. A sudden load Z is applied at 0.5s. load2 The resistor has a resistance of 5Ω and the inductor has a resistance of 4μH. A sudden load Z is applied at 1.2s. load3 The resistor has a resistance of 2Ω and the inductor has a resistance of 4μH. The system assumes an initial load Z. load1 Under these circumstances, observe the inverter's output voltage and current to determine its operating condition. When the load Z is added for the first time... load2 During this time, observe the inverter's output voltage and current, especially the transient current fluctuations, to see if they exceed the inverter's maximum current capacity (IM). When the load Z is added a second time... load3 At that time, observe the output voltage and current of the inverter, focusing on the transient current fluctuations, and compare and analyze them with the subsequent operating condition two.

[0094] Operating Condition 2: A single current limiter is used for current limiting control. The inverter output is observed during load fluctuations and compared with the condition without current limiting. The initial system load is Z. load1 The load is a constant resistance load, primarily consisting of a resistor and an inductor, with a resistance of 10Ω and an inductance of 2μH. A sudden load Z is applied at 0.5s. load2 The resistor has a resistance of 5Ω and the inductor has a resistance of 4μH. A sudden load Z is applied at 1.2s. load3 The resistor has a resistance of 2Ω and the inductor has a resistance of 4μH. The system assumes an initial load Z. load1 Under these circumstances, observe the inverter's output voltage and current to determine its operating condition. When the load Z is added for the first time... load2 During this period, observe the inverter output voltage and current, and assess the impact of only introducing a current limiter on the transient current of the inverter output. Compare this observation with that of operating condition one, and analyze whether the fluctuation of the transient current has been mitigated. When the load Z is added for the second time...load3 At the same time, observe the output voltage and current of the inverter, and pay attention to the impact on the transient current of the inverter output. Also, observe the angular frequency waveform of the inverter output at this time and compare it with that of operating condition one to analyze and compare the fluctuation of the transient current.

[0095] Operating Condition 3: Introducing current-limiting control technology for the energy storage voltage source inverter, observing the inverter's output under load fluctuations, and comparing it with the condition without current limiting and with only a current limiter. The initial system load is Z. load1 The load is a constant resistance load, primarily consisting of a resistor and an inductor, with a resistance of 10Ω and an inductance of 2μH. A sudden load Z is applied at 0.5s. load2 The resistor has a resistance of 5Ω and the inductor has a resistance of 4μH. A sudden load Z is applied at 1.2s. load3 The resistor has a resistance of 2Ω and the inductor has a resistance of 4μH. When the load Z is first added... load2 During this period, observe the inverter output voltage and current, and assess the impact of the current-limiting control technology (introduced as a voltage source for the energy storage inverter) on the transient current output of the inverter. Compare this data with operating conditions one and two, and analyze whether the fluctuations in transient current have been mitigated. When the load Z is added for the second time... load3 At the same time, observe the inverter output voltage and current, and pay attention to the impact on the transient current output of the inverter. Also observe the inverter output phase angle waveform at this time and compare it with operating conditions one and two to analyze and compare the fluctuation of transient current.

[0096] The simulation results in Figures 4, 5, 6, and 7 correspond to the comparison of three operating conditions, proving the accuracy and reliability of the current limiting control technology for voltage source operation of the energy storage inverter.

[0097] Figure 4 shows the simulation results of the system without current limiting measures and with a single current limiter for load fluctuations, i.e., the first load is applied at 0.5s, for comparison and analysis.

[0098] in Figure 4a This is a comparison chart of single-phase output current. Figure 4b This is a comparison chart of the three-phase output current. Figure 4cThe figures show the voltage and current waveforms at the distribution network bus. When only a current limiter is used for limiting the load, the first load active power fluctuation ranges from 14kW to 32kW. For this simulated inverter, this just exceeds the inverter's rated power of 30kW. Therefore, the current limiting effect is normal, and the output current does not fluctuate significantly. However, the distribution network bus voltage fluctuates noticeably, exhibiting a long buffer time. Comparing this figure with Figure 5 shows the simulation results for the second load fluctuation—without current limiting measures and with only a current limiter—comparing the results when the load is applied for the second time at 1.2s.

[0099] in Figure 5a This is a comparison chart of single-phase output current. Figure 5b This is a comparison chart of the three-phase output current. Figure 5c The voltage and current waveforms at the distribution network bus are shown. At this point, the second load active power fluctuation is between 32kW and 41kW. For this simulated inverter setup, this load fluctuation significantly exceeds the inverter's rated power of 30kW. Therefore, when using a separate current limiter, according to... Figure 5c As can be seen, prolonged use of a single current limiter leads to significant voltage fluctuations on the distribution network bus, noticeable voltage loop detachment, and a continuous shift in the output angular frequency, resulting in instability. Therefore, the advantages of the method of this invention can be verified by comparing Figures 6 and 7.

[0100] Figure 6 shows the simulation results of the system without current limiting measures and the current limiting control technology of the energy storage voltage source inverter under load fluctuations, i.e., the first load is applied at 0.5s, for comparison and analysis. Figure 6a This is a comparison chart of single-phase output current. Figure 6b This is a comparison chart of the three-phase output current. Figure 6c The waveforms represent the voltage and current at the distribution network bus. When the control method of this invention is introduced, its suppression and fluctuation effects are similar to those of introducing a current limiter alone during the initial small-range load fluctuation. At this time, the current limiting effect is normal, the output current does not fluctuate significantly, the voltage fluctuation of the distribution network bus is small, and the buffer time is shorter than that of introducing a current limiter alone.

[0101] Figure 7 shows the simulation results of the system without current limiting measures and the current limiting control technology of the energy storage voltage source inverter under load fluctuations, specifically the comparison and analysis of the second load application at 1.2s. Figure 7a This is a comparison chart of single-phase output current. Figure 7b This is a comparison chart of the three-phase output current. Figure 7cThe voltage and current waveforms at the distribution network bus are shown. By observing the detailed comparison between Figure 5 and Figure 7, the advantages of adopting the current limiting control technology of this invention can be further seen. At this time, the second load fluctuates over a wide range, and its suppression effect is better than that of introducing a current limiter alone. There is no instability phenomenon, and the voltage fluctuation of the distribution network bus is not obvious. The buffer time is short and the limiting effect is obvious.

[0102] The above simulation verification proves the correctness and reliability of the present invention.

[0103] In summary, under the control strategy described in this invention, the d-axis and q-axis components of the current command value are limited according to the overload condition, ensuring that the reactive current is maintained within a certain fluctuation range. This ensures the reactive power fluctuation margin during transient processes, while still providing a certain voltage support capability. This effectively improves the service life of the energy storage voltage source inverter and ensures the stability of the system under different load fluctuations.

[0104] Meanwhile, by engaging the phase angle switching module, the phase angle of the inverter output is the same as the voltage phase angle at the distribution network bus during transient overcurrent. After entering steady state, the phase angle in the original droop Pf relationship is used again. By using this switching module, the system outputs the maximum current only during transients. When it returns to steady state, i.e., the inverter output frequency is within the threshold range, the inverter outputs rated current and rated power, and operates stably under rated conditions. This improves the transient overcurrent phenomenon, effectively increases the service life of the energy storage voltage source inverter, and ensures the stability of the system under different load fluctuations.

[0105] Example 2:

[0106] See Figure 8 This embodiment provides a current limiting control system for an energy storage inverter operating under voltage source mode, including:

[0107] The initial parameter module is used to obtain the rated voltage and rated current of the energy storage inverter, and to set the maximum current that the energy storage inverter can withstand based on the rated current; this module is used to implement the function of step S100 in Embodiment 1, which will not be described in detail here.

[0108] The current limiter introduction module is used to introduce a current limiter into the current loop when the load increases during the voltage source operation of the energy storage inverter. It limits the current command values ​​of the d and q axes in the dq coordinate system, and sets the limit amplitude and the amplitude of the d and q axis current command values ​​according to the maximum current that the energy storage inverter can handle. This module is used to implement the function of step S200 in Embodiment 1, which will not be described in detail here.

[0109] The distribution network bus frequency and phase angle calculation module is used to introduce a phase-locked loop (PLL) link, collect the distribution network bus voltage, track the distribution network bus q-axis voltage through dq transformation and PI controller, and calculate the distribution network bus frequency and phase angle when the distribution network bus q-axis voltage is 0. This module is used to implement the function of step S300 in Example 1, which will not be described in detail here.

[0110] The inverter actual output frequency and phase angle calculation module calculates the actual output frequency and phase angle of the energy storage inverter based on the drooping active power-frequency relationship when the energy storage inverter is voltage sourced; this module is used to implement the function of step S400 in Embodiment 1, and will not be described in detail here.

[0111] The phase angle switching module, when engaged in the phase angle switching stage, keeps the frequency and phase angle of the energy storage inverter output at the actual output frequency and phase angle when the actual output current of the energy storage inverter does not trigger the current limiter. When the actual output current of the energy storage inverter triggers the current limiter, it switches the frequency and phase angle of the energy storage inverter output to the frequency and phase angle of the distribution network bus when the q-axis voltage of the distribution network bus is 0. This module is used to implement the function of step S500 in embodiment one, and will not be described in detail here.

[0112] The phase angle recovery module is used to recalculate and determine whether the output frequency of the energy storage inverter has recovered to the set threshold after the current limiter is triggered. If it has recovered, the output frequency and phase angle of the inverter are switched back to the actual output frequency and phase angle of the energy storage inverter. This module is used to implement the function of step S600 in Embodiment 1, which will not be described in detail here.

[0113] The symbols in the diagram represent: P and Q: the active and reactive power required by the load.

[0114] P * Q * Rated active power and rated reactive power of the energy storage voltage source inverter.

[0115] In a preferred embodiment of this invention, the maximum current that the energy storage inverter can handle is set to 1.1 times the rated current.

[0116] In a preferred embodiment of this invention, the current limiter module sets the limit value based on the maximum current that the energy storage inverter can handle, and the d-axis and q-axis current command values ​​are specifically as follows:

[0117] The limiting amplitude is set to be equal to the maximum current that the energy storage inverter can handle;

[0118] The amplitude of the d-axis current command value is set to I. refdmax =0.95*I M The q-axis current command amplitude is set to

[0119] The specific d-axis and q-axis current limiting settings are as follows:

[0120]

[0121] When I ref_q When the value is greater than 0, the q-axis current command amplitude is set as follows:

[0122]

[0123] When I ref_q When <0, the q-axis current command amplitude is set as follows:

[0124]

[0125] Among them, I M This is the maximum current that the energy storage inverter can handle. These are the d-axis and q-axis current command values ​​for the inverter after current limiting; I ref_d I ref_q This is the current command value output by the actual voltage loop of the inverter.

[0126] In a preferred embodiment of this example, the set threshold in the phase angle recovery module is specifically 50Hz ± 0.2Hz.

[0127] Example 3:

[0128] This embodiment proposes an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements a current limiting control method for voltage source operation of an energy storage inverter as described in any embodiment of the present invention.

[0129] Example 4:

[0130] This embodiment proposes a computer-readable storage medium storing a computer program that, when executed by a processor, implements a current-limiting control method for voltage-sourced operation of an energy storage inverter as described in any embodiment of the present invention.

[0131] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, A and B simultaneously, or B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0132] Those skilled in the art will recognize that the units and algorithm steps described in the embodiments disclosed herein can be implemented using electronic hardware, computer software, or a combination of electronic hardware and software. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0133] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0134] In the several embodiments provided in this application, any function, if implemented as a software functional unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0135] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A current limiting control method for an energy storage inverter operating in voltage source mode, characterized by, Includes the following steps: Obtain the rated voltage and rated current of the energy storage inverter, and set the maximum current that the energy storage inverter can withstand based on the rated current; When the load increases during voltage source operation of the energy storage inverter, a current limiter is introduced into the current loop to limit the d-axis and q-axis current command values ​​in the dq coordinate system. The limit value and the d-axis and q-axis current command value are set according to the maximum current that the energy storage inverter can handle. A phase-locked loop (PLL) is introduced to collect the voltage of the distribution network bus. The q-axis voltage of the distribution network bus is tracked through dq transformation and PI controller. When the q-axis voltage of the distribution network bus is 0, the frequency and phase angle of the distribution network bus are calculated. The actual output frequency and phase angle of the energy storage inverter are calculated based on the drooping active power-frequency relationship when the energy storage inverter is voltage sourced. When the phase angle switching stage is engaged, if the actual output current of the energy storage inverter does not trigger the current limiter, the frequency and phase angle of the energy storage inverter output are kept at the actual output frequency and phase angle. When the actual output current of the energy storage inverter triggers the current limiter, the frequency and phase angle of the energy storage inverter output are switched to the frequency and phase angle of the distribution network bus when the q-axis voltage of the distribution network bus is 0. When the current limiter is triggered, the system recalculates and determines whether the output frequency of the energy storage inverter has recovered to the set threshold. If it has, the inverter's output frequency and phase angle are switched back to the actual output frequency and phase angle of the energy storage inverter. The specific steps for setting the limiting amplitude based on the maximum current that the energy storage inverter can handle, and the amplitude of the d-axis and q-axis current command values ​​are as follows: The limiting amplitude is set to be equal to the maximum current that the energy storage inverter can handle; The amplitude of the d-axis current command value is set to The q-axis current command amplitude is set to ; The specific d-axis and q-axis current limiting settings are as follows: ； when At that time, the q-axis current command amplitude is set as follows: ； when At that time, the q-axis current command amplitude is set as follows: ； in, This is the maximum current that the energy storage inverter can handle. These are the commanded values ​​for the d-axis and q-axis currents of the inverter after current limiting; This is the current command value output by the actual voltage loop of the inverter; In the step of recalculating and determining whether the output frequency of the energy storage inverter has recovered to within the set threshold, the set threshold is specifically 50Hz ± 0.2Hz.

2. The current limiting control method for an energy storage inverter operating under voltage source mode according to claim 1, characterized in that: The maximum current that the energy storage inverter can handle is set to 1.1 times the rated current.

3. A current-limiting control system for an energy storage inverter operating under voltage source mode, characterized in that, include: The initial parameter module is used to obtain the rated voltage and rated current of the energy storage inverter, and to set the maximum current that the energy storage inverter can withstand based on the rated current; The current limiter module is used to introduce a current limiter into the current loop when the load increases during the voltage source operation of the energy storage inverter. The current limiter limits the d-axis and q-axis current command values ​​in the dq coordinate system. The limit value and the d-axis and q-axis current command value are set according to the maximum current that the energy storage inverter can handle. The distribution network bus frequency and phase angle calculation module is used to introduce a phase-locked loop (PLL) link to collect the distribution network bus voltage, track the distribution network bus q-axis voltage through dq transformation and PI controller, and calculate the distribution network bus frequency and phase angle when the distribution network bus q-axis voltage is 0. The inverter actual output frequency and phase angle calculation module calculates the actual output frequency and phase angle of the energy storage inverter based on the droop active power-frequency relationship when the energy storage inverter is voltage sourced. The phase angle switching module is activated in the phase angle switching stage. When the actual output current of the energy storage inverter does not trigger the current limiter, the frequency and phase angle of the energy storage inverter output are kept at the actual output frequency and phase angle. When the actual output current of the energy storage inverter triggers the current limiter, the frequency and phase angle of the energy storage inverter output are switched to the frequency and phase angle of the distribution network bus when the q-axis voltage of the distribution network bus is 0. The phase angle recovery module is used to recalculate and determine whether the output frequency of the energy storage inverter has recovered to the set threshold after the current limiter is triggered. If it has recovered, the frequency and phase angle of the inverter output at this time will be switched back to the actual output frequency and phase angle of the energy storage inverter. In the current limiter module, the limit value is set according to the maximum current that the energy storage inverter can handle, and the specific values ​​of the d-axis and q-axis current command values ​​are as follows: The limiting amplitude is set to be equal to the maximum current that the energy storage inverter can handle; The amplitude of the d-axis current command value is set to The q-axis current command amplitude is set to ; The specific d-axis and q-axis current limiting settings are as follows: ； when At that time, the q-axis current command amplitude is set as follows: ； when At that time, the q-axis current command amplitude is set as follows: ； in, This is the maximum current that the energy storage inverter can handle. These are the commanded values ​​for the d-axis and q-axis currents of the inverter after current limiting; This is the current command value output by the actual voltage loop of the inverter; In the phase angle recovery module, the set threshold is specifically 50Hz ± 0.2Hz.

4. The current limiting control system for a voltage-sourced energy storage inverter according to claim 3, characterized in that: The maximum current that the energy storage inverter can handle is set to 1.1 times the rated current.

5. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the current limiting control method for the voltage source operation of the energy storage inverter as described in any one of claims 1 to 2.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by the processor, the program implements the current limiting control method for voltage source operation of the energy storage inverter as described in any one of claims 1 to 2.

Images