Droop control frequency adaptive adjustment method and controller based on droop control

Abstract

The present invention relates to a droop control-based adaptive frequency adjustment method and controller. The method comprises: sampling the system frequency; if the rate of change of the system active power in the current sampling period is less than the corrected system frequency rate of change, then increasing the droop control frequency by an offset value and using it as a droop control frequency set value to perform droop control on the system; if the rate of change of the system active power in the current sampling period is greater than or equal to the corrected system frequency rate of change, then decreasing the droop control frequency by an offset value and using it as a droop control frequency set value to perform droop control on the system. The present invention injects a frequency offset into the droop control to move the system operating point to an equilibrium point, monitors the system power consumption by comparing the active power change rate and the system frequency change rate in real time, appropriately adjusts the injected frequency offset, and ultimately finds the operating point with the lowest system power, thereby achieving the ultimate goal of reducing system power consumption.

Description

Technical Field

[0001] The present invention relates to an electric energy storage system, and in particular to a droop control frequency adaptive adjustment method based on droop control, and also to a controller, a control device for an energy storage converter, a readable storage medium and a computer program product. Background Art

[0002] With rapid economic development, the energy crisis has become increasingly severe. To address this situation, countries have begun to actively implement corresponding countermeasures, and new clean energy sources have received attention from all over the world. Currently, the use of renewable energy to replace traditional fossil fuels for power generation has become a major development direction. Microgrid technology also plays a key role in the utilization of distributed renewable energy. Energy storage devices are the core component of microgrids. Their function is to store excess power output and release it when needed to ensure the normal operation of the entire system. This improves the imbalance between the power consumption of renewable energy generation systems and the power grid, playing a vital role in the sustainable operation of the system.

[0003] Currently, common energy storage converters are categorized as unipolar and bipolar. Bipolar bidirectional converters are typically used. These converters are not only suitable for high-power applications but also address the uncontrollable voltage of energy storage batteries. Currently, droop control is a mainstream control strategy for this structure. During discharge, the active power, system frequency, reactive power, and voltage amplitude of energy storage converters exhibit droop characteristics similar to those of motors. This droop characteristic is mimicked for control. However, droop control primarily focuses on addressing power imbalance, harmonic suppression, and smoothing off-grid and grid-connected switching, leaving room for improvement in reducing converter power consumption. Summary of the Invention

[0004] Based on this, it is necessary to provide a droop control frequency adaptive adjustment method based on droop control that can reduce power consumption.

[0005] A method for adaptively adjusting a droop control frequency based on droop control includes the steps of executing a control strategy, wherein the steps of executing the control strategy include: sampling the system frequency; if the rate of change of the system active power in the current sampling period is less than the rate of change of the system frequency in the current sampling period after magnitude correction, increasing the droop control frequency by a first offset value and using the value as the droop control frequency given value to perform droop control on the system; if the rate of change of the system active power in the current sampling period is greater than or equal to the rate of change of the system frequency in the current sampling period after magnitude correction, reducing the droop control frequency by a second offset value and using the value as the droop control frequency given value to perform droop control on the system.

[0006] The above-mentioned droop control frequency adaptive adjustment method based on droop control injects a frequency offset into the droop control to move the system operating point to a balance point, and monitors the system power consumption by comparing the active power change rate and the system frequency change rate in real time, appropriately adjusts the injected frequency offset, and finally finds the operating point with the minimum system power, thereby achieving the ultimate goal of reducing system power consumption.

[0007] In one embodiment, the absolute values ​​of the first offset value and the second offset value are equal; the rate of change of the system active power in the current sampling period is calculated by subtracting the system active power in the previous sampling period from the system active power in the current sampling period and dividing the result by the sampling time interval, and the system active power in the previous sampling period is where f nom is the previous droop control frequency setting value, Δf is the first offset value, f sys is the system frequency of the previous sampling period, m is the droop coefficient of active power; the system active power of the current sampling period is where f′ nom is the current droop control frequency given value, f′ sys is the system frequency of the current sampling period.

[0008] In one embodiment, the system further includes a step of performing a working status detection after the system is started, and executing the control strategy if the steady-state index is met; the step of performing the working status detection includes: periodically sampling the active power of the system; if the difference between the maximum and minimum values ​​of the active power within a first time period is less than a first threshold, it is determined that the steady-state index is met, and a power mutation detection is performed; the step of the power mutation detection includes: periodically sampling the active power of the system; if the difference between the maximum and minimum values ​​of the active power within a second time period is greater than a second threshold, the execution of the control strategy is terminated, and the working status detection is performed.

[0009] In one embodiment, the system frequency change rate of the current sampling period is calculated by subtracting the system frequency of the previous sampling period from the system frequency of the current sampling period and dividing the result by the sampling time interval.

[0010] In one embodiment, the system is an energy storage converter system, and the energy storage converter system includes an inverter, a filter inductor, and a filter capacitor.

[0011] In one embodiment, the filter inductor and the filter capacitor form an LC filter.

[0012] In one embodiment, the droop control includes: obtaining three-phase voltage and three-phase current on the AC side of the inverter; obtaining the system active power and system reactive power based on the three-phase voltage and three-phase current; performing droop control based on the system active power and the system reactive power to obtain the amplitude and phase angle of the input reference voltage for voltage and current dual closed-loop control; obtaining a sinusoidal modulation signal based on the current of the filter inductor, the input reference voltage and the three-phase voltage; obtaining a sinusoidal pulse width modulation pulse based on the sinusoidal modulation signal to control the on and off of the switching devices in the inverter; wherein the current sampling period droop control frequency given value is used to adjust the frequency of the Pf droop characteristic control of the droop control.

[0013] It is also necessary to provide a controller storing a computer program, wherein when the controller executes the computer program, the steps of the method described in any of the above embodiments are implemented.

[0014] In one embodiment, the controller is a two-stage controller.

[0015] It is also necessary to provide a control device for an energy storage converter, the energy storage converter including an inverter, a filter inductor, and a filter capacitor, the control device including: a power measurement module for obtaining system active power and system reactive power based on three-phase voltage and three-phase current; a droop characteristic control module for performing droop control based on the system active power and system reactive power to obtain the amplitude and phase angle of the input reference voltage for voltage and current dual closed-loop control; a voltage and current dual closed-loop control module for obtaining a sinusoidal modulation signal based on the current of the filter inductor, the input reference voltage, and the three-phase voltage; an SPWM module for obtaining a sinusoidal pulse width modulation pulse based on the sinusoidal modulation signal to control the on and off of the switching devices in the inverter; a secondary controller storing a computer program, wherein the controller implements the steps of the method described in any of the aforementioned embodiments when executing the computer program; wherein the current sampling period droop control frequency set value is used to adjust the frequency of the Pf droop characteristic control of the droop characteristic control module.

[0016] It is also necessary to provide a readable storage medium having a computer program stored thereon, which implements the steps of the method described in any of the above embodiments when the computer program is executed by a processor.

[0017] It is also necessary to provide a computer program product, comprising a computer program, which implements the steps of the method described in any of the above embodiments when the computer program is executed by a processor. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to better describe and illustrate the embodiments and / or examples of the inventions disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered to limit the scope of the disclosed inventions, the presently described embodiments and / or examples, and any of the best modes currently understood for these inventions.

[0019] Figure 1 is an exemplary droop characteristic curve;

[0020] Figure 2 A structural block diagram of a control device for an energy storage converter in one embodiment;

[0021] Figure 3 is a control block diagram of a power measurement module in one embodiment;

[0022] Figure 4 is a control block diagram of a droop characteristic control module in one embodiment;

[0023] Figure 5 is an exemplary droop characteristic curve diagram power analysis;

[0024] Figure 6 is an adaptive power consumption reduction control strategy process of a secondary controller in one embodiment;

[0025] Figure 7 is a flow chart of a method for adaptively adjusting droop control frequency based on droop control in one embodiment;

[0026] Figure 8 is a flow chart of working status detection in one embodiment;

[0027] Figure 9 This is a flow chart of power mutation detection in one embodiment;

[0028] Figure 10 This is a simulation structure block diagram of an energy storage converter in one embodiment;

[0029] Figure 11 yes Figure 10 The three-phase voltage U obtained by simulating the two-stage controller of the present application is shown in the structure configuration abc waveform;

[0030] Figure 12 yes Figure 10 The three-phase current I obtained by simulating the two-stage controller of the present application is shown in the structure configuration abc waveform;

[0031] Figure 13 yes Figure 10 The structure shown is configured with the two-stage controller of this application to simulate the U dc The simulation waveform of

[0032] Figure 14 yes Figure 10 The power output waveform obtained by simulating the two-stage controller of the present application with the structure shown;

[0033] Figure 15 This is the power output waveform of the comparison ratio;

[0034] Figure 16 yes Figure 10 The waveforms of system frequency and phase angle obtained by simulating the two-stage controller of the present application using the structure shown;

[0035] Figure 17 This is the power output waveform before the simulated 3.8KW load is added;

[0036] Figure 18 The power output waveform before and after adding the simulated 3.8KW load;

[0037] Figure 19 The droop control frequency setting value before and after the 3.8KW load is increased;

[0038] Figure 20 It is the status of control strategy, working status detection and power mutation detection. DETAILED DESCRIPTION

[0039] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive disclosure of the present invention.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0041] It should be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it can be directly on, adjacent to, connected to, or coupled to the other element or layer, or there can be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, a first element, component, region, layer, or part discussed below may be represented as a second element, component, region, layer, or part without departing from the teachings of the present invention.

[0042] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0043] To minimize system power loss, this application proposes a two-stage controller model. The control objective is to minimize power loss while maintaining the inverter frequency and bus voltage within acceptable deviations. The bus voltage deviation is controlled within ±5%, while the frequency must comply with national standards for grid connection. References indicate that the frequency range should be between 48.5Hz and 50.5Hz. This two-stage controller primarily achieves this by injecting an offset into the droop function to achieve a balance point.

[0044] First, exemplary droop control will be described.

[0045] According to the power control characteristics of the distributed interface inverter, the droop control equation can be obtained:

[0046] f=f0-m(P-P0) (1)

[0047] V=V0-n(Q-Q0) (2)

[0048] Among them, f, V are the voltage frequency and voltage amplitude output by the inverter, P, Q are the active power and reactive power output by the inverter, f0, V0 are the rated system frequency and rated voltage amplitude, m, n are the droop coefficients of active power and reactive power. According to formulas (1) and (2), the droop characteristic curve can be drawn. Figure 1 .

[0049] According to the droop characteristics reflected by equations (1) and (2), the droop coefficients m and n in traditional droop control can generally be set as:

[0050]

[0051] Among them, P max , Q max is the maximum active power and maximum reactive power allowed to be output, f max 、f min is the maximum and minimum system frequency allowed, V max 、V min is the maximum and minimum voltage allowed. According to the above formula, the controller of the distributed interface inverter circuit can be designed as follows: Figure 2 As shown. Figure 2 The energy storage converter in one embodiment of the present application includes an inverter, a filter inductor L f , filter capacitor C f Filter inductor L f and filter capacitor C f Forming an LC filter. V dc is the equivalent voltage on the DC side of the inverter, i Labc The control device of the energy storage converter includes a power measurement module, a droop characteristic control module, a voltage and current double closed loop control module and an SPWM (sinusoidal pulse width modulation) module. The three-phase voltage u is collected on the AC side of the inverter. oabc and three-phase current i oabc The power measurement module is based on the three-phase voltage u oabc and three-phase current i oabc The system active power P and system reactive power Q are obtained. The droop characteristic control module performs droop control based on the system active power P and system reactive power Q obtained by the power measurement module to obtain the input reference voltage for the voltage and current dual closed-loop control. The amplitude V * and phase angle θ * The voltage and current double closed loop control module is based on the current i of the filter inductor. Labc , input reference voltage And three-phase voltage u oabc Get the sinusoidal modulated signal The SPWM module modulates the signal according to the sinusoidal A sinusoidal pulse width modulation pulse is obtained to control the on and off of a switching device (such as an IGBT) in the inverter.

[0052] For example, the three-phase voltage u collected on the AC side of the inverter oabc and three-phase current i oabc It is an instantaneous value. According to the instantaneous reactive power theory, the instantaneous active power p and instantaneous reactive power q on the transmission line can be obtained as follows:

[0053]

[0054] Among them, u od 、u oq 、i od 、i oq is the dq axis component obtained after the three-phase parameters are transformed. In order to eliminate the high-frequency ripple in the instantaneous power and improve the stability of the output power, the instantaneous power obtained by formula (5) (6) needs to be obtained through a low-pass filter to obtain the average power as the power input signal of the droop characteristic control module:

[0055]

[0056] Among them, ω c is the cutoff frequency of the low-pass filter, ω c / (s+ω c ) is the transfer function of the low-pass filter, P is the average active power output by the inverter, and Q is the average reactive power output by the inverter. Based on the above analysis, we can get Figure 3 The control block diagram of the power measurement module is shown in Figure 2.

[0057] According to equations (1) and (2), the droop control loop can be obtained. Figure 4 The control block diagram of the droop characteristic control module is shown in Figure 2. Based on the average active power P and average reactive power Q obtained by the power measurement module, the amplitude of the input reference voltage V can be obtained by controlling the Pf and QV droop characteristics. * and phase angle θ * , the reference voltage in the synthetic three-phase stationary coordinate After the coordinate dq transformation, it serves as the input reference voltage of the voltage and current dual closed-loop control module.

[0058] The voltage-current dual closed-loop control module uses the inductor current instantaneous feedback control as the inner loop and the capacitor voltage instantaneous feedback control as the outer loop. The inverter performs a dq conversion between the output voltage and a reference voltage signal. The resulting error signal is passed through the PI controller in the outer voltage loop and then fed into the inner current control loop as a reference value. The inverter bridge output filters the inductor current and compares it with the current reference signal. The resulting error signal is then passed through the P controller in the inner current loop, generating a voltage signal that serves as the inverter bridge modulation voltage signal.

[0059] The control device of the energy storage converter of the present application also includes a secondary controller. The frequency offset injected by the secondary controller is the offset injected into f in equation (1). The adaptive power consumption reduction control strategy of the secondary controller is described below:

[0060] First, from the perspective of the power of the energy storage system, we can get the following formula:

[0061] P=P load +P loss (8)

[0062] Among them, P is the total power output by the inverter, P load is the power occupied by the load, P loss is the power loss in the energy storage system. Figure 5 It is reflected in the droop characteristic curve. Figure 5 Medium max is the highest frequency allowed by the system (50.5 Hz in one embodiment of the present application), f min is the lowest frequency allowed by the system (48.5 Hz in one embodiment of the present application), f sys is the current system frequency, Δf step For a given frequency offset, P supplied The total output power of the inverter.

[0063] exist Figure 5 In the figure, the line segment trajectory of the Load Profile is the moving trajectory of the droop characteristic when there is only load in the system. It can be seen that the droop function will be offset in parallel due to the recommended P&O strategy, but no matter how it changes, the frequency of the system will always remain within the set value of 48.5HZ~50.5HZ. In actual control, by adding a frequency offset to the droop control, a certain correction is made to the power loss. When the frequency offset is incorporated into the droop characteristic control module, the system will reach a new steady-state frequency and update the share of load power and loss power. Considering the load power as a constant, if the curvature of the total power changes, it means that the power loss of the system has changed, and by detecting the change in the total power curvature, it is determined whether the power consumption has decreased or increased, which determines the value of the next given frequency offset. In this process, the point closest to the load plane represents the point with the smallest power loss. The above method can be used to find the point with the smallest power loss. The process can be as follows Figure 6 shown.

[0064] Based on the above theoretical foundation, this application proposes a droop control frequency adaptive adjustment method based on droop control, which adaptively adjusts the droop control frequency set value sent to the droop characteristic control module by comparing the active power change rate and the system frequency change rate in real time. Figure 7 FIG. 1 is a flow chart of a method for adaptively adjusting droop control frequency based on droop control in one embodiment, comprising the following steps:

[0065] S110, sampling the system frequency.

[0066] The system frequency is sampled at a fixed sampling period to compare the active power change rate and the system frequency change rate in real time.

[0067] S120 , compare the rate of change ΔP of the system active power in the current sampling period with the rate of change Δfn of the system frequency after magnitude correction (i.e., multiplied by the correction coefficient β). If ΔP<β×Δfn, execute step S132 ; otherwise, execute step S134 .

[0068] The value of β can be set through simulation or based on experience.

[0069] S132: The droop control frequency is increased by the first offset value and used as the droop control frequency given value.

[0070] That is, the droop control frequency given value is increased by the first offset value and then outputted to the droop characteristic control module.

[0071] S134: Reduce the droop control frequency by the second offset value and use it as a given value of the droop control frequency.

[0072] That is, the droop control frequency given value is reduced by the second offset value and then output to the droop characteristic control module.

[0073] S140: Perform droop control on the system according to the droop control frequency given value.

[0074] In one embodiment of the present application, the absolute values ​​of the first offset value and the second offset value are equal, both being Δf. In one embodiment of the present application, Δf is set to 0.1, so the frequency reference value sent to the droop characteristic control module must increase at the beginning, that is, Δfn>0. After each sampling period, whether ΔP increases or decreases can be determined by comparing ΔP with β×Δfn. If ΔP decreases (ΔP<β×Δfn), it means that power consumption is decreasing, and Δf can be continued to be increased to find the minimum power consumption point; conversely, if ΔP increases (ΔP>β×Δfn), it means that power consumption is increasing, and Δf needs to be reduced to continue to find the minimum power consumption point.

[0075] In one embodiment of the present application,

[0076]

[0077]

[0078] Where Δt is the sampling time interval, f nom is the previous droop control frequency setting value, f′ nom is the current droop control frequency given value, f sys is the system frequency of the previous sampling period, f′ sys is the system frequency of the current sampling period, and m is the droop coefficient of active power. In one embodiment of the present application, f′ nom =f nom +Δf.

[0079] The adaptive power consumption reduction control strategy is effective, but because it requires real-time comparison of the active power change rate and the system frequency change rate, the working environment requirements of the control strategy are very demanding. For example, when the system is in the startup state, the input power has been increasing or decreasing for a period of time. At this time, enabling the control strategy will seriously affect the algorithm judgment; in addition, when the system suddenly increases or decreases the load, it will also cause the power to change significantly in a short period of time, affecting the algorithm judgment. In both of the above situations, the control strategy may fail, causing the system to lose control.

[0080] To address the above issues, it is necessary to add a function to determine the stability of the system's working state. During the startup phase, the system's active power is periodically sampled to calculate the difference between the maximum and minimum active power values ​​within the first time period. When the difference reaches the threshold value under the stable working state, the control strategy algorithm is restarted. For sudden load increases, a load mutation detection function is added. This function also periodically samples the system's active power. When the input power change rate changes dramatically, that is, when the difference between the maximum and minimum active power values ​​within the second time period is greater than the preset threshold, the control strategy stops working and locks the droop control frequency setpoint until the system stabilizes before restarting. See [1] for more information. Figure 8 and Figure 9 .

[0081] Figure 10 This is a simulation block diagram of the energy storage converter in one embodiment. In this simulation, the load power is set to 3800W, the system frequency is 50HZ, the AC side line voltage is 380V, and the line impedance is set to: 0.642+j0.1Ω / km. In the simulation, the line length is set to 1 km, the LC filter capacitance is set to 1mF, and the inductance is set to 30mH. The energy storage device battery is set to a normal voltage of 400V. In the power setting, the maximum power of the inverter P max =10KW, the power factor of the inverter is set to about 0.9.

[0082] Figure 11 yes Figure 10 The three-phase voltage U obtained by simulating the two-stage controller of the present application is shown in the structure configuration abc The waveform, Figure 12 yes Figure 10 The three-phase current I obtained by simulating the two-stage controller of the present application is shown in the structure configuration abc The waveform, Figure 13 yes Figure 10 The structure shown is configured with the two-stage controller of this application to simulate the U dc The simulation waveform. Figures 11 to 13 The waveform is basically consistent with the waveform of the traditional droop control simulation model in the comparative example. Figure 14 yes Figure 10 The power output waveform obtained by simulating the two-stage controller of the present application with the structure shown is: Figure 15 It can be seen that the active power of the comparative example is maintained at 5800W under droop control, while that of the embodiment of the present application is reduced to 5400W and maintained there, that is, the power consumption can be reduced by 400W. Figure 16 yes Figure 10 The waveforms of the system frequency and phase angle obtained by simulating the two-stage controller of the present application with the structure shown show that the system frequency is maintained between 49 Hz and 50.5 Hz, which fully complies with the national grid-connected standards.

[0083] The inventors also verified the effectiveness of the working state detection and power mutation detection of the present application through simulation. Figure 17 This is the power output waveform before the load increases. At 1.8 seconds, the secondary controller detects that the working state meets the steady-state indicators and starts to execute the control strategy. Figure 18 The power output waveform before and after the load is increased. Figure 19 It is the given value of droop control frequency before and after load increase. Figure 20 From top to bottom, the control strategy, operating state detection, and power sudden change detection are shown. It can be seen that after a 2.5-second load surge, the control strategy locks the droop control frequency setpoint at 50.45Hz and terminates execution (becoming 0). At this point, power sudden change detection ceases (becoming 0), and operating state detection begins (becoming 1). When the system detects that it has returned to a stable operating state (meeting the steady-state indicator), the control strategy is reactivated to reduce power consumption. This cycle of state changes repeats, and simulations verify the effectiveness of the algorithm improvements.

[0084] It should be understood that, although the various steps in the flowchart of the present application are shown in sequence as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowchart of the present application may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0085] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory or optical memory, etc. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0086] The present application also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps in the method described in any of the above embodiments are implemented.

[0087] The present application also provides a computer device, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the steps in the method described in any of the above embodiments are implemented.

[0088] The present application also provides a computer program product, including a computer program, which implements the steps of the method described in any of the above embodiments when executed by a processor.

[0089] Throughout this specification, references to terms such as "some embodiments," "other embodiments," and "desired embodiments" indicate that a particular feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. Although these terms are used interchangeably throughout this specification, they do not necessarily refer to the same embodiment or example.

[0090] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A droop control frequency adaptive adjustment method based on droop control, characterized in that: The method includes the steps of executing a control strategy, wherein the steps of executing a control strategy include: Sampling the system frequency; If the rate of change of the system active power in the current sampling period is less than the rate of change of the system frequency in the current sampling period after magnitude correction, the droop control frequency is increased by a first offset value and used as a given value of the droop control frequency to perform droop control on the system; if the rate of change of the system active power in the current sampling period is greater than or equal to the rate of change of the system frequency in the current sampling period after magnitude correction, the droop control frequency is reduced by a second offset value and used as a given value of the droop control frequency to perform droop control on the system, and the absolute values ​​of the first offset value and the second offset value are equal; The change rate of the system active power in the current sampling period is calculated by subtracting the system active power in the previous sampling period from the system active power in the current sampling period and dividing the result by the sampling time interval. where f nom is the previous droop control frequency setting value, Δf is the first offset value, f sys is the system frequency of the previous sampling period, m is the droop coefficient of active power; the system active power of the current sampling period is where f′ nom is the current droop control frequency given value, f′ sys is the system frequency of the current sampling period.

2. The droop control frequency adaptive adjustment method based on droop control according to claim 1, characterized in that: It also includes the steps of detecting the working state after the system is started, and executing the control strategy if the steady-state index is met; The step of performing working status detection includes: performing periodic sampling on the active power of the system; If the difference between the maximum and minimum values ​​of the active power within the first time period is less than a first threshold, it is determined that the steady-state indicator is met, and power mutation detection is performed; The step of detecting power mutation includes: performing periodic sampling on the active power of the system; If the difference between the maximum value and the minimum value of the active power within the second time period is greater than a second threshold, the execution of the control strategy is terminated and the working state detection is performed.

3. The droop control frequency adaptive adjustment method based on droop control according to claim 1, characterized in that: The system frequency change rate of the current sampling period is calculated by subtracting the system frequency of the previous sampling period from the system frequency of the current sampling period and dividing the result by the sampling time interval.

4. The method for adaptively adjusting droop control frequency based on droop control according to claim 1, characterized in that: The system is an energy storage converter system, which includes an inverter, a filter inductor and a filter capacitor.

5. The method for adaptively adjusting droop control frequency based on droop control according to claim 4, characterized in that: The droop control includes: Obtaining three-phase voltage and three-phase current on the AC side of the inverter; Obtaining the system active power and the system reactive power according to the three-phase voltage and the three-phase current; Performing droop control according to the system active power and the system reactive power to obtain the amplitude and phase angle of the input reference voltage for voltage and current dual closed-loop control; Obtaining a sinusoidal modulation signal according to the current of the filter inductor, the input reference voltage and the three-phase voltage; Obtaining a sinusoidal pulse width modulation pulse according to the sinusoidal modulation signal to control the on / off of a switching device in the inverter; The current droop control frequency given value is used to adjust the frequency of the Pf droop characteristic control of the droop control.

6. A controller storing a computer program, characterized in that: When the controller executes the computer program, the steps of the method according to any one of claims 1 to 5 are implemented.

7. A control device for an energy storage converter, the energy storage converter comprising an inverter, a filter inductor, and a filter capacitor, characterized in that: The control device comprises: Power measurement module, used to obtain system active power and system reactive power based on three-phase voltage and three-phase current; A droop characteristic control module is used to perform droop control according to the system active power and system reactive power to obtain the amplitude and phase angle of the input reference voltage for voltage and current dual closed-loop control; A voltage-current dual closed-loop control module, configured to obtain a sinusoidal modulation signal according to the current of the filter inductor, the input reference voltage, and the three-phase voltage; An SPWM module, configured to obtain a sinusoidal pulse width modulation pulse according to the sinusoidal modulation signal, and perform on-off control on the switching device in the inverter; a secondary controller storing a computer program, wherein the secondary controller implements the steps of the method according to any one of claims 1 to 4 when executing the computer program; The current droop control frequency given value is used to adjust the frequency of the Pf droop characteristic control of the droop characteristic control module.

8. A readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

9. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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