A network-constructing type energy storage converter control method, device and system based on frequency disturbance observation

Abstract

The application discloses a network-constructing energy storage converter control method, device and system based on frequency disturbance observation, and belongs to the technical field of power electronics control. The system collects the output voltage of the converter AC side, the grid-connected current and the filter inductance current, calculates the actual active power and reactive power, and generates the active power deviation and the angular frequency deviation; the extended state observer is used to estimate the frequency-related total disturbance acting on the comprehensive influence of the grid frequency disturbance and the grid strength change according to the above deviation signals; the frequency compensation quantity is generated according to the disturbance estimation quantity and is superposed with the basic angular frequency deviation and the rated angular frequency to obtain the output angular frequency and the synchronization angle; and then the operation of the converter is modulated and driven through the reactive-voltage control and the voltage-current double closed loop control. The application does not need to take the grid angular frequency as the direct input of the observer, and can improve the frequency disturbance adaptability and the power synchronization stability of the network-constructing energy storage converter system.

Description

Technical Field

[0001] This invention belongs to the field of power electronic control technology, specifically relating to a control method, device and system for a grid-type energy storage converter based on frequency disturbance observation. Background Technology

[0002] As the proportion of new energy power generation and energy storage devices connected to the power system via power electronic converters continues to increase, grid-based control is gradually being applied to energy storage converters. This enables the energy storage converters to exhibit controlled voltage source characteristics and provide inertia, damping, and voltage support to the power grid. Existing grid-based energy storage converter systems typically employ virtual synchronous generator control or power synchronization control. They generate the output angular frequency and synchronization angle based on active power deviation and generate an output voltage amplitude reference based on reactive power deviation. The converter operation is then controlled through an outer voltage loop, an inner current loop, and a modulation stage. The existing technical literature "C. Li, Y. Yang, Y. Cao, L. Wang, T. Dragičević, and F. Blaabjerg, Frequency and Voltage Stability Analysis of Grid-Forming Virtual Synchronous Generator Attached to Weak Grid, IEEE Journal of Emerging and Selected Topics in Power Electronics, vol. 10, no. 3, pp. 2662–2671, Jun. 2022" establishes a frequency and voltage stability model for grid-forming virtual synchronous generators connected to weak grids. It analyzes the impact of grid strength and control parameters such as inertia and damping on the stable operation of the system, showing that a decrease in grid strength weakens the synchronization capability between the grid-forming virtual synchronous generator and the grid, and may cause low-frequency oscillations.

[0003] The output angular frequency and synchronization angle of a grid-formed converter are typically dynamically generated by the power synchronization control loop. The dynamic coupling between active power, reactive power, and output voltage amplitude can alter the system's equivalent damping, causing oscillations in the output frequency and power. Existing literature, "Y. Yang, J. Xu, C. Li, W. Zhang, Q. Wu, M. Wen, and F. Blaabjerg, A New Virtual Inductance Control Method for Frequency Stabilization of Grid-Forming Virtual Synchronous Generators, IEEE Transactions on Industrial Electronics, vol. 70, no. 1, pp. 441–451, Jan. 2023," establishes a small-signal model of a grid-formed virtual synchronous generator. It analyzes the frequency oscillation mechanism under active and reactive power coupling conditions using feedback factors and proposes a virtual inductor control strategy based on the energy conservation principle to suppress frequency and power oscillations and improve system damping and stability margin. This method primarily alters the power coupling relationship and system dynamic characteristics by adding a virtual inductor.

[0004] To improve the frequency dynamics and synchronization stability of virtual synchronous generators, existing technologies also reshape the equivalent inertia and damping characteristics of the system by adjusting the virtual inertia or adding additional damping elements to the active power control loop. The existing technical literature "X. Hou, Y. Sun, X. Zhang, J. Lu, P. Wang, and JM Guerrero, Improvement of Frequency Regulation in VSG-Based AC Microgrid Via AdaptiveVirtual Inertia, IEEE Transactions on Power Electronics, vol. 35, no. 2, pp.1589–1602, Feb. 2020" proposes an adaptive virtual inertia control method. This method increases the virtual inertia when the system frequency deviates from the rated value to mitigate frequency changes and improve the frequency minimum; and decreases the virtual inertia during the system frequency recovery process to accelerate dynamic recovery. Another existing technical document, "X. Xiong, C. Wu, B. Hu, D. Pan, and F. Blaabjerg, Transient Damping Method for Improving the SynchronizationStability of Virtual Synchronous Generators, IEEE Transactions on Power Electronics, vol. 36, no. 7, pp. 7820–7831, Jul. 2021," analyzes the synchronization stability problem of virtual synchronous generators under large disturbances and adds a transient damping element to the active power control loop to coordinate synchronization stability and inertia response. The above method shows that virtual inertia and damping parameters simultaneously affect the frequency change rate, dynamic recovery process, and synchronization stability; parameter shaping alone is insufficient to simultaneously address various dynamic performance characteristics under different grid conditions and operating conditions.

[0005] To address the impact of grid frequency disturbances and converter current and power capacity constraints on the stable operation of grid-formed converters, existing technologies improve the frequency response of converters by introducing grid frequency feedback or constructing composite power-frequency synchronization loops. The existing literature "T. Xu, S. Jiang, Y. Zhu, and G. Konstantinou, Composite Power-Frequency Synchronization Loop for Enhanced Frequency Response Considering Current and Power Limits of Grid-Forming Converters, IEEE Transactions on Power Electronics, vol. 40, no. 4, pp. 4969–4983, Apr. 2025" studies the impact of current and power limitations on the frequency response and synchronization stability of grid-formed converters. It introduces a phase-locked loop-based droop channel into the traditional power synchronization loop to form a composite power-frequency synchronization loop, thereby improving the equivalent damping and synchronization stability under severe frequency disturbances. This method relies on a phase-locked loop to obtain grid frequency information. Its control focuses on coordinating current limiting, power limiting, and frequency response. There is still room for improvement in the unified online estimation and compensation of the combined effects of grid frequency disturbances and grid strength changes.

[0006] Therefore, to address the issue that the stability margin of the active power synchronization loop in existing grid-connected energy storage converter systems decreases under grid frequency disturbances and grid strength variations, and that it is difficult to balance frequency disturbance adaptability and power synchronization dynamic performance simply by adjusting virtual inertia, damping parameters, or introducing explicit grid frequency feedback, it is necessary to propose a grid-connected energy storage converter control method based on frequency disturbance observation. This method, while retaining the basic power synchronization control structure, performs online estimation and compensation for the total frequency-related disturbances acting on the active power synchronization control loop, thereby improving the frequency disturbance adaptability and power synchronization stability of the grid-connected energy storage converter system. Summary of the Invention

[0007] The present invention aims to provide a control method, device and system for grid-type energy storage converters based on frequency disturbance observation. Under the condition of retaining the basic power synchronization control structure, the method performs online estimation and compensation for the total frequency-related disturbances acting on the active power synchronization control loop, so as to improve the frequency disturbance adaptability and power synchronization stability of the grid-type energy storage converter system.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The converter system includes: an energy storage unit that provides input DC power, which is then passed through a three-phase converter bridge and connected to the power grid, thereby achieving bidirectional power conversion between the energy storage unit and the power grid; characterized in that the control method includes: An active power deviation signal is generated based on the active power reference value and the actual active power, and an angular frequency deviation signal is generated based on the rated angular frequency and the output angular frequency. Using the active power deviation signal as the observed output and the angular frequency deviation signal as the observed input, state observation is performed to obtain the frequency-related total disturbance estimate. Based on the frequency-related total disturbance estimate and the input gain, a frequency compensation amount is generated; The rated angular frequency, the fundamental angular frequency deviation, and the frequency compensation amount are superimposed to obtain the output angular frequency; Integrating the output angular frequency generates the synchronization angle; The switching drive signal generated based on the synchronization angle is used to control the switching transistors of the converter system.

[0009] Further, using the active power deviation signal as the observed output and the angular frequency deviation signal as the observed input, state observation is performed to obtain a frequency-related total disturbance estimate, including: Based on the active power deviation signal e P and first state estimator Generate observation error signal ε , means as follows: ; Second state estimator An update is performed, as shown below: ; The second state estimate As the frequency-related total disturbance estimate Represented as: .

[0010] Further, based on the frequency-related total disturbance estimate and the input gain, a frequency compensation amount is generated, including: Based on the second state estimate and the input gain of the extended state observer b Generate frequency compensation amount ω fc : ; Further, the rated angular frequency, the fundamental angular frequency deviation, and the frequency compensation amount are superimposed to obtain the output angular frequency, including: The frequency compensation amount ω fc Deviation Δ from the fundamental angular frequency ω 0 superposition, and introduce the rated angular frequency. ω ref The output angular frequency is obtained. ω : ; The step of integrating the output angular frequency to generate the synchronization angle includes: In the formula, Let be the synchronization angle at time t. for Synchronization angle at time, for The output angular frequency corresponding to the given moment.

[0011] Furthermore, the grid-type energy storage converter control method based on frequency disturbance observation also includes: Collect the three-phase output voltage, three-phase grid-connected current, and three-phase filter inductor current on the grid-connected side of the three-phase filter inductor; Calculate the actual active power and actual reactive power based on the three-phase output voltage and the three-phase grid current. The three-phase output voltage and the three-phase grid-connected current are subjected to a two-phase stationary coordinate transformation with unchanged amplitude to obtain the α-axis component and β-axis component of the output voltage, and the α-axis component and β-axis component of the grid-connected current, respectively. The actual active power is calculated according to the following formula. P and the actual reactive power Q : ; The active power deviation signal is generated according to the following formula. e P and the angular frequency deviation signal e ω : In the formula, P ref The active power reference value is... ω ref The rated angular frequency, ω The output angular frequency of the grid-type energy storage converter system is given.

[0012] Furthermore, the switching transistors of the converter system are controlled by generating a switching drive signal based on the synchronization angle, including: The actual output voltage amplitude is calculated based on the three-phase output voltage, and an output voltage amplitude reference is generated based on the actual reactive power, the reactive power reference value, the rated output voltage amplitude, and the actual output voltage amplitude. The output voltage amplitude reference satisfies the following: In the formula, D q The preset reactive power-voltage droop coefficient, τ This is the preset reactive power control proportional coefficient. V o This represents the actual output voltage amplitude. Q This represents the actual reactive power. Q ref This is a reference value for reactive power. V ref This is the rated output voltage amplitude; Based on the synchronization angle, the three-phase output voltage and the three-phase filter inductor current are subjected to a rotating coordinate transformation to obtain the d-axis and q-axis components of the output voltage and the d-axis and q-axis components of the filter inductor current. A current reference is generated using the voltage outer loop based on the output voltage amplitude reference and the d-axis and q-axis components of the output voltage; The modulation voltage component is generated using the inner current loop based on the current reference and the d-axis and q-axis components of the filter inductor current. The three-phase modulation reference signal is obtained by performing an inverse coordinate transformation on the modulation voltage component. Perform pulse width modulation (PWM) operations based on the three-phase modulation reference signal to generate a PWM signal; A switch drive signal is generated based on the pulse width modulation signal to control the power switch of the converter system to turn on and off.

[0013] This invention provides a control system for a grid-type energy storage converter based on frequency disturbance observation. The grid-type energy storage converter includes a converter system and a control system, wherein the control system provides switching drive signals to the converter system. The converter system includes: an energy storage unit that provides input DC power, which is then converted and filtered by a three-phase converter bridge and an AC filter module before being connected to the power grid, thereby achieving bidirectional power conversion between the energy storage unit and the power grid; the control system includes: The deviation signal generation module generates an active power deviation signal based on the active power reference value and the actual active power, and generates an angular frequency deviation signal based on the rated angular frequency and the feedback output angular frequency. A frequency disturbance observation module generates a frequency-related total disturbance estimate based on the input gain, active power deviation signal, and angular frequency deviation signal. The frequency compensation and synchronization angle generation module generates the output angular frequency and synchronization angle based on the fundamental angular frequency deviation, the frequency-related total disturbance estimate, the input gain, and the rated angular frequency. A switch drive module generates a switch drive signal based on the synchronization angle to control the power switch transistor to turn on and off.

[0014] Furthermore, the control system of the grid-type energy storage converter based on frequency disturbance observation includes: An output voltage sampling module acquires the three-phase output voltage and generates a three-phase output voltage signal; A grid-connected current sampling module, which collects three-phase grid-connected current and generates a three-phase grid-connected current signal; A filter inductor current sampling module is provided, which acquires the three-phase filter inductor current and generates a three-phase filter inductor current signal. A basic active power synchronization control module, which generates a basic angular frequency deviation based on the active power deviation signal; The reactive power-voltage control module generates an output voltage amplitude reference based on the actual reactive power, the reactive power reference value, the rated output voltage amplitude, and the actual output voltage amplitude. A dual closed-loop control module for voltage outer loop and current inner loop generates a modulated voltage component based on the output voltage amplitude reference, synchronization angle, three-phase output voltage signal and three-phase filter inductor current signal. The coordinate inverse transformation and modulation module performs coordinate inverse transformation on the modulation voltage component according to the synchronization angle to generate a three-phase modulation reference signal and a pulse width modulation signal.

[0015] Furthermore, the control system of the grid-type energy storage converter based on frequency disturbance observation includes a frequency disturbance observation module, which includes: The observation error generation unit, based on the active power deviation signal... e P and first state estimator Generate observation error signal ε It is expressed as follows: In the formula, the first state estimate Used to track active power deviation signals e P ; An input gain configuration unit generates an input gain representation as follows: In the formula, b For input gain, k δP The nominal small-signal gain is the change in power angle to the change in active power at the preset steady-state operating point. The first state estimation unit estimates the second state. An update is performed, as shown below: In the formula, s Represents a Laplace complex variable. G 2 represents the gain of the second observer. ω o This is the preset observer bandwidth; The second state estimation unit estimates the first state. An update is performed, as shown below: In the formula, G 1 represents the gain of the first observer. N The gain coefficient is a dimensionless coefficient. Total disturbance estimation output unit, the total disturbance estimation output unit outputs the second state estimate As the frequency-related total disturbance estimate Output, the second state estimate Used to estimate the total frequency-dependent disturbance acting on the active power synchronization control loop. f td Therefore, the frequency-dependent total disturbance estimate Represented as: .

[0016] This invention provides a grid-type energy storage converter based on frequency disturbance observation, comprising: The converter system and control system are connected, and the control system provides switching drive signals to the converter system. The converter system includes an energy storage unit that provides input DC power. The input DC power is converted by a three-phase converter bridge and an AC filter module to obtain three-phase filter inductor current and three-phase output voltage, which are then connected to the power grid, thereby realizing bidirectional power conversion between the energy storage unit and the power grid.

[0017] Furthermore, the control system employs a grid-type energy storage converter control method based on frequency disturbance observation, as described above.

[0018] Furthermore, the control system integrates any of the above-mentioned grid-type energy storage converter control systems based on frequency disturbance observation.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes the dynamic characteristics of the active power synchronization loop in a grid-type energy storage converter system based on frequency disturbance observation. It uniformly characterizes the small-signal gain deviation of active power caused by grid angular frequency disturbance and grid strength change as a frequency-related total disturbance acting on the active power synchronization control loop. While retaining the basic active power synchronization control structure, it constructs an extended state observer with the active power deviation signal as the observed output and the angular frequency deviation signal as the observed input to estimate the frequency-related total disturbance online. The estimation result is then converted into a frequency compensation quantity and superimposed on the basic output angular frequency. Thus, without relying on phase-locked loops or explicit grid frequency detection, it achieves unified compensation for grid frequency disturbance and grid strength change.

[0020] To make the above-mentioned features and advantages of the invention more apparent and understandable, specific embodiments are described below, and detailed descriptions are provided in conjunction with the accompanying drawings. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a grid-type energy storage converter based on frequency disturbance observation, provided as an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram of the control system of a grid-type energy storage converter based on frequency disturbance observation, provided as an embodiment of the present invention.

[0023] Figure 3 A schematic diagram of the grid-connected equivalent circuit of a grid-type energy storage converter system based on frequency disturbance observation is provided for one embodiment of the present invention.

[0024] Figure 4 This is a schematic diagram of the frequency disturbance observation compensation control principle provided for one embodiment of the present invention.

[0025] Figure 5 This is a schematic diagram of the internal structure of a frequency disturbance observer provided in one embodiment of the present invention.

[0026] Figure 6 The flowchart of a frequency disturbance observation and control method for a grid-type energy storage converter system based on frequency disturbance observation is provided for one embodiment of the present invention.

[0027] Figure 7 The figures show experimental waveforms of different power synchronization control methods when the grid frequency experiences a step change of -0.4 Hz. Figure 7 Figure (a) shows the experimental waveform of VSG-PSC1. Figure 7 Figure (b) shows the experimental waveforms of VSG-PSC2. Figure 7 Figure (c) shows the experimental waveform of FDO-PSC.

[0028] Figure 8 The figures show experimental waveforms of different power synchronization control methods when the grid frequency experiences a step change of -0.8 Hz. Figure 8 Figure (a) shows the experimental waveform of VSG-PSC1. Figure 8 Figure (b) shows the experimental waveforms of VSG-PSC2. Figure 8 Figure (c) shows the experimental waveform of FDO-PSC.

[0029] Figure 9 The figures show experimental waveforms of different power synchronization control methods when the active power reference value experiences a step change of -400 W. Figure 9 Figure (a) shows the experimental waveform of VSG-PSC1. Figure 9 Figure (b) shows the experimental waveforms of VSG-PSC2. Figure 9 Figure (c) shows the experimental waveform of FDO-PSC.

[0030] Figure 10 The figures show experimental waveforms for different power synchronization control methods when the active power reference value experiences a +400 W step change. Figure 10 Figure (a) shows the experimental waveform of VSG-PSC1. Figure 10 Figure (b) shows the experimental waveforms of VSG-PSC2. Figure 10 Figure (c) shows the experimental waveform of FDO-PSC.

[0031] In the diagram: 1. Converter system; 2. Control system; 3. Power grid; 11. Energy storage unit module; 12. Three-phase converter bridge; 13. AC filter module; 201. Output voltage sampling module; 202. Grid-connected current sampling module; 203. Filter inductor current sampling module; 204. Power calculation module; 205. Deviation signal generation module; 206. Basic active power synchronization control module; 207. Frequency disturbance observation module; 208. Frequency compensation and synchronization angle generation module; 209. Reactive power-voltage control module; 210. Voltage outer loop and current inner loop dual closed-loop control module; 211. Coordinate inverse transformation and modulation module; 212. Switch drive module; 2071. Observation error generation unit; 2072. Input gain configuration unit; 2073. First state estimation unit; 2074. Second state estimation unit; 2075. Total disturbance estimation output unit. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the described embodiments are only used to illustrate the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Without departing from the technical concept of the present invention, those skilled in the art can make corresponding adjustments to the relevant system structure, control parameters, and control links.

[0033] In the description of this invention, "connection" can refer to a direct connection between two components or an indirect connection between two components through one or more intermediate components; expressions such as "first" and "second" are only used to distinguish different signals, states or components and do not indicate their order or importance.

[0034] Figure 1 This is a schematic diagram of a grid-type energy storage converter based on frequency perturbation observation. Figure 1 As shown, this application provides a grid-type energy storage converter based on frequency disturbance observation, including a converter system 1, a control system 2 and a power grid 3. The AC side of the converter system 1 is connected to the power grid 3 via an AC filter module 13. The output terminal of the control system 2 is connected to the control terminal of the converter system 1. The control system 2 provides a switching drive signal to the converter system 1.

[0035] As an example, the converter system 1 includes: an energy storage unit module 11, which provides input DC power. V dc The input DC power V dc The input DC power is processed by the three-phase converter bridge 12 and AC filter module 13. V dc The phase a filter inductor current is obtained by transformation and filtering. iLa b-phase filter inductor current i Lb c-phase filter inductor current i Lc and the output voltage of phase a v oa b-phase output voltage v ob c-phase output voltage v oc It is connected to the power grid 3 to realize bidirectional power conversion between the energy storage unit module 11 and the power grid 3.

[0036] The three-phase converter bridge 12 includes a first bridge arm, a second bridge arm, and a third bridge arm, which are connected in parallel between the positive and negative terminals of the DC bus. The first bridge arm is composed of a series connection of switch Q1 and switch Q2, the second bridge arm is composed of a series connection of switch Q3 and switch Q4, and the third bridge arm is composed of a series connection of switch Q5 and switch Q6. The series connection points of the first bridge arm, the second bridge arm, and the third bridge arm serve as the three-phase AC output terminals of the three-phase converter bridge 12, which are used to connect to the AC filter module 13.

[0037] The AC filtering module 13 includes: a-phase filter inductor L fa b-phase filter inductor L fb c-phase filter inductor L fc and the a-phase filter capacitor C fa b-phase filter capacitor C fb c-phase filter capacitor C fc The a-phase filter inductor L fa b-phase filter inductor L fb c-phase filter inductor L fc The a-phase filter capacitor is connected in series between the three-phase AC output terminals of the three-phase converter bridge 12 and the power grid. C fa b-phase filter capacitor C fb c-phase filter capacitor C fc One end of each filter module is connected to the grid-connected side of the filter inductor of each phase, and the other ends are connected to each other to form a star connection. The AC filter module 13 is used to filter out the switching frequency harmonics generated by the three-phase converter bridge 12.

[0038] The power grid 3 is connected to the grid-connected side of the AC filter module 13.

[0039] For example, please refer to Figure 2 , Figure 2 This is a schematic diagram of a control system for a grid-type energy storage converter based on frequency disturbance observation, provided in one embodiment of the present invention. The control system 2 may include: Output voltage sampling module 201, the output voltage sampling module 201 collects the output voltage of phase a. v oa b-phase output voltage v ob c-phase output voltage v oc And generate a three-phase output voltage signal. v oabc ; Grid-connected current sampling module 202, the grid-connected current sampling module 202 collects the grid-connected current of phase a. i oa Phase b grid current i ob c-phase grid current i oc And generate a three-phase grid-connected current signal. i oabc ; The filter inductor current sampling module 203 collects the filter inductor current of phase a. i La b-phase filter inductor current i Lb c-phase filter inductor current i Lc And generate three-phase filtered inductor current signals. i Labc .

[0040] Power calculation module 204, the power calculation module 204 calculates based on the three-phase output voltage signal v oabc and three-phase grid-connected current signal i oabc Calculate the actual active power P and actual reactive power Q ; Deviation signal generation module 205, the deviation signal generation module 205 based on active power reference value P ref With actual active power P Generate active power deviation signal e P and according to the rated angular frequency ωref With output angular frequency ω Generate angular frequency deviation signal e ω ; The basic active power synchronization control module 206, which controls the basic active power synchronization based on the active power deviation signal... e P Generate fundamental angular frequency deviation Δ ω 0; Frequency disturbance observation module 207, the frequency disturbance observation module 207 according to input gain b Active power deviation signal e P and angular frequency deviation signal e ω Generate frequency-related total disturbance estimate ; Frequency compensation and synchronization angle generation module 208, the frequency compensation and synchronization angle generation module 208 based on the fundamental angular frequency deviation Δ ω 0. Frequency-dependent total disturbance estimate Input gain b and rated angular frequency ω ref Generate output angular frequency ω and synchronization angle θ Output angular frequency ω Feedback is sent to the deviation signal generation module 205; Reactive power-voltage control module 209, the reactive power-voltage control module 209 according to the actual reactive power Q Reactive power reference value Q ref Rated output voltage amplitude V ref and actual output voltage amplitude V o Generate output voltage amplitude reference V oi ; The voltage outer loop and current inner loop dual closed-loop control module 210, wherein the voltage outer loop and current inner loop dual closed-loop control module 210 refers to the output voltage amplitude reference. V oi Synchronization Angle θ Three-phase output voltage signal v oabc and three-phase filter inductor current signal i Labc Generate modulated voltage components ; Inverse coordinate transformation and modulation module 211, the inverse coordinate transformation and modulation module 211 according to the synchronization angle θ For modulated voltage components Perform inverse coordinate transformation to generate a three-phase modulation reference signal and a pulse width modulation signal. PWM ; Switch driving module 212, the switch driving module 212 according to pulse width modulation signal PWM Generate switch drive signal u GQ1 ~ u GQ6 It controls the on and off states of power switching transistors Q1 to Q6.

[0041] Specifically, the switch drive signal u GQ1 Controls the switching on and off of power switch Q1, and the switching drive signal. u GQ2 Controls the switching on and off of power switch Q2, and the switching drive signal. u GQ3 Controls the switching on and off of power switch Q3, and the switching drive signal. u GQ4 Controls the switching on and off of power switch Q4, and the switching drive signal. u GQ5 Controls the switching on and off of power switch Q5, and the switching drive signal. u GQ6 Controls the on and off states of power switch Q6.

[0042] Through the above control structure, the foundation active power synchronization control module 206 outputs the foundation angular frequency deviation Δ. ω 0; Frequency disturbance observation module 207 estimates the total frequency-related disturbance. Online estimation of the combined impact of grid frequency disturbances and grid strength changes on the active power synchronization control loop; frequency compensation and synchronization angle generation module 208 estimates the total frequency-related disturbance. Correct output angular frequency ω And generate the synchronization angle required for voltage and current dual closed-loop control and modulation. θ This creates a frequency disturbance observation and compensation control closed loop that does not require the grid angular frequency as a direct input.

[0043] Please see Figure 3 , Figure 3 This is a schematic diagram of the grid-connected equivalent circuit of a grid-type energy storage converter system based on frequency perturbation observation. Figure 3 As shown, the grid-type energy storage converter system based on frequency perturbation observation can be equivalent to the output voltage phasor. V o ∠ δ Controlled voltage source and equivalent output impedance Zo In a series configuration, power grid 3 can be represented as a power grid voltage phasor. V g The voltage source with ∠0 and the equivalent impedance of the power grid Z g A series structure. Among them, δ Output voltage phasor of a grid-type energy storage converter system based on frequency perturbation observation V o ∠ δ With grid voltage phasor V g The angle of attack between ∠0 and ∠0.

[0044] Equivalent output impedance Z o Equivalent impedance to power grid Z g Constitutes the equivalent total impedance Z t It is expressed as follows: In the formula, r t The resistive component of the equivalent total impedance. X t For the sense component, φ The impedance angle is denoted by j, which represents the imaginary unit.

[0045] In equivalent total impedance Z t Under conditions where inductive power is dominant, the actual active power transmitted from converter system 1 to grid 3 P It can be approximated as: In the formula, This represents the actual output voltage amplitude. This represents the actual grid voltage amplitude.

[0046] By performing small-signal linearization on the above active power-power angle relationship near the preset steady-state operating point, and using a small-angle approximation of the steady-state power angle, we can obtain: In the formula, k δP The nominal small-signal gain is the ratio of the change in power angle to the change in active power at the preset steady-state operating point. This represents the minute change in actual active power relative to the active power at the steady-state operating point. It is the minute change in the power angle relative to the steady-state operating point power angle.

[0047] In the formula, Von and V gn These represent the output voltage amplitude and grid voltage amplitude of the grid-type energy storage converter system based on frequency disturbance observations at this operating point, respectively. It is the sum of the equivalent output reactance of the grid-type energy storage converter system based on frequency disturbance observation and the equivalent reactance of the power grid.

[0048] Gongjiao δ Synchronization angle θ Phase angle with grid voltage θ g The rate of change of the difference satisfies: In the formula, The output angular frequency of the grid-type energy storage converter system. The angular frequency of the power grid. The angular frequency deviation signal, Δ ω g The power grid angular frequency disturbance is expressed as follows: In the formula, This is the rated angular frequency.

[0049] When changes in grid strength cause a deviation Δ between the actual small-signal gain and the nominal small-signal gain... k δP At that time, at the active power reference value P ref Under the condition that the frequency remains unchanged during the disturbance, the active power deviation signal e P = P ref - P The dynamic relationship is represented as: In the formula: Frequency-dependent total disturbance A unified characterization of the combined effects of grid angular frequency disturbances and small-signal gain deviations in active power caused by grid strength variations on the dynamic synchronization of active power.

[0050] Frequency disturbance observation module 207 uses active power deviation signal As the observed output quantity, the angular frequency deviation signal e ω As an observed input, the total frequency-dependent perturbation Online estimation yields the frequency-dependent total disturbance estimate. No need to change the grid angular frequency ωg As the direct input to this module.

[0051] Figure 4 This is a schematic diagram of the frequency disturbance observation and compensation control principle. The frequency disturbance observation and compensation control is jointly implemented by the basic active power synchronization control module 206, the frequency disturbance observation module 207, and the frequency compensation and synchronization angle generation module 208. The basic active power synchronization control module 206 calculates based on the active power deviation signal... e P Generate fundamental angular frequency deviation Δ ω 0; The frequency compensation and synchronization angle generation module 208 estimates based on the second state. and input gain b Generate frequency compensation amount ω fc The rated angular frequency ω ref , fundamental angular frequency deviation Δ ω 0 and frequency compensation amount ω fc Superposition yields the output angular frequency. ω For output angular frequency ω Perform integration to generate the synchronization angle. θ In this embodiment, the basic active power synchronization control module 206 adopts the virtual synchronous generator rotor motion equation, and its control relationship is as follows: In the formula, J The preset virtual moment of inertia, D p The preset active power loop damping coefficient, ω ref This is the rated angular frequency.

[0052] No frequency compensation was introduced. At that time, the fundamental output angular frequency ω 0 is: The basic active power synchronous control module 206 is used to generate the basic angular frequency deviation Δ of the grid-type energy storage converter system. ω 0. Based on this, the frequency disturbance observation module 207 and the frequency compensation and synchronization angle generation module 208 adjust the fundamental angular frequency deviation Δ. ω The output angular frequency is obtained by correcting 0. .

[0053] Figure 5 This is a schematic diagram of the internal structure of the frequency disturbance observation module, as shown below. Figure 5 As shown, the frequency disturbance observation module 207 employs a second-order linear extended state observer. The active power deviation signal... eP As the observed output quantity, the angular frequency deviation signal e ω As the observation input, the active power deviation signal will be used. e P Total frequency-related disturbance f td Defined as first state variables Second state variable It is expressed as follows: As an example, the frequency disturbance observation module 207 includes: Observation error generation unit 2071, the observation error generation unit 2071 based on active power deviation signal e P and first state estimator Generate observation error signal ε It is expressed as follows: Wherein, the first state estimate Used to track active power deviation signals e P .

[0054] Input gain configuration unit 2072, the input gain configuration unit 2072 receiving angular frequency deviation signal e ω After input gain b Obtain the first observation estimate and generate the input gain. b It is expressed as follows: In the formula, k δP The nominal small-signal gain is based on the change in power angle to the change in active power at the preset steady-state operating point. b This is the input gain for the extended state observer.

[0055] First state estimation unit 2073, the first state estimation unit 2073 estimates the second state quantity. An update is performed, as shown below: In the formula, s Represents a Laplace complex variable. G 2 represents the gain of the second observer. ω oThe preset observer bandwidth can be set according to the dynamic speed of the active power synchronization control loop, the controller sampling frequency, and the noise level of the power measurement signal, so as to coordinate the tracking speed and noise suppression capability of the frequency-dependent total disturbance.

[0056] The second state estimation unit 2074 estimates the first state quantity. An update is performed, as shown below: In the formula, G 1 represents the gain of the first observer. N This is a dimensionless gain coefficient.

[0057] Total disturbance estimation output unit 2075, the total disturbance estimation output unit 2075 outputs the second state estimate As the frequency-related total disturbance estimate Output, the second state estimate Used to estimate the total frequency-dependent disturbance acting on the active power synchronization control loop. f td Therefore, the frequency-dependent total disturbance estimate Represented as: .

[0058] Frequency disturbance observation module 207 does not require the grid angular frequency to be measured. ω g Or the grid angular frequency disturbance Δ ω g Instead of direct input, it is based on the active power deviation signal. e P Angular frequency deviation signal generated inside the grid-type energy storage converter system e ω Online estimation of frequency-related total disturbance. .

[0059] As an example, the frequency compensation and synchronization angle generation module 208 calculates based on the second state estimate. and input gain b Generate frequency compensation amount ω fc , means as follows: .

[0060] Furthermore, the rated angular frequency ω ref , fundamental angular frequency deviation Δ ω 0 and frequency compensation amount ωfc Superposition yields the output angular frequency. ω , means as follows: .

[0061] Furthermore, regarding the output angular frequency ω Perform integration to generate the synchronization angle. θ , means as follows: In the formula, Let be the synchronization angle at time t. for Synchronization angle at time, Let λ be the output angular frequency at time λ.

[0062] Due to angular frequency deviation signal e ω Defined as: Therefore, frequency compensation amount ω fc At the output angular frequency ω When positive and negative superposition occurs, it will affect the active power deviation signal. e P The total frequency-related disturbance is formed in the dynamic relationship. f td The opposite direction of the compensation effect weakens the impact of the frequency-related total disturbance on the dynamic synchronization of active power, thereby achieving frequency compensation.

[0063] In one digital control implementation, the control system 2 integrates a control method for a grid-type energy storage converter system based on frequency disturbance observation, which can be implemented by a digital signal processor, microcontroller, field-programmable gate array, or other digital controller. The aforementioned differential equations can be digitally calculated using the Euler method, bilinear transform method, or other discretization methods according to a preset sampling period. This invention does not limit the specific controller type or numerical discretization method.

[0064] Through the above control process, the basic active power synchronization control structure is retained. The frequency disturbance observation module 207 estimates the comprehensive impact of grid frequency disturbance and grid strength changes on the active power synchronization control loop online. The frequency compensation and synchronization angle generation module 208 corrects the output angular frequency based on the disturbance estimation results, thereby improving the power synchronization stability of the grid-type energy storage converter system under frequency disturbance conditions.

[0065] Figure 6This is a flowchart of the control method for a grid-type energy storage converter system based on frequency disturbance observation. This control method is executed by control system 2. During the operation of the grid-type energy storage converter system based on frequency disturbance observation, the steps are executed cyclically according to a preset control cycle.

[0066] The preset control cycle can be determined based on the switching frequency, sampling frequency, and computing power of the grid-type energy storage converter system based on frequency disturbance observation. Within each control cycle, the control system 2 sequentially completes electrical quantity sampling, power calculation, deviation signal generation, frequency-related total disturbance observation, fundamental angular frequency deviation generation, frequency compensation quantity generation, output angular frequency superposition, and synchronization angle generation.

[0067] As an example, the control method for the grid-type energy storage converter system based on frequency disturbance observation includes: Step S1: Acquire the three-phase output voltage on the grid-connected side of the three-phase filter inductor. v oa , v ob , v oc Three-phase grid-connected current i oa , i ob , i oc and three-phase filter inductor current i La , i Lb , i Lc .

[0068] The acquired voltage and current signals can be converted into digital sampling signals by voltage sensors, current sensors, signal conditioning circuits, and analog-to-digital converters, and then respectively form three-phase output voltage signals. v oabc Three-phase grid-connected current signal i oabc and three-phase filter inductor current signal i Labc .

[0069] Step S2: Based on the three-phase output voltage v oa , v ob , v oc Three-phase grid-connected current i oa , i ob , i oc Calculate the actual active power Pand actual reactive power Q , means as follows: in, The α-axis component of the three-phase output voltage is obtained by analyzing the three-phase output voltage signal. v oabc Obtained by performing a two-phase stationary coordinate transformation with unchanged amplitude; The β-axis component of the three-phase output voltage is obtained by analyzing the three-phase output voltage signal. v oabc Obtained by performing a two-phase stationary coordinate transformation with unchanged amplitude; In one implementation, the actual active power and actual reactive power are low-pass filtered before being input to the subsequent control module to reduce the influence of switching frequency components and sampling noise.

[0070] Step S3: Based on the active power reference value P ref and actual active power P Generate active power deviation signal : According to the rated angular frequency ω ref and output angular frequency ω Generate angular frequency deviation signal : In one discrete control implementation, step S3 uses the output angular frequency stored in the previous control cycle. ω [ k -1] Calculate the angular frequency deviation signal of the current control cycle. Then generate the output angular frequency of the current control cycle. ω [ k Using this order of operations can avoid forming algebraic loops within the same control cycle.

[0071] Step S4: Using the active power deviation signal e P As the observed output quantity, the angular frequency deviation signal e ω As the observation input, the extended state observer is used to perform state observations, and the frequency-related total disturbance estimate is obtained. .

[0072] Step S5: Based on the active power deviation signal e P Generate fundamental angular frequency deviation Δ ω 0.

[0073] Step S6: Based on the frequency-dependent total disturbance estimate and the input gain of the extended state observer b Generate frequency compensation amount .

[0074] Step S7: Set the rated angular frequency ω ref , fundamental angular frequency deviation Δ ω 0 and the frequency compensation amount ω fc The output angular frequency is obtained by superimposing the results. .

[0075] Step S8: Output angular frequency Perform integration to generate the synchronization angle. θ .

[0076] In a digital controller, the synchronization angle can be updated discretely according to the following formula: In the formula, T s To preset the control cycle, k This is for controlling the cycle number. When the synchronization angle exceeds the angle range corresponding to one electrical cycle, periodic normalization can be performed.

[0077] Step S9: Based on the synchronization angle θ Generate switch drive signal u GQ1 ~ u GQ6 Control the switching transistors of the grid-type energy storage converter system.

[0078] After completing the above steps, control system 2 enters the next control cycle and repeats the above steps. The frequency-dependent total disturbance estimate is continuously updated within the cycle. Continuously correct the output angular frequency Continuously adjust the synchronization angle θ This enables the grid-type energy storage converter system to perform real-time control based on the dynamic changes in active power caused by grid frequency disturbances and grid strength variations.

[0079] The above sequence of steps is used to illustrate the logical relationships of the control method and does not require all operations to be executed strictly in the order described above. While keeping the data dependencies between steps unchanged, some sampling, calculation, and state update operations can be executed in parallel, or the execution order can be adjusted according to the task scheduling method of the digital controller.

[0080] The above steps constitute the core process of frequency disturbance observation and control in this invention. Based on this, those skilled in the art can use methods known in the art to generate the synchronization angle. θ and output angular frequency Used for subsequent control of the converter.

[0081] As an example, step S4 includes: Based on the active power deviation signal and first state estimator Generate observation error signal ε It is expressed as follows: ; Second state estimator An update is performed, as shown below: The second state estimate As the frequency-related total disturbance estimate Represented as: .

[0082] As an example, step S6 includes: Based on the second state estimate and input gain b Generate frequency compensation amount ω fc : .

[0083] As an example, step S7 includes: The frequency compensation amount ω fc Deviation Δ from the fundamental angular frequency ω 0 superposition, and introduce the rated angular frequency. ω ref The output angular frequency is obtained. ω : .

[0084] As an example, step S8 includes: The step of integrating the output angular frequency to generate the synchronization angle includes: .

[0085] As an example, step S9: based on the synchronization angle θ Generate switch drive signal u GQ1 ~ u GQ6 Controlling the switching transistors of a grid-type energy storage converter system includes: Step S91: Calculate the actual output voltage amplitude based on the three-phase output voltage.V o And based on the actual reactive power Q Reactive power reference value Q ref Rated output voltage amplitude V ref Combine the actual output voltage amplitude to generate an output voltage amplitude reference. V oi : In the formula, D q The preset reactive power-voltage droop coefficient, τ The preset reactive power control proportional coefficient is used to adjust the degree of influence of reactive power deviation on the output voltage amplitude reference.

[0086] Step S92: Based on the synchronization angle θ A rotating coordinate transformation is performed on the three-phase output voltage and the three-phase filter inductor current to obtain the d-axis and q-axis components of the output voltage and filter inductor current. The outer voltage loop is based on the output voltage amplitude reference. V oi The rotating coordinate component of the output voltage generates a current reference, and the inner current loop generates a modulation voltage component based on the current reference and the rotating coordinate component of the filter inductor current. .

[0087] Step S93: Based on the synchronization angle θ For modulated voltage components Perform inverse coordinate transformation to generate a three-phase modulation reference signal.

[0088] Step S94: Perform pulse width modulation operation based on the three-phase modulation reference signal to generate a pulse width modulation signal and control the operation of the grid-type energy storage converter system.

[0089] Specifically, the pulse width modulation method can be sinusoidal pulse width modulation, space vector pulse width modulation, or other modulation methods suitable for the three-phase converter bridge.

[0090] Step S95: Generate a switching drive signal based on the pulse width modulation signal. u GQ1 to u GQ6 The power switches Q1 to Q6 in the grid-type energy storage converter are controlled to turn on and off, thereby regulating the AC output voltage of the grid-type energy storage converter. v oabc Grid-connected current i oabc And power exchange with the power grid.

[0091] In one specific embodiment of this application, an experimental platform is built to verify the control method of a grid-type energy storage converter system based on frequency disturbance observation. The experimental platform includes a DC power supply, a three-phase converter prototype, an AC filter module, a line inductor, a programmable AC power supply, a digital controller, a host computer, and an oscilloscope.

[0092] The three-phase converter prototype adopts a three-phase two-level bridge structure. The DC side is connected to a DC power supply, and the AC side is connected to a programmable AC power supply via an AC filter module and a line inductor. The DC power supply is used to simulate the energy storage unit module 11 and provide the DC power required for the experiment; the line inductor is used to simulate the equivalent impedance of the power grid; the programmable AC power supply is used to simulate the power grid 3 and apply frequency perturbations; the digital controller is used to execute steps S1 to S9; the host computer is used to configure control parameters and running instructions; and the oscilloscope is used to acquire the grid-connected A-phase current, power angle, actual active power, and actual reactive power.

[0093] In summary, this invention utilizes the dynamic characteristics of the active power synchronization loop in a grid-type energy storage converter system based on frequency disturbance observation. It uniformly characterizes the small-signal gain deviation of active power caused by grid angular frequency disturbance and grid strength change as a frequency-related total disturbance acting on the active power synchronization control loop. While retaining the basic active power synchronization control structure, it constructs an extended state observer with the active power deviation signal as the observed output and the angular frequency deviation signal as the observed input to estimate the frequency-related total disturbance online. The estimation result is then converted into a frequency compensation quantity and superimposed on the basic output angular frequency. Thus, without relying on a phase-locked loop or explicit grid frequency detection, it achieves unified compensation for grid frequency disturbance and grid strength change.

[0094] This embodiment uses a DC power supply to provide DC power instead of an energy storage unit. In practical applications, the DC power supply can be replaced by a battery, supercapacitor, or other energy storage unit. The energy storage unit can be directly connected to the DC bus or connected to the DC bus via a bidirectional DC-DC converter.

[0095] In one specific parameter configuration, the experimental system parameters are shown in Table 1.

[0096] Table 1 Experimental System Parameters To compare the stability and dynamic response performance of different power synchronization controls under grid frequency disturbances and active power reference value disturbances, this embodiment sets up three control schemes: a traditional virtual synchronous generator power synchronization control scheme without frequency disturbance observation and compensation channels (VSG-PSC1), a traditional virtual synchronous generator power synchronization control scheme with reduced active power synchronization control parameters (VSG-PSC2), and a scheme that adds frequency disturbance observation and compensation channels to the basic active power synchronization control structure of VSG-PSC1 (FDO-PSC). The parameters of each control scheme are shown in Table 2.

[0097] Table 2 Parameter settings for three power synchronization control schemes In Table 2, "—" indicates that the corresponding control scheme does not have a frequency disturbance observation and compensation channel, and therefore does not involve the observer bandwidth. ω o Dimensionless gain coefficient N and observer input gain b .

[0098] The VSG-PSC1 employs traditional virtual synchronous generator power synchronization control without a frequency disturbance observation and compensation channel. The FDO-PSC adds a frequency disturbance observation and compensation channel to the basic active power synchronization control structure of the VSG-PSC1, and uses the same virtual moment of inertia as the VSG-PSC1. J and active circuit damping coefficient D p Therefore, the difference in experimental results between VSG-PSC1 and FDO-PSC mainly reflects the control effect of frequency disturbance observation and compensation channel generation.

[0099] The VSG-PSC2 also does not have a frequency disturbance observation and compensation channel, but it reduces the active power synchronization control parameters. Among these, the active power loop damping coefficient... D p and virtual moment of inertia J The synchronization is reduced to half that of VSG-PSC1. VSG-PSC2 is used to compare the dynamic response performance difference between the traditional VSG-PSC and FDO-PSC after extending the frequency disturbance stability range.

[0100] Figures 7 to 10 Experimental waveforms for three power synchronization control schemes under grid frequency step disturbances and active power reference value step disturbances are presented respectively. Each figure includes three sub-figures, among which... Figure 7 Figure (a) shows the experimental waveform of VSG-PSC1. Figure 7 Figure (b) shows the experimental waveforms of VSG-PSC2. Figure 7Figure (c) shows the experimental waveform of FDO-PSC; Figure 8 Figure (a) shows the experimental waveform of VSG-PSC1. Figure 8 Figure (b) shows the experimental waveforms of VSG-PSC2. Figure 8 Figure (c) shows the experimental waveform of FDO-PSC; Figure 9 (a) The figure shows the experimental waveforms of VSG-PSC1. Figure 9 Figure (b) shows the experimental waveforms of VSG-PSC2. Figure 9 Figure (c) shows the experimental waveform of FDO-PSC; Figure 10 (a) The figure shows the experimental waveforms of VSG-PSC1. Figure 10 Figure (b) shows the experimental waveforms of VSG-PSC2. Figure 10 Figure (c) shows the experimental waveforms of the FDO-PSC. Each set of experimental waveforms includes the grid-connected A-phase current. i a , and angle δ Actual active power P and actual reactive power Q .

[0101] conduct Figure 7 During the grid frequency disturbance experiment, the three-phase converter prototype was first controlled to operate stably under the conditions of a grid frequency of 50 Hz, an active power reference value of 1 kW, and a reactive power reference value of 0 kVar. Subsequently, the grid frequency was reduced from 50 Hz to 49.6 Hz using a programmable AC power supply, and a ΔVar was applied. f g Negative step disturbance at the grid frequency of -0.4 Hz.

[0102] like Figure 7 As shown in (a), when using VSG-PSC1, the three-phase converter prototype can resume stable operation, with an actual active power regulation time of 381.5 ms and an overshoot of 29.8 W.

[0103] like Figure 7 As shown in (b), when using VSG-PSC2, the prototype can also resume stable operation, but the actual active power regulation time increases to 712.8 ms and the overshoot increases to 130.1 W.

[0104] like Figure 7 As shown in (c), when using FDO-PSC, the prototype maintains stable operation with an actual active power adjustment time of 352.3 ms and an overshoot of 45.7 W.

[0105] Under this frequency disturbance condition, all three control schemes were able to maintain stability. The settling time of FDO-PSC was shorter than that of VSG-PSC1 and VSG-PSC2, and its overshoot was significantly smaller than that of VSG-PSC2, indicating that the frequency disturbance observation and compensation channel can improve the dynamic recovery speed under frequency disturbance without changing the basic virtual moment of inertia and damping parameters.

[0106] exist Figure 8 In the experiment shown, the initial operating conditions of the three-phase converter prototype are the same as those of the prototype. Figure 7 Same. The mains frequency is reduced from 50 Hz to 49.2 Hz using a programmable AC power supply, and a Δ is applied. f g Negative step disturbance at the grid frequency of -0.8 Hz.

[0107] like Figure 8 As shown in (a), when using VSG-PSC1, the active power deviation caused by grid frequency disturbance increases, and the actual active power and power angle oscillate continuously. The three-phase converter prototype failed to return to a stable operating state.

[0108] like Figure 8 As shown in (b), when using VSG-PSC2, the prototype can recover stable operation under the same frequency disturbance, with an actual active power adjustment time of 745.7 ms and an overshoot of 184.3 W.

[0109] like Figure 8 As shown in (c), when using FDO-PSC, the prototype can also maintain stable operation, with an actual active power adjustment time of 362.1 ms and an overshoot of 70.1 W.

[0110] The VSG-PSC1 and FDO-PSC use the same virtual moment of inertia and active power loop damping coefficient. Under these parameters, the VSG-PSC1 oscillates continuously after a -0.8 Hz frequency step, while the FDO-PSC is still able to recover stable operation, indicating that the FDO-PSC has a larger grid frequency disturbance stability margin compared to the traditional VSG-PSC with the same parameters.

[0111] By reducing the active power synchronization control parameters, the VSG-PSC2 improves the adaptability of the traditional VSG-PSC to grid frequency disturbances, enabling it to maintain stable operation under the -0.4 Hz and -0.8 Hz frequency disturbance conditions tested in this embodiment.

[0112] To further compare the active power dynamic response performance of the three control schemes, and to focus on the difference in dynamic performance between VSG-PSC2 and FDO-PSC under the aforementioned frequency disturbance conditions, negative and positive step tests of the active power reference value were conducted. Figure 9 and Figure 10 In the two independent experiments shown, the grid frequency was kept at 50Hz, the reactive power reference value was 0 kVar, and the three-phase converter prototype was controlled to operate stably under the condition of an active power reference value of 1 kW.

[0113] exist Figure 9 In the negative step experiment of the active power reference value shown, the active power reference value is reduced from 1 kW to 600 W, that is, Δ is applied. P ref =-400 W active power reference value step disturbance.

[0114] like Figure 9 As shown in (a), when using VSG-PSC1, the actual active power regulation time is 610.4 ms and the overshoot is 104.3 W.

[0115] like Figure 9 As shown in (b), when using VSG-PSC2, the actual active power regulation time is greater than 800 ms and the overshoot is 237.6 W.

[0116] like Figure 9 As shown in (c), when using FDO-PSC, the actual active power regulation time is 412.3 ms and the overshoot is 60.3 W.

[0117] Under the negative step condition of active power reference value, the settling time and overshoot of FDO-PSC are both smaller than those of VSG-PSC1 and VSG-PSC2, indicating that the frequency disturbance observation and compensation channel improves the frequency disturbance stability capability without reducing the active power reference value tracking performance. In contrast, although VSG-PSC2 improves the frequency disturbance adaptation range by reducing the active power synchronization control parameters, its active power dynamic response is significantly slower.

[0118] exist Figure 10 In another set of independent experiments shown, the active power reference value was increased from 1 kW to 1.4 kW, i.e., Δ was applied. P ref =+400 W active power reference value step disturbance.

[0119] like Figure 10 As shown in (a), when using VSG-PSC1, the actual active power regulation time is 392.1 ms and the overshoot is 17.3 W.

[0120] like Figure 10 As shown in (b), when using VSG-PSC2, the actual active power regulation time is 729.5 ms and the overshoot is 112.7 W.

[0121] like Figure 10 As shown in (c), when using FDO-PSC, the actual active power regulation time is 362.8 ms and the overshoot is 15.6 W.

[0122] Under positive step conditions of active power reference value, the settling time and overshoot of FDO-PSC are both smaller than those of the two VSG-PSC models, enabling it to track changes in active power reference value more quickly. VSG-PSC2 exhibits a longer settling time and a larger overshoot, further illustrating that while reducing traditional power synchronization control parameters can improve frequency disturbance adaptability, it can also reduce the dynamic response performance of active power control.

[0123] comprehensive Figure 7 and Figure 8 The experimental results show that, when using the same virtual moment of inertia... J and active circuit damping coefficient D p Under these conditions, FDO-PSC has a larger stability margin against grid frequency disturbances compared to VSG-PSC1. Both control schemes operate stably with a small frequency step of -0.4 Hz; however, when the frequency step increases to -0.8 Hz, VSG-PSC1 exhibits sustained power oscillations, while FDO-PSC is still able to recover stable operation.

[0124] By reducing the virtual moment of inertia and the active loop damping coefficient, the VSG-PSC2 can maintain stable operation under the same test frequency disturbance conditions as the FDO-PSC. However, Figures 7 to 10 This indicates that the VSG-PSC2 exhibits a longer settling time and a larger active power overshoot under both grid frequency disturbances and active power reference value disturbances, suggesting that improving stability margin by reducing traditional VSG-PSC control parameters will sacrifice dynamic response performance.

[0125] In contrast, FDO-PSC improves the grid frequency disturbance stability margin by observing and compensating for the total frequency-related disturbances acting on the active power synchronous control loop online, without changing the basic virtual moment of inertia and the active power loop damping coefficient. At the same time, it maintains a shorter settling time and a smaller overshoot under positive and negative step conditions of active power reference value.

[0126] This embodiment illustrates that, under the parameters and operating conditions given in the embodiment, FDO-PSC can balance the stability performance under grid frequency disturbances and the dynamic response performance of active power control.

[0127] Without departing from the spirit and essence of the invention, the invention may also have the following optional embodiments: First, the input gain of the extended state observer bBased on the nominal small-signal gain at the preset steady-state operating point k δP The settings can be fixed, or updated based on estimates of the output voltage amplitude, grid voltage amplitude, and equivalent total reactance. k δP And update the input gain accordingly. b .

[0128] Secondly, the observer bandwidth ω o and dimensionless gain coefficient N The configuration can be based on the dynamic speed of the active power synchronization control loop, the sampling frequency of the digital controller, and the electrical quantity sampling noise, and is not limited to the values ​​listed in Table 2.

[0129] Third, the virtual moment of inertia of the basic active power synchronization control module 206. J and active circuit damping coefficient D p The settings can be configured based on the rated capacity, grid strength, and expected dynamic performance of the grid-type energy storage converter system. The frequency disturbance observation and compensation channel can be combined with basic active power synchronization control modules with different parameter configurations while retaining the basic active power synchronization control structure.

[0130] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A control method for a grid-type energy storage converter based on frequency disturbance observation, wherein the grid-type energy storage converter includes a converter system and a control system, and the control system provides switching drive signals to the converter system; The converter system includes: An energy storage unit provides input DC power, which is then connected to the power grid via a three-phase converter bridge, enabling bidirectional power conversion between the energy storage unit and the power grid; characterized in that the control method includes: An active power deviation signal is generated based on the active power reference value and the actual active power, and an angular frequency deviation signal is generated based on the rated angular frequency and the output angular frequency. Using the active power deviation signal as the observed output and the angular frequency deviation signal as the observed input, state observation is performed to obtain the frequency-related total disturbance estimate. Based on the frequency-related total disturbance estimate and the input gain, a frequency compensation amount is generated; The rated angular frequency, the fundamental angular frequency deviation, and the frequency compensation amount are superimposed to obtain the output angular frequency; Integrating the output angular frequency generates the synchronization angle; The switching drive signal generated based on the synchronization angle is used to control the switching transistors of the converter system.

2. The control method for a grid-type energy storage converter based on frequency disturbance observation as described in claim 1, characterized in that, Using the active power deviation signal as the observed output and the angular frequency deviation signal as the observed input, state observation is performed to obtain a frequency-related total disturbance estimate, including: Based on the active power deviation signal e P and first state estimator Generate observation error signal ε , means as follows: ； Second state estimator An update is performed, as shown below: ； The second state estimate As the frequency-related total disturbance estimate Represented as: 。 3. The control method for a grid-type energy storage converter based on frequency disturbance observation as described in claim 2, characterized in that, The step of generating a frequency compensation amount based on the frequency-related total disturbance estimate and the input gain includes: Based on the second state estimate and the input gain b Generate frequency compensation amount ω fc : 。 4. The control method for a grid-type energy storage converter based on frequency disturbance observation as described in claim 3, characterized in that, The step of superimposing the rated angular frequency, the fundamental angular frequency deviation, and the frequency compensation amount to obtain the output angular frequency includes: The frequency compensation amount ω fc Deviation Δ from the fundamental angular frequency ω 0 superposition, and introduce the rated angular frequency. ω ref The output angular frequency is obtained. ω : ； The step of integrating the output angular frequency to generate the synchronization angle includes: In the formula, Let be the synchronization angle at time t. for Synchronization angle at time, for The output angular frequency corresponding to the given moment.

5. The control method for a grid-type energy storage converter based on frequency disturbance observation as described in claim 1, characterized in that, include: Collect the three-phase output voltage, three-phase grid-connected current, and three-phase filter inductor current on the grid-connected side of the three-phase filter inductor; Calculate the actual active power and actual reactive power based on the three-phase output voltage and the three-phase grid current. The three-phase output voltage and the three-phase grid-connected current are subjected to a two-phase stationary coordinate transformation with unchanged amplitude to obtain the α-axis component and β-axis component of the output voltage, and the α-axis component and β-axis component of the grid-connected current, respectively. The actual active power is calculated according to the following formula. P and the actual reactive power Q : ； The active power deviation signal is generated according to the following formula. e P and the angular frequency deviation signal e ω : In the formula, P ref The active power reference value is... ω ref The rated angular frequency, ω The output angular frequency of the grid-type energy storage converter system is given.

6. The control method for a grid-type energy storage converter based on frequency disturbance observation as described in claim 5, characterized in that, The step of generating a switch drive signal based on the synchronization angle to control the switching transistors of the converter system includes: The actual output voltage amplitude is calculated based on the three-phase output voltage, and an output voltage amplitude reference is generated based on the actual reactive power, the reactive power reference value, the rated output voltage amplitude, and the actual output voltage amplitude. The output voltage amplitude reference satisfies the following: In the formula, D q The preset reactive power-voltage droop coefficient, τ This is the preset reactive power control proportional coefficient. V o This represents the actual output voltage amplitude. Q This represents the actual reactive power. Q ref This is a reference value for reactive power. V ref This is the rated output voltage amplitude; Based on the synchronization angle, the three-phase output voltage and the three-phase filter inductor current are subjected to a rotating coordinate transformation to obtain the d-axis and q-axis components of the output voltage and the d-axis and q-axis components of the filter inductor current. A current reference is generated using the voltage outer loop based on the output voltage amplitude reference and the d-axis and q-axis components of the output voltage; The modulation voltage component is generated using the inner current loop based on the current reference and the d-axis and q-axis components of the filter inductor current. Perform an inverse coordinate transformation on the modulated voltage components to obtain a three-phase modulated reference signal; Perform pulse width modulation (PWM) operations based on the three-phase modulation reference signal to generate a PWM signal; A switch drive signal is generated based on the pulse width modulation signal to control the power switch of the converter system to turn on and off.

7. A control system for a grid-type energy storage converter based on frequency disturbance observation, wherein the grid-type energy storage converter includes a converter system and a control system, and the control system provides switching drive signals to the converter system; The converter system includes: An energy storage unit provides input DC power, which is then converted and filtered by a three-phase converter bridge and an AC filter module before being connected to the power grid, achieving bidirectional power conversion between the energy storage unit and the power grid; the control system comprises: The deviation signal generation module generates an active power deviation signal based on the active power reference value and the actual active power, and generates an angular frequency deviation signal based on the rated angular frequency and the feedback output angular frequency. A frequency disturbance observation module generates a frequency-related total disturbance estimate based on the input gain, active power deviation signal, and angular frequency deviation signal. The frequency compensation and synchronization angle generation module generates the output angular frequency and synchronization angle based on the fundamental angular frequency deviation, the frequency-related total disturbance estimate, the input gain, and the rated angular frequency. A switch drive module generates a switch drive signal based on the synchronization angle to control the power switch transistor to turn on and off.

8. The control system for a grid-type energy storage converter based on frequency disturbance observation as described in claim 7, characterized in that, The control system includes: An output voltage sampling module acquires the three-phase output voltage and generates a three-phase output voltage signal; A grid-connected current sampling module, which collects three-phase grid-connected current and generates a three-phase grid-connected current signal; A filter inductor current sampling module is provided, which acquires the three-phase filter inductor current and generates a three-phase filter inductor current signal. A basic active power synchronization control module, which generates a basic angular frequency deviation based on the active power deviation signal; The reactive power-voltage control module generates an output voltage amplitude reference based on the actual reactive power, the reactive power reference value, the rated output voltage amplitude, and the actual output voltage amplitude. A dual closed-loop control module for voltage outer loop and current inner loop generates a modulated voltage component based on the output voltage amplitude reference, synchronization angle, three-phase output voltage signal and three-phase filter inductor current signal. The coordinate inverse transformation and modulation module performs coordinate inverse transformation on the modulation voltage component according to the synchronization angle to generate a three-phase modulation reference signal and a pulse width modulation signal.

9. The control system for a grid-type energy storage converter based on frequency disturbance observation as described in claim 7, characterized in that, The control system includes: Frequency disturbance observation module, the frequency disturbance observation module includes: The observation error generation unit, based on the active power deviation signal... e P and first state estimator Generate observation error signal ε It is expressed as follows: In the formula, the first state estimate Used to track active power deviation signals e P ; An input gain configuration unit generates an input gain representation as follows: In the formula, b For input gain, k δP The nominal small-signal gain is the change in power angle to the change in active power at the preset steady-state operating point. The first state estimation unit estimates the second state. An update is performed, as shown below: In the formula, s Represents a Laplace complex variable. G 2 represents the gain of the second observer. ω o This is the preset observer bandwidth; The second state estimation unit estimates the first state. An update is performed, as shown below: In the formula, G 1 represents the gain of the first observer. N The gain coefficient is a dimensionless coefficient. Total disturbance estimation output unit, the total disturbance estimation output unit outputs the second state estimate As the frequency-related total disturbance estimate Output, the second state estimate Used to estimate the total frequency-dependent disturbance acting on the active power synchronization control loop. f td Therefore, the frequency-dependent total disturbance estimate Represented as: 。 10. A grid-type energy storage converter based on frequency disturbance observation, characterized in that, include: The converter system and control system are connected, and the control system provides switching drive signals to the converter system. The converter system includes an energy storage unit that provides input DC power. The input DC power is converted by a three-phase converter bridge to obtain three-phase inductor current and three-phase output voltage, which are then connected to the power grid, thereby realizing bidirectional power conversion between the energy storage unit and the power grid.

11. A grid-type energy storage converter based on frequency disturbance observation as described in claim 10, characterized in that, The control system adopts the control method of the grid-type energy storage converter as described in any one of claims 1-6.

12. A grid-type energy storage converter based on frequency disturbance observation as described in claim 10, characterized in that, The control system integrates the control system of the grid-type energy storage converter as described in any one of claims 7-9.

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