Hybrid damping grid-connected inverter control method based on critical damping ratio design

Abstract

The invention discloses a hybrid damping grid-connected inverter control method based on critical damping ratio design. The hybrid damping grid-connected inverter control method comprises the steps of S1, designing an initial steady-state working point and designing LCL filter parameters; s2, designing parameters of a current outer loop controller; s3, reference resistance required by the grid-connected system is solved; s4, calculating a value range of a feedback coefficient of active damping; s5, drawing an equivalent passive damping coefficient curve based on the value range of the feedback coefficient, judging whether an effective positive damping range exists or not, and if not, returning to the step S1; s6, if yes, calculating the passive damping in the value range of the feedback coefficient; s7, calculating a mixed damping coefficient based on passive damping and active damping, and drawing a damping coefficient curve; and S8, verifying whether the curve meets the design requirement of the critical damping ratio or not. According to the method, the characteristics of low loss of active damping and simple parameter setting of passive damping are effectively combined, the control scheme is flexible, and high robustness can be kept under strong and weak power grids.

Description

Technical Field

[0001] This invention belongs to the field of grid-connected inverter control technology, and specifically relates to a hybrid damping grid-connected inverter control method based on critical damping ratio design. Background Technology

[0002] Against the backdrop of a global transition to renewable energy, increased grid impedance, frequent voltage fluctuations, and higher harmonic content have severely impacted the control performance of grid-connected three-phase inverters, posing challenges to system stability. To reduce high-order harmonics in the inverter output current, an LCL filter is typically used between the inverter and the grid. However, the inherent resonance of the LCL filter can lead to system instability, necessitating the application of active and passive damping methods in LCL filter-based converter systems.

[0003] Capacitor current feedback is one of the most stable active damping methods. Its advantages include no damping loss and no reduction in the high-frequency attenuation performance of the LCL filter, making it widely used in industry. However, the introduction of digital control delay limits the performance of active damping. As the grid impedance increases, the performance of active damping will no longer meet the requirements, affecting system stability. Unlike the complex implementation of active damping, passive damping is a simple and popular method. Typically, a resistor and capacitor are connected in series to suppress filter resonance, at the cost of increased damping loss and degraded attenuation performance.

[0004] Numerous solutions exist to address the digital control delay problem in active damping, typically involving adding various phase compensators, integrators, or using filters to extend the positive damping region in the state feedback loop. Various strategies also exist to address the shortcomings of passive damping schemes, primarily by adding circuit components or modifying the topology to bypass the fundamental and switching frequency components of the capacitor current. All these proposed solutions increase the complexity of the positive definite process of system parameters and the design of filter parameters. Therefore, considering both system cost and design efficiency, cost-effective traditional damping control schemes remain a commonly used approach in practical applications.

[0005] Chinese Patent Publication No. CN109327152A discloses a method for determining the critical damping parameters of a grid-connected current loop that includes digital control delay. The method involves the following steps: taking a single-inductor grid-connected converter as the controlled object, obtaining its vector model in a positive-sequence synchronous rotating coordinate system; employing a complex coefficient vector controller in the current loop to cancel the complex coefficient zeros of the controlled object; starting with digital control, directly including a one-step delay introduced by digital control in the current loop; further obtaining the open-loop transfer function of the current loop by approximating this delay element with a second-order Pade function; and finally, finding the controller gain that puts the system in a critical damping state as the optimal gain of the current loop by analyzing the root locus curve of the current loop. While this invention uses a complex coefficient vector controller to cancel the complex poles of the controlled object and uses a Pade function to approximate the time delay, it undoubtedly significantly increases the complexity of system parameter design. Summary of the Invention

[0006] The purpose of this invention is to provide a hybrid damping grid-connected inverter control method based on critical damping ratio design. The critical damping ratio is used as the design target for the system damping effect. By combining two traditional damping control schemes, it effectively combines the low loss of active damping with the simple parameter tuning of passive damping. The design is simple, the control scheme is flexible, and it can maintain strong robustness under both strong and weak power grids.

[0007] The technical solution of the present invention is as follows: On one hand, the present invention provides a control method for a hybrid damping grid-connected inverter based on critical damping ratio design, comprising the following steps: S1: Design the initial steady-state operating point, including determining the rated power and rated current of the grid-connected inverter, and designing the LCL filter parameters; S2: Design parameters for the outer loop current controller; S3: Solve for the reference resistance required by the grid-connected system based on the definition of critical damping ratio; S4: Calculate the range of values ​​for the feedback coefficient of active damping based on the steady-state requirements of the grid-connected system; S5: Plot the equivalent passive damping coefficient curve based on the range of the feedback coefficient, and determine whether there is an effective positive damping range. If not, return to step S1. S6: If it exists, take a value within the range of the feedback coefficient and calculate the required passive damping of the grid-connected system based on the critical resistance; S7: Calculate the hybrid damping coefficient based on passive and active damping, and plot the damping coefficient curve; S8: Verify whether the damping coefficient curve meets the design requirements of the critical damping ratio.

[0008] Preferably, step S2 designs the parameters of the outer current loop controller, including the proportional gain, resonant gain, and resonant term bandwidth. Based on these parameters, the transfer function of the QPR controller is designed.

[0009]

[0010] In the formula, The transfer function of the QPR controller used; This is the proportionality coefficient; The cutoff frequency; The resonant coefficient; The bandwidth of the resonant term; The fundamental angular frequency; It is a complex variable; This refers to the PWM modulation gain. This represents the inductance value on the inverter side of the LCL filter. This represents the mesh-side inductance value of the LCL filter.

[0011] Preferably, the grid-connected inverter is a three-phase voltage-source grid-connected inverter based on an LCL filter, and the reference resistor calculated in step S3 based on the definition of the critical damping ratio... Should meet:

[0012] In the formula, This represents the inductance value on the inverter side of the LCL filter. This refers to the capacitance value of the LCL filter; This represents the mesh-side inductance value of the LCL filter; This is the equivalent inductive reactance on the grid side; The critical damping coefficient is 0.28.

[0013] Preferably, the specific range of values ​​for the feedback coefficient of the active damping in step S4, based on the steady-state requirements of the grid-connected system, is as follows: Based on the phase margin constraint, amplitude margin constraint, and steady-state error constraint of the grid-connected system, the feedback coefficient of active damping is calculated. The range of values ​​for is expressed as:

[0014]

[0015]

[0016] In the formula, This refers to the PWM modulation gain. For active damping, the feedback coefficient is used. This represents the inductance value on the inverter side of the LCL filter. This represents the mesh-side inductance value of the LCL filter; To design the loop gain of the grid-connected system at the fundamental frequency; , The amplitude margin is designed based on the resonant frequency of the LCL filter; Phase margin required for grid-connected systems; The cutoff frequency; The resonant frequency; The switching frequency; For switching cycles; The fundamental frequency; Design parameters for the bandwidth of the resonant term.

[0017] Preferably, the passive damping required by the grid-connected system calculated in step S6 is expressed as follows:

[0018] In the formula, For passive damping; Used as a reference resistor; For active damping, the feedback coefficient is used. This refers to the PWM modulation gain. This refers to the capacitance value of the LCL filter; This represents the inductance value on the inverter side of the LCL filter. It is the resonant angular frequency.

[0019] Preferably, the calculation of the hybrid damping coefficient based on passive damping and active damping is as follows:

[0020] In the formula, This refers to the mixed damping coefficient; For passive damping; This represents the inductance value on the inverter side of the LCL filter. This refers to the capacitance value of the LCL filter; This represents the mesh-side inductance value of the LCL filter; This is the equivalent inductive reactance on the grid side; For active damping, the feedback coefficient is used. This is the PWM modulation gain.

[0021] On the other hand, the present invention provides a hybrid damping grid-connected inverter control system based on critical damping ratio design, including an initialization and parameter design module, a reference resistance calculation module, an effectiveness determination module, and a hybrid damping calculation and verification module; The initialization and parameter design module is used to design the initial steady-state operating point, including determining the rated power and rated current of the grid-connected inverter, and designing the parameters of the LCL filter and the current outer loop controller. The reference resistance calculation module is used to calculate the reference resistance required by the grid-connected system based on the definition of critical damping ratio. The effectiveness determination module is used to calculate the range of values ​​for the feedback coefficient of active damping according to the steady-state requirements of the grid-connected system, plot the equivalent passive damping coefficient curve based on the range of values ​​for the feedback coefficient, and determine whether there is an effective positive damping range; if so, it calculates the required passive damping of the grid-connected system by taking values ​​within the range of values ​​for the feedback coefficient and the critical resistance. The hybrid damping calculation and verification module is used to calculate the hybrid damping coefficient based on passive damping and active damping, plot the damping coefficient curve, and verify whether the damping coefficient curve meets the design requirements of the critical damping ratio.

[0022] Preferably, the control system is built on In the coordinate system, after the grid-side current passes through the QPR regulator, it undergoes coordinate transformation and sinusoidal pulse width modulation to generate a PWM drive signal to drive the switching of the bridge arm switches of the three-phase inverter.

[0023] In another aspect, the present invention also provides an electronic device, the electronic device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the hybrid damping grid-connected inverter control method based on critical damping ratio design as described in any embodiment of the present invention.

[0024] In another aspect, the present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the hybrid damping grid-connected inverter control method based on critical damping ratio design as described in any embodiment of the present invention.

[0025] Compared with the prior art, the present invention has the following technical effects: This invention proposes a hybrid damping grid-connected inverter control method based on critical damping ratio design. Using the critical damping coefficient introduced by the critical damping ratio scheme as a benchmark, it measures system robustness through the changing trend of the system damping coefficient curve, providing a new approach to the design of LCL-type grid-connected inverter control. By innovatively combining two traditional damping control schemes, it effectively integrates the flexibility of active damping with the high design efficiency of passive damping. Compared with existing damping control methods, this scheme offers higher design efficiency, more flexible control, uses less passive damping, achieves flattening of the LCL resonance peak, and exhibits better robustness under both strong and weak power grid conditions. Attached Figure Description

[0026] Figure 1 This is an overall flowchart of the hybrid damping grid-connected inverter control method based on critical damping ratio design described in this invention. Figure 2 This is the overall architecture diagram of the hybrid damping grid-connected inverter control method based on critical damping ratio design described in this invention; Figure 3 This is a block diagram of a passive damping current loop control based on a capacitor design. Figure 4 These are the equivalent critical damping curves plotted based on the critical damping ratio, and the equivalent passive damping curves plotted based on the active damping feedback coefficient. Figure 5 This is a graph showing the relationship between the damping coefficient and the grid impedance in the hybrid damping control method described in this invention. Figure 6 The Bode plots of the open-loop gain at different impedances using a hybrid damping scheme are shown. Figure 7 This is the experimental waveform of a single-phase circuit when the power grid inductive reactance changes to 0mH; Figure 8 The waveform of a single-phase circuit is shown when the inductive reactance of the power grid changes by 0.9 mH. Figure 9 This is the experimental waveform of a single-phase circuit when the grid inductive reactance changes to 3mH. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present application and with reference to the accompanying drawings.

[0028] Example 1 This embodiment provides a hybrid damping grid-connected inverter control method based on critical damping ratio design. Using the critical damping coefficient introduced by the critical damping ratio scheme as a benchmark, the design target for grid-connected system damping is clearly defined. By superimposing the damping coefficients, a corresponding reference resistor is introduced into the grid-connected system to ensure accurate flattening of the LCL resonant peak without generating unnecessary losses. (See reference...) Figure 1 , Figure 2 As shown, it includes the following steps: S1: Designing the initial steady-state operating point includes determining the rated power and rated current of the grid-connected inverter, and designing the LCL filter parameters according to the inverter-side current ripple requirements, the reactive power requirements absorbed by the filter capacitor, and the injected grid-connected current harmonic standard IEEE2014-1547.

[0029] S2: Design parameters for the outer loop current controller.

[0030] In a preferred embodiment of this invention, step S2 designs the parameters of the outer current loop controller, including the proportional gain, the resonant gain, and the resonant term bandwidth. Based on these parameters, the transfer function of the QPR controller is designed.

[0031]

[0032] In the formula, The transfer function of the QPR controller used; This is a proportional gain, used to obtain the optimal proportional element required by the system, based on the grid-connected system cutoff frequency. The loop gain at the location needs to be set; The cutoff frequency; The resonant coefficient is used to ensure that the system operates at the cutoff frequency. The phase lag characteristics at the point can meet the requirements, and the setting is based on the magnitude of the required amplitude gain of the system; This is the resonant term bandwidth, used to reduce sensitivity to fundamental frequency changes. It is set based on the requirements of the system's closed-loop cutoff frequency (usually determined at a gain of -3 dB). The fundamental angular frequency; These are the complex variables contained in the transfer function; This refers to the PWM modulation gain. This represents the inductance value on the inverter side of the LCL filter. This represents the mesh-side inductance value of the LCL filter.

[0033] S3: Solve for the reference resistance required by the grid-connected system based on the definition of critical damping ratio; In a preferred embodiment of this invention, the grid-connected inverter is a three-phase voltage-source grid-connected inverter based on an LCL filter. In step S3, the reference resistance is solved based on the critical damping ratio definition. This is a transformation based on the (series) passive damping coefficient formula, specifically the resistance value of the series passive resistor determined by the critical damping ratio. This resistance serves as a reference for hybrid damping design, meaning the reference resistor should satisfy the following:

[0034] In the formula, This represents the inductance value on the inverter side of the LCL filter. This refers to the capacitance value of the LCL filter; This represents the mesh-side inductance value of the LCL filter; This is the equivalent inductive reactance on the grid side; The critical damping coefficient is 0.28.

[0035] S4: Calculate the range of values ​​for the feedback coefficient of active damping based on the steady-state requirements of the grid-connected system.

[0036] In a preferred embodiment of this practice, step S4, which calculates the range of values ​​for the feedback coefficient of the active damping based on the steady-state requirements of the grid-connected system, specifically includes: To meet the dynamic performance requirements of the system, the phase margin constraint (PM), gain margin constraint (GM), and steady-state error (loop gain) should be designed before selecting the feedback coefficients. Constraints are then used to guide the design of feedback coefficients. The selection is as follows The constraint equation is the final derivation result, and the constraint equation curve (with) As the independent variable, The two-dimensional curve (with the dependent variable as the two-dimensional curve) constitutes Within the acceptable range, first select the suitable one. (Crossing frequency), further select as needed. The values ​​of are expressed as follows: the phase margin constraint, magnitude margin constraint, and steady-state error constraint based on the grid-connected system are:

[0037]

[0038]

[0039] In the formula, This refers to the PWM modulation gain. For active damping, the feedback coefficient is used. This represents the inductance value on the inverter side of the LCL filter. This represents the mesh-side inductance value of the LCL filter; To design the loop gain of the grid-connected system at the fundamental frequency; , The amplitude margin is designed based on the resonant frequency of the LCL filter; Phase margin required for grid-connected systems; The resonant frequency; The switching frequency; The cutoff frequency; For switching cycles; The fundamental frequency; To design parameters for the resonant term bandwidth, and to ensure sufficient gain for the PR regulator during grid frequency fluctuations, it is generally set to... It is 1 / 2.

[0040] S5: Plot the equivalent passive damping coefficient curve based on the range of the feedback coefficient, and determine whether there is an effective positive damping range. If not, return to step S1. S6: If it exists, take a value within the range of the feedback coefficient and calculate the required passive damping of the grid-connected system based on the critical resistance; In a preferred embodiment of this invention, step S6, which calculates the required passive damping of the grid-connected system, is expressed as follows:

[0041] In the formula, For passive damping; Used as a reference resistor; For active damping, the feedback coefficient is used. This refers to the PWM modulation gain. This refers to the capacitance value of the LCL filter; This represents the inductance value on the inverter side of the LCL filter. It is the resonant angular frequency.

[0042] Specifically, the main idea of ​​the passive damping calculation is as follows: at the resonant frequency, the active equivalent parallel resistance is converted into a series resistance, which is then superimposed with the passive series resistance, and the final superimposed value is the reference resistance.

[0043] Therefore, the derivation process of the above formula is as follows: At the resonant frequency At this point, the equivalent impedance of the capacitor in series with the resistor is ,in, A capacitor connected in series with a resistor; The imaginary unit is used; capacitors in parallel with resistors ( The equivalent admittance is ,in, Let the capacitor and resistor be connected in parallel; let them be in... For the same damping effect on the system, the following must be satisfied:

[0044] In the formula, For real part; This is the equivalent impedance of the capacitor in series with the resistor; For capacitors and resistors in parallel ( (Equivalent) admittance.

[0045] This formula is the equivalent conversion formula for series and parallel resistances at the resonant frequency. and (relationship).

[0046] The capacitor current feedback coefficient The relationship with the equivalent resistance is expressed as:

[0047] By combining the above formulas, we can obtain the equivalent passive series resistance of the feedback coefficient at the resonant frequency (the minuend in the passive damping calculation formula).

[0048] S7: Calculate the hybrid damping coefficient based on passive and active damping, and plot the damping coefficient curve.

[0049] As a preferred embodiment of this invention, the calculation of the hybrid damping coefficient based on passive damping and active damping is specifically as follows:

[0050] In the formula, This refers to the mixed damping coefficient; For passive damping; This represents the inductance value on the inverter side of the LCL filter. This refers to the capacitance value of the LCL filter; This represents the mesh-side inductance value of the LCL filter; This is the equivalent inductive reactance on the grid side; For active damping, the feedback coefficient is used. This is the PWM modulation gain.

[0051] Specifically, the passive damping coefficient is expressed as:

[0052] In the formula, , These represent the passive damping coefficients when the system uses a capacitor in series with a resistor and a capacitor in parallel with a resistor, respectively. This refers to the resistance value of the resistor used. For example... Figure 3 As shown, this is a passive damping current loop control scheme based on capacitor design.

[0053] The active damping scheme can be derived as passive damping of the equivalent capacitance in parallel with the resistance and analyzed accordingly:

[0054] In the formula , , The equivalent passive damping coefficients for active damping schemes such as capacitor current, capacitor voltage, and grid current feedback are respectively. , For PWM modulation gain, This represents the feedback coefficient for the active damping scheme.

[0055] Specifically, the capacitor current feedback scheme offers the best damping effect, is insensitive to changes in grid impedance (strong robustness), and requires no differentiation calculations. The capacitor voltage feedback scheme may reuse a voltage sensor (current-saving sensor), but it requires differentiation calculations, which significantly amplifies measurement noise, resulting in generally poor performance and stability. The grid current feedback scheme requires no additional sensors (reusing a grid-connected current sensor), is simple to implement, but has relatively weak damping effect, its performance is highly dependent on grid impedance (poor robustness), and it may be unstable or require adaptive control when the grid changes.

[0056] In summary, due to the optimal damping effect, the strongest robustness (unaffected by power grid changes), and the avoidance of noise problems caused by differentiation, this embodiment preferably constructs a hybrid damping scheme by combining the active damping scheme of capacitor current feedback with the passive damping scheme of capacitor series resistance. By leveraging the complementarity of the damping coefficient curve trends, an active damping scheme of current feedback in this branch is introduced on the basis of passive damping of capacitor series resistance, and a new damping coefficient is obtained through hybrid damping control.

[0057] like Figure 4 As shown, the red and blue curves represent the passive resistance (parallel and series) required for the critical damping ratio, and their damping coefficients vary with the grid inductive reactance (increasing in parallel and decreasing in series). The yellow and black curves ( The curves are equivalent passive damping (parallel and series) curves for active damping. It can be seen that the required critical damping coefficient cannot be achieved by using only active damping scheme, so passive resistance needs to be added.

[0058] S8: Verify whether the damping coefficient curve meets the design requirements of the critical damping ratio. Specifically, verify that the new damping coefficient is achieved when the grid inductive reactance is 0 ( When this condition is met, the following conditions must be satisfied: If the conditions are not met, return to step S6; if the conditions are met, the design of the control method is completed.

[0059] To verify the effectiveness and superiority of the method provided in this embodiment, some specific examples are provided below: like Figure 5 As shown, the red curve represents the traditional passive damping scheme, and the black curve represents the hybrid damping scheme. It can be seen that the damping coefficient of the traditional passive damping scheme is easily affected by changes in grid impedance (the damping effect decreases significantly as the grid inductive reactance increases), while the damping coefficient curve of the hybrid damping scheme used in this embodiment is almost unaffected, and the system robustness is better than that of the traditional passive damping scheme.

[0060] like Figure 6-9As shown, after adopting the hybrid damping scheme described in this embodiment, the system stability is basically unaffected by changes in grid inductive reactance, and it exhibits good current quality waveforms in different resonant frequency ranges.

[0061] Example 2 Accordingly, this embodiment provides a hybrid damping grid-connected inverter control system based on critical damping ratio design, used to implement the hybrid damping grid-connected inverter control method based on critical damping ratio design as described in Embodiment 1, including an initialization and parameter design module, a reference resistance calculation module, an effectiveness determination module, and a hybrid damping calculation and verification module.

[0062] The initialization and parameter design module is used to design the initial steady-state operating point, including determining the rated power and rated current of the grid-connected inverter, and designing the parameters of the LCL filter and the current outer loop controller.

[0063] The reference resistance calculation module is used to solve for the reference resistance required by the grid-connected system based on the definition of critical damping ratio.

[0064] The effectiveness determination module is used to calculate the range of values ​​for the feedback coefficient of active damping based on the steady-state requirements of the grid-connected system, plot the equivalent passive damping coefficient curve based on the range of values ​​for the feedback coefficient, and determine whether there is an effective positive damping range. If so, the required passive damping of the grid-connected system is calculated by taking values ​​within the range of values ​​for the feedback coefficient and the critical resistance.

[0065] The hybrid damping calculation and verification module is used to calculate the hybrid damping coefficient based on passive damping and active damping, plot the damping coefficient curve, and verify whether the damping coefficient curve meets the design requirements of the critical damping ratio.

[0066] As a preferred embodiment of this practice, the control system is established on In the coordinate system, after the grid-side current passes through the QPR regulator, it undergoes coordinate transformation and sinusoidal pulse width modulation to generate a PWM drive signal to drive the switching of the bridge arm switches of the three-phase inverter.

[0067] Example 3 This embodiment provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the hybrid damping grid-connected inverter control method based on critical damping ratio design as described in Embodiment 1 of this invention.

[0068] Example 4 This embodiment provides a computer-readable storage medium storing a computer program thereon. When the computer program is executed by a processor, it implements the hybrid damping grid-connected inverter control method based on critical damping ratio design as described in Embodiment 1 of this invention.

[0069] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, A and B simultaneously, or B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0070] Those skilled in the art will recognize that the units and algorithm steps described in the embodiments disclosed herein can be implemented using electronic hardware, computer software, or a combination of electronic hardware and software. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0071] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0072] In the several embodiments provided in this application, any function, if implemented as a software functional unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0073] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A control method for a hybrid damped grid-connected inverter based on critical damping ratio design, characterized in that, Includes the following steps: S1: Design the initial steady-state operating point, including determining the rated power and rated current of the grid-connected inverter, and designing the LCL filter parameters; S2: Design parameters for the outer loop current controller; S3: Solve for the reference resistance required by the grid-connected system based on the definition of critical damping ratio; S4: Calculate the range of values ​​for the feedback coefficient of active damping based on the steady-state requirements of the grid-connected system; S5: Plot the equivalent passive damping coefficient curve based on the range of the feedback coefficient, and determine whether there is an effective positive damping range. If not, return to step S1. S6: If it exists, take a value within the range of the feedback coefficient and calculate the required passive damping of the grid-connected system based on the critical resistance; S7: Calculate the hybrid damping coefficient based on passive and active damping, and plot the damping coefficient curve; S8: Verify whether the damping coefficient curve meets the design requirements of the critical damping ratio.

2. The control method for a hybrid damped grid-connected inverter based on critical damping ratio design according to claim 1, characterized in that, Step S2 involves designing the parameters of the outer current loop controller, including the proportional gain, resonant gain, and resonant term bandwidth. Based on these parameters, the transfer function of the QPR controller is designed. In the formula, The transfer function of the QPR controller used; This is the proportionality coefficient; The cutoff frequency; The resonant coefficient; The bandwidth of the resonant term; The fundamental angular frequency; It is a complex variable; This refers to the PWM modulation gain. This represents the inductance value on the inverter side of the LCL filter. This represents the mesh-side inductance value of the LCL filter.

3. The control method for a hybrid damped grid-connected inverter based on critical damping ratio design according to claim 1, characterized in that, The grid-connected inverter is a three-phase voltage-source grid-connected inverter based on an LCL filter. The reference resistor calculated in step S3 based on the definition of the critical damping ratio... It should meet the following requirements: In the formula, This represents the inductance value on the inverter side of the LCL filter. This refers to the capacitance value of the LCL filter; This represents the mesh-side inductance value of the LCL filter; This is the equivalent inductive reactance on the grid side; The critical damping coefficient is 0.

28.

4. The control method for a hybrid damped grid-connected inverter based on critical damping ratio design according to claim 1, characterized in that, Step S4 calculates the range of values ​​for the feedback coefficient of the active damping based on the steady-state requirements of the grid-connected system. Based on the phase margin constraint, amplitude margin constraint, and steady-state error constraint of the grid-connected system, the feedback coefficient of active damping is calculated. The range of values ​​for is expressed as: In the formula, This refers to the PWM modulation gain. For active damping, the feedback coefficient is used. This represents the inductance value on the inverter side of the LCL filter. This represents the mesh-side inductance value of the LCL filter; To design the loop gain of the grid-connected system at the fundamental frequency; , The amplitude margin is designed based on the resonant frequency of the LCL filter; Phase margin required for grid-connected systems; The cutoff frequency; The resonant frequency; The switching frequency; For switching cycles; The fundamental frequency; Design parameters for the bandwidth of the resonant term.

5. The control method for a hybrid damped grid-connected inverter based on critical damping ratio design according to claim 1, characterized in that, Step S6 calculates the required passive damping for the grid-connected system, expressed as: In the formula, For passive damping; Used as a reference resistor; For active damping, the feedback coefficient is used. This refers to the PWM modulation gain. This refers to the capacitance value of the LCL filter; This represents the inductance value on the inverter side of the LCL filter. It is the resonant angular frequency.

6. The control method for a hybrid damped grid-connected inverter based on critical damping ratio design according to claim 1, characterized in that, The specific calculation of the hybrid damping coefficient based on passive and active damping is as follows: In the formula, This refers to the mixed damping coefficient; For passive damping; This represents the inductance value on the inverter side of the LCL filter. This refers to the capacitance value of the LCL filter; This represents the mesh-side inductance value of the LCL filter; This is the equivalent inductive reactance on the grid side; For active damping, the feedback coefficient is used. This is the PWM modulation gain.

7. A hybrid damping grid-connected inverter control system based on critical damping ratio design, characterized in that, The system is used to implement the hybrid damping grid-connected inverter control method based on critical damping ratio design as described in any one of claims 1 to 6, including an initialization and parameter design module, a reference resistance calculation module, an effectiveness determination module, and a hybrid damping calculation and verification module; The initialization and parameter design module is used to design the initial steady-state operating point, including determining the rated power and rated current of the grid-connected inverter, and designing the parameters of the LCL filter and the current outer loop controller. The reference resistance calculation module is used to calculate the reference resistance required by the grid-connected system based on the definition of critical damping ratio. The effectiveness determination module is used to calculate the range of values ​​for the feedback coefficient of active damping based on the steady-state requirements of the grid-connected system, plot the equivalent passive damping coefficient curve based on the range of values ​​for the feedback coefficient, and determine whether there is an effective positive damping range. If it exists, take a value within the range of the feedback coefficient and calculate the required passive damping of the grid-connected system based on the critical resistance; The hybrid damping calculation and verification module is used to calculate the hybrid damping coefficient based on passive damping and active damping, plot the damping coefficient curve, and verify whether the damping coefficient curve meets the design requirements of the critical damping ratio.

8. The hybrid damping grid-connected inverter control system based on critical damping ratio design according to claim 7, characterized in that, The control system is built on In the coordinate system, after the grid-side current passes through the QPR regulator, it undergoes coordinate transformation and sinusoidal pulse width modulation to generate a PWM drive signal to drive the switching of the bridge arm switches of the three-phase inverter.

9. An electronic device, the electronic device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, when the processor executes the computer program, it implements the hybrid damping grid-connected inverter control method based on critical damping ratio design as described in any one of claims 1 to 6.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the hybrid damping grid-connected inverter control method based on critical damping ratio design as described in any one of claims 1 to 6.

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