New energy converter voltage frequency support method and system based on fractional order matching control

Abstract

The invention relates to the technical field of power grid control, in particular to a new energy converter voltage frequency supporting method and system based on fractional order matching control, and the method comprises the steps: configuring rated operation parameters of a converter; collecting operation data of the new energy converter, and calculating an instantaneous power difference of a DC bus; constructing a fractional order transfer function, calculating an additional frequency regulating variable according to the instantaneous power difference, generating an AC port output frequency reference value, and transmitting the AC port output frequency reference value to an outer loop controller to generate a PWM signal; calculating the current available reactive capacity of the converter according to the operation data in combination with the converter, and calculating a reactive voltage droop coefficient; a reactive current reference value is calculated through a second fractional order controller; and adjusting the active power output of the converter according to the PWM signal, and controlling the reactive power of the converter according to the reactive current reference value. According to the invention, by introducing the fractional order control and the adaptive strategy, the dynamic stability and the adaptive capability of the voltage frequency support of the converter are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of power grid control technology, and in particular to a method and system for supporting the voltage and frequency of a new energy converter based on fractional-order matching control. Background Technology

[0002] Driven by the "dual-carbon" strategic goal, the scale of new energy power generation, represented by wind power and photovoltaics, continues to expand. These units are generally connected to the grid through power electronic converters. Based on different control characteristics, the control strategies of new energy converters can be mainly divided into two categories: "grid-following" and "grid-building." Grid-following control relies on phase-locked loops to track the grid voltage phase, making the converter behave as a controlled current source. Although it can achieve maximum power point tracking operation, it cannot actively support the grid voltage and frequency. On the other hand, grid-building control simulates the operating mechanism of a synchronous generator, enabling the converter to have voltage source characteristics. It can provide necessary inertia and reactive power support to the grid while outputting maximum power, thereby effectively improving the stability of the system. As the penetration rate of new energy continues to increase, the equivalent inertia level of the grid continues to decrease. Therefore, grid-building control technology has become the key to ensuring the safe and stable operation of the new power system.

[0003] Currently, mainstream grid-based control methods include droop control, virtual synchronous machine control, and their derived matching control. These methods can achieve predetermined power transmission during steady-state grid operation and participate in transient regulation of the grid to some extent. However, the core control components of these existing strategies are generally based on traditional integer-order calculus theory, with relatively fixed response mechanisms and limited dynamic adjustment capabilities. When facing complex transient processes such as grid voltage drops and frequency fluctuations, traditional integer-order controllers struggle to achieve an optimal balance between response speed and stability, often exhibiting slow response or overshoot oscillations. This results in insufficient active and reactive power support capabilities, and there is an unfavorable coupling effect between the two, ultimately limiting their application potential in improving the dynamic stability of high-proportion renewable energy grids. Summary of the Invention

[0004] In view of at least one of the above technical problems, the present invention provides a voltage and frequency support method and system for new energy converters based on fractional-order matching control, which solves the technical problem that existing new energy converter access methods do not have the ability to adapt to grid fluctuations, and further provides voltage and frequency support for voltage and frequency fluctuations.

[0005] This invention provides a method for supporting the voltage and frequency of a new energy converter based on fractional-order matched control, comprising the following steps:

[0006] Configure the rated operating parameters of the converter system, and initialize the first fractional-order controller of the active frequency matching control loop and the second fractional-order controller of the reactive voltage control loop;

[0007] Collect operating data from the new energy converter and calculate the instantaneous power difference between the two ends of the DC bus;

[0008] Construct a fractional transfer function, calculate the additional frequency adjustment based on the instantaneous power difference, and superimpose the additional frequency adjustment with the rated frequency of the power grid to generate the output frequency reference value of the AC port of the converter.

[0009] The output frequency reference value is sent to the outer loop controller of the converter, and a PWM signal is generated to drive the power switching devices of the converter through pulse width modulation.

[0010] Based on the operating data and the apparent power capacity limit of the converter, the current available reactive power capacity of the converter is calculated, and the reactive voltage droop coefficient is calculated based on the reactive power capacity.

[0011] Based on the reactive voltage droop coefficient, the preset rated voltage reference value, and the operating data, the reactive current reference value is calculated by the second fractional-order controller.

[0012] The active power output of the converter is adjusted according to the PWM signal, and the reactive current reference value is used to control the converter to inject or absorb the corresponding reactive power into the grid.

[0013] In some embodiments of the present invention, the fractional transfer function is constructed by a first fractional controller based on capacitor voltage, including the following steps performed within the first fractional controller:

[0014] Obtain the correspondence between the voltage change of the DC bus capacitor and the instantaneous power difference, and simulate the rotor motion equation of the synchronous generator to establish an integer-order active frequency control equation.

[0015] The integer-order differential operator in the active frequency control equation is replaced with a fractional-order differential operator to form a fractional-order active frequency control matching equation.

[0016] Based on the active frequency control matching equation, the fractional transfer function with the instantaneous power difference as input and the additional frequency adjustment as output is derived.

[0017] In some embodiments of the present invention, obtaining the reactive current reference value according to the second fractional-order controller includes:

[0018] Based on the real-time output active power of the converter and the upper limit of the apparent power capacity in the operating data, calculate the currently available reactive power capacity;

[0019] Based on the reactive power capacity and the allowable range of converter port voltage, the reactive power droop coefficient is calculated.

[0020] Based on the reactive voltage droop coefficient and the correspondence between the real-time voltage of the converter port in the operating data and the rated voltage reference value, a deviation signal for reactive voltage control is generated.

[0021] The deviation signal is input to the second fractional-order controller for fractional-order calculus and integrator operations, and the reactive current reference value is output. The second fractional-order controller is a fractional-order PI controller. λ Controller.

[0022] In some embodiments of the present invention, the implementation of the supporting method is based on a unified converter control architecture, and the integration and execution process of the control architecture includes:

[0023] Construct a control architecture that integrates fractional-order active frequency control, fractional-order reactive voltage control, and voltage-current dual-loop control.

[0024] The change in the capacitor voltage of the DC bus is obtained, and in the control architecture, the output frequency reference value of the AC port of the converter is generated based on the first fractional-order controller and the change in the capacitor voltage.

[0025] In the control architecture, the reactive current reference value is calculated based on the second fractional-order controller, and the virtual internal potential reference value of the AC device is generated based on the reactive current reference value.

[0026] The virtual internal potential reference value is calculated based on the preset virtual impedance to obtain the voltage reference value of the voltage and current dual-loop control loop, and the PWM signal is generated to drive the power conversion of the converter.

[0027] The fractional-order active frequency control loop is implemented by the first fractional-order controller, the fractional-order reactive voltage control loop is implemented by the second fractional-order controller, and the voltage and current dual-loop control loop is implemented by the voltage loop controller and the current loop controller.

[0028] In some embodiments of the present invention, a fractional-order active frequency control matching equation is formed, including:

[0029] The integer-order active frequency control equations include ;

[0030] Replacing the integer-order differential operators in the active frequency control equation with fractional-order differential operators forms a fractional-order active frequency control matching equation. ;

[0031] Where C is the DC bus capacitance of the converter, U dc0 The rated voltage of the DC bus, u dc P represents the real-time voltage value of the DC bus. re For the actual power output of the new energy converter, P out The active power output of the converter is denoted by N, which represents the matching coefficient from DC voltage to AC frequency. θ is the output phase of the converter port, and λ is the fractional order.

[0032] In some embodiments of the present invention, the fractional transfer function includes:

[0033] ;

[0034] Among them, the intermediate variable K P =3U o ·U g / X, U g U represents the grid voltage amplitude. o Let X be the output voltage of the converter, X be the sum of the inductance of the converter filter and the line inductance, and S be the Laplace transform operator.

[0035] In some embodiments of the present invention, calculating the currently available reactive power capacity includes:

[0036] Construct the reactive power capacity ;

[0037] Among them, S rate P is the rated capacity of the new energy converter. out Q is the active power output of the converter. s The remaining currently available reactive power capacity of the converter.

[0038] In some embodiments of the present invention, calculating the reactive voltage droop coefficient includes:

[0039] The reactive voltage droop coefficient ;

[0040] Among them, K q U is the reactive voltage droop coefficient of the converter at any given time. o，L U is the lower limit of the normal range of the converter output voltage. n This is the rated value of the output voltage of the converter.

[0041] In some embodiments of the present invention, based on the droop characteristics, reactive voltage support is further achieved, and the generation of a deviation signal for reactive voltage control includes:

[0042] Constructing equations ;

[0043] Where E is the virtual internal potential of the converter, and K q Let k be the reactive voltage droop coefficient. v The reactive power integral coefficient, Q, is set manually. ref E is the reactive power setpoint for the converter. o Q is the corresponding output internal potential. out U is the real-time value of the reactive power of the converter, and U is the real-time effective value of the converter port voltage.

[0044] In some embodiments of the present invention, obtaining the reactive current reference value according to the second fractional-order controller includes:

[0045] Constructing the fractional-order transfer function of reactive voltage ;

[0046] Among them, U g X represents the grid voltage amplitude. g Here, S is the reactance of the connecting line, S is the Laplace transform operator, ΔE is the increment of the virtual internal potential of the converter, and ΔQ is the value of the reactance of the connecting line. out This represents the increment of the reactive power of the converter.

[0047] This invention also provides a voltage and frequency support system for a new energy converter based on fractional-order matched control, comprising:

[0048] The initial configuration module configures the rated operating parameters of the converter system and initializes the first fractional-order controller of the active frequency matching control loop and the second fractional-order controller of the reactive voltage control loop.

[0049] The data acquisition and calculation module collects the operating data of the new energy converter and calculates the instantaneous power difference between the two ends of the DC bus.

[0050] The active power signal generation module constructs a fractional transfer function, calculates an additional frequency adjustment based on the instantaneous power difference, and superimposes the additional frequency adjustment with the rated frequency of the power grid to generate an output frequency reference value for the AC port of the converter; the output frequency reference value is sent to the outer loop controller of the converter, and a PWM signal for driving the power switching devices of the converter is generated through pulse width modulation.

[0051] The reactive power reference calculation module calculates the current available reactive power capacity of the converter based on the operating data and the apparent power capacity limit of the converter, and calculates the reactive voltage droop coefficient based on the reactive power capacity; based on the reactive voltage droop coefficient, the preset rated voltage reference value and the operating data, the reactive current reference value is calculated by the second fractional-order controller.

[0052] The power support module adjusts the active power output of the converter according to the PWM signal, and controls the converter to inject or absorb corresponding reactive power into the grid according to the reactive current reference value.

[0053] The beneficial effects of this invention are as follows: This invention introduces a fractional-order transfer function into the active power frequency control loop and employs a fractional-order PI control function in the reactive power voltage control loop. λ The controller enables the converter to achieve faster and smoother power regulation when the power grid experiences power disturbances or voltage fluctuations, effectively avoiding severe power and frequency oscillations, thereby significantly improving the transient process quality of the converter's participation in grid regulation and the overall system stability. By calculating the available reactive power capacity of the converter in real time and adaptively adjusting the reactive voltage droop coefficient accordingly, the converter can intelligently allocate its reactive power support capacity according to its actual operating status. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a schematic diagram illustrating the steps of the new energy converter voltage and frequency support method based on fractional-order matching control in an embodiment of the present invention.

[0056] Figure 2 This is a flowchart of the first fractional-order controller based on capacitor voltage in an embodiment of the present invention;

[0057] Figure 3 This is a flowchart illustrating the steps of obtaining the reactive current reference value according to the second fractional-order controller in an embodiment of the present invention.

[0058] Figure 4 This is a flowchart illustrating the integration and execution process of the control architecture described in this embodiment of the invention.

[0059] Figure 5 This is a diagram of the fractional-order active frequency matching control loop based on capacitor voltage in an embodiment of the present invention;

[0060] Figure 6 This embodiment of the invention is based on fractional PI. λ Reactive voltage control circuit diagram of the controller;

[0061] Figure 7 This is a general control block diagram of a new energy converter based on fractional-order matching control in an embodiment of the present invention. Detailed Implementation

[0062] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0063] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0065] This invention provides a method such as Figures 1 to 7 The voltage and frequency support method for new energy converters based on fractional-order matched control, as shown, includes the following steps:

[0066] Configure the rated operating parameters of the converter system, and initialize the first fractional-order controller of the active frequency matching control loop and the second fractional-order controller of the reactive voltage control loop;

[0067] Collect operating data from the new energy converter and calculate the instantaneous power difference between the two ends of the DC bus;

[0068] Construct a fractional transfer function, calculate the additional frequency regulation based on the instantaneous power difference, and superimpose the additional frequency regulation with the rated frequency of the power grid to generate the output frequency reference value of the AC port of the converter.

[0069] The output frequency reference value is sent to the outer loop controller of the converter, and a PWM signal is generated to drive the power switching devices of the converter through pulse width modulation.

[0070] Based on the operating data and the apparent power capacity limit of the converter, the current available reactive power capacity of the converter is calculated, and the reactive voltage droop factor is calculated based on the reactive power capacity.

[0071] Based on the reactive voltage droop coefficient, the preset rated voltage reference value, and the operating data, the reactive current reference value is calculated by the second fractional-order controller.

[0072] The active power output of the converter is adjusted according to the PWM signal, and the reactive power is injected into or absorbed by the converter into the grid according to the reactive current reference value.

[0073] First, the rated operating parameters of the converter are configured, such as the rated DC bus voltage, AC rated frequency and voltage. Then, the parameters of the first and second fractional-order controllers are initialized, laying the foundation for the fractional-order control algorithm and ensuring that the control system has performance that surpasses traditional integer-order control. Subsequently, the system enters a real-time operation cycle, continuously collecting operating data such as DC bus voltage, AC port voltage and current through sensors, and calculating the instantaneous power difference between the two ends of the DC bus. The instantaneous power difference reflects the power surplus or deficit status of the power grid, acting as an early warning signal and providing the most direct and rapid input basis for frequency support.

[0074] Then, the system inputs the instantaneous power difference into a preset fractional-order transfer function, i.e., the first fractional-order controller. Compared with the traditional integer-order controller, the fractional-order design has more flexible adjustment capabilities in the frequency domain, and can simultaneously improve the transient and steady-state performance of the system. The fractional-order transfer function outputs a smooth additional frequency adjustment, which, after being superimposed with the grid rated frequency, generates the output frequency reference value of the converter's AC port. This simulates and optimizes the inertial response of the synchronous generator, enabling the converter to adjust its output frequency quickly and smoothly when the grid frequency fluctuates, thereby guiding the change in active power and forming inertial support with excellent dynamic quality for the grid frequency. The frequency reference value is then sent to the outer loop controller, and finally, through PWM modulation, a drive signal is generated to control the active power output of the converter.

[0075] While providing frequency support, the system first calculates the available reactive power capacity based on the real-time active power output of the converter and its rated apparent power capacity, achieving a real-time and accurate assessment of the converter's own reactive power support capability. Then, based on the available reactive power capacity, the system adaptively calculates the reactive voltage droop coefficient, enabling the converter to intelligently adjust the voltage support level according to its own capacity reserves. It actively supports the converter when capacity is sufficient and smoothly transitions when capacity is tight, thereby maximizing the reactive power support effect and avoiding sudden changes in operating points while ensuring equipment safety. Next, the system uses the reactive voltage droop coefficient and the deviation between the acquired port voltage and the rated value to generate a control signal, which is input to the second fractional-order controller. The fractional-order controller performs more refined fractional-order calculus calculations on the deviation and outputs a reactive current reference value, achieving fast, accurate, and shock-free voltage compensation. Ultimately, the system controls the converter to inject or absorb the corresponding reactive power based on this reactive current reference value, working in conjunction with the aforementioned active frequency support to achieve efficient, reliable, and intelligent comprehensive support for grid voltage and frequency, significantly improving the operational stability of high-proportion renewable energy grids.

[0076] In some embodiments of the present invention, such as Figure 2 As shown, the fractional-order transfer function is constructed using a first fractional-order controller based on the capacitor voltage, which includes the following steps within the first fractional-order controller:

[0077] The relationship between the voltage change of the DC bus capacitor and the instantaneous power difference is obtained, and the rotor motion equation of the synchronous generator is simulated to establish an integer order active frequency control equation.

[0078] The integer-order differential operators in the active frequency control equation are replaced with fractional-order differential operators to form a fractional-order active frequency control matching equation.

[0079] Based on the active frequency control matching equation, a fractional transfer function with instantaneous power difference as input and additional frequency adjustment as output is derived.

[0080] First, a control foundation is established based on the physical characteristics of the DC bus capacitor. By analyzing the physical relationship between the rate of change of voltage on the DC bus capacitor and the net power flowing into and out of the capacitor, i.e., the instantaneous power difference, and drawing on the mathematical model of the rotor motion equation of a traditional synchronous generator, an integer-order active frequency control equation is established. This provides a clear physical basis and control objective for the controller, ensuring the predictability of system behavior. However, traditional integer-order active frequency control equations have inherent limitations in dynamic response performance; their response characteristics are relatively fixed, making it difficult to simultaneously coordinate response speed and stability.

[0081] Therefore, in this embodiment, the integer-order differential operator in the above integer-order equation is replaced with a fractional-order differential operator, thereby forming a fractional-order active frequency control matching equation. The fractional order is introduced as an adjustable dimension. Compared with the traditional integer-order operator, the fractional-order differential operator can describe the dynamic process of the system more precisely. Its unique memory characteristics enable the controller to adjust the damping degree and response speed of the system at the same time, thereby breaking the contradiction between speed and stability that the integer-order controller must make.

[0082] Finally, based on the fractional-order active power frequency control matching equation, a fractional-order transfer function with instantaneous power difference as input signal and additional frequency adjustment as output signal is derived. The fractional-order transfer function is the core mathematical expression of the first fractional-order controller. In the actual implementation of digital control systems, this fractional-order transfer function can be transformed into a high-order integer-order difference equation or state-space equation that can be executed in a microprocessor through various fractional-order calculus approximation algorithms, such as the Oustaloup filter method. The resulting first fractional-order controller enables the converter to exhibit both fast and stable frequency support characteristics when responding to grid power disturbances, effectively suppressing power and frequency oscillations and significantly improving the dynamic performance of the system.

[0083] In some embodiments of the present invention, such as Figure 3 As shown, the reactive current reference value obtained according to the second fractional-order controller includes:

[0084] Calculate the currently available reactive power capacity based on the real-time output active power and apparent power capacity limit of the converter in the operating data;

[0085] Calculate the reactive voltage droop coefficient based on the reactive capacity and the allowable range of converter port voltage;

[0086] Based on the reactive voltage droop coefficient and the correspondence between the real-time voltage of the converter port and the reference value of the rated voltage in the operating data, a deviation signal for reactive voltage control is generated.

[0087] The deviation signal is input to the second fractional-order controller, which performs fractional-order calculus and outputs a reactive current reference value. The second fractional-order controller is a fractional-order PI controller. λ Controller.

[0088] Specifically, based on the real-time output active power and apparent power capacity limit of the converter in the operating data, the currently available reactive power capacity is calculated. The apparent power capacity of the converter is a constant value. When the real-time active power output occupies a portion of the capacity, the remaining capacity can be used for reactive power support. The currently available reactive power capacity can be obtained through simple algebraic calculations, ensuring that the reactive power support provided by the converter under any operating condition, whether it is full load or light load operation, will not exceed its own physical capacity range. This fundamentally guarantees the safe operation of the equipment and maximizes the utilization of capacity.

[0089] After knowing the available reactive power capacity, the reactive power voltage droop factor is adaptively calculated based on the calculated reactive power capacity and the allowable operating range of the converter port voltage. Traditional fixed droop factors may cause overload or response rigidity when the converter capacity is limited. However, the adaptive calculation method in this embodiment can dynamically adjust the slope of the droop curve. For example, when the available reactive power capacity is sufficient, the system will adopt a larger droop factor, and the converter will make strong reactive power compensation for small voltage deviations. Conversely, when the available capacity is tight, a smaller droop factor will be automatically adopted, making the support behavior more gentle and conservative. This gives the converter's reactive power support behavior an intelligent adjustment function, which can actively maintain voltage stability when the capacity is sufficient and smoothly transition when the capacity is limited. It effectively avoids control abrupt changes or system instability caused by reaching the capacity limit, and greatly enhances the robustness of control.

[0090] Then, based on the adaptively calculated reactive voltage droop coefficient and the deviation between the real-time voltage of the converter port and the rated voltage reference value in the operating data, a deviation signal for reactive voltage control is generated. The difference between the actual voltage state and the desired state is scaled by a reactive voltage droop coefficient determined by its own capacity, and transformed into a preliminary reactive power demand command. This integrates the voltage demand of the external power grid with the support capacity of the internal converter, providing a reasonable input reference for subsequent control.

[0091] Finally, this deviation signal is input to the second fractional-order controller, which is a fractional-order PI controller. λ The controller performs fractional-order calculus calculations to output the final reactive current reference value; unlike traditional integer-order PI controllers, fractional-order PI controllers... λThe controller introduces an adjustable fractional-order λ, giving it more flexible phase and gain adjustment capabilities. During integration, fractional-order integration better suppresses phase lag than standard integer-order integration, thus providing superior dynamic damping characteristics while ensuring the elimination of steady-state errors. Therefore, the reactive current reference value output by this controller can instruct the converter to generate fast, smooth, and overshoot-free reactive power, achieving precise and stable support for the grid voltage. This effectively avoids voltage oscillation problems that may occur with traditional control methods and significantly improves the system's power quality.

[0092] In some embodiments of the present invention, such as Figure 4 and Figure 7 As shown, the implementation of the supporting method is based on a unified converter control architecture. The integration and execution process of the control architecture includes:

[0093] Construct a control architecture that integrates fractional-order active frequency control, fractional-order reactive voltage control, and voltage-current dual-loop control.

[0094] The change in the capacitor voltage of the DC bus is obtained, and in the control architecture, the output frequency reference value of the AC port of the converter is generated based on the first fractional-order controller and the change in capacitor voltage.

[0095] In the control architecture, the reactive current reference value is calculated based on the second fractional-order controller, and the virtual internal potential reference value of the AC device is generated based on the reactive current reference value.

[0096] The virtual internal potential reference value is calculated based on the preset virtual impedance to obtain the voltage reference value of the voltage and current dual-loop control loop, and a PWM signal is generated to drive the power conversion of the converter.

[0097] The fractional-order active frequency control loop is implemented by the first fractional-order controller, the fractional-order reactive voltage control loop is implemented by the second fractional-order controller, and the voltage and current dual-loop control loop is implemented by the voltage loop controller and the current loop controller.

[0098] A control architecture integrating fractional-order active frequency control, fractional-order reactive voltage control, and voltage-current dual-loop control is constructed. The control architecture organically combines the aforementioned fractional-order active and reactive control with the underlying execution units to form a complete control system with distinct layers, each performing its own function and working in concert. This ensures that the intelligent decisions generated by the control algorithm can be smoothly and accurately transmitted to the power devices, and ultimately transformed into actual support actions for the power grid.

[0099] After the architecture is built, the change in the capacitor voltage of the DC bus is obtained. In the control architecture, based on the first fractional-order controller and the change in capacitor voltage, the output frequency reference value of the AC port of the converter is generated. The first fractional-order controller performs fractional-order calculation on the power difference implied by the change in capacitor voltage and outputs a frequency command with superior dynamic performance, so that the frequency adjustment of the converter port has the ability to respond proactively, intelligently and smoothly to the power imbalance state of the grid.

[0100] Meanwhile, in another path of the architecture, a reactive current reference value is calculated based on the second fractional-order controller, and a virtual internal electromotive force (EMF) reference value for the converter is generated based on this reactive current reference value. This virtual EMF simulates the internal induced electromotive force of a traditional synchronous generator. Using this virtual EMF to indirectly control reactive power output is a more fundamental and natural grid-based control method, making the converter's external characteristics closer to an ideal voltage source. This allows it to more effectively support the voltage level at the grid connection point and enhance the system's voltage stability.

[0101] Subsequently, the system calculates the virtual internal potential reference value based on the preset virtual impedance to obtain the voltage reference value of the voltage-current dual-loop control loop. The virtual impedance simulates the internal impedance characteristics of the synchronous generator, realizes autonomous power distribution, and provides a necessary buffer to effectively suppress potential oscillations caused by line impedance differences or instantaneous overcurrent, thereby enhancing the system's damping and robustness. The voltage reference value is sent to the voltage-current dual-loop controller, and after tracking and adjustment, the final PWM signal is generated to drive the power switching devices of the converter to complete the power conversion.

[0102] In the unified control architecture, the fractional-order active frequency control loop is implemented by the first fractional-order controller, the fractional-order reactive voltage control loop is implemented by the second fractional-order controller, and the voltage and current dual-loop control loop is implemented by the voltage loop PI controller and the current loop PI controller. This ensures the innovation of the top-level control strategy and makes full use of the maturity and reliability of the bottom-level control, so that the above-mentioned fractional-order matching control strategy can be implemented efficiently and reliably. Ultimately, it realizes the converter's comprehensive support for grid voltage and frequency in a fast, smooth, and adaptive manner, and significantly improves the dynamic stability of the power system under the high proportion of new energy access.

[0103] In some embodiments of the present invention, such as Figure 5 As shown, a fractional-order active frequency control matching equation is formed, including:

[0104] Integer-order active frequency control equations include ;

[0105] The DC bus energy storage capacitor on the new energy converter side is used to maintain DC side voltage stability. Its voltage change reflects the dynamic balance between the converter's input power and output power. Therefore, a traditional integer-order dynamic relationship between DC bus voltage and power difference can be established first. That is, using the DC side power difference as excitation, the dynamic change expression of DC bus voltage is obtained through energy conservation. When the input power is greater than the output power, the capacitor's energy storage causes the DC voltage to rise; conversely, the capacitor releases energy, causing the DC voltage to fall. At the same time, the change in DC bus voltage is mapped to the AC side phase angle adjustment, realizing the converter's support for grid frequency disturbances, thereby achieving dynamic matching control of active power and frequency. When a power gap occurs on the grid side, causing a frequency drop, the converter's output active power will be reflected in the drop in DC bus voltage. This voltage change will then be fed back to the AC side through the above phase angle expression, increasing the output phase angle and thus improving the converter's output active power, forming a frequency support capability similar to the inertial response characteristics of a synchronous generator.

[0106] However, the control equations based on integer-order differentials only reflect the response characteristics at a single time scale, making it difficult to cover the slow variability, nonlocality, and historical state memory effects commonly found in new energy systems. Under real wind and solar power output and weak grid conditions, the system dynamics do not completely conform to a single first-order inertial dynamic model. Therefore, this embodiment introduces fractional-order differential operators to construct a dynamic control structure with adjustable memory depth and virtual inertia characteristics, using a fractional inverse form of 1-λ, as shown below:

[0107] The integer-order differential operators in the active frequency control equations are replaced with fractional-order differential operators, forming a fractional-order active frequency control matching equation, including... ;

[0108] Where C is the DC bus capacitance of the converter, U dc0 The rated voltage of the DC bus, u dc P represents the real-time voltage value of the DC bus. re For the actual power output of the new energy converter, P out θ represents the active power output of the converter, N represents the matching coefficient from DC voltage to AC frequency, θ represents the output phase of the converter port, and λ represents the fractional order, 0 < λ < 1.

[0109] When λ approaches 0, the derivative order 1-λ approaches 1, and the active frequency control matching equation naturally degenerates into a classical integer order model. When λ approaches 1, the derivative order 1-λ approaches 0, and the system exhibits stronger historical state memory characteristics, making the power regulation process smoother and demonstrating more significant virtual inertia and damping effects. This enables the converter to have better dynamic stability and disturbance rejection capability in weak power grids.

[0110] By replacing the integer-order differential operator with the fractional-order differential operator, a fractional-order active frequency control matching equation is formed, enabling the DC-side voltage to dynamically possess adjustable memory. This allows the construction of an active frequency support mechanism with adjustable virtual inertia and damping, achieving flexible buffering and adaptive frequency stability support capabilities against grid disturbances.

[0111] Based on the above embodiments, such as Figure 5 As shown, the fractional transfer function includes:

[0112] ;

[0113] Among them, the intermediate variable K P =3U o ·U g / X, U g U represents the grid voltage amplitude. o Let X be the output voltage of the converter, X be the sum of the inductance of the converter filter and the line inductance, and S be the Laplace transform operator.

[0114] Based on the power balance relationship of the equivalent energy storage element of the DC bus, a fractional-order dynamic relationship between the DC bus voltage change and the power difference can be obtained, that is, with the DC bus rated voltage U dc0 The product of the capacitance C and the capacitance C is used as the energy storage inertia factor. The system's memory characteristics for historical power disturbances are described; based on the equivalent power transfer characteristics on the AC side, the converter output active power and its voltage phase angle difference satisfy an approximately linear relationship. The scaling factor for this linear relationship can be determined through the intermediate variable K. P The value represents the electrical coupling strength between the converter and the power grid; the larger the value, the more sensitive the converter's output power is to changes in phase angle. The matching coefficient N, representing the transition from DC voltage to AC frequency, determines the degree to which the DC bus voltage deviation affects the converter's output phase angle, thereby adjusting the active power output, in conjunction with the intermediate variable K. P The combination of these elements acts as an equivalent virtual damping mechanism, characterizing the power coupling strength between the converter and the grid from the electrical side. By forming a stable equilibrium point together with the fractional-order dynamic term, the system can achieve rapid power response under high grid strength conditions, while maintaining sufficient response damping in weak grid conditions or scenarios with severe power fluctuations, thus preventing voltage oscillations or phase divergence caused by active power injection. The fractional-order transfer function P in this embodiment... out The system achieves unified coordination of virtual inertia, virtual damping, and energy mitigation in the fractional-order active power control loop, enabling the converter to provide rapid support during grid frequency changes and maintain stable system recovery in medium- and long-term dynamics. This significantly improves the operational stability and support capability of the new energy grid-connected system under conditions of weak grid, high fluctuations, and large disturbances.

[0115] In some embodiments of the present invention, calculating the currently available reactive power capacity includes:

[0116] Constructing reactive power capacity ;

[0117] Among them, S rate P is the rated capacity of the new energy converter. out Q is the active power output of the converter. s This represents the remaining currently available reactive power capacity of the converter.

[0118] Because the output power of the converter is limited by its rated apparent power capacity S rate Therefore, at any given moment, when the converter outputs active power P out Given that the remaining reactive power capacity Q available for voltage regulation and reactive power support is... s It can be determined through the apparent power triangle relationship. During the operation of the converter, its active power and reactive power together constitute the total apparent power vector. The maximum amplitude of the apparent power is limited by the upper limit of the rated capacity of the equipment. When the active power output of the converter is large, the reactive power capacity will be reduced accordingly; conversely, when the active power output is low, the converter will have a greater reactive power support capacity. Based on this, dynamic online calculation of reactive power capacity is realized, which enables the converter to adaptively adjust the intensity of reactive power regulation according to the real-time operating status under various operating power conditions, thereby achieving sustainable, safe and stable voltage support without exceeding the equipment capacity boundary.

[0119] Based on the above embodiments, the reactive voltage droop factor is calculated, including:

[0120] reactive voltage droop coefficient ;

[0121] Among them, K q U is the reactive voltage droop factor of the converter at any given time. o，L U is the lower limit of the normal range of the converter output voltage. n This is the rated value of the output voltage of the converter.

[0122] Since the voltage regulation at the converter's grid connection point cannot exceed the safe operating range allowed by the power grid, the reactive power that the converter can absorb or inject must be coordinated with the upper and lower limits of the voltage deviation when providing voltage support. This embodiment uses (U... n -U o,L The voltage droop coefficient K represents the maximum allowable downward adjustment range of the voltage. q Available reactive power capacity Q s The reactive power voltage support behavior is dynamically updated according to changes, thus always subject to the dual constraints of equipment capacity and grid voltage safety boundary.

[0123] When the current active power output of the converter is high, the available reactive power capacity Q s When it is small, the obtained droop coefficient K q The reactive power will naturally decrease, thus limiting the extent of reactive power regulation. This prevents the converter from outputting excessive reactive power under high load conditions to support the grid voltage, which could lead to increased DC bus voltage, increased device heat loss, or even system protection activation. Conversely, when the converter operates under low active power output conditions, the available reactive power capacity Q can be reduced. s Increasing the droop coefficient K q This will be increased accordingly to achieve a stronger reactive power support effect, using a reactive voltage droop coefficient K. q This helps the power grid maintain voltage stability when voltage fluctuates, load increases, or line power distribution changes.

[0124] Based on the above embodiments, such as Figure 6 As shown, based on the droop characteristics, reactive voltage support is further implemented, and the deviation signal for reactive voltage control is generated, including:

[0125] Constructing equations ;

[0126] Where E is the virtual internal potential of the converter, and K q k is the reactive voltage droop factor. v The reactive power integral coefficient, Q, is set manually. ref E is the reactive power setpoint for the converter. o Q is the corresponding output internal potential. out U is the real-time value of the reactive power of the converter, and U is the real-time effective value of the converter port voltage.

[0127] The equations in this embodiment reflect the adaptive variation of reactive power support commands with voltage deviation. When the grid voltage is lower than the rated voltage (U... n When -U)>0, the system automatically increases reactive power output to boost voltage; when the grid voltage returns to normal, (U) n -U) decreases, causing reactive power support to gradually decrease, thereby ensuring stable system operation and preventing overcompensation; since the calculation of reactive power support capacity includes apparent power capacity constraints, the resulting converter reactive power setpoint Q ref It always stays within the safe range allowed by the converter equipment, avoiding the reactive power output exceeding the limit and voltage oscillation problems that may occur in traditional fixed droop control.

[0128] Then, a virtual internal potential is generated by integrating the reactive power deviation. When the actual reactive power output Q... out Less than the target reactive power input Q refWhen the integral term is positive, the virtual internal potential amplitude E increases, thereby increasing the voltage amplitude at the converter output port and allowing it to inject more reactive power into the grid. Conversely, when the measured reactive output is greater than the reference value, the virtual internal potential will decrease, causing the reactive power injection to automatically revert. The integral term has historical memory characteristics, so the converter voltage support process has stable convergence, avoiding the oscillation and instability that are prone to occur in traditional proportional droop control.

[0129] Based on the above embodiments, such as Figure 6 As shown, the reactive current reference value obtained according to the second fractional-order controller includes:

[0130] Constructing the fractional-order transfer function of reactive voltage ;

[0131] Among them, U g X represents the grid voltage amplitude. g Here, S is the reactance of the connecting line, S is the Laplace transform operator, ΔE is the increment of the virtual internal potential of the converter, and ΔQ is the value of the reactance of the connecting line. out This represents the increment of the reactive power of the converter.

[0132] Based on the aforementioned reactive power reference generation mechanism and virtual internal potential adjustment relationship, the reactive power output deviation ΔQ out As the control input, the virtual internal potential change ΔE is used as the control output to construct a fractional-order transfer function for reactive power voltage. This function expresses how the converter, during reactive power voltage regulation, accumulates and mitigates reactive power changes through a dynamic process with 1-λ-order fractional integral characteristics. It avoids directly and instantaneously transmitting reactive power deviations to the internal potential regulation, thus giving reactive power support a buffer-then-enhancement time characteristic. Furthermore, since 0 < λ < 1, the fractional-order integral operator... Located between the zeroth and first order integrals, this allows the system to generate a smooth, oscillating dynamic response during rapid voltage disturbances, avoiding secondary voltage fluctuations caused by excessively fast response during reactive power regulation.

[0133] In the fractional-order transfer function of reactive voltage (K) q k v X g +U g k v The term comprehensively reflects the combined effect of droop characteristics, reactive power regulation proportional gain, and grid reactance on dynamic support capability. When the grid is weak or the voltage support demand is stronger, this term automatically increases, making reactive power regulation more powerful; while when the grid is strong or strong support is not needed, this term naturally weakens, making the regulation process more gradual; U in the denominator g It makes the regulation intensity inversely proportional to the grid voltage amplitude, and has the characteristic of adaptively adjusting the support sensitivity according to the voltage level.

[0134] This invention also provides a voltage and frequency support system for a new energy converter based on fractional-order matched control, comprising:

[0135] The initial configuration module configures the rated operating parameters of the converter system and initializes the first fractional-order controller of the active frequency matching control loop and the second fractional-order controller of the reactive voltage control loop.

[0136] The data acquisition and calculation module collects the operating data of the new energy converter and calculates the instantaneous power difference between the two ends of the DC bus.

[0137] The active power signal generation module constructs a fractional transfer function, calculates the additional frequency regulation based on the instantaneous power difference, and superimposes the additional frequency regulation with the rated frequency of the power grid to generate the output frequency reference value of the AC port of the converter; the output frequency reference value is sent to the outer loop controller of the converter, and a PWM signal is generated to drive the power switching devices of the converter through pulse width modulation.

[0138] The reactive power reference calculation module calculates the current available reactive power capacity of the converter based on the operating data and the apparent power capacity limit of the converter, and calculates the reactive voltage droop coefficient based on the reactive power capacity; based on the reactive voltage droop coefficient, the preset rated voltage reference value and the operating data, the reactive current reference value is calculated by the second fractional-order controller.

[0139] The power support module adjusts the active power output of the converter according to the PWM signal, and controls the converter to inject or absorb the corresponding reactive power into the grid according to the reactive current reference value.

[0140] The voltage and frequency support system described above in this invention can effectively realize the voltage and frequency support method for new energy converters based on fractional-order matching control. The technical effects it can achieve are as described in the above embodiments, and will not be repeated here.

[0141] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0142] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0143] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0144] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0145] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0146] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for supporting the voltage and frequency of a new energy converter based on fractional-order matched control, characterized in that, Includes the following steps: Configure the rated operating parameters of the converter system, and initialize the first fractional-order controller of the active frequency matching control loop and the second fractional-order controller of the reactive voltage control loop; Collect operating data from the new energy converter and calculate the instantaneous power difference between the two ends of the DC bus; Construct a fractional transfer function, calculate the additional frequency adjustment based on the instantaneous power difference, and superimpose the additional frequency adjustment with the rated frequency of the power grid to generate the output frequency reference value of the AC port of the converter. The output frequency reference value is sent to the outer loop controller of the converter, and a PWM signal is generated to drive the power switching devices of the converter through pulse width modulation. Based on the operating data and the apparent power capacity limit of the converter, the current available reactive power capacity of the converter is calculated, and the reactive voltage droop coefficient is calculated based on the reactive power capacity. Based on the reactive voltage droop coefficient, the preset rated voltage reference value, and the operating data, the reactive current reference value is calculated by the second fractional-order controller. The active power output of the converter is adjusted according to the PWM signal, and the reactive current reference value is used to control the converter to inject or absorb the corresponding reactive power into the grid.

2. The voltage and frequency support method for a new energy converter based on fractional-order matched control according to claim 1, characterized in that, The fractional-order transfer function is constructed using a first fractional-order controller based on capacitor voltage, including the following steps performed within the first fractional-order controller: Obtain the correspondence between the voltage change of the DC bus capacitor and the instantaneous power difference, and simulate the rotor motion equation of the synchronous generator to establish an integer-order active frequency control equation. The integer-order differential operator in the active frequency control equation is replaced with a fractional-order differential operator to form a fractional-order active frequency control matching equation. Based on the active frequency control matching equation, the fractional transfer function with the instantaneous power difference as input and the additional frequency adjustment as output is derived.

3. The voltage and frequency support method for new energy converters based on fractional-order matched control according to claim 1, characterized in that, The reactive current reference value is obtained according to the second fractional-order controller, including: Based on the real-time output active power of the converter and the upper limit of the apparent power capacity in the operating data, calculate the currently available reactive power capacity; Based on the reactive power capacity and the allowable range of converter port voltage, the reactive power droop coefficient is calculated. Based on the reactive voltage droop coefficient and the correspondence between the real-time voltage of the converter port in the operating data and the rated voltage reference value, a deviation signal for reactive voltage control is generated. The deviation signal is input to the second fractional-order controller for fractional-order calculus and integrator operations, and the reactive current reference value is output. The second fractional-order controller is a fractional-order PI controller. λ Controller.

4. The voltage and frequency support method for new energy converters based on fractional-order matched control according to any one of claims 1 to 3, characterized in that, The implementation of the aforementioned support method is based on a unified converter control architecture, and the integration and execution process of the control architecture includes: Construct a control architecture that integrates fractional-order active frequency control, fractional-order reactive voltage control, and voltage-current dual-loop control. The change in the capacitor voltage of the DC bus is obtained, and in the control architecture, the output frequency reference value of the AC port of the converter is generated based on the first fractional-order controller and the change in the capacitor voltage. In the control architecture, the reactive current reference value is calculated based on the second fractional-order controller, and the virtual internal potential reference value of the AC device is generated based on the reactive current reference value. The virtual internal potential reference value is calculated based on the preset virtual impedance to obtain the voltage reference value of the voltage and current dual-loop control loop, and the PWM signal is generated to drive the power conversion of the converter. The fractional-order active frequency control loop is implemented by the first fractional-order controller, the fractional-order reactive voltage control loop is implemented by the second fractional-order controller, and the voltage and current dual-loop control loop is implemented by the voltage loop controller and the current loop controller.

5. The voltage and frequency support method for new energy converters based on fractional-order matched control according to claim 2, characterized in that, A fractional-order active frequency control matching equation is formed, including: The integer-order active frequency control equations include ; Replacing the integer-order differential operators in the active frequency control equation with fractional-order differential operators forms a fractional-order active frequency control matching equation. ; Where C is the DC bus capacitance of the converter, U dc0 The rated voltage of the DC bus, u dc P represents the real-time voltage value of the DC bus. re For the actual power output of the new energy converter, P out The active power output of the converter is denoted by N, which represents the matching coefficient from DC voltage to AC frequency. θ is the output phase of the converter port, and λ is the fractional order.

6. The voltage and frequency support method for a new energy converter based on fractional-order matched control according to claim 5, characterized in that, The fractional transfer function includes: ； Among them, the intermediate variable K P =3U o ·U g / X, U g U represents the grid voltage amplitude. o Let X be the output voltage of the converter, X be the sum of the inductance of the converter filter and the line inductance, and S be the Laplace transform operator.

7. The voltage and frequency support method for new energy converters based on fractional-order matched control according to claim 3, characterized in that, Calculating the currently available reactive power capacity includes: Construct the reactive power capacity ; Among them, S rate P is the rated capacity of the new energy converter. out Q is the active power output of the converter. s The remaining currently available reactive power capacity of the converter.

8. The voltage and frequency support method for new energy converters based on fractional-order matched control according to claim 7, characterized in that, The calculation of the reactive voltage droop factor includes: The reactive voltage droop coefficient ; Among them, K q U is the reactive voltage droop coefficient of the converter at any given time. o，L U is the lower limit of the normal range of the converter output voltage. n This is the rated value of the output voltage of the converter.

9. The voltage and frequency support method for new energy converters based on fractional-order matched control according to claim 8, characterized in that, Based on the droop characteristics, further reactive voltage support is achieved, generating deviation signals for reactive voltage control, including: Constructing equations ; Where E is the virtual internal potential of the converter, and K q Let k be the reactive voltage droop coefficient. v The reactive power integral coefficient, Q, is set manually. ref E is the reactive power setpoint for the converter. o Q is the corresponding output internal potential. out U is the real-time value of the reactive power of the converter, and U is the real-time effective value of the converter port voltage.

10. The method for supporting the voltage and frequency of a new energy converter based on fractional-order matched control according to claim 9, characterized in that, The reactive current reference value is obtained according to the second fractional-order controller, including: Constructing the fractional-order transfer function of reactive voltage ; Among them, U g X represents the grid voltage amplitude. g Here, S is the reactance of the connecting line, S is the Laplace transform operator, ΔE is the increment of the virtual internal potential of the converter, and ΔQ is the value of the reactance of the connecting line. out This represents the increment of the reactive power of the converter.

11. A voltage and frequency support system for a new energy converter based on fractional-order matched control, characterized in that, include: The initial configuration module configures the rated operating parameters of the converter system and initializes the first fractional-order controller of the active frequency matching control loop and the second fractional-order controller of the reactive voltage control loop. The data acquisition and calculation module collects the operating data of the new energy converter and calculates the instantaneous power difference between the two ends of the DC bus. The active signal generation module constructs a fractional transfer function, calculates the additional frequency adjustment based on the instantaneous power difference, and superimposes the additional frequency adjustment with the rated frequency of the power grid to generate the output frequency reference value of the AC port of the converter. The output frequency reference value is sent to the outer loop controller of the converter, and a PWM signal is generated to drive the power switching devices of the converter through pulse width modulation. The reactive power reference calculation module calculates the current available reactive power capacity of the converter based on the operating data and the apparent power capacity limit of the converter, and calculates the reactive voltage droop coefficient based on the reactive power capacity; based on the reactive voltage droop coefficient, the preset rated voltage reference value and the operating data, the reactive current reference value is calculated by the second fractional-order controller. The power support module adjusts the active power output of the converter according to the PWM signal, and controls the converter to inject or absorb corresponding reactive power into the grid according to the reactive current reference value.

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