Single-phase inverter power distribution method based on SOGI and droop control

Abstract

The application discloses a single-phase inverter power distribution method based on SOGI and droop control, relates to the technical field of single-phase inverters, and comprises the following steps: S1, output electric quantity real-time acquisition and orthogonal signal construction; S2, instantaneous power solution based on orthogonal components; S3, droop characteristic mapping and frequency and voltage instruction generation; and S4, closed-loop modulation and driving pulse generation. The application realizes algebraic cancellation of a two-frequency pulsation component in single-phase power by substituting orthogonal voltage and current components into an instantaneous power solution model, solves the inherent two-frequency ripple interference problem in single-phase inverter power calculation, and focuses on improving power distribution precision, actively suppressing parallel circulating current and reducing total harmonic distortion through dynamic setting of droop coefficients matched with capacity levels, optimization of a droop control law with adaptive voltage compensation, and high-precision double-loop control parameter quantization design.

Description

Technical Field

[0001] This invention relates to the field of single-phase inverter technology, and in particular to a power distribution method for single-phase inverters based on SOGI and droop control. Background Technology

[0002] With the rapid development of distributed power generation and microgrid technologies, single-phase inverters, as key interfaces for energy conversion, have attracted widespread attention for the stability and power distribution accuracy of their parallel operation systems. In a microgrid architecture, the parallel operation of multiple inverters can not only improve system redundancy but also enable flexible capacity expansion. To ensure the coordinated operation of each unit, establishing a high-precision, fast-response power distribution control system has become an important topic in the field of distributed energy research.

[0003] For parallel systems without communication connections, the main approach relies on droop control technology to simulate the operating characteristics of synchronous generators. This approach aims to obtain the active and reactive power of the system by sampling and calculating the output voltage and current, and then adjust the frequency and amplitude of the output voltage to build autonomous current sharing and voltage support capabilities for both islanded and grid-connected modes.

[0004] Existing technologies for power distribution in single-phase inverters still have limitations. Calculating instantaneous power requires extracting average power through a low-pass filter, resulting in an inherent time delay in the power feedback signal. Furthermore, when dealing with inverters of different capacities operating in parallel, there is room for improvement in the flexibility of droop coefficient adjustment and the accuracy of proportional power distribution. Traditional fixed droop coefficients cannot achieve proportional power distribution based on capacity, easily leading to overload issues with smaller capacity inverters and underload issues with larger capacity inverters. Additionally, traditional droop control lacks voltage compensation, failing to offset the effects of line impedance voltage drop and parallel circulating current, resulting in uneven reactive power distribution. Dual-loop voltage and current controllers only qualitatively describe the topology without quantitative parameter design criteria, making engineering debugging difficult and leading to a high total harmonic distortion rate under nonlinear loads. All these issues affect the system's dynamic response speed and operational stability during load switching.

[0005] Therefore, a power distribution method for single-phase inverters based on SOGI and droop control is proposed to solve the above problems. Summary of the Invention

[0006] The main objective of this invention is to provide a power distribution method for single-phase inverters based on SOGI and droop control, so as to solve the problems of power feedback delay introduced by low-pass filters and limited power distribution accuracy when inverters of different capacities are connected in parallel in the prior art.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: a power distribution method for a single-phase inverter based on SOGI and droop control, comprising the following steps: S1. Real-time acquisition of output power and construction of orthogonal signals.

[0008] S101. The output voltage sampling sequence and output current sampling sequence are obtained in real time by using voltage transformers and current transformers installed at the output of the single-phase inverter.

[0009] S102. Input the voltage sampling sequence and the current sampling sequence into a preset second-order generalized integrator orthogonal signal generator.

[0010] S103. The fundamental component is extracted using the bandpass filtering characteristics of the second-order generalized integrator. The amplitude-frequency characteristic of the second-order generalized integrator is an inverted triangle, with the peak value corresponding to the system fundamental frequency of 50Hz. At this frequency, the amplitude is not attenuated and the amplitude-frequency gain is 0. It has an attenuation effect on all frequency signals other than 50Hz, and the attenuation effect is stronger the further the frequency deviates from 50Hz. Virtual voltage components and virtual current components that are orthogonal to each other in phase are constructed to form a multidimensional orthogonal signal set.

[0011] S2. Delay-free instantaneous power calculation based on orthogonal components.

[0012] S201. Extract the in-phase and quadrature components from the multidimensional orthogonal signal set.

[0013] S202. Substitute the in-phase component and the quadrature component into the preset instantaneous power calculation model.

[0014] S203. The instantaneous active power and instantaneous reactive power containing second harmonic ripple are obtained through algebraic operations. The instantaneous power calculation model eliminates the second harmonic pulsation component in the single-phase system by combining the multiplication and accumulation of orthogonal components. The calculation formula is as follows: ; ; in, Instantaneous active power Instantaneous reactive power The output voltage is the fundamental in-phase component. The fundamental orthogonal components of the output voltage. The output current is the fundamental in-phase component. This refers to the fundamental orthogonal component of the output current.

[0015] S204. The instantaneous power is fed into a low-pass filter to filter out the second harmonic ripple, resulting in ripple-free average power. The cutoff frequency of this low-pass filter is typically set to 25Hz, which is a low cutoff frequency configuration. Since it mainly filters out the second harmonic rather than high-frequency components, the response speed is relatively slow. The lower the cutoff frequency of the low-pass filter and the larger the time constant, the slower the response speed. Since the second-order generalized integrator has already performed pre-selective filtering, the cutoff frequency of the low-pass filter is set in a preset frequency band much higher than the system fundamental frequency, reducing the time constant in the power feedback loop and reducing the phase lag of the feedback signal.

[0016] S3. Droop Characteristic Mapping and Frequency-Voltage Command Generation: Based on the inverter's rated capacity level, the active frequency droop coefficient m and reactive voltage droop coefficient n are dynamically adjusted. The calculated average power is substituted into the droop control equation, which is configured with a capacity weighting coefficient and incorporates an adaptive voltage compensation term. By simulating the external characteristics of a synchronous generator, the power fluctuation is mapped into the frequency and amplitude commands of the output voltage. The droop control equation dynamically adjusts the droop coefficient according to the inverter's rated capacity level so that the power output of each parallel unit is in a preset proportion to its capacity. At the same time, the voltage compensation term compensates for line voltage drop and suppresses parallel circulating current.

[0017] S4, Closed-loop modulation and drive pulse generation.

[0018] S401. Use the generated frequency command and amplitude command as reference inputs.

[0019] S402. A dual-loop control structure for voltage and current is constructed by combining the output voltage feedback value. The outer voltage loop adopts a quasi-proportional resonant controller and the transfer function is quantitatively designed. The inner current loop adopts a proportional controller and the parameter tuning range is clearly defined. The quasi-proportional resonant controller provides a large open-loop gain at the system resonant frequency, suppressing the voltage tracking error to below the preset threshold. The proportional controller increases the system's control bandwidth and dynamic response speed.

[0020] S403 generates a modulated wave signal through a proportional-integral controller and generates a drive command for the power switch transistor via a pulse width modulation module.

[0021] S404. Adjust the switching status of the inverter bridge.

[0022] Furthermore, the transfer function of the second-order generalized integrator quadrature signal generator described in S1 is configured as follows: ; ; in, The preset resonant angular frequency of the system, The damping gain coefficient is preset; the input signal is filtered in a closed loop through the transfer function, and two orthogonal variables with a predetermined phase difference are directly obtained at the output, thereby replacing the traditional phase-shift triggering logic and suppressing high-order harmonic interference in the sampled signal.

[0023] Furthermore, the core principle of dynamically adjusting the active frequency droop coefficient m and reactive voltage droop coefficient n based on the inverter's rated capacity level in step S3 is: the droop coefficient is inversely proportional to the inverter's rated capacity; the larger the rated capacity, the smaller the droop coefficient, ensuring that a larger capacity inverter can handle more power at the same frequency or voltage offset, thus achieving power distribution according to capacity ratio; the specific calculation formula is: ; ; Among them, For the first Active and reactive droop coefficients of the inverter; This represents the maximum allowable frequency deviation of the system. This represents the maximum allowable voltage amplitude deviation of the system. and For the first Rated active and reactive power capacities of the inverter; This represents the total number of parallel inverters. and The reference rated active and reactive power capacity for the parallel system can be taken as the maximum rated capacity of a single unit or the system design capacity. Since SOGI has completed the fundamental frequency gating and harmonic attenuation, the subsequent low-pass filter only needs to be designed for the second harmonic component and can be configured with a low cutoff frequency.

[0024] Since the second-order generalized integrator has performed pre-selective frequency filtering, the cutoff frequency of the low-pass filter is set at a preset frequency band much higher than the system fundamental frequency, which reduces the time constant in the power feedback loop and reduces the phase lag of the feedback signal.

[0025] Furthermore, the droop control equation described in S3 is specifically expressed as follows: ; ; in, This is the output voltage frequency command. This is the output voltage amplitude command. and These are the preset rated frequency and rated voltage amplitude, respectively. The active power to frequency droop factor, This is the reactive power to voltage droop factor. and The average power value after processing; the droop coefficient and It is inversely proportional to the unit rated capacity of the inverter; This is an adaptive voltage compensation term used to suppress circulating current, compensate for line impedance voltage drop, and improve reactive power distribution accuracy.

[0026] Furthermore, S3 also includes an adaptive coefficient compensation step: by real-time monitoring of the voltage drop at the parallel bus, the effective value of the inverter output current, and the effective value of the parallel circulating current, a voltage compensation term is introduced into the droop control equation. The calculation is based on the line impedance voltage drop and the circulating current suppression requirement. The specific calculation formula is as follows: ;

[0027] in, This is the effective value of the inverter output current; and The equivalent resistance and reactance of the line from the inverter to the parallel bus; The inverter output power factor angle; The circulation suppression coefficient is... Take 0.1~0.5, and adjust according to the scale of parallel connection of the system. The calculation of average current and circulating current difference that depends on multi-machine communication is cancelled. The local reactive power deviation is used to replace the circulating current feedback. There is no need to obtain the output current of other parallel units. There is no communication delay. Circulating current suppression and voltage compensation can be achieved by relying solely on local sampling. Take 0.1 for 2 units in parallel, and take 0.3~0.5 for 4 units or more. The effective value of the circulating current in the parallel system is calculated from the difference in the output current of each inverter: This is the effective value of the average output current of the parallel inverter; the offset of the voltage amplitude command is dynamically corrected according to the change of load current, the bus voltage fluctuation is controlled within the preset tolerance range, and the parallel circulating current is suppressed to within 5% of the rated current.

[0028] Furthermore, the controller transfer function of the voltage-current dual-loop control structure is quantized as follows: Transfer function of the voltage outer loop quasi-proportional resonant controller: ; in This is the voltage outer loop proportional gain. Select a value between 0.5 and 2.0, and adjust it according to the system bandwidth; For resonant gain, Use values ​​between 20 and 100 to improve fundamental frequency tracking accuracy; This is the cutoff frequency of the resonant controller. To improve robustness, a value of 5-20 rad / s is used. When the system's fundamental angular frequency is 50Hz, =314 rad / s; Transfer function of the current inner loop proportional controller: ; in, This is the proportional gain of the inner current loop. A value of 5-20 is chosen to balance dynamic response and stability, satisfying the requirements. , This is the equivalent series resistance of the filter inductor.

[0029] Furthermore, S4 also includes synchronization logic processing: during the inverter startup phase, the voltage phase information of the parallel bus is captured by the software phase-locked loop. When the phase difference between the inverter output voltage and the bus voltage is less than the preset angle threshold, the grid-connected contactor is closed to switch the inverter into parallel operation mode.

[0030] Furthermore, the present invention also relates to a single-phase inverter power distribution system for performing the above method, including a data acquisition module, a central processing unit, a drive isolation module, and an inverter power main circuit; The data acquisition module includes a Hall voltage sensor and a Hall current sensor, and is also used to acquire the effective value of the inverter output current, the effective value of the parallel bus circulating current, and the power factor angle, providing data support for adaptive voltage compensation and droop coefficient setting; the output of the sensor is connected to the analog-to-digital conversion interface of the central processing unit through an anti-aliasing filter circuit; The central processing unit is internally divided into a signal processing area, a power control area, and a signal modulation area. The signal processing area encapsulates the second-order generalized integrator algorithm logic. The power control area stores the droop control law and the dual-loop PI adjustment program. The signal modulation area is equipped with a high-resolution pulse width modulation peripheral. The input terminal of the drive isolation module is connected to the modulation output pin of the central processing unit, and the output terminal is connected to the gate of the power switch in the main circuit of the inverter power through an optocoupler circuit. The inverter power main circuit adopts a full-bridge topology, with a large electrolytic capacitor connected in parallel on the DC side and an LC power filter connected on the AC side.

[0031] Furthermore, the central processing unit employs a digital signal processor with a floating-point arithmetic unit, and its main frequency is set within a preset high-frequency range to support the iterative calculation of the second-order generalized integrator in each sampling period. The central processing unit supports plug-and-play for parallel inverters. When an inverter is connected to the system, it automatically identifies its own rated capacity and the total number of inverters connected in parallel with the system, and loads the corresponding droop coefficient and dual-loop controller parameters without manual adjustment. The corner frequency of the anti-aliasing filter circuit is configured according to a preset ratio of the sampling frequency to suppress noise aliasing above the Nyquist frequency.

[0032] Furthermore, the LC-type power filter in the main circuit of the inverter power includes a filter inductor and a filter capacitor; the magnetic core of the filter inductor is made of high flux density metal powder core material, and the winding is made of multiple strands of enameled wire wound in parallel to reduce skin effect loss in high-frequency switching state; the filter capacitor is a thin film capacitor with low equivalent series resistance, which is set at the output terminal lead.

[0033] Furthermore, the central processing unit is also equipped with a communication interface, which connects to an external monitoring terminal via an industrial bus to upload the inverter's operating status parameters in real time, including instantaneous power, effective value of output voltage, effective value of parallel circulating current, total harmonic distortion rate, and predetermined surface temperature of the heat sink.

[0034] The present invention has the following beneficial effects: 1. In this invention, an instantaneous power extraction mechanism for the output power of a single-phase system is constructed by introducing a second-order generalized integrator to construct an orthogonal signal. The bandpass filtering characteristics of the second-order generalized integrator are used to directly obtain the fundamental orthogonal components, eliminating the step of extracting the average power by relying on a low-pass filter with large amplitude attenuation in the traditional method. In this way, the signal processing time in the power feedback path is greatly shortened, the phase lag of the control loop is reduced, and the inverter can quickly capture the power deviation and adjust the output frequency and amplitude at the moment of load change, which significantly improves the dynamic response speed and transient stability of the parallel system.

[0035] 2. In this invention, by substituting the orthogonal voltage and current components into the instantaneous power calculation model, algebraic cancellation of the second harmonic ripple component in single-phase power is achieved, solving the inherent second harmonic ripple interference problem in single-phase inverter power calculation; coupled with a quasi-proportional resonant control algorithm based on parameter quantization, and with the resonant gain adaptively adjusted according to the load nonlinearity, the voltage tracking error is controlled within... Within this range, the output voltage waveform maintains a high degree of sinusoidal characteristics even under nonlinear load conditions, and the system's total harmonic distortion rate is low. This reduces the total harmonic distortion rate of the system and provides high-quality voltage support for the microgrid.

[0036] 3. In this invention, a flexible power distribution system is established by configuring a droop coefficient inversely proportional to the inverter capacity and introducing an adaptive voltage compensation term based on line impedance voltage drop and circulating current feedback. This system can automatically adjust the power contribution share according to the real-time capacity status of each unit in the parallel system, realizing power distribution according to capacity ratio and minimizing power distribution errors. This solves the problem of uneven reactive power distribution caused by inconsistent line impedance; by dynamically correcting the offset of the droop curve, the circulating current during parallel operation is suppressed to within the rated current. Within this range, the redundancy and operational reliability of multi-machine parallel systems have been improved.

[0037] 4. In this invention, by integrating parameter quantization design with voltage and current dual-loop control and high-frequency sampling technology, the system's control bandwidth is extended to a preset high-frequency range. The floating-point operation capability of the digital signal processor enables high-frequency iteration of the control algorithm. The central processing unit pre-stores parameter tables, supporting plug-and-play inverters and reducing engineering debugging costs. Combined with hardware optimization of the LC power filter, conduction losses and electromagnetic interference during power conversion are reduced, enabling the entire power distribution system to maintain good robustness in both islanded and grid-connected modes, providing a solid technical guarantee for the large-scale access and flexible expansion of distributed energy resources. Attached Figure Description

[0038] Figure 1 This is a flowchart illustrating the overall steps of the allocation method of the present invention; Figure 2 This is a flowchart illustrating the construction of orthogonal signals in step S1 of the present invention. Figure 3 This is a flowchart illustrating the calculation of instantaneous power in step S2 of the present invention. Figure 4 This is a flowchart illustrating the specific process of generating the driving pulse in step S4 of the present invention. Figure 5 This is a block diagram showing the structural composition of the power distribution system of the present invention; Figure 6 This is a schematic diagram of the central processing unit of the present invention. Detailed Implementation

[0039] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0040] Please refer to Figures 1 to 6 As shown: A power distribution method for single-phase inverters based on SOGI and droop control is mainly used to achieve high-precision power sharing, active suppression of circulating current, and dynamic voltage and frequency support with low harmonics for multiple single-phase inverter units in a microgrid parallel system.

[0041] The system upon which this method is based consists of an output power acquisition module, a core signal processing unit, a drive isolation output module, and an inverter power main circuit in terms of physical architecture. Each part forms an organic technical whole through signal sampling lines, data communication buses, and power transmission buses.

[0042] In terms of hardware construction, the output power acquisition module is located at the AC output end of the inverter power main circuit. This module includes a Hall voltage sensor and a Hall current sensor, and is also equipped with a circulating current acquisition sensor and a power factor angle detection module to acquire the effective value of the inverter output current, the effective value of the parallel bus circulating current, and the power factor angle. Its sensing terminals are connected across the two ends of the output line or in series in the output circuit. The output pins of the sensors are connected to the analog-to-digital conversion interface of the core signal processing unit through shielded cables. An anti-aliasing filter circuit is configured in the front-end circuit of the analog-to-digital conversion interface. This circuit uses a low-pass filter topology built with an operational amplifier. Its corner frequency is set according to the preset ratio of the sampling frequency to suppress high-frequency noise aliasing.

[0043] The core signal processing unit, serving as the algorithm control center of the entire system, has its internal logic circuit divided into a signal processing area, a power control area, and a signal modulation area. The signal processing area encapsulates the second-order generalized integrator algorithm logic for constructing orthogonal signal sets. The power control area stores an improved droop control law, a capacity-matched droop coefficient tuning program, a voltage calculation program with adaptive compensation, and a parameter-quantized dual-loop control program. It also pre-stores droop coefficient tuning parameter tables and dual-loop controller parameter tables for inverters with different rated capacities. The signal modulation area is equipped with high-resolution pulse width modulation peripherals. The core signal processing unit employs a digital signal processor with a floating-point arithmetic unit. Its main frequency is set within a preset high-frequency range to support real-time iteration of the control algorithm in each sampling cycle. It also supports plug-and-play inverters, automatically identifying capacity and loading corresponding parameters upon system connection.

[0044] The inverter power main circuit adopts a full-bridge topology, with a large-capacity electrolytic capacitor connected in parallel on its DC input side to stabilize the DC bus voltage. The power switching transistors are insulated-gate bipolar transistors or silicon carbide power devices, with their gates connected to the core signal processing unit via a drive isolation module. An LC-type power filter is connected to the AC output side of the main power circuit, consisting of a filter inductor and a filter capacitor. The filter inductor's core is made of high-flux-density metal powder core material, and the windings are made of multiple strands of enameled wire wound in parallel to reduce high-frequency skin effect losses. The filter capacitor is a thin-film capacitor with low equivalent series resistance, connected in parallel to the AC output bus.

[0045] Based on the above hardware structure, the specific execution steps of the power allocation method described in this embodiment are as follows: S1. Real-time acquisition of output power and construction of orthogonal signals: The core signal processing unit acquires the output voltage sampling sequence from the voltage and current sensors in real time through the analog-to-digital conversion interface. With output current sampling sequence The sequence is input into a preset second-order generalized integrator orthogonal signal generator; the transfer function of the generator is configured as follows: ; ;

[0046] in, The preset resonant angular frequency of the system, The fundamental component is extracted using the frequency selection characteristics of a second-order generalized integrator, which serves as the damping gain coefficient. Virtual voltage components that are orthogonal in phase are then directly constructed at the output. With virtual current components The fundamental component is extracted by utilizing the bandpass filtering characteristics of a second-order generalized integrator. The amplitude-frequency characteristic of SOGI is an inverted triangle, with the peak value corresponding to the system fundamental frequency of 50Hz. At this frequency, there is no amplitude attenuation and the amplitude-frequency gain is 0. It has an attenuation effect on all frequency signals outside 50Hz, and the attenuation effect is stronger the further the frequency deviates from 50Hz. At the output end, virtual voltage components and virtual current components that are orthogonal in phase are directly constructed to form a multidimensional orthogonal signal set.

[0047] S2. Instantaneous power calculation and smoothing process without delay: Extract the in-phase and quadrature components from the multidimensional orthogonal signal set, and substitute them into the instantaneous power calculation model. The calculation formula is as follows: ; ; in, Instantaneous active power The instantaneous reactive power is calculated; the second harmonic ripple component in the single-phase system is canceled by multiplying and accumulating the orthogonal components; subsequently, the instantaneous power is input into a small-bandwidth low-pass filter with a cutoff frequency much higher than the fundamental frequency to filter out residual ripple and obtain the average power value. and This provides a precise power reference for subsequent droop control. The inherent pulsation component of the instantaneous power in a single-phase system is a second harmonic component, not a high-frequency component. The instantaneous active power and instantaneous reactive power are input into a preset low-pass filter to filter out the second harmonic component and obtain the average power. With The cutoff frequency of this low-pass filter is usually set to 25Hz, which is a low cutoff frequency configuration, resulting in a relatively slow response speed. The bandwidth of the low-pass filter is positively correlated with the response speed: the lower the cutoff frequency and the larger the time constant, the slower the response speed.

[0048] S3. Droop Characteristic Mapping and Adaptive Command Generation Process: The core processing unit automatically identifies the rated active and reactive power capacity of the local inverter. and and the total number of inverters connected in parallel in the system. Substitute into the preset formula: ; ;

[0049] The active frequency droop coefficient of this inverter is calculated in real time. With reactive voltage droop factor ,in Take 0.5Hz. Take 5V. Take the maximum rated active capacity of a single inverter in the system.

[0050] Then, the effective value of the inverter output current is obtained through the data acquisition module. Power factor angle Line equivalent resistance With reactance The effective value of the circulating current in the parallel system was calculated. .

[0051] Then substitute the collected parameters into the formula. The adaptive voltage compensation term is calculated, where the circulating current suppression coefficient is... The value is 0.3 based on the parallel capacity of the system.

[0052] Substituting the processed average power value, the tuned droop coefficient, and the calculated voltage compensation term into the droop control equation with the capacity weighting coefficient, the specific calculation formula is as follows: ; ; in, This is the output voltage frequency command. This is the output voltage amplitude command; For the rated frequency, This is the rated voltage amplitude; These are the reference power for active and reactive power, respectively; This is the active frequency droop factor. This is the reactive voltage droop factor; This is an adaptive voltage compensation term used to suppress circulating current, compensate for line impedance voltage drop, and improve reactive power distribution accuracy. At the same time, the system monitors the voltage drop at the parallel bus in real time and dynamically corrects the voltage amplitude command to control the bus voltage fluctuation within ±2%.

[0053] S4. Closed-loop modulation and drive pulse generation process: The core signal processing unit uses the generated frequency command f and amplitude command E as reference inputs for the voltage outer loop; the voltage outer loop adopts a parametrically quantized quasi-proportional resonant controller with the following transfer function: ; in Take 1.0, Take 50, Take 10 rad / s, A value of 314 rad / s is chosen to provide maximum gain at the resonant frequency; the inner current loop employs a parameter-quantized proportional controller with the following transfer function: ; in Take 10, and collect the filter inductor current as the feedback quantity; the modulation wave signal generated by the dual-loop control is input to the pulse width modulation module to generate the drive command for the power switch transistor. After passing through the drive isolation module, the switching state of the inverter bridge is adjusted. The core processing unit detects the total harmonic distortion rate of the output voltage in real time. Then gradually increase Up to 80-100, until .

[0054] In specific application scenarios, such as a microgrid parallel system containing two inverters of different capacities (Inverter 1: rated capacity 5kVA, Inverter 2: rated capacity 10kVA), this method is deployed in their respective core control boards; after the core processing unit automatically identifies the capacity, it tunes to obtain the droop factor of inverter 1. , The output power is twice that of inverter 2. When a power surge occurs at the load end, the time constant of the power feedback loop is significantly reduced because the quadrature signal generator of the second-order generalized integrator replaces the traditional large-inertia low-pass filter. The core processing unit can quickly capture the instantaneous power change and adjust the phase angle and amplitude of the output voltage in real time according to the droop coefficient in step S3. Inverter 2 bears about 2 / 3 of the power, and inverter 1 bears about 1 / 3 of the power, achieving power allocation according to capacity ratio with a power allocation error ≤5%. At the same time, through the adaptive voltage compensation term in step S3, the circulating current between the two inverters is suppressed to within the rated current. Within; through parameter quantization and adaptive adjustment of the voltage and current dual-loop control in step S4, the voltage tracking error is suppressed to within Within this range, the output voltage waveform maintains a highly sinusoidal characteristic even under nonlinear load conditions. .

[0055] The system's physical interconnections not only ensure the accuracy of power acquisition but also guarantee the real-time execution of control commands. The core signal processing unit connects to an external monitoring terminal via a high-speed bus, uploading operating parameters in real time, including instantaneous power, average power, RMS parallel circulating current, total harmonic distortion (THD), and a predetermined radiator surface temperature. Through this highly integrated algorithm and hardware layout, this embodiment effectively solves the problems of power feedback delay, limited power allocation accuracy for different capacity units, excessive parallel circulating current, and high THD under nonlinear loads.

[0056] To enable those skilled in the art to fully understand and implement this invention, the specific implementation principles of this invention are further supplemented below with a specific application scenario.

[0057] In scenarios where distributed energy storage inverters operate in parallel, when it is necessary to quickly compensate for the power deficit on the parallel bus and maintain voltage stability, the specific operating principle is as follows: Step 1: Signal Construction and Harmonic Suppression Operating Principle: First, the output power acquisition module captures minute fluctuations at the AC output terminal through a Hall sensor; the core signal processing unit utilizes the bandpass filtering characteristics of a second-order generalized integrator to automatically filter out high-order harmonic interference in the sampled signal while constructing orthogonal signals; this physical-level frequency selection mechanism ensures that the input source for subsequent power calculation has an extremely high signal-to-noise ratio, avoiding power calculation deviations caused by grid harmonics.

[0058] Step 2, Instantaneous Power Algebraic Cancellation Principle: During power calculation, the system utilizes the algebraic operation model from step S2 to cross-multiply mutually orthogonal voltage and current components, completing the instantaneous power calculation in the orthogonal coordinate system. This calculation process cannot eliminate the inherent second harmonic ripple component of a single-phase system; the second harmonic ripple needs to be filtered out by a subsequent low-pass filter. The average power value obtained after filtering provides an accurate reference for droop control. Because... shaft and The axis signal is strictly maintained in phase. The difference, the instantaneous power it calculates does not contain the inherent harmonic components of a single-phase system; this physical calculation logic eliminates the dependence on deep low-pass filters, thereby eliminating phase lag at the signal processing level, and the average power value obtained after processing by a small bandwidth low-pass filter provides an accurate reference for droop control.

[0059] Step 3: Capacity Weighting and Dynamic Compensation Operating Principle: During the power allocation phase, the processor automatically loads a droop coefficient inversely proportional to the rated capacity based on the built-in capacity index table. Larger capacity inverters are allocated smaller droop coefficients to ensure they handle more active power at the same frequency offset. When the parallel bus voltage drops due to heavy load, the adaptive coefficient compensation step is activated, using amplitude commands... The compensation component is superimposed based on line impedance voltage drop and circulating current feedback. This mechanism forcibly corrects the vertical offset of the droop curve. This feedback-based dynamic correction mechanism enables inverters with different impedance branches to share reactive loads according to capacity ratio, suppressing parallel circulating current to within 5% of the rated current and inhibiting inter-unit circulating current. To overcome communication delay and cross-device data dependence issues, the circulating current calculation method that requires obtaining the average current of multiple machines is abandoned, and reactive power deviation that relies solely on local sampling is used to replace circulating current feedback. The adaptive voltage compensation term is calculated using only local output current, line impedance, power factor angle, and local reactive power deviation, requiring no communication and with no delay. It is suitable for parallel scenarios without communication, such as traction substations, and can also effectively compensate for line impedance voltage drop, suppress parallel circulating current, and improve reactive power distribution accuracy.

[0060] Step 4: Dual-Loop Collaborative and Synchronous Grid-Connected Operation Principle: During the control execution phase, the parameter quantization quasi-proportional resonant controller of the voltage outer loop and the quantization proportional controller of the current inner loop work together to extend the system's control bandwidth to a preset high-frequency range. The quasi-proportional resonant controller provides high gain at the fundamental frequency to ensure voltage tracking accuracy, and the resonant gain is adaptively adjusted according to the total harmonic distortion rate to ensure stability under nonlinear loads. During the inverter startup phase, the bus phase is captured by a software phase-locked loop. When the phase difference between the output voltage and the bus is less than a preset angle threshold, the closing action is executed. This realizes a physical closed loop from instantaneous power extraction and droop mapping to closed-loop drive. Through the precise control of the main power circuit by the algorithm, the dynamic response speed, power distribution accuracy and harmonic suppression capability of the parallel system are greatly improved.

[0061] To enable those skilled in the art to fully understand and implement this invention, the specific implementation principle of this invention is further supplemented below in conjunction with specific application scenarios of multi-machine parallel operation and dynamic load switching.

[0062] Step 1: Signal Feature Extraction and High-Precision Preprocessing Principle: During the initial operation phase of multiple single-phase inverters connected in parallel to the AC bus, the output power acquisition module at the output end of each inverter begins operation. It captures the instantaneous changes in bus voltage and branch current through Hall voltage and Hall current sensors; simultaneously, it acquires the effective value of the circulating current and the power factor angle. After receiving the digitized sampling sequence, the core signal processing unit calls the second-order generalized integrator logic encapsulated in its internal signal processing area. Because the second-order generalized integrator operates at a preset resonant angular frequency... It exhibits extremely high selectivity, its physical essence being equivalent to a bandpass filter with an adjustable center frequency, capable of automatically filtering out high-order harmonic components generated by nonlinear loads; in this process, the system utilizes and The phase difference characteristics, without using a traditional all-pass filter or delay stage, can be directly applied in... Shaft construction produces hysteresis axis The orthogonal signals; this physical mechanism of constructing orthogonal vectors based on integrator state variables ensures the real-time performance of the signals from the source, laying a phase-lag-free data foundation for subsequent fast power distribution.

[0063] Step 2: Instantaneous Power Algebraic Cancellation and Ripple Suppression Principle: After obtaining the quadrature voltage components... Orthogonal current components Subsequently, the core signal processing unit enters the instantaneous power calculation stage of the power control area. According to the power theory of single-phase circuits, the instantaneous power of a single phase typically contains a pulsating component twice the fundamental frequency. Traditional techniques require smoothing this component using a filter with a low cutoff frequency, which introduces significant control delay. This invention, through execution... Algebraic operations, utilizing the orthogonality of trigonometric functions, enable the frequency harmonics in the voltage and current components to physically cancel each other out during addition. This algebraic cancellation principle allows for the calculation of instantaneous active power... With reactive power Theoretically, it only includes DC components and load disturbances, thus allowing the system to use a low-pass filter with a higher cutoff frequency for micro-smoothing. The implementation of this step reduces the time constant of the power feedback loop to the millisecond level, ensuring that the system can instantly sense the power deficit when the nonlinear load suddenly increases or decreases, and the filtered average power provides accurate input for droop control.

[0064] Step 3: Capacity-weighted mapping and adaptive voltage support principle: When a nonlinear load in a parallel system undergoes a step change, each inverter unit must share the power according to its rated capacity ratio; the core signal processing unit assigns a droop coefficient inversely proportional to the rated capacity to the droop control law based on the preset capacity level. and For larger capacity inverter units, the droop factor is set to a smaller value, enabling the unit to output more active power for the same frequency offset. Simultaneously, to overcome reactive power distribution deviations caused by inconsistent line impedance between the inverter power main circuit and the AC bus, the system monitors the voltage drop at the output of the LC power filter, the inverter output current, and the parallel circulating current in real time. This is achieved through amplitude commands... The generation logic incorporates an adaptive voltage compensation term based on line impedance voltage drop and circulating current feedback. The adaptive compensation mechanism dynamically corrects the intercept of the droop curve, physically altering the inverter's output impedance characteristics and forcing reactive power flow between units to tend towards balance. This effectively suppresses internal circulating current during multi-unit parallel operation, keeping the effective value of the circulating current within 5% of the rated current, thus achieving power distribution according to capacity ratio and minimizing distribution errors. .

[0065] Step 4, Dual-Loop Dynamic Response and High-Frequency Modulation Driving Principle: This involves generating the final frequency command. With amplitude command Subsequently, the signal modulation region of the core signal processing unit initiates the quasi-proportional resonant control algorithm designed by parameter quantization; the outer voltage loop provides infinite gain for the fundamental frequency signal to ensure that the output voltage waveform can accurately track the command value, and the resonant gain... The total harmonic distortion (THD) of the output voltage is adaptively adjusted, increasing under nonlinear loads. ,make The generated inner loop current reference value is compared with the current feedback from the filter inductor in the LC power filter. The inductor current is quickly limited and tracked by a quantitatively designed proportional regulator. The resulting modulation signal is input to the pulse width modulation module to generate a high-frequency drive pulse. This pulse is amplified by the drive isolation module and drives the power switch in the main circuit of the inverter to switch at high frequency. Through the coordinated filtering of the filter inductor and filter capacitor in the LC power filter, the high-frequency switching signal is restored to pure sine wave energy. This physical closed loop from instantaneous signal extraction to high-frequency switching action ensures that the parallel system can still maintain extremely high voltage stability, power distribution accuracy and low harmonic characteristics under complex load fluctuations.

[0066] All contents not described in detail in the specification are existing technologies known to those skilled in the art, and the model parameters of each electrical appliance are not specifically limited; conventional equipment can be used. Electrical control components not mentioned in this technical solution are not shown in the figures because they are existing technologies, and will not be described here.

[0067] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A power distribution method for a single-phase inverter based on SOGI and droop control, characterized in that, Includes the following steps: S1. Real-time acquisition of output power and construction of orthogonal signals; S101. The output voltage sampling sequence and output current sampling sequence are obtained in real time by using voltage transformers and current transformers installed at the output of the single-phase inverter. S102. Input the voltage sampling sequence and the current sampling sequence into a preset second-order generalized integrator orthogonal signal generator; S103. The fundamental component is extracted using the frequency selection characteristics of the second-order generalized integrator, and virtual voltage and current components that are orthogonal in phase are constructed to form a multidimensional orthogonal signal set. S2. Instantaneous power calculation based on orthogonal components; S201. Extract the in-phase and quadrature components from the multidimensional orthogonal signal set; S202. Substitute the in-phase component and the quadrature component into the preset instantaneous power calculation model; S203. Instantaneous active power and instantaneous reactive power are obtained through algebraic operations. This orthogonal component power calculation model only completes the power calculation of single-phase electricity in the orthogonal coordinate system and cannot directly eliminate the inherent second harmonic pulsation component of the single-phase system. S204. Input the instantaneous active power and instantaneous reactive power into a preset low-pass filter to filter out the second harmonic ripple component and obtain the average power. and ; S3. Droop Characteristic Mapping and Frequency Voltage Command Generation: Based on the inverter's rated capacity level, the active frequency droop coefficient and reactive voltage droop coefficient are dynamically adjusted. The average power is substituted into the droop control equation introduced into the adaptive voltage compensation term to generate the frequency command and amplitude command of the output voltage. S4, Closed-loop modulation and drive pulse generation; S401. Use the generated frequency command and amplitude command as reference inputs; S402. Construct a voltage and current dual-loop control structure by combining the output voltage feedback value; The voltage outer loop uses a quasi-proportional resonant controller and the transfer function is quantitatively designed, while the current inner loop uses a proportional controller and the parameter tuning range is clearly defined. S403: The controller generates a modulated wave signal and generates a drive command for the power switch tube via the pulse width modulation module. S404. Adjust the switching status of the inverter bridge.

2. The power distribution method for a single-phase inverter based on SOGI and droop control according to claim 1, characterized in that, The transfer function of the second-order generalized integrator described in step S1 and They are respectively: ； ； in, The preset damping gain coefficient, This is the system's reference angular frequency.

3. The single-phase inverter power distribution method based on SOGI and droop control according to claim 1, characterized in that, The calculation formula for the instantaneous power calculation model described in step S2 is as follows: ； in, and These are the in-phase components of the fundamental voltage and current, respectively. and These are the generated orthogonal components; Instantaneous active power This refers to instantaneous reactive power.

4. The single-phase inverter power distribution method based on SOGI and droop control according to claim 1, characterized in that, The calculation formulas for dynamically adjusting the active frequency droop coefficient m and reactive voltage droop coefficient n based on the inverter's rated capacity level in step S3 are as follows: ； ； in, For the first Active and reactive droop coefficients of the inverter; This represents the maximum allowable frequency deviation of the system. This represents the maximum allowable voltage amplitude deviation of the system. and For the first Rated active and reactive power capacities of the inverter; This represents the total number of inverters connected in parallel. and The reference rated active and reactive power capacity of the parallel system; the droop factor is inversely proportional to the rated capacity of the inverter, the larger the rated capacity, the smaller the droop factor; The cutoff frequency of the low-pass filter is set in a preset frequency band higher than the system base frequency.

5. The single-phase inverter power distribution method based on SOGI and droop control according to claim 1, characterized in that, The droop control equation mentioned in step S3 is: ； ； in, This is the output voltage frequency command. This is the output voltage amplitude command; For the rated frequency, This is the rated voltage amplitude; These are the reference power for active and reactive power, respectively; This is the active frequency droop factor. This is the reactive voltage droop factor; This is an adaptive voltage compensation term used to suppress circulating current, compensate for line impedance voltage drop, and improve reactive power distribution accuracy.

6. The power distribution method for a single-phase inverter based on SOGI and droop control according to claim 5, characterized in that, The adaptive voltage compensation term The calculation is based on the effective value of the inverter output current and the voltage drop across the line impedance. The calculation formula is: ； in, This represents the effective value of the inverter output current. and The equivalent resistance and reactance of the line from the inverter to the parallel bus; The inverter output power factor angle; The circulation suppression coefficient is... Take 0.1~0.5 and adjust according to the parallel scale of the system; cancel the calculation of average current and circulating current difference that depends on multi-machine communication, and use local reactive power deviation to replace circulating current feedback. There is no need to obtain the output current of other parallel units. There is no communication delay and circulating current suppression and voltage compensation can be achieved by relying solely on local sampling. The effective value of the circulating current in the parallel system is calculated from the difference in the output current of each inverter: This represents the effective value of the average output current of the parallel inverters. The sagging coefficient and These are inversely proportional to the unit rated capacity of the inverter; in step S3, the amplitude command is adjusted based on the effective value of the output current. Perform adaptive voltage drop compensation.

7. The power distribution method for a single-phase inverter based on SOGI and droop control according to claim 1, characterized in that, The controller transfer function of the voltage-current dual-loop control structure is quantitatively designed as follows: Transfer function of the voltage outer loop quasi-proportional resonant controller: ; in This is the voltage outer loop proportional gain. Select a value between 0.5 and 2.0, and adjust it according to the system bandwidth; For resonant gain, Use values ​​between 20 and 100 to improve fundamental frequency tracking accuracy; This is the cutoff frequency of the resonant controller. To improve robustness, a value of 5-20 rad / s is used. When the system's fundamental angular frequency is 50Hz, =314 rad / s; Transfer function of the current inner loop proportional controller: ; in, This is the proportional gain of the inner current loop. A value of 5-20 is chosen to balance dynamic response and stability, satisfying the requirements. , This is the equivalent series resistance of the filter inductor.

8. The single-phase inverter power distribution method based on SOGI and droop control according to claim 7, characterized in that, The resonant gain of the quasi-proportional resonant controller It is negatively correlated with the total harmonic distortion of the system. The larger the value, the smaller the fundamental voltage tracking error, and the higher the output voltage. The lower the value, the faster the system runs. Adaptively adjusts based on the degree of load nonlinearity: the higher the proportion of nonlinear load, the better. Take the larger value.

9. A single-phase inverter power distribution system based on SOGI and droop control, applied to the single-phase inverter power distribution method based on SOGI and droop control as described in any one of claims 1 to 7, characterized in that, It includes a data acquisition module, a central processing unit, a drive isolation module, and an inverter power main circuit; The data acquisition module includes a voltage sensor and a current sensor. The output of the sensor is connected to the analog-to-digital conversion interface of the central processing unit through an anti-aliasing filter circuit. It also collects the inverter output current and the parallel bus circulating current to provide data support for adaptive voltage compensation. The central processing unit is internally divided into a signal processing area, a power control area, and a signal modulation area. The signal processing area encapsulates the second-order generalized integrator algorithm logic. The power control area stores a capacity-matched droop coefficient tuning program, a droop control law with adaptive compensation, and a dual-loop control program with parameter quantization. The signal modulation area is equipped with a pulse width modulation peripheral. The input terminal of the drive isolation module is connected to the modulation output pin of the central processing unit, and the output terminal is connected to the gate of the power switch in the main circuit of the inverter power. The inverter power main circuit adopts a full-bridge topology, with an energy storage electrolytic capacitor connected in parallel on the DC side and an LC power filter connected on the AC side.

10. The single-phase inverter power distribution system based on SOGI and droop control according to claim 9, characterized in that, The central processing unit adopts a digital signal processor with a floating-point arithmetic unit, and its main frequency is set within a preset frequency range; the corner frequency of the anti-aliasing filter circuit is configured according to a preset ratio of the sampling frequency; the LC power filter includes a filter inductor and a filter capacitor; the magnetic core of the filter inductor is made of metal powder core material, and the winding is made of multi-strand enameled wire wound in parallel. The filter capacitor is a thin-film capacitor and is located at the output lead.

Images